* [PATCH kcsan 01/29] kcsan: Refactor reading of instrumented memory
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 02/29] kcsan: Remove redundant zero-initialization of globals Paul E. McKenney
` (27 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng,
Mark Rutland, Paul E . McKenney
From: Marco Elver <elver@google.com>
Factor out the switch statement reading instrumented memory into a
helper read_instrumented_memory().
No functional change.
Signed-off-by: Marco Elver <elver@google.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/kcsan/core.c | 51 +++++++++++++++------------------------------
1 file changed, 17 insertions(+), 34 deletions(-)
diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
index 4b84c8e7884b4..6bfd3040f46be 100644
--- a/kernel/kcsan/core.c
+++ b/kernel/kcsan/core.c
@@ -325,6 +325,21 @@ static void delay_access(int type)
udelay(delay);
}
+/*
+ * Reads the instrumented memory for value change detection; value change
+ * detection is currently done for accesses up to a size of 8 bytes.
+ */
+static __always_inline u64 read_instrumented_memory(const volatile void *ptr, size_t size)
+{
+ switch (size) {
+ case 1: return READ_ONCE(*(const u8 *)ptr);
+ case 2: return READ_ONCE(*(const u16 *)ptr);
+ case 4: return READ_ONCE(*(const u32 *)ptr);
+ case 8: return READ_ONCE(*(const u64 *)ptr);
+ default: return 0; /* Ignore; we do not diff the values. */
+ }
+}
+
void kcsan_save_irqtrace(struct task_struct *task)
{
#ifdef CONFIG_TRACE_IRQFLAGS
@@ -482,23 +497,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned
* Read the current value, to later check and infer a race if the data
* was modified via a non-instrumented access, e.g. from a device.
*/
- old = 0;
- switch (size) {
- case 1:
- old = READ_ONCE(*(const u8 *)ptr);
- break;
- case 2:
- old = READ_ONCE(*(const u16 *)ptr);
- break;
- case 4:
- old = READ_ONCE(*(const u32 *)ptr);
- break;
- case 8:
- old = READ_ONCE(*(const u64 *)ptr);
- break;
- default:
- break; /* ignore; we do not diff the values */
- }
+ old = read_instrumented_memory(ptr, size);
/*
* Delay this thread, to increase probability of observing a racy
@@ -511,23 +510,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned
* racy access.
*/
access_mask = ctx->access_mask;
- new = 0;
- switch (size) {
- case 1:
- new = READ_ONCE(*(const u8 *)ptr);
- break;
- case 2:
- new = READ_ONCE(*(const u16 *)ptr);
- break;
- case 4:
- new = READ_ONCE(*(const u32 *)ptr);
- break;
- case 8:
- new = READ_ONCE(*(const u64 *)ptr);
- break;
- default:
- break; /* ignore; we do not diff the values */
- }
+ new = read_instrumented_memory(ptr, size);
diff = old ^ new;
if (access_mask)
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 02/29] kcsan: Remove redundant zero-initialization of globals
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 01/29] kcsan: Refactor reading of instrumented memory Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 03/29] kcsan: Avoid checking scoped accesses from nested contexts Paul E. McKenney
` (26 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng,
Mark Rutland, Paul E . McKenney
From: Marco Elver <elver@google.com>
They are implicitly zero-initialized, remove explicit initialization.
It keeps the upcoming additions to kcsan_ctx consistent with the rest.
No functional change intended.
Signed-off-by: Marco Elver <elver@google.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
init/init_task.c | 5 -----
kernel/kcsan/core.c | 5 -----
2 files changed, 10 deletions(-)
diff --git a/init/init_task.c b/init/init_task.c
index 2d024066e27bd..73cc8f03511a3 100644
--- a/init/init_task.c
+++ b/init/init_task.c
@@ -182,11 +182,6 @@ struct task_struct init_task
#endif
#ifdef CONFIG_KCSAN
.kcsan_ctx = {
- .disable_count = 0,
- .atomic_next = 0,
- .atomic_nest_count = 0,
- .in_flat_atomic = false,
- .access_mask = 0,
.scoped_accesses = {LIST_POISON1, NULL},
},
#endif
diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
index 6bfd3040f46be..e34a1710b7bcc 100644
--- a/kernel/kcsan/core.c
+++ b/kernel/kcsan/core.c
@@ -44,11 +44,6 @@ bool kcsan_enabled;
/* Per-CPU kcsan_ctx for interrupts */
static DEFINE_PER_CPU(struct kcsan_ctx, kcsan_cpu_ctx) = {
- .disable_count = 0,
- .atomic_next = 0,
- .atomic_nest_count = 0,
- .in_flat_atomic = false,
- .access_mask = 0,
.scoped_accesses = {LIST_POISON1, NULL},
};
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 03/29] kcsan: Avoid checking scoped accesses from nested contexts
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 01/29] kcsan: Refactor reading of instrumented memory Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 02/29] kcsan: Remove redundant zero-initialization of globals Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 04/29] kcsan: Add core support for a subset of weak memory modeling Paul E. McKenney
` (25 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
Avoid checking scoped accesses from nested contexts (such as nested
interrupts or in scheduler code) which share the same kcsan_ctx.
This is to avoid detecting false positive races of accesses in the same
thread with currently scoped accesses: consider setting up a watchpoint
for a non-scoped (normal) access that also "conflicts" with a current
scoped access. In a nested interrupt (or in the scheduler), which shares
the same kcsan_ctx, we cannot check scoped accesses set up in the parent
context -- simply ignore them in this case.
With the introduction of kcsan_ctx::disable_scoped, we can also clean up
kcsan_check_scoped_accesses()'s recursion guard, and do not need to
modify the list's prev pointer.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
include/linux/kcsan.h | 1 +
kernel/kcsan/core.c | 18 +++++++++++++++---
2 files changed, 16 insertions(+), 3 deletions(-)
diff --git a/include/linux/kcsan.h b/include/linux/kcsan.h
index fc266ecb2a4db..13cef3458fedf 100644
--- a/include/linux/kcsan.h
+++ b/include/linux/kcsan.h
@@ -21,6 +21,7 @@
*/
struct kcsan_ctx {
int disable_count; /* disable counter */
+ int disable_scoped; /* disable scoped access counter */
int atomic_next; /* number of following atomic ops */
/*
diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
index e34a1710b7bcc..bd359f8ee63a7 100644
--- a/kernel/kcsan/core.c
+++ b/kernel/kcsan/core.c
@@ -204,15 +204,17 @@ check_access(const volatile void *ptr, size_t size, int type, unsigned long ip);
static noinline void kcsan_check_scoped_accesses(void)
{
struct kcsan_ctx *ctx = get_ctx();
- struct list_head *prev_save = ctx->scoped_accesses.prev;
struct kcsan_scoped_access *scoped_access;
- ctx->scoped_accesses.prev = NULL; /* Avoid recursion. */
+ if (ctx->disable_scoped)
+ return;
+
+ ctx->disable_scoped++;
list_for_each_entry(scoped_access, &ctx->scoped_accesses, list) {
check_access(scoped_access->ptr, scoped_access->size,
scoped_access->type, scoped_access->ip);
}
- ctx->scoped_accesses.prev = prev_save;
+ ctx->disable_scoped--;
}
/* Rules for generic atomic accesses. Called from fast-path. */
@@ -465,6 +467,15 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned
goto out;
}
+ /*
+ * Avoid races of scoped accesses from nested interrupts (or scheduler).
+ * Assume setting up a watchpoint for a non-scoped (normal) access that
+ * also conflicts with a current scoped access. In a nested interrupt,
+ * which shares the context, it would check a conflicting scoped access.
+ * To avoid, disable scoped access checking.
+ */
+ ctx->disable_scoped++;
+
/*
* Save and restore the IRQ state trace touched by KCSAN, since KCSAN's
* runtime is entered for every memory access, and potentially useful
@@ -578,6 +589,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned
if (!kcsan_interrupt_watcher)
local_irq_restore(irq_flags);
kcsan_restore_irqtrace(current);
+ ctx->disable_scoped--;
out:
user_access_restore(ua_flags);
}
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 04/29] kcsan: Add core support for a subset of weak memory modeling
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (2 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 03/29] kcsan: Avoid checking scoped accesses from nested contexts Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 05/29] kcsan: Add core memory barrier instrumentation functions Paul E. McKenney
` (24 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
Add support for modeling a subset of weak memory, which will enable
detection of a subset of data races due to missing memory barriers.
KCSAN's approach to detecting missing memory barriers is based on
modeling access reordering, and enabled if `CONFIG_KCSAN_WEAK_MEMORY=y`,
which depends on `CONFIG_KCSAN_STRICT=y`. The feature can be enabled or
disabled at boot and runtime via the `kcsan.weak_memory` boot parameter.
Each memory access for which a watchpoint is set up, is also selected
for simulated reordering within the scope of its function (at most 1
in-flight access).
We are limited to modeling the effects of "buffering" (delaying the
access), since the runtime cannot "prefetch" accesses (therefore no
acquire modeling). Once an access has been selected for reordering, it
is checked along every other access until the end of the function scope.
If an appropriate memory barrier is encountered, the access will no
longer be considered for reordering.
When the result of a memory operation should be ordered by a barrier,
KCSAN can then detect data races where the conflict only occurs as a
result of a missing barrier due to reordering accesses.
Suggested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
include/linux/kcsan-checks.h | 10 +-
include/linux/kcsan.h | 10 +-
include/linux/sched.h | 3 +
kernel/kcsan/core.c | 202 ++++++++++++++++++++++++++++++++---
lib/Kconfig.kcsan | 20 ++++
scripts/Makefile.kcsan | 9 +-
6 files changed, 235 insertions(+), 19 deletions(-)
diff --git a/include/linux/kcsan-checks.h b/include/linux/kcsan-checks.h
index 5f5965246877a..a1c6a89fde710 100644
--- a/include/linux/kcsan-checks.h
+++ b/include/linux/kcsan-checks.h
@@ -99,7 +99,15 @@ void kcsan_set_access_mask(unsigned long mask);
/* Scoped access information. */
struct kcsan_scoped_access {
- struct list_head list;
+ union {
+ struct list_head list; /* scoped_accesses list */
+ /*
+ * Not an entry in scoped_accesses list; stack depth from where
+ * the access was initialized.
+ */
+ int stack_depth;
+ };
+
/* Access information. */
const volatile void *ptr;
size_t size;
diff --git a/include/linux/kcsan.h b/include/linux/kcsan.h
index 13cef3458fedf..c07c71f5ba4fd 100644
--- a/include/linux/kcsan.h
+++ b/include/linux/kcsan.h
@@ -49,8 +49,16 @@ struct kcsan_ctx {
*/
unsigned long access_mask;
- /* List of scoped accesses. */
+ /* List of scoped accesses; likely to be empty. */
struct list_head scoped_accesses;
+
+#ifdef CONFIG_KCSAN_WEAK_MEMORY
+ /*
+ * Scoped access for modeling access reordering to detect missing memory
+ * barriers; only keep 1 to keep fast-path complexity manageable.
+ */
+ struct kcsan_scoped_access reorder_access;
+#endif
};
/**
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 78c351e35fec6..0cd40b0104874 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1339,6 +1339,9 @@ struct task_struct {
#ifdef CONFIG_TRACE_IRQFLAGS
struct irqtrace_events kcsan_save_irqtrace;
#endif
+#ifdef CONFIG_KCSAN_WEAK_MEMORY
+ int kcsan_stack_depth;
+#endif
#endif
#if IS_ENABLED(CONFIG_KUNIT)
diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
index bd359f8ee63a7..481f8a5240898 100644
--- a/kernel/kcsan/core.c
+++ b/kernel/kcsan/core.c
@@ -40,6 +40,13 @@ module_param_named(udelay_interrupt, kcsan_udelay_interrupt, uint, 0644);
module_param_named(skip_watch, kcsan_skip_watch, long, 0644);
module_param_named(interrupt_watcher, kcsan_interrupt_watcher, bool, 0444);
+#ifdef CONFIG_KCSAN_WEAK_MEMORY
+static bool kcsan_weak_memory = true;
+module_param_named(weak_memory, kcsan_weak_memory, bool, 0644);
+#else
+#define kcsan_weak_memory false
+#endif
+
bool kcsan_enabled;
/* Per-CPU kcsan_ctx for interrupts */
@@ -351,6 +358,67 @@ void kcsan_restore_irqtrace(struct task_struct *task)
#endif
}
+static __always_inline int get_kcsan_stack_depth(void)
+{
+#ifdef CONFIG_KCSAN_WEAK_MEMORY
+ return current->kcsan_stack_depth;
+#else
+ BUILD_BUG();
+ return 0;
+#endif
+}
+
+static __always_inline void add_kcsan_stack_depth(int val)
+{
+#ifdef CONFIG_KCSAN_WEAK_MEMORY
+ current->kcsan_stack_depth += val;
+#else
+ BUILD_BUG();
+#endif
+}
+
+static __always_inline struct kcsan_scoped_access *get_reorder_access(struct kcsan_ctx *ctx)
+{
+#ifdef CONFIG_KCSAN_WEAK_MEMORY
+ return ctx->disable_scoped ? NULL : &ctx->reorder_access;
+#else
+ return NULL;
+#endif
+}
+
+static __always_inline bool
+find_reorder_access(struct kcsan_ctx *ctx, const volatile void *ptr, size_t size,
+ int type, unsigned long ip)
+{
+ struct kcsan_scoped_access *reorder_access = get_reorder_access(ctx);
+
+ if (!reorder_access)
+ return false;
+
+ /*
+ * Note: If accesses are repeated while reorder_access is identical,
+ * never matches the new access, because !(type & KCSAN_ACCESS_SCOPED).
+ */
+ return reorder_access->ptr == ptr && reorder_access->size == size &&
+ reorder_access->type == type && reorder_access->ip == ip;
+}
+
+static inline void
+set_reorder_access(struct kcsan_ctx *ctx, const volatile void *ptr, size_t size,
+ int type, unsigned long ip)
+{
+ struct kcsan_scoped_access *reorder_access = get_reorder_access(ctx);
+
+ if (!reorder_access || !kcsan_weak_memory)
+ return;
+
+ reorder_access->ptr = ptr;
+ reorder_access->size = size;
+ reorder_access->type = type | KCSAN_ACCESS_SCOPED;
+ reorder_access->ip = ip;
+ reorder_access->stack_depth = get_kcsan_stack_depth();
+}
+
/*
* Pull everything together: check_access() below contains the performance
* critical operations; the fast-path (including check_access) functions should
@@ -389,8 +457,10 @@ static noinline void kcsan_found_watchpoint(const volatile void *ptr,
* The access_mask check relies on value-change comparison. To avoid
* reporting a race where e.g. the writer set up the watchpoint, but the
* reader has access_mask!=0, we have to ignore the found watchpoint.
+ *
+ * reorder_access is never created from an access with access_mask set.
*/
- if (ctx->access_mask)
+ if (ctx->access_mask && !find_reorder_access(ctx, ptr, size, type, ip))
return;
/*
@@ -440,11 +510,13 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned
const bool is_assert = (type & KCSAN_ACCESS_ASSERT) != 0;
atomic_long_t *watchpoint;
u64 old, new, diff;
- unsigned long access_mask;
enum kcsan_value_change value_change = KCSAN_VALUE_CHANGE_MAYBE;
+ bool interrupt_watcher = kcsan_interrupt_watcher;
unsigned long ua_flags = user_access_save();
struct kcsan_ctx *ctx = get_ctx();
+ unsigned long access_mask = ctx->access_mask;
unsigned long irq_flags = 0;
+ bool is_reorder_access;
/*
* Always reset kcsan_skip counter in slow-path to avoid underflow; see
@@ -467,6 +539,17 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned
goto out;
}
+ /*
+ * The local CPU cannot observe reordering of its own accesses, and
+ * therefore we need to take care of 2 cases to avoid false positives:
+ *
+ * 1. Races of the reordered access with interrupts. To avoid, if
+ * the current access is reorder_access, disable interrupts.
+ * 2. Avoid races of scoped accesses from nested interrupts (below).
+ */
+ is_reorder_access = find_reorder_access(ctx, ptr, size, type, ip);
+ if (is_reorder_access)
+ interrupt_watcher = false;
/*
* Avoid races of scoped accesses from nested interrupts (or scheduler).
* Assume setting up a watchpoint for a non-scoped (normal) access that
@@ -482,7 +565,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned
* information is lost if dirtied by KCSAN.
*/
kcsan_save_irqtrace(current);
- if (!kcsan_interrupt_watcher)
+ if (!interrupt_watcher)
local_irq_save(irq_flags);
watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
@@ -503,7 +586,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned
* Read the current value, to later check and infer a race if the data
* was modified via a non-instrumented access, e.g. from a device.
*/
- old = read_instrumented_memory(ptr, size);
+ old = is_reorder_access ? 0 : read_instrumented_memory(ptr, size);
/*
* Delay this thread, to increase probability of observing a racy
@@ -515,8 +598,17 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned
* Re-read value, and check if it is as expected; if not, we infer a
* racy access.
*/
- access_mask = ctx->access_mask;
- new = read_instrumented_memory(ptr, size);
+ if (!is_reorder_access) {
+ new = read_instrumented_memory(ptr, size);
+ } else {
+ /*
+ * Reordered accesses cannot be used for value change detection,
+ * because the memory location may no longer be accessible and
+ * could result in a fault.
+ */
+ new = 0;
+ access_mask = 0;
+ }
diff = old ^ new;
if (access_mask)
@@ -585,11 +677,20 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned
*/
remove_watchpoint(watchpoint);
atomic_long_dec(&kcsan_counters[KCSAN_COUNTER_USED_WATCHPOINTS]);
+
out_unlock:
- if (!kcsan_interrupt_watcher)
+ if (!interrupt_watcher)
local_irq_restore(irq_flags);
kcsan_restore_irqtrace(current);
ctx->disable_scoped--;
+
+ /*
+ * Reordered accesses cannot be used for value change detection,
+ * therefore never consider for reordering if access_mask is set.
+ * ASSERT_EXCLUSIVE are not real accesses, ignore them as well.
+ */
+ if (!access_mask && !is_assert)
+ set_reorder_access(ctx, ptr, size, type, ip);
out:
user_access_restore(ua_flags);
}
@@ -597,7 +698,6 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned
static __always_inline void
check_access(const volatile void *ptr, size_t size, int type, unsigned long ip)
{
- const bool is_write = (type & KCSAN_ACCESS_WRITE) != 0;
atomic_long_t *watchpoint;
long encoded_watchpoint;
@@ -608,12 +708,14 @@ check_access(const volatile void *ptr, size_t size, int type, unsigned long ip)
if (unlikely(size == 0))
return;
+again:
/*
* Avoid user_access_save in fast-path: find_watchpoint is safe without
* user_access_save, as the address that ptr points to is only used to
* check if a watchpoint exists; ptr is never dereferenced.
*/
- watchpoint = find_watchpoint((unsigned long)ptr, size, !is_write,
+ watchpoint = find_watchpoint((unsigned long)ptr, size,
+ !(type & KCSAN_ACCESS_WRITE),
&encoded_watchpoint);
/*
* It is safe to check kcsan_is_enabled() after find_watchpoint in the
@@ -627,9 +729,42 @@ check_access(const volatile void *ptr, size_t size, int type, unsigned long ip)
else {
struct kcsan_ctx *ctx = get_ctx(); /* Call only once in fast-path. */
- if (unlikely(should_watch(ctx, ptr, size, type)))
+ if (unlikely(should_watch(ctx, ptr, size, type))) {
kcsan_setup_watchpoint(ptr, size, type, ip);
- else if (unlikely(ctx->scoped_accesses.prev))
+ return;
+ }
+
+ if (!(type & KCSAN_ACCESS_SCOPED)) {
+ struct kcsan_scoped_access *reorder_access = get_reorder_access(ctx);
+
+ if (reorder_access) {
+ /*
+ * reorder_access check: simulates reordering of
+ * the access after subsequent operations.
+ */
+ ptr = reorder_access->ptr;
+ type = reorder_access->type;
+ ip = reorder_access->ip;
+ /*
+ * Upon a nested interrupt, this context's
+ * reorder_access can be modified (shared ctx).
+ * We know that upon return, reorder_access is
+ * always invalidated by setting size to 0 via
+ * __tsan_func_exit(). Therefore we must read
+ * and check size after the other fields.
+ */
+ barrier();
+ size = READ_ONCE(reorder_access->size);
+ if (size)
+ goto again;
+ }
+ }
+
+ /*
+ * Always checked last, right before returning from runtime;
+ * if reorder_access is valid, checked after it was checked.
+ */
+ if (unlikely(ctx->scoped_accesses.prev))
kcsan_check_scoped_accesses();
}
}
@@ -916,19 +1051,56 @@ DEFINE_TSAN_VOLATILE_READ_WRITE(8);
DEFINE_TSAN_VOLATILE_READ_WRITE(16);
/*
- * The below are not required by KCSAN, but can still be emitted by the
- * compiler.
+ * Function entry and exit are used to determine the validty of reorder_access.
+ * Reordering of the access ends at the end of the function scope where the
+ * access happened. This is done for two reasons:
+ *
+ * 1. Artificially limits the scope where missing barriers are detected.
+ * This minimizes false positives due to uninstrumented functions that
+ * contain the required barriers but were missed.
+ *
+ * 2. Simplifies generating the stack trace of the access.
*/
void __tsan_func_entry(void *call_pc);
-void __tsan_func_entry(void *call_pc)
+noinline void __tsan_func_entry(void *call_pc)
{
+ if (!IS_ENABLED(CONFIG_KCSAN_WEAK_MEMORY))
+ return;
+
+ add_kcsan_stack_depth(1);
}
EXPORT_SYMBOL(__tsan_func_entry);
+
void __tsan_func_exit(void);
-void __tsan_func_exit(void)
+noinline void __tsan_func_exit(void)
{
+ struct kcsan_scoped_access *reorder_access;
+
+ if (!IS_ENABLED(CONFIG_KCSAN_WEAK_MEMORY))
+ return;
+
+ reorder_access = get_reorder_access(get_ctx());
+ if (!reorder_access)
+ goto out;
+
+ if (get_kcsan_stack_depth() <= reorder_access->stack_depth) {
+ /*
+ * Access check to catch cases where write without a barrier
+ * (supposed release) was last access in function: because
+ * instrumentation is inserted before the real access, a data
+ * race due to the write giving up a c-s would only be caught if
+ * we do the conflicting access after.
+ */
+ check_access(reorder_access->ptr, reorder_access->size,
+ reorder_access->type, reorder_access->ip);
+ reorder_access->size = 0;
+ reorder_access->stack_depth = INT_MIN;
+ }
+out:
+ add_kcsan_stack_depth(-1);
}
EXPORT_SYMBOL(__tsan_func_exit);
+
void __tsan_init(void);
void __tsan_init(void)
{
diff --git a/lib/Kconfig.kcsan b/lib/Kconfig.kcsan
index e0a93ffdef30e..e4394ea8068b0 100644
--- a/lib/Kconfig.kcsan
+++ b/lib/Kconfig.kcsan
@@ -191,6 +191,26 @@ config KCSAN_STRICT
closely aligns with the rules defined by the Linux-kernel memory
consistency model (LKMM).
+config KCSAN_WEAK_MEMORY
+ bool "Enable weak memory modeling to detect missing memory barriers"
+ default y
+ depends on KCSAN_STRICT
+ # We can either let objtool nop __tsan_func_{entry,exit}() and builtin
+ # atomics instrumentation in .noinstr.text, or use a compiler that can
+ # implement __no_kcsan to really remove all instrumentation.
