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

Wang Nan
2015-04-30T10:58:06Z

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