linux-kernel - Re: [BUG REPORT] perf tools: x86_64: Broken calllchain when sampling taken at 'callq' instruction

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Date:	Wed, 18 Nov 2015 16:00:17 +0800
From:	"Wangnan (F)" <wangnan0@...wei.com>
To:	Jiri Olsa <jolsa@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	David Ahern <dsahern@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Milian Wolff <milian.wolff@...b.com>
CC:	<linux-kernel@...r.kernel.org>, pi3orama <pi3orama@....com>,
	"lizefan 00213767" <lizefan@...wei.com>
Subject: Re: [BUG REPORT] perf tools: x86_64: Broken calllchain when sampling
 taken at 'callq' instruction



On 2015/11/18 15:20, Wangnan (F) wrote:
> Hi all,
>
> When analysising Jiri's patchset [1] I found a dwarf unwind problem.
> On x86 platform, when sample is at a 'callq' instruction, dwarf based
> stack unwind always fail.
>
> I compile a small C source file with debug information, turn off
> frame pointer and disable optimization:
>
> $ gcc -g -O0 -fomit-frame-pointer ./test_dwarf_unwind.c -o 
> ./test_dwarf_unwind

For whom want to test it: here is the test code I used.

#include <stdio.h>
#include <unistd.h>
#include <sys/time.h>

static volatile int x = 0;

int funcc(void)
{
     struct timeval tv1, tv2;
     unsigned long us1, us2;

     gettimeofday(&tv1, NULL);

     us1 = tv1.tv_sec * 1000000 + tv1.tv_usec;

     while(1) {
         x = x + 100;
         gettimeofday(&tv2, NULL);
         us2 = tv2.tv_sec * 1000000 + tv2.tv_usec;
         if (us2 - us1 >= 3000000)
             break;
     }
     return x;
}
int funcb(void) { return funcc();}
int funca(void) { return funcb();}
int main() { funca(); return 0;}



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