On 3/8/23 13:42, Martin KaFai Lau wrote:
On 3/7/23 4:50 PM, Kui-Feng Lee wrote:
@@ -11566,22 +11591,34 @@ struct bpf_link *bpf_program__attach(const
struct bpf_program *prog)
return link;
}
+struct bpf_link_struct_ops {
+ struct bpf_link link;
+ int map_fd;
+};
+
static int bpf_link__detach_struct_ops(struct bpf_link *link)
{
+ struct bpf_link_struct_ops *st_link;
__u32 zero = 0;
- if (bpf_map_delete_elem(link->fd, &zero))
- return -errno;
+ st_link = container_of(link, struct bpf_link_struct_ops, link);
- return 0;
+ if (st_link->map_fd < 0) {
map_fd < 0 should always be true?
If the user pass a wrong link, it can fail.
I check it here explicitly even the kernel returns
an error for deleting an element of a struct_ops w/ link.
+ /* Fake bpf_link */
+ if (bpf_map_delete_elem(link->fd, &zero))
+ return -errno;
+ return 0;
+ }
+
+ /* Doesn't support detaching. */
+ return -EOPNOTSUPP;
}
struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map)
{
- struct bpf_struct_ops *st_ops;
- struct bpf_link *link;
- __u32 i, zero = 0;
- int err;
+ struct bpf_link_struct_ops *link;
+ __u32 zero = 0;
+ int err, fd;
if (!bpf_map__is_struct_ops(map) || map->fd == -1)
return libbpf_err_ptr(-EINVAL);
@@ -11590,31 +11627,34 @@ struct bpf_link
*bpf_map__attach_struct_ops(const struct bpf_map *map)
if (!link)
return libbpf_err_ptr(-EINVAL);
- st_ops = map->st_ops;
- for (i = 0; i < btf_vlen(st_ops->type); i++) {
- struct bpf_program *prog = st_ops->progs[i];
- void *kern_data;
- int prog_fd;
+ /* kern_vdata should be prepared during the loading phase. */
+ err = bpf_map_update_elem(map->fd, &zero,
map->st_ops->kern_vdata, 0);
+ if (err) {
+ err = -errno;
+ free(link);
+ return libbpf_err_ptr(err);
+ }
- if (!prog)
- continue;
- prog_fd = bpf_program__fd(prog);
- kern_data = st_ops->kern_vdata + st_ops->kern_func_off[i];
- *(unsigned long *)kern_data = prog_fd;
+ if (!(map->def.map_flags & BPF_F_LINK)) {
+ /* Fake bpf_link */
+ link->link.fd = map->fd;
+ link->map_fd = -1;
+ link->link.detach = bpf_link__detach_struct_ops;
+ return &link->link;
}
- err = bpf_map_update_elem(map->fd, &zero, st_ops->kern_vdata, 0);
- if (err) {
+ fd = bpf_link_create(map->fd, -1, BPF_STRUCT_OPS, NULL);
+ if (fd < 0) {
err = -errno;
free(link);
return libbpf_err_ptr(err);
}
- link->detach = bpf_link__detach_struct_ops;
- link->fd = map->fd;
+ link->link.fd = fd;
+ link->map_fd = map->fd;
Does it need to set link->link.detach?
Yes, I have made some changes to this part. The new code will set
link->link.detach for BPF_F_LINK as well to cleanup fd.
- return link;
+ return &link->link;
}
typedef enum bpf_perf_event_ret (*bpf_perf_event_print_t)(struct
perf_event_header *hdr,
