On 2/15/23 17:02, Martin KaFai Lau wrote:
On 2/14/23 2:17 PM, Kui-Feng Lee wrote:
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;
Similar here, does this link_update operation needs a lock?
The update function of tcp_ca checks if the name is unique with the
protection of a lock. bpf_struct_ops_map_update_elem() also check and
update state of the kvalue to prevent changing kvalue. Only one of
thread will success to register or update at any moment.
+
+ 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,
This seems a little non-intuitive to add a struct_ops specific thing to
the generic bpf_link_ops. May be avoid adding ".update_struct_ops" and
directly call the bpf_struct_ops_map_link_update() from link_update()?
It has `.update_prog` for BPF programs so `.update_struct_ops` or
`.update_map` is not that weird for me. It would be better to have a
`.update_link` to receive either a bpf_prog or bpf_map, and remove
`.update_prog`.
};
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
Why it is needed? Does it hit error without it?
It can be removed now.
+
+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;
+ }
How about BPF_F_REPLACE?
Do you mean the new_map should be labeled with BPF_F_REPLACE to replace
the old one?
+
+ 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;
This change is not obvious. Please put some comment in the commit
message about this change.
sure!
