[PATCH 15/19] libbpf: Add support to link multi func tracing program

[Jiri Olsa <jolsa@kernel.org>]

Adding support to link multi func tracing program
through link_create interface.

Adding special types for multi func programs:

  fentry.multi
  fexit.multi

so you can define multi func programs like:

  SEC("fentry.multi/bpf_fentry_test*")
  int BPF_PROG(test1, unsigned long ip, __u64 a, __u64 b, __u64 c, __u64 d, __u64 e, __u64 f)

that defines test1 to be attached to bpf_fentry_test* functions,
and able to attach ip and 6 arguments.

If functions are not specified the program needs to be attached
manually.

Adding new btf id related fields to bpf_link_create_opts and
bpf_link_create to use them.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 tools/lib/bpf/bpf.c    | 11 ++++++-
 tools/lib/bpf/bpf.h    |  4 ++-
 tools/lib/bpf/libbpf.c | 72 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 85 insertions(+), 2 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 86dcac44f32f..da892737b522 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -674,7 +674,8 @@ int bpf_link_create(int prog_fd, int target_fd,
 		    enum bpf_attach_type attach_type,
 		    const struct bpf_link_create_opts *opts)
 {
-	__u32 target_btf_id, iter_info_len;
+	__u32 target_btf_id, iter_info_len, multi_btf_ids_cnt;
+	__s32 *multi_btf_ids;
 	union bpf_attr attr;
 	int fd;
 
@@ -687,6 +688,9 @@ int bpf_link_create(int prog_fd, int target_fd,
 	if (iter_info_len && target_btf_id)
 		return libbpf_err(-EINVAL);
 
+	multi_btf_ids = OPTS_GET(opts, multi_btf_ids, 0);
+	multi_btf_ids_cnt = OPTS_GET(opts, multi_btf_ids_cnt, 0);
+
 	memset(&attr, 0, sizeof(attr));
 	attr.link_create.prog_fd = prog_fd;
 	attr.link_create.target_fd = target_fd;
@@ -701,6 +705,11 @@ int bpf_link_create(int prog_fd, int target_fd,
 		attr.link_create.target_btf_id = target_btf_id;
 	}
 
+	if (multi_btf_ids && multi_btf_ids_cnt) {
+		attr.link_create.multi_btf_ids = (__u64) multi_btf_ids;
+		attr.link_create.multi_btf_ids_cnt = multi_btf_ids_cnt;
+	}
+
 	fd = sys_bpf(BPF_LINK_CREATE, &attr, sizeof(attr));
 	return libbpf_err_errno(fd);
 }
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index 4f758f8f50cd..2f78b6c34765 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -177,8 +177,10 @@ struct bpf_link_create_opts {
 	union bpf_iter_link_info *iter_info;
 	__u32 iter_info_len;
 	__u32 target_btf_id;
+	__s32 *multi_btf_ids;
+	__u32 multi_btf_ids_cnt;
 };
-#define bpf_link_create_opts__last_field target_btf_id
+#define bpf_link_create_opts__last_field multi_btf_ids_cnt
 
 LIBBPF_API int bpf_link_create(int prog_fd, int target_fd,
 			       enum bpf_attach_type attach_type,
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 65f87cc1220c..bd31de3b6a85 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -228,6 +228,7 @@ struct bpf_sec_def {
 	bool is_attachable;
 	bool is_attach_btf;
 	bool is_sleepable;
+	bool is_multi_func;
 	attach_fn_t attach_fn;
 };
 
