linux-kernel - [RFC PATCH v10 36/50] perf tools: Attach eBPF program to perf event

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Date:	Wed, 1 Jul 2015 02:14:24 +0000
From:	Wang Nan <wangnan0@...wei.com>
To:	<acme@...nel.org>, <ast@...mgrid.com>, <brendan.d.gregg@...il.com>,
	<daniel@...earbox.net>, <namhyung@...nel.org>,
	<masami.hiramatsu.pt@...achi.com>, <paulus@...ba.org>,
	<a.p.zijlstra@...llo.nl>, <mingo@...hat.com>, <jolsa@...nel.org>,
	<dsahern@...il.com>
CC:	<linux-kernel@...r.kernel.org>, <lizefan@...wei.com>,
	<hekuang@...wei.com>, <xiakaixu@...wei.com>, <pi3orama@....com>
Subject: [RFC PATCH v10 36/50] perf tools: Attach eBPF program to perf event

In this patch PERF_EVENT_IOC_SET_BPF ioctl is used to attach eBPF
program to a newly created perf event. The file descriptor of the
eBPF program is passed to perf record using previous patches, and
stored into evsel->bpf_fd.

It is possible that different perf event are created for one kprobe
events for different CPUs. In this case, when trying to call the
ioctl, EEXIST will be return. This patch doesn't treat it as an error.

Signed-off-by: Wang Nan <wangnan0@...wei.com>
---
 tools/perf/util/evsel.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 4767ad6..3a33338 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1185,6 +1185,22 @@ retry_open:
 					  err);
 				goto try_fallback;
 			}
+
+			if (evsel->bpf_fd >= 0) {
+				int evt_fd = FD(evsel, cpu, thread);
+				int bpf_fd = evsel->bpf_fd;
+
+				err = ioctl(evt_fd,
+					    PERF_EVENT_IOC_SET_BPF,
+					    bpf_fd);
+				if (err && errno != EEXIST) {
+					pr_err("failed to attach bpf fd %d: %s\n",
+					       bpf_fd, strerror(errno));
+					err = -EINVAL;
+					goto out_close;
+				}
+			}
+
 			set_rlimit = NO_CHANGE;
 
 			/*
-- 
1.8.3.4

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