[PATCH kcsan 0/3] KCSAN updates for v6.2

[PATCH kcsan 0/3] KCSAN updates for v6.2

[Paul E. McKenney]

Hello!

This series provides KCSAN updates:

1.	Instrument memcpy/memset/memmove with newer Clang, courtesy of
	Marco Elver.

2.	objtool, kcsan: Add volatile read/write instrumentation to
	whitelist, courtesy of Marco Elver.

3.	Fix trivial typo in Kconfig help comments, courtesy of Ryosuke
	Yasuoka.

						Thanx, Paul

------------------------------------------------------------------------

 kernel/kcsan/core.c   |   50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 lib/Kconfig.kcsan     |    6 +++---
 tools/objtool/check.c |   10 ++++++++++
 3 files changed, 63 insertions(+), 3 deletions(-)

[PATCH kcsan 1/3] kcsan: Instrument memcpy/memset/memmove with newer Clang

[Paul E. McKenney]

From: Marco Elver <elver@google.com>

With Clang version 16+, -fsanitize=thread will turn
memcpy/memset/memmove calls in instrumented functions into
__tsan_memcpy/__tsan_memset/__tsan_memmove calls respectively.

Add these functions to the core KCSAN runtime, so that we (a) catch data
races with mem* functions, and (b) won't run into linker errors with
such newer compilers.

Cc: stable@vger.kernel.org # v5.10+
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/kcsan/core.c | 50 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
index fe12dfe254ecf..54d077e1a2dc7 100644
--- a/kernel/kcsan/core.c
+++ b/kernel/kcsan/core.c
@@ -14,10 +14,12 @@
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/list.h>
+#include <linux/minmax.h>
 #include <linux/moduleparam.h>
 #include <linux/percpu.h>
 #include <linux/preempt.h>
 #include <linux/sched.h>
+#include <linux/string.h>
 #include <linux/uaccess.h>
 
 #include "encoding.h"
@@ -1308,3 +1310,51 @@ noinline void __tsan_atomic_signal_fence(int memorder)
 	}
 }
 EXPORT_SYMBOL(__tsan_atomic_signal_fence);
+
+#ifdef __HAVE_ARCH_MEMSET
+void *__tsan_memset(void *s, int c, size_t count);
+noinline void *__tsan_memset(void *s, int c, size_t count)
+{
+	/*
+	 * Instead of not setting up watchpoints where accessed size is greater
+	 * than MAX_ENCODABLE_SIZE, truncate checked size to MAX_ENCODABLE_SIZE.
+	 */
+	size_t check_len = min_t(size_t, count, MAX_ENCODABLE_SIZE);
+
+	check_access(s, check_len, KCSAN_ACCESS_WRITE, _RET_IP_);
+	return memset(s, c, count);
+}
+#else
+void *__tsan_memset(void *s, int c, size_t count) __alias(memset);
+#endif
+EXPORT_SYMBOL(__tsan_memset);
+
+#ifdef __HAVE_ARCH_MEMMOVE
+void *__tsan_memmove(void *dst, const void *src, size_t len);
+noinline void *__tsan_memmove(void *dst, const void *src, size_t len)
+{
+	size_t check_len = min_t(size_t, len, MAX_ENCODABLE_SIZE);
+
+	check_access(dst, check_len, KCSAN_ACCESS_WRITE, _RET_IP_);
+	check_access(src, check_len, 0, _RET_IP_);
+	return memmove(dst, src, len);
+}
+#else
+void *__tsan_memmove(void *dst, const void *src, size_t len) __alias(memmove);
+#endif
+EXPORT_SYMBOL(__tsan_memmove);
+
+#ifdef __HAVE_ARCH_MEMCPY
+void *__tsan_memcpy(void *dst, const void *src, size_t len);
+noinline void *__tsan_memcpy(void *dst, const void *src, size_t len)
+{
+	size_t check_len = min_t(size_t, len, MAX_ENCODABLE_SIZE);
+
+	check_access(dst, check_len, KCSAN_ACCESS_WRITE, _RET_IP_);
+	check_access(src, check_len, 0, _RET_IP_);
+	return memcpy(dst, src, len);
+}
+#else
+void *__tsan_memcpy(void *dst, const void *src, size_t len) __alias(memcpy);
+#endif
+EXPORT_SYMBOL(__tsan_memcpy);
-- 
2.31.1.189.g2e36527f23

[PATCH kcsan 2/3] objtool, kcsan: Add volatile read/write instrumentation to whitelist

[Paul E. McKenney]

From: Marco Elver <elver@google.com>

Adds KCSAN's volatile instrumentation to objtool's uaccess whitelist.

Recent kernel change have shown that this was missing from the uaccess
whitelist (since the first upstreamed version of KCSAN):

  mm/gup.o: warning: objtool: fault_in_readable+0x101: call to __tsan_volatile_write1() with UACCESS enabled

Fixes: 75d75b7a4d54 ("kcsan: Support distinguishing volatile accesses")
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 tools/objtool/check.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 43ec14c29a60c..a7f1e6c8bb0a7 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -999,6 +999,16 @@ static const char *uaccess_safe_builtin[] = {
 	"__tsan_read_write4",
 	"__tsan_read_write8",
 	"__tsan_read_write16",
+	"__tsan_volatile_read1",
+	"__tsan_volatile_read2",
+	"__tsan_volatile_read4",
+	"__tsan_volatile_read8",
+	"__tsan_volatile_read16",
+	"__tsan_volatile_write1",
+	"__tsan_volatile_write2",
+	"__tsan_volatile_write4",
+	"__tsan_volatile_write8",
+	"__tsan_volatile_write16",
 	"__tsan_atomic8_load",
 	"__tsan_atomic16_load",
 	"__tsan_atomic32_load",
-- 
2.31.1.189.g2e36527f23

[PATCH kcsan 3/3] kcsan: Fix trivial typo in Kconfig help comments

[Paul E. McKenney]

From: Ryosuke Yasuoka <ryasuoka@redhat.com>

Fix trivial typo in Kconfig help comments in KCSAN_SKIP_WATCH and
KCSAN_SKIP_WATCH_RANDOMIZE

Signed-off-by: Ryosuke Yasuoka <ryasuoka@redhat.com>
Reviewed-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 lib/Kconfig.kcsan | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/Kconfig.kcsan b/lib/Kconfig.kcsan
index 47a693c458642..375575a5a0e3c 100644
--- a/lib/Kconfig.kcsan
+++ b/lib/Kconfig.kcsan
@@ -125,7 +125,7 @@ config KCSAN_SKIP_WATCH
 	default 4000
 	help
 	  The number of per-CPU memory operations to skip, before another
-	  watchpoint is set up, i.e. one in KCSAN_WATCH_SKIP per-CPU
+	  watchpoint is set up, i.e. one in KCSAN_SKIP_WATCH per-CPU
 	  memory operations are used to set up a watchpoint. A smaller value
 	  results in more aggressive race detection, whereas a larger value
 	  improves system performance at the cost of missing some races.
@@ -135,8 +135,8 @@ config KCSAN_SKIP_WATCH_RANDOMIZE
 	default y
 	help
 	  If instruction skip count should be randomized, where the maximum is
-	  KCSAN_WATCH_SKIP. If false, the chosen value is always
-	  KCSAN_WATCH_SKIP.
+	  KCSAN_SKIP_WATCH. If false, the chosen value is always
+	  KCSAN_SKIP_WATCH.
 
 config KCSAN_INTERRUPT_WATCHER
 	bool "Interruptible watchers" if !KCSAN_STRICT
-- 
2.31.1.189.g2e36527f23