From: Song Liu <songliubraving@fb.com>
To: <linux-kernel@vger.kernel.org>, <bpf@vger.kernel.org>,
<netdev@vger.kernel.org>
Cc: <ast@kernel.org>, <daniel@iogearbox.net>, <kernel-team@fb.com>,
<john.fastabend@gmail.com>, <kpsingh@chromium.org>,
<brouer@redhat.com>, <peterz@infradead.org>,
Song Liu <songliubraving@fb.com>
Subject: [PATCH v5 bpf-next 3/5] libbpf: print hint when PERF_EVENT_IOC_SET_BPF returns -EPROTO
Date: Thu, 23 Jul 2020 11:06:46 -0700 [thread overview]
Message-ID: <20200723180648.1429892-4-songliubraving@fb.com> (raw)
In-Reply-To: <20200723180648.1429892-1-songliubraving@fb.com>
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(+)
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) {
--
2.24.1
next prev parent reply other threads:[~2020-07-23 18:09 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-23 18:06 [PATCH v5 bpf-next 0/5] bpf: fix stackmap on perf_events with PEBS Song Liu
2020-07-23 18:06 ` [PATCH v5 bpf-next 1/5] bpf: separate bpf_get_[stack|stackid] for perf events BPF Song Liu
2020-07-23 18:06 ` [PATCH v5 bpf-next 2/5] bpf: fail PERF_EVENT_IOC_SET_BPF when bpf_get_[stack|stackid] cannot work Song Liu
2020-07-23 18:06 ` Song Liu [this message]
2020-07-23 18:06 ` [PATCH v5 bpf-next 4/5] selftests/bpf: add callchain_stackid Song Liu
2020-07-23 18:06 ` [PATCH v5 bpf-next 5/5] selftests/bpf: add get_stackid_cannot_attach Song Liu
2020-07-24 5:32 ` Alexei Starovoitov
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