| Message ID | 1454403366-27055-3-git-send-email-wangnan0@huawei.com |
|---|---|
| State | New |
| Headers | show |
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 >>
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 || dso__is_vdso(dso) || elf_section_by_name(elf, &ehdr, &shdr, ".gnu.prelink_undo",
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); 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(+) -- 1.8.3.4