* [PATCH 1/2] x86/unwind: Silence more entry-code related warnings
@ 2017-04-26 1:48 Josh Poimboeuf
2017-04-26 1:48 ` [PATCH 2/2] x86/unwind: Dump all stacks in unwind_dump() Josh Poimboeuf
2017-04-26 8:24 ` [tip:x86/asm] x86/unwind: Silence more entry-code related warnings tip-bot for Josh Poimboeuf
0 siblings, 2 replies; 4+ messages in thread
From: Josh Poimboeuf @ 2017-04-26 1:48 UTC (permalink / raw)
To: x86; +Cc: linux-kernel, Borislav Petkov
Borislav Petkov reported the following unwinder warning:
WARNING: kernel stack regs at ffffc9000024fea8 in udevadm:92 has bad 'bp' value 00007fffc4614d30
unwind stack type:0 next_sp: (null) mask:0x6 graph_idx:0
ffffc9000024fea8: 000055a6100e9b38 (0x55a6100e9b38)
ffffc9000024feb0: 000055a6100e9b35 (0x55a6100e9b35)
ffffc9000024feb8: 000055a6100e9f68 (0x55a6100e9f68)
ffffc9000024fec0: 000055a6100e9f50 (0x55a6100e9f50)
ffffc9000024fec8: 00007fffc4614d30 (0x7fffc4614d30)
ffffc9000024fed0: 000055a6100eaf50 (0x55a6100eaf50)
ffffc9000024fed8: 0000000000000000 ...
ffffc9000024fee0: 0000000000000100 (0x100)
ffffc9000024fee8: ffff8801187df488 (0xffff8801187df488)
ffffc9000024fef0: 00007ffffffff000 (0x7ffffffff000)
ffffc9000024fef8: 0000000000000000 ...
ffffc9000024ff10: ffffc9000024fe98 (0xffffc9000024fe98)
ffffc9000024ff18: 00007fffc4614d00 (0x7fffc4614d00)
ffffc9000024ff20: ffffffffffffff10 (0xffffffffffffff10)
ffffc9000024ff28: ffffffff811c6c1f (SyS_newlstat+0xf/0x10)
ffffc9000024ff30: 0000000000000010 (0x10)
ffffc9000024ff38: 0000000000000296 (0x296)
ffffc9000024ff40: ffffc9000024ff50 (0xffffc9000024ff50)
ffffc9000024ff48: 0000000000000018 (0x18)
ffffc9000024ff50: ffffffff816b2e6a (entry_SYSCALL_64_fastpath+0x18/0xa8)
...
It unwinded from an interrupt which came in right after entry code
called into a C syscall handler, before it had a chance to set up the
frame pointer, so regs->bp still had its user space value.
Add a check to silence warnings in such a case, where an interrupt
has occurred and regs->sp is almost at the end of the stack.
Reported-by: Borislav Petkov <bp@suse.de>
Tested-by: Borislav Petkov <bp@suse.de>
Fixes: c32c47c68a0a ("x86/unwind: Warn on bad frame pointer")
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
arch/x86/kernel/unwind_frame.c | 20 +++++++++++++++++---
1 file changed, 17 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
index bda82df..ae0821f 100644
--- a/arch/x86/kernel/unwind_frame.c
+++ b/arch/x86/kernel/unwind_frame.c
@@ -91,16 +91,26 @@ static bool in_entry_code(unsigned long ip)
return false;
}
+static inline unsigned long *last_frame(struct unwind_state *state)
+{
+ return (unsigned long *)task_pt_regs(state->task) - 2;
+}
+
#ifdef CONFIG_X86_32
#define GCC_REALIGN_WORDS 3
#else
#define GCC_REALIGN_WORDS 1
#endif
+static inline unsigned long *last_aligned_frame(struct unwind_state *state)
+{
+ return last_frame(state) - GCC_REALIGN_WORDS;
+}
+
static bool is_last_task_frame(struct unwind_state *state)
{
- unsigned long *last_bp = (unsigned long *)task_pt_regs(state->task) - 2;
- unsigned long *aligned_bp = last_bp - GCC_REALIGN_WORDS;
+ unsigned long *last_bp = last_frame(state);
+ unsigned long *aligned_bp = last_aligned_frame(state);
/*
* We have to check for the last task frame at two different locations
@@ -277,10 +287,14 @@ bool unwind_next_frame(struct unwind_state *state)
/*
* Don't warn if the unwinder got lost due to an interrupt in entry
- * code before the stack was set up:
+ * code or in the C handler before the first frame pointer got set up:
*/
if (state->got_irq && in_entry_code(state->ip))
goto the_end;
+ if (state->regs &&
+ state->regs->sp >= (unsigned long)last_aligned_frame(state) &&
+ state->regs->sp < (unsigned long)task_pt_regs(state->task))
+ goto the_end;
if (state->regs) {
printk_deferred_once(KERN_WARNING
--
2.7.4
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH 2/2] x86/unwind: Dump all stacks in unwind_dump()
2017-04-26 1:48 [PATCH 1/2] x86/unwind: Silence more entry-code related warnings Josh Poimboeuf
@ 2017-04-26 1:48 ` Josh Poimboeuf
2017-04-26 8:25 ` [tip:x86/asm] " tip-bot for Josh Poimboeuf
2017-04-26 8:24 ` [tip:x86/asm] x86/unwind: Silence more entry-code related warnings tip-bot for Josh Poimboeuf
1 sibling, 1 reply; 4+ messages in thread
From: Josh Poimboeuf @ 2017-04-26 1:48 UTC (permalink / raw)
To: x86; +Cc: linux-kernel
Currently unwind_dump() dumps only the most recently accessed stack.
