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* [PATCH 1/2] arm64: stacktrace: avoid listing stacktrace functions in stacktrace
@ 2017-08-30  7:32 Prakash Gupta
  2017-08-30  7:32 ` [PATCH 2/2] mm, page_owner: Skip unnecessary stack_trace entries Prakash Gupta
  2017-08-30 20:28 ` [PATCH 1/2] arm64: stacktrace: avoid listing stacktrace functions in stacktrace Andrew Morton
  0 siblings, 2 replies; 7+ messages in thread
From: Prakash Gupta @ 2017-08-30  7:32 UTC (permalink / raw)
  To: akpm, mhocko, vbabka, will.deacon, catalin.marinas,
	iamjoonsoo.kim, rmk+kernel, linux-kernel, linux-mm
  Cc: Prakash Gupta

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.

This was fixed for arch arm by Commit 3683f44c42e9 ("ARM: stacktrace: avoid
listing stacktrace functions in stacktrace")

Signed-off-by: Prakash Gupta <guptap@codeaurora.org>
---
 arch/arm64/kernel/stacktrace.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 3144584617e7..76809ccd309c 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -140,7 +140,8 @@ void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
 		trace->entries[trace->nr_entries++] = ULONG_MAX;
 }
 
-void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
+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;
@@ -150,15 +151,16 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 
 	data.trace = trace;
 	data.skip = trace->skip;
+	data.no_sched_functions = nosched;
 
 	if (tsk != current) {
-		data.no_sched_functions = 1;
 		frame.fp = thread_saved_fp(tsk);
 		frame.pc = thread_saved_pc(tsk);
 	} else {
-		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.pc = (unsigned long)save_stack_trace_tsk;
+		frame.pc = (unsigned long)__save_stack_trace;
 	}
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 	frame.graph = tsk->curr_ret_stack;
@@ -172,9 +174,15 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 }
 EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
 
+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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member of the Code Aurora Forum, hosted by The Linux Foundation

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^ permalink raw reply	[flat|nested] 7+ messages in thread

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Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-08-30  7:32 [PATCH 1/2] arm64: stacktrace: avoid listing stacktrace functions in stacktrace Prakash Gupta
2017-08-30  7:32 ` [PATCH 2/2] mm, page_owner: Skip unnecessary stack_trace entries Prakash Gupta
2017-08-31  7:34   ` Vlastimil Babka
2017-09-01  5:00     ` Prakash Gupta
2017-08-30 20:28 ` [PATCH 1/2] arm64: stacktrace: avoid listing stacktrace functions in stacktrace Andrew Morton
2017-08-31  6:28   ` Prakash Gupta
2017-09-04 10:29   ` Catalin Marinas

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