From: Kaitao Cheng <[email protected]> Add three kfuncs for BPF linked list queries: - bpf_list_node_is_edge(head, node, is_first): true if node is the first (when is_first is true) or the last (when is_first is false) in the list. - bpf_list_empty(head): true if the list has no entries.
In previous versions, to implement the above functionality, it was 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_edge/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 <[email protected]> --- kernel/bpf/helpers.c | 37 +++++++++++++++++++++++++++++++++++++ kernel/bpf/verifier.c | 11 +++++++++-- 2 files changed, 46 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 740b53024283..3d22b6080185 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2538,6 +2538,41 @@ __bpf_kfunc int bpf_list_add_impl(struct bpf_list_head *head, return -EINVAL; } +__bpf_kfunc bool bpf_list_node_is_edge(struct bpf_list_head *head, + struct bpf_list_node *node, bool is_first) +{ + struct list_head *h = (struct list_head *)head, *edge; + struct bpf_list_node_kern *n = (struct bpf_list_node_kern *)node; + + /* 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); + + if (list_empty(h)) + return false; + + if (READ_ONCE(n->owner) != head) + return false; + + edge = is_first ? h->next : h->prev; + return edge == &n->list_head; +} + +__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) { @@ -4608,6 +4643,8 @@ 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_add_impl) +BTF_ID_FLAGS(func, bpf_list_node_is_edge) +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) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index e458cf3b1dd1..d133d18aa0cc 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -12465,6 +12465,8 @@ enum special_kfunc_type { KF_bpf_list_front, KF_bpf_list_back, KF_bpf_list_add_impl, + KF_bpf_list_node_is_edge, + KF_bpf_list_empty, KF_bpf_cast_to_kern_ctx, KF_bpf_rdonly_cast, KF_bpf_rcu_read_lock, @@ -12527,6 +12529,8 @@ BTF_ID(func, bpf_list_del) BTF_ID(func, bpf_list_front) BTF_ID(func, bpf_list_back) BTF_ID(func, bpf_list_add_impl) +BTF_ID(func, bpf_list_node_is_edge) +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) @@ -13003,7 +13007,9 @@ static bool is_bpf_list_api_kfunc(u32 btf_id) 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_add_impl]; + btf_id == special_kfunc_list[KF_bpf_list_add_impl] || + btf_id == special_kfunc_list[KF_bpf_list_node_is_edge] || + btf_id == special_kfunc_list[KF_bpf_list_empty]; } static bool is_bpf_rbtree_api_kfunc(u32 btf_id) @@ -13126,7 +13132,8 @@ static bool check_kfunc_is_graph_node_api(struct bpf_verifier_env *env, ret = (kfunc_btf_id == special_kfunc_list[KF_bpf_list_push_front_impl] || kfunc_btf_id == special_kfunc_list[KF_bpf_list_push_back_impl] || kfunc_btf_id == special_kfunc_list[KF_bpf_list_del] || - kfunc_btf_id == special_kfunc_list[KF_bpf_list_add_impl]); + kfunc_btf_id == special_kfunc_list[KF_bpf_list_add_impl] || + kfunc_btf_id == special_kfunc_list[KF_bpf_list_node_is_edge]); break; case BPF_RB_NODE: ret = (kfunc_btf_id == special_kfunc_list[KF_bpf_rbtree_remove] || -- 2.50.1 (Apple Git-155)
