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    Subject[ 040/115] tracing: Use stack of calling function for stack tracer
    Date
    3.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

    commit 87889501d0adfae10e3b0f0e6f2d7536eed9ae84 upstream.

    Use the stack of stack_trace_call() instead of check_stack() as
    the test pointer for max stack size. It makes it a bit cleaner
    and a little more accurate.

    Adding stable, as a later fix depends on this patch.

    Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    kernel/trace/trace_stack.c | 12 +++++++-----
    1 file changed, 7 insertions(+), 5 deletions(-)

    --- a/kernel/trace/trace_stack.c
    +++ b/kernel/trace/trace_stack.c
    @@ -39,20 +39,21 @@ static DEFINE_MUTEX(stack_sysctl_mutex);
    int stack_tracer_enabled;
    static int last_stack_tracer_enabled;

    -static inline void check_stack(void)
    +static inline void
    +check_stack(unsigned long *stack)
    {
    unsigned long this_size, flags;
    unsigned long *p, *top, *start;
    int i;

    - this_size = ((unsigned long)&this_size) & (THREAD_SIZE-1);
    + this_size = ((unsigned long)stack) & (THREAD_SIZE-1);
    this_size = THREAD_SIZE - this_size;

    if (this_size <= max_stack_size)
    return;

    /* we do not handle interrupt stacks yet */
    - if (!object_is_on_stack(&this_size))
    + if (!object_is_on_stack(stack))
    return;

    local_irq_save(flags);
    @@ -73,7 +74,7 @@ static inline void check_stack(void)
    * Now find where in the stack these are.
    */
    i = 0;
    - start = &this_size;
    + start = stack;
    top = (unsigned long *)
    (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);

    @@ -113,6 +114,7 @@ static void
    stack_trace_call(unsigned long ip, unsigned long parent_ip,
    struct ftrace_ops *op, struct pt_regs *pt_regs)
    {
    + unsigned long stack;
    int cpu;

    preempt_disable_notrace();
    @@ -122,7 +124,7 @@ stack_trace_call(unsigned long ip, unsig
    if (per_cpu(trace_active, cpu)++ != 0)
    goto out;

    - check_stack();
    + check_stack(&stack);

    out:
    per_cpu(trace_active, cpu)--;



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