| Message ID | 20200723180648.1429892-4-songliubraving@fb.com |
|---|---|
| State | Accepted |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | bpf: fix stackmap on perf_events with PEBS | expand |
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 846164c79df1c..484e50d49a4cf 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -7833,6 +7833,9 @@ struct bpf_link *bpf_program__attach_perf_event(struct bpf_program *prog, pr_warn("program '%s': failed to attach to pfd %d: %s\n", bpf_program__title(prog, false), pfd, libbpf_strerror_r(err, errmsg, sizeof(errmsg))); + if (err == -EPROTO) + pr_warn("program '%s': try add PERF_SAMPLE_CALLCHAIN to or remove exclude_callchain_[kernel|user] from pfd %d\n", + bpf_program__title(prog, false), pfd); return ERR_PTR(err); } if (ioctl(pfd, PERF_EVENT_IOC_ENABLE, 0) < 0) {
The kernel prevents potential unwinder warnings and crashes by blocking BPF program with bpf_get_[stack|stackid] on perf_event without PERF_SAMPLE_CALLCHAIN, or with exclude_callchain_[kernel|user]. Print a hint message in libbpf to help the user debug such issues. Signed-off-by: Song Liu <songliubraving@fb.com> --- tools/lib/bpf/libbpf.c | 3 +++ 1 file changed, 3 insertions(+)