[RFC PATCH bpf-next 13/17] libbpf: Add support to create tracing multi link

Jiri Olsa
2022-08-08T14:09:01Z

Adding new interface tion to attach programs with
tracing multi link:

bpf_program__attach_tracing_multi(const struct bpf_program *prog,
const char *pattern,
const struct bpf_tracing_multi_opts *opts);

The program is attach to functions specified by patter
or by btf IDs specified in bpf_tracing_multi_opts object.

Adding support for new sections to attach programs
with above functions:

fentry.multi/pattern
fexit.multi/pattern

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
tools/lib/bpf/bpf.c | 7 ++++
tools/lib/bpf/bpf.h | 4 ++
tools/lib/bpf/libbpf.c | 89 ++++++++++++++++++++++++++++++++++++++++
tools/lib/bpf/libbpf.h | 14 +++++++
tools/lib/bpf/libbpf.map | 1 +
5 files changed, 115 insertions(+)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index efcc06dafbd9..06e6666ee90e 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -713,6 +713,13 @@ int bpf_link_create(int prog_fd, int target_fd,
if (!OPTS_ZEROED(opts, kprobe_multi))
return libbpf_err(-EINVAL);
break;
+ case BPF_TRACE_FENTRY_MULTI:
+ case BPF_TRACE_FEXIT_MULTI:
+ attr.link_create.tracing_multi.btf_ids = (__u64) OPTS_GET(opts, tracing_multi.btf_ids, 0);
+ attr.link_create.tracing_multi.btf_ids_cnt = OPTS_GET(opts, tracing_multi.btf_ids_cnt, 0);
+ if (!OPTS_ZEROED(opts, tracing_multi))
+ return libbpf_err(-EINVAL);
+ break;
case BPF_TRACE_FENTRY:
case BPF_TRACE_FEXIT:
case BPF_MODIFY_RETURN:
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index 9c50beabdd14..71676228f032 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -321,6 +321,10 @@ struct bpf_link_create_opts {
struct {
__u64 cookie;
} tracing;
+ struct {
+ __u32 *btf_ids;
+ __u32 btf_ids_cnt;
+ } tracing_multi;
};
size_t :0;
};
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 0952eac92eab..209a42bed165 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -116,6 +116,8 @@ static const char * const attach_type_name[] = {
[BPF_SK_REUSEPORT_SELECT_OR_MIGRATE] = "sk_reuseport_select_or_migrate",
[BPF_PERF_EVENT] = "perf_event",
[BPF_TRACE_KPROBE_MULTI] = "trace_kprobe_multi",
+ [BPF_TRACE_FENTRY_MULTI] = "trace_fentry_multi",
+ [BPF_TRACE_FEXIT_MULTI] = "trace_fexit_multi",
};

static const char * const link_type_name[] = {
@@ -129,6 +131,7 @@ static const char * const link_type_name[] = {
[BPF_LINK_TYPE_PERF_EVENT] = "perf_event",
[BPF_LINK_TYPE_KPROBE_MULTI] = "kprobe_multi",
[BPF_LINK_TYPE_STRUCT_OPS] = "struct_ops",
+ [BPF_LINK_TYPE_TRACING_MULTI] = "tracing_multi",
};

static const char * const map_type_name[] = {
@@ -8445,6 +8448,7 @@ static int attach_trace(const struct bpf_program *prog, long cookie, struct bpf_
static int attach_kprobe_multi(const struct bpf_program *prog, long cookie, struct bpf_link **link);
static int attach_lsm(const struct bpf_program *prog, long cookie, struct bpf_link **link);
static int attach_iter(const struct bpf_program *prog, long cookie, struct bpf_link **link);
+static int attach_tracing_multi(const struct bpf_program *prog, long cookie, struct bpf_link **link);

static const struct bpf_sec_def section_defs[] = {
SEC_DEF("socket", SOCKET_FILTER, 0, SEC_NONE),
@@ -8477,6 +8481,8 @@ static const struct bpf_sec_def section_defs[] = {
SEC_DEF("fentry.s+", TRACING, BPF_TRACE_FENTRY, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),
SEC_DEF("fmod_ret.s+", TRACING, BPF_MODIFY_RETURN, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),
SEC_DEF("fexit.s+", TRACING, BPF_TRACE_FEXIT, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),
+ SEC_DEF("fentry.multi/", TRACING, BPF_TRACE_FENTRY_MULTI, 0, attach_tracing_multi),
+ SEC_DEF("fexit.multi/", TRACING, BPF_TRACE_FEXIT_MULTI, 0, attach_tracing_multi),
SEC_DEF("freplace+", EXT, 0, SEC_ATTACH_BTF, attach_trace),
SEC_DEF("lsm+", LSM, BPF_LSM_MAC, SEC_ATTACH_BTF, attach_lsm),
SEC_DEF("lsm.s+", LSM, BPF_LSM_MAC, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_lsm),
@@ -10374,6 +10380,89 @@ static int attach_kprobe_multi(const struct bpf_program *prog, long cookie, stru
return libbpf_get_error(*link);
}

