From: Kaitao Cheng <[email protected]> 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.
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_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 <[email protected]> --- kernel/bpf/helpers.c | 41 +++++++++++++++++++++++++++++++++++++++++ kernel/bpf/verifier.c | 15 +++++++++++++-- 2 files changed, 54 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index d212962d4ed6..ada14eca58ab 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2528,6 +2528,44 @@ __bpf_kfunc int bpf_list_add_impl(struct bpf_list_node *prev, return __bpf_list_add_after(p, n, meta ? meta->record : NULL, off); } +__bpf_kfunc bool bpf_list_is_first(struct bpf_list_head *head, struct bpf_list_node *node) +{ + struct list_head *h = (struct list_head *)head; + struct bpf_list_node_kern *n = (struct bpf_list_node_kern *)node; + + if (unlikely(!h->next) || list_empty(h)) + return false; + + if (READ_ONCE(n->owner) != head) + return false; + + return h->next == &n->list_head; +} + +__bpf_kfunc bool bpf_list_is_last(struct bpf_list_head *head, struct bpf_list_node *node) +{ + struct list_head *h = (struct list_head *)head; + struct bpf_list_node_kern *n = (struct bpf_list_node_kern *)node; + + if (unlikely(!h->next) || list_empty(h)) + return false; + + if (READ_ONCE(n->owner) != head) + return false; + + return h->prev == &n->list_head; +} + +__bpf_kfunc bool bpf_list_empty(struct bpf_list_head *head) +{ + struct list_head *h = (struct list_head *)head; + + if (unlikely(!h->next)) + return true; + + return list_empty(h); +} + __bpf_kfunc struct bpf_rb_node *bpf_rbtree_remove(struct bpf_rb_root *root, struct bpf_rb_node *node) { @@ -4598,6 +4636,9 @@ 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_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) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 923deb73683b..149eac5f70e3 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -12435,6 +12435,9 @@ enum special_kfunc_type { KF_bpf_list_front, KF_bpf_list_back, KF_bpf_list_add_impl, + 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, @@ -12497,6 +12500,9 @@ 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_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) @@ -12973,7 +12979,10 @@ 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_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) @@ -13096,7 +13105,9 @@ 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_is_first] || + kfunc_btf_id == special_kfunc_list[KF_bpf_list_is_last]); break; case BPF_RB_NODE: ret = (kfunc_btf_id == special_kfunc_list[KF_bpf_rbtree_remove] || -- 2.50.1 (Apple Git-155)