@@ -7609,6 +7610,8 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
 
 		if (prog->sec_def->is_sleepable)
 			prog->prog_flags |= BPF_F_SLEEPABLE;
+		if (prog->sec_def->is_multi_func)
+			prog->prog_flags |= BPF_F_MULTI_FUNC;
 		bpf_program__set_type(prog, prog->sec_def->prog_type);
 		bpf_program__set_expected_attach_type(prog,
 				prog->sec_def->expected_attach_type);
@@ -9070,6 +9073,8 @@ static struct bpf_link *attach_raw_tp(const struct bpf_sec_def *sec,
 				      struct bpf_program *prog);
 static struct bpf_link *attach_trace(const struct bpf_sec_def *sec,
 				     struct bpf_program *prog);
+static struct bpf_link *attach_trace_multi(const struct bpf_sec_def *sec,
+					   struct bpf_program *prog);
 static struct bpf_link *attach_lsm(const struct bpf_sec_def *sec,
 				   struct bpf_program *prog);
 static struct bpf_link *attach_iter(const struct bpf_sec_def *sec,
@@ -9143,6 +9148,14 @@ static const struct bpf_sec_def section_defs[] = {
 		.attach_fn = attach_iter),
 	SEC_DEF("syscall", SYSCALL,
 		.is_sleepable = true),
+	SEC_DEF("fentry.multi/", TRACING,
+		.expected_attach_type = BPF_TRACE_FENTRY,
+		.is_multi_func = true,
+		.attach_fn = attach_trace_multi),
+	SEC_DEF("fexit.multi/", TRACING,
+		.expected_attach_type = BPF_TRACE_FEXIT,
+		.is_multi_func = true,
+		.attach_fn = attach_trace_multi),
 	BPF_EAPROG_SEC("xdp_devmap/",		BPF_PROG_TYPE_XDP,
 						BPF_XDP_DEVMAP),
 	BPF_EAPROG_SEC("xdp_cpumap/",		BPF_PROG_TYPE_XDP,
@@ -9584,6 +9597,9 @@ static int libbpf_find_attach_btf_id(struct bpf_program *prog, int *btf_obj_fd,
 	if (!name)
 		return -EINVAL;
 
+	if (prog->prog_flags & BPF_F_MULTI_FUNC)
+		return 0;
+
 	for (i = 0; i < ARRAY_SIZE(section_defs); i++) {
 		if (!section_defs[i].is_attach_btf)
 			continue;
@@ -10537,6 +10553,62 @@ static struct bpf_link *bpf_program__attach_btf_id(struct bpf_program *prog)
 	return (struct bpf_link *)link;
 }
 
+static struct bpf_link *bpf_program__attach_multi(struct bpf_program *prog)
+{
+	char *pattern = prog->sec_name + prog->sec_def->len;
+	DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts);
+	enum bpf_attach_type attach_type;
+	int prog_fd, link_fd, cnt, err;
+	struct bpf_link *link = NULL;
+	__s32 *ids = NULL;
+
+	prog_fd = bpf_program__fd(prog);
+	if (prog_fd < 0) {
+		pr_warn("prog '%s': can't attach before loaded\n", prog->name);
+		return ERR_PTR(-EINVAL);
+	}
+
+	err = bpf_object__load_vmlinux_btf(prog->obj, true);
+	if (err)
+		return ERR_PTR(err);
+
+	cnt = btf__find_by_pattern_kind(prog->obj->btf_vmlinux, pattern,
+					BTF_KIND_FUNC, &ids);
+	if (cnt <= 0)
+		return ERR_PTR(-EINVAL);
+
+	link = calloc(1, sizeof(*link));
+	if (!link) {
+		err = -ENOMEM;
+		goto out_err;
+	}
+	link->detach = &bpf_link__detach_fd;
+
+	opts.multi_btf_ids = ids;
+	opts.multi_btf_ids_cnt = cnt;
+
+	attach_type = bpf_program__get_expected_attach_type(prog);
+	link_fd = bpf_link_create(prog_fd, 0, attach_type, &opts);
+	if (link_fd < 0) {
+		err = -errno;
+		goto out_err;
+	}
+	link->fd = link_fd;
+	free(ids);
+	return link;
+
+out_err:
+	free(link);
+	free(ids);
+	return ERR_PTR(err);
+}
+
+static struct bpf_link *attach_trace_multi(const struct bpf_sec_def *sec,
+					   struct bpf_program *prog)
+{
+	return bpf_program__attach_multi(prog);
+}
+
 struct bpf_link *bpf_program__attach_trace(struct bpf_program *prog)
 {
 	return bpf_program__attach_btf_id(prog);
-- 
2.31.1