diff options
authorNamhyung Kim <>2021-09-10 15:46:30 -0700
committerArnaldo Carvalho de Melo <>2021-09-11 16:04:47 -0300
commit4a86d41404005a3c7e7b6065e8169ac6202887a9 (patch)
parent99fc5941b835d662eb2e91d8b61249e9a51df9f0 (diff)
perf tools: Allow build-id with trailing zeros
Currently 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: 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: 39be8d0115b321ed ("perf tools: Pass build_id object to dso__build_id_equal()") Signed-off-by: Namhyung Kim <> Acked-by: Jiri Olsa <> Cc: Andi Kleen <> Cc: Ian Rogers <> Cc: Peter Zijlstra <> Link: Signed-off-by: Arnaldo Carvalho de Melo <>
1 files changed, 10 insertions, 0 deletions
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->size) &&
+ !memchr_inv(&dso->[bid->size], 0,
+ dso->bid.size - bid->size);
+ }
return dso->bid.size == bid->size &&
memcmp(dso->, bid->data, dso->bid.size) == 0;