But it has a few issues.
In some cases, 'first_sp' can get out of sync with 'stack_info', causing
unwind_dump() to start from the wrong address, flood the printk buffer,
and eventually read a bad address.
In other cases, dumping only the most recently accessed stack doesn't
give enough data to diagnose the error.
Fix both issues by dumping *all* stacks involved in the trace, not just
the last one.
Fixes: 8b5e99f02264 ("x86/unwind: Dump stack data on warnings")
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
arch/x86/kernel/unwind_frame.c | 34 +++++++++++++++++++++-------------
1 file changed, 21 insertions(+), 13 deletions(-)
diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
index ae0821f..fec70fe 100644
--- a/arch/x86/kernel/unwind_frame.c
+++ b/arch/x86/kernel/unwind_frame.c
@@ -30,6 +30,8 @@ static void unwind_dump(struct unwind_state *state)
static bool dumped_before = false;
bool prev_zero, zero = false;
unsigned long word, *sp;
+ struct stack_info stack_info = {0};
+ unsigned long visit_mask = 0;
if (dumped_before)
return;
@@ -40,21 +42,27 @@ static void unwind_dump(struct unwind_state *state)
state->stack_info.type, state->stack_info.next_sp,
state->stack_mask, state->graph_idx);
- for (sp = state->orig_sp; sp < state->stack_info.end; sp++) {
- word = READ_ONCE_NOCHECK(*sp);
+ for (sp = state->orig_sp; sp; sp = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
+ if (get_stack_info(sp, state->task, &stack_info, &visit_mask))
+ break;
- prev_zero = zero;
- zero = word == 0;
+ for (; sp < stack_info.end; sp++) {
- if (zero) {
- if (!prev_zero)
- printk_deferred("%p: %0*x ...\n",
- sp, BITS_PER_LONG/4, 0);
- continue;
- }
+ word = READ_ONCE_NOCHECK(*sp);
+
+ prev_zero = zero;
+ zero = word == 0;
- printk_deferred("%p: %0*lx (%pB)\n",
- sp, BITS_PER_LONG/4, word, (void *)word);
+ if (zero) {
+ if (!prev_zero)
+ printk_deferred("%p: %0*x ...\n",
+ sp, BITS_PER_LONG/4, 0);
+ continue;
+ }
+
+ printk_deferred("%p: %0*lx (%pB)\n",
+ sp, BITS_PER_LONG/4, word, (void *)word);
+ }
}
}
@@ -216,7 +224,7 @@ static bool update_stack_state(struct unwind_state *state,
}
/* Save the original stack pointer for unwind_dump(): */
- if (!state->orig_sp || info->type != prev_type)
+ if (!state->orig_sp)
state->orig_sp = frame;
return true;
--
2.7.4
^ permalink raw reply [flat|nested] 4+ messages in thread
* [tip:x86/asm] x86/unwind: Silence more entry-code related warnings
2017-04-26 1:48 [PATCH 1/2] x86/unwind: Silence more entry-code related warnings Josh Poimboeuf
2017-04-26 1:48 ` [PATCH 2/2] x86/unwind: Dump all stacks in unwind_dump() Josh Poimboeuf
@ 2017-04-26 8:24 ` tip-bot for Josh Poimboeuf
1 sibling, 0 replies; 4+ messages in thread
From: tip-bot for Josh Poimboeuf @ 2017-04-26 8:24 UTC (permalink / raw)
To: linux-tip-commits
Cc: dvlasenk, mingo, linux-kernel, tglx, hpa, peterz, jpoimboe,
torvalds, bp, bp, luto, brgerst
Commit-ID: b0d50c7b5d807ce6f7ba58e42b260e92bd7d88fb
Gitweb: http://git.kernel.org/tip/b0d50c7b5d807ce6f7ba58e42b260e92bd7d88fb
Author: Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Tue, 25 Apr 2017 20:48:51 -0500
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 26 Apr 2017 08:19:05 +0200
x86/unwind: Silence more entry-code related warnings
Borislav Petkov reported the following unwinder warning:
WARNING: kernel stack regs at ffffc9000024fea8 in udevadm:92 has bad 'bp' value 00007fffc4614d30
