Commit 3683f44c authored by Russell King's avatar Russell King
Browse files

ARM: stacktrace: avoid listing stacktrace functions in stacktrace 



While debugging the FEC ethernet driver using stacktrace, it was noticed
that the stacktraces always begin as follows:

 [<c00117b4>] save_stack_trace_tsk+0x0/0x98
 [<c0011870>] save_stack_trace+0x24/0x28
 ...

This is because the stack trace code includes the stack frames for itself.
This is incorrect behaviour, and also leads to "skip" doing the wrong
thing (which is the number of stack frames to avoid recording.)

Perversely, it does the right thing when passed a non-current thread.  Fix
this by ensuring that we have a known constant number of frames above the
main stack trace function, and always skip these.

Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent deace4a6

arch/arm/kernel/stacktrace.c

+13 −5
Original line number Diff line number Diff line
@@ -83,13 +83,16 @@ static int save_trace(struct stackframe *frame, void *d) 
	return trace->nr_entries >= trace->max_entries;

}



void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)

/* This must be noinline to so that our skip calculation works correctly */

static noinline void __save_stack_trace(struct task_struct *tsk,

	struct stack_trace *trace, unsigned int nosched)

{

	struct stack_trace_data data;

	struct stackframe frame;



	data.trace = trace;

	data.skip = trace->skip;

	data.no_sched_functions = nosched;



	if (tsk != current) {

#ifdef CONFIG_SMP
@@ -102,7 +105,6 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) 
			trace->entries[trace->nr_entries++] = ULONG_MAX;

		return;

#else

		data.no_sched_functions = 1;

		frame.fp = thread_saved_fp(tsk);

		frame.sp = thread_saved_sp(tsk);

		frame.lr = 0;		/* recovered from the stack */
@@ -111,11 +113,12 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) 
	} else {

		register unsigned long current_sp asm ("sp");



		data.no_sched_functions = 0;

		/* We don't want this function nor the caller */

		data.skip += 2;

		frame.fp = (unsigned long)__builtin_frame_address(0);

		frame.sp = current_sp;

		frame.lr = (unsigned long)__builtin_return_address(0);

		frame.pc = (unsigned long)save_stack_trace_tsk;

		frame.pc = (unsigned long)__save_stack_trace;

	}



	walk_stackframe(&frame, save_trace, &data);
@@ -123,9 +126,14 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) 
		trace->entries[trace->nr_entries++] = ULONG_MAX;

}



void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)

{

	__save_stack_trace(tsk, trace, 1);

}



void save_stack_trace(struct stack_trace *trace)

{

	save_stack_trace_tsk(current, trace);

	__save_stack_trace(current, trace, 0);

}

EXPORT_SYMBOL_GPL(save_stack_trace);

#endif

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