On 2/14/23 18:58, Stanislav Fomichev wrote:
On 02/14, Kui-Feng Lee wrote:
bpf_map__attach_struct_ops() was creating a dummy bpf_link as a
placeholder, but now it is constructing an authentic one by calling
bpf_link_create() if the map has the BPF_F_LINK flag.
You can flag a struct_ops map with BPF_F_LINK by calling
bpf_map__set_map_flags().
Signed-off-by: Kui-Feng Lee <kuifeng@xxxxxxxx>
---
tools/lib/bpf/libbpf.c | 73 +++++++++++++++++++++++++++++++++---------
1 file changed, 58 insertions(+), 15 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 75ed95b7e455..1eff6a03ddd9 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -11430,29 +11430,41 @@ struct bpf_link *bpf_program__attach(const
struct bpf_program *prog)
return link;
}
+struct bpf_link_struct_ops_map {
+ struct bpf_link link;
+ int map_fd;
+};
Ah, ok, now you're adding bpf_link_struct_ops_map. I guess I'm now
confused why you haven't done it in the first patch :-/
Just won't to mix the libbpf part and kernel part in one patch.
And what are these fake bpf_links? Can you share more about it means?
For the next version, I will detail it in the commit log. In a nutshell,
before this point, there was no bpf_link for struct_ops. Libbpf
attempted to create an equivalent interface to other BPF programs by
providing a simulated bpf_link instead of a true one from the kernel;
that fake bpf_link stores FDs associated with struct_ops maps rather
than real bpf_links.
+
static int bpf_link__detach_struct_ops(struct bpf_link *link)
{
+ struct bpf_link_struct_ops_map *st_link;
__u32 zero = 0;
- if (bpf_map_delete_elem(link->fd, &zero))
+ st_link = container_of(link, struct bpf_link_struct_ops_map, link);
+
+ if (st_link->map_fd < 0) {
+ /* Fake bpf_link */
+ if (bpf_map_delete_elem(link->fd, &zero))
+ return -errno;
+ return 0;
+ }
+
+ if (bpf_map_delete_elem(st_link->map_fd, &zero))
+ return -errno;
+
+ if (close(link->fd))
return -errno;
return 0;
}
-struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map)
+/*
+ * Update the map with the prepared vdata.
+ */
+static int bpf_map__update_vdata(const struct bpf_map *map)
{
struct bpf_struct_ops *st_ops;
- struct bpf_link *link;
__u32 i, zero = 0;
- int err;
-
- if (!bpf_map__is_struct_ops(map) || map->fd == -1)
- return libbpf_err_ptr(-EINVAL);
-
- link = calloc(1, sizeof(*link));
- if (!link)
- return libbpf_err_ptr(-EINVAL);
st_ops = map->st_ops;
for (i = 0; i < btf_vlen(st_ops->type); i++) {
@@ -11468,17 +11480,48 @@ struct bpf_link
*bpf_map__attach_struct_ops(const struct bpf_map *map)
*(unsigned long *)kern_data = prog_fd;
}
- err = bpf_map_update_elem(map->fd, &zero, st_ops->kern_vdata, 0);
+ return bpf_map_update_elem(map->fd, &zero, st_ops->kern_vdata, 0);
+}
+
+struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map)
+{
+ struct bpf_link_struct_ops_map *link;
+ int err, fd;
+
+ if (!bpf_map__is_struct_ops(map) || map->fd == -1)
+ return libbpf_err_ptr(-EINVAL);
+
+ link = calloc(1, sizeof(*link));
+ if (!link)
+ return libbpf_err_ptr(-EINVAL);
+
+ err = bpf_map__update_vdata(map);
if (err) {
err = -errno;
free(link);
return libbpf_err_ptr(err);
}
- link->detach = bpf_link__detach_struct_ops;
- link->fd = map->fd;
+ link->link.detach = bpf_link__detach_struct_ops;
- return link;
+ if (!(map->def.map_flags & BPF_F_LINK)) {
+ /* Fake bpf_link */
+ link->link.fd = map->fd;
+ link->map_fd = -1;
+ return &link->link;
+ }
+
+ fd = bpf_link_create(map->fd, -1, BPF_STRUCT_OPS_MAP, NULL);
+ if (fd < 0) {
+ err = -errno;
+ free(link);
+ return libbpf_err_ptr(err);
+ }
+
+ link->link.fd = fd;
+ link->map_fd = map->fd;
+
+ return &link->link;
}
typedef enum bpf_perf_event_ret (*bpf_perf_event_print_t)(struct
perf_event_header *hdr,
--
2.30.2
