On 6/5/21 4:10 AM, Jiri Olsa wrote:
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@xxxxxxxxxx>
---
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;
[...]
@@ -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);
In kernel, looks like we support cnt = 0, here we error out.
Should we also error out in the kernel if cnt == 0?
+
+ 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);
+}
+
[...]
