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Wed, 04 Mar 2026 06:35:36 -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, linux-kselftest@vger.kernel.org Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v6 2/5] bpf: Add bpf_list_add_impl to insert node after a given list node Date: Wed, 4 Mar 2026 22:34:56 +0800 Message-ID: <20260304143459.78059-3-pilgrimtao@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260304143459.78059-1-pilgrimtao@gmail.com> References: <20260304143459.78059-1-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: quoted-printable Content-Type: text/plain; charset="utf-8" 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 | 34 ++++++++++++++++++++++++++++++++++ kernel/bpf/verifier.c | 17 +++++++++++++---- 2 files changed, 47 insertions(+), 4 deletions(-) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index cc1a096a1f64..740b53024283 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2505,6 +2505,39 @@ __bpf_kfunc struct bpf_list_node *bpf_list_back(stru= ct bpf_list_head *head) return (struct bpf_list_node *)h->prev; } =20 +__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 =3D (void *)new, *kp =3D (void *)prev; + struct btf_struct_meta *meta =3D meta__ign; + struct list_head *n =3D &kn->list_head, *p =3D &kp->list_head; + struct list_head *h =3D (void *)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); + goto fail; + } + + if (WARN_ON_ONCE(READ_ONCE(kp->owner) !=3D head)) + goto fail; + + if (cmpxchg(&kn->owner, NULL, BPF_PTR_POISON)) + goto fail; + + list_add(n, p); + WRITE_ONCE(kn->owner, head); + return 0; + +fail: + __bpf_obj_drop_impl((void *)n - off, meta ? meta->record : NULL, false); + return -EINVAL; +} + __bpf_kfunc struct bpf_rb_node *bpf_rbtree_remove(struct bpf_rb_root *root, struct bpf_rb_node *node) { @@ -4574,6 +4607,7 @@ 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..e458cf3b1dd1 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 =3D=3D special_kfunc_list[KF_bpf_list_pop_back] || btf_id =3D=3D special_kfunc_list[KF_bpf_list_del] || btf_id =3D=3D special_kfunc_list[KF_bpf_list_front] || - btf_id =3D=3D special_kfunc_list[KF_bpf_list_back]; + btf_id =3D=3D special_kfunc_list[KF_bpf_list_back] || + btf_id =3D=3D special_kfunc_list[KF_bpf_list_add_impl]; } =20 static bool is_bpf_rbtree_api_kfunc(u32 btf_id) @@ -13122,7 +13125,8 @@ static bool check_kfunc_is_graph_node_api(struct bp= f_verifier_env *env, case BPF_LIST_NODE: ret =3D (kfunc_btf_id =3D=3D special_kfunc_list[KF_bpf_list_push_front_i= mpl] || kfunc_btf_id =3D=3D special_kfunc_list[KF_bpf_list_push_back_impl= ] || - kfunc_btf_id =3D=3D special_kfunc_list[KF_bpf_list_del]); + kfunc_btf_id =3D=3D special_kfunc_list[KF_bpf_list_del] || + kfunc_btf_id =3D=3D special_kfunc_list[KF_bpf_list_add_impl]); break; case BPF_RB_NODE: ret =3D (kfunc_btf_id =3D=3D 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, =20 if (meta.func_id =3D=3D special_kfunc_list[KF_bpf_list_push_front_impl] || meta.func_id =3D=3D special_kfunc_list[KF_bpf_list_push_back_impl] || + meta.func_id =3D=3D special_kfunc_list[KF_bpf_list_add_impl] || meta.func_id =3D=3D special_kfunc_list[KF_bpf_rbtree_add_impl]) { release_ref_obj_id =3D regs[BPF_REG_2].ref_obj_id; insn_aux->insert_off =3D regs[BPF_REG_2].off; @@ -23230,13 +23235,17 @@ static int fixup_kfunc_call(struct bpf_verifier_e= nv *env, struct bpf_insn *insn, *cnt =3D 3; } else if (desc->func_id =3D=3D special_kfunc_list[KF_bpf_list_push_back_= impl] || desc->func_id =3D=3D special_kfunc_list[KF_bpf_list_push_front_impl] = || + desc->func_id =3D=3D special_kfunc_list[KF_bpf_list_add_impl] || desc->func_id =3D=3D special_kfunc_list[KF_bpf_rbtree_add_impl]) { struct btf_struct_meta *kptr_struct_meta =3D env->insn_aux_data[insn_idx= ].kptr_struct_meta; int struct_meta_reg =3D BPF_REG_3; int node_offset_reg =3D BPF_REG_4; =20 - /* rbtree_add has extra 'less' arg, so args-to-fixup are in diff regs */ - if (desc->func_id =3D=3D 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 =3D=3D special_kfunc_list[KF_bpf_list_add_impl] || + desc->func_id =3D=3D special_kfunc_list[KF_bpf_rbtree_add_impl]) { struct_meta_reg =3D BPF_REG_4; node_offset_reg =3D BPF_REG_5; } --=20 2.50.1 (Apple Git-155)