+ depends on STACK_VALIDATION || CC_IS_GCC
+ help
+ Enable support for modeling a subset of weak memory, which allows
+ detecting a subset of data races due to missing memory barriers.
+
+ Depends on KCSAN_STRICT, because the options strenghtening certain
+ plain accesses by default (depending on !KCSAN_STRICT) reduce the
+ ability to detect any data races invoving reordered accesses, in
+ particular reordered writes.
+
+ Weak memory modeling relies on additional instrumentation and may
+ affect performance.
+
config KCSAN_REPORT_VALUE_CHANGE_ONLY
bool "Only report races where watcher observed a data value change"
default y
diff --git a/scripts/Makefile.kcsan b/scripts/Makefile.kcsan
index 37cb504c77e13..4c7f0d282e42f 100644
--- a/scripts/Makefile.kcsan
+++ b/scripts/Makefile.kcsan
@@ -9,7 +9,12 @@ endif
# Keep most options here optional, to allow enabling more compilers if absence
# of some options does not break KCSAN nor causes false positive reports.
-export CFLAGS_KCSAN := -fsanitize=thread \
- $(call cc-option,$(call cc-param,tsan-instrument-func-entry-exit=0) -fno-optimize-sibling-calls) \
+kcsan-cflags := -fsanitize=thread -fno-optimize-sibling-calls \
$(call cc-option,$(call cc-param,tsan-compound-read-before-write=1),$(call cc-option,$(call cc-param,tsan-instrument-read-before-write=1))) \
$(call cc-param,tsan-distinguish-volatile=1)
+
+ifndef CONFIG_KCSAN_WEAK_MEMORY
+kcsan-cflags += $(call cc-option,$(call cc-param,tsan-instrument-func-entry-exit=0))
+endif
+
+export CFLAGS_KCSAN := $(kcsan-cflags)
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 05/29] kcsan: Add core memory barrier instrumentation functions
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (3 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 04/29] kcsan: Add core support for a subset of weak memory modeling Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 06/29] kcsan, kbuild: Add option for barrier instrumentation only Paul E. McKenney
` (23 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
Add the core memory barrier instrumentation functions. These invalidate
the current in-flight reordered access based on the rules for the
respective barrier types and in-flight access type.
To obtain barrier instrumentation that can be disabled via __no_kcsan
with appropriate compiler-support (and not just with objtool help),
barrier instrumentation repurposes __atomic_signal_fence(), instead of
inserting explicit calls. Crucially, __atomic_signal_fence() normally
does not map to any real instructions, but is still intercepted by
fsanitize=thread. As a result, like any other instrumentation done by
the compiler, barrier instrumentation can be disabled with __no_kcsan.
Unfortunately Clang and GCC currently differ in their __no_kcsan aka
__no_sanitize_thread behaviour with respect to builtin atomics (and
__tsan_func_{entry,exit}) instrumentation. This is already reflected in
Kconfig.kcsan's dependencies for KCSAN_WEAK_MEMORY. A later change will
introduce support for newer versions of Clang that can implement
__no_kcsan to also remove the additional instrumentation introduced by
KCSAN_WEAK_MEMORY.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
include/linux/kcsan-checks.h | 71 +++++++++++++++++++++++++++++++++++-
kernel/kcsan/core.c | 68 +++++++++++++++++++++++++++++++++-
2 files changed, 136 insertions(+), 3 deletions(-)
diff --git a/include/linux/kcsan-checks.h b/include/linux/kcsan-checks.h
index a1c6a89fde710..9d2c869167f2e 100644
--- a/include/linux/kcsan-checks.h
+++ b/include/linux/kcsan-checks.h
@@ -36,6 +36,36 @@
*/
void __kcsan_check_access(const volatile void *ptr, size_t size, int type);
+/*
+ * See definition of __tsan_atomic_signal_fence() in kernel/kcsan/core.c.
+ * Note: The mappings are arbitrary, and do not reflect any real mappings of C11
+ * memory orders to the LKMM memory orders and vice-versa!
+ */
+#define __KCSAN_BARRIER_TO_SIGNAL_FENCE_mb __ATOMIC_SEQ_CST
+#define __KCSAN_BARRIER_TO_SIGNAL_FENCE_wmb __ATOMIC_ACQ_REL
+#define __KCSAN_BARRIER_TO_SIGNAL_FENCE_rmb __ATOMIC_ACQUIRE
+#define __KCSAN_BARRIER_TO_SIGNAL_FENCE_release __ATOMIC_RELEASE
+
+/**
+ * __kcsan_mb - full memory barrier instrumentation
+ */
+void __kcsan_mb(void);
+
+/**
+ * __kcsan_wmb - write memory barrier instrumentation
+ */
+void __kcsan_wmb(void);
+
+/**
+ * __kcsan_rmb - read memory barrier instrumentation
+ */
+void __kcsan_rmb(void);
+
+/**
+ * __kcsan_release - release barrier instrumentation
+ */
+void __kcsan_release(void);
+
/**
* kcsan_disable_current - disable KCSAN for the current context
*
@@ -159,6 +189,10 @@ void kcsan_end_scoped_access(struct kcsan_scoped_access *sa);
static inline void __kcsan_check_access(const volatile void *ptr, size_t size,
int type) { }
+static inline void __kcsan_mb(void) { }
+static inline void __kcsan_wmb(void) { }
+static inline void __kcsan_rmb(void) { }
+static inline void __kcsan_release(void) { }
static inline void kcsan_disable_current(void) { }
static inline void kcsan_enable_current(void) { }
static inline void kcsan_enable_current_nowarn(void) { }
@@ -191,12 +225,45 @@ static inline void kcsan_end_scoped_access(struct kcsan_scoped_access *sa) { }
*/
#define __kcsan_disable_current kcsan_disable_current
#define __kcsan_enable_current kcsan_enable_current_nowarn
-#else
+#else /* __SANITIZE_THREAD__ */
static inline void kcsan_check_access(const volatile void *ptr, size_t size,
int type) { }
static inline void __kcsan_enable_current(void) { }
static inline void __kcsan_disable_current(void) { }
-#endif
+#endif /* __SANITIZE_THREAD__ */
+
+#if defined(CONFIG_KCSAN_WEAK_MEMORY) && defined(__SANITIZE_THREAD__)
+/*
+ * Normal barrier instrumentation is not done via explicit calls, but by mapping
+ * to a repurposed __atomic_signal_fence(), which normally does not generate any
+ * real instructions, but is still intercepted by fsanitize=thread. This means,
+ * like any other compile-time instrumentation, barrier instrumentation can be
+ * disabled with the __no_kcsan function attribute.
+ *
+ * Also see definition of __tsan_atomic_signal_fence() in kernel/kcsan/core.c.
+ */
+#define __KCSAN_BARRIER_TO_SIGNAL_FENCE(name) \
+ static __always_inline void kcsan_##name(void) \
+ { \
+ barrier(); \
+ __atomic_signal_fence(__KCSAN_BARRIER_TO_SIGNAL_FENCE_##name); \
+ barrier(); \
+ }
+__KCSAN_BARRIER_TO_SIGNAL_FENCE(mb)
+__KCSAN_BARRIER_TO_SIGNAL_FENCE(wmb)
+__KCSAN_BARRIER_TO_SIGNAL_FENCE(rmb)
+__KCSAN_BARRIER_TO_SIGNAL_FENCE(release)
+#elif defined(CONFIG_KCSAN_WEAK_MEMORY) && defined(__KCSAN_INSTRUMENT_BARRIERS__)
+#define kcsan_mb __kcsan_mb
+#define kcsan_wmb __kcsan_wmb
+#define kcsan_rmb __kcsan_rmb
+#define kcsan_release __kcsan_release
+#else /* CONFIG_KCSAN_WEAK_MEMORY && ... */
+static inline void kcsan_mb(void) { }
+static inline void kcsan_wmb(void) { }
+static inline void kcsan_rmb(void) { }
+static inline void kcsan_release(void) { }
+#endif /* CONFIG_KCSAN_WEAK_MEMORY && ... */
/**
* __kcsan_check_read - check regular read access for races
diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
index 481f8a5240898..9160609139666 100644
--- a/kernel/kcsan/core.c
+++ b/kernel/kcsan/core.c
@@ -939,6 +939,22 @@ void __kcsan_check_access(const volatile void *ptr, size_t size, int type)
}
EXPORT_SYMBOL(__kcsan_check_access);
+#define DEFINE_MEMORY_BARRIER(name, order_before_cond) \
+ void __kcsan_##name(void) \
+ { \
+ struct kcsan_scoped_access *sa = get_reorder_access(get_ctx()); \
+ if (!sa) \
+ return; \
+ if (order_before_cond) \
+ sa->size = 0; \
+ } \
+ EXPORT_SYMBOL(__kcsan_##name)
+
+DEFINE_MEMORY_BARRIER(mb, true);
+DEFINE_MEMORY_BARRIER(wmb, sa->type & (KCSAN_ACCESS_WRITE | KCSAN_ACCESS_COMPOUND));
+DEFINE_MEMORY_BARRIER(rmb, !(sa->type & KCSAN_ACCESS_WRITE) || (sa->type & KCSAN_ACCESS_COMPOUND));
+DEFINE_MEMORY_BARRIER(release, true);
+
/*
* KCSAN uses the same instrumentation that is emitted by supported compilers
* for ThreadSanitizer (TSAN).
@@ -1123,10 +1139,19 @@ EXPORT_SYMBOL(__tsan_init);
* functions, whose job is to also execute the operation itself.
*/
+static __always_inline void kcsan_atomic_builtin_memorder(int memorder)
+{
+ if (memorder == __ATOMIC_RELEASE ||
+ memorder == __ATOMIC_SEQ_CST ||
+ memorder == __ATOMIC_ACQ_REL)
+ __kcsan_release();
+}
+
#define DEFINE_TSAN_ATOMIC_LOAD_STORE(bits) \
u##bits __tsan_atomic##bits##_load(const u##bits *ptr, int memorder); \
u##bits __tsan_atomic##bits##_load(const u##bits *ptr, int memorder) \
{ \
+ kcsan_atomic_builtin_memorder(memorder); \
if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \
check_access(ptr, bits / BITS_PER_BYTE, KCSAN_ACCESS_ATOMIC, _RET_IP_); \
} \
@@ -1136,6 +1161,7 @@ EXPORT_SYMBOL(__tsan_init);
void __tsan_atomic##bits##_store(u##bits *ptr, u##bits v, int memorder); \
void __tsan_atomic##bits##_store(u##bits *ptr, u##bits v, int memorder) \
{ \
+ kcsan_atomic_builtin_memorder(memorder); \
if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \
check_access(ptr, bits / BITS_PER_BYTE, \
KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC, _RET_IP_); \
@@ -1148,6 +1174,7 @@ EXPORT_SYMBOL(__tsan_init);
u##bits __tsan_atomic##bits##_##op(u##bits *ptr, u##bits v, int memorder); \
u##bits __tsan_atomic##bits##_##op(u##bits *ptr, u##bits v, int memorder) \
{ \
+ kcsan_atomic_builtin_memorder(memorder); \
if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \
check_access(ptr, bits / BITS_PER_BYTE, \
KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | \
@@ -1180,6 +1207,7 @@ EXPORT_SYMBOL(__tsan_init);
int __tsan_atomic##bits##_compare_exchange_##strength(u##bits *ptr, u##bits *exp, \
u##bits val, int mo, int fail_mo) \
{ \
+ kcsan_atomic_builtin_memorder(mo); \
if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \
check_access(ptr, bits / BITS_PER_BYTE, \
KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | \
@@ -1195,6 +1223,7 @@ EXPORT_SYMBOL(__tsan_init);
u##bits __tsan_atomic##bits##_compare_exchange_val(u##bits *ptr, u##bits exp, u##bits val, \
int mo, int fail_mo) \
{ \
+ kcsan_atomic_builtin_memorder(mo); \
if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \
check_access(ptr, bits / BITS_PER_BYTE, \
KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | \
@@ -1226,10 +1255,47 @@ DEFINE_TSAN_ATOMIC_OPS(64);
void __tsan_atomic_thread_fence(int memorder);
void __tsan_atomic_thread_fence(int memorder)
{
+ kcsan_atomic_builtin_memorder(memorder);
__atomic_thread_fence(memorder);
}
EXPORT_SYMBOL(__tsan_atomic_thread_fence);
+/*
+ * In instrumented files, we emit instrumentation for barriers by mapping the
+ * kernel barriers to an __atomic_signal_fence(), which is interpreted specially
+ * and otherwise has no relation to a real __atomic_signal_fence(). No known
+ * kernel code uses __atomic_signal_fence().
+ *
+ * Since fsanitize=thread instrumentation handles __atomic_signal_fence(), which
+ * are turned into calls to __tsan_atomic_signal_fence(), such instrumentation
+ * can be disabled via the __no_kcsan function attribute (vs. an explicit call
+ * which could not). When __no_kcsan is requested, __atomic_signal_fence()
+ * generates no code.
+ *
+ * Note: The result of using __atomic_signal_fence() with KCSAN enabled is
+ * potentially limiting the compiler's ability to reorder operations; however,
+ * if barriers were instrumented with explicit calls (without LTO), the compiler
+ * couldn't optimize much anyway. The result of a hypothetical architecture
+ * using __atomic_signal_fence() in normal code would be KCSAN false negatives.
+ */
void __tsan_atomic_signal_fence(int memorder);
-void __tsan_atomic_signal_fence(int memorder) { }
+noinline void __tsan_atomic_signal_fence(int memorder)
+{
+ switch (memorder) {
+ case __KCSAN_BARRIER_TO_SIGNAL_FENCE_mb:
+ __kcsan_mb();
+ break;
+ case __KCSAN_BARRIER_TO_SIGNAL_FENCE_wmb:
+ __kcsan_wmb();
+ break;
+ case __KCSAN_BARRIER_TO_SIGNAL_FENCE_rmb:
+ __kcsan_rmb();
+ break;
+ case __KCSAN_BARRIER_TO_SIGNAL_FENCE_release:
+ __kcsan_release();
+ break;
+ default:
+ break;
+ }
+}
EXPORT_SYMBOL(__tsan_atomic_signal_fence);
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 06/29] kcsan, kbuild: Add option for barrier instrumentation only
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (4 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 05/29] kcsan: Add core memory barrier instrumentation functions Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 07/29] kcsan: Call scoped accesses reordered in reports Paul E. McKenney
` (22 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
Source files that disable KCSAN via KCSAN_SANITIZE := n, remove all
instrumentation, including explicit barrier instrumentation. With
instrumentation for memory barriers, in few places it is required to
enable just the explicit instrumentation for memory barriers to avoid
false positives.
Providing the Makefile variable KCSAN_INSTRUMENT_BARRIERS_obj.o or
KCSAN_INSTRUMENT_BARRIERS (for all files) set to 'y' only enables the
explicit barrier instrumentation.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
scripts/Makefile.lib | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index d1f865b8c0cba..ab17f7b2e33c4 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -182,6 +182,11 @@ ifeq ($(CONFIG_KCSAN),y)
_c_flags += $(if $(patsubst n%,, \
$(KCSAN_SANITIZE_$(basetarget).o)$(KCSAN_SANITIZE)y), \
$(CFLAGS_KCSAN))
+# Some uninstrumented files provide implied barriers required to avoid false
+# positives: set KCSAN_INSTRUMENT_BARRIERS for barrier instrumentation only.
+_c_flags += $(if $(patsubst n%,, \
+ $(KCSAN_INSTRUMENT_BARRIERS_$(basetarget).o)$(KCSAN_INSTRUMENT_BARRIERS)n), \
+ -D__KCSAN_INSTRUMENT_BARRIERS__)
endif
# $(srctree)/$(src) for including checkin headers from generated source files
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 07/29] kcsan: Call scoped accesses reordered in reports
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (5 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 06/29] kcsan, kbuild: Add option for barrier instrumentation only Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 08/29] kcsan: Show location access was reordered to Paul E. McKenney
` (21 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
The scoping of an access simply denotes the scope in which it may be
reordered. However, in reports, it'll be less confusing to say the
access is "reordered". This is more accurate when the race occurred.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/kcsan/kcsan_test.c | 4 ++--
kernel/kcsan/report.c | 16 ++++++++--------
2 files changed, 10 insertions(+), 10 deletions(-)
diff --git a/kernel/kcsan/kcsan_test.c b/kernel/kcsan/kcsan_test.c
index 6607292385880..6e3c2b8bc6083 100644
--- a/kernel/kcsan/kcsan_test.c
+++ b/kernel/kcsan/kcsan_test.c
@@ -213,9 +213,9 @@ static bool report_matches(const struct expect_report *r)
const bool is_atomic = (ty & KCSAN_ACCESS_ATOMIC);
const bool is_scoped = (ty & KCSAN_ACCESS_SCOPED);
const char *const access_type_aux =
- (is_atomic && is_scoped) ? " (marked, scoped)"
+ (is_atomic && is_scoped) ? " (marked, reordered)"
: (is_atomic ? " (marked)"
- : (is_scoped ? " (scoped)" : ""));
+ : (is_scoped ? " (reordered)" : ""));
if (i == 1) {
/* Access 2 */
diff --git a/kernel/kcsan/report.c b/kernel/kcsan/report.c
index fc15077991c47..1b0e050bdf6a0 100644
--- a/kernel/kcsan/report.c
+++ b/kernel/kcsan/report.c
@@ -215,9 +215,9 @@ static const char *get_access_type(int type)
if (type & KCSAN_ACCESS_ASSERT) {
if (type & KCSAN_ACCESS_SCOPED) {
if (type & KCSAN_ACCESS_WRITE)
- return "assert no accesses (scoped)";
+ return "assert no accesses (reordered)";
else
- return "assert no writes (scoped)";
+ return "assert no writes (reordered)";
} else {
if (type & KCSAN_ACCESS_WRITE)
return "assert no accesses";
@@ -240,17 +240,17 @@ static const char *get_access_type(int type)
case KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC:
return "read-write (marked)";
case KCSAN_ACCESS_SCOPED:
- return "read (scoped)";
+ return "read (reordered)";
case KCSAN_ACCESS_SCOPED | KCSAN_ACCESS_ATOMIC:
- return "read (marked, scoped)";
+ return "read (marked, reordered)";
case KCSAN_ACCESS_SCOPED | KCSAN_ACCESS_WRITE:
- return "write (scoped)";
+ return "write (reordered)";
case KCSAN_ACCESS_SCOPED | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC:
- return "write (marked, scoped)";
+ return "write (marked, reordered)";
case KCSAN_ACCESS_SCOPED | KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE:
- return "read-write (scoped)";
+ return "read-write (reordered)";
case KCSAN_ACCESS_SCOPED | KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC:
- return "read-write (marked, scoped)";
+ return "read-write (marked, reordered)";
default:
BUG();
}
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 08/29] kcsan: Show location access was reordered to
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (6 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 07/29] kcsan: Call scoped accesses reordered in reports Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 09/29] kcsan: Document modeling of weak memory Paul E. McKenney
` (20 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
Also show the location the access was reordered to. An example report:
| ==================================================================
| BUG: KCSAN: data-race in test_kernel_wrong_memorder / test_kernel_wrong_memorder
|
| read-write to 0xffffffffc01e61a8 of 8 bytes by task 2311 on cpu 5:
| test_kernel_wrong_memorder+0x57/0x90
| access_thread+0x99/0xe0
| kthread+0x2ba/0x2f0
| ret_from_fork+0x22/0x30
|
| read-write (reordered) to 0xffffffffc01e61a8 of 8 bytes by task 2310 on cpu 7:
| test_kernel_wrong_memorder+0x57/0x90
| access_thread+0x99/0xe0
| kthread+0x2ba/0x2f0
| ret_from_fork+0x22/0x30
| |
| +-> reordered to: test_kernel_wrong_memorder+0x80/0x90
|
| Reported by Kernel Concurrency Sanitizer on:
| CPU: 7 PID: 2310 Comm: access_thread Not tainted 5.14.0-rc1+ #18
| Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
| ==================================================================
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/kcsan/report.c | 35 +++++++++++++++++++++++------------
1 file changed, 23 insertions(+), 12 deletions(-)
diff --git a/kernel/kcsan/report.c b/kernel/kcsan/report.c
index 1b0e050bdf6a0..67794404042a5 100644
--- a/kernel/kcsan/report.c
+++ b/kernel/kcsan/report.c
@@ -308,10 +308,12 @@ static int get_stack_skipnr(const unsigned long stack_entries[], int num_entries
/*
* Skips to the first entry that matches the function of @ip, and then replaces
- * that entry with @ip, returning the entries to skip.
+ * that entry with @ip, returning the entries to skip with @replaced containing
+ * the replaced entry.
*/
static int
-replace_stack_entry(unsigned long stack_entries[], int num_entries, unsigned long ip)
+replace_stack_entry(unsigned long stack_entries[], int num_entries, unsigned long ip,
+ unsigned long *replaced)
{
unsigned long symbolsize, offset;
unsigned long target_func;
@@ -330,6 +332,7 @@ replace_stack_entry(unsigned long stack_entries[], int num_entries, unsigned lon
func -= offset;
if (func == target_func) {
+ *replaced = stack_entries[skip];
stack_entries[skip] = ip;
return skip;
}
@@ -342,9 +345,10 @@ replace_stack_entry(unsigned long stack_entries[], int num_entries, unsigned lon
}
static int
-sanitize_stack_entries(unsigned long stack_entries[], int num_entries, unsigned long ip)
+sanitize_stack_entries(unsigned long stack_entries[], int num_entries, unsigned long ip,
+ unsigned long *replaced)
{
- return ip ? replace_stack_entry(stack_entries, num_entries, ip) :
+ return ip ? replace_stack_entry(stack_entries, num_entries, ip, replaced) :
get_stack_skipnr(stack_entries, num_entries);
}
@@ -360,6 +364,14 @@ static int sym_strcmp(void *addr1, void *addr2)
return strncmp(buf1, buf2, sizeof(buf1));
}
+static void
+print_stack_trace(unsigned long stack_entries[], int num_entries, unsigned long reordered_to)
+{
+ stack_trace_print(stack_entries, num_entries, 0);
+ if (reordered_to)
+ pr_err(" |\n +-> reordered to: %pS\n", (void *)reordered_to);
+}
+
static void print_verbose_info(struct task_struct *task)
{
if (!task)
@@ -378,10 +390,12 @@ static void print_report(enum kcsan_value_change value_change,
struct other_info *other_info,
u64 old, u64 new, u64 mask)
{
+ unsigned long reordered_to = 0;
unsigned long stack_entries[NUM_STACK_ENTRIES] = { 0 };
int num_stack_entries = stack_trace_save(stack_entries, NUM_STACK_ENTRIES, 1);
- int skipnr = sanitize_stack_entries(stack_entries, num_stack_entries, ai->ip);
+ int skipnr = sanitize_stack_entries(stack_entries, num_stack_entries, ai->ip, &reordered_to);
unsigned long this_frame = stack_entries[skipnr];
+ unsigned long other_reordered_to = 0;
unsigned long other_frame = 0;
int other_skipnr = 0; /* silence uninit warnings */
@@ -394,7 +408,7 @@ static void print_report(enum kcsan_value_change value_change,
if (other_info) {
other_skipnr = sanitize_stack_entries(other_info->stack_entries,
other_info->num_stack_entries,
- other_info->ai.ip);
+ other_info->ai.ip, &other_reordered_to);
other_frame = other_info->stack_entries[other_skipnr];
/* @value_change is only known for the other thread */
@@ -434,10 +448,9 @@ static void print_report(enum kcsan_value_change value_change,
other_info->ai.cpu_id);
/* Print the other thread's stack trace. */
- stack_trace_print(other_info->stack_entries + other_skipnr,
+ print_stack_trace(other_info->stack_entries + other_skipnr,
other_info->num_stack_entries - other_skipnr,
- 0);
-
+ other_reordered_to);
if (IS_ENABLED(CONFIG_KCSAN_VERBOSE))
print_verbose_info(other_info->task);
@@ -451,9 +464,7 @@ static void print_report(enum kcsan_value_change value_change,
get_thread_desc(ai->task_pid), ai->cpu_id);
}
/* Print stack trace of this thread. */
- stack_trace_print(stack_entries + skipnr, num_stack_entries - skipnr,
- 0);
-
+ print_stack_trace(stack_entries + skipnr, num_stack_entries - skipnr, reordered_to);
if (IS_ENABLED(CONFIG_KCSAN_VERBOSE))
print_verbose_info(current);
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 09/29] kcsan: Document modeling of weak memory
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (7 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 08/29] kcsan: Show location access was reordered to Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 10/29] kcsan: test: Match reordered or normal accesses Paul E. McKenney
` (19 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
Document how KCSAN models a subset of weak memory and the subset of
missing memory barriers it can detect as a result.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
Documentation/dev-tools/kcsan.rst | 76 +++++++++++++++++++++++++------
1 file changed, 63 insertions(+), 13 deletions(-)
diff --git a/Documentation/dev-tools/kcsan.rst b/Documentation/dev-tools/kcsan.rst
index 7db43c7c09b8c..3ae866dcc9240 100644
--- a/Documentation/dev-tools/kcsan.rst
+++ b/Documentation/dev-tools/kcsan.rst
@@ -204,17 +204,17 @@ Ultimately this allows to determine the possible executions of concurrent code,
and if that code is free from data races.
