From 6f520ce17920b3cdfbd2479b3ccf27f9706219d0 Mon Sep 17 00:00:00 2001 From: Ajay Kaher Date: Wed, 23 Nov 2022 15:48:16 +0530 Subject: [PATCH] perf symbol: correction while adjusting symbol perf doesn't provide proper symbol information for specially crafted .debug files. Sometimes .debug file may not have similar program header as runtime ELF file. For example if we generate .debug file using objcopy --only-keep-debug resulting file will not contain .text, .data and other runtime sections. That means corresponding program headers will have zero FileSiz and modified Offset. Example: program header of text section of libxxx.so: Type Offset VirtAddr PhysAddr FileSiz MemSiz Flags Align LOAD 0x00000000003d3000 0x00000000003d3000 0x00000000003d3000 0x000000000055ae80 0x000000000055ae80 R E 0x1000 Same program header after executing: objcopy --only-keep-debug libxxx.so libxxx.so.debug LOAD 0x0000000000001000 0x00000000003d3000 0x00000000003d3000 0x0000000000000000 0x000000000055ae80 R E 0x1000 Offset and FileSiz have been changed. Following formula will not provide correct value, if program header taken from .debug file (syms_ss): sym.st_value -= phdr.p_vaddr - phdr.p_offset; Correct program header information is located inside runtime ELF file (runtime_ss). Fixes: 2d86612aacb7805f ("perf symbol: Correct address for bss symbols") Signed-off-by: Ajay Kaher Cc: Alexander Shishkin Cc: Alexey Makhalov Cc: Jiri Olsa Cc: Leo Yan Cc: Mark Rutland Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Srivatsa S. Bhat Cc: Steven Rostedt (VMware) Cc: Vasavi Sirnapalli Link: http://lore.kernel.org/lkml/1669198696-50547-1-git-send-email-akaher@vmware.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/symbol-elf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c index 647b7df..8034569 100644 --- a/tools/perf/util/symbol-elf.c +++ b/tools/perf/util/symbol-elf.c @@ -1303,7 +1303,7 @@ dso__load_sym_internal(struct dso *dso, struct map *map, struct symsrc *syms_ss, (!used_opd && syms_ss->adjust_symbols)) { GElf_Phdr phdr; - if (elf_read_program_header(syms_ss->elf, + if (elf_read_program_header(runtime_ss->elf, (u64)sym.st_value, &phdr)) { pr_debug4("%s: failed to find program header for " "symbol: %s st_value: %#" PRIx64 "\n", -- 2.7.4