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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: Nicolai Stange <nstange@suse.de>
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Joe Lawrence 2019-01-22 10:57:23 -05:00 committed by Michael Ellerman
parent 18be37603d
commit 29a77bbb0c
1 changed files with 14 additions and 26 deletions
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40
arch/powerpc/kernel/stacktrace.c
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@ -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;
}