Automatically enabling a perf event after attaching a BPF prog to it is
not always desirable.
Add a new "dont_enable" field to struct bpf_perf_event_opts. While
introducing "enable" instead would be nicer in that it would avoid
a double negation in the implementation, it would make
DECLARE_LIBBPF_OPTS() less efficient.
Acked-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
Suggested-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Tested-by: Thomas Richter <tmricht@xxxxxxxxxxxxx>
Co-developed-by: Thomas Richter <tmricht@xxxxxxxxxxxxx>
Signed-off-by: Thomas Richter <tmricht@xxxxxxxxxxxxx>
Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
---
tools/lib/bpf/libbpf.c | 13 ++++++++-----
tools/lib/bpf/libbpf.h | 4 +++-
2 files changed, 11 insertions(+), 6 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index fb4d92c5c339..8f5a81b672e1 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -10965,11 +10965,14 @@ struct bpf_link *bpf_program__attach_perf_event_opts(const struct bpf_program *p
}
link->link.fd = pfd;
}
- if (ioctl(pfd, PERF_EVENT_IOC_ENABLE, 0) < 0) {
- err = -errno;
- pr_warn("prog '%s': failed to enable perf_event FD %d: %s\n",
- prog->name, pfd, errstr(err));
- goto err_out;
+
+ if (!OPTS_GET(opts, dont_enable, false)) {
+ if (ioctl(pfd, PERF_EVENT_IOC_ENABLE, 0) < 0) {
+ err = -errno;
+ pr_warn("prog '%s': failed to enable perf_event FD %d: %s\n",
+ prog->name, pfd, errstr(err));
+ goto err_out;
+ }
}
return &link->link;
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index d1cf813a057b..455a957cb702 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -499,9 +499,11 @@ struct bpf_perf_event_opts {
__u64 bpf_cookie;
/* don't use BPF link when attach BPF program */
bool force_ioctl_attach;
+ /* don't automatically enable the event */
+ bool dont_enable;
size_t :0;
};
-#define bpf_perf_event_opts__last_field force_ioctl_attach
+#define bpf_perf_event_opts__last_field dont_enable
LIBBPF_API struct bpf_link *
bpf_program__attach_perf_event(const struct bpf_program *prog, int pfd);
--
2.50.1
