linux-kernel - [PATCH 03/44] perf: Fix branch stack callchain limit

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Message-Id: <20251119224140.8616-4-david.laight.linux@gmail.com>
Date: Wed, 19 Nov 2025 22:40:59 +0000
From: david.laight.linux@...il.com
To: linux-kernel@...r.kernel.org,
	linux-perf-users@...r.kernel.org
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	David Laight <david.laight.linux@...il.com>
Subject: [PATCH 03/44] perf: Fix branch stack callchain limit

From: David Laight <david.laight.linux@...il.com>

The code that bounds the brs->nr to event->attr.sample_max_stack
incorrectly masks brs->nr with 65535 before the limit check.
Replace the min_t(u16, ...) with a plain min(...).

I guess there may be another limit on brs->nr (which is u64).

Fixes: c53e14f1ea4a8 ("perf: Extend per event callchain limit to branch stack")
Signed-off-by: David Laight <david.laight.linux@...il.com>
---
 include/linux/perf_event.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index fd1d91017b99..f91c875ea311 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1430,7 +1430,7 @@ static inline void perf_sample_save_brstack(struct perf_sample_data *data,
 	if (branch_sample_hw_index(event))
 		size += sizeof(u64);
 
-	brs->nr = min_t(u16, event->attr.sample_max_stack, brs->nr);
+	brs->nr = min(event->attr.sample_max_stack, brs->nr);
 
 	size += brs->nr * sizeof(struct perf_branch_entry);
 
-- 
2.39.5