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Date: Sun, 24 Jul 2022 14:00:13 +0800 From: Leo Yan <leo.yan@...aro.org> To: Arnaldo Carvalho de Melo <acme@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, Mark Rutland <mark.rutland@....com>, Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>, Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Ian Rogers <irogers@...gle.com>, Fangrui Song <maskray@...gle.com>, Chang Rui <changruinj@...il.com>, linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org Cc: Leo Yan <leo.yan@...aro.org> Subject: [PATCH v3 2/2] perf symbol: Skip symbols if SHF_ALLOC flag is not set Some symbols are observed the 'st_value' field are zeros. 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 <maskray@...gle.com> Signed-off-by: Leo Yan <leo.yan@...aro.org> --- 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 ef6ced5c5746..b3be5b1d9dbb 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; /* -- 2.25.1
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