KCSAN is aware of *marked atomic operations* (``READ_ONCE``, ``WRITE_ONCE``,
-``atomic_*``, etc.), but is oblivious of any ordering guarantees and simply
-assumes that memory barriers are placed correctly. In other words, KCSAN
-assumes that as long as a plain access is not observed to race with another
-conflicting access, memory operations are correctly ordered.
-
-This means that KCSAN will not report *potential* data races due to missing
-memory ordering. Developers should therefore carefully consider the required
-memory ordering requirements that remain unchecked. If, however, missing
-memory ordering (that is observable with a particular compiler and
-architecture) leads to an observable data race (e.g. entering a critical
-section erroneously), KCSAN would report the resulting data race.
+``atomic_*``, etc.), and a subset of ordering guarantees implied by memory
+barriers. With ``CONFIG_KCSAN_WEAK_MEMORY=y``, KCSAN models load or store
+buffering, and can detect missing ``smp_mb()``, ``smp_wmb()``, ``smp_rmb()``,
+``smp_store_release()``, and all ``atomic_*`` operations with equivalent
+implied barriers.
+
+Note, KCSAN will not report all data races due to missing memory ordering,
+specifically where a memory barrier would be required to prohibit subsequent
+memory operation from reordering before the barrier. Developers should
+therefore carefully consider the required memory ordering requirements that
+remain unchecked.
Race Detection Beyond Data Races
--------------------------------
@@ -268,6 +268,56 @@ marked operations, if all accesses to a variable that is accessed concurrently
are properly marked, KCSAN will never trigger a watchpoint and therefore never
report the accesses.
+Modeling Weak Memory
+~~~~~~~~~~~~~~~~~~~~
+
+KCSAN's approach to detecting data races due to missing memory barriers is
+based on modeling access reordering (with ``CONFIG_KCSAN_WEAK_MEMORY=y``).
+Each plain memory access for which a watchpoint is set up, is also selected for
+simulated reordering within the scope of its function (at most 1 in-flight
+access).
+
+Once an access has been selected for reordering, it is checked along every
+other access until the end of the function scope. If an appropriate memory
+barrier is encountered, the access will no longer be considered for simulated
+reordering.
+
+When the result of a memory operation should be ordered by a barrier, KCSAN can
+then detect data races where the conflict only occurs as a result of a missing
+barrier. Consider the example::
+
+ int x, flag;
+ void T1(void)
+ {
+ x = 1; // data race!
+ WRITE_ONCE(flag, 1); // correct: smp_store_release(&flag, 1)
+ }
+ void T2(void)
+ {
+ while (!READ_ONCE(flag)); // correct: smp_load_acquire(&flag)
+ ... = x; // data race!
+ }
+
+When weak memory modeling is enabled, KCSAN can consider ``x`` in ``T1`` for
+simulated reordering. After the write of ``flag``, ``x`` is again checked for
+concurrent accesses: because ``T2`` is able to proceed after the write of
+``flag``, a data race is detected. With the correct barriers in place, ``x``
+would not be considered for reordering after the proper release of ``flag``,
+and no data race would be detected.
+
+Deliberate trade-offs in complexity but also practical limitations mean only a
+subset of data races due to missing memory barriers can be detected. With
+currently available compiler support, the implementation is limited to modeling
+the effects of "buffering" (delaying accesses), since the runtime cannot
+"prefetch" accesses. Also recall that watchpoints are only set up for plain
+accesses, and the only access type for which KCSAN simulates reordering. This
+means reordering of marked accesses is not modeled.
+
+A consequence of the above is that acquire operations do not require barrier
+instrumentation (no prefetching). Furthermore, marked accesses introducing
+address or control dependencies do not require special handling (the marked
+access cannot be reordered, later dependent accesses cannot be prefetched).
+
Key Properties
~~~~~~~~~~~~~~
@@ -290,8 +340,8 @@ Key Properties
4. **Detects Racy Writes from Devices:** Due to checking data values upon
setting up watchpoints, racy writes from devices can also be detected.
-5. **Memory Ordering:** KCSAN is *not* explicitly aware of the LKMM's ordering
- rules; this may result in missed data races (false negatives).
+5. **Memory Ordering:** KCSAN is aware of only a subset of LKMM ordering rules;
+ this may result in missed data races (false negatives).
6. **Analysis Accuracy:** For observed executions, due to using a sampling
strategy, the analysis is *unsound* (false negatives possible), but aims to
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 10/29] kcsan: test: Match reordered or normal accesses
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (8 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 09/29] kcsan: Document modeling of weak memory Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 11/29] kcsan: test: Add test cases for memory barrier instrumentation Paul E. McKenney
` (18 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
Due to reordering accesses with weak memory modeling, any access can now
appear as "(reordered)".
Match any permutation of accesses if CONFIG_KCSAN_WEAK_MEMORY=y, so that
we effectively match an access if it is denoted "(reordered)" or not.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/kcsan/kcsan_test.c | 92 +++++++++++++++++++++++++++------------
1 file changed, 63 insertions(+), 29 deletions(-)
diff --git a/kernel/kcsan/kcsan_test.c b/kernel/kcsan/kcsan_test.c
index 6e3c2b8bc6083..ec054879201b3 100644
--- a/kernel/kcsan/kcsan_test.c
+++ b/kernel/kcsan/kcsan_test.c
@@ -151,7 +151,7 @@ struct expect_report {
/* Check observed report matches information in @r. */
__no_kcsan
-static bool report_matches(const struct expect_report *r)
+static bool __report_matches(const struct expect_report *r)
{
const bool is_assert = (r->access[0].type | r->access[1].type) & KCSAN_ACCESS_ASSERT;
bool ret = false;
@@ -253,6 +253,40 @@ static bool report_matches(const struct expect_report *r)
return ret;
}
+static __always_inline const struct expect_report *
+__report_set_scoped(struct expect_report *r, int accesses)
+{
+ BUILD_BUG_ON(accesses > 3);
+
+ if (accesses & 1)
+ r->access[0].type |= KCSAN_ACCESS_SCOPED;
+ else
+ r->access[0].type &= ~KCSAN_ACCESS_SCOPED;
+
+ if (accesses & 2)
+ r->access[1].type |= KCSAN_ACCESS_SCOPED;
+ else
+ r->access[1].type &= ~KCSAN_ACCESS_SCOPED;
+
+ return r;
+}
+
+__no_kcsan
+static bool report_matches_any_reordered(struct expect_report *r)
+{
+ return __report_matches(__report_set_scoped(r, 0)) ||
+ __report_matches(__report_set_scoped(r, 1)) ||
+ __report_matches(__report_set_scoped(r, 2)) ||
+ __report_matches(__report_set_scoped(r, 3));
+}
+
+#ifdef CONFIG_KCSAN_WEAK_MEMORY
+/* Due to reordering accesses, any access may appear as "(reordered)". */
+#define report_matches report_matches_any_reordered
+#else
+#define report_matches __report_matches
+#endif
+
/* ===== Test kernels ===== */
static long test_sink;
@@ -438,13 +472,13 @@ static noinline void test_kernel_xor_1bit(void)
__no_kcsan
static void test_basic(struct kunit *test)
{
- const struct expect_report expect = {
+ struct expect_report expect = {
.access = {
{ test_kernel_write, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
},
};
- static const struct expect_report never = {
+ struct expect_report never = {
.access = {
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
@@ -469,14 +503,14 @@ static void test_basic(struct kunit *test)
__no_kcsan
static void test_concurrent_races(struct kunit *test)
{
- const struct expect_report expect = {
+ struct expect_report expect = {
.access = {
/* NULL will match any address. */
{ test_kernel_rmw_array, NULL, 0, __KCSAN_ACCESS_RW(KCSAN_ACCESS_WRITE) },
{ test_kernel_rmw_array, NULL, 0, __KCSAN_ACCESS_RW(0) },
},
};
- static const struct expect_report never = {
+ struct expect_report never = {
.access = {
{ test_kernel_rmw_array, NULL, 0, 0 },
{ test_kernel_rmw_array, NULL, 0, 0 },
@@ -498,13 +532,13 @@ static void test_concurrent_races(struct kunit *test)
__no_kcsan
static void test_novalue_change(struct kunit *test)
{
- const struct expect_report expect_rw = {
+ struct expect_report expect_rw = {
.access = {
{ test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
},
};
- const struct expect_report expect_ww = {
+ struct expect_report expect_ww = {
.access = {
{ test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
{ test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
@@ -530,13 +564,13 @@ static void test_novalue_change(struct kunit *test)
__no_kcsan
static void test_novalue_change_exception(struct kunit *test)
{
- const struct expect_report expect_rw = {
+ struct expect_report expect_rw = {
.access = {
{ test_kernel_write_nochange_rcu, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
},
};
- const struct expect_report expect_ww = {
+ struct expect_report expect_ww = {
.access = {
{ test_kernel_write_nochange_rcu, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
{ test_kernel_write_nochange_rcu, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
@@ -556,7 +590,7 @@ static void test_novalue_change_exception(struct kunit *test)
__no_kcsan
static void test_unknown_origin(struct kunit *test)
{
- const struct expect_report expect = {
+ struct expect_report expect = {
.access = {
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
{ NULL },
@@ -578,7 +612,7 @@ static void test_unknown_origin(struct kunit *test)
__no_kcsan
static void test_write_write_assume_atomic(struct kunit *test)
{
- const struct expect_report expect = {
+ struct expect_report expect = {
.access = {
{ test_kernel_write, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
{ test_kernel_write, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
@@ -604,7 +638,7 @@ static void test_write_write_assume_atomic(struct kunit *test)
__no_kcsan
static void test_write_write_struct(struct kunit *test)
{
- const struct expect_report expect = {
+ struct expect_report expect = {
.access = {
{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
@@ -626,7 +660,7 @@ static void test_write_write_struct(struct kunit *test)
__no_kcsan
static void test_write_write_struct_part(struct kunit *test)
{
- const struct expect_report expect = {
+ struct expect_report expect = {
.access = {
{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
{ test_kernel_write_struct_part, &test_struct.val[3], sizeof(test_struct.val[3]), KCSAN_ACCESS_WRITE },
@@ -658,7 +692,7 @@ static void test_read_atomic_write_atomic(struct kunit *test)
__no_kcsan
static void test_read_plain_atomic_write(struct kunit *test)
{
- const struct expect_report expect = {
+ struct expect_report expect = {
.access = {
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
{ test_kernel_write_atomic, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC },
@@ -679,7 +713,7 @@ static void test_read_plain_atomic_write(struct kunit *test)
__no_kcsan
static void test_read_plain_atomic_rmw(struct kunit *test)
{
- const struct expect_report expect = {
+ struct expect_report expect = {
.access = {
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
{ test_kernel_atomic_rmw, &test_var, sizeof(test_var),
@@ -701,13 +735,13 @@ static void test_read_plain_atomic_rmw(struct kunit *test)
__no_kcsan
static void test_zero_size_access(struct kunit *test)
{
- const struct expect_report expect = {
+ struct expect_report expect = {
.access = {
{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
},
};
- const struct expect_report never = {
+ struct expect_report never = {
.access = {
{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
{ test_kernel_read_struct_zero_size, &test_struct.val[3], 0, 0 },
@@ -741,7 +775,7 @@ static void test_data_race(struct kunit *test)
__no_kcsan
static void test_assert_exclusive_writer(struct kunit *test)
{
- const struct expect_report expect = {
+ struct expect_report expect = {
.access = {
{ test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
{ test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
@@ -759,7 +793,7 @@ static void test_assert_exclusive_writer(struct kunit *test)
__no_kcsan
static void test_assert_exclusive_access(struct kunit *test)
{
- const struct expect_report expect = {
+ struct expect_report expect = {
.access = {
{ test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
@@ -777,19 +811,19 @@ static void test_assert_exclusive_access(struct kunit *test)
__no_kcsan
static void test_assert_exclusive_access_writer(struct kunit *test)
{
- const struct expect_report expect_access_writer = {
+ struct expect_report expect_access_writer = {
.access = {
{ test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
{ test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
},
};
- const struct expect_report expect_access_access = {
+ struct expect_report expect_access_access = {
.access = {
{ test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
{ test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
},
};
- const struct expect_report never = {
+ struct expect_report never = {
.access = {
{ test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
{ test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
@@ -813,7 +847,7 @@ static void test_assert_exclusive_access_writer(struct kunit *test)
__no_kcsan
static void test_assert_exclusive_bits_change(struct kunit *test)
{
- const struct expect_report expect = {
+ struct expect_report expect = {
.access = {
{ test_kernel_assert_bits_change, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
{ test_kernel_change_bits, &test_var, sizeof(test_var),
@@ -844,13 +878,13 @@ static void test_assert_exclusive_bits_nochange(struct kunit *test)
__no_kcsan
static void test_assert_exclusive_writer_scoped(struct kunit *test)
{
- const struct expect_report expect_start = {
+ struct expect_report expect_start = {
.access = {
{ test_kernel_assert_writer_scoped, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_SCOPED },
{ test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
},
};
- const struct expect_report expect_inscope = {
+ struct expect_report expect_inscope = {
.access = {
{ test_enter_scope, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_SCOPED },
{ test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
@@ -871,16 +905,16 @@ static void test_assert_exclusive_writer_scoped(struct kunit *test)
__no_kcsan
static void test_assert_exclusive_access_scoped(struct kunit *test)
{
- const struct expect_report expect_start1 = {
+ struct expect_report expect_start1 = {
.access = {
{ test_kernel_assert_access_scoped, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_SCOPED },
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
},
};
- const struct expect_report expect_start2 = {
+ struct expect_report expect_start2 = {
.access = { expect_start1.access[0], expect_start1.access[0] },
};
- const struct expect_report expect_inscope = {
+ struct expect_report expect_inscope = {
.access = {
{ test_enter_scope, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_SCOPED },
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
@@ -985,7 +1019,7 @@ static void test_atomic_builtins(struct kunit *test)
__no_kcsan
static void test_1bit_value_change(struct kunit *test)
{
- const struct expect_report expect = {
+ struct expect_report expect = {
.access = {
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
{ test_kernel_xor_1bit, &test_var, sizeof(test_var), __KCSAN_ACCESS_RW(KCSAN_ACCESS_WRITE) },
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 11/29] kcsan: test: Add test cases for memory barrier instrumentation
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (9 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 10/29] kcsan: test: Match reordered or normal accesses Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 12/29] kcsan: Ignore GCC 11+ warnings about TSan runtime support Paul E. McKenney
` (17 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
Adds test cases to check that memory barriers are instrumented
correctly, and detection of missing memory barriers is working as
intended if CONFIG_KCSAN_STRICT=y.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/kcsan/kcsan_test.c | 319 ++++++++++++++++++++++++++++++++++++++
1 file changed, 319 insertions(+)
diff --git a/kernel/kcsan/kcsan_test.c b/kernel/kcsan/kcsan_test.c
index ec054879201b3..5bf94550bcdf6 100644
--- a/kernel/kcsan/kcsan_test.c
+++ b/kernel/kcsan/kcsan_test.c
@@ -16,9 +16,12 @@
#define pr_fmt(fmt) "kcsan_test: " fmt
#include <kunit/test.h>
+#include <linux/atomic.h>
+#include <linux/bitops.h>
#include <linux/jiffies.h>
#include <linux/kcsan-checks.h>
#include <linux/kernel.h>
+#include <linux/mutex.h>
#include <linux/sched.h>
#include <linux/seqlock.h>
#include <linux/spinlock.h>
@@ -305,6 +308,16 @@ static DEFINE_SEQLOCK(test_seqlock);
__no_kcsan
static noinline void sink_value(long v) { WRITE_ONCE(test_sink, v); }
+/*
+ * Generates a delay and some accesses that enter the runtime but do not produce
+ * data races.
+ */
+static noinline void test_delay(int iter)
+{
+ while (iter--)
+ sink_value(READ_ONCE(test_sink));
+}
+
static noinline void test_kernel_read(void) { sink_value(test_var); }
static noinline void test_kernel_write(void)
@@ -466,8 +479,219 @@ static noinline void test_kernel_xor_1bit(void)
kcsan_nestable_atomic_end();
}
+#define TEST_KERNEL_LOCKED(name, acquire, release) \
+ static noinline void test_kernel_##name(void) \
+ { \
+ long *flag = &test_struct.val[0]; \
+ long v = 0; \
+ if (!(acquire)) \
+ return; \
+ while (v++ < 100) { \
+ test_var++; \
+ barrier(); \
+ } \
+ release; \
+ test_delay(10); \
+ }
+
+TEST_KERNEL_LOCKED(with_memorder,
+ cmpxchg_acquire(flag, 0, 1) == 0,
+ smp_store_release(flag, 0));
+TEST_KERNEL_LOCKED(wrong_memorder,
+ cmpxchg_relaxed(flag, 0, 1) == 0,
+ WRITE_ONCE(*flag, 0));
+TEST_KERNEL_LOCKED(atomic_builtin_with_memorder,
+ __atomic_compare_exchange_n(flag, &v, 1, 0, __ATOMIC_ACQUIRE, __ATOMIC_RELAXED),
+ __atomic_store_n(flag, 0, __ATOMIC_RELEASE));
+TEST_KERNEL_LOCKED(atomic_builtin_wrong_memorder,
+ __atomic_compare_exchange_n(flag, &v, 1, 0, __ATOMIC_RELAXED, __ATOMIC_RELAXED),
+ __atomic_store_n(flag, 0, __ATOMIC_RELAXED));
+
/* ===== Test cases ===== */
+/*
+ * Tests that various barriers have the expected effect on internal state. Not
+ * exhaustive on atomic_t operations. Unlike the selftest, also checks for
+ * too-strict barrier instrumentation; these can be tolerated, because it does
+ * not cause false positives, but at least we should be aware of such cases.
