From 24a026e4ae1d7a9f7889d2ce6202be3e1ea6a3c0 Mon Sep 17 00:00:00 2001 From: Namhyung Kim Date: Fri, 10 Sep 2021 15:46:30 -0700 Subject: [PATCH] perf tools: Allow build-id with trailing zeros commit 4a86d41404005a3c7e7b6065e8169ac6202887a9 upstream. 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: .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: 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: http://lore.kernel.org/lkml/20210910224630.1084877-1-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Greg Kroah-Hartman --- 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 ee15db2be2f43..9ed9a5676d352 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; }