github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-07-27 17:47:41 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

bpf: add bpf_list_is_first/last/empty kfuncs

Browse Source 
Add three kfuncs for BPF linked list queries:
- bpf_list_is_first(head, node): true if node is the first in the list.
- bpf_list_is_last(head, node): true if node is the last in the list.
- bpf_list_empty(head): true if the list has no entries.

Currently, without these kfuncs, to implement the above functionality
it is necessary to first call bpf_list_pop_front/back to retrieve the
first or last node before checking whether the passed-in node was the
first or last one. After the check, the node had to be pushed back into
the list using bpf_list_push_front/back, which was very inefficient.

Now, with the bpf_list_is_first/last/empty kfuncs, we can directly
check whether a node is the first, last, or whether the list is empty,
without having to first retrieve the node.

Signed-off-by: Kaitao Cheng <chengkaitao@kylinos.cn>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Link: https://lore.kernel.org/r/20260521032306.97118-8-kaitao.cheng@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Kaitao Cheng 2026-05-21 11:23:05 +08:00 committed by Alexei Starovoitov
parent a3493ca504
commit 745515d386
2 changed files with 53 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

40
kernel/bpf/helpers.c
View File

@ -2656,6 +2656,43 @@ __bpf_kfunc struct bpf_list_node *bpf_list_back(struct bpf_list_head *head)
return (struct bpf_list_node *)h->prev;
}
__bpf_kfunc bool bpf_list_is_first(struct bpf_list_head *head,
struct bpf_list_node *node__nonown_allowed)
{
struct list_head *h = (struct list_head *)head;
struct bpf_list_node_kern *kn = (struct bpf_list_node_kern *)node__nonown_allowed;
if (READ_ONCE(kn->owner) != head)
return false;
return list_is_first(&kn->list_head, h);
}
__bpf_kfunc bool bpf_list_is_last(struct bpf_list_head *head,
struct bpf_list_node *node__nonown_allowed)
{
struct list_head *h = (struct list_head *)head;
struct bpf_list_node_kern *kn = (struct bpf_list_node_kern *)node__nonown_allowed;
if (READ_ONCE(kn->owner) != head)
return false;
return list_is_last(&kn->list_head, h);
}
__bpf_kfunc bool bpf_list_empty(struct bpf_list_head *head)
{
struct list_head *h = (struct list_head *)head;
/* If list_head was 0-initialized by map, bpf_obj_init_field wasn't
* called on its fields, so init here
*/
if (unlikely(!h->next))
INIT_LIST_HEAD(h);
return list_empty(h);
}
__bpf_kfunc struct bpf_rb_node *bpf_rbtree_remove(struct bpf_rb_root *root,
struct bpf_rb_node *node)
{
@ -4772,6 +4809,9 @@ BTF_ID_FLAGS(func, bpf_list_pop_back, KF_ACQUIRE | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_list_del, KF_ACQUIRE | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_list_front, KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_list_back, KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_list_is_first)
BTF_ID_FLAGS(func, bpf_list_is_last)
BTF_ID_FLAGS(func, bpf_list_empty)
BTF_ID_FLAGS(func, bpf_task_acquire, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_task_release, KF_RELEASE)
BTF_ID_FLAGS(func, bpf_rbtree_remove, KF_ACQUIRE | KF_RET_NULL)

15
kernel/bpf/verifier.c
View File

@ -10965,6 +10965,9 @@ enum special_kfunc_type {
KF_bpf_list_del,
KF_bpf_list_front,
KF_bpf_list_back,
KF_bpf_list_is_first,
KF_bpf_list_is_last,
KF_bpf_list_empty,
KF_bpf_cast_to_kern_ctx,
KF_bpf_rdonly_cast,
KF_bpf_rcu_read_lock,
@ -11035,6 +11038,9 @@ BTF_ID(func, bpf_list_pop_back)
BTF_ID(func, bpf_list_del)
BTF_ID(func, bpf_list_front)
BTF_ID(func, bpf_list_back)
BTF_ID(func, bpf_list_is_first)
BTF_ID(func, bpf_list_is_last)
BTF_ID(func, bpf_list_empty)
BTF_ID(func, bpf_cast_to_kern_ctx)
BTF_ID(func, bpf_rdonly_cast)
BTF_ID(func, bpf_rcu_read_lock)
@ -11556,7 +11562,10 @@ static bool is_bpf_list_api_kfunc(u32 btf_id)
btf_id == special_kfunc_list[KF_bpf_list_pop_back] ||
btf_id == special_kfunc_list[KF_bpf_list_del] ||
btf_id == special_kfunc_list[KF_bpf_list_front] ||
btf_id == special_kfunc_list[KF_bpf_list_back];
btf_id == special_kfunc_list[KF_bpf_list_back] ||
btf_id == special_kfunc_list[KF_bpf_list_is_first] ||
btf_id == special_kfunc_list[KF_bpf_list_is_last] ||
btf_id == special_kfunc_list[KF_bpf_list_empty];
}
static bool is_bpf_rbtree_api_kfunc(u32 btf_id)
@ -11678,7 +11687,9 @@ static bool check_kfunc_is_graph_node_api(struct bpf_verifier_env *env,
switch (node_field_type) {
case BPF_LIST_NODE:
ret = is_bpf_list_push_kfunc(kfunc_btf_id) ||
kfunc_btf_id == special_kfunc_list[KF_bpf_list_del];
kfunc_btf_id == special_kfunc_list[KF_bpf_list_del] ||
kfunc_btf_id == special_kfunc_list[KF_bpf_list_is_first] ||
kfunc_btf_id == special_kfunc_list[KF_bpf_list_is_last];
break;
case BPF_RB_NODE:
ret = (is_bpf_rbtree_add_kfunc(kfunc_btf_id) ||