+ */
+static void test_barrier_nothreads(struct kunit *test)
+{
+#ifdef CONFIG_KCSAN_WEAK_MEMORY
+ struct kcsan_scoped_access *reorder_access = ¤t->kcsan_ctx.reorder_access;
+#else
+ struct kcsan_scoped_access *reorder_access = NULL;
+#endif
+ arch_spinlock_t arch_spinlock = __ARCH_SPIN_LOCK_UNLOCKED;
+ DEFINE_SPINLOCK(spinlock);
+ DEFINE_MUTEX(mutex);
+ atomic_t dummy;
+
+ KCSAN_TEST_REQUIRES(test, reorder_access != NULL);
+ KCSAN_TEST_REQUIRES(test, IS_ENABLED(CONFIG_SMP));
+
+#define __KCSAN_EXPECT_BARRIER(access_type, barrier, order_before, name) \
+ do { \
+ reorder_access->type = (access_type) | KCSAN_ACCESS_SCOPED; \
+ reorder_access->size = sizeof(test_var); \
+ barrier; \
+ KUNIT_EXPECT_EQ_MSG(test, reorder_access->size, \
+ order_before ? 0 : sizeof(test_var), \
+ "improperly instrumented type=(" #access_type "): " name); \
+ } while (0)
+#define KCSAN_EXPECT_READ_BARRIER(b, o) __KCSAN_EXPECT_BARRIER(0, b, o, #b)
+#define KCSAN_EXPECT_WRITE_BARRIER(b, o) __KCSAN_EXPECT_BARRIER(KCSAN_ACCESS_WRITE, b, o, #b)
+#define KCSAN_EXPECT_RW_BARRIER(b, o) __KCSAN_EXPECT_BARRIER(KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE, b, o, #b)
+
+ /* Force creating a valid entry in reorder_access first. */
+ test_var = 0;
+ while (test_var++ < 1000000 && reorder_access->size != sizeof(test_var))
+ __kcsan_check_read(&test_var, sizeof(test_var));
+ KUNIT_ASSERT_EQ(test, reorder_access->size, sizeof(test_var));
+
+ kcsan_nestable_atomic_begin(); /* No watchpoints in called functions. */
+
+ KCSAN_EXPECT_READ_BARRIER(mb(), true);
+ KCSAN_EXPECT_READ_BARRIER(wmb(), false);
+ KCSAN_EXPECT_READ_BARRIER(rmb(), true);
+ KCSAN_EXPECT_READ_BARRIER(smp_mb(), true);
+ KCSAN_EXPECT_READ_BARRIER(smp_wmb(), false);
+ KCSAN_EXPECT_READ_BARRIER(smp_rmb(), true);
+ KCSAN_EXPECT_READ_BARRIER(dma_wmb(), false);
+ KCSAN_EXPECT_READ_BARRIER(dma_rmb(), true);
+ KCSAN_EXPECT_READ_BARRIER(smp_mb__before_atomic(), true);
+ KCSAN_EXPECT_READ_BARRIER(smp_mb__after_atomic(), true);
+ KCSAN_EXPECT_READ_BARRIER(smp_mb__after_spinlock(), true);
+ KCSAN_EXPECT_READ_BARRIER(smp_store_mb(test_var, 0), true);
+ KCSAN_EXPECT_READ_BARRIER(smp_load_acquire(&test_var), false);
+ KCSAN_EXPECT_READ_BARRIER(smp_store_release(&test_var, 0), true);
+ KCSAN_EXPECT_READ_BARRIER(xchg(&test_var, 0), true);
+ KCSAN_EXPECT_READ_BARRIER(xchg_release(&test_var, 0), true);
+ KCSAN_EXPECT_READ_BARRIER(xchg_relaxed(&test_var, 0), false);
+ KCSAN_EXPECT_READ_BARRIER(cmpxchg(&test_var, 0, 0), true);
+ KCSAN_EXPECT_READ_BARRIER(cmpxchg_release(&test_var, 0, 0), true);
+ KCSAN_EXPECT_READ_BARRIER(cmpxchg_relaxed(&test_var, 0, 0), false);
+ KCSAN_EXPECT_READ_BARRIER(atomic_read(&dummy), false);
+ KCSAN_EXPECT_READ_BARRIER(atomic_read_acquire(&dummy), false);
+ KCSAN_EXPECT_READ_BARRIER(atomic_set(&dummy, 0), false);
+ KCSAN_EXPECT_READ_BARRIER(atomic_set_release(&dummy, 0), true);
+ KCSAN_EXPECT_READ_BARRIER(atomic_add(1, &dummy), false);
+ KCSAN_EXPECT_READ_BARRIER(atomic_add_return(1, &dummy), true);
+ KCSAN_EXPECT_READ_BARRIER(atomic_add_return_acquire(1, &dummy), false);
+ KCSAN_EXPECT_READ_BARRIER(atomic_add_return_release(1, &dummy), true);
+ KCSAN_EXPECT_READ_BARRIER(atomic_add_return_relaxed(1, &dummy), false);
+ KCSAN_EXPECT_READ_BARRIER(atomic_fetch_add(1, &dummy), true);
+ KCSAN_EXPECT_READ_BARRIER(atomic_fetch_add_acquire(1, &dummy), false);
+ KCSAN_EXPECT_READ_BARRIER(atomic_fetch_add_release(1, &dummy), true);
+ KCSAN_EXPECT_READ_BARRIER(atomic_fetch_add_relaxed(1, &dummy), false);
+ KCSAN_EXPECT_READ_BARRIER(test_and_set_bit(0, &test_var), true);
+ KCSAN_EXPECT_READ_BARRIER(test_and_clear_bit(0, &test_var), true);
+ KCSAN_EXPECT_READ_BARRIER(test_and_change_bit(0, &test_var), true);
+ KCSAN_EXPECT_READ_BARRIER(clear_bit_unlock(0, &test_var), true);
+ KCSAN_EXPECT_READ_BARRIER(__clear_bit_unlock(0, &test_var), true);
+ KCSAN_EXPECT_READ_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var), true);
+ KCSAN_EXPECT_READ_BARRIER(arch_spin_lock(&arch_spinlock), false);
+ KCSAN_EXPECT_READ_BARRIER(arch_spin_unlock(&arch_spinlock), true);
+ KCSAN_EXPECT_READ_BARRIER(spin_lock(&spinlock), false);
+ KCSAN_EXPECT_READ_BARRIER(spin_unlock(&spinlock), true);
+ KCSAN_EXPECT_READ_BARRIER(mutex_lock(&mutex), false);
+ KCSAN_EXPECT_READ_BARRIER(mutex_unlock(&mutex), true);
+
+ KCSAN_EXPECT_WRITE_BARRIER(mb(), true);
+ KCSAN_EXPECT_WRITE_BARRIER(wmb(), true);
+ KCSAN_EXPECT_WRITE_BARRIER(rmb(), false);
+ KCSAN_EXPECT_WRITE_BARRIER(smp_mb(), true);
+ KCSAN_EXPECT_WRITE_BARRIER(smp_wmb(), true);
+ KCSAN_EXPECT_WRITE_BARRIER(smp_rmb(), false);
+ KCSAN_EXPECT_WRITE_BARRIER(dma_wmb(), true);
+ KCSAN_EXPECT_WRITE_BARRIER(dma_rmb(), false);
+ KCSAN_EXPECT_WRITE_BARRIER(smp_mb__before_atomic(), true);
+ KCSAN_EXPECT_WRITE_BARRIER(smp_mb__after_atomic(), true);
+ KCSAN_EXPECT_WRITE_BARRIER(smp_mb__after_spinlock(), true);
+ KCSAN_EXPECT_WRITE_BARRIER(smp_store_mb(test_var, 0), true);
+ KCSAN_EXPECT_WRITE_BARRIER(smp_load_acquire(&test_var), false);
+ KCSAN_EXPECT_WRITE_BARRIER(smp_store_release(&test_var, 0), true);
+ KCSAN_EXPECT_WRITE_BARRIER(xchg(&test_var, 0), true);
+ KCSAN_EXPECT_WRITE_BARRIER(xchg_release(&test_var, 0), true);
+ KCSAN_EXPECT_WRITE_BARRIER(xchg_relaxed(&test_var, 0), false);
+ KCSAN_EXPECT_WRITE_BARRIER(cmpxchg(&test_var, 0, 0), true);
+ KCSAN_EXPECT_WRITE_BARRIER(cmpxchg_release(&test_var, 0, 0), true);
+ KCSAN_EXPECT_WRITE_BARRIER(cmpxchg_relaxed(&test_var, 0, 0), false);
+ KCSAN_EXPECT_WRITE_BARRIER(atomic_read(&dummy), false);
+ KCSAN_EXPECT_WRITE_BARRIER(atomic_read_acquire(&dummy), false);
+ KCSAN_EXPECT_WRITE_BARRIER(atomic_set(&dummy, 0), false);
+ KCSAN_EXPECT_WRITE_BARRIER(atomic_set_release(&dummy, 0), true);
+ KCSAN_EXPECT_WRITE_BARRIER(atomic_add(1, &dummy), false);
+ KCSAN_EXPECT_WRITE_BARRIER(atomic_add_return(1, &dummy), true);
+ KCSAN_EXPECT_WRITE_BARRIER(atomic_add_return_acquire(1, &dummy), false);
+ KCSAN_EXPECT_WRITE_BARRIER(atomic_add_return_release(1, &dummy), true);
+ KCSAN_EXPECT_WRITE_BARRIER(atomic_add_return_relaxed(1, &dummy), false);
+ KCSAN_EXPECT_WRITE_BARRIER(atomic_fetch_add(1, &dummy), true);
+ KCSAN_EXPECT_WRITE_BARRIER(atomic_fetch_add_acquire(1, &dummy), false);
+ KCSAN_EXPECT_WRITE_BARRIER(atomic_fetch_add_release(1, &dummy), true);
+ KCSAN_EXPECT_WRITE_BARRIER(atomic_fetch_add_relaxed(1, &dummy), false);
+ KCSAN_EXPECT_WRITE_BARRIER(test_and_set_bit(0, &test_var), true);
+ KCSAN_EXPECT_WRITE_BARRIER(test_and_clear_bit(0, &test_var), true);
+ KCSAN_EXPECT_WRITE_BARRIER(test_and_change_bit(0, &test_var), true);
+ KCSAN_EXPECT_WRITE_BARRIER(clear_bit_unlock(0, &test_var), true);
+ KCSAN_EXPECT_WRITE_BARRIER(__clear_bit_unlock(0, &test_var), true);
+ KCSAN_EXPECT_WRITE_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var), true);
+ KCSAN_EXPECT_WRITE_BARRIER(arch_spin_lock(&arch_spinlock), false);
+ KCSAN_EXPECT_WRITE_BARRIER(arch_spin_unlock(&arch_spinlock), true);
+ KCSAN_EXPECT_WRITE_BARRIER(spin_lock(&spinlock), false);
+ KCSAN_EXPECT_WRITE_BARRIER(spin_unlock(&spinlock), true);
+ KCSAN_EXPECT_WRITE_BARRIER(mutex_lock(&mutex), false);
+ KCSAN_EXPECT_WRITE_BARRIER(mutex_unlock(&mutex), true);
+
+ KCSAN_EXPECT_RW_BARRIER(mb(), true);
+ KCSAN_EXPECT_RW_BARRIER(wmb(), true);
+ KCSAN_EXPECT_RW_BARRIER(rmb(), true);
+ KCSAN_EXPECT_RW_BARRIER(smp_mb(), true);
+ KCSAN_EXPECT_RW_BARRIER(smp_wmb(), true);
+ KCSAN_EXPECT_RW_BARRIER(smp_rmb(), true);
+ KCSAN_EXPECT_RW_BARRIER(dma_wmb(), true);
+ KCSAN_EXPECT_RW_BARRIER(dma_rmb(), true);
+ KCSAN_EXPECT_RW_BARRIER(smp_mb__before_atomic(), true);
+ KCSAN_EXPECT_RW_BARRIER(smp_mb__after_atomic(), true);
+ KCSAN_EXPECT_RW_BARRIER(smp_mb__after_spinlock(), true);
+ KCSAN_EXPECT_RW_BARRIER(smp_store_mb(test_var, 0), true);
+ KCSAN_EXPECT_RW_BARRIER(smp_load_acquire(&test_var), false);
+ KCSAN_EXPECT_RW_BARRIER(smp_store_release(&test_var, 0), true);
+ KCSAN_EXPECT_RW_BARRIER(xchg(&test_var, 0), true);
+ KCSAN_EXPECT_RW_BARRIER(xchg_release(&test_var, 0), true);
+ KCSAN_EXPECT_RW_BARRIER(xchg_relaxed(&test_var, 0), false);
+ KCSAN_EXPECT_RW_BARRIER(cmpxchg(&test_var, 0, 0), true);
+ KCSAN_EXPECT_RW_BARRIER(cmpxchg_release(&test_var, 0, 0), true);
+ KCSAN_EXPECT_RW_BARRIER(cmpxchg_relaxed(&test_var, 0, 0), false);
+ KCSAN_EXPECT_RW_BARRIER(atomic_read(&dummy), false);
+ KCSAN_EXPECT_RW_BARRIER(atomic_read_acquire(&dummy), false);
+ KCSAN_EXPECT_RW_BARRIER(atomic_set(&dummy, 0), false);
+ KCSAN_EXPECT_RW_BARRIER(atomic_set_release(&dummy, 0), true);
+ KCSAN_EXPECT_RW_BARRIER(atomic_add(1, &dummy), false);
+ KCSAN_EXPECT_RW_BARRIER(atomic_add_return(1, &dummy), true);
+ KCSAN_EXPECT_RW_BARRIER(atomic_add_return_acquire(1, &dummy), false);
+ KCSAN_EXPECT_RW_BARRIER(atomic_add_return_release(1, &dummy), true);
+ KCSAN_EXPECT_RW_BARRIER(atomic_add_return_relaxed(1, &dummy), false);
+ KCSAN_EXPECT_RW_BARRIER(atomic_fetch_add(1, &dummy), true);
+ KCSAN_EXPECT_RW_BARRIER(atomic_fetch_add_acquire(1, &dummy), false);
+ KCSAN_EXPECT_RW_BARRIER(atomic_fetch_add_release(1, &dummy), true);
+ KCSAN_EXPECT_RW_BARRIER(atomic_fetch_add_relaxed(1, &dummy), false);
+ KCSAN_EXPECT_RW_BARRIER(test_and_set_bit(0, &test_var), true);
+ KCSAN_EXPECT_RW_BARRIER(test_and_clear_bit(0, &test_var), true);
+ KCSAN_EXPECT_RW_BARRIER(test_and_change_bit(0, &test_var), true);
+ KCSAN_EXPECT_RW_BARRIER(clear_bit_unlock(0, &test_var), true);
+ KCSAN_EXPECT_RW_BARRIER(__clear_bit_unlock(0, &test_var), true);
+ KCSAN_EXPECT_RW_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var), true);
+ KCSAN_EXPECT_RW_BARRIER(arch_spin_lock(&arch_spinlock), false);
+ KCSAN_EXPECT_RW_BARRIER(arch_spin_unlock(&arch_spinlock), true);
+ KCSAN_EXPECT_RW_BARRIER(spin_lock(&spinlock), false);
+ KCSAN_EXPECT_RW_BARRIER(spin_unlock(&spinlock), true);
+ KCSAN_EXPECT_RW_BARRIER(mutex_lock(&mutex), false);
+ KCSAN_EXPECT_RW_BARRIER(mutex_unlock(&mutex), true);
+
+ kcsan_nestable_atomic_end();
+}
+
/* Simple test with normal data race. */
__no_kcsan
static void test_basic(struct kunit *test)
@@ -1039,6 +1263,90 @@ static void test_1bit_value_change(struct kunit *test)
KUNIT_EXPECT_TRUE(test, match);
}
+__no_kcsan
+static void test_correct_barrier(struct kunit *test)
+{
+ struct expect_report expect = {
+ .access = {
+ { test_kernel_with_memorder, &test_var, sizeof(test_var), __KCSAN_ACCESS_RW(KCSAN_ACCESS_WRITE) },
+ { test_kernel_with_memorder, &test_var, sizeof(test_var), __KCSAN_ACCESS_RW(0) },
+ },
+ };
+ bool match_expect = false;
+
+ test_struct.val[0] = 0; /* init unlocked */
+ begin_test_checks(test_kernel_with_memorder, test_kernel_with_memorder);
+ do {
+ match_expect = report_matches_any_reordered(&expect);
+ } while (!end_test_checks(match_expect));
+ KUNIT_EXPECT_FALSE(test, match_expect);
+}
+
+__no_kcsan
+static void test_missing_barrier(struct kunit *test)
+{
+ struct expect_report expect = {
+ .access = {
+ { test_kernel_wrong_memorder, &test_var, sizeof(test_var), __KCSAN_ACCESS_RW(KCSAN_ACCESS_WRITE) },
+ { test_kernel_wrong_memorder, &test_var, sizeof(test_var), __KCSAN_ACCESS_RW(0) },
+ },
+ };
+ bool match_expect = false;
+
+ test_struct.val[0] = 0; /* init unlocked */
+ begin_test_checks(test_kernel_wrong_memorder, test_kernel_wrong_memorder);
+ do {
+ match_expect = report_matches_any_reordered(&expect);
+ } while (!end_test_checks(match_expect));
+ if (IS_ENABLED(CONFIG_KCSAN_WEAK_MEMORY))
+ KUNIT_EXPECT_TRUE(test, match_expect);
+ else
+ KUNIT_EXPECT_FALSE(test, match_expect);
+}
+
+__no_kcsan
+static void test_atomic_builtins_correct_barrier(struct kunit *test)
+{
+ struct expect_report expect = {
+ .access = {
+ { test_kernel_atomic_builtin_with_memorder, &test_var, sizeof(test_var), __KCSAN_ACCESS_RW(KCSAN_ACCESS_WRITE) },
+ { test_kernel_atomic_builtin_with_memorder, &test_var, sizeof(test_var), __KCSAN_ACCESS_RW(0) },
+ },
+ };
+ bool match_expect = false;
+
+ test_struct.val[0] = 0; /* init unlocked */
+ begin_test_checks(test_kernel_atomic_builtin_with_memorder,
+ test_kernel_atomic_builtin_with_memorder);
+ do {
+ match_expect = report_matches_any_reordered(&expect);
+ } while (!end_test_checks(match_expect));
+ KUNIT_EXPECT_FALSE(test, match_expect);
+}
+
+__no_kcsan
+static void test_atomic_builtins_missing_barrier(struct kunit *test)
+{
+ struct expect_report expect = {
+ .access = {
+ { test_kernel_atomic_builtin_wrong_memorder, &test_var, sizeof(test_var), __KCSAN_ACCESS_RW(KCSAN_ACCESS_WRITE) },
+ { test_kernel_atomic_builtin_wrong_memorder, &test_var, sizeof(test_var), __KCSAN_ACCESS_RW(0) },
+ },
+ };
+ bool match_expect = false;
+
+ test_struct.val[0] = 0; /* init unlocked */
+ begin_test_checks(test_kernel_atomic_builtin_wrong_memorder,
+ test_kernel_atomic_builtin_wrong_memorder);
+ do {
+ match_expect = report_matches_any_reordered(&expect);
+ } while (!end_test_checks(match_expect));
+ if (IS_ENABLED(CONFIG_KCSAN_WEAK_MEMORY))
+ KUNIT_EXPECT_TRUE(test, match_expect);
+ else
+ KUNIT_EXPECT_FALSE(test, match_expect);
+}
+
/*
* Generate thread counts for all test cases. Values generated are in interval
* [2, 5] followed by exponentially increasing thread counts from 8 to 32.
@@ -1088,6 +1396,7 @@ static const void *nthreads_gen_params(const void *prev, char *desc)
#define KCSAN_KUNIT_CASE(test_name) KUNIT_CASE_PARAM(test_name, nthreads_gen_params)
static struct kunit_case kcsan_test_cases[] = {
+ KUNIT_CASE(test_barrier_nothreads),
KCSAN_KUNIT_CASE(test_basic),
KCSAN_KUNIT_CASE(test_concurrent_races),
KCSAN_KUNIT_CASE(test_novalue_change),
@@ -1112,6 +1421,10 @@ static struct kunit_case kcsan_test_cases[] = {
KCSAN_KUNIT_CASE(test_seqlock_noreport),
KCSAN_KUNIT_CASE(test_atomic_builtins),
KCSAN_KUNIT_CASE(test_1bit_value_change),
+ KCSAN_KUNIT_CASE(test_correct_barrier),
+ KCSAN_KUNIT_CASE(test_missing_barrier),
+ KCSAN_KUNIT_CASE(test_atomic_builtins_correct_barrier),
+ KCSAN_KUNIT_CASE(test_atomic_builtins_missing_barrier),
{},
};
@@ -1176,6 +1489,9 @@ static int test_init(struct kunit *test)
observed.nlines = 0;
spin_unlock_irqrestore(&observed.lock, flags);
+ if (strstr(test->name, "nothreads"))
+ return 0;
+
if (!torture_init_begin((char *)test->name, 1))
return -EBUSY;
@@ -1218,6 +1534,9 @@ static void test_exit(struct kunit *test)
struct task_struct **stop_thread;
int i;
+ if (strstr(test->name, "nothreads"))
+ return;
+
if (torture_cleanup_begin())
return;
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 12/29] kcsan: Ignore GCC 11+ warnings about TSan runtime support
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (10 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 11/29] kcsan: test: Add test cases for memory barrier instrumentation Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 13/29] kcsan: selftest: Add test case to check memory barrier instrumentation Paul E. McKenney
` (16 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
GCC 11 has introduced a new warning option, -Wtsan [1], to warn about
unsupported operations in the TSan runtime. But KCSAN != TSan runtime,
so none of the warnings apply.
[1] https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/Warning-Options.html
Ignore the warnings.
Currently the warning only fires in the test for __atomic_thread_fence():
kernel/kcsan/kcsan_test.c: In function ‘test_atomic_builtins’:
kernel/kcsan/kcsan_test.c:1234:17: warning: ‘atomic_thread_fence’ is not supported with ‘-fsanitize=thread’ [-Wtsan]
1234 | __atomic_thread_fence(__ATOMIC_SEQ_CST);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
which exists to ensure the KCSAN runtime keeps supporting the builtin
instrumentation.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
scripts/Makefile.kcsan | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/scripts/Makefile.kcsan b/scripts/Makefile.kcsan
index 4c7f0d282e42f..19f693b68a968 100644
--- a/scripts/Makefile.kcsan
+++ b/scripts/Makefile.kcsan
@@ -13,6 +13,12 @@ kcsan-cflags := -fsanitize=thread -fno-optimize-sibling-calls \
$(call cc-option,$(call cc-param,tsan-compound-read-before-write=1),$(call cc-option,$(call cc-param,tsan-instrument-read-before-write=1))) \
$(call cc-param,tsan-distinguish-volatile=1)
+ifdef CONFIG_CC_IS_GCC
+# GCC started warning about operations unsupported by the TSan runtime. But
+# KCSAN != TSan, so just ignore these warnings.
+kcsan-cflags += -Wno-tsan
+endif
+
ifndef CONFIG_KCSAN_WEAK_MEMORY
kcsan-cflags += $(call cc-option,$(call cc-param,tsan-instrument-func-entry-exit=0))
endif
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 13/29] kcsan: selftest: Add test case to check memory barrier instrumentation
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (11 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 12/29] kcsan: Ignore GCC 11+ warnings about TSan runtime support Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 14/29] locking/barriers, kcsan: Add instrumentation for barriers Paul E. McKenney
` (15 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
Memory barrier instrumentation is crucial to avoid false positives. To
avoid surprises, run a simple test case in the boot-time selftest to
ensure memory barriers are still instrumented correctly.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/kcsan/Makefile | 2 +
kernel/kcsan/selftest.c | 141 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 143 insertions(+)
diff --git a/kernel/kcsan/Makefile b/kernel/kcsan/Makefile
index c2bb07f5bcc72..ff47e896de3ba 100644
--- a/kernel/kcsan/Makefile
+++ b/kernel/kcsan/Makefile
@@ -11,6 +11,8 @@ CFLAGS_core.o := $(call cc-option,-fno-conserve-stack) \
-fno-stack-protector -DDISABLE_BRANCH_PROFILING
obj-y := core.o debugfs.o report.o
+
+KCSAN_INSTRUMENT_BARRIERS_selftest.o := y
obj-$(CONFIG_KCSAN_SELFTEST) += selftest.o
CFLAGS_kcsan_test.o := $(CFLAGS_KCSAN) -g -fno-omit-frame-pointer
diff --git a/kernel/kcsan/selftest.c b/kernel/kcsan/selftest.c
index b4295a3892b7c..08c6b84b9ebed 100644
--- a/kernel/kcsan/selftest.c
+++ b/kernel/kcsan/selftest.c
@@ -7,10 +7,15 @@
#define pr_fmt(fmt) "kcsan: " fmt
+#include <linux/atomic.h>
+#include <linux/bitops.h>
#include <linux/init.h>
+#include <linux/kcsan-checks.h>
#include <linux/kernel.h>
#include <linux/printk.h>
#include <linux/random.h>
+#include <linux/sched.h>
+#include <linux/spinlock.h>
#include <linux/types.h>
#include "encoding.h"
@@ -103,6 +108,141 @@ static bool __init test_matching_access(void)
return true;
}
+/*
+ * Correct memory barrier instrumentation is critical to avoiding false
+ * positives: simple test to check at boot certain barriers are always properly
+ * instrumented. See kcsan_test for a more complete test.
