[PATCH v1 1/2] perf evsel: Ensure the fallback message is always written to
From: Ian Rogers
Date: Thu Sep 18 2025 - 13:24:19 EST
The fallback message is unconditionally printed in places like
record__open. If no fallback is attempted this can lead to printing
uninitialized data, crashes, etc.
Fixes: c0a54341c0e8 ("perf evsel: Introduce event fallback method")
Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
tools/perf/util/evsel.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 477cddf08c5c..814ef6f6b32a 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -3565,7 +3565,7 @@ bool evsel__fallback(struct evsel *evsel, struct target *target, int err,
/* If event has exclude user then don't exclude kernel. */
if (evsel->core.attr.exclude_user)
- return false;
+ goto no_fallback;
/* Is there already the separator in the name. */
if (strchr(name, '/') ||
@@ -3573,7 +3573,7 @@ bool evsel__fallback(struct evsel *evsel, struct target *target, int err,
sep = "";
if (asprintf(&new_name, "%s%su", name, sep) < 0)
- return false;
+ goto no_fallback;
free(evsel->name);
evsel->name = new_name;
@@ -3596,17 +3596,19 @@ bool evsel__fallback(struct evsel *evsel, struct target *target, int err,
sep = "";
if (asprintf(&new_name, "%s%sH", name, sep) < 0)
- return false;
+ goto no_fallback;
free(evsel->name);
evsel->name = new_name;
/* Apple M1 requires exclude_guest */
- scnprintf(msg, msgsize, "trying to fall back to excluding guest samples");
+ scnprintf(msg, msgsize, "Trying to fall back to excluding guest samples");
evsel->core.attr.exclude_guest = 1;
return true;
}
-
+no_fallback:
+ scnprintf(msg, msgsize, "No fallback found for '%s' for error %d",
+ evsel__name(evsel), err);
return false;
}
--
2.51.0.470.ga7dc726c21-goog