On Tue, 19 Jul 2022 at 20:37, Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote: > > On Tue, Jul 19, 2022 at 03:24:18PM +0200, Kumar Kartikeya Dwivedi wrote: > > > > +#define ____BTF_ID_FLAGS_LIST(_0, _1, _2, _3, _4, _5, N, ...) _1##_##_2##_##_3##_##_4##_##_5##__ > > +#define __BTF_ID_FLAGS_LIST(...) ____BTF_ID_FLAGS_LIST(0x0, ##__VA_ARGS__, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0) > > + > > +#define __FLAGS(prefix, ...) \ > > + __PASTE(prefix, __BTF_ID_FLAGS_LIST(__VA_ARGS__)) > > + > > +#define BTF_ID_FLAGS(prefix, name, ...) \ > > + BTF_ID(prefix, name) \ > > + __BTF_ID(__ID(__FLAGS(__BTF_ID__flags__, ##__VA_ARGS__))) > > + > > /* > > * The BTF_ID_LIST macro defines pure (unsorted) list > > * of BTF IDs, with following layout: > > @@ -145,10 +164,53 @@ asm( \ > > ".popsection; \n"); \ > > extern struct btf_id_set name; > > > > +/* > > + * The BTF_SET8_START/END macros pair defines sorted list of > > + * BTF IDs and their flags plus its members count, with the > > + * following layout: > > + * > > + * BTF_SET8_START(list) > > + * BTF_ID_FLAGS(type1, name1, flags...) > > + * BTF_ID_FLAGS(type2, name2, flags...) > > + * BTF_SET8_END(list) > > + * > > + * __BTF_ID__set8__list: > > + * .zero 8 > > + * list: > > + * __BTF_ID__type1__name1__3: > > + * .zero 4 > > + * __BTF_ID__flags__0x0_0x0_0x0_0x0_0x0__4: > > + * .zero 4 > > Overall looks great, > but why encode flags into a name? > Why reuse ____BTF_ID for flags and complicate resolve_btfid? > Instead of .zero 4 insert the actual flags as .word ? > > The usage will be slightly different. > Instead of: > BTF_ID_FLAGS(func, bpf_get_task_pid, KF_ACQUIRE, KF_RET_NULL) > it will be > BTF_ID_FLAGS(func, bpf_get_task_pid, KF_ACQUIRE | KF_RET_NULL) Nice, I didn't know you could do complex expressions like this for asm directives like .word, but it makes sense now. TIL. I'm not very well versed with GNU as. I will rework this and drop the resolve_btfids changes for flags. Thanks a lot!