+ */
+static bool __init test_barrier(void)
+{
+#ifdef CONFIG_KCSAN_WEAK_MEMORY
+ struct kcsan_scoped_access *reorder_access = ¤t->kcsan_ctx.reorder_access;
+#else
+ struct kcsan_scoped_access *reorder_access = NULL;
+#endif
+ bool ret = true;
+ arch_spinlock_t arch_spinlock = __ARCH_SPIN_LOCK_UNLOCKED;
+ DEFINE_SPINLOCK(spinlock);
+ atomic_t dummy;
+ long test_var;
+
+ if (!reorder_access || !IS_ENABLED(CONFIG_SMP))
+ return true;
+
+#define __KCSAN_CHECK_BARRIER(access_type, barrier, name) \
+ do { \
+ reorder_access->type = (access_type) | KCSAN_ACCESS_SCOPED; \
+ reorder_access->size = 1; \
+ barrier; \
+ if (reorder_access->size != 0) { \
+ pr_err("improperly instrumented type=(" #access_type "): " name "\n"); \
+ ret = false; \
+ } \
+ } while (0)
+#define KCSAN_CHECK_READ_BARRIER(b) __KCSAN_CHECK_BARRIER(0, b, #b)
+#define KCSAN_CHECK_WRITE_BARRIER(b) __KCSAN_CHECK_BARRIER(KCSAN_ACCESS_WRITE, b, #b)
+#define KCSAN_CHECK_RW_BARRIER(b) __KCSAN_CHECK_BARRIER(KCSAN_ACCESS_WRITE | KCSAN_ACCESS_COMPOUND, b, #b)
+
+ kcsan_nestable_atomic_begin(); /* No watchpoints in called functions. */
+
+ KCSAN_CHECK_READ_BARRIER(mb());
+ KCSAN_CHECK_READ_BARRIER(rmb());
+ KCSAN_CHECK_READ_BARRIER(smp_mb());
+ KCSAN_CHECK_READ_BARRIER(smp_rmb());
+ KCSAN_CHECK_READ_BARRIER(dma_rmb());
+ KCSAN_CHECK_READ_BARRIER(smp_mb__before_atomic());
+ KCSAN_CHECK_READ_BARRIER(smp_mb__after_atomic());
+ KCSAN_CHECK_READ_BARRIER(smp_mb__after_spinlock());
+ KCSAN_CHECK_READ_BARRIER(smp_store_mb(test_var, 0));
+ KCSAN_CHECK_READ_BARRIER(smp_store_release(&test_var, 0));
+ KCSAN_CHECK_READ_BARRIER(xchg(&test_var, 0));
+ KCSAN_CHECK_READ_BARRIER(xchg_release(&test_var, 0));
+ KCSAN_CHECK_READ_BARRIER(cmpxchg(&test_var, 0, 0));
+ KCSAN_CHECK_READ_BARRIER(cmpxchg_release(&test_var, 0, 0));
+ KCSAN_CHECK_READ_BARRIER(atomic_set_release(&dummy, 0));
+ KCSAN_CHECK_READ_BARRIER(atomic_add_return(1, &dummy));
+ KCSAN_CHECK_READ_BARRIER(atomic_add_return_release(1, &dummy));
+ KCSAN_CHECK_READ_BARRIER(atomic_fetch_add(1, &dummy));
+ KCSAN_CHECK_READ_BARRIER(atomic_fetch_add_release(1, &dummy));
+ KCSAN_CHECK_READ_BARRIER(test_and_set_bit(0, &test_var));
+ KCSAN_CHECK_READ_BARRIER(test_and_clear_bit(0, &test_var));
+ KCSAN_CHECK_READ_BARRIER(test_and_change_bit(0, &test_var));
+ KCSAN_CHECK_READ_BARRIER(clear_bit_unlock(0, &test_var));
+ KCSAN_CHECK_READ_BARRIER(__clear_bit_unlock(0, &test_var));
+ KCSAN_CHECK_READ_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var));
+ arch_spin_lock(&arch_spinlock);
+ KCSAN_CHECK_READ_BARRIER(arch_spin_unlock(&arch_spinlock));
+ spin_lock(&spinlock);
+ KCSAN_CHECK_READ_BARRIER(spin_unlock(&spinlock));
+
+ KCSAN_CHECK_WRITE_BARRIER(mb());
+ KCSAN_CHECK_WRITE_BARRIER(wmb());
+ KCSAN_CHECK_WRITE_BARRIER(smp_mb());
+ KCSAN_CHECK_WRITE_BARRIER(smp_wmb());
+ KCSAN_CHECK_WRITE_BARRIER(dma_wmb());
+ KCSAN_CHECK_WRITE_BARRIER(smp_mb__before_atomic());
+ KCSAN_CHECK_WRITE_BARRIER(smp_mb__after_atomic());
+ KCSAN_CHECK_WRITE_BARRIER(smp_mb__after_spinlock());
+ KCSAN_CHECK_WRITE_BARRIER(smp_store_mb(test_var, 0));
+ KCSAN_CHECK_WRITE_BARRIER(smp_store_release(&test_var, 0));
+ KCSAN_CHECK_WRITE_BARRIER(xchg(&test_var, 0));
+ KCSAN_CHECK_WRITE_BARRIER(xchg_release(&test_var, 0));
+ KCSAN_CHECK_WRITE_BARRIER(cmpxchg(&test_var, 0, 0));
+ KCSAN_CHECK_WRITE_BARRIER(cmpxchg_release(&test_var, 0, 0));
+ KCSAN_CHECK_WRITE_BARRIER(atomic_set_release(&dummy, 0));
+ KCSAN_CHECK_WRITE_BARRIER(atomic_add_return(1, &dummy));
+ KCSAN_CHECK_WRITE_BARRIER(atomic_add_return_release(1, &dummy));
+ KCSAN_CHECK_WRITE_BARRIER(atomic_fetch_add(1, &dummy));
+ KCSAN_CHECK_WRITE_BARRIER(atomic_fetch_add_release(1, &dummy));
+ KCSAN_CHECK_WRITE_BARRIER(test_and_set_bit(0, &test_var));
+ KCSAN_CHECK_WRITE_BARRIER(test_and_clear_bit(0, &test_var));
+ KCSAN_CHECK_WRITE_BARRIER(test_and_change_bit(0, &test_var));
+ KCSAN_CHECK_WRITE_BARRIER(clear_bit_unlock(0, &test_var));
+ KCSAN_CHECK_WRITE_BARRIER(__clear_bit_unlock(0, &test_var));
+ KCSAN_CHECK_WRITE_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var));
+ arch_spin_lock(&arch_spinlock);
+ KCSAN_CHECK_WRITE_BARRIER(arch_spin_unlock(&arch_spinlock));
+ spin_lock(&spinlock);
+ KCSAN_CHECK_WRITE_BARRIER(spin_unlock(&spinlock));
+
+ KCSAN_CHECK_RW_BARRIER(mb());
+ KCSAN_CHECK_RW_BARRIER(wmb());
+ KCSAN_CHECK_RW_BARRIER(rmb());
+ KCSAN_CHECK_RW_BARRIER(smp_mb());
+ KCSAN_CHECK_RW_BARRIER(smp_wmb());
+ KCSAN_CHECK_RW_BARRIER(smp_rmb());
+ KCSAN_CHECK_RW_BARRIER(dma_wmb());
+ KCSAN_CHECK_RW_BARRIER(dma_rmb());
+ KCSAN_CHECK_RW_BARRIER(smp_mb__before_atomic());
+ KCSAN_CHECK_RW_BARRIER(smp_mb__after_atomic());
+ KCSAN_CHECK_RW_BARRIER(smp_mb__after_spinlock());
+ KCSAN_CHECK_RW_BARRIER(smp_store_mb(test_var, 0));
+ KCSAN_CHECK_RW_BARRIER(smp_store_release(&test_var, 0));
+ KCSAN_CHECK_RW_BARRIER(xchg(&test_var, 0));
+ KCSAN_CHECK_RW_BARRIER(xchg_release(&test_var, 0));
+ KCSAN_CHECK_RW_BARRIER(cmpxchg(&test_var, 0, 0));
+ KCSAN_CHECK_RW_BARRIER(cmpxchg_release(&test_var, 0, 0));
+ KCSAN_CHECK_RW_BARRIER(atomic_set_release(&dummy, 0));
+ KCSAN_CHECK_RW_BARRIER(atomic_add_return(1, &dummy));
+ KCSAN_CHECK_RW_BARRIER(atomic_add_return_release(1, &dummy));
+ KCSAN_CHECK_RW_BARRIER(atomic_fetch_add(1, &dummy));
+ KCSAN_CHECK_RW_BARRIER(atomic_fetch_add_release(1, &dummy));
+ KCSAN_CHECK_RW_BARRIER(test_and_set_bit(0, &test_var));
+ KCSAN_CHECK_RW_BARRIER(test_and_clear_bit(0, &test_var));
+ KCSAN_CHECK_RW_BARRIER(test_and_change_bit(0, &test_var));
+ KCSAN_CHECK_RW_BARRIER(clear_bit_unlock(0, &test_var));
+ KCSAN_CHECK_RW_BARRIER(__clear_bit_unlock(0, &test_var));
+ KCSAN_CHECK_RW_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var));
+ arch_spin_lock(&arch_spinlock);
+ KCSAN_CHECK_RW_BARRIER(arch_spin_unlock(&arch_spinlock));
+ spin_lock(&spinlock);
+ KCSAN_CHECK_RW_BARRIER(spin_unlock(&spinlock));
+
+ kcsan_nestable_atomic_end();
+
+ return ret;
+}
+
static int __init kcsan_selftest(void)
{
int passed = 0;
@@ -120,6 +260,7 @@ static int __init kcsan_selftest(void)
RUN_TEST(test_requires);
RUN_TEST(test_encode_decode);
RUN_TEST(test_matching_access);
+ RUN_TEST(test_barrier);
pr_info("selftest: %d/%d tests passed\n", passed, total);
if (passed != total)
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 14/29] locking/barriers, kcsan: Add instrumentation for barriers
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (12 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 13/29] kcsan: selftest: Add test case to check memory barrier instrumentation Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 15/29] locking/barriers, kcsan: Support generic instrumentation Paul E. McKenney
` (14 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
Adds the required KCSAN instrumentation for barriers if CONFIG_SMP.
KCSAN supports modeling the effects of:
smp_mb()
smp_rmb()
smp_wmb()
smp_store_release()
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
include/asm-generic/barrier.h | 29 +++++++++++++++--------------
include/linux/spinlock.h | 2 +-
2 files changed, 16 insertions(+), 15 deletions(-)
diff --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h
index 640f09479bdf7..27a9c9edfef66 100644
--- a/include/asm-generic/barrier.h
+++ b/include/asm-generic/barrier.h
@@ -14,6 +14,7 @@
#ifndef __ASSEMBLY__
#include <linux/compiler.h>
+#include <linux/kcsan-checks.h>
#include <asm/rwonce.h>
#ifndef nop
@@ -62,15 +63,15 @@
#ifdef CONFIG_SMP
#ifndef smp_mb
-#define smp_mb() __smp_mb()
+#define smp_mb() do { kcsan_mb(); __smp_mb(); } while (0)
#endif
#ifndef smp_rmb
-#define smp_rmb() __smp_rmb()
+#define smp_rmb() do { kcsan_rmb(); __smp_rmb(); } while (0)
#endif
#ifndef smp_wmb
-#define smp_wmb() __smp_wmb()
+#define smp_wmb() do { kcsan_wmb(); __smp_wmb(); } while (0)
#endif
#else /* !CONFIG_SMP */
@@ -123,19 +124,19 @@ do { \
#ifdef CONFIG_SMP
#ifndef smp_store_mb
-#define smp_store_mb(var, value) __smp_store_mb(var, value)
+#define smp_store_mb(var, value) do { kcsan_mb(); __smp_store_mb(var, value); } while (0)
#endif
#ifndef smp_mb__before_atomic
-#define smp_mb__before_atomic() __smp_mb__before_atomic()
+#define smp_mb__before_atomic() do { kcsan_mb(); __smp_mb__before_atomic(); } while (0)
#endif
#ifndef smp_mb__after_atomic
-#define smp_mb__after_atomic() __smp_mb__after_atomic()
+#define smp_mb__after_atomic() do { kcsan_mb(); __smp_mb__after_atomic(); } while (0)
#endif
#ifndef smp_store_release
-#define smp_store_release(p, v) __smp_store_release(p, v)
+#define smp_store_release(p, v) do { kcsan_release(); __smp_store_release(p, v); } while (0)
#endif
#ifndef smp_load_acquire
@@ -178,13 +179,13 @@ do { \
#endif /* CONFIG_SMP */
/* Barriers for virtual machine guests when talking to an SMP host */
-#define virt_mb() __smp_mb()
-#define virt_rmb() __smp_rmb()
-#define virt_wmb() __smp_wmb()
-#define virt_store_mb(var, value) __smp_store_mb(var, value)
-#define virt_mb__before_atomic() __smp_mb__before_atomic()
-#define virt_mb__after_atomic() __smp_mb__after_atomic()
-#define virt_store_release(p, v) __smp_store_release(p, v)
+#define virt_mb() do { kcsan_mb(); __smp_mb(); } while (0)
+#define virt_rmb() do { kcsan_rmb(); __smp_rmb(); } while (0)
+#define virt_wmb() do { kcsan_wmb(); __smp_wmb(); } while (0)
+#define virt_store_mb(var, value) do { kcsan_mb(); __smp_store_mb(var, value); } while (0)
+#define virt_mb__before_atomic() do { kcsan_mb(); __smp_mb__before_atomic(); } while (0)
+#define virt_mb__after_atomic() do { kcsan_mb(); __smp_mb__after_atomic(); } while (0)
+#define virt_store_release(p, v) do { kcsan_release(); __smp_store_release(p, v); } while (0)
#define virt_load_acquire(p) __smp_load_acquire(p)
/**
diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h
index b4e5ca23f8403..5c0c5174155d0 100644
--- a/include/linux/spinlock.h
+++ b/include/linux/spinlock.h
@@ -171,7 +171,7 @@ do { \
* Architectures that can implement ACQUIRE better need to take care.
*/
#ifndef smp_mb__after_spinlock
-#define smp_mb__after_spinlock() do { } while (0)
+#define smp_mb__after_spinlock() kcsan_mb()
#endif
#ifdef CONFIG_DEBUG_SPINLOCK
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 15/29] locking/barriers, kcsan: Support generic instrumentation
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (13 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 14/29] locking/barriers, kcsan: Add instrumentation for barriers Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 16/29] locking/atomics, kcsan: Add instrumentation for barriers Paul E. McKenney
` (13 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
Thus far only smp_*() barriers had been defined by asm-generic/barrier.h
based on __smp_*() barriers, because the !SMP case is usually generic.
With the introduction of instrumentation, it also makes sense to have
asm-generic/barrier.h assist in the definition of instrumented versions
of mb(), rmb(), wmb(), dma_rmb(), and dma_wmb().
Because there is no requirement to distinguish the !SMP case, the
definition can be simpler: we can avoid also providing fallbacks for the
__ prefixed cases, and only check if `defined(__<barrier>)`, to finally
define the KCSAN-instrumented versions.
This also allows for the compiler to complain if an architecture
accidentally defines both the normal and __ prefixed variant.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
include/asm-generic/barrier.h | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h
index 27a9c9edfef66..02c4339c8eebf 100644
--- a/include/asm-generic/barrier.h
+++ b/include/asm-generic/barrier.h
@@ -21,6 +21,31 @@
#define nop() asm volatile ("nop")
#endif
+/*
+ * Architectures that want generic instrumentation can define __ prefixed
+ * variants of all barriers.
+ */
+
+#ifdef __mb
+#define mb() do { kcsan_mb(); __mb(); } while (0)
+#endif
+
+#ifdef __rmb
+#define rmb() do { kcsan_rmb(); __rmb(); } while (0)
+#endif
+
+#ifdef __wmb
+#define wmb() do { kcsan_wmb(); __wmb(); } while (0)
+#endif
+
+#ifdef __dma_rmb
+#define dma_rmb() do { kcsan_rmb(); __dma_rmb(); } while (0)
+#endif
+
+#ifdef __dma_wmb
+#define dma_wmb() do { kcsan_wmb(); __dma_wmb(); } while (0)
+#endif
+
/*
* Force strict CPU ordering. And yes, this is required on UP too when we're
* talking to devices.
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 16/29] locking/atomics, kcsan: Add instrumentation for barriers
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (14 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 15/29] locking/barriers, kcsan: Support generic instrumentation Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 17/29] asm-generic/bitops, " Paul E. McKenney
` (12 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
Adds the required KCSAN instrumentation for barriers of atomics.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
include/linux/atomic/atomic-instrumented.h | 135 ++++++++++++++++++++-
scripts/atomic/gen-atomic-instrumented.sh | 41 +++++--
2 files changed, 166 insertions(+), 10 deletions(-)
diff --git a/include/linux/atomic/atomic-instrumented.h b/include/linux/atomic/atomic-instrumented.h
index a0f654370da3a..5d69b143c28e6 100644
--- a/include/linux/atomic/atomic-instrumented.h
+++ b/include/linux/atomic/atomic-instrumented.h
@@ -45,6 +45,7 @@ atomic_set(atomic_t *v, int i)
static __always_inline void
atomic_set_release(atomic_t *v, int i)
{
+ kcsan_release();
instrument_atomic_write(v, sizeof(*v));
arch_atomic_set_release(v, i);
}
@@ -59,6 +60,7 @@ atomic_add(int i, atomic_t *v)
static __always_inline int
atomic_add_return(int i, atomic_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_add_return(i, v);
}
@@ -73,6 +75,7 @@ atomic_add_return_acquire(int i, atomic_t *v)
static __always_inline int
atomic_add_return_release(int i, atomic_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_add_return_release(i, v);
}
@@ -87,6 +90,7 @@ atomic_add_return_relaxed(int i, atomic_t *v)
static __always_inline int
atomic_fetch_add(int i, atomic_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_fetch_add(i, v);
}
@@ -101,6 +105,7 @@ atomic_fetch_add_acquire(int i, atomic_t *v)
static __always_inline int
atomic_fetch_add_release(int i, atomic_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_fetch_add_release(i, v);
}
@@ -122,6 +127,7 @@ atomic_sub(int i, atomic_t *v)
static __always_inline int
atomic_sub_return(int i, atomic_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_sub_return(i, v);
}
@@ -136,6 +142,7 @@ atomic_sub_return_acquire(int i, atomic_t *v)
static __always_inline int
atomic_sub_return_release(int i, atomic_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_sub_return_release(i, v);
}
@@ -150,6 +157,7 @@ atomic_sub_return_relaxed(int i, atomic_t *v)
static __always_inline int
atomic_fetch_sub(int i, atomic_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_fetch_sub(i, v);
}
@@ -164,6 +172,7 @@ atomic_fetch_sub_acquire(int i, atomic_t *v)
static __always_inline int
atomic_fetch_sub_release(int i, atomic_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_fetch_sub_release(i, v);
}
@@ -185,6 +194,7 @@ atomic_inc(atomic_t *v)
static __always_inline int
atomic_inc_return(atomic_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_inc_return(v);
}
@@ -199,6 +209,7 @@ atomic_inc_return_acquire(atomic_t *v)
static __always_inline int
atomic_inc_return_release(atomic_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_inc_return_release(v);
}
@@ -213,6 +224,7 @@ atomic_inc_return_relaxed(atomic_t *v)
static __always_inline int
atomic_fetch_inc(atomic_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_fetch_inc(v);
}
@@ -227,6 +239,7 @@ atomic_fetch_inc_acquire(atomic_t *v)
static __always_inline int
atomic_fetch_inc_release(atomic_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_fetch_inc_release(v);
}
@@ -248,6 +261,7 @@ atomic_dec(atomic_t *v)
static __always_inline int
atomic_dec_return(atomic_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_dec_return(v);
}
@@ -262,6 +276,7 @@ atomic_dec_return_acquire(atomic_t *v)
static __always_inline int
atomic_dec_return_release(atomic_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_dec_return_release(v);
}
@@ -276,6 +291,7 @@ atomic_dec_return_relaxed(atomic_t *v)
static __always_inline int
atomic_fetch_dec(atomic_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_fetch_dec(v);
}
@@ -290,6 +306,7 @@ atomic_fetch_dec_acquire(atomic_t *v)
static __always_inline int
atomic_fetch_dec_release(atomic_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_fetch_dec_release(v);
}
@@ -311,6 +328,7 @@ atomic_and(int i, atomic_t *v)
static __always_inline int
atomic_fetch_and(int i, atomic_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_fetch_and(i, v);
}
@@ -325,6 +343,7 @@ atomic_fetch_and_acquire(int i, atomic_t *v)
static __always_inline int
atomic_fetch_and_release(int i, atomic_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_fetch_and_release(i, v);
}
@@ -346,6 +365,7 @@ atomic_andnot(int i, atomic_t *v)
static __always_inline int
atomic_fetch_andnot(int i, atomic_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_fetch_andnot(i, v);
}
@@ -360,6 +380,7 @@ atomic_fetch_andnot_acquire(int i, atomic_t *v)
static __always_inline int
atomic_fetch_andnot_release(int i, atomic_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_fetch_andnot_release(i, v);
}
@@ -381,6 +402,7 @@ atomic_or(int i, atomic_t *v)
static __always_inline int
atomic_fetch_or(int i, atomic_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_fetch_or(i, v);
}
@@ -395,6 +417,7 @@ atomic_fetch_or_acquire(int i, atomic_t *v)
static __always_inline int
atomic_fetch_or_release(int i, atomic_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_fetch_or_release(i, v);
}
@@ -416,6 +439,7 @@ atomic_xor(int i, atomic_t *v)
static __always_inline int
atomic_fetch_xor(int i, atomic_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_fetch_xor(i, v);
}
@@ -430,6 +454,7 @@ atomic_fetch_xor_acquire(int i, atomic_t *v)
static __always_inline int
atomic_fetch_xor_release(int i, atomic_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_fetch_xor_release(i, v);
}
@@ -444,6 +469,7 @@ atomic_fetch_xor_relaxed(int i, atomic_t *v)
static __always_inline int
atomic_xchg(atomic_t *v, int i)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_xchg(v, i);
}
@@ -458,6 +484,7 @@ atomic_xchg_acquire(atomic_t *v, int i)
static __always_inline int
atomic_xchg_release(atomic_t *v, int i)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_xchg_release(v, i);
}
@@ -472,6 +499,7 @@ atomic_xchg_relaxed(atomic_t *v, int i)
static __always_inline int
atomic_cmpxchg(atomic_t *v, int old, int new)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_cmpxchg(v, old, new);
}
@@ -486,6 +514,7 @@ atomic_cmpxchg_acquire(atomic_t *v, int old, int new)
static __always_inline int
atomic_cmpxchg_release(atomic_t *v, int old, int new)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_cmpxchg_release(v, old, new);
}
@@ -500,6 +529,7 @@ atomic_cmpxchg_relaxed(atomic_t *v, int old, int new)
static __always_inline bool
atomic_try_cmpxchg(atomic_t *v, int *old, int new)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
instrument_atomic_read_write(old, sizeof(*old));
return arch_atomic_try_cmpxchg(v, old, new);
@@ -516,6 +546,7 @@ atomic_try_cmpxchg_acquire(atomic_t *v, int *old, int new)
static __always_inline bool
atomic_try_cmpxchg_release(atomic_t *v, int *old, int new)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
instrument_atomic_read_write(old, sizeof(*old));
return arch_atomic_try_cmpxchg_release(v, old, new);
@@ -532,6 +563,7 @@ atomic_try_cmpxchg_relaxed(atomic_t *v, int *old, int new)
static __always_inline bool
atomic_sub_and_test(int i, atomic_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_sub_and_test(i, v);
}
@@ -539,6 +571,7 @@ atomic_sub_and_test(int i, atomic_t *v)
static __always_inline bool
atomic_dec_and_test(atomic_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_dec_and_test(v);
}
@@ -546,6 +579,7 @@ atomic_dec_and_test(atomic_t *v)
static __always_inline bool
atomic_inc_and_test(atomic_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_inc_and_test(v);
}
@@ -553,6 +587,7 @@ atomic_inc_and_test(atomic_t *v)
static __always_inline bool
atomic_add_negative(int i, atomic_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_add_negative(i, v);
}
@@ -560,6 +595,7 @@ atomic_add_negative(int i, atomic_t *v)
static __always_inline int
atomic_fetch_add_unless(atomic_t *v, int a, int u)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_fetch_add_unless(v, a, u);
}
@@ -567,6 +603,7 @@ atomic_fetch_add_unless(atomic_t *v, int a, int u)
static __always_inline bool
atomic_add_unless(atomic_t *v, int a, int u)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_add_unless(v, a, u);
}
@@ -574,6 +611,7 @@ atomic_add_unless(atomic_t *v, int a, int u)
static __always_inline bool
atomic_inc_not_zero(atomic_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_inc_not_zero(v);
}
@@ -581,6 +619,7 @@ atomic_inc_not_zero(atomic_t *v)
static __always_inline bool
atomic_inc_unless_negative(atomic_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_inc_unless_negative(v);
}
@@ -588,6 +627,7 @@ atomic_inc_unless_negative(atomic_t *v)
static __always_inline bool
atomic_dec_unless_positive(atomic_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_dec_unless_positive(v);
}
@@ -595,6 +635,7 @@ atomic_dec_unless_positive(atomic_t *v)
static __always_inline int
atomic_dec_if_positive(atomic_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_dec_if_positive(v);
}
@@ -623,6 +664,7 @@ atomic64_set(atomic64_t *v, s64 i)
static __always_inline void
atomic64_set_release(atomic64_t *v, s64 i)
{
+ kcsan_release();
instrument_atomic_write(v, sizeof(*v));
arch_atomic64_set_release(v, i);
}
@@ -637,6 +679,7 @@ atomic64_add(s64 i, atomic64_t *v)
static __always_inline s64
atomic64_add_return(s64 i, atomic64_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_add_return(i, v);
}
@@ -651,6 +694,7 @@ atomic64_add_return_acquire(s64 i, atomic64_t *v)
static __always_inline s64
atomic64_add_return_release(s64 i, atomic64_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_add_return_release(i, v);
