On Tue, Feb 06, 2024 at 02:04:27PM -0800, Alexei Starovoitov wrote:
> From: Alexei Starovoitov <ast@xxxxxxxxxx>
>
> 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, but bpf prog would need to use '(void *)&arena'.
> Which is not clean.
>
> Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
> ---
> kernel/bpf/verifier.c | 14 +++++++++++++-
> 1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index d9c2dbb3939f..db569ce89fb1 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -10741,6 +10741,11 @@ static bool is_kfunc_arg_ignore(const struct btf *btf, const struct btf_param *a
> return __kfunc_param_match_suffix(btf, arg, "__ign");
> }
>
> +static bool is_kfunc_arg_map(const struct btf *btf, const struct btf_param *arg)
> +{
> + return __kfunc_param_match_suffix(btf, arg, "__map");
> +}
> +
> static bool is_kfunc_arg_alloc_obj(const struct btf *btf, const struct btf_param *arg)
> {
> return __kfunc_param_match_suffix(btf, arg, "__alloc");
> @@ -11064,7 +11069,7 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,
> 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)) {
> + if (!btf_type_is_struct(ref_t) && !btf_type_is_void(ref_t)) {
> verbose(env, "kernel function %s args#%d pointer type %s %s is not supported\n",
> meta->func_name, argno, btf_type_str(ref_t), ref_tname);
> return -EINVAL;
> @@ -11660,6 +11665,13 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
> if (kf_arg_type < 0)
> return kf_arg_type;
>
> + if (is_kfunc_arg_map(btf, &args[i])) {
> + /* 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);
> + }
This is fine, but given that this should only apply to KF_ARG_PTR_TO_BTF_ID,
this seems a bit cleaner, wdyt?
index ddaf09db1175..998da8b302ac 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -10741,6 +10741,11 @@ static bool is_kfunc_arg_ignore(const struct btf *btf, const struct btf_param *a
return __kfunc_param_match_suffix(btf, arg, "__ign");
}
+static bool is_kfunc_arg_map(const struct btf *btf, const struct btf_param *arg)
+{
+ return __kfunc_param_match_suffix(btf, arg, "__map");
+}
+
static bool is_kfunc_arg_alloc_obj(const struct btf *btf, const struct btf_param *arg)
{
return __kfunc_param_match_suffix(btf, arg, "__alloc");
@@ -10910,6 +10915,7 @@ 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, /* pointer to a struct bpf_map */
};
enum special_kfunc_type {
@@ -11064,12 +11070,12 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,
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)) {
+ if (!btf_type_is_struct(ref_t) && !btf_type_is_void(ref_t)) {
verbose(env, "kernel function %s args#%d pointer type %s %s is not supported\n",
meta->func_name, argno, btf_type_str(ref_t), ref_tname);
return -EINVAL;
}
- return KF_ARG_PTR_TO_BTF_ID;
+ return is_kfunc_arg_map(meta->btf, &args[argno]) ? KF_ARG_PTR_TO_MAP : KF_ARG_PTR_TO_BTF_ID;
}
if (is_kfunc_arg_callback(env, meta->btf, &args[argno]))
@@ -11663,6 +11669,7 @@ 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))
@@ -11879,6 +11886,13 @@ 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 ||
> +
> switch (kf_arg_type) {
> case KF_ARG_PTR_TO_NULL:
> continue;
> --
> 2.34.1
>
>
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