[PATCHv5 bpf-next 14/28] libbpf: Add bpf_program__attach_uprobe_multi function

Jiri Olsa
2023-07-30T13:44:49Z

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>
---
tools/lib/bpf/libbpf.c | 114 +++++++++++++++++++++++++++++++++++++++
tools/lib/bpf/libbpf.h | 51 ++++++++++++++++++
tools/lib/bpf/libbpf.map | 1 +
3 files changed, 166 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 445953a4d8fc..eb16d6f307e0 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -11128,6 +11128,120 @@ 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,
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 55b97b208754..2e3eb3614c40 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/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;
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 9c7538dd5835..841a2f9c6fef 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/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;
--
2.41.0