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 188D6383316 for ; Thu, 21 May 2026 03:24:47 +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=1779333889; cv=none; b=TPqFEWazSiPb1OQutAxdwfuB3SjRhZhl8Xzb9T34Tv2HD6IH77B6AMRutf6jVAYa2IK5abX2Wb8lmxVHzyO4o65DBvsAJEQmUz8JWBrk8kmCw8ATrRFCIXmDmnqlMgRv2pJUf7if1r2CtQB6qlT6h7CezLjFcyZ8J80X3Q6RUs4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779333889; c=relaxed/simple; bh=e0BLPZF0W2n+jN/JnZKz67oRVTlrLWBUGzpdlvERSKk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=f1r+qt81mg8X4iE2uSE/Jc7uN/K13hiAdtZyzaIswZPXpGsC1X8SIaj8TtSkTxhiEr3xE9Rkrh9F51yOnD5Bg1ZNLLTv9vd6nxQxOpwYeHwdtdsnSJgKJxXbtsqDB3pJUwsv1kNNdxV5x6Hy+WzBjd/IiA/2+bQtJ+c8bMZPnTY= 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=hHQ8FKXt; 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="hHQ8FKXt" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1779333886; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ElWLdrCbk8g1PoRY5Me2SOYGZbdC80GXt7KhUPW29fY=; b=hHQ8FKXtOwvBV/1S2ldKNZWC8T1xf03OX4IiS056QwTgQuMA+NlGwxb4wAcl0qvPo843kA W9/4DFagL8QPo2Fc/9vW44hwMyAC809D1Ai2XGXR5KeniaZZgvuSFdlqMVpoL98kt1+OXU rOqiEl42FGvwf/fJqgs9oVKEYK/wavg= From: Kaitao Cheng To: ast@kernel.org, corbet@lwn.net, martin.lau@linux.dev, 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, skhan@linuxfoundation.org, memxor@gmail.com Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, vmalik@redhat.com, linux-kselftest@vger.kernel.org, Emil Tsalapatis Subject: [PATCH bpf-next v11 7/8] bpf: add bpf_list_is_first/last/empty kfuncs Date: Thu, 21 May 2026 11:23:05 +0800 Message-ID: <20260521032306.97118-8-kaitao.cheng@linux.dev> In-Reply-To: <20260521032306.97118-1-kaitao.cheng@linux.dev> References: <20260521032306.97118-1-kaitao.cheng@linux.dev> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT From: Kaitao Cheng 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. Currently, without these kfuncs, to implement the above functionality it is 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 Reviewed-by: Emil Tsalapatis --- kernel/bpf/helpers.c | 40 ++++++++++++++++++++++++++++++++++++++++ kernel/bpf/verifier.c | 15 +++++++++++++-- 2 files changed, 53 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 89579165ef4d..b6c3d02d5593 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2656,6 +2656,43 @@ __bpf_kfunc struct bpf_list_node *bpf_list_back(struct bpf_list_head *head) return (struct bpf_list_node *)h->prev; } +__bpf_kfunc bool bpf_list_is_first(struct bpf_list_head *head, + struct bpf_list_node *node__nonown_allowed) +{ + struct list_head *h = (struct list_head *)head; + struct bpf_list_node_kern *kn = (struct bpf_list_node_kern *)node__nonown_allowed; + + if (READ_ONCE(kn->owner) != head) + return false; + + return list_is_first(&kn->list_head, h); +} + +__bpf_kfunc bool bpf_list_is_last(struct bpf_list_head *head, + struct bpf_list_node *node__nonown_allowed) +{ + struct list_head *h = (struct list_head *)head; + struct bpf_list_node_kern *kn = (struct bpf_list_node_kern *)node__nonown_allowed; + + if (READ_ONCE(kn->owner) != head) + return false; + + return list_is_last(&kn->list_head, h); +} + +__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) { @@ -4772,6 +4809,9 @@ 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_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 662ad7312697..d9bdc3b32c05 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -10965,6 +10965,9 @@ enum special_kfunc_type { KF_bpf_list_del, KF_bpf_list_front, KF_bpf_list_back, + 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, @@ -11035,6 +11038,9 @@ 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_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) @@ -11556,7 +11562,10 @@ 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_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) @@ -11678,7 +11687,9 @@ static bool check_kfunc_is_graph_node_api(struct bpf_verifier_env *env, switch (node_field_type) { case BPF_LIST_NODE: ret = is_bpf_list_push_kfunc(kfunc_btf_id) || - 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_is_first] || + kfunc_btf_id == special_kfunc_list[KF_bpf_list_is_last]; break; case BPF_RB_NODE: ret = (is_bpf_rbtree_add_kfunc(kfunc_btf_id) || -- 2.50.1 (Apple Git-155)