From 045edee19d591e59ed53772bf6dfc9b1ed9577eb Mon Sep 17 00:00:00 2001 From: Song Liu Date: Mon, 6 Nov 2023 20:57:25 -0800 Subject: bpf: Introduce KF_ARG_PTR_TO_CONST_STR Similar to ARG_PTR_TO_CONST_STR for BPF helpers, KF_ARG_PTR_TO_CONST_STR specifies kfunc args that point to const strings. Annotation "__str" is used to specify kfunc arg of type KF_ARG_PTR_TO_CONST_STR. Also, add documentation for the "__str" annotation. bpf_get_file_xattr() will be the first kfunc that uses this type. Signed-off-by: Song Liu Signed-off-by: Andrii Nakryiko Acked-by: Andrii Nakryiko Acked-by: Vadim Fedorenko Link: https://lore.kernel.org/bpf/20231107045725.2278852-4-song@kernel.org Signed-off-by: Alexei Starovoitov --- Documentation/bpf/kfuncs.rst | 24 ++++++++++++++++++++++++ kernel/bpf/verifier.c | 19 +++++++++++++++++++ 2 files changed, 43 insertions(+) diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst index 723408e399ab..7985c6615f3c 100644 --- a/Documentation/bpf/kfuncs.rst +++ b/Documentation/bpf/kfuncs.rst @@ -135,6 +135,30 @@ Either way, the returned buffer is either NULL, or of size buffer_szk. Without t annotation, the verifier will reject the program if a null pointer is passed in with a nonzero size. +2.2.5 __str Annotation +---------------------------- +This annotation is used to indicate that the argument is a constant string. + +An example is given below:: + + __bpf_kfunc bpf_get_file_xattr(..., const char *name__str, ...) + { + ... + } + +In this case, ``bpf_get_file_xattr()`` can be called as:: + + bpf_get_file_xattr(..., "xattr_name", ...); + +Or:: + + const char name[] = "xattr_name"; /* This need to be global */ + int BPF_PROG(...) + { + ... + bpf_get_file_xattr(..., name, ...); + ... + } .. _BPF_kfunc_nodef: diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 637f34231633..9276e0abcb4b 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -10810,6 +10810,11 @@ static bool is_kfunc_arg_nullable(const struct btf *btf, const struct btf_param return __kfunc_param_match_suffix(btf, arg, "__nullable"); } +static bool is_kfunc_arg_const_str(const struct btf *btf, const struct btf_param *arg) +{ + return __kfunc_param_match_suffix(btf, arg, "__str"); +} + static bool is_kfunc_arg_scalar_with_name(const struct btf *btf, const struct btf_param *arg, const char *name) @@ -10953,6 +10958,7 @@ enum kfunc_ptr_arg_type { KF_ARG_PTR_TO_RB_ROOT, KF_ARG_PTR_TO_RB_NODE, KF_ARG_PTR_TO_NULL, + KF_ARG_PTR_TO_CONST_STR, }; enum special_kfunc_type { @@ -11103,6 +11109,9 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env, if (is_kfunc_arg_rbtree_node(meta->btf, &args[argno])) return KF_ARG_PTR_TO_RB_NODE; + if (is_kfunc_arg_const_str(meta->btf, &args[argno])) + return KF_ARG_PTR_TO_CONST_STR; + if ((base_type(reg->type) == PTR_TO_BTF_ID || reg2btf_ids[base_type(reg->type)])) { if (!btf_type_is_struct(ref_t)) { verbose(env, "kernel function %s args#%d pointer type %s %s is not supported\n", @@ -11734,6 +11743,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ case KF_ARG_PTR_TO_MEM_SIZE: case KF_ARG_PTR_TO_CALLBACK: case KF_ARG_PTR_TO_REFCOUNTED_KPTR: + case KF_ARG_PTR_TO_CONST_STR: /* Trusted by default */ break; default: @@ -12005,6 +12015,15 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ meta->arg_btf = reg->btf; meta->arg_btf_id = reg->btf_id; break; + case KF_ARG_PTR_TO_CONST_STR: + if (reg->type != PTR_TO_MAP_VALUE) { + verbose(env, "arg#%d doesn't point to a const string\n", i); + return -EINVAL; + } + ret = check_reg_const_str(env, reg, regno); + if (ret) + return ret; + break; } } -- cgit