[PATCH bpf-next v2 12/21] libbpf: Add tracing_multi link support for bpf progs

[Leon Hwang <leon.hwang@linux.dev>]

By design, a tracing_multi link does not support both kernel functions
and bpf progs at the same time.

In libbpf, the bpf_tracing_multi_opts options provides two new fields for
tracing bpf progs:

* 'fds': the fd array of the target bpf progs. One fd must be provided
         multiple times for multiple targets.
* 'funcs': the function name array of the target bpf progs.

The 'cnt' field indicates the size of both 'fds' and 'funcs' arrays.

The 'funcs' will be translated to 'ids' by 'libbpf_find_prog_btf_id()'.

At last, 'fds'+'ids' will be passed to kernel.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 tools/lib/bpf/bpf.c    |  1 +
 tools/lib/bpf/bpf.h    |  2 ++
 tools/lib/bpf/libbpf.c | 41 +++++++++++++++++++++++++++++++++++++----
 tools/lib/bpf/libbpf.h |  4 +++-
 4 files changed, 43 insertions(+), 5 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index b49822d212ae..4a78ccba9df2 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -852,6 +852,7 @@ int bpf_link_create(int prog_fd, int target_fd,
 		attr.link_create.tracing_multi.ids = ptr_to_u64(OPTS_GET(opts, tracing_multi.ids, 0));
 		attr.link_create.tracing_multi.cookies = ptr_to_u64(OPTS_GET(opts, tracing_multi.cookies, 0));
 		attr.link_create.tracing_multi.cnt = OPTS_GET(opts, tracing_multi.cnt, 0);
+		attr.link_create.tracing_multi.fds = ptr_to_u64(OPTS_GET(opts, tracing_multi.fds, 0));
 		if (!OPTS_ZEROED(opts, tracing_multi))
 			return libbpf_err(-EINVAL);
 		break;
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index 826d9cc9ab65..cc37cf622dd8 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -474,6 +474,8 @@ struct bpf_link_create_opts {
 			const __u32 *ids;
 			const __u64 *cookies;
 			__u32 cnt;
+			__u32 :32;
+			const int *fds;
 		} tracing_multi;
 	};
 	size_t :0;
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index cb09ded90773..edc5e8e813f3 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -13671,10 +13671,12 @@ bpf_program__attach_tracing_multi(const struct bpf_program *prog, const char *pa
 {
 	LIBBPF_OPTS(bpf_link_create_opts, lopts);
 	int prog_fd, link_fd, err, cnt;
+	struct bpf_link *link = NULL;
 	__u32 *free_ids = NULL;
-	struct bpf_link *link;
 	const __u64 *cookies;
+	const char **funcs;
 	const __u32 *ids;
+	const int *fds;
 
 	if (!OPTS_VALID(opts, bpf_tracing_multi_opts))
 		return libbpf_err_ptr(-EINVAL);
@@ -13689,12 +13691,22 @@ bpf_program__attach_tracing_multi(const struct bpf_program *prog, const char *pa
 	cnt = OPTS_GET(opts, cnt, 0);
 	ids = OPTS_GET(opts, ids, NULL);
 	cookies = OPTS_GET(opts, cookies, NULL);
+	fds = OPTS_GET(opts, fds, NULL);
+	funcs = OPTS_GET(opts, funcs, NULL);
 
-	if (!!ids != !!cnt)
+	if (ids && fds)
+		return libbpf_err_ptr(-EINVAL);
+	if (!!fds != !!funcs)
+		return libbpf_err_ptr(-EINVAL);
+	if (fds && !cnt)
 		return libbpf_err_ptr(-EINVAL);
-	if (pattern && (ids || cookies))
+	if (ids && !cnt)
 		return libbpf_err_ptr(-EINVAL);
-	if (!pattern && !ids)
+	if (!fds && !ids && cnt)
+		return libbpf_err_ptr(-EINVAL);
+	if (pattern && (fds || ids || cookies))
+		return libbpf_err_ptr(-EINVAL);
+	if (!pattern && !ids && !fds)
 		return libbpf_err_ptr(-EINVAL);
 
 	if (pattern) {
@@ -13704,11 +13716,32 @@ bpf_program__attach_tracing_multi(const struct bpf_program *prog, const char *pa
 		if (cnt == 0)
 			return libbpf_err_ptr(-EINVAL);
 		ids = (const __u32 *) free_ids;
+	} else if (fds) {
+		size_t cap = 0;
+		int i;
+
+		err = libbpf_ensure_mem((void **) &free_ids, &cap, sizeof(*free_ids), cnt);
+		if (err)
+			return libbpf_err_ptr(err);
+
+		for (i = 0; i < cnt; i++) {
+			if (!funcs[i]) {
+				err = -EINVAL;
+				goto error;
+			}
+			err = libbpf_find_prog_btf_id(funcs[i], fds[i], prog->obj->token_fd);
+			if (err < 0)
+				goto error;
+
+			free_ids[i] = err;
+		}
+		ids = (const __u32 *) free_ids;
 	}
 
 	lopts.tracing_multi.ids = ids;
 	lopts.tracing_multi.cookies = cookies;
 	lopts.tracing_multi.cnt = cnt;
+	lopts.tracing_multi.fds = fds;
 
 	link = calloc(1, sizeof(*link));
 	if (!link) {
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 03f794f4adb0..612f3e17ebc2 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -746,10 +746,12 @@ struct bpf_tracing_multi_opts {
 	const __u32 *ids;
 	const __u64 *cookies;
 	size_t cnt;
+	const int *fds;
+	const char **funcs;
 	size_t :0;
 };
 
-#define bpf_tracing_multi_opts__last_field cnt
+#define bpf_tracing_multi_opts__last_field funcs
 
 LIBBPF_API struct bpf_link *
 bpf_program__attach_tracing_multi(const struct bpf_program *prog, const char *pattern,
-- 
2.55.0