[PATCH v1] perf symbol: Fix ENOENT case for filename__read_build_id

[Ian Rogers <irogers@google.com>]

Some callers of filename__read_build_id assume the error value must be
-1, fix by making them handle all < 0 values.

If is_regular_file fails in filename__read_build_id then it could be
the file is missing (ENOENT) and it would be wrong to return
-EWOULDBLOCK in that case. Fix the logic so -EWOULDBLOCK is only
reported if other errors with stat haven't occurred.

Fixes: 834ebb5678d7 ("perf tools: Don't read build-ids from non-regular files")
Signed-off-by: Ian Rogers <irogers@google.com>
---
Note, a shorter version of this patch appeared in a series
cleaning/refactoring the build id reading code:
https://lore.kernel.org/lkml/20251201205509.195451-11-irogers@google.com/
It is sent without the refactor for the sake of fixing the bug in an
earlier release.
---
 tools/perf/builtin-buildid-cache.c | 6 ++++--
 tools/perf/util/libbfd.c           | 4 +++-
 tools/perf/util/symbol-elf.c       | 4 +++-
 tools/perf/util/symbol-minimal.c   | 4 +++-
 4 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/tools/perf/builtin-buildid-cache.c b/tools/perf/builtin-buildid-cache.c
index c98104481c8a..539e779e3268 100644
--- a/tools/perf/builtin-buildid-cache.c
+++ b/tools/perf/builtin-buildid-cache.c
@@ -276,12 +276,14 @@ static bool dso__missing_buildid_cache(struct dso *dso, int parm __maybe_unused)
 {
 	char filename[PATH_MAX];
 	struct build_id bid = { .size = 0, };
+	int err;
 
 	if (!dso__build_id_filename(dso, filename, sizeof(filename), false))
 		return true;
 
-	if (filename__read_build_id(filename, &bid) == -1) {
-		if (errno == ENOENT)
+	err = filename__read_build_id(filename, &bid);
+	if (err < 0) {
+		if (err == -ENOENT)
 			return false;
 
 		pr_warning("Problems with %s file, consider removing it from the cache\n",
diff --git a/tools/perf/util/libbfd.c b/tools/perf/util/libbfd.c
index 0099b415decc..edf0829e9635 100644
--- a/tools/perf/util/libbfd.c
+++ b/tools/perf/util/libbfd.c
@@ -391,8 +391,10 @@ int libbfd__read_build_id(const char *filename, struct build_id *bid)
 
 	if (!filename)
 		return -EFAULT;
+
+	errno = 0;
 	if (!is_regular_file(filename))
-		return -EWOULDBLOCK;
+		return errno == 0 ? -EWOULDBLOCK : -errno;
 
 	fd = open(filename, O_RDONLY);
 	if (fd < 0)
diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index 957143fbf8a0..d1dcafa4b3b8 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -902,8 +902,10 @@ int filename__read_build_id(const char *filename, struct build_id *bid)
 
 	if (!filename)
 		return -EFAULT;
+
+	errno = 0;
 	if (!is_regular_file(filename))
-		return -EWOULDBLOCK;
+		return errno == 0 ? -EWOULDBLOCK : -errno;
 
 	err = kmod_path__parse(&m, filename);
 	if (err)
diff --git a/tools/perf/util/symbol-minimal.c b/tools/perf/util/symbol-minimal.c
index c6b17c14a2e9..8221dc9868f7 100644
--- a/tools/perf/util/symbol-minimal.c
+++ b/tools/perf/util/symbol-minimal.c
@@ -104,8 +104,10 @@ int filename__read_build_id(const char *filename, struct build_id *bid)
 
 	if (!filename)
 		return -EFAULT;
+
+	errno = 0;
 	if (!is_regular_file(filename))
-		return -EWOULDBLOCK;
+		return errno == 0 ? -EWOULDBLOCK : -errno;
 
 	fd = open(filename, O_RDONLY);
 	if (fd < 0)
-- 
2.52.0.223.gf5cc29aaa4-goog