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perf symbol: Skip symbols if SHF_ALLOC flag is not set

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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 <maskray@google.com>
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Chang Rui <changruinj@gmail.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220724060013.171050-3-leo.yan@linaro.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Leo Yan 2022-07-24 14:00:13 +08:00 committed by Arnaldo Carvalho de Melo
parent 2d86612aac
commit 882528d2e7
1 changed files with 11 additions and 0 deletions
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11
tools/perf/util/symbol-elf.c
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@ -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;
/*