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Wed, 25 Feb 2026 01:27:58 -0800 (PST) From: Chengkaitao To: martin.lau@linux.dev, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, shuah@kernel.org, chengkaitao@kylinos.cn, leon.hwang@linux.dev, linux-kselftest@vger.kernel.org Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 3/6] bpf: add bpf_list_add_impl to insert node after a given list node Date: Wed, 25 Feb 2026 17:26:48 +0800 Message-ID: <20260225092651.94689-4-pilgrimtao@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260225092651.94689-1-pilgrimtao@gmail.com> References: <20260225092651.94689-1-pilgrimtao@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Kaitao Cheng Add a new kfunc bpf_list_add_impl(prev, node, meta, off) that inserts 'node' after 'prev' in the BPF linked list. Both must be in the same list; 'prev' must already be in the list. The new node must be an owning reference (e.g. from bpf_obj_new); the kfunc consumes that reference and the node becomes non-owning once inserted. Returns 0 on success, -EINVAL if prev is not in a list or node is already in a list (or duplicate insertion). On failure, the kernel drops the passed-in node. Signed-off-by: Kaitao Cheng --- kernel/bpf/helpers.c | 34 ++++++++++++++++++++++++++++++++++ kernel/bpf/verifier.c | 10 ++++++++-- 2 files changed, 42 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 577af62a9f7a..d212962d4ed6 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2495,6 +2495,39 @@ __bpf_kfunc struct bpf_list_node *bpf_list_back(struct bpf_list_head *head) return (struct bpf_list_node *)h->prev; } +static int __bpf_list_add_after(struct bpf_list_node_kern *prev, + struct bpf_list_node_kern *node, + struct btf_record *rec, u64 off) +{ + struct bpf_list_head *head; + struct list_head *n = &node->list_head, *p = &prev->list_head; + + head = READ_ONCE(prev->owner); + if (unlikely(!head)) + goto fail; + + if (cmpxchg(&node->owner, NULL, BPF_PTR_POISON)) + goto fail; + + list_add(n, p); + WRITE_ONCE(node->owner, head); + return 0; + +fail: + __bpf_obj_drop_impl((void *)n - off, rec, false); + return -EINVAL; +} + +__bpf_kfunc int bpf_list_add_impl(struct bpf_list_node *prev, + struct bpf_list_node *node, + void *meta__ign, u64 off) +{ + struct bpf_list_node_kern *n = (void *)node, *p = (void *)prev; + struct btf_struct_meta *meta = meta__ign; + + return __bpf_list_add_after(p, n, meta ? meta->record : NULL, off); +} + __bpf_kfunc struct bpf_rb_node *bpf_rbtree_remove(struct bpf_rb_root *root, struct bpf_rb_node *node) { @@ -4564,6 +4597,7 @@ 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_add_impl) 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 1e9857177a7a..923deb73683b 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -12434,6 +12434,7 @@ enum special_kfunc_type { KF_bpf_list_del, KF_bpf_list_front, KF_bpf_list_back, + KF_bpf_list_add_impl, KF_bpf_cast_to_kern_ctx, KF_bpf_rdonly_cast, KF_bpf_rcu_read_lock, @@ -12495,6 +12496,7 @@ 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_add_impl) BTF_ID(func, bpf_cast_to_kern_ctx) BTF_ID(func, bpf_rdonly_cast) BTF_ID(func, bpf_rcu_read_lock) @@ -12970,7 +12972,8 @@ 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_add_impl]; } static bool is_bpf_rbtree_api_kfunc(u32 btf_id) @@ -13092,7 +13095,8 @@ static bool check_kfunc_is_graph_node_api(struct bpf_verifier_env *env, case BPF_LIST_NODE: 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_del] || + kfunc_btf_id == special_kfunc_list[KF_bpf_list_add_impl]); break; case BPF_RB_NODE: ret = (kfunc_btf_id == special_kfunc_list[KF_bpf_rbtree_remove] || @@ -14237,6 +14241,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, if (meta.func_id == special_kfunc_list[KF_bpf_list_push_front_impl] || meta.func_id == special_kfunc_list[KF_bpf_list_push_back_impl] || + meta.func_id == special_kfunc_list[KF_bpf_list_add_impl] || meta.func_id == special_kfunc_list[KF_bpf_rbtree_add_impl]) { release_ref_obj_id = regs[BPF_REG_2].ref_obj_id; insn_aux->insert_off = regs[BPF_REG_2].off; @@ -23203,6 +23208,7 @@ static int fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, *cnt = 3; } else if (desc->func_id == special_kfunc_list[KF_bpf_list_push_back_impl] || desc->func_id == special_kfunc_list[KF_bpf_list_push_front_impl] || + desc->func_id == special_kfunc_list[KF_bpf_list_add_impl] || desc->func_id == special_kfunc_list[KF_bpf_rbtree_add_impl]) { struct btf_struct_meta *kptr_struct_meta = env->insn_aux_data[insn_idx].kptr_struct_meta; int struct_meta_reg = BPF_REG_3; -- 2.50.1 (Apple Git-155)