From 99e87f7bb7268cf644add87130590966fd5d0d17 Mon Sep 17 00:00:00 2001 From: Wang Nan Date: Thu, 7 Apr 2016 10:24:31 +0000 Subject: [PATCH] perf symbols: Adjust symbol for shared objects 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 skipping adjustment is okay. However, 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. Now nearly all types of ELF files should adjust symbols. Makes ss->adjust_symbols default to true. Steps to reproduce the problem: $ cat ./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 $ cat ./buggy.c int fib(int x) { return (x == 0) ? 1 : (x == 1) ? 1 : fib(x - 1) + fib(x - 2); } $ cat ./main.c #include extern int fib(int x); int main() { int i; for (i = 0; i < 40; i++) printf("%d\n", fib(i)); return 0; } $ 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 Acked-by: Namhyung Kim Tested-by: Arnaldo Carvalho de Melo Cc: Adrian Hunter Cc: Cody P Schafer Cc: He Kuang Cc: Jiri Olsa Cc: Kirill Smelkov Cc: Li Zefan Cc: Masami Hiramatsu Cc: Zefan Li Cc: pi3orama@163.com Link: http://lkml.kernel.org/r/1460024671-64774-3-git-send-email-wangnan0@huawei.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/symbol-elf.c | 13 +++---------- 1 file changed, 3 insertions(+), 10 deletions(-) diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c index bc229a74c6a9..3f9d6798bd18 100644 --- a/tools/perf/util/symbol-elf.c +++ b/tools/perf/util/symbol-elf.c @@ -709,17 +709,10 @@ int symsrc__init(struct symsrc *ss, struct dso *dso, const char *name, if (ss->opdshdr.sh_type != SHT_PROGBITS) ss->opdsec = NULL; - if (dso->kernel == DSO_TYPE_USER) { - GElf_Shdr shdr; - ss->adjust_symbols = (ehdr.e_type == ET_EXEC || - ehdr.e_type == ET_REL || - dso__is_vdso(dso) || - elf_section_by_name(elf, &ehdr, &shdr, - ".gnu.prelink_undo", - NULL) != NULL); - } else { + if (dso->kernel == DSO_TYPE_USER) + ss->adjust_symbols = true; + else ss->adjust_symbols = elf__needs_adjust_symbols(ehdr); - } ss->name = strdup(name); if (!ss->name) { -- 2.11.0