perf lock contention: Rework offset calculation with BPF CO-RE

It seems BPF CO-RE reloc doesn't work well with the pattern that gets
the field-offset only.  Use offsetof() to make it explicit so that
the compiler would generate the correct code.

Fixes: 0c1228486befa3d6 ("perf lock contention: Support pre-5.14 kernels")
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Hao Luo <haoluo@google.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <song@kernel.org>
Cc: bpf@vger.kernel.org
Co-developed-by: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Link: https://lore.kernel.org/r/20230427234833.1576130-2-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c
index 30c1930..8d3cfbb 100644 (file)
--- a/tools/perf/util/bpf_skel/lock_contention.bpf.c
+++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c
@@ -429,21 +429,21 @@ struct rq___new {
 SEC("raw_tp/bpf_test_finish")
 int BPF_PROG(collect_lock_syms)
 {
-       __u64 lock_addr;
+       __u64 lock_addr, lock_off;
        __u32 lock_flag;
 
+       if (bpf_core_field_exists(struct rq___new, __lock))
+               lock_off = offsetof(struct rq___new, __lock);
+       else
+               lock_off = offsetof(struct rq___old, lock);
+
        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;
 
-               if (bpf_core_field_exists(rq_new->__lock))
-                       lock_addr = (__u64)&rq_new->__lock;
-               else
-                       lock_addr = (__u64)&rq_old->lock;
+               lock_addr = (__u64)(void *)rq + lock_off;
                lock_flag = LOCK_CLASS_RQLOCK;
                bpf_map_update_elem(&lock_syms, &lock_addr, &lock_flag, BPF_ANY);
        }