Commit 29a77bbb authored by Joe Lawrence's avatar Joe Lawrence Committed by Michael Ellerman
Browse files

powerpc/livepatch: small cleanups in save_stack_trace_tsk_reliable() 



Mostly cosmetic changes:

- Group common stack pointer code at the top
- Simplify the first frame logic
- Code stackframe iteration into for...loop construct
- Check for trace->nr_entries overflow before adding any into the array

Suggested-by: default avatarNicolai Stange <nstange@suse.de>
Signed-off-by: default avatarJoe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 18be3760

arch/powerpc/kernel/stacktrace.c

+14 −26
Original line number Diff line number Diff line
@@ -95,20 +95,11 @@ save_stack_trace_tsk_reliable(struct task_struct *tsk, 
				struct stack_trace *trace)

{

	unsigned long sp;

	unsigned long newsp;

	unsigned long stack_page = (unsigned long)task_stack_page(tsk);

	unsigned long stack_end;

	int graph_idx = 0;



	/*

	 * The last frame (unwinding first) may not yet have saved

	 * its LR onto the stack.

	 */

	int firstframe = 1;



	if (tsk == current)

		sp = current_stack_pointer();

	else

		sp = tsk->thread.ksp;

	bool firstframe;



	stack_end = stack_page + THREAD_SIZE;

	if (!is_idle_task(tsk)) {
@@ -135,14 +126,20 @@ save_stack_trace_tsk_reliable(struct task_struct *tsk, 
		stack_end -= STACK_FRAME_OVERHEAD;

	}



	if (tsk == current)

		sp = current_stack_pointer();

	else

		sp = tsk->thread.ksp;



	if (sp < stack_page + sizeof(struct thread_struct) ||

	    sp > stack_end - STACK_FRAME_MIN_SIZE) {

		return 1;

	}



	for (;;) {

	for (firstframe = true; sp != stack_end;

	     firstframe = false, sp = newsp) {

		unsigned long *stack = (unsigned long *) sp;

		unsigned long newsp, ip;

		unsigned long ip;



		/* sanity check: ABI requires SP to be aligned 16 bytes. */

		if (sp & 0xF)
@@ -163,10 +160,8 @@ save_stack_trace_tsk_reliable(struct task_struct *tsk, 
		 * rest of the frame may be uninitialized, continue to

		 * the next.

		 */

		if (firstframe) {

			firstframe = 0;

			goto next;

		}

		if (firstframe)

			continue;



		/* Mark stacktraces with exception frames as unreliable. */

		if (sp <= stack_end - STACK_INT_FRAME_SIZE &&
@@ -193,19 +188,12 @@ save_stack_trace_tsk_reliable(struct task_struct *tsk, 
			return 1;

#endif



		if (trace->nr_entries >= trace->max_entries)

			return -E2BIG;

		if (!trace->skip)

			trace->entries[trace->nr_entries++] = ip;

		else

			trace->skip--;



next:

		if (newsp == stack_end)

			break;



		if (trace->nr_entries >= trace->max_entries)

			return -E2BIG;



		sp = newsp;

	}

	return 0;

}

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