lkml.org 
[lkml]   [2016]   [Jun]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 10/13] x86/dumpstack: Try harder to get a call trace on stack overflow
On Wed, Jun 15, 2016 at 05:28:32PM -0700, Andy Lutomirski wrote:
> 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 | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
> index d4d085e27d04..400a2e17c1d1 100644
> --- a/arch/x86/kernel/dumpstack.c
> +++ b/arch/x86/kernel/dumpstack.c
> @@ -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 + 1;

That will start walking the stack in the middle of the thread_info
struct.

I think you meant:

stack = (unsigned long *)(tinfo + 1)

However, thread_info will have been overwritten anyway. So maybe it
should just be:

stack = tinfo;

(Though that still wouldn't quite work because the valid_stack_ptr()
check would fail...)

> +
> while (valid_stack_ptr(tinfo, stack, sizeof(*stack), end)) {
> unsigned long addr;

--
Josh

\
 
 \ /
  Last update: 2016-06-16 21:01    [W:0.286 / U:4.544 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site