lkml.org 
[lkml]   [2016]   [Feb]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 2/2] perf tools: Adjust symbol for shared objects
From
Date


On 2016/2/2 23:18, Namhyung Kim wrote:
> On Tue, Feb 02, 2016 at 08:56:06AM +0000, Wang Nan wrote:
>> He Kuang reported a problem that perf fails to get correct symbol on
>> Android platform in [1]. The problem can be reproduced on normal x86_64
>> platform. I will describe the reproducing steps in detail at the end of
>> commit message.
>>
>> The reason of this problem is the missing of symbol adjustment for normal
>> shared objects. In most of the cases it works correctly, but when
>> '.text' section have different 'address' and 'offset' the result is
>> wrong. I checked all shared objects in my working platform, only wine
>> dll objects and debug objects (in .debug) have this problem. However,
>> it is common on Android. For example:
>>
>> $ readelf -S ./libsurfaceflinger.so | grep \.text
>> [10] .text PROGBITS 0000000000029030 00012030
>>
>> This patch enables symbol adjustment for dynamic objects so the symbol
>> address got from elfutils would be adjusted correctly.
>>
>> Steps to reproduce the problem:
>>
>> $ cat << EOF > ./Makefile
>> PWD := $(shell pwd)
>> LDFLAGS += "-Wl,-rpath=$(PWD)"
>> CFLAGS += -g
>> main: main.c libbuggy.so
>> libbuggy.so: buggy.c
>> gcc -g -shared -fPIC -Wl,-Ttext-segment=0x200000 $< -o $@
>> clean:
>> rm -rf main libbuggy.so *.o
>> EOF
>>
>> $ cat << EOF > ./buggy.c
>> int fib(int x)
>> {
>> return (x == 0) ? 1 : (x == 1) ? 1 : fib(x - 1) + fib(x - 2);
>> }
>> EOF
>>
>> $ cat << EOF > ./main.c
>> #include <stdio.h>
>>
>> extern int fix(int x);
> s/fix/fib/ ?

Thank you. Have you really tested this program?

>> int main()
>> {
>> int i;
>>
>> for (i = 0; i < 40; i++)
>> printf("%d\n", fib(i));
>> return 0;
>> }
>> EOF
>>
>> $ make
>> $ perf record ./main
>> ...
>> $ perf report --stdio
>> # Overhead Command Shared Object Symbol
>> # ........ ....... ................. ...............................
>> #
>> 14.97% main libbuggy.so [.] 0x000000000000066c
>> 8.68% main libbuggy.so [.] 0x00000000000006aa
>> 8.52% main libbuggy.so [.] fib@plt
>> 7.95% main libbuggy.so [.] 0x0000000000000664
>> 5.94% main libbuggy.so [.] 0x00000000000006a9
>> 5.35% main libbuggy.so [.] 0x0000000000000678
>> ...
>>
>> The correct result should be (after this patch):
>>
>> # Overhead Command Shared Object Symbol
>> # ........ ....... ................. ...............................
>> #
>> 91.47% main libbuggy.so [.] fib
>> 8.52% main libbuggy.so [.] fib@plt
>> 0.00% main [kernel.kallsyms] [k] kmem_cache_free
>>
>> [1] http://lkml.kernel.org/g/1452567507-54013-1-git-send-email-hekuang@huawei.com
>>
>> Signed-off-by: Wang Nan <wangnan0@huawei.com>
>> Cc: Adrian Hunter <adrian.hunter@intel.com>
>> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
>> Cc: Cody P Schafer <dev@codyps.com>
>> Cc: He Kuang <hekuang@huawei.com>
>> Cc: Jiri Olsa <jolsa@kernel.org>
>> Cc: Kirill Smelkov <kirr@nexedi.com>
>> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
>> Cc: Namhyung Kim <namhyung@kernel.org>
>> Cc: Li Zefan <lizefan@huawei.com>
>> Cc: pi3orama@163.com
>> ---
>> tools/perf/util/symbol-elf.c | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
>> index 5227186..d4e59dd 100644
>> --- a/tools/perf/util/symbol-elf.c
>> +++ b/tools/perf/util/symbol-elf.c
>> @@ -712,6 +712,7 @@ int symsrc__init(struct symsrc *ss, struct dso *dso, const char *name,
>> GElf_Shdr shdr;
>> ss->adjust_symbols = (ehdr.e_type == ET_EXEC ||
>> ehdr.e_type == ET_REL ||
>> + ehdr.e_type == ET_DYN ||
> It seems there's no need to check the e_type anymore..

OK. Let's make adjust_symbols the default choice.

Thank you.

> Thanks,
> Namhyung
>
>
>> dso__is_vdso(dso) ||
>> elf_section_by_name(elf, &ehdr, &shdr,
>> ".gnu.prelink_undo",
>> --
>> 1.8.3.4
>>


\
 
 \ /
  Last update: 2016-02-03 04:01    [W:0.080 / U:0.720 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site