[RFC PATCH 22/22] perf bpf: attaches eBPF program to perf fd.

[Wang Nan <wangnan0@huawei.com>]

This patch does the final work whcih makes eBPF program actually work.
It introduces bpf_attach(), which first retrive id field of previous
created k(ret)probe events, then use PERF_EVENT_IOC_SET_BPF to attach
eBPF program to the events.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
---
 tools/perf/util/bpf-loader.c | 82 ++++++++++++++++++++++++++++++++++++++++++++
 tools/perf/util/bpf-loader.h |  2 ++
 2 files changed, 84 insertions(+)

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index 186a3d0..c646ca4 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -15,6 +15,7 @@
 #include "bpf-loader.h"
 #include "probe-event.h"
 #include "probe-finder.h" // for MAX_PROBES
+#include "trace-event.h"
 
 #include <linux/list.h>
 #include <linux/types.h>
@@ -326,6 +327,8 @@ bpf_perf_prog_free(struct bpf_perf_prog *prog)
 	}
 	if (prog->prog_fd >= 0)
 		close(prog->prog_fd);
+	if (prog->perf_fd >= 0)
+		close(prog->perf_fd);
 	free(prog);
 }
 
@@ -375,6 +378,8 @@ bpf_perf_prog_alloc(struct bpf_obj *obj __maybe_unused,
 		prog->insns_cnt * sizeof(struct bpf_insn));
 	prog->idx = idx;
 	prog->prog_fd = -1;
+	prog->event_id = -1;
+	prog->perf_fd = -1;
 	return prog;
 out:
 	bpf_perf_prog_free(prog);
@@ -964,6 +969,81 @@ static int bpf_probe(void)
 	return err < 0 ? err : 0;
 }
 
+static int bpf_perf_prog_attach(struct bpf_perf_prog *prog)
+{
+	struct event_format* format;
+	struct perf_event_attr attr;
+	int fd, err;
+
+	format = trace_event__tp_format(prog->pev->group,
+					prog->pev->event);
+	if (!format) {
+		pr_err("bpf: attach: failed to get format of %s/%s\n",
+			prog->pev->group, prog->pev->event);
+		return -EINVAL;
+	}
+
+	pr_debug("bpf: attach %s/%s: id=%d\n",
+			prog->pev->group,
+			prog->pev->event,
+			format->id);
+	prog->event_id = format->id;
+
+	pevent_free_format(format);
+
+	memset(&attr, '\0', sizeof(attr));
+
+	attr.type = PERF_TYPE_TRACEPOINT;
+	attr.sample_type = PERF_SAMPLE_RAW;
+	attr.sample_period = 1;
+	attr.wakeup_events = 1;
+	attr.config = prog->event_id;
+
+	fd = sys_perf_event_open(&attr, -1, 0, -1, 0);
+	if (fd < 0) {
+		pr_err("bpf: open event %d failed\n", prog->event_id);
+		return -errno;
+	}
+	prog->perf_fd = fd;
+
+	err = ioctl(fd, PERF_EVENT_IOC_ENABLE, 0);
+	if (err) {
+		pr_err("bpf attach: enable failed: %s\n",
+			strerror(errno));
+		return -errno;
+	}
+
+	err = ioctl(fd, PERF_EVENT_IOC_SET_BPF, prog->prog_fd);
+	if (err) {
+		pr_err("bpf attach: set bpf: %s\n", strerror(errno));
+		return -errno;
+	}
+	pr_debug("bpf: attach %s to event %d\n", prog->name,
+			prog->event_id);
+
+	return 0;
+}
+
+static int bpf_attach(void)
+{
+	struct bpf_obj *obj;
+	int err;
+
+	list_for_each_entry(obj, &bpf_obj_list, list) {
+		struct bpf_perf_prog *prog;
+
+		list_for_each_entry(prog, &obj->progs_list, list) {
+			err = bpf_perf_prog_attach(prog);
+			if (err) {
+				pr_err("bpf: attach: faied to attach %s\n",
+					prog->name);
+				return err;
+			}
+		}
+	}
+	return 0;
+}
+
 int bpf__run(void)
 {
 	int err;
@@ -971,6 +1051,8 @@ int bpf__run(void)
 	pr_debug("bpf: probing\n");
 	if ((err = bpf_probe()))
 		return err;
+	if ((err = bpf_attach()))
+		return err;
 
 	pr_info("BPF is running. Use Ctrl-c to stop.\n");
 	while(1)
diff --git a/tools/perf/util/bpf-loader.h b/tools/perf/util/bpf-loader.h
index dfdc3ca..baa4404 100644
--- a/tools/perf/util/bpf-loader.h
+++ b/tools/perf/util/bpf-loader.h
@@ -32,6 +32,8 @@ struct bpf_perf_prog {
 
 	/* fd of loaded eBPF program */
 	int prog_fd;
+	int event_id;
+	int perf_fd;
 };
 
 struct bpf_obj {
-- 
1.8.3.4