libbpf: Add bpf_program__attach_uprobe_multi function

Adding bpf_program__attach_uprobe_multi function that
allows to attach multiple uprobes with uprobe_multi link.

The user can specify uprobes with direct arguments:

  binary_path/func_pattern/pid

or with struct bpf_uprobe_multi_opts opts argument fields:

  const char **syms;
  const unsigned long *offsets;
  const unsigned long *ref_ctr_offsets;
  const __u64 *cookies;

User can specify 2 mutually exclusive set of inputs:

 1) use only path/func_pattern/pid arguments

 2) use path/pid with allowed combinations of:
    syms/offsets/ref_ctr_offsets/cookies/cnt

    - syms and offsets are mutually exclusive
    - ref_ctr_offsets and cookies are optional

Any other usage results in error.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20230809083440.3209381-15-jolsa@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>

tools/lib/bpf/libbpf.c

@@ -11146,6 +11146,120 @@ static int resolve_full_path(const char *file, char *result, size_t result_sz)
 	return -ENOENT;
 }
 
+struct bpf_link *
+bpf_program__attach_uprobe_multi(const struct bpf_program *prog,
+				 pid_t pid,
+				 const char *path,
+				 const char *func_pattern,
+				 const struct bpf_uprobe_multi_opts *opts)
+{
+	const unsigned long *ref_ctr_offsets = NULL, *offsets = NULL;
+	LIBBPF_OPTS(bpf_link_create_opts, lopts);
+	unsigned long *resolved_offsets = NULL;
+	int err = 0, link_fd, prog_fd;
+	struct bpf_link *link = NULL;
+	char errmsg[STRERR_BUFSIZE];
+	char full_path[PATH_MAX];
+	const __u64 *cookies;
+	const char **syms;
+	size_t cnt;
+
+	if (!OPTS_VALID(opts, bpf_uprobe_multi_opts))
+		return libbpf_err_ptr(-EINVAL);
+
+	syms = OPTS_GET(opts, syms, NULL);
+	offsets = OPTS_GET(opts, offsets, NULL);
+	ref_ctr_offsets = OPTS_GET(opts, ref_ctr_offsets, NULL);
+	cookies = OPTS_GET(opts, cookies, NULL);
+	cnt = OPTS_GET(opts, cnt, 0);
+
+	/*
+	 * User can specify 2 mutually exclusive set of inputs:
+	 *
+	 * 1) use only path/func_pattern/pid arguments
+	 *
+	 * 2) use path/pid with allowed combinations of:
+	 *    syms/offsets/ref_ctr_offsets/cookies/cnt
+	 *
+	 *    - syms and offsets are mutually exclusive
+	 *    - ref_ctr_offsets and cookies are optional
+	 *
+	 * Any other usage results in error.
+	 */
+
+	if (!path)
+		return libbpf_err_ptr(-EINVAL);
+	if (!func_pattern && cnt == 0)
+		return libbpf_err_ptr(-EINVAL);
+
+	if (func_pattern) {
+		if (syms || offsets || ref_ctr_offsets || cookies || cnt)
+			return libbpf_err_ptr(-EINVAL);
+	} else {
+		if (!!syms == !!offsets)
+			return libbpf_err_ptr(-EINVAL);
+	}
+
+	if (func_pattern) {
+		if (!strchr(path, '/')) {
+			err = resolve_full_path(path, full_path, sizeof(full_path));
+			if (err) {
+				pr_warn("prog '%s': failed to resolve full path for '%s': %d\n",
+					prog->name, path, err);
+				return libbpf_err_ptr(err);
+			}
+			path = full_path;
+		}
+
+		err = elf_resolve_pattern_offsets(path, func_pattern,
+						  &resolved_offsets, &cnt);
+		if (err < 0)
+			return libbpf_err_ptr(err);
+		offsets = resolved_offsets;
+	} else if (syms) {
+		err = elf_resolve_syms_offsets(path, cnt, syms, &resolved_offsets);
+		if (err < 0)
+			return libbpf_err_ptr(err);
+		offsets = resolved_offsets;
+	}
+
+	lopts.uprobe_multi.path = path;
+	lopts.uprobe_multi.offsets = offsets;
+	lopts.uprobe_multi.ref_ctr_offsets = ref_ctr_offsets;
+	lopts.uprobe_multi.cookies = cookies;
+	lopts.uprobe_multi.cnt = cnt;
+	lopts.uprobe_multi.flags = OPTS_GET(opts, retprobe, false) ? BPF_F_UPROBE_MULTI_RETURN : 0;
+
+	if (pid == 0)
+		pid = getpid();
+	if (pid > 0)
+		lopts.uprobe_multi.pid = pid;
+
+	link = calloc(1, sizeof(*link));
+	if (!link) {
+		err = -ENOMEM;
+		goto error;
+	}
+	link->detach = &bpf_link__detach_fd;
+
+	prog_fd = bpf_program__fd(prog);
+	link_fd = bpf_link_create(prog_fd, 0, BPF_TRACE_UPROBE_MULTI, &lopts);
+	if (link_fd < 0) {
+		err = -errno;
+		pr_warn("prog '%s': failed to attach multi-uprobe: %s\n",
+			prog->name, libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
+		goto error;
+	}
+	link->fd = link_fd;
+	free(resolved_offsets);
+	return link;
+
+error:
+	free(resolved_offsets);
+	free(link);
+	return libbpf_err_ptr(err);
+}
+
 LIBBPF_API struct bpf_link *
 bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
 				const char *binary_path, size_t func_offset,