unwind stack type:0 next_sp: (null) mask:0x6 graph_idx:0
ffffc9000024fea8: 000055a6100e9b38 (0x55a6100e9b38)
ffffc9000024feb0: 000055a6100e9b35 (0x55a6100e9b35)
ffffc9000024feb8: 000055a6100e9f68 (0x55a6100e9f68)
ffffc9000024fec0: 000055a6100e9f50 (0x55a6100e9f50)
ffffc9000024fec8: 00007fffc4614d30 (0x7fffc4614d30)
ffffc9000024fed0: 000055a6100eaf50 (0x55a6100eaf50)
ffffc9000024fed8: 0000000000000000 ...
ffffc9000024fee0: 0000000000000100 (0x100)
ffffc9000024fee8: ffff8801187df488 (0xffff8801187df488)
ffffc9000024fef0: 00007ffffffff000 (0x7ffffffff000)
ffffc9000024fef8: 0000000000000000 ...
ffffc9000024ff10: ffffc9000024fe98 (0xffffc9000024fe98)
ffffc9000024ff18: 00007fffc4614d00 (0x7fffc4614d00)
ffffc9000024ff20: ffffffffffffff10 (0xffffffffffffff10)
ffffc9000024ff28: ffffffff811c6c1f (SyS_newlstat+0xf/0x10)
ffffc9000024ff30: 0000000000000010 (0x10)
ffffc9000024ff38: 0000000000000296 (0x296)
ffffc9000024ff40: ffffc9000024ff50 (0xffffc9000024ff50)
ffffc9000024ff48: 0000000000000018 (0x18)
ffffc9000024ff50: ffffffff816b2e6a (entry_SYSCALL_64_fastpath+0x18/0xa8)
...
It unwinded from an interrupt which came in right after entry code
called into a C syscall handler, before it had a chance to set up the
frame pointer, so regs->bp still had its user space value.
Add a check to silence warnings in such a case, where an interrupt
has occurred and regs->sp is almost at the end of the stack.
Reported-by: Borislav Petkov <bp@suse.de>
Tested-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: c32c47c68a0a ("x86/unwind: Warn on bad frame pointer")
Link: http://lkml.kernel.org/r/c695f0d0d4c2cfe6542b90e2d0520e11eb901eb5.1493171120.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/unwind_frame.c | 20 +++++++++++++++++---
1 file changed, 17 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
index bda82df..ae0821f 100644
--- a/arch/x86/kernel/unwind_frame.c
+++ b/arch/x86/kernel/unwind_frame.c
@@ -91,16 +91,26 @@ static bool in_entry_code(unsigned long ip)
return false;
}
+static inline unsigned long *last_frame(struct unwind_state *state)
+{
+ return (unsigned long *)task_pt_regs(state->task) - 2;
+}
+
#ifdef CONFIG_X86_32
#define GCC_REALIGN_WORDS 3
#else
#define GCC_REALIGN_WORDS 1
#endif
+static inline unsigned long *last_aligned_frame(struct unwind_state *state)
+{
+ return last_frame(state) - GCC_REALIGN_WORDS;
+}
+
static bool is_last_task_frame(struct unwind_state *state)
{
- unsigned long *last_bp = (unsigned long *)task_pt_regs(state->task) - 2;
- unsigned long *aligned_bp = last_bp - GCC_REALIGN_WORDS;
+ unsigned long *last_bp = last_frame(state);
+ unsigned long *aligned_bp = last_aligned_frame(state);
/*
* We have to check for the last task frame at two different locations
@@ -277,10 +287,14 @@ bad_address:
/*
* Don't warn if the unwinder got lost due to an interrupt in entry
- * code before the stack was set up:
+ * code or in the C handler before the first frame pointer got set up:
*/
if (state->got_irq && in_entry_code(state->ip))
goto the_end;
+ if (state->regs &&
+ state->regs->sp >= (unsigned long)last_aligned_frame(state) &&
+ state->regs->sp < (unsigned long)task_pt_regs(state->task))
+ goto the_end;
if (state->regs) {
printk_deferred_once(KERN_WARNING
^ permalink raw reply [flat|nested] 4+ messages in thread
* [tip:x86/asm] x86/unwind: Dump all stacks in unwind_dump()
