By improving the BPF_LINK_UPDATE command of bpf(), it should allow you
to conveniently switch between different struct_ops on a single
bpf_link. This would enable smoother transitions from one struct_ops
to another.
The struct_ops maps passing along with BPF_LINK_UPDATE should have the
BPF_F_LINK flag.
Signed-off-by: Kui-Feng Lee <kuifeng@xxxxxxxx>
---
include/linux/bpf.h | 1 +
include/uapi/linux/bpf.h | 8 ++++--
kernel/bpf/bpf_struct_ops.c | 55 +++++++++++++++++++++++++++++++++++++
kernel/bpf/syscall.c | 31 +++++++++++++++++++++
net/ipv4/bpf_tcp_ca.c | 2 --
5 files changed, 93 insertions(+), 4 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 5fe39f56a760..03a15dc26d7a 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1408,6 +1408,7 @@ struct bpf_link_ops {
void (*show_fdinfo)(const struct bpf_link *link, struct seq_file *seq);
int (*fill_link_info)(const struct bpf_link *link,
struct bpf_link_info *info);
+ int (*update_struct_ops)(struct bpf_link *link, struct bpf_map *new_map);
};
struct bpf_tramp_link {
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 48d8b3058aa1..7c009ac859c8 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1552,8 +1552,12 @@ union bpf_attr {
struct { /* struct used by BPF_LINK_UPDATE command */
__u32 link_fd; /* link fd */
- /* new program fd to update link with */
- __u32 new_prog_fd;
+ union {
+ /* new program fd to update link with */
+ __u32 new_prog_fd;
+ /* new struct_ops map fd to update link with */
+ __u32 new_map_fd;
+ };
__u32 flags; /* extra flags */
/* expected link's program fd; is specified only if
* BPF_F_REPLACE flag is set in flags */
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index d16ca06cf09a..d329621fc721 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -752,11 +752,66 @@ static int bpf_struct_ops_map_link_fill_link_info(const struct bpf_link *link,
return 0;
}
+static int bpf_struct_ops_map_link_update(struct bpf_link *link, struct bpf_map *new_map)
+{
+ struct bpf_struct_ops_value *kvalue;
+ struct bpf_struct_ops_map *st_map, *old_st_map;
+ struct bpf_map *old_map;
+ int err;
+
+ if (new_map->map_type != BPF_MAP_TYPE_STRUCT_OPS || !(new_map->map_flags & BPF_F_LINK))
+ return -EINVAL;
+
+ old_map = link->map;
+
+ /* It does nothing if the new map is the same as the old one.
+ * A struct_ops that backs a bpf_link can not be updated or
+ * its kvalue would be updated and causes inconsistencies.
+ */
+ if (old_map == new_map)
+ return 0;
+
+ /* The new and old struct_ops must be the same type. */
+ st_map = (struct bpf_struct_ops_map *)new_map;
+ old_st_map = (struct bpf_struct_ops_map *)old_map;
+ if (st_map->st_ops != old_st_map->st_ops)
+ return -EINVAL;
+
+ /* Assure the struct_ops is updated (has value) and not
+ * backing any other link.
+ */
+ kvalue = &st_map->kvalue;
+ if (kvalue->state != BPF_STRUCT_OPS_STATE_INUSE ||
+ refcount_read(&kvalue->refcnt) != 0)
+ return -EINVAL;
+
+ bpf_map_inc(new_map);
+ refcount_set(&kvalue->refcnt, 1);
+
+ set_memory_rox((long)st_map->image, 1);
+ err = st_map->st_ops->update(kvalue->data, old_st_map->kvalue.data);
+ if (err) {
+ refcount_set(&kvalue->refcnt, 0);
+
+ set_memory_nx((long)st_map->image, 1);
+ set_memory_rw((long)st_map->image, 1);
+ bpf_map_put(new_map);
+ return err;
+ }
+
+ link->map = new_map;
+
+ bpf_struct_ops_kvalue_put(&old_st_map->kvalue);
+
+ return 0;
+}
+
static const struct bpf_link_ops bpf_struct_ops_map_lops = {
.release = bpf_struct_ops_map_link_release,
.dealloc = bpf_struct_ops_map_link_dealloc,
.show_fdinfo = bpf_struct_ops_map_link_show_fdinfo,
.fill_link_info = bpf_struct_ops_map_link_fill_link_info,
+ .update_struct_ops = bpf_struct_ops_map_link_update,
};
int link_create_struct_ops_map(union bpf_attr *attr, bpfptr_t uattr)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 54e172d8f5d1..1341634863b5 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -4650,6 +4650,32 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr)
return ret;
}
+#define BPF_LINK_UPDATE_STRUCT_OPS_LAST_FIELD link_update_struct_ops.new_map_fd
+
+static int link_update_struct_ops(struct bpf_link *link, union bpf_attr *attr)
+{
+ struct bpf_map *new_map;
+ int ret = 0;
+
+ new_map = bpf_map_get(attr->link_update.new_map_fd);
+ if (IS_ERR(new_map))
+ return -EINVAL;
+
+ if (new_map->map_type != BPF_MAP_TYPE_STRUCT_OPS) {
+ ret = -EINVAL;
+ goto out_put_map;
+ }
+
+ if (link->ops->update_struct_ops)
+ ret = link->ops->update_struct_ops(link, new_map);
+ else
+ ret = -EINVAL;
+
+out_put_map:
+ bpf_map_put(new_map);
+ return ret;
+}
+
#define BPF_LINK_UPDATE_LAST_FIELD link_update.old_prog_fd
static int link_update(union bpf_attr *attr)
@@ -4670,6 +4696,11 @@ static int link_update(union bpf_attr *attr)
if (IS_ERR(link))
return PTR_ERR(link);
+ if (link->type == BPF_LINK_TYPE_STRUCT_OPS) {
+ ret = link_update_struct_ops(link, attr);
+ goto out_put_link;
+ }
+
new_prog = bpf_prog_get(attr->link_update.new_prog_fd);
if (IS_ERR(new_prog)) {
ret = PTR_ERR(new_prog);
diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c
index 66ce5fadfe42..558b01d5250f 100644
--- a/net/ipv4/bpf_tcp_ca.c
+++ b/net/ipv4/bpf_tcp_ca.c
@@ -239,8 +239,6 @@ static int bpf_tcp_ca_init_member(const struct btf_type *t,
if (bpf_obj_name_cpy(tcp_ca->name, utcp_ca->name,
sizeof(tcp_ca->name)) <= 0)
return -EINVAL;
- if (tcp_ca_find(utcp_ca->name))
- return -EEXIST;
return 1;
}
--
2.30.2
