tracing: Use stack of calling function for stack tracer

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.

Cc: stable@vger.kernel.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 7 insertions, 5 deletions

diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 42ca822fc701..dc02e29d8255 100644
--- 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, unsigned long parent_ip,
         if (per_cpu(trace_active, cpu)++ != 0)
                 goto out;
 
-        check_stack();
+        check_stack(&stack);
 
  out:
         per_cpu(trace_active, cpu)--;