[PATCH v3 10/13] x86/dumpstack: Try harder to get a call trace on stack overflow

Andy Lutomirski
2016-06-20T23:45:15Z

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>
---
arch/x86/kernel/dumpstack.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index d4d085e27d04..9cdf05d768cf 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -89,7 +89,7 @@ static inline int valid_stack_ptr(struct thread_info *tinfo,
else
return 0;
}
- return p > t && p < t + THREAD_SIZE - size;
+ return p >= t && p < t + THREAD_SIZE - size;
}

unsigned long
@@ -100,6 +100,13 @@ print_context_stack(struct thread_info *tinfo,
{
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)tinfo - (unsigned long)stack < PAGE_SIZE)
+ stack = (unsigned long *)tinfo;
+
while (valid_stack_ptr(tinfo, stack, sizeof(*stack), end)) {
unsigned long addr;

--
2.5.5