From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-181.mta1.migadu.com (out-181.mta1.migadu.com [95.215.58.181]) (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 54DE03537D6 for ; Wed, 4 Mar 2026 03:29:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.181 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772594960; cv=none; b=KmugUqJswVMqCsOM1snQNd3xNPBtUuSNm64VztBGDK8+LLThCPSq0RNDKKF6+WAS1tZmZl3Ka6C78E8M7uQNi3DtCDUivVIFysHXIr0BS2MCbaQ1LsmwV+SdjqkB2hHjVd3GhMR7OByzjUuAQvWwBXzhOM0s4DS9FaLDIDucYcI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772594960; c=relaxed/simple; bh=0hzv2xhvechn9sHUAnZoW1fRftyh5ZrNmVoIgKw4E98=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=pk7uLNaCzQ0bzHb/6JiovNb+OKSmN+r0+Lr7YpGEWmNobwDSk8EoPq2aXpHMltY/DkzNbpzYWFz4psodVol/BYBJ2UGtV1fJRta9dN3W/V/Ra/wlgdipTxwxQObPfVASquRmm3SWD8Ntg5DQzOSBWfbLVtHRbgtoOPVBIqqx5+U= 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=acqJpgFv; arc=none smtp.client-ip=95.215.58.181 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="acqJpgFv" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1772594957; 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=OEpRNSH5ADcIRXvmOmBT4RbUgn1P97XMtCnamERhLyU=; b=acqJpgFvh/zPyfWdUeTX8xPAkp2MsWh0NVSx+lG4mvyDtXqlWfvqbyjE2ettTpAJvYQ+kz eNZEHLFRI43HZjxXZmKlV/VgKQvAHDfc4lVlKbO55bvjJeKXeRTgT6zR13sfqLJSoeftCN /5ZsCIu3aNhquRS6b4ZSMNolCGtJGlM= Date: Wed, 4 Mar 2026 11:29:06 +0800 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v4 3/6] 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: <20260303135219.33726-1-pilgrimtao@gmail.com> <20260303135219.33726-4-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: <20260303135219.33726-4-pilgrimtao@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 3/3/26 21:52, 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 | 27 +++++++++++++++++++++++++++ > kernel/bpf/verifier.c | 14 ++++++++++---- > 2 files changed, 37 insertions(+), 4 deletions(-) > > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c > index 19d88da8e694..488810da8f30 100644 > --- a/kernel/bpf/helpers.c > +++ b/kernel/bpf/helpers.c > @@ -2497,6 +2497,32 @@ __bpf_kfunc struct bpf_list_node *bpf_list_back(struct bpf_list_head *head) > return (struct bpf_list_node *)h->prev; > } > > +__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; > + struct list_head *n = &kn->list_head, *p = &kp->list_head; > + > + if (unlikely(!head)) > + return -EINVAL; Should the head handling be kept consistent with __bpf_list_add()? > + > + if (WARN_ON_ONCE(READ_ONCE(kp->owner) != head)) > + return -EINVAL; > + > + if (cmpxchg(&kn->owner, NULL, BPF_PTR_POISON)) { > + __bpf_obj_drop_impl((void *)n - off, > + meta ? meta->record : NULL, false); > + return -EINVAL; > + } > + > + list_add(n, p); > + WRITE_ONCE(kn->owner, head); > + return 0; > +} > + > __bpf_kfunc struct bpf_rb_node *bpf_rbtree_remove(struct bpf_rb_root *root, > struct bpf_rb_node *node) > { > @@ -4566,6 +4592,7 @@ 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..6dfd4afff1cf 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -12464,6 +12464,7 @@ 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, > @@ -12525,6 +12526,7 @@ 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) > @@ -13000,7 +13002,8 @@ 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) > @@ -13122,7 +13125,8 @@ 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] || > @@ -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 +23235,14 @@ 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 */ Why drop this comment? Please add a comment explaining the reason for adding the KF_bpf_list_add_impl check here. Thanks, Leon > - if (desc->func_id == special_kfunc_list[KF_bpf_rbtree_add_impl]) { > + 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; > }