Martin KaFai Lau <kafai@xxxxxx> [Wed, 2020-06-17 23:18 -0700]:
> On Wed, Jun 17, 2020 at 01:43:45PM -0700, Andrey Ignatov wrote:
> [ ... ]
> > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> > index e5c5305e859c..fa21b1e766ae 100644
> > --- a/kernel/bpf/btf.c
> > +++ b/kernel/bpf/btf.c
> > @@ -3577,6 +3577,67 @@ btf_get_prog_ctx_type(struct bpf_verifier_log *log, struct btf *btf,
> > return ctx_type;
> > }
> >
> > +#define BPF_PROG_TYPE(_id, _name, prog_ctx_type, kern_ctx_type)
> > +#define BPF_LINK_TYPE(_id, _name)
> > +static const struct bpf_map_ops * const btf_vmlinux_map_ops[] = {
> > +#define BPF_MAP_TYPE(_id, _ops) \
> > + [_id] = &_ops,
> > +#include <linux/bpf_types.h>
> > +#undef BPF_MAP_TYPE
> > +};
> > +static u32 btf_vmlinux_map_ids[] = {
> > +#define BPF_MAP_TYPE(_id, _ops) \
> > + [_id] = (u32)-1,
> > +#include <linux/bpf_types.h>
> > +#undef BPF_MAP_TYPE
> > +};
> > +#undef BPF_PROG_TYPE
> > +#undef BPF_LINK_TYPE
> > +
> > +static int btf_vmlinux_map_ids_init(const struct btf *btf,
> > + struct bpf_verifier_log *log)
> > +{
> > + int base_btf_id, btf_id, i;
> > + const char *btf_name;
> > +
> > + base_btf_id = btf_find_by_name_kind(btf, "bpf_map", BTF_KIND_STRUCT);
> > + if (base_btf_id < 0)
> > + return base_btf_id;
> > +
> > + BUILD_BUG_ON(ARRAY_SIZE(btf_vmlinux_map_ops) !=
> > + ARRAY_SIZE(btf_vmlinux_map_ids));
> > +
> > + for (i = 0; i < ARRAY_SIZE(btf_vmlinux_map_ops); ++i) {
> > + if (!btf_vmlinux_map_ops[i])
> > + continue;
> > + btf_name = btf_vmlinux_map_ops[i]->map_btf_name;
> > + if (!btf_name) {
> > + btf_vmlinux_map_ids[i] = base_btf_id;
> > + continue;
> > + }
> > + btf_id = btf_find_by_name_kind(btf, btf_name, BTF_KIND_STRUCT);
> > + if (btf_id < 0)
> > + return btf_id;
> > + btf_vmlinux_map_ids[i] = btf_id;
> Since map_btf_name is already in map_ops, how about storing map_btf_id in
> map_ops also?
> btf_id 0 is "void" which is as good as -1, so there is no need
> to modify all map_ops to init map_btf_id to -1.
Yeah, btf_id == 0 being a valid id was the reason I used -1.
I realized that having a map type specific struct with btf_id == 0
should be practically impossible, but is it guaranteed to always be
"void" or it just happened so and can change in the future?
If both this and having one more field in bpf_map_ops is not a problem,
I'll move it to bpf_map_ops.
--
Andrey Ignatov
