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Fri, 24 Jul 2026 12:08:32 -0700 (PDT) Received: from localhost ([2a03:2880:ff:47::]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2cf8efd828asm56717515ad.19.2026.07.24.12.08.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 24 Jul 2026 12:08:32 -0700 (PDT) From: Amery Hung To: bpf@vger.kernel.org Cc: alexei.starovoitov@gmail.com, andrii@kernel.org, daniel@iogearbox.net, eddyz87@gmail.com, memxor@gmail.com, ameryhung@gmail.com, kernel-team@meta.com Subject: [PATCH bpf-next v2 17/18] bpf: Classify scalar kfunc arguments from BTF Date: Fri, 24 Jul 2026 12:08:11 -0700 Message-ID: <20260724190813.1458271-18-ameryhung@gmail.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260724190813.1458271-1-ameryhung@gmail.com> References: <20260724190813.1458271-1-ameryhung@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Add kfunc scalar argument types, classify them in get_kfunc_arg_type() along side with pointer arguments and move scalar type verification into the main switch in check_kfunc_args(). This keeps BTF-based classification separate from register validation for every argument, paving the way for generating the kfunc argument prototype at add-call time. No functional change intended. Signed-off-by: Amery Hung --- kernel/bpf/verifier.c | 118 +++++++++++++++++++++++++++--------------- 1 file changed, 76 insertions(+), 42 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 3b357007e893..e44fc7296d0c 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -11099,6 +11099,11 @@ enum kfunc_ptr_arg_type { KF_ARG_PTR_TO_IRQ_FLAG, KF_ARG_PTR_TO_RES_SPIN_LOCK, KF_ARG_PTR_TO_TASK_WORK, + KF_ARG_CONST, /* const scalar */ + KF_ARG_CONST_MEM_SIZE, /* const scalar sizing a preceding memory arg */ + KF_ARG_CONST_ALLOC_SIZE_OR_ZERO, /* const scalar sizing a returned buffer */ + KF_ARG_MEM_SIZE, /* scalar sizing a preceding memory arg */ + KF_ARG_ANYTHING, /* unconstrained scalar */ }; enum special_kfunc_type { @@ -11355,14 +11360,40 @@ bool bpf_is_kfunc_pkt_changing(struct bpf_call_arg_meta *meta) } static int -get_kfunc_ptr_arg_type(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta, - const struct btf_type *t, const struct btf_type *ref_t, - const char *ref_tname, const struct btf_param *args, - int arg, int nargs, argno_t argno) +get_kfunc_arg_type(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta, + const struct btf_param *args, int arg, int nargs) { + const struct btf_type *t, *ref_t = NULL; + argno_t argno = argno_from_arg(arg + 1); + const char *ref_tname = NULL; bool arg_mem_size = false; int arg_type; + t = btf_type_skip_modifiers(meta->btf, args[arg].type, NULL); + + /* Scalar arguments are classified from their BTF suffix/name alone. */ + if (btf_type_is_scalar(t)) { + if (is_kfunc_arg_constant(meta->btf, &args[arg])) + return KF_ARG_CONST; + if (is_kfunc_arg_const_mem_size(meta->btf, &args[arg])) + return KF_ARG_CONST_MEM_SIZE; + if (is_kfunc_arg_mem_size(meta->btf, &args[arg])) + return KF_ARG_MEM_SIZE; + if (is_kfunc_arg_scalar_with_name(meta->btf, &args[arg], "rdonly_buf_size") || + is_kfunc_arg_scalar_with_name(meta->btf, &args[arg], "rdwr_buf_size")) + return KF_ARG_CONST_ALLOC_SIZE_OR_ZERO; + return KF_ARG_ANYTHING; + } + + if (!btf_type_is_ptr(t)) { + verbose(env, "Unrecognized %s type %s\n", + reg_arg_name(env, argno), btf_type_str(t)); + return -EINVAL; + } + + ref_t = btf_type_skip_modifiers(meta->btf, t->type, NULL); + ref_tname = btf_name_by_offset(meta->btf, ref_t->name_off); + /* In this function, we verify the kfunc's BTF as per the argument type, * leaving the rest of the verification with respect