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>
---
 tools/perf/builtin-buildid-cache.c | 6 ++++--
 tools/perf/util/symbol.c           | 3 ++-
 2 files changed, 6 insertions(+), 3 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/symbol.c b/tools/perf/util/symbol.c
index 76dc5b70350a..f43e30019e21 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -2008,8 +2008,9 @@ 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)
-- 
2.52.0.158.g65b55ccf14-goog