linux-kernel - [PATCH v2] perf lock contention: Fix builtin detection

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Date:   Tue,  7 Mar 2023 16:30:20 -0800
From:   Ian Rogers <irogers@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Martin KaFai Lau <martin.lau@...nel.org>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org
Subject: [PATCH v2] perf lock contention: Fix builtin detection

__has_builtin was passed the macro rather than the actual builtin
feature. The builtin test isn't sufficient and a clang version test
also needs to be performed.

Fixes: 1bece1351c65 ("perf lock contention: Support old rw_semaphore type")
Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/util/bpf_skel/lock_contention.bpf.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c
index e6007eaeda1a..141b36d13b19 100644
--- a/tools/perf/util/bpf_skel/lock_contention.bpf.c
+++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c
@@ -182,7 +182,13 @@ static inline struct task_struct *get_lock_owner(__u64 lock, __u32 flags)
 		struct mutex *mutex = (void *)lock;
 		owner = BPF_CORE_READ(mutex, owner.counter);
 	} else if (flags == LCB_F_READ || flags == LCB_F_WRITE) {
-#if __has_builtin(bpf_core_type_matches)
+	/*
+	 * Support for the BPF_TYPE_MATCHES argument to the
+	 * __builtin_preserve_type_info builtin was added at some point during
+	 * development of clang 15 and it's what is needed for
+	 * bpf_core_type_matches.
+	 */
+#if __has_builtin(__builtin_preserve_type_info) && __clang_major__ >= 15
 		if (bpf_core_type_matches(struct rw_semaphore___old)) {
 			struct rw_semaphore___old *rwsem = (void *)lock;
 			owner = (unsigned long)BPF_CORE_READ(rwsem, owner);
-- 
2.40.0.rc0.216.gc4246ad0f0-goog