Messages in this thread Patch in this message | | | From | Namhyung Kim <> | Subject | [PATCH v2] perf tools: Allow build-id with trailing zeros | Date | Fri, 10 Sep 2021 15:46:30 -0700 |
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Current perf saves a build-id with size but old versions assumes the size of 20. In case the build-id is less than 20 (like for MD5), it'd fill the rest with 0s.
I saw a problem when old version of perf record saved a binary in the build-id cache and new version of perf reads the data. The symbols should be read from the build-id cache (as the path no longer has the same binary) but it failed due to mismatch in the build-id.
symsrc__init: build id mismatch for /home/namhyung/.debug/.build-id/53/e4c2f42a4c61a2d632d92a72afa08f00000000/elf.
The build-id event in the data has 20 byte build-ids, but it saw a different size (16) when it reads the build-id of the elf file in the build-id cache.
$ readelf -n ~/.debug/.build-id/53/e4c2f42a4c61a2d632d92a72afa08f00000000/elf
Displaying notes found in: .note.gnu.build-id Owner Data size Description GNU 0x00000010 NT_GNU_BUILD_ID (unique build ID bitstring) Build ID: 53e4c2f42a4c61a2d632d92a72afa08f
Let's fix this by allowing trailing zeros if the size is different.
Fixes: 39be8d0115b3 ("perf tools: Pass build_id object to dso__build_id_equal()")
Acked-by: Jiri Olsa <jolsa@redhat.com> Signed-off-by: Namhyung Kim <namhyung@kernel.org> --- tools/perf/util/dso.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c index ee15db2be2f4..9ed9a5676d35 100644 --- a/tools/perf/util/dso.c +++ b/tools/perf/util/dso.c @@ -1349,6 +1349,16 @@ void dso__set_build_id(struct dso *dso, struct build_id *bid) bool dso__build_id_equal(const struct dso *dso, struct build_id *bid) { + if (dso->bid.size > bid->size && dso->bid.size == BUILD_ID_SIZE) { + /* + * For the backward compatibility, it allows a build-id has + * trailing zeros. + */ + return !memcmp(dso->bid.data, bid->data, bid->size) && + !memchr_inv(&dso->bid.data[bid->size], 0, + dso->bid.size - bid->size); + } + return dso->bid.size == bid->size && memcmp(dso->bid.data, bid->data, dso->bid.size) == 0; } -- 2.33.0.309.g3052b89438-goog
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