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;
}