+struct bpf_link *
+bpf_program__attach_tracing_multi(const struct bpf_program *prog, const char *pattern,
+ const struct bpf_tracing_multi_opts *opts)
+{
+ LIBBPF_OPTS(bpf_link_create_opts, lopts);
+ __u32 *btf_ids, cnt, *free_ids = NULL;
+ char errmsg[STRERR_BUFSIZE];
+ int prog_fd, link_fd, err;
+ struct bpf_link *link;
+
+ btf_ids = OPTS_GET(opts, btf_ids, false);
+ cnt = OPTS_GET(opts, cnt, false);
+
+ if (!pattern && !btf_ids && !cnt)
+ return libbpf_err_ptr(-EINVAL);
+ if (pattern && (btf_ids || cnt))
+ return libbpf_err_ptr(-EINVAL);
+
+ if (pattern) {
+ err = bpf_object__load_vmlinux_btf(prog->obj, true);
+ if (err)
+ return libbpf_err_ptr(err);
+
+ cnt = btf__find_by_glob_kind(prog->obj->btf_vmlinux, BTF_KIND_FUNC,
+ pattern, NULL, &btf_ids);
+ if (cnt <= 0)
+ return libbpf_err_ptr(-EINVAL);
+ free_ids = btf_ids;
+ }
+
+ lopts.tracing_multi.btf_ids = btf_ids;
+ lopts.tracing_multi.btf_ids_cnt = cnt;
+
+ link = calloc(1, sizeof(*link));
+ if (!link)
+ return libbpf_err_ptr(-ENOMEM);
+ link->detach = &bpf_link__detach_fd;
+
+ prog_fd = bpf_program__fd(prog);
+ link_fd = bpf_link_create(prog_fd, 0, prog->expected_attach_type, &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(free_ids);
+ return link;
+error:
+ free(link);
+ free(free_ids);
+ return libbpf_err_ptr(err);
+}
+
+static int attach_tracing_multi(const struct bpf_program *prog, long cookie, struct bpf_link **link)
+{
+ const char *spec;
+ char *pattern;
+ bool is_fexit;
+ int n;
+
+ /* no auto-attach for SEC("fentry.multi") and SEC("fexit.multi") */
+ if (strcmp(prog->sec_name, "fentry.multi") == 0 ||
+ strcmp(prog->sec_name, "fexit.multi") == 0)
+ return 0;
+
+ is_fexit = str_has_pfx(prog->sec_name, "fexit.multi/");
+ if (is_fexit)
+ spec = prog->sec_name + sizeof("fexit.multi/") - 1;
+ else
+ spec = prog->sec_name + sizeof("fentry.multi/") - 1;
+
+ n = sscanf(spec, "%m[a-zA-Z0-9_.*?]", &pattern);
+ if (n < 1) {
+ pr_warn("tracing multi pattern is invalid: %s\n", pattern);
+ return -EINVAL;
+ }
+
+ *link = bpf_program__attach_tracing_multi(prog, pattern, NULL);
+ return libbpf_get_error(*link);
+}
+
static void gen_uprobe_legacy_event_name(char *buf, size_t buf_sz,
const char *binary_path, uint64_t offset)
{
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 61493c4cddac..07992d8ee06c 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -503,6 +503,20 @@ bpf_program__attach_ksyscall(const struct bpf_program *prog,
const char *syscall_name,
const struct bpf_ksyscall_opts *opts);

+struct bpf_tracing_multi_opts {
+ /* size of this struct, for forward/backward compatibility */
+ size_t sz;
+ __u32 *btf_ids;
+ size_t cnt;
+ size_t :0;
+};
+
+#define bpf_kprobe_multi_opts__last_field retprobe
+
+LIBBPF_API struct bpf_link *
+bpf_program__attach_tracing_multi(const struct bpf_program *prog, const char *pattern,
+ const struct bpf_tracing_multi_opts *opts);
+
struct bpf_uprobe_opts {
/* size of this struct, for forward/backward compatiblity */
size_t sz;
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 119e6e1ea7f1..2168516a75a5 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -358,6 +358,7 @@ LIBBPF_1.0.0 {
bpf_obj_get_opts;
bpf_prog_query_opts;
bpf_program__attach_ksyscall;
+ bpf_program__attach_tracing_multi;
btf__add_enum64;
btf__add_enum64_value;
libbpf_bpf_attach_type_str;
--
2.37.1