tools/lib/bpf/libbpf.h

@@ -529,6 +529,57 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
 				      const char *pattern,
 				      const struct bpf_kprobe_multi_opts *opts);
 
+struct bpf_uprobe_multi_opts {
+	/* size of this struct, for forward/backward compatibility */
+	size_t sz;
+	/* array of function symbols to attach to */
+	const char **syms;
+	/* array of function addresses to attach to */
+	const unsigned long *offsets;
+	/* optional, array of associated ref counter offsets */
+	const unsigned long *ref_ctr_offsets;
+	/* optional, array of associated BPF cookies */
+	const __u64 *cookies;
+	/* number of elements in syms/addrs/cookies arrays */
+	size_t cnt;
+	/* create return uprobes */
+	bool retprobe;
+	size_t :0;
+};
+
+#define bpf_uprobe_multi_opts__last_field retprobe
+
+/**
+ * @brief **bpf_program__attach_uprobe_multi()** attaches a BPF program
+ * to multiple uprobes with uprobe_multi link.
+ *
+ * User can specify 2 mutually exclusive set of inputs:
+ *
+ *   1) use only path/func_pattern/pid arguments
+ *
+ *   2) use path/pid with allowed combinations of
+ *      syms/offsets/ref_ctr_offsets/cookies/cnt
+ *
+ *      - syms and offsets are mutually exclusive
+ *      - ref_ctr_offsets and cookies are optional
+ *
+ *
+ * @param prog BPF program to attach
+ * @param pid Process ID to attach the uprobe to, 0 for self (own process),
+ * -1 for all processes
+ * @param binary_path Path to binary
+ * @param func_pattern Regular expression to specify functions to attach
+ * BPF program to
+ * @param opts Additional options (see **struct bpf_uprobe_multi_opts**)
+ * @return 0, on success; negative error code, otherwise
+ */
+LIBBPF_API struct bpf_link *
+bpf_program__attach_uprobe_multi(const struct bpf_program *prog,
+				 pid_t pid,
+				 const char *binary_path,
+				 const char *func_pattern,
+				 const struct bpf_uprobe_multi_opts *opts);
+
 struct bpf_ksyscall_opts {
 	/* size of this struct, for forward/backward compatibility */
 	size_t sz;

tools/lib/bpf/libbpf.map

@@ -398,4 +398,5 @@ LIBBPF_1.3.0 {
 		bpf_prog_detach_opts;
 		bpf_program__attach_netfilter;
 		bpf_program__attach_tcx;
+		bpf_program__attach_uprobe_multi;
 } LIBBPF_1.2.0;