From 882528d2e77687c3ef26abb9c490f77a9c1f6e1a Mon Sep 17 00:00:00 2001 From: Leo Yan Date: Sun, 24 Jul 2022 14:00:13 +0800 Subject: [PATCH] perf symbol: Skip symbols if SHF_ALLOC flag is not set Some symbols are observed with the 'st_value' field zeroed. E.g. libc.so.6 in Ubuntu contains a symbol '__evoke_link_warning_getwd' which resides in the '.gnu.warning.getwd' section. Unlike normal sections, such kind of sections are used for linker warning when a file calls deprecated functions, but they are not part of memory images, the symbols in these sections should be dropped. This patch checks the section attribute SHF_ALLOC bit, if the bit is not set, it skips symbols to avoid spurious ones. Suggested-by: Fangrui Song Signed-off-by: Leo Yan Acked-by: Namhyung Kim Cc: Alexander Shishkin Cc: Chang Rui Cc: Ian Rogers Cc: Ingo Molnar Cc: Jiri Olsa Cc: Mark Rutland Cc: Peter Zijlstra Link: https://lore.kernel.org/r/20220724060013.171050-3-leo.yan@linaro.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/symbol-elf.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c index ef6ced5..b3be5b1 100644 --- a/tools/perf/util/symbol-elf.c +++ b/tools/perf/util/symbol-elf.c @@ -1255,6 +1255,17 @@ dso__load_sym_internal(struct dso *dso, struct map *map, struct symsrc *syms_ss, gelf_getshdr(sec, &shdr); + /* + * If the attribute bit SHF_ALLOC is not set, the section + * doesn't occupy memory during process execution. + * E.g. ".gnu.warning.*" section is used by linker to generate + * warnings when calling deprecated functions, the symbols in + * the section aren't loaded to memory during process execution, + * so skip them. + */ + if (!(shdr.sh_flags & SHF_ALLOC)) + continue; + secstrs = secstrs_sym; /* -- 2.7.4