[PATCH 1/3] perf cs-etm: Initialize the Thumb instruction buffer

[Leo Yan <leo.yan@arm.com>]

cs_etm__frontend_mem_access() can return zero or a short read without
fully initializing instrBytes. cs_etm__t32_instr_size() nevertheless
inspects its second byte. With CORESIGHT=1 and -O3, GCC 15.2.0 reports:

  error: 'instrBytes' may be used uninitialized

Zero-initialize the buffer to avoid reading uninitialized stack data
when instruction memory is unavailable and fix the build failure.

Reported-by: Ian Rogers <irogers@google.com>
Closes: https://lore.kernel.org/linux-perf-users/20261030-perf_cs_etm_fix_non_taken-v3-0-7629b52ab047@arm.com/T/#m64fb81c665214b79883d9be815b40ac5f6669628
Fixes: a7ee4d625ede ("perf cs-etm: Support for ARM A32/T32 instruction sets in CoreSight trace")
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/perf/util/cs-etm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
index 3e01b401ca6f3a08f44bb69204317efaf2fa18d0..25f12bd110934a204d79244f45317085b7a81666 100644
--- a/tools/perf/util/cs-etm.c
+++ b/tools/perf/util/cs-etm.c
@@ -1369,7 +1369,7 @@ static inline int cs_etm__t32_instr_size(struct cs_etm_queue *etmq,
 					 struct cs_etm_traceid_queue *tidq,
 					 struct cs_etm_packet *packet, u64 addr)
 {
-	u8 instrBytes[2];
+	u8 instrBytes[2] = { 0 };
 
 	cs_etm__frontend_mem_access(etmq, tidq, packet, addr,
 				    ARRAY_SIZE(instrBytes), instrBytes);

-- 
2.34.1