From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f54.google.com (mail-pj1-f54.google.com [209.85.216.54]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 99F7321A453 for ; Wed, 25 Feb 2026 09:28:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.54 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772011714; cv=none; b=jLOJkUBwmONdTA+bR+NJW+lCcrPdeCwWuEOwbNy9gdGIqf363U1xLDkes2hHumtyMULJhONb+bwH6sqhDybH1aJ6D0ebEF5KzKALO7Evy8hw/vRu7V3eX8gUom0gHtJLV8JLTl5As6fFotoB1Z4SyjLD5vB4adnG+KagTiF1alM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772011714; c=relaxed/simple; bh=MtGZ1s9d0Ohu8LVtS1x+dMK9rylCalqlFA6D7V3l7Ro=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=rzb3sY+oBGWpOJCOJCzfokBgrhu/PkQAB5Oq1dWdozXWzSlmTzlDOKg7ed9SbXl+RZREUVlsF5alPbd/a4tLkKujNRL5wVJH2Wooh1tSY324b+9B7Y3IihJVjkTBmkxtFEgLBZ1UStUAY0QtoCu+iMBaKCnLZvM0P1Jn19xqNrc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=IJ7vnRzM; arc=none smtp.client-ip=209.85.216.54 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="IJ7vnRzM" Received: by mail-pj1-f54.google.com with SMTP id 98e67ed59e1d1-3591cc98871so41258a91.3 for ; Wed, 25 Feb 2026 01:28:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1772011713; x=1772616513; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=jcNjMPltPtLcCQ8lC4dQD+ECjUO8JYcdiEXegBoi6yA=; b=IJ7vnRzMWIosw+fn1X84Dv/FciYW0nbnyW6ij8AoUaJqLsFPG92mHyaYBSrkG6hd5w vNOxXanELbPPw1DqtHSirSc5LItDmpwXd2m0ukyx/LH8z4SW+Jdu1OzCTv0vvHzXQVZu btsSavK2hE10aN/jVxxMbk+S/gKqlooLnmRKcIufkn9C1tID7xJIGUDsGMBzd/BQUuLd jR7jYuV9Axjg2eZG9Gv3/3CRGrHCSZs6qzxEN82tcQr5ZKtziw2L0cohj3Cumu1dQSH+ ADnYk+OgN11OVhZVOMrT2wVkfrOV3OeA/wZgkQu8qgbTRWOH0q5DR6eDiAqKhg+75ymW h5mQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1772011713; x=1772616513; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=jcNjMPltPtLcCQ8lC4dQD+ECjUO8JYcdiEXegBoi6yA=; b=v1XaRXQVLjwzCYpWF/J8Op1e9RPcuT6L66BsndVnUpUKYA+eVgNGQtky+aHlgDiPcX a2n90bsZArSbsmXtDGlaJvKPagtHHXTnslKJQCwiul6rPavkJvBal3z7NphbjAnam/Fo ZiEiE3tJohbbab3XtgtDOMv/zPPf3aMb2ChU51onLyrQiR+8o8apvtXp2U/Kd3EuycGA POcTNXHa/PXtIqXtIUncm+b4bxkvelZhSdjnwEHixdveKxAbIvBV78YaVm7wQpXXF0BL lYhwYyAoiWMNNVIpWF95Vo6m/Sn8DTBCe94N2ZlpUDBWHh9NGjVvezPMohkPZHNIkFz2 uxhA== X-Forwarded-Encrypted: i=1; AJvYcCWFV3tBmcxQekH0r9XN45pmH/OZ7qCI2owQY7woORgCHSW4IiJTXrwi70GFRI0+2rrgLFNFDS905BHJtQg=@vger.kernel.org X-Gm-Message-State: AOJu0Ywvzj29h8Wq6BhFelkDd9658qROUCFwrQzK1bclrx7PuYpCz+nZ 0RWTtoFaOEZT+5P/sHu3YB5W0SPUzzxBj3OTGTra/M5h3Onax0MVTmIf X-Gm-Gg: ATEYQzyewiZo97Fug3TZfUDnSthO6tjIvqQJ+9MU7YGAqdY1KvMG7eodTXJrlSoXVsW B9qEIRHX4YtdtRUMnMDcxcpWobPHPE4JUYEEeQpC1wo9h7KfSpYVgMUdcySjTrygZoLTD64ZoUr /SMovJLf4Mpoz8IoKDXmCS8zkmNzAdJvi4yCl1BH0yjSqab+yxJ2yh0J9i+5TXSxRroaKDC51Y1 UHDX2+Fz5etE8c+EAjR3eMyGtPre1dzK6WODewtbED5H45V7NV+ubT8fLNrvoaasB1CM7lftkcS KDmI9dv0fsC0A5dFRoiiK8vkuTh1RGTq7dWM48iLwHlbPVgNItNtLBzZRwlk3xZ0UcPMl2B/2wp iCiNXpdMLky5XOAZTBxt9FRHBIfo98ALDPpNcRa3G+2BMVW0oBZCYBbjADnlyT5OvjjEt6ptwAA jBpCDN8IcPlrmCUVf8u2SjuXcZaMSOEj0rMFxuo3cyoHwj5mBFs/dWqXzhkGNaaUhG X-Received: by 2002:a17:90b:4c4f:b0:358:e7bc:429 with SMTP id 98e67ed59e1d1-358e7bc080bmr4543609a91.0.1772011712956; Wed, 25 Feb 2026 01:28:32 -0800 (PST) Received: from localhost.localdomain ([113.218.252.140]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-35912f5f29fsm837901a91.1.2026.02.25.01.28.14 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Wed, 25 Feb 2026 01:28:32 -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 5/6] bpf: add bpf_list_is_first/last/empty kfuncs Date: Wed, 25 Feb 2026 17:26:50 +0800 Message-ID: <20260225092651.94689-6-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 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 --- 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)