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bpf: Recognize '__map' suffix in kfunc arguments 

Recognize 'void *p__map' kfunc argument as 'struct bpf_map *p__map'.
It allows kfunc to have 'void *' argument for maps, since bpf progs
will call them as:
struct {
        __uint(type, BPF_MAP_TYPE_ARENA);
	...
} arena SEC(".maps");

bpf_kfunc_with_map(... &arena ...);

Underneath libbpf will load CONST_PTR_TO_MAP into the register via ld_imm64
insn. If kfunc was defined with 'struct bpf_map *' it would pass the
verifier as well, but bpf prog would need to type cast the argument
(void *)&arena, which is not clean.

Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20240307031228.42896-3-alexei.starovoitov@gmail.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
This commit is contained in:
Alexei Starovoitov 2024-03-06 19:12:24 -08:00 committed by Martin KaFai Lau
parent 88d1d4a7ee
commit 8d94f1357c
1 changed files with 16 additions and 0 deletions
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16
kernel/bpf/verifier.c
View File

@ -10752,6 +10752,11 @@ static bool is_kfunc_arg_ignore(const struct btf *btf, const struct btf_param *a
return btf_param_match_suffix(btf, arg, "__ign");
}
static bool is_kfunc_arg_map(const struct btf *btf, const struct btf_param *arg)
{
return btf_param_match_suffix(btf, arg, "__map");
}
static bool is_kfunc_arg_alloc_obj(const struct btf *btf, const struct btf_param *arg)
{
return btf_param_match_suffix(btf, arg, "__alloc");
@ -10921,6 +10926,7 @@ enum kfunc_ptr_arg_type {
KF_ARG_PTR_TO_RB_NODE,
KF_ARG_PTR_TO_NULL,
KF_ARG_PTR_TO_CONST_STR,
KF_ARG_PTR_TO_MAP,
};
enum special_kfunc_type {
@ -11074,6 +11080,9 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,
if (is_kfunc_arg_const_str(meta->btf, &args[argno]))
return KF_ARG_PTR_TO_CONST_STR;
if (is_kfunc_arg_map(meta->btf, &args[argno]))
return KF_ARG_PTR_TO_MAP;
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",
@ -11674,6 +11683,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
switch (kf_arg_type) {
case KF_ARG_PTR_TO_NULL:
continue;
case KF_ARG_PTR_TO_MAP:
case KF_ARG_PTR_TO_ALLOC_BTF_ID:
case KF_ARG_PTR_TO_BTF_ID:
if (!is_kfunc_trusted_args(meta) && !is_kfunc_rcu(meta))
@ -11890,6 +11900,12 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
if (ret < 0)
return ret;
break;
case KF_ARG_PTR_TO_MAP:
/* If argument has '__map' suffix expect 'struct bpf_map *' */
ref_id = *reg2btf_ids[CONST_PTR_TO_MAP];
ref_t = btf_type_by_id(btf_vmlinux, ref_id);
ref_tname = btf_name_by_offset(btf, ref_t->name_off);
fallthrough;
case KF_ARG_PTR_TO_BTF_ID:
/* Only base_type is checked, further checks are done here */
if ((base_type(reg->type) != PTR_TO_BTF_ID ||