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