On Fri, Feb 09, 2024 at 10:57:45AM -0600, David Vernet wrote:
> 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;
Makes sense, but then should I add the following on top:
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index e970d9fd7f32..b524dc168023 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -11088,13 +11088,16 @@ 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) && !btf_type_is_void(ref_t)) {
+ if (!btf_type_is_struct(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 is_kfunc_arg_map(meta->btf, &args[argno]) ? KF_ARG_PTR_TO_MAP : KF_ARG_PTR_TO_BTF_ID;
+ return KF_ARG_PTR_TO_BTF_ID;
}
?
