This is a note to let you know that I've just added the patch titled perf tools: Allow build-id with trailing zeros to the 5.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: perf-tools-allow-build-id-with-trailing-zeros.patch and it can be found in the queue-5.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 4a86d41404005a3c7e7b6065e8169ac6202887a9 Mon Sep 17 00:00:00 2001 From: Namhyung Kim <namhyung@xxxxxxxxxx> Date: Fri, 10 Sep 2021 15:46:30 -0700 Subject: perf tools: Allow build-id with trailing zeros From: Namhyung Kim <namhyung@xxxxxxxxxx> 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 <namhyung@xxxxxxxxxx> Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx> Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx> Cc: Ian Rogers <irogers@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Link: http://lore.kernel.org/lkml/20210910224630.1084877-1-namhyung@xxxxxxxxxx Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- tools/perf/util/dso.c | 10 ++++++++++ 1 file changed, 10 insertions(+) --- a/tools/perf/util/dso.c +++ b/tools/perf/util/dso.c @@ -1349,6 +1349,16 @@ void dso__set_build_id(struct dso *dso, 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; } Patches currently in stable-queue which might be from namhyung@xxxxxxxxxx are queue-5.14/perf-tools-allow-build-id-with-trailing-zeros.patch queue-5.14/perf-symbol-look-for-imagebase-in-pe-file-to-compute-.text-offset.patch