From b9f82b5c63bf5390da19e879275a792a959a8dac Mon Sep 17 00:00:00 2001 From: Namhyung Kim Date: Thu, 27 Apr 2023 16:48:33 -0700 Subject: [PATCH 1/1] 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 Acked-by: Ian Rogers Cc: Adrian Hunter Cc: Andrii Nakryiko Cc: Hao Luo Cc: Ian Rogers Cc: Ingo Molnar Cc: Jiri Olsa Cc: Peter Zijlstra Cc: Song Liu Cc: bpf@vger.kernel.org Co-developed-by: Andrii Nakryiko Link: https://lore.kernel.org/r/20230427234833.1576130-2-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/bpf_skel/lock_contention.bpf.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) 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 --- 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); } -- 2.7.4