}
@@ -665,6 +709,7 @@ atomic64_add_return_relaxed(s64 i, atomic64_t *v)
static __always_inline s64
atomic64_fetch_add(s64 i, atomic64_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_fetch_add(i, v);
}
@@ -679,6 +724,7 @@ atomic64_fetch_add_acquire(s64 i, atomic64_t *v)
static __always_inline s64
atomic64_fetch_add_release(s64 i, atomic64_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_fetch_add_release(i, v);
}
@@ -700,6 +746,7 @@ atomic64_sub(s64 i, atomic64_t *v)
static __always_inline s64
atomic64_sub_return(s64 i, atomic64_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_sub_return(i, v);
}
@@ -714,6 +761,7 @@ atomic64_sub_return_acquire(s64 i, atomic64_t *v)
static __always_inline s64
atomic64_sub_return_release(s64 i, atomic64_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_sub_return_release(i, v);
}
@@ -728,6 +776,7 @@ atomic64_sub_return_relaxed(s64 i, atomic64_t *v)
static __always_inline s64
atomic64_fetch_sub(s64 i, atomic64_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_fetch_sub(i, v);
}
@@ -742,6 +791,7 @@ atomic64_fetch_sub_acquire(s64 i, atomic64_t *v)
static __always_inline s64
atomic64_fetch_sub_release(s64 i, atomic64_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_fetch_sub_release(i, v);
}
@@ -763,6 +813,7 @@ atomic64_inc(atomic64_t *v)
static __always_inline s64
atomic64_inc_return(atomic64_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_inc_return(v);
}
@@ -777,6 +828,7 @@ atomic64_inc_return_acquire(atomic64_t *v)
static __always_inline s64
atomic64_inc_return_release(atomic64_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_inc_return_release(v);
}
@@ -791,6 +843,7 @@ atomic64_inc_return_relaxed(atomic64_t *v)
static __always_inline s64
atomic64_fetch_inc(atomic64_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_fetch_inc(v);
}
@@ -805,6 +858,7 @@ atomic64_fetch_inc_acquire(atomic64_t *v)
static __always_inline s64
atomic64_fetch_inc_release(atomic64_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_fetch_inc_release(v);
}
@@ -826,6 +880,7 @@ atomic64_dec(atomic64_t *v)
static __always_inline s64
atomic64_dec_return(atomic64_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_dec_return(v);
}
@@ -840,6 +895,7 @@ atomic64_dec_return_acquire(atomic64_t *v)
static __always_inline s64
atomic64_dec_return_release(atomic64_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_dec_return_release(v);
}
@@ -854,6 +910,7 @@ atomic64_dec_return_relaxed(atomic64_t *v)
static __always_inline s64
atomic64_fetch_dec(atomic64_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_fetch_dec(v);
}
@@ -868,6 +925,7 @@ atomic64_fetch_dec_acquire(atomic64_t *v)
static __always_inline s64
atomic64_fetch_dec_release(atomic64_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_fetch_dec_release(v);
}
@@ -889,6 +947,7 @@ atomic64_and(s64 i, atomic64_t *v)
static __always_inline s64
atomic64_fetch_and(s64 i, atomic64_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_fetch_and(i, v);
}
@@ -903,6 +962,7 @@ atomic64_fetch_and_acquire(s64 i, atomic64_t *v)
static __always_inline s64
atomic64_fetch_and_release(s64 i, atomic64_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_fetch_and_release(i, v);
}
@@ -924,6 +984,7 @@ atomic64_andnot(s64 i, atomic64_t *v)
static __always_inline s64
atomic64_fetch_andnot(s64 i, atomic64_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_fetch_andnot(i, v);
}
@@ -938,6 +999,7 @@ atomic64_fetch_andnot_acquire(s64 i, atomic64_t *v)
static __always_inline s64
atomic64_fetch_andnot_release(s64 i, atomic64_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_fetch_andnot_release(i, v);
}
@@ -959,6 +1021,7 @@ atomic64_or(s64 i, atomic64_t *v)
static __always_inline s64
atomic64_fetch_or(s64 i, atomic64_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_fetch_or(i, v);
}
@@ -973,6 +1036,7 @@ atomic64_fetch_or_acquire(s64 i, atomic64_t *v)
static __always_inline s64
atomic64_fetch_or_release(s64 i, atomic64_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_fetch_or_release(i, v);
}
@@ -994,6 +1058,7 @@ atomic64_xor(s64 i, atomic64_t *v)
static __always_inline s64
atomic64_fetch_xor(s64 i, atomic64_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_fetch_xor(i, v);
}
@@ -1008,6 +1073,7 @@ atomic64_fetch_xor_acquire(s64 i, atomic64_t *v)
static __always_inline s64
atomic64_fetch_xor_release(s64 i, atomic64_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_fetch_xor_release(i, v);
}
@@ -1022,6 +1088,7 @@ atomic64_fetch_xor_relaxed(s64 i, atomic64_t *v)
static __always_inline s64
atomic64_xchg(atomic64_t *v, s64 i)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_xchg(v, i);
}
@@ -1036,6 +1103,7 @@ atomic64_xchg_acquire(atomic64_t *v, s64 i)
static __always_inline s64
atomic64_xchg_release(atomic64_t *v, s64 i)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_xchg_release(v, i);
}
@@ -1050,6 +1118,7 @@ atomic64_xchg_relaxed(atomic64_t *v, s64 i)
static __always_inline s64
atomic64_cmpxchg(atomic64_t *v, s64 old, s64 new)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_cmpxchg(v, old, new);
}
@@ -1064,6 +1133,7 @@ atomic64_cmpxchg_acquire(atomic64_t *v, s64 old, s64 new)
static __always_inline s64
atomic64_cmpxchg_release(atomic64_t *v, s64 old, s64 new)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_cmpxchg_release(v, old, new);
}
@@ -1078,6 +1148,7 @@ atomic64_cmpxchg_relaxed(atomic64_t *v, s64 old, s64 new)
static __always_inline bool
atomic64_try_cmpxchg(atomic64_t *v, s64 *old, s64 new)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
instrument_atomic_read_write(old, sizeof(*old));
return arch_atomic64_try_cmpxchg(v, old, new);
@@ -1094,6 +1165,7 @@ atomic64_try_cmpxchg_acquire(atomic64_t *v, s64 *old, s64 new)
static __always_inline bool
atomic64_try_cmpxchg_release(atomic64_t *v, s64 *old, s64 new)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
instrument_atomic_read_write(old, sizeof(*old));
return arch_atomic64_try_cmpxchg_release(v, old, new);
@@ -1110,6 +1182,7 @@ atomic64_try_cmpxchg_relaxed(atomic64_t *v, s64 *old, s64 new)
static __always_inline bool
atomic64_sub_and_test(s64 i, atomic64_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_sub_and_test(i, v);
}
@@ -1117,6 +1190,7 @@ atomic64_sub_and_test(s64 i, atomic64_t *v)
static __always_inline bool
atomic64_dec_and_test(atomic64_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_dec_and_test(v);
}
@@ -1124,6 +1198,7 @@ atomic64_dec_and_test(atomic64_t *v)
static __always_inline bool
atomic64_inc_and_test(atomic64_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_inc_and_test(v);
}
@@ -1131,6 +1206,7 @@ atomic64_inc_and_test(atomic64_t *v)
static __always_inline bool
atomic64_add_negative(s64 i, atomic64_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_add_negative(i, v);
}
@@ -1138,6 +1214,7 @@ atomic64_add_negative(s64 i, atomic64_t *v)
static __always_inline s64
atomic64_fetch_add_unless(atomic64_t *v, s64 a, s64 u)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_fetch_add_unless(v, a, u);
}
@@ -1145,6 +1222,7 @@ atomic64_fetch_add_unless(atomic64_t *v, s64 a, s64 u)
static __always_inline bool
atomic64_add_unless(atomic64_t *v, s64 a, s64 u)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_add_unless(v, a, u);
}
@@ -1152,6 +1230,7 @@ atomic64_add_unless(atomic64_t *v, s64 a, s64 u)
static __always_inline bool
atomic64_inc_not_zero(atomic64_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_inc_not_zero(v);
}
@@ -1159,6 +1238,7 @@ atomic64_inc_not_zero(atomic64_t *v)
static __always_inline bool
atomic64_inc_unless_negative(atomic64_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_inc_unless_negative(v);
}
@@ -1166,6 +1246,7 @@ atomic64_inc_unless_negative(atomic64_t *v)
static __always_inline bool
atomic64_dec_unless_positive(atomic64_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_dec_unless_positive(v);
}
@@ -1173,6 +1254,7 @@ atomic64_dec_unless_positive(atomic64_t *v)
static __always_inline s64
atomic64_dec_if_positive(atomic64_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic64_dec_if_positive(v);
}
@@ -1201,6 +1283,7 @@ atomic_long_set(atomic_long_t *v, long i)
static __always_inline void
atomic_long_set_release(atomic_long_t *v, long i)
{
+ kcsan_release();
instrument_atomic_write(v, sizeof(*v));
arch_atomic_long_set_release(v, i);
}
@@ -1215,6 +1298,7 @@ atomic_long_add(long i, atomic_long_t *v)
static __always_inline long
atomic_long_add_return(long i, atomic_long_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_add_return(i, v);
}
@@ -1229,6 +1313,7 @@ atomic_long_add_return_acquire(long i, atomic_long_t *v)
static __always_inline long
atomic_long_add_return_release(long i, atomic_long_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_add_return_release(i, v);
}
@@ -1243,6 +1328,7 @@ atomic_long_add_return_relaxed(long i, atomic_long_t *v)
static __always_inline long
atomic_long_fetch_add(long i, atomic_long_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_fetch_add(i, v);
}
@@ -1257,6 +1343,7 @@ atomic_long_fetch_add_acquire(long i, atomic_long_t *v)
static __always_inline long
atomic_long_fetch_add_release(long i, atomic_long_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_fetch_add_release(i, v);
}
@@ -1278,6 +1365,7 @@ atomic_long_sub(long i, atomic_long_t *v)
static __always_inline long
atomic_long_sub_return(long i, atomic_long_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_sub_return(i, v);
}
@@ -1292,6 +1380,7 @@ atomic_long_sub_return_acquire(long i, atomic_long_t *v)
static __always_inline long
atomic_long_sub_return_release(long i, atomic_long_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_sub_return_release(i, v);
}
@@ -1306,6 +1395,7 @@ atomic_long_sub_return_relaxed(long i, atomic_long_t *v)
static __always_inline long
atomic_long_fetch_sub(long i, atomic_long_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_fetch_sub(i, v);
}
@@ -1320,6 +1410,7 @@ atomic_long_fetch_sub_acquire(long i, atomic_long_t *v)
static __always_inline long
atomic_long_fetch_sub_release(long i, atomic_long_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_fetch_sub_release(i, v);
}
@@ -1341,6 +1432,7 @@ atomic_long_inc(atomic_long_t *v)
static __always_inline long
atomic_long_inc_return(atomic_long_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_inc_return(v);
}
@@ -1355,6 +1447,7 @@ atomic_long_inc_return_acquire(atomic_long_t *v)
static __always_inline long
atomic_long_inc_return_release(atomic_long_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_inc_return_release(v);
}
@@ -1369,6 +1462,7 @@ atomic_long_inc_return_relaxed(atomic_long_t *v)
static __always_inline long
atomic_long_fetch_inc(atomic_long_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_fetch_inc(v);
}
@@ -1383,6 +1477,7 @@ atomic_long_fetch_inc_acquire(atomic_long_t *v)
static __always_inline long
atomic_long_fetch_inc_release(atomic_long_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_fetch_inc_release(v);
}
@@ -1404,6 +1499,7 @@ atomic_long_dec(atomic_long_t *v)
static __always_inline long
atomic_long_dec_return(atomic_long_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_dec_return(v);
}
@@ -1418,6 +1514,7 @@ atomic_long_dec_return_acquire(atomic_long_t *v)
static __always_inline long
atomic_long_dec_return_release(atomic_long_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_dec_return_release(v);
}
@@ -1432,6 +1529,7 @@ atomic_long_dec_return_relaxed(atomic_long_t *v)
static __always_inline long
atomic_long_fetch_dec(atomic_long_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_fetch_dec(v);
}
@@ -1446,6 +1544,7 @@ atomic_long_fetch_dec_acquire(atomic_long_t *v)
static __always_inline long
atomic_long_fetch_dec_release(atomic_long_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_fetch_dec_release(v);
}
@@ -1467,6 +1566,7 @@ atomic_long_and(long i, atomic_long_t *v)
static __always_inline long
atomic_long_fetch_and(long i, atomic_long_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_fetch_and(i, v);
}
@@ -1481,6 +1581,7 @@ atomic_long_fetch_and_acquire(long i, atomic_long_t *v)
static __always_inline long
atomic_long_fetch_and_release(long i, atomic_long_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_fetch_and_release(i, v);
}
@@ -1502,6 +1603,7 @@ atomic_long_andnot(long i, atomic_long_t *v)
static __always_inline long
atomic_long_fetch_andnot(long i, atomic_long_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_fetch_andnot(i, v);
}
@@ -1516,6 +1618,7 @@ atomic_long_fetch_andnot_acquire(long i, atomic_long_t *v)
static __always_inline long
atomic_long_fetch_andnot_release(long i, atomic_long_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_fetch_andnot_release(i, v);
}
@@ -1537,6 +1640,7 @@ atomic_long_or(long i, atomic_long_t *v)
static __always_inline long
atomic_long_fetch_or(long i, atomic_long_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_fetch_or(i, v);
}
@@ -1551,6 +1655,7 @@ atomic_long_fetch_or_acquire(long i, atomic_long_t *v)
static __always_inline long
atomic_long_fetch_or_release(long i, atomic_long_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_fetch_or_release(i, v);
}
@@ -1572,6 +1677,7 @@ atomic_long_xor(long i, atomic_long_t *v)
static __always_inline long
atomic_long_fetch_xor(long i, atomic_long_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_fetch_xor(i, v);
}
@@ -1586,6 +1692,7 @@ atomic_long_fetch_xor_acquire(long i, atomic_long_t *v)
static __always_inline long
atomic_long_fetch_xor_release(long i, atomic_long_t *v)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_fetch_xor_release(i, v);
}
@@ -1600,6 +1707,7 @@ atomic_long_fetch_xor_relaxed(long i, atomic_long_t *v)
static __always_inline long
atomic_long_xchg(atomic_long_t *v, long i)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_xchg(v, i);
}
@@ -1614,6 +1722,7 @@ atomic_long_xchg_acquire(atomic_long_t *v, long i)
static __always_inline long
atomic_long_xchg_release(atomic_long_t *v, long i)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_xchg_release(v, i);
}
@@ -1628,6 +1737,7 @@ atomic_long_xchg_relaxed(atomic_long_t *v, long i)
static __always_inline long
atomic_long_cmpxchg(atomic_long_t *v, long old, long new)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_cmpxchg(v, old, new);
}
@@ -1642,6 +1752,7 @@ atomic_long_cmpxchg_acquire(atomic_long_t *v, long old, long new)
static __always_inline long
atomic_long_cmpxchg_release(atomic_long_t *v, long old, long new)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_cmpxchg_release(v, old, new);
}
@@ -1656,6 +1767,7 @@ atomic_long_cmpxchg_relaxed(atomic_long_t *v, long old, long new)
static __always_inline bool
atomic_long_try_cmpxchg(atomic_long_t *v, long *old, long new)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
instrument_atomic_read_write(old, sizeof(*old));
return arch_atomic_long_try_cmpxchg(v, old, new);
@@ -1672,6 +1784,7 @@ atomic_long_try_cmpxchg_acquire(atomic_long_t *v, long *old, long new)
static __always_inline bool
atomic_long_try_cmpxchg_release(atomic_long_t *v, long *old, long new)
{
+ kcsan_release();
instrument_atomic_read_write(v, sizeof(*v));
instrument_atomic_read_write(old, sizeof(*old));
return arch_atomic_long_try_cmpxchg_release(v, old, new);
@@ -1688,6 +1801,7 @@ atomic_long_try_cmpxchg_relaxed(atomic_long_t *v, long *old, long new)
static __always_inline bool
atomic_long_sub_and_test(long i, atomic_long_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_sub_and_test(i, v);
}
@@ -1695,6 +1809,7 @@ atomic_long_sub_and_test(long i, atomic_long_t *v)
static __always_inline bool
atomic_long_dec_and_test(atomic_long_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_dec_and_test(v);
}
@@ -1702,6 +1817,7 @@ atomic_long_dec_and_test(atomic_long_t *v)
static __always_inline bool
atomic_long_inc_and_test(atomic_long_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_inc_and_test(v);
}
@@ -1709,6 +1825,7 @@ atomic_long_inc_and_test(atomic_long_t *v)
static __always_inline bool
atomic_long_add_negative(long i, atomic_long_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_add_negative(i, v);
}
@@ -1716,6 +1833,7 @@ atomic_long_add_negative(long i, atomic_long_t *v)
static __always_inline long
atomic_long_fetch_add_unless(atomic_long_t *v, long a, long u)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_fetch_add_unless(v, a, u);
}
@@ -1723,6 +1841,7 @@ atomic_long_fetch_add_unless(atomic_long_t *v, long a, long u)
static __always_inline bool
atomic_long_add_unless(atomic_long_t *v, long a, long u)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_add_unless(v, a, u);
}
@@ -1730,6 +1849,7 @@ atomic_long_add_unless(atomic_long_t *v, long a, long u)
static __always_inline bool
atomic_long_inc_not_zero(atomic_long_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_inc_not_zero(v);
}
@@ -1737,6 +1857,7 @@ atomic_long_inc_not_zero(atomic_long_t *v)
static __always_inline bool
atomic_long_inc_unless_negative(atomic_long_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_inc_unless_negative(v);
}
@@ -1744,6 +1865,7 @@ atomic_long_inc_unless_negative(atomic_long_t *v)
static __always_inline bool
atomic_long_dec_unless_positive(atomic_long_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_dec_unless_positive(v);
}
@@ -1751,6 +1873,7 @@ atomic_long_dec_unless_positive(atomic_long_t *v)
static __always_inline long
atomic_long_dec_if_positive(atomic_long_t *v)
{
+ kcsan_mb();
instrument_atomic_read_write(v, sizeof(*v));
return arch_atomic_long_dec_if_positive(v);
}
@@ -1758,6 +1881,7 @@ atomic_long_dec_if_positive(atomic_long_t *v)
#define xchg(ptr, ...) \
({ \
typeof(ptr) __ai_ptr = (ptr); \
+ kcsan_mb(); \
instrument_atomic_write(__ai_ptr, sizeof(*__ai_ptr)); \
arch_xchg(__ai_ptr, __VA_ARGS__); \
})
@@ -1772,6 +1896,7 @@ atomic_long_dec_if_positive(atomic_long_t *v)
#define xchg_release(ptr, ...) \
({ \
typeof(ptr) __ai_ptr = (ptr); \
+ kcsan_release(); \
instrument_atomic_write(__ai_ptr, sizeof(*__ai_ptr)); \
arch_xchg_release(__ai_ptr, __VA_ARGS__); \
})
@@ -1786,6 +1911,7 @@ atomic_long_dec_if_positive(atomic_long_t *v)
#define cmpxchg(ptr, ...) \
({ \
typeof(ptr) __ai_ptr = (ptr); \
+ kcsan_mb(); \
instrument_atomic_write(__ai_ptr, sizeof(*__ai_ptr)); \
arch_cmpxchg(__ai_ptr, __VA_ARGS__); \
})
@@ -1800,6 +1926,7 @@ atomic_long_dec_if_positive(atomic_long_t *v)
#define cmpxchg_release(ptr, ...) \
({ \
typeof(ptr) __ai_ptr = (ptr); \
+ kcsan_release(); \
instrument_atomic_write(__ai_ptr, sizeof(*__ai_ptr)); \
arch_cmpxchg_release(__ai_ptr, __VA_ARGS__); \
})
@@ -1814,6 +1941,7 @@ atomic_long_dec_if_positive(atomic_long_t *v)
#define cmpxchg64(ptr, ...) \
({ \
typeof(ptr) __ai_ptr = (ptr); \
+ kcsan_mb(); \
instrument_atomic_write(__ai_ptr, sizeof(*__ai_ptr)); \
arch_cmpxchg64(__ai_ptr, __VA_ARGS__); \
})
@@ -1828,6 +1956,7 @@ atomic_long_dec_if_positive(atomic_long_t *v)
#define cmpxchg64_release(ptr, ...) \
({ \
typeof(ptr) __ai_ptr = (ptr); \
+ kcsan_release(); \
instrument_atomic_write(__ai_ptr, sizeof(*__ai_ptr)); \
arch_cmpxchg64_release(__ai_ptr, __VA_ARGS__); \
})
@@ -1843,6 +1972,7 @@ atomic_long_dec_if_positive(atomic_long_t *v)
({ \
typeof(ptr) __ai_ptr = (ptr); \
typeof(oldp) __ai_oldp = (oldp); \
+ kcsan_mb(); \
instrument_atomic_write(__ai_ptr, sizeof(*__ai_ptr)); \
instrument_atomic_write(__ai_oldp, sizeof(*__ai_oldp)); \
arch_try_cmpxchg(__ai_ptr, __ai_oldp, __VA_ARGS__); \
@@ -1861,6 +1991,7 @@ atomic_long_dec_if_positive(atomic_long_t *v)
({ \
typeof(ptr) __ai_ptr = (ptr); \
typeof(oldp) __ai_oldp = (oldp); \
+ kcsan_release(); \
instrument_atomic_write(__ai_ptr, sizeof(*__ai_ptr)); \
instrument_atomic_write(__ai_oldp, sizeof(*__ai_oldp)); \
arch_try_cmpxchg_release(__ai_ptr, __ai_oldp, __VA_ARGS__); \
@@ -1892,6 +2023,7 @@ atomic_long_dec_if_positive(atomic_long_t *v)
#define sync_cmpxchg(ptr, ...) \
({ \
typeof(ptr) __ai_ptr = (ptr); \
+ kcsan_mb(); \
instrument_atomic_write(__ai_ptr, sizeof(*__ai_ptr)); \
arch_sync_cmpxchg(__ai_ptr, __VA_ARGS__); \
})
@@ -1899,6 +2031,7 @@ atomic_long_dec_if_positive(atomic_long_t *v)
#define cmpxchg_double(ptr, ...) \
({ \
typeof(ptr) __ai_ptr = (ptr); \
+ kcsan_mb(); \
instrument_atomic_write(__ai_ptr, 2 * sizeof(*__ai_ptr)); \
arch_cmpxchg_double(__ai_ptr, __VA_ARGS__); \
})
@@ -1912,4 +2045,4 @@ atomic_long_dec_if_positive(atomic_long_t *v)
})
#endif /* _LINUX_ATOMIC_INSTRUMENTED_H */
-// 2a9553f0a9d5619f19151092df5cabbbf16ce835
+// 87c974b93032afd42143613434d1a7788fa598f9
diff --git a/scripts/atomic/gen-atomic-instrumented.sh b/scripts/atomic/gen-atomic-instrumented.sh
index 035ceb4ee85c9..68f902731d018 100755
--- a/scripts/atomic/gen-atomic-instrumented.sh
+++ b/scripts/atomic/gen-atomic-instrumented.sh
@@ -34,6 +34,14 @@ gen_param_check()
gen_params_checks()
{
local meta="$1"; shift
+ local order="$1"; shift
+
+ if [ "${order}" = "_release" ]; then
+ printf "\tkcsan_release();\n"
+ elif [ -z "${order}" ] && ! meta_in "$meta" "slv"; then
+ # RMW with return value is fully ordered
+ printf "\tkcsan_mb();\n"
+ fi
while [ "$#" -gt 0 ]; do
gen_param_check "$meta" "$1"
@@ -56,7 +64,7 @@ gen_proto_order_variant()
local ret="$(gen_ret_type "${meta}" "${int}")"
local params="$(gen_params "${int}" "${atomic}" "$@")"
- local checks="$(gen_params_checks "${meta}" "$@")"
+ local checks="$(gen_params_checks "${meta}" "${order}" "$@")"
local args="$(gen_args "$@")"
local retstmt="$(gen_ret_stmt "${meta}")"
@@ -75,29 +83,44 @@ EOF
gen_xchg()
{
local xchg="$1"; shift
+ local order="$1"; shift
local mult="$1"; shift
+ kcsan_barrier=""
+ if [ "${xchg%_local}" = "${xchg}" ]; then
+ case "$order" in
+ _release) kcsan_barrier="kcsan_release()" ;;
+ "") kcsan_barrier="kcsan_mb()" ;;
+ esac
+ fi
+
if [ "${xchg%${xchg#try_cmpxchg}}" = "try_cmpxchg" ] ; then
cat <<EOF
-#define ${xchg}(ptr, oldp, ...) \\
+#define ${xchg}${order}(ptr, oldp, ...) \\
({ \\
typeof(ptr) __ai_ptr = (ptr); \\
typeof(oldp) __ai_oldp = (oldp); \\
+EOF
+[ -n "$kcsan_barrier" ] && printf "\t${kcsan_barrier}; \\\\\n"
+cat <<EOF
instrument_atomic_write(__ai_ptr, ${mult}sizeof(*__ai_ptr)); \\
instrument_atomic_write(__ai_oldp, ${mult}sizeof(*__ai_oldp)); \\
