perf lock contention: Support pre-5.14 kernels

'struct rq's member '__lock' was renamed from 'lock' in 5.14.
Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20230408055208.1283832-1-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/bpf_skel/lock_contention.bpf.c

@@ -418,6 +418,14 @@ int contention_end(u64 *ctx)
 
 extern struct rq runqueues __ksym;
 
+struct rq__old {
+	raw_spinlock_t lock;
+} __attribute__((preserve_access_index));
+
+struct rq__new {
+	raw_spinlock_t __lock;
+} __attribute__((preserve_access_index));
+
 SEC("raw_tp/bpf_test_finish")
 int BPF_PROG(collect_lock_syms)
 {
@@ -426,11 +434,16 @@ int BPF_PROG(collect_lock_syms)
 
 	for (int i = 0; i < MAX_CPUS; i++) {
 		struct rq *rq = bpf_per_cpu_ptr(&runqueues, i);
+		struct rq__new *rq_new = (void *)rq;
+		struct rq__old *rq_old = (void *)rq;
 
 		if (rq == NULL)
 			break;
 
-		lock_addr = (__u64)&rq->__lock;
+		if (bpf_core_field_exists(rq_new->__lock))
+			lock_addr = (__u64)&rq_new->__lock;
+		else
+			lock_addr = (__u64)&rq_old->lock;
 		lock_flag = LOCK_CLASS_RQLOCK;
 		bpf_map_update_elem(&lock_syms, &lock_addr, &lock_flag, BPF_ANY);
 	}