On Wed, Dec 1, 2021 at 2:21 PM Hao Luo <haoluo@xxxxxxxxxx> wrote:
>
> On Wed, Dec 1, 2021 at 12:34 PM Alexei Starovoitov
> <alexei.starovoitov@xxxxxxxxx> wrote:
> >
> > On Mon, Nov 29, 2021 at 05:29:47PM -0800, Hao Luo wrote:
> > >
> > > +
> > > struct bpf_reg_types {
> > > const enum bpf_reg_type types[10];
> > > u32 *btf_id;
> > > +
> > > + /* Certain types require customized type matching function. */
> > > + bool (*type_match_fn)(enum bpf_arg_type arg_type,
> > > + enum bpf_reg_type type,
> > > + enum bpf_reg_type expected);
> > > };
> > >
> > > static const struct bpf_reg_types map_key_value_types = {
> > > @@ -5013,6 +5019,19 @@ static const struct bpf_reg_types btf_id_sock_common_types = {
> > > };
> > > #endif
> > >
> > > +static bool mem_type_match(enum bpf_arg_type arg_type,
> > > + enum bpf_reg_type type, enum bpf_reg_type expected)
> > > +{
> > > + /* If arg_type is tagged with MEM_RDONLY, type is compatible with both
> > > + * RDONLY and RDWR mem, fold the MEM_RDONLY flag in 'type' before
> > > + * comparison.
> > > + */
> > > + if ((arg_type & MEM_RDONLY) != 0)
> > > + type &= ~MEM_RDONLY;
> > > +
> > > + return type == expected;
> > > +}
> > > +
> > > static const struct bpf_reg_types mem_types = {
> > > .types = {
> > > PTR_TO_STACK,
> > > @@ -5022,8 +5041,8 @@ static const struct bpf_reg_types mem_types = {
> > > PTR_TO_MAP_VALUE,
> > > PTR_TO_MEM,
> > > PTR_TO_BUF,
> > > - PTR_TO_BUF | MEM_RDONLY,
> > > },
> > > + .type_match_fn = mem_type_match,
> >
> > why add a callback for this logic?
> > Isn't it a universal rule for MEM_RDONLY?
>
> Ah, good point, I didn't realize that. Maybe, not only MEM_RDONLY, but
> all flags can be checked in the same way? Like the following
>
> static const struct bpf_reg_types int_ptr_types = {
> @@ -5097,6 +5116,13 @@ static int check_reg_type(struct
> bpf_verifier_env *env, u32 regno,
> if (expected == NOT_INIT)
> break;
>
> + flag = bpf_type_flag(arg_type);
>
> - if (type == expected)
> + if ((type & ~flag) == expected)
> goto found;
> }
I think for MAYBE_NULL and MEM_RDONLY that would be correct,
but not necessarily apply to future flags.
I would open code it for these specific flags.
Also what do you think about dropping bpf_ prefix from type_flag()?
It won't conflict with anything and less verbose.