- arch_${xchg}(__ai_ptr, __ai_oldp, __VA_ARGS__); \\
+ arch_${xchg}${order}(__ai_ptr, __ai_oldp, __VA_ARGS__); \\
})
EOF
else
cat <<EOF
-#define ${xchg}(ptr, ...) \\
+#define ${xchg}${order}(ptr, ...) \\
({ \\
typeof(ptr) __ai_ptr = (ptr); \\
+EOF
+[ -n "$kcsan_barrier" ] && printf "\t${kcsan_barrier}; \\\\\n"
+cat <<EOF
instrument_atomic_write(__ai_ptr, ${mult}sizeof(*__ai_ptr)); \\
- arch_${xchg}(__ai_ptr, __VA_ARGS__); \\
+ arch_${xchg}${order}(__ai_ptr, __VA_ARGS__); \\
})
EOF
@@ -145,21 +168,21 @@ done
for xchg in "xchg" "cmpxchg" "cmpxchg64" "try_cmpxchg"; do
for order in "" "_acquire" "_release" "_relaxed"; do
- gen_xchg "${xchg}${order}" ""
+ gen_xchg "${xchg}" "${order}" ""
printf "\n"
done
done
for xchg in "cmpxchg_local" "cmpxchg64_local" "sync_cmpxchg"; do
- gen_xchg "${xchg}" ""
+ gen_xchg "${xchg}" "" ""
printf "\n"
done
-gen_xchg "cmpxchg_double" "2 * "
+gen_xchg "cmpxchg_double" "" "2 * "
printf "\n\n"
-gen_xchg "cmpxchg_double_local" "2 * "
+gen_xchg "cmpxchg_double_local" "" "2 * "
cat <<EOF
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 17/29] asm-generic/bitops, kcsan: Add instrumentation for barriers
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (15 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 16/29] locking/atomics, kcsan: Add instrumentation for barriers Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 18/29] x86/barriers, kcsan: Use generic instrumentation for non-smp barriers Paul E. McKenney
` (11 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
Adds the required KCSAN instrumentation for barriers of atomic bitops.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
include/asm-generic/bitops/instrumented-atomic.h | 3 +++
include/asm-generic/bitops/instrumented-lock.h | 3 +++
2 files changed, 6 insertions(+)
diff --git a/include/asm-generic/bitops/instrumented-atomic.h b/include/asm-generic/bitops/instrumented-atomic.h
index 81915dcd4b4e8..c90192b1c7552 100644
--- a/include/asm-generic/bitops/instrumented-atomic.h
+++ b/include/asm-generic/bitops/instrumented-atomic.h
@@ -67,6 +67,7 @@ static inline void change_bit(long nr, volatile unsigned long *addr)
*/
static inline bool test_and_set_bit(long nr, volatile unsigned long *addr)
{
+ kcsan_mb();
instrument_atomic_read_write(addr + BIT_WORD(nr), sizeof(long));
return arch_test_and_set_bit(nr, addr);
}
@@ -80,6 +81,7 @@ static inline bool test_and_set_bit(long nr, volatile unsigned long *addr)
*/
static inline bool test_and_clear_bit(long nr, volatile unsigned long *addr)
{
+ kcsan_mb();
instrument_atomic_read_write(addr + BIT_WORD(nr), sizeof(long));
return arch_test_and_clear_bit(nr, addr);
}
@@ -93,6 +95,7 @@ static inline bool test_and_clear_bit(long nr, volatile unsigned long *addr)
*/
static inline bool test_and_change_bit(long nr, volatile unsigned long *addr)
{
+ kcsan_mb();
instrument_atomic_read_write(addr + BIT_WORD(nr), sizeof(long));
return arch_test_and_change_bit(nr, addr);
}
diff --git a/include/asm-generic/bitops/instrumented-lock.h b/include/asm-generic/bitops/instrumented-lock.h
index 75ef606f71452..eb64bd4f11f3c 100644
--- a/include/asm-generic/bitops/instrumented-lock.h
+++ b/include/asm-generic/bitops/instrumented-lock.h
@@ -22,6 +22,7 @@
*/
static inline void clear_bit_unlock(long nr, volatile unsigned long *addr)
{
+ kcsan_release();
instrument_atomic_write(addr + BIT_WORD(nr), sizeof(long));
arch_clear_bit_unlock(nr, addr);
}
@@ -37,6 +38,7 @@ static inline void clear_bit_unlock(long nr, volatile unsigned long *addr)
*/
static inline void __clear_bit_unlock(long nr, volatile unsigned long *addr)
{
+ kcsan_release();
instrument_write(addr + BIT_WORD(nr), sizeof(long));
arch___clear_bit_unlock(nr, addr);
}
@@ -71,6 +73,7 @@ static inline bool test_and_set_bit_lock(long nr, volatile unsigned long *addr)
static inline bool
clear_bit_unlock_is_negative_byte(long nr, volatile unsigned long *addr)
{
+ kcsan_release();
instrument_atomic_write(addr + BIT_WORD(nr), sizeof(long));
return arch_clear_bit_unlock_is_negative_byte(nr, addr);
}
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 18/29] x86/barriers, kcsan: Use generic instrumentation for non-smp barriers
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (16 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 17/29] asm-generic/bitops, " Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 19/29] x86/qspinlock, kcsan: Instrument barrier of pv_queued_spin_unlock() Paul E. McKenney
` (10 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
Prefix all barriers with __, now that asm-generic/barriers.h supports
defining the final instrumented version of these barriers. The change is
limited to barriers used by x86-64.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
arch/x86/include/asm/barrier.h | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h
index 3ba772a69cc8b..35389b2af88ee 100644
--- a/arch/x86/include/asm/barrier.h
+++ b/arch/x86/include/asm/barrier.h
@@ -19,9 +19,9 @@
#define wmb() asm volatile(ALTERNATIVE("lock; addl $0,-4(%%esp)", "sfence", \
X86_FEATURE_XMM2) ::: "memory", "cc")
#else
-#define mb() asm volatile("mfence":::"memory")
-#define rmb() asm volatile("lfence":::"memory")
-#define wmb() asm volatile("sfence" ::: "memory")
+#define __mb() asm volatile("mfence":::"memory")
+#define __rmb() asm volatile("lfence":::"memory")
+#define __wmb() asm volatile("sfence" ::: "memory")
#endif
/**
@@ -51,8 +51,8 @@ static inline unsigned long array_index_mask_nospec(unsigned long index,
/* Prevent speculative execution past this barrier. */
#define barrier_nospec() alternative("", "lfence", X86_FEATURE_LFENCE_RDTSC)
-#define dma_rmb() barrier()
-#define dma_wmb() barrier()
+#define __dma_rmb() barrier()
+#define __dma_wmb() barrier()
#define __smp_mb() asm volatile("lock; addl $0,-4(%%" _ASM_SP ")" ::: "memory", "cc")
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 19/29] x86/qspinlock, kcsan: Instrument barrier of pv_queued_spin_unlock()
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (17 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 18/29] x86/barriers, kcsan: Use generic instrumentation for non-smp barriers Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 20/29] mm, kcsan: Enable barrier instrumentation Paul E. McKenney
` (9 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
If CONFIG_PARAVIRT_SPINLOCKS=y, queued_spin_unlock() is implemented
using pv_queued_spin_unlock() which is entirely inline asm based. As
such, we do not receive any KCSAN barrier instrumentation via regular
atomic operations.
Add the missing KCSAN barrier instrumentation for the
CONFIG_PARAVIRT_SPINLOCKS case.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
arch/x86/include/asm/qspinlock.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h
index d86ab942219c4..d87451df480bd 100644
--- a/arch/x86/include/asm/qspinlock.h
+++ b/arch/x86/include/asm/qspinlock.h
@@ -53,6 +53,7 @@ static inline void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
static inline void queued_spin_unlock(struct qspinlock *lock)
{
+ kcsan_release();
pv_queued_spin_unlock(lock);
}
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 20/29] mm, kcsan: Enable barrier instrumentation
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (18 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 19/29] x86/qspinlock, kcsan: Instrument barrier of pv_queued_spin_unlock() Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 21/29] sched, kcsan: Enable memory " Paul E. McKenney
` (8 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
Some memory management calls imply memory barriers that are required to
avoid false positives. For example, without the correct instrumentation,
we could observe data races of the following variant:
T0 | T1
------------------------+------------------------
|
*a = 42; ---+ |
kfree(a); | |
| | b = kmalloc(..); // b == a
<reordered> <-+ | *b = 42; // not a data race!
|
Therefore, instrument memory barriers in all allocator code currently
not being instrumented in a default build.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
mm/Makefile | 2 ++
1 file changed, 2 insertions(+)
diff --git a/mm/Makefile b/mm/Makefile
index d6c0042e3aa0d..7919cd7f13f2a 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -15,6 +15,8 @@ KCSAN_SANITIZE_slab_common.o := n
KCSAN_SANITIZE_slab.o := n
KCSAN_SANITIZE_slub.o := n
KCSAN_SANITIZE_page_alloc.o := n
+# But enable explicit instrumentation for memory barriers.
+KCSAN_INSTRUMENT_BARRIERS := y
# These files are disabled because they produce non-interesting and/or
# flaky coverage that is not a function of syscall inputs. E.g. slab is out of
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 21/29] sched, kcsan: Enable memory barrier instrumentation
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (19 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 20/29] mm, kcsan: Enable barrier instrumentation Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 22/29] objtool, kcsan: Add memory barrier instrumentation to whitelist Paul E. McKenney
` (7 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
There's no fundamental reason to disable KCSAN for scheduler code,
except for excessive noise and performance concerns (instrumenting
scheduler code is usually a good way to stress test KCSAN itself).
However, several core sched functions imply memory barriers that are
invisible to KCSAN without instrumentation, but are required to avoid
false positives. Therefore, unconditionally enable instrumentation of
memory barriers in scheduler code. Also update the comment to reflect
this and be a bit more brief.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/sched/Makefile | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile
index c7421f2d05e15..c83b37af155b1 100644
--- a/kernel/sched/Makefile
+++ b/kernel/sched/Makefile
@@ -11,11 +11,10 @@ ccflags-y += $(call cc-disable-warning, unused-but-set-variable)
# that is not a function of syscall inputs. E.g. involuntary context switches.
KCOV_INSTRUMENT := n
-# There are numerous data races here, however, most of them are due to plain accesses.
-# This would make it even harder for syzbot to find reproducers, because these
-# bugs trigger without specific input. Disable by default, but should re-enable
-# eventually.
+# Disable KCSAN to avoid excessive noise and performance degradation. To avoid
+# false positives ensure barriers implied by sched functions are instrumented.
KCSAN_SANITIZE := n
+KCSAN_INSTRUMENT_BARRIERS := y
ifneq ($(CONFIG_SCHED_OMIT_FRAME_POINTER),y)
# According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 22/29] objtool, kcsan: Add memory barrier instrumentation to whitelist
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (20 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 21/29] sched, kcsan: Enable memory " Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 23/29] objtool, kcsan: Remove memory barrier instrumentation from noinstr Paul E. McKenney
` (6 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
Adds KCSAN's memory barrier instrumentation to objtool's uaccess
whitelist.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
tools/objtool/check.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 21735829b860c..61dfb66b30b64 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -849,6 +849,10 @@ static const char *uaccess_safe_builtin[] = {
"__asan_report_store16_noabort",
/* KCSAN */
"__kcsan_check_access",
+ "__kcsan_mb",
+ "__kcsan_wmb",
+ "__kcsan_rmb",
+ "__kcsan_release",
"kcsan_found_watchpoint",
"kcsan_setup_watchpoint",
"kcsan_check_scoped_accesses",
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 23/29] objtool, kcsan: Remove memory barrier instrumentation from noinstr
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (21 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 22/29] objtool, kcsan: Add memory barrier instrumentation to whitelist Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 24/29] compiler_attributes.h: Add __disable_sanitizer_instrumentation Paul E. McKenney
` (5 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng,
Josh Poimboeuf, Paul E . McKenney
From: Marco Elver <elver@google.com>
Teach objtool to turn instrumentation required for memory barrier
modeling into nops in noinstr text.
The __tsan_func_entry/exit calls are still emitted by compilers even
with the __no_sanitize_thread attribute. The memory barrier
instrumentation will be inserted explicitly (without compiler help), and
thus needs to also explicitly be removed.
Signed-off-by: Marco Elver <elver@google.com>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
tools/objtool/check.c | 37 ++++++++++++++++++++++++-----
tools/objtool/include/objtool/elf.h | 2 +-
2 files changed, 32 insertions(+), 7 deletions(-)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 61dfb66b30b64..a9a1f7259d628 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1072,11 +1072,11 @@ static void annotate_call_site(struct objtool_file *file,
}
/*
- * Many compilers cannot disable KCOV with a function attribute
- * so they need a little help, NOP out any KCOV calls from noinstr
- * text.
+ * Many compilers cannot disable KCOV or sanitizer calls with a function
+ * attribute so they need a little help, NOP out any such calls from
+ * noinstr text.
*/
- if (insn->sec->noinstr && sym->kcov) {
+ if (insn->sec->noinstr && sym->profiling_func) {
if (reloc) {
reloc->type = R_NONE;
elf_write_reloc(file->elf, reloc);
@@ -1991,6 +1991,31 @@ static int read_intra_function_calls(struct objtool_file *file)
return 0;
}
+/*
+ * Return true if name matches an instrumentation function, where calls to that
+ * function from noinstr code can safely be removed, but compilers won't do so.
+ */
+static bool is_profiling_func(const char *name)
+{
+ /*
+ * Many compilers cannot disable KCOV with a function attribute.
+ */
+ if (!strncmp(name, "__sanitizer_cov_", 16))
+ return true;
+
+ /*
+ * Some compilers currently do not remove __tsan_func_entry/exit nor
+ * __tsan_atomic_signal_fence (used for barrier instrumentation) with
+ * the __no_sanitize_thread attribute, remove them. Once the kernel's
+ * minimum Clang version is 14.0, this can be removed.
+ */
+ if (!strncmp(name, "__tsan_func_", 12) ||
+ !strcmp(name, "__tsan_atomic_signal_fence"))
+ return true;
+
+ return false;
+}
+
static int classify_symbols(struct objtool_file *file)
{
struct section *sec;
@@ -2011,8 +2036,8 @@ static int classify_symbols(struct objtool_file *file)
if (!strcmp(func->name, "__fentry__"))
func->fentry = true;
- if (!strncmp(func->name, "__sanitizer_cov_", 16))
- func->kcov = true;
+ if (is_profiling_func(func->name))
+ func->profiling_func = true;
}
}
diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index cdc739fa9a6fb..d223367814017 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -58,7 +58,7 @@ struct symbol {
u8 static_call_tramp : 1;
u8 retpoline_thunk : 1;
u8 fentry : 1;
- u8 kcov : 1;
+ u8 profiling_func : 1;
struct list_head pv_target;
};
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 24/29] compiler_attributes.h: Add __disable_sanitizer_instrumentation
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (22 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 23/29] objtool, kcsan: Remove memory barrier instrumentation from noinstr Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 25/29] kcsan: Support WEAK_MEMORY with Clang where no objtool support exists Paul E. McKenney
` (4 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Alexander Potapenko <glider@google.com>
The new attribute maps to
__attribute__((disable_sanitizer_instrumentation)), which will be
supported by Clang >= 14.0. Future support in GCC is also possible.
This attribute disables compiler instrumentation for kernel sanitizer
tools, making it easier to implement noinstr. It is different from the
existing __no_sanitize* attributes, which may still allow certain types
of instrumentation to prevent false positives.
Signed-off-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
include/linux/compiler_attributes.h | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h
index b9121afd87331..37e2600202216 100644
--- a/include/linux/compiler_attributes.h
+++ b/include/linux/compiler_attributes.h
@@ -308,6 +308,24 @@
# define __compiletime_warning(msg)
#endif
+/*
+ * Optional: only supported since clang >= 14.0
+ *
+ * clang: https://clang.llvm.org/docs/AttributeReference.html#disable-sanitizer-instrumentation
+ *
+ * disable_sanitizer_instrumentation is not always similar to
+ * no_sanitize((<sanitizer-name>)): the latter may still let specific sanitizers
+ * insert code into functions to prevent false positives. Unlike that,
+ * disable_sanitizer_instrumentation prevents all kinds of instrumentation to
+ * functions with the attribute.
+ */
+#if __has_attribute(disable_sanitizer_instrumentation)
+# define __disable_sanitizer_instrumentation \
+ __attribute__((disable_sanitizer_instrumentation))
+#else
+# define __disable_sanitizer_instrumentation
+#endif
+
/*
* gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
* gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 25/29] kcsan: Support WEAK_MEMORY with Clang where no objtool support exists
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (23 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 24/29] compiler_attributes.h: Add __disable_sanitizer_instrumentation Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 26/29] kcsan: Make barrier tests compatible with lockdep Paul E. McKenney
` (3 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
Clang and GCC behave a little differently when it comes to the
__no_sanitize_thread attribute, which has valid reasons, and depending
on context either one could be right.
Traditionally, user space ThreadSanitizer [1] still expects instrumented
builtin atomics (to avoid false positives) and __tsan_func_{entry,exit}
(to generate meaningful stack traces), even if the function has the
attribute no_sanitize("thread").
[1] https://clang.llvm.org/docs/ThreadSanitizer.html#attribute-no-sanitize-thread
GCC doesn't follow the same policy (for better or worse), and removes
all kinds of instrumentation if no_sanitize is added. Arguably, since
this may be a problem for user space ThreadSanitizer, we expect this may
change in future.
Since KCSAN != ThreadSanitizer, the likelihood of false positives even
without barrier instrumentation everywhere, is much lower by design.
At least for Clang, however, to fully remove all sanitizer
instrumentation, we must add the disable_sanitizer_instrumentation
attribute, which is available since Clang 14.0.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
include/linux/compiler_types.h | 13 ++++++++++++-
lib/Kconfig.kcsan | 2 +-
2 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 1d32f4c03c9ef..3c1795fdb5686 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -198,9 +198,20 @@ struct ftrace_likely_data {
# define __no_kasan_or_inline __always_inline
#endif
-#define __no_kcsan __no_sanitize_thread
#ifdef __SANITIZE_THREAD__
+/*
+ * Clang still emits instrumentation for __tsan_func_{entry,exit}() and builtin
+ * atomics even with __no_sanitize_thread (to avoid false positives in userspace
+ * ThreadSanitizer). The kernel's requirements are stricter and we really do not
+ * want any instrumentation with __no_kcsan.
+ *
+ * Therefore we add __disable_sanitizer_instrumentation where available to
+ * disable all instrumentation. See Kconfig.kcsan where this is mandatory.
+ */
+# define __no_kcsan __no_sanitize_thread __disable_sanitizer_instrumentation
# define __no_sanitize_or_inline __no_kcsan notrace __maybe_unused
+#else
+# define __no_kcsan
#endif
#ifndef __no_sanitize_or_inline
diff --git a/lib/Kconfig.kcsan b/lib/Kconfig.kcsan
index e4394ea8068b0..63b70b8c55519 100644
--- a/lib/Kconfig.kcsan
+++ b/lib/Kconfig.kcsan
@@ -198,7 +198,7 @@ config KCSAN_WEAK_MEMORY
# We can either let objtool nop __tsan_func_{entry,exit}() and builtin
# atomics instrumentation in .noinstr.text, or use a compiler that can
# implement __no_kcsan to really remove all instrumentation.
- depends on STACK_VALIDATION || CC_IS_GCC
+ depends on STACK_VALIDATION || CC_IS_GCC || CLANG_VERSION >= 140000
help
Enable support for modeling a subset of weak memory, which allows
detecting a subset of data races due to missing memory barriers.
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 26/29] kcsan: Make barrier tests compatible with lockdep
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (24 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 25/29] kcsan: Support WEAK_MEMORY with Clang where no objtool support exists Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 27/29] kcsan: Turn barrier instrumentation into macros Paul E. McKenney
` (2 subsequent siblings)
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
The barrier tests in selftest and the kcsan_test module only need the
spinlock and mutex to test correct barrier instrumentation. Therefore,
these were initially placed on the stack.
However, lockdep asserts that locks are in static storage, and will
generate this warning:
| INFO: trying to register non-static key.
| The code is fine but needs lockdep annotation, or maybe
| you didn't initialize this object before use?
| turning off the locking correctness validator.
| CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.16.0-rc1+ #3208
| Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-1ubuntu1.1 04/01/2014
| Call Trace:
| <TASK>
| dump_stack_lvl+0x88/0xd8
| dump_stack+0x15/0x1b
| register_lock_class+0x6b3/0x840
| ...
| test_barrier+0x490/0x14c7
| kcsan_selftest+0x47/0xa0
| ...
To fix, move the test locks into static storage.
Fixing the above also revealed that lock operations are strengthened on
first use with lockdep enabled, due to lockdep calling out into
non-instrumented files (recall that kernel/locking/lockdep.c is not
instrumented with KCSAN).
Only kcsan_test checks for over-instrumentation of *_lock() operations,
where we can simply "warm up" the test locks to avoid the test case
failing with lockdep.
