On Thu, Jun 18, 2020 at 5:56 PM Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> wrote: > > On Tue, Jun 16, 2020 at 3:05 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote: > > > > Adding support to generate .BTF_ids section that would > > hold various BTF IDs list for verifier. > > > > Adding macros help to define lists of BTF IDs placed in > > .BTF_ids section. They are initially filled with zeros > > (during compilation) and resolved later during the > > linking phase by btfid tool. > > > > Following defines list of one BTF ID that is accessible > > within kernel code as bpf_skb_output_btf_ids array. > > > > extern int bpf_skb_output_btf_ids[]; > > > > BTF_ID_LIST(bpf_skb_output_btf_ids) > > BTF_ID(struct, sk_buff) > > > > Suggested-by: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> > > Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx> > > --- > > include/asm-generic/vmlinux.lds.h | 4 ++ > > kernel/bpf/Makefile | 2 +- > > kernel/bpf/btf_ids.c | 3 ++ > > kernel/bpf/btf_ids.h | 70 +++++++++++++++++++++++++++++++ > > 4 files changed, 78 insertions(+), 1 deletion(-) > > create mode 100644 kernel/bpf/btf_ids.c > > create mode 100644 kernel/bpf/btf_ids.h > > > > [...] > > > +/* > > + * Following macros help to define lists of BTF IDs placed > > + * in .BTF_ids section. They are initially filled with zeros > > + * (during compilation) and resolved later during the > > + * linking phase by btfid tool. > > + * > > + * Any change in list layout must be reflected in btfid > > + * tool logic. > > + */ > > + > > +#define SECTION ".BTF_ids" > > nit: SECTION is super generic and non-greppable. BTF_IDS_SECTION? > > > + > > +#define ____BTF_ID(symbol) \ > > +asm( \ > > +".pushsection " SECTION ",\"a\"; \n" \ > > section should be also read-only? Either immediately here, of btfid > tool should mark it? Unless I missed that it's already doing it :) > > > +".local " #symbol " ; \n" \ > > +".type " #symbol ", @object; \n" \ > > +".size " #symbol ", 4; \n" \ > > +#symbol ": \n" \ > > +".zero 4 \n" \ > > +".popsection; \n"); > > + > > +#define __BTF_ID(...) \ > > + ____BTF_ID(__VA_ARGS__) > > why varargs, if it's always a single argument? Or it's one of those > macro black magic things were it works only in this particular case, > but not others? > > > > + > > +#define __ID(prefix) \ > > + __PASTE(prefix, __COUNTER__) > > + > > + > > +/* > > + * The BTF_ID defines unique symbol for each ID pointing > > + * to 4 zero bytes. > > + */ > > +#define BTF_ID(prefix, name) \ > > + __BTF_ID(__ID(__BTF_ID__##prefix##__##name##__)) > > + > > + > > +/* > > + * The BTF_ID_LIST macro defines pure (unsorted) list > > + * of BTF IDs, with following layout: > > + * > > + * BTF_ID_LIST(list1) > > + * BTF_ID(type1, name1) > > + * BTF_ID(type2, name2) > > + * > > + * list1: > > + * __BTF_ID__type1__name1__1: > > + * .zero 4 > > + * __BTF_ID__type2__name2__2: > > + * .zero 4 > > + * > > + */ > > +#define BTF_ID_LIST(name) \ > > nit: btw, you call it a list here, but btfids tool talks about > "sorts". Maybe stick to consistent naming. Either "list" or "set" > seems to be appropriate. Set implies a sorted aspect a bit more, IMO. > > > +asm( \ > > +".pushsection " SECTION ",\"a\"; \n" \ > > +".global " #name "; \n" \ > > I was expecting to see reserved 4 bytes for list size? I also couldn't > find where btfids tool prepends it. From what I could understand, it > just assumed the first 4 bytes are the length prefix? Sorry if I'm > slow... Never mind, this is different from whitelisting you do in patch #8. But now I'm curious how this list symbol gets its size correctly calculated?.. > > > > +#name ":; \n" \ > > +".popsection; \n"); > > + > > +#endif > > -- > > 2.25.4 > >