2017-04-26 1:48 ` [PATCH 2/2] x86/unwind: Dump all stacks in unwind_dump() Josh Poimboeuf
@ 2017-04-26 8:25 ` tip-bot for Josh Poimboeuf
0 siblings, 0 replies; 4+ messages in thread
From: tip-bot for Josh Poimboeuf @ 2017-04-26 8:25 UTC (permalink / raw)
To: linux-tip-commits
Cc: tglx, mingo, bp, torvalds, jpoimboe, luto, brgerst, dvlasenk,
hpa, linux-kernel, peterz
Commit-ID: 262fa734a0023a43391f9bd4a4099487b8393f35
Gitweb: http://git.kernel.org/tip/262fa734a0023a43391f9bd4a4099487b8393f35
Author: Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Tue, 25 Apr 2017 20:48:52 -0500
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 26 Apr 2017 08:19:05 +0200
x86/unwind: Dump all stacks in unwind_dump()
Currently unwind_dump() dumps only the most recently accessed stack.
But it has a few issues.
In some cases, 'first_sp' can get out of sync with 'stack_info', causing
unwind_dump() to start from the wrong address, flood the printk buffer,
and eventually read a bad address.
In other cases, dumping only the most recently accessed stack doesn't
give enough data to diagnose the error.
Fix both issues by dumping *all* stacks involved in the trace, not just
the last one.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 8b5e99f02264 ("x86/unwind: Dump stack data on warnings")
Link: http://lkml.kernel.org/r/016d6a9810d7d1bfc87ef8c0e6ee041c6744c909.1493171120.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/unwind_frame.c | 34 +++++++++++++++++++++-------------
1 file changed, 21 insertions(+), 13 deletions(-)
diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
index ae0821f..fec70fe 100644
--- a/arch/x86/kernel/unwind_frame.c
+++ b/arch/x86/kernel/unwind_frame.c
@@ -30,6 +30,8 @@ static void unwind_dump(struct unwind_state *state)
static bool dumped_before = false;
bool prev_zero, zero = false;
unsigned long word, *sp;
+ struct stack_info stack_info = {0};
+ unsigned long visit_mask = 0;
if (dumped_before)
return;
@@ -40,21 +42,27 @@ static void unwind_dump(struct unwind_state *state)
state->stack_info.type, state->stack_info.next_sp,
state->stack_mask, state->graph_idx);
- for (sp = state->orig_sp; sp < state->stack_info.end; sp++) {
- word = READ_ONCE_NOCHECK(*sp);
+ for (sp = state->orig_sp; sp; sp = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
+ if (get_stack_info(sp, state->task, &stack_info, &visit_mask))
+ break;
- prev_zero = zero;
- zero = word == 0;
+ for (; sp < stack_info.end; sp++) {
- if (zero) {
- if (!prev_zero)
- printk_deferred("%p: %0*x ...\n",
- sp, BITS_PER_LONG/4, 0);
- continue;
- }
+ word = READ_ONCE_NOCHECK(*sp);
+
+ prev_zero = zero;
+ zero = word == 0;
- printk_deferred("%p: %0*lx (%pB)\n",
- sp, BITS_PER_LONG/4, word, (void *)word);
+ if (zero) {
+ if (!prev_zero)
+ printk_deferred("%p: %0*x ...\n",
+ sp, BITS_PER_LONG/4, 0);
+ continue;
+ }
+
+ printk_deferred("%p: %0*lx (%pB)\n",
+ sp, BITS_PER_LONG/4, word, (void *)word);
+ }
}
}
@@ -216,7 +224,7 @@ static bool update_stack_state(struct unwind_state *state,
}
/* Save the original stack pointer for unwind_dump(): */
- if (!state->orig_sp || info->type != prev_type)
+ if (!state->orig_sp)
state->orig_sp = frame;
return true;
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2017-04-26 8:32 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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