[RFC PATCH bpf-next 2/2] libbpf: Allow setting bpf_prog priority

[Dmitrii Dolgov <9erthalion6@gmail.com>]

Introduce prio field in opts structures (bpf_tracepoint_opts,
bpf_link_create_opts, bpf_perf_event_opts) to pass a priority value for
the bpf_prog when a new bpf link is created. This value will be further
used in perf_event_set_bpf_prog to specify in which order to execute
bpf_progs attached to the same tracepoint.

Signed-off-by: Dmitrii Dolgov <9erthalion6@gmail.com>
---
 kernel/bpf/syscall.c   | 3 ++-
 tools/lib/bpf/bpf.c    | 1 +
 tools/lib/bpf/bpf.h    | 1 +
 tools/lib/bpf/libbpf.c | 4 +++-
 tools/lib/bpf/libbpf.h | 6 ++++--
 5 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 72fb3d2c30a4..629852b35b21 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3009,7 +3009,8 @@ static int bpf_perf_link_attach(const union bpf_attr *attr, struct bpf_prog *pro
 	}
 
 	event = perf_file->private_data;
-	err = perf_event_set_bpf_prog(event, prog, attr->link_create.perf_event.bpf_cookie, 0);
+	err = perf_event_set_bpf_prog(event, prog, attr->link_create.perf_event.bpf_cookie,
+								  attr->link_create.perf_event.prio);
 	if (err) {
 		bpf_link_cleanup(&link_primer);
 		goto out_put_file;
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index cf27251adb92..029c9809bf9b 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -851,6 +851,7 @@ int bpf_link_create(int prog_fd, int target_fd,
 		break;
 	case BPF_PERF_EVENT:
 		attr.link_create.perf_event.bpf_cookie = OPTS_GET(opts, perf_event.bpf_cookie, 0);
+		attr.link_create.perf_event.prio = OPTS_GET(opts, perf_event.prio, 0);
 		if (!OPTS_ZEROED(opts, perf_event))
 			return libbpf_err(-EINVAL);
 		break;
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index f4b4afb6d4ba..9a8ec9081ba7 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -412,6 +412,7 @@ struct bpf_link_create_opts {
 	union {
 		struct {
 			__u64 bpf_cookie;
+			__u32 prio;
 		} perf_event;
 		struct {
 			__u32 flags;
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 809fe209cdcc..e09c00b53772 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -9912,7 +9912,8 @@ struct bpf_link *bpf_program__attach_perf_event_opts(const struct bpf_program *p
 
 	if (kernel_supports(prog->obj, FEAT_PERF_LINK)) {
 		DECLARE_LIBBPF_OPTS(bpf_link_create_opts, link_opts,
-			.perf_event.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0));
+			.perf_event.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0),
+			.perf_event.prio = OPTS_GET(opts, prio, 0));
 
 		link_fd = bpf_link_create(prog_fd, pfd, BPF_PERF_EVENT, &link_opts);
 		if (link_fd < 0) {
@@ -10663,6 +10664,7 @@ struct bpf_link *bpf_program__attach_tracepoint_opts(const struct bpf_program *p
 		return libbpf_err_ptr(-EINVAL);
 
 	pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);
+	pe_opts.prio = OPTS_GET(opts, prio, 0);
 
 	pfd = perf_event_open_tracepoint(tp_category, tp_name);
 	if (pfd < 0) {
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 05dde85e19a6..30f1808a4b49 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -394,8 +394,9 @@ struct bpf_perf_event_opts {
 	size_t sz;
 	/* custom user-provided value fetchable through bpf_get_attach_cookie() */
 	__u64 bpf_cookie;
+	__u32 prio;
 };
-#define bpf_perf_event_opts__last_field bpf_cookie
+#define bpf_perf_event_opts__last_field prio
 
 LIBBPF_API struct bpf_link *
 bpf_program__attach_perf_event(const struct bpf_program *prog, int pfd);
@@ -508,8 +509,9 @@ struct bpf_tracepoint_opts {
 	size_t sz;
 	/* custom user-provided value fetchable through bpf_get_attach_cookie() */
 	__u64 bpf_cookie;
+	__u32 prio;
 };
-#define bpf_tracepoint_opts__last_field bpf_cookie
+#define bpf_tracepoint_opts__last_field prio
 
 LIBBPF_API struct bpf_link *
 bpf_program__attach_tracepoint(const struct bpf_program *prog,
-- 
2.32.0