Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> writes: > On Tue, Mar 3, 2020 at 3:01 PM Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote: >> >> On 3/3/20 1:32 AM, Andrii Nakryiko wrote: >> > Switch BPF UAPI constants, previously defined as #define macro, to anonymous >> > enum values. This preserves constants values and behavior in expressions, but >> > has added advantaged of being captured as part of DWARF and, subsequently, BTF >> > type info. Which, in turn, greatly improves usefulness of generated vmlinux.h >> > for BPF applications, as it will not require BPF users to copy/paste various >> > flags and constants, which are frequently used with BPF helpers. Only those >> > constants that are used/useful from BPF program side are converted. >> > >> > Signed-off-by: Andrii Nakryiko <andriin@xxxxxx> >> >> Just thinking out loud, is there some way this could be resolved generically >> either from compiler side or via additional tooling where this ends up as BTF >> data and thus inside vmlinux.h as anon enum eventually? bpf.h is one single >> header and worst case libbpf could also ship a copy of it (?), but what about >> all the other things one would need to redefine e.g. for tracing? Small example >> that comes to mind are all these TASK_* defines in sched.h etc, and there's >> probably dozens of other similar stuff needed too depending on the particular >> case; would be nice to have some generic catch-all, hmm. > > Enum convertion seems to be the simplest and cleanest way, > unfortunately (as far as I know). DWARF has some extensions capturing > #defines, but values are strings (and need to be parsed, which is pain > already for "1 << 1ULL"), and it's some obscure extension, not a > standard thing. I agree would be nice not to have and change all UAPI > headers for this, but I'm not aware of the solution like that. Since this is a UAPI header, are we sure that no userspace programs are using these defines in #ifdefs or something like that? -Toke
