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    Subject[PATCH] ARM:stacktrace: make stacktrace skip always right.
    Date
    This patch is for commit 3683f44c42e991d313dc301504ee0fca1aeb8580,
    that makes stacktrace NOT begin from stacktrace self function,
    which are: __save_stack_trace and save_stack_trace.

    But save_stack_trace will NOT have stacktrace information when build
    with '-O2', assemble code looks like below:
    00000154 <save_stack_trace>:
    154: e1a0200d mov r2, sp
    158: e1a01000 mov r1, r0
    15c: e3c23d7f bic r3, r2, #8128 ; 0x1fc0
    160: e3a02000 mov r2, #0
    164: e3c3303f bic r3, r3, #63 ; 0x3f
    168: e593000c ldr r0, [r3, #12]
    16c: eaffffd0 b b4 <__save_stack_trace>

    In this situation, the "data.skip +=2" operation will skip the last
    user call function, make user stacktrace strange/incorrect.

    To fix this, we have to make sure save_stack_trace has stacktrace info,
    then skip 2 function will be OK.

    Signed-off-by: Wang Kai <morgan.wang@huawei.com>
    ---
    arch/arm/kernel/stacktrace.c | 1 +
    1 file changed, 1 insertion(+)

    diff --git a/arch/arm/kernel/stacktrace.c b/arch/arm/kernel/stacktrace.c
    index 6582c4a..1eb1b5ae 100644
    --- a/arch/arm/kernel/stacktrace.c
    +++ b/arch/arm/kernel/stacktrace.c
    @@ -134,6 +134,7 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
    void save_stack_trace(struct stack_trace *trace)
    {
    __save_stack_trace(current, trace, 0);
    + asm volatile("" : : : "memory");
    }
    EXPORT_SYMBOL_GPL(save_stack_trace);
    #endif
    --
    1.8.5.5


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