From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-180.mta1.migadu.com (out-180.mta1.migadu.com [95.215.58.180]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7515135C192 for ; Mon, 9 Mar 2026 06:34:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.180 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773038077; cv=none; b=Pf9m2/AwYEy5l9ZN8KzuRS9MJc9Im7cOqJIbpqtpBCQ3zqc/fC41XzCKe+HiUoIktXZeVmgkjdk8cTxxOmTU3ZHhRdJJoQoTIzaGEmo4DmhmtMxhY7vHuMi3mtiJ67IzVacOdFmA/IRIq366Ik++M/HsGxQI3GD4nSkeJtui1RQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773038077; c=relaxed/simple; bh=YlrpL0fO/7GISjyAsbJjQDNQafXT5EqPTrdkxOERr9M=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=PKJjVSrwh1pRCakx3AK6qwoVq7aX3KuG5YtAXmYsK3VtNmMJHlVxx5NQno/uvlwJZ2evGrp5QNkUZBQdQhMYHATz6ZT2US+Bir1EL4zjTEjJX4IYfY7/SNgyNY42nSCnZy6kde17lxjtyB1m+4D+RqigFrqStlt5sFFLy6CFlFM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=WFbq8ghD; arc=none smtp.client-ip=95.215.58.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="WFbq8ghD" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1773038063; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=AVYuGex5GhS6X5XqyVI/Awi8X36At9y4ChFrGeytdUI=; b=WFbq8ghDai/FKnMOgiE4mNeQ1A4hL1olHksQnJz3xuEve9xiggtFi9p+l9EhmpVKBolGd4 YAEXvXmS/OkMBcoUMsHp2H/ReZb3UqqZgHWOCWBYFHsGR/gd238M/Ll4f5ojO0Y8xU/raq 5e+QrUz1LR8AgVqc6fJnACDBCLgQtM0= Date: Mon, 9 Mar 2026 14:34:11 +0800 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH bpf-next v7 2/5] bpf: Add bpf_list_add_impl to insert node after a given list node Content-Language: en-US To: Chengkaitao , 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, linux-kselftest@vger.kernel.org Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260308134614.29711-1-pilgrimtao@gmail.com> <20260308134614.29711-3-pilgrimtao@gmail.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Leon Hwang In-Reply-To: <20260308134614.29711-3-pilgrimtao@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 8/3/26 21:46, Chengkaitao wrote: > From: Kaitao Cheng > > Add a new kfunc bpf_list_add_impl(head, new, prev, meta, off) that > inserts 'new' 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. > > We have added an additional parameter bpf_list_head *head to > bpf_list_add_impl, as the verifier requires the head parameter to > check whether the lock is being held. > > Returns 0 on success, -EINVAL if 'prev' is not in a list or 'new' > 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 | 56 ++++++++++++++++++++++++++++++------------- > kernel/bpf/verifier.c | 13 ++++++++-- > 2 files changed, 50 insertions(+), 19 deletions(-) > > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c > index 01b74c4ac00d..407520fde668 100644 > --- a/kernel/bpf/helpers.c > +++ b/kernel/bpf/helpers.c > @@ -2379,11 +2379,12 @@ __bpf_kfunc void *bpf_refcount_acquire_impl(void *p__refcounted_kptr, void *meta > return (void *)p__refcounted_kptr; > } > > -static int __bpf_list_add(struct bpf_list_node_kern *node, > - struct bpf_list_head *head, > - bool tail, struct btf_record *rec, u64 off) > +static int __bpf_list_add(struct bpf_list_head *head, > + struct bpf_list_node_kern *new, > + struct list_head *prev, > + struct btf_record *rec, u64 off) > { > - struct list_head *n = &node->list_head, *h = (void *)head; > + struct list_head *n = &new->list_head, *h = (void *)head; > > /* If list_head was 0-initialized by map, bpf_obj_init_field wasn't > * called on its fields, so init here > @@ -2391,39 +2392,59 @@ static int __bpf_list_add(struct bpf_list_node_kern *node, > if (unlikely(!h->next)) > INIT_LIST_HEAD(h); > > - /* node->owner != NULL implies !list_empty(n), no need to separately > + /* When prev is not the list head, it must be a node in this list. */ > + if (prev != h && WARN_ON_ONCE(READ_ONCE(container_of( > + prev, struct bpf_list_node_kern, list_head)->owner) != head)) > + goto fail; > + > + /* new->owner != NULL implies !list_empty(n), no need to separately > * check the latter > */ > - if (cmpxchg(&node->owner, NULL, BPF_PTR_POISON)) { > - /* Only