[PATCHv2 bpf-next 11/24] libbpf: Add bpf_program__attach_uprobe_multi_opts function

Jiri Olsa
2023-06-20T08:37:42Z

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

The user can specify uprobes with direct arguments:

binary_path/func_pattern

or with struct bpf_uprobe_multi_opts opts argument fields:

const char *path;
const char **syms;
const unsigned long *offsets;
const unsigned long *ref_ctr_offsets;

User can specify 3 mutually exclusive set of incputs:

1) use only binary_path/func_pattern aruments

2) use only opts argument with allowed combinations of:
path/offsets/ref_ctr_offsets/cookies/cnt

3) use binary_path with allowed combinations of:
syms/offsets/ref_ctr_offsets/cookies/cnt

Any other usage results in error.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
tools/lib/bpf/libbpf.c | 131 +++++++++++++++++++++++++++++++++++++++
tools/lib/bpf/libbpf.h | 31 +++++++++
tools/lib/bpf/libbpf.map | 1 +
3 files changed, 163 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 3e5c88caf5d5..d972cea4c658 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -11402,6 +11402,137 @@ static int resolve_full_path(const char *file, char *result, size_t result_sz)
return -ENOENT;
}

+struct bpf_link *
+bpf_program__attach_uprobe_multi_opts(const struct bpf_program *prog,
+ pid_t pid,
+ const char *binary_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;
+ const char **resolved_symbols = NULL;
+ int err = 0, link_fd, prog_fd;
+ struct bpf_link *link = NULL;
+ char errmsg[STRERR_BUFSIZE];
+ const char *path, **syms;
+ char full_path[PATH_MAX];
+ const __u64 *cookies;
+ bool has_pattern;
+ bool retprobe;
+ size_t cnt;
+
+ if (!OPTS_VALID(opts, bpf_uprobe_multi_opts))
+ return libbpf_err_ptr(-EINVAL);
+
+ path = OPTS_GET(opts, path, NULL);
+ 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 3 mutually exclusive set of incputs:
+ *
+ * 1) use only binary_path/func_pattern aruments
+ *
+ * 2) use only opts argument with allowed combinations of:
+ * path/offsets/ref_ctr_offsets/cookies/cnt
+ *
+ * 3) use binary_path with allowed combinations of:
+ * syms/offsets/ref_ctr_offsets/cookies/cnt
+ *
+ * Any other usage results in error.
+ */
+
+ if (!binary_path && !func_pattern && !cnt)
+ return libbpf_err_ptr(-EINVAL);
+ if (func_pattern && !binary_path)
+ return libbpf_err_ptr(-EINVAL);
+
+ has_pattern = binary_path && func_pattern;
+
+ if (has_pattern) {
+ if (path || syms || offsets || ref_ctr_offsets || cookies || cnt)
+ return libbpf_err_ptr(-EINVAL);
+ } else {
+ if (!cnt)
+ return libbpf_err_ptr(-EINVAL);
+ if (!!path == !!binary_path)
+ return libbpf_err_ptr(-EINVAL);
+ if (!!syms == !!offsets)
+ return libbpf_err_ptr(-EINVAL);
+ if (path && syms)
+ return libbpf_err_ptr(-EINVAL);
+ }
+
+ if (has_pattern) {
+ if (!strchr(binary_path, '/')) {
+ err = resolve_full_path(binary_path, full_path, sizeof(full_path));
+ if (err) {
+ pr_warn("prog '%s': failed to resolve full path for '%s': %d\n",
+ prog->name, binary_path, err);
+ return libbpf_err_ptr(err);
+ }
+ binary_path = full_path;
+ }
+
+ err = elf_find_pattern_func_offset(binary_path, func_pattern,
+ &resolved_symbols, &resolved_offsets,
+ &cnt);
+ if (err < 0)
+ return libbpf_err_ptr(err);
+ offsets = resolved_offsets;
+ } else if (syms) {
+ err = elf_find_multi_func_offset(binary_path, cnt, syms, &resolved_offsets);
+ if (err < 0)
+ return libbpf_err_ptr(err);
+ offsets = resolved_offsets;
+ }
+
+ retprobe = OPTS_GET(opts, retprobe, false);
+
+ lopts.uprobe_multi.path = path ?: binary_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 = retprobe ? 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: %s\n",
+ prog->name, libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
+ goto error;
+ }
+ link->fd = link_fd;
+ free(resolved_offsets);
+ free(resolved_symbols);
+ return link;
+
+error:
+ free(resolved_offsets);
+ free(resolved_symbols);
+ 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 754da73c643b..b6ff7d69a1d7 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -529,6 +529,37 @@ 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;
+ /* path to attach */
+ const char *path;
+ /* array of function symbols to attach */
+ const char **syms;
+ /* array of function addresses to attach */
+ const unsigned long *offsets;
+ /* array of refctr offsets to attach */
+ const unsigned long *ref_ctr_offsets;
+ /* array of user-provided values fetchable through bpf_get_attach_cookie */
+ const __u64 *cookies;
+ /* number of elements in syms/addrs/cookies arrays */
+ size_t cnt;
+ /* create return uprobes */
+ bool retprobe;
+ /* pid filter */
+ int pid;
+ size_t :0;
+};
+
+#define bpf_uprobe_multi_opts__last_field pid
+
+LIBBPF_API struct bpf_link *
+bpf_program__attach_uprobe_multi_opts(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 7521a2fb7626..81558ef1bc38 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -390,6 +390,7 @@ LIBBPF_1.2.0 {
bpf_link_get_info_by_fd;
bpf_map_get_info_by_fd;
bpf_prog_get_info_by_fd;
+ bpf_program__attach_uprobe_multi_opts;
} LIBBPF_1.1.0;

LIBBPF_1.3.0 {
--
2.41.0