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Subject[tip:x86/mm] x86/dumpstack: Try harder to get a call trace on stack overflow
Commit-ID:  9a2e9da3e003112399f2863b7b6b911043c01895
Gitweb: http://git.kernel.org/tip/9a2e9da3e003112399f2863b7b6b911043c01895
Author: Andy Lutomirski <luto@kernel.org>
AuthorDate: Thu, 14 Jul 2016 13:22:52 -0700
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 15 Jul 2016 10:26:26 +0200

x86/dumpstack: Try harder to get a call trace on stack overflow

If we overflow the stack, print_context_stack() will abort. Detect
this case and rewind back into the valid part of the stack so that
we can trace it.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
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>
Link: http://lkml.kernel.org/r/ee1690eb2715ccc5dc187fde94effa4ca0ccbbcd.1468527351.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/dumpstack.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index ef8017c..cc88e25 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -87,7 +87,7 @@ static inline int valid_stack_ptr(struct task_struct *task,
else
return 0;
}
- return p > t && p < t + THREAD_SIZE - size;
+ return p >= t && p < t + THREAD_SIZE - size;
}

unsigned long
@@ -98,6 +98,14 @@ print_context_stack(struct task_struct *task,
{
struct stack_frame *frame = (struct stack_frame *)bp;

+ /*
+ * If we overflowed the stack into a guard page, jump back to the
+ * bottom of the usable stack.
+ */
+ if ((unsigned long)task_stack_page(task) - (unsigned long)stack <
+ PAGE_SIZE)
+ stack = (unsigned long *)task_stack_page(task);
+
while (valid_stack_ptr(task, stack, sizeof(*stack), end)) {
unsigned long addr;

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