linux-kernel - Re: [BUG] perf report: fails to symbolize when vaddr is non zero for shared objects

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Message-ID: <20150616143401.GA2548@redhat.com>
Date:	Tue, 16 Jun 2015 11:34:01 -0300
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, Jiri Olsa <jolsa@...hat.com>,
	Namhyung Kim <namhyung@...nel.org>,
	David Ahern <dsahern@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...e.hu" <mingo@...e.hu>
Subject: Re: [BUG] perf report: fails to symbolize when vaddr is non zero for
 shared objects

Em Tue, Jun 16, 2015 at 12:03:01AM -0700, Stephane Eranian escreveu:
> Hi,
> 
> It has been brought to my attention that on systems where the text
> of shared libs is not loaded with a zero virtual address, perf report
> fails to symbolize
> correctly samples. This is true of older versions of perf and also the latest
> in tip.git.
> 
> I looked at symbol-elf.c and I did not see a place where the vaddr was taken
> into account from the program headers in the case of ET_DYN. I see it for
> ET_EXE, though.
> 
> $ readelf -e lib.so
>   Type:                              DYN (Shared object file)
>   ....
>   Type          Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
>  LOAD           0x000000 0x0000d000 0x0000d000 0x73657c 0x73657c R E 0x1000
> 
> If you get samples in the shared lib, they will be off, possibly
> attributed to the wrong
> functions.
> 
> Could this be fixed quickly?

You tell me, do you have a patch to propose? :-)

- Arnaldo
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