called from BPF prog, no need to migrate_disable */ > - __bpf_obj_drop_impl((void *)n - off, rec, false); > - return -EINVAL; > - } > - > - tail ? list_add_tail(n, h) : list_add(n, h); > - WRITE_ONCE(node->owner, head); > + if (cmpxchg(&new->owner, NULL, BPF_PTR_POISON)) > + goto fail; > > + list_add(n, prev); > + WRITE_ONCE(new->owner, head); > return 0; > + > +fail: > + /* Only called from BPF prog, no need to migrate_disable */ > + __bpf_obj_drop_impl((void *)n - off, rec, false); > + return -EINVAL; > } > This refactoring is worth. But it should be a preparatory patch. > __bpf_kfunc int bpf_list_push_front_impl(struct bpf_list_head *head, > struct bpf_list_node *node, > void *meta__ign, u64 off) > { > - struct bpf_list_node_kern *n = (void *)node; > + struct bpf_list_node_kern *new = (void *)node; > struct btf_struct_meta *meta = meta__ign; > + struct list_head *h = (void *)head; > > - return __bpf_list_add(n, head, false, meta ? meta->record : NULL, off); > + return __bpf_list_add(head, new, h, meta ? meta->record : NULL, off); Strange to change the positions of the first two args. Thanks, Leon > } > > __bpf_kfunc int bpf_list_push_back_impl(struct bpf_list_head *head, > struct bpf_list_node *node, > void *meta__ign, u64 off) > { > - struct bpf_list_node_kern *n = (void *)node; > + struct bpf_list_node_kern *new = (void *)node; > + struct btf_struct_meta *meta = meta__ign; > + struct list_head *h = (void *)head; > + > + return __bpf_list_add(head, new, h->prev, meta ? meta->record : NULL, off); > +} > + > +__bpf_kfunc int bpf_list_add_impl(struct bpf_list_head *head, > + struct bpf_list_node *new, > + struct bpf_list_node *prev, > + void *meta__ign, u64 off) > +{ > + struct bpf_list_node_kern *kn = (void *)new, *kp = (void *)prev; > struct btf_struct_meta *meta = meta__ign; > > - return __bpf_list_add(n, head, true, meta ? meta->record : NULL, off); > + return __bpf_list_add(head, kn, &kp->list_head, > + meta ? meta->record : NULL, off); > } > > static struct bpf_list_node *__bpf_list_del(struct bpf_list_head *head, > @@ -4563,6 +4584,7 @@ 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 c9557d3fb8dd..5f55b68ed935 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -12459,6 +12459,7 @@ enum special_kfunc_type { > KF_bpf_refcount_acquire_impl, > KF_bpf_list_push_front_impl, > KF_bpf_list_push_back_impl, > + KF_bpf_list_add_impl, > KF_bpf_list_pop_front, > KF_bpf_list_pop_back, > KF_bpf_list_del, > @@ -12520,6 +12521,7 @@ BTF_ID(func, bpf_obj_drop_impl) > BTF_ID(func, bpf_refcount_acquire_impl) > BTF_ID(func, bpf_list_push_front_impl) > BTF_ID(func, bpf_list_push_back_impl) > +BTF_ID(func, bpf_list_add_impl) > BTF_ID(func, bpf_list_pop_front) > BTF_ID(func, bpf_list_pop_back) > BTF_ID(func, bpf_list_del) > @@ -12996,6 +12998,7 @@ static bool is_bpf_list_api_kfunc(u32 btf_id) > { > return btf_id == special_kfunc_list[KF_bpf_list_push_front_impl] || > btf_id == special_kfunc_list[KF_bpf_list_push_back_impl] || > + btf_id == special_kfunc_list[KF_bpf_list_add_impl] || > btf_id == special_kfunc_list[KF_bpf_list_pop_front] || > btf_id == special_kfunc_list[KF_bpf_list_pop_back] || > btf_id == special_kfunc_list[KF_bpf_list_del] || > @@ -13122,6 +13125,7 @@ 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_add_impl] || > kfunc_btf_id == special_kfunc_list[KF_bpf_list_del]); > break; > case BPF_RB_NODE: > @@ -14264,6 +14268,7 @@ 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; > @@ -23230,13 +23235,17 @@ 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; > int node_offset_reg = BPF_REG_4; > > - /* rbtree_add has extra 'less' arg, so args-to-fixup are in diff regs */ > - if (desc->func_id == special_kfunc_list[KF_bpf_rbtree_add_impl]) { > + /* list/rbtree_add_impl have an extra arg (prev/less), > + * so args-to-fixup are in different regs. > + */ > + if (desc->func_id == special_kfunc_list[KF_bpf_list_add_impl] || > + desc->func_id == special_kfunc_list[KF_bpf_rbtree_add_impl]) { > struct_meta_reg = BPF_REG_4; > node_offset_reg = BPF_REG_5; > }