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/kcsan/kcsan_test.c | 37 +++++++++++++++++++++++--------------
kernel/kcsan/selftest.c | 14 +++++++-------
2 files changed, 30 insertions(+), 21 deletions(-)
diff --git a/kernel/kcsan/kcsan_test.c b/kernel/kcsan/kcsan_test.c
index 5bf94550bcdf6..2bad0820f73ad 100644
--- a/kernel/kcsan/kcsan_test.c
+++ b/kernel/kcsan/kcsan_test.c
@@ -300,6 +300,8 @@ static struct {
long val[8];
} test_struct;
static DEFINE_SEQLOCK(test_seqlock);
+static DEFINE_SPINLOCK(test_spinlock);
+static DEFINE_MUTEX(test_mutex);
/*
* Helper to avoid compiler optimizing out reads, and to generate source values
@@ -523,8 +525,6 @@ static void test_barrier_nothreads(struct kunit *test)
struct kcsan_scoped_access *reorder_access = NULL;
#endif
arch_spinlock_t arch_spinlock = __ARCH_SPIN_LOCK_UNLOCKED;
- DEFINE_SPINLOCK(spinlock);
- DEFINE_MUTEX(mutex);
atomic_t dummy;
KCSAN_TEST_REQUIRES(test, reorder_access != NULL);
@@ -543,6 +543,15 @@ static void test_barrier_nothreads(struct kunit *test)
#define KCSAN_EXPECT_WRITE_BARRIER(b, o) __KCSAN_EXPECT_BARRIER(KCSAN_ACCESS_WRITE, b, o, #b)
#define KCSAN_EXPECT_RW_BARRIER(b, o) __KCSAN_EXPECT_BARRIER(KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE, b, o, #b)
+ /*
+ * Lockdep initialization can strengthen certain locking operations due
+ * to calling into instrumented files; "warm up" our locks.
+ */
+ spin_lock(&test_spinlock);
+ spin_unlock(&test_spinlock);
+ mutex_lock(&test_mutex);
+ mutex_unlock(&test_mutex);
+
/* Force creating a valid entry in reorder_access first. */
test_var = 0;
while (test_var++ < 1000000 && reorder_access->size != sizeof(test_var))
@@ -592,10 +601,10 @@ static void test_barrier_nothreads(struct kunit *test)
KCSAN_EXPECT_READ_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var), true);
KCSAN_EXPECT_READ_BARRIER(arch_spin_lock(&arch_spinlock), false);
KCSAN_EXPECT_READ_BARRIER(arch_spin_unlock(&arch_spinlock), true);
- KCSAN_EXPECT_READ_BARRIER(spin_lock(&spinlock), false);
- KCSAN_EXPECT_READ_BARRIER(spin_unlock(&spinlock), true);
- KCSAN_EXPECT_READ_BARRIER(mutex_lock(&mutex), false);
- KCSAN_EXPECT_READ_BARRIER(mutex_unlock(&mutex), true);
+ KCSAN_EXPECT_READ_BARRIER(spin_lock(&test_spinlock), false);
+ KCSAN_EXPECT_READ_BARRIER(spin_unlock(&test_spinlock), true);
+ KCSAN_EXPECT_READ_BARRIER(mutex_lock(&test_mutex), false);
+ KCSAN_EXPECT_READ_BARRIER(mutex_unlock(&test_mutex), true);
KCSAN_EXPECT_WRITE_BARRIER(mb(), true);
KCSAN_EXPECT_WRITE_BARRIER(wmb(), true);
@@ -638,10 +647,10 @@ static void test_barrier_nothreads(struct kunit *test)
KCSAN_EXPECT_WRITE_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var), true);
KCSAN_EXPECT_WRITE_BARRIER(arch_spin_lock(&arch_spinlock), false);
KCSAN_EXPECT_WRITE_BARRIER(arch_spin_unlock(&arch_spinlock), true);
- KCSAN_EXPECT_WRITE_BARRIER(spin_lock(&spinlock), false);
- KCSAN_EXPECT_WRITE_BARRIER(spin_unlock(&spinlock), true);
- KCSAN_EXPECT_WRITE_BARRIER(mutex_lock(&mutex), false);
- KCSAN_EXPECT_WRITE_BARRIER(mutex_unlock(&mutex), true);
+ KCSAN_EXPECT_WRITE_BARRIER(spin_lock(&test_spinlock), false);
+ KCSAN_EXPECT_WRITE_BARRIER(spin_unlock(&test_spinlock), true);
+ KCSAN_EXPECT_WRITE_BARRIER(mutex_lock(&test_mutex), false);
+ KCSAN_EXPECT_WRITE_BARRIER(mutex_unlock(&test_mutex), true);
KCSAN_EXPECT_RW_BARRIER(mb(), true);
KCSAN_EXPECT_RW_BARRIER(wmb(), true);
@@ -684,10 +693,10 @@ static void test_barrier_nothreads(struct kunit *test)
KCSAN_EXPECT_RW_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var), true);
KCSAN_EXPECT_RW_BARRIER(arch_spin_lock(&arch_spinlock), false);
KCSAN_EXPECT_RW_BARRIER(arch_spin_unlock(&arch_spinlock), true);
- KCSAN_EXPECT_RW_BARRIER(spin_lock(&spinlock), false);
- KCSAN_EXPECT_RW_BARRIER(spin_unlock(&spinlock), true);
- KCSAN_EXPECT_RW_BARRIER(mutex_lock(&mutex), false);
- KCSAN_EXPECT_RW_BARRIER(mutex_unlock(&mutex), true);
+ KCSAN_EXPECT_RW_BARRIER(spin_lock(&test_spinlock), false);
+ KCSAN_EXPECT_RW_BARRIER(spin_unlock(&test_spinlock), true);
+ KCSAN_EXPECT_RW_BARRIER(mutex_lock(&test_mutex), false);
+ KCSAN_EXPECT_RW_BARRIER(mutex_unlock(&test_mutex), true);
kcsan_nestable_atomic_end();
}
diff --git a/kernel/kcsan/selftest.c b/kernel/kcsan/selftest.c
index 08c6b84b9ebed..b6d4da07d80a1 100644
--- a/kernel/kcsan/selftest.c
+++ b/kernel/kcsan/selftest.c
@@ -113,6 +113,7 @@ static bool __init test_matching_access(void)
* positives: simple test to check at boot certain barriers are always properly
* instrumented. See kcsan_test for a more complete test.
*/
+static DEFINE_SPINLOCK(test_spinlock);
static bool __init test_barrier(void)
{
#ifdef CONFIG_KCSAN_WEAK_MEMORY
@@ -122,7 +123,6 @@ static bool __init test_barrier(void)
#endif
bool ret = true;
arch_spinlock_t arch_spinlock = __ARCH_SPIN_LOCK_UNLOCKED;
- DEFINE_SPINLOCK(spinlock);
atomic_t dummy;
long test_var;
@@ -172,8 +172,8 @@ static bool __init test_barrier(void)
KCSAN_CHECK_READ_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var));
arch_spin_lock(&arch_spinlock);
KCSAN_CHECK_READ_BARRIER(arch_spin_unlock(&arch_spinlock));
- spin_lock(&spinlock);
- KCSAN_CHECK_READ_BARRIER(spin_unlock(&spinlock));
+ spin_lock(&test_spinlock);
+ KCSAN_CHECK_READ_BARRIER(spin_unlock(&test_spinlock));
KCSAN_CHECK_WRITE_BARRIER(mb());
KCSAN_CHECK_WRITE_BARRIER(wmb());
@@ -202,8 +202,8 @@ static bool __init test_barrier(void)
KCSAN_CHECK_WRITE_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var));
arch_spin_lock(&arch_spinlock);
KCSAN_CHECK_WRITE_BARRIER(arch_spin_unlock(&arch_spinlock));
- spin_lock(&spinlock);
- KCSAN_CHECK_WRITE_BARRIER(spin_unlock(&spinlock));
+ spin_lock(&test_spinlock);
+ KCSAN_CHECK_WRITE_BARRIER(spin_unlock(&test_spinlock));
KCSAN_CHECK_RW_BARRIER(mb());
KCSAN_CHECK_RW_BARRIER(wmb());
@@ -235,8 +235,8 @@ static bool __init test_barrier(void)
KCSAN_CHECK_RW_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var));
arch_spin_lock(&arch_spinlock);
KCSAN_CHECK_RW_BARRIER(arch_spin_unlock(&arch_spinlock));
- spin_lock(&spinlock);
- KCSAN_CHECK_RW_BARRIER(spin_unlock(&spinlock));
+ spin_lock(&test_spinlock);
+ KCSAN_CHECK_RW_BARRIER(spin_unlock(&test_spinlock));
kcsan_nestable_atomic_end();
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 27/29] kcsan: Turn barrier instrumentation into macros
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (25 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 26/29] kcsan: Make barrier tests compatible with lockdep Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 28/29] kcsan: Avoid nested contexts reading inconsistent reorder_access Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 29/29] kcsan: Only test clear_bit_unlock_is_negative_byte if arch defines it Paul E. McKenney
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng,
kernel test robot, Paul E . McKenney
From: Marco Elver <elver@google.com>
Some architectures use barriers in 'extern inline' functions, from which
we should not refer to static inline functions.
For example, building Alpha with gcc and W=1 shows:
./include/asm-generic/barrier.h:70:30: warning: 'kcsan_rmb' is static but used in inline function 'pmd_offset' which is not static
70 | #define smp_rmb() do { kcsan_rmb(); __smp_rmb(); } while (0)
| ^~~~~~~~~
./arch/alpha/include/asm/pgtable.h:293:9: note: in expansion of macro 'smp_rmb'
293 | smp_rmb(); /* see above */
| ^~~~~~~
Which seems to warn about 6.7.4#3 of the C standard:
"An inline definition of a function with external linkage shall not
contain a definition of a modifiable object with static or thread
storage duration, and shall not contain a reference to an identifier
with internal linkage."
Fix it by turning barrier instrumentation into macros, which matches
definitions in <asm/barrier.h>.
Perhaps we can revert this change in future, when there are no more
'extern inline' users left.
Link: https://lkml.kernel.org/r/202112041334.X44uWZXf-lkp@intel.com
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
include/linux/kcsan-checks.h | 24 +++++++++++++-----------
1 file changed, 13 insertions(+), 11 deletions(-)
diff --git a/include/linux/kcsan-checks.h b/include/linux/kcsan-checks.h
index 9d2c869167f2e..92f3843d9ebb8 100644
--- a/include/linux/kcsan-checks.h
+++ b/include/linux/kcsan-checks.h
@@ -241,28 +241,30 @@ static inline void __kcsan_disable_current(void) { }
* disabled with the __no_kcsan function attribute.
*
* Also see definition of __tsan_atomic_signal_fence() in kernel/kcsan/core.c.
+ *
+ * These are all macros, like <asm/barrier.h>, since some architectures use them
+ * in non-static inline functions.
*/
#define __KCSAN_BARRIER_TO_SIGNAL_FENCE(name) \
- static __always_inline void kcsan_##name(void) \
- { \
+ do { \
barrier(); \
__atomic_signal_fence(__KCSAN_BARRIER_TO_SIGNAL_FENCE_##name); \
barrier(); \
- }
-__KCSAN_BARRIER_TO_SIGNAL_FENCE(mb)
-__KCSAN_BARRIER_TO_SIGNAL_FENCE(wmb)
-__KCSAN_BARRIER_TO_SIGNAL_FENCE(rmb)
-__KCSAN_BARRIER_TO_SIGNAL_FENCE(release)
+ } while (0)
+#define kcsan_mb() __KCSAN_BARRIER_TO_SIGNAL_FENCE(mb)
+#define kcsan_wmb() __KCSAN_BARRIER_TO_SIGNAL_FENCE(wmb)
+#define kcsan_rmb() __KCSAN_BARRIER_TO_SIGNAL_FENCE(rmb)
+#define kcsan_release() __KCSAN_BARRIER_TO_SIGNAL_FENCE(release)
#elif defined(CONFIG_KCSAN_WEAK_MEMORY) && defined(__KCSAN_INSTRUMENT_BARRIERS__)
#define kcsan_mb __kcsan_mb
#define kcsan_wmb __kcsan_wmb
#define kcsan_rmb __kcsan_rmb
#define kcsan_release __kcsan_release
#else /* CONFIG_KCSAN_WEAK_MEMORY && ... */
-static inline void kcsan_mb(void) { }
-static inline void kcsan_wmb(void) { }
-static inline void kcsan_rmb(void) { }
-static inline void kcsan_release(void) { }
+#define kcsan_mb() do { } while (0)
+#define kcsan_wmb() do { } while (0)
+#define kcsan_rmb() do { } while (0)
+#define kcsan_release() do { } while (0)
#endif /* CONFIG_KCSAN_WEAK_MEMORY && ... */
/**
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 28/29] kcsan: Avoid nested contexts reading inconsistent reorder_access
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (26 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 27/29] kcsan: Turn barrier instrumentation into macros Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
2021-12-14 22:04 ` [PATCH kcsan 29/29] kcsan: Only test clear_bit_unlock_is_negative_byte if arch defines it Paul E. McKenney
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Paul E . McKenney
From: Marco Elver <elver@google.com>
Nested contexts, such as nested interrupts or scheduler code, share the
same kcsan_ctx. When such a nested context reads an inconsistent
reorder_access due to an interrupt during set_reorder_access(), we can
observe the following warning:
| ------------[ cut here ]------------
| Cannot find frame for torture_random kernel/torture.c:456 in stack trace
| WARNING: CPU: 13 PID: 147 at kernel/kcsan/report.c:343 replace_stack_entry kernel/kcsan/report.c:343
| ...
| Call Trace:
| <TASK>
| sanitize_stack_entries kernel/kcsan/report.c:351 [inline]
| print_report kernel/kcsan/report.c:409
| kcsan_report_known_origin kernel/kcsan/report.c:693
| kcsan_setup_watchpoint kernel/kcsan/core.c:658
| rcutorture_one_extend kernel/rcu/rcutorture.c:1475
| rcutorture_loop_extend kernel/rcu/rcutorture.c:1558 [inline]
| ...
| </TASK>
| ---[ end trace ee5299cb933115f5 ]---
| ==================================================================
| BUG: KCSAN: data-race in _raw_spin_lock_irqsave / rcutorture_one_extend
|
| write (reordered) to 0xffffffff8c93b300 of 8 bytes by task 154 on cpu 12:
| queued_spin_lock include/asm-generic/qspinlock.h:80 [inline]
| do_raw_spin_lock include/linux/spinlock.h:185 [inline]
| __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:111 [inline]
| _raw_spin_lock_irqsave kernel/locking/spinlock.c:162
| try_to_wake_up kernel/sched/core.c:4003
| sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097
| asm_sysvec_apic_timer_interrupt arch/x86/include/asm/idtentry.h:638
| set_reorder_access kernel/kcsan/core.c:416 [inline] <-- inconsistent reorder_access
| kcsan_setup_watchpoint kernel/kcsan/core.c:693
| rcutorture_one_extend kernel/rcu/rcutorture.c:1475
| rcutorture_loop_extend kernel/rcu/rcutorture.c:1558 [inline]
| rcu_torture_one_read kernel/rcu/rcutorture.c:1600
| rcu_torture_reader kernel/rcu/rcutorture.c:1692
| kthread kernel/kthread.c:327
| ret_from_fork arch/x86/entry/entry_64.S:295
|
| read to 0xffffffff8c93b300 of 8 bytes by task 147 on cpu 13:
| rcutorture_one_extend kernel/rcu/rcutorture.c:1475
| rcutorture_loop_extend kernel/rcu/rcutorture.c:1558 [inline]
| ...
The warning is telling us that there was a data race which KCSAN wants
to report, but the function where the original access (that is now
reordered) happened cannot be found in the stack trace, which prevents
KCSAN from generating the right stack trace. The stack trace of "write
(reordered)" now only shows where the access was reordered to, but
should instead show the stack trace of the original write, with a final
line saying "reordered to".
At the point where set_reorder_access() is interrupted, it just set
reorder_access->ptr and size, at which point size is non-zero. This is
sufficient (if ctx->disable_scoped is zero) for further accesses from
nested contexts to perform checking of this reorder_access.
That then happened in _raw_spin_lock_irqsave(), which is called by
scheduler code. However, since reorder_access->ip is still stale (ptr
and size belong to a different ip not yet set) this finally leads to
replace_stack_entry() not finding the frame in reorder_access->ip and
generating the above warning.
Fix it by ensuring that a nested context cannot access reorder_access
while we update it in set_reorder_access(): set ctx->disable_scoped for
the duration that reorder_access is updated, which effectively locks
reorder_access and prevents concurrent use by nested contexts. Note,
set_reorder_access() can do the update only if disabled_scoped is zero
on entry, and must therefore set disable_scoped back to non-zero after
the initial check in set_reorder_access().
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/kcsan/core.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
index 9160609139666..fe12dfe254ecf 100644
--- a/kernel/kcsan/core.c
+++ b/kernel/kcsan/core.c
@@ -412,11 +412,20 @@ set_reorder_access(struct kcsan_ctx *ctx, const volatile void *ptr, size_t size,
if (!reorder_access || !kcsan_weak_memory)
return;
+ /*
+ * To avoid nested interrupts or scheduler (which share kcsan_ctx)
+ * reading an inconsistent reorder_access, ensure that the below has
+ * exclusive access to reorder_access by disallowing concurrent use.
+ */
+ ctx->disable_scoped++;
+ barrier();
reorder_access->ptr = ptr;
reorder_access->size = size;
reorder_access->type = type | KCSAN_ACCESS_SCOPED;
reorder_access->ip = ip;
reorder_access->stack_depth = get_kcsan_stack_depth();
+ barrier();
+ ctx->disable_scoped--;
}
/*
--
2.31.1.189.g2e36527f23
^ permalink raw reply [flat|nested] 30+ messages in thread* [PATCH kcsan 29/29] kcsan: Only test clear_bit_unlock_is_negative_byte if arch defines it
2021-12-14 22:03 [PATCH kcsan 0/29] Kernel Concurrency Sanitizer (KCSAN) updates for v5.17 Paul E. McKenney
` (27 preceding siblings ...)
2021-12-14 22:04 ` [PATCH kcsan 28/29] kcsan: Avoid nested contexts reading inconsistent reorder_access Paul E. McKenney
@ 2021-12-14 22:04 ` Paul E. McKenney
28 siblings, 0 replies; 30+ messages in thread
From: Paul E. McKenney @ 2021-12-14 22:04 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng,
kernel test robot, Paul E . McKenney
From: Marco Elver <elver@google.com>
Some architectures do not define clear_bit_unlock_is_negative_byte().
Only test it when it is actually defined (similar to other usage, such
as in lib/test_kasan.c).
Link: https://lkml.kernel.org/r/202112050757.x67rHnFU-lkp@intel.com
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/kcsan/kcsan_test.c | 8 +++++---
kernel/kcsan/selftest.c | 8 +++++---
2 files changed, 10 insertions(+), 6 deletions(-)
diff --git a/kernel/kcsan/kcsan_test.c b/kernel/kcsan/kcsan_test.c
index 2bad0820f73ad..a36fca063a73a 100644
--- a/kernel/kcsan/kcsan_test.c
+++ b/kernel/kcsan/kcsan_test.c
@@ -598,7 +598,6 @@ static void test_barrier_nothreads(struct kunit *test)
KCSAN_EXPECT_READ_BARRIER(test_and_change_bit(0, &test_var), true);
KCSAN_EXPECT_READ_BARRIER(clear_bit_unlock(0, &test_var), true);
KCSAN_EXPECT_READ_BARRIER(__clear_bit_unlock(0, &test_var), true);
- KCSAN_EXPECT_READ_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var), true);
KCSAN_EXPECT_READ_BARRIER(arch_spin_lock(&arch_spinlock), false);
KCSAN_EXPECT_READ_BARRIER(arch_spin_unlock(&arch_spinlock), true);
KCSAN_EXPECT_READ_BARRIER(spin_lock(&test_spinlock), false);
@@ -644,7 +643,6 @@ static void test_barrier_nothreads(struct kunit *test)
KCSAN_EXPECT_WRITE_BARRIER(test_and_change_bit(0, &test_var), true);
KCSAN_EXPECT_WRITE_BARRIER(clear_bit_unlock(0, &test_var), true);
KCSAN_EXPECT_WRITE_BARRIER(__clear_bit_unlock(0, &test_var), true);
- KCSAN_EXPECT_WRITE_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var), true);
KCSAN_EXPECT_WRITE_BARRIER(arch_spin_lock(&arch_spinlock), false);
KCSAN_EXPECT_WRITE_BARRIER(arch_spin_unlock(&arch_spinlock), true);
KCSAN_EXPECT_WRITE_BARRIER(spin_lock(&test_spinlock), false);
@@ -690,7 +688,6 @@ static void test_barrier_nothreads(struct kunit *test)
KCSAN_EXPECT_RW_BARRIER(test_and_change_bit(0, &test_var), true);
KCSAN_EXPECT_RW_BARRIER(clear_bit_unlock(0, &test_var), true);
KCSAN_EXPECT_RW_BARRIER(__clear_bit_unlock(0, &test_var), true);
- KCSAN_EXPECT_RW_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var), true);
KCSAN_EXPECT_RW_BARRIER(arch_spin_lock(&arch_spinlock), false);
KCSAN_EXPECT_RW_BARRIER(arch_spin_unlock(&arch_spinlock), true);
KCSAN_EXPECT_RW_BARRIER(spin_lock(&test_spinlock), false);
@@ -698,6 +695,11 @@ static void test_barrier_nothreads(struct kunit *test)
KCSAN_EXPECT_RW_BARRIER(mutex_lock(&test_mutex), false);
KCSAN_EXPECT_RW_BARRIER(mutex_unlock(&test_mutex), true);
+#ifdef clear_bit_unlock_is_negative_byte
+ KCSAN_EXPECT_READ_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var), true);
+ KCSAN_EXPECT_WRITE_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var), true);
+ KCSAN_EXPECT_RW_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var), true);
+#endif
kcsan_nestable_atomic_end();
}
diff --git a/kernel/kcsan/selftest.c b/kernel/kcsan/selftest.c
index b6d4da07d80a1..75712959c84e0 100644
--- a/kernel/kcsan/selftest.c
+++ b/kernel/kcsan/selftest.c
@@ -169,7 +169,6 @@ static bool __init test_barrier(void)
KCSAN_CHECK_READ_BARRIER(test_and_change_bit(0, &test_var));
KCSAN_CHECK_READ_BARRIER(clear_bit_unlock(0, &test_var));
KCSAN_CHECK_READ_BARRIER(__clear_bit_unlock(0, &test_var));
- KCSAN_CHECK_READ_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var));
arch_spin_lock(&arch_spinlock);
KCSAN_CHECK_READ_BARRIER(arch_spin_unlock(&arch_spinlock));
spin_lock(&test_spinlock);
@@ -199,7 +198,6 @@ static bool __init test_barrier(void)
KCSAN_CHECK_WRITE_BARRIER(test_and_change_bit(0, &test_var));
KCSAN_CHECK_WRITE_BARRIER(clear_bit_unlock(0, &test_var));
KCSAN_CHECK_WRITE_BARRIER(__clear_bit_unlock(0, &test_var));
- KCSAN_CHECK_WRITE_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var));
arch_spin_lock(&arch_spinlock);
KCSAN_CHECK_WRITE_BARRIER(arch_spin_unlock(&arch_spinlock));
spin_lock(&test_spinlock);
@@ -232,12 +230,16 @@ static bool __init test_barrier(void)
KCSAN_CHECK_RW_BARRIER(test_and_change_bit(0, &test_var));
KCSAN_CHECK_RW_BARRIER(clear_bit_unlock(0, &test_var));
KCSAN_CHECK_RW_BARRIER(__clear_bit_unlock(0, &test_var));
- KCSAN_CHECK_RW_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var));
arch_spin_lock(&arch_spinlock);
KCSAN_CHECK_RW_BARRIER(arch_spin_unlock(&arch_spinlock));
spin_lock(&test_spinlock);
KCSAN_CHECK_RW_BARRIER(spin_unlock(&test_spinlock));
+#ifdef clear_bit_unlock_is_negative_byte
+ KCSAN_CHECK_RW_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var));
+ KCSAN_CHECK_READ_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var));
+ KCSAN_CHECK_WRITE_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var));
+#endif
kcsan_nestable_atomic_end();
return ret;
--
2.31.1.189.g2e36527f23
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