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    Subject[PATCH 04/11] 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.

    Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
    Signed-off-by: Andy Lutomirski <luto@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 ef8017ca5ba9..cc88e25d73e9 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;

    --
    2.7.4
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