to the register * type to our caller. When a set of conditions hold in the BTF type of @@ -12051,7 +12082,6 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me int regno = reg_from_argno(argno); bool btf_id_fixed_off_ok = true; u32 ref_id, type_size; - bool is_ret_buf_sz = false; int kf_arg_type; if (is_kfunc_arg_prog_aux(btf, &args[i])) { @@ -12075,39 +12105,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me t = btf_type_skip_modifiers(btf, args[i].type, NULL); - if (btf_type_is_scalar(t)) { - if (reg->type != SCALAR_VALUE) { - verbose(env, "%s is not a scalar\n", reg_arg_name(env, argno)); - return -EINVAL; - } - - if (is_kfunc_arg_constant(meta->btf, &args[i]) || - is_kfunc_arg_const_mem_size(meta->btf, &args[i])) { - ret = process_const_arg(env, reg, argno, meta); - if (ret < 0) - return ret; - } else if (is_kfunc_arg_scalar_with_name(btf, &args[i], "rdonly_buf_size")) { - meta->r0_rdonly = true; - is_ret_buf_sz = true; - } else if (is_kfunc_arg_scalar_with_name(btf, &args[i], "rdwr_buf_size")) { - is_ret_buf_sz = true; - } - - if (is_ret_buf_sz) { - ret = process_const_alloc_mem_size(env, reg, argno, &meta->ret_mem); - if (ret < 0) - return ret; - } - continue; - } - - if (!btf_type_is_ptr(t)) { - verbose(env, "Unrecognized %s type %s\n", - reg_arg_name(env, argno), btf_type_str(t)); - return -EINVAL; - } - - if ((bpf_register_is_null(reg) || type_may_be_null(reg->type)) && + if (btf_type_is_ptr(t) && (bpf_register_is_null(reg) || type_may_be_null(reg->type)) && !is_kfunc_arg_nullable(meta->btf, &args[i])) { verbose(env, "Possibly NULL pointer passed to trusted %s\n", reg_arg_name(env, argno)); @@ -12124,11 +12122,12 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me if (reg_is_referenced(env, reg)) update_ref_obj(&meta->ref_obj, reg); - ref_t = btf_type_skip_modifiers(btf, t->type, &ref_id); - ref_tname = btf_name_by_offset(btf, ref_t->name_off); + if (btf_type_is_ptr(t)) { + ref_t = btf_type_skip_modifiers(btf, t->type, &ref_id); + ref_tname = btf_name_by_offset(btf, ref_t->name_off); + } - kf_arg_type = get_kfunc_ptr_arg_type(env, meta, t, ref_t, ref_tname, - args, i, nargs, argno); + kf_arg_type = get_kfunc_arg_type(env, meta, args, i, nargs); if (kf_arg_type < 0) return kf_arg_type; @@ -12142,6 +12141,11 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me } switch (base_type(kf_arg_type)) { + case KF_ARG_CONST: + case KF_ARG_CONST_MEM_SIZE: + case KF_ARG_MEM_SIZE: + case KF_ARG_ANYTHING: + case KF_ARG_CONST_ALLOC_SIZE_OR_ZERO: case KF_ARG_PTR_TO_ALLOC_BTF_ID: case KF_ARG_PTR_TO_BTF_ID: case KF_ARG_CONST_MAP_PTR: @@ -12182,6 +12186,36 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me return ret; switch (base_type(kf_arg_type)) { + case KF_ARG_CONST: + case KF_ARG_CONST_MEM_SIZE: + if (reg->type != SCALAR_VALUE) { + verbose(env, "%s is not a scalar\n", reg_arg_name(env, argno)); + return -EINVAL; + } + + ret = process_const_arg(env, reg, argno, meta); + if (ret < 0) + return ret; + break; + case KF_ARG_MEM_SIZE: + case KF_ARG_ANYTHING: + if (reg->type != SCALAR_VALUE) { + verbose(env, "%s is not a scalar\n", reg_arg_name(env, argno)); + return -EINVAL; + } + break; + case KF_ARG_CONST_ALLOC_SIZE_OR_ZERO: + if (reg->type != SCALAR_VALUE) { + verbose(env, "%s is not a scalar\n", reg_arg_name(env, argno)); + return -EINVAL; + } + + if (is_kfunc_arg_scalar_with_name(btf, &args[i], "rdonly_buf_size")) + meta->r0_rdonly = true; + ret = process_const_alloc_mem_size(env, reg, argno, &meta->ret_mem); + if (ret < 0) + return ret; + break; case KF_ARG_PTR_TO_CTX: if (reg->type != PTR_TO_CTX) { verbose(env, "%s expected pointer to ctx, but got %s\n", -- 2.52.0