On Wed, Apr 24, 2024 at 2:30 PM Jose E. Marchesi
<jose.marchesi@xxxxxxxxxx> wrote:
>
>
> Hi Yonghong.
>
> > On 4/24/24 1:41 AM, Jose E. Marchesi wrote:
> >> This little patch modifies selftests/bpf/Makefile so it passes the
> >> following extra options when invoking gcc-bpf:
> >>
> >> -gbtf
> >> This makes GCC to emit BTF debug info in .BTF and .BTF.ext.
> >
> > Could we do if '-g' is specified, for bpf program,
> > btf will be automatically generated?
>
> Hmm, in principle I wouldn't oppose for -g to mean -gbtf instead of
> -gdwarf. DWARF can always be generated by using -gdwarf.
>
> Faust, Indu, WDYT?
>
> >>
> >> -mco-re
> >> This tells GCC to generate CO-RE relocations in .BTF.ext.
> >
> > Can we make this default? That is, remove -mco-re option. I
> > can imagine for any serious bpf program, co-re is a must.
>
> CO-RE depends on BTF. So I understand the above as making -mco-re the
> default if BTF is generated, i.e. if -gbtf (or -g with the modification
> above) are specified. Isn't that what clang does? Am I interpreting
> correctly?
>
> >>
> >> -masm=pseudoc
> >> This tells GCC to emit BPF assembler using the pseudo-c syntax.
> >
> > Can we make it the other way round such that -masm=pseudoc is
> > the default? You can have an option e.g., -masm=non-pseudoc,
> > for the other format?
>
> We could add a configure-time build option:
>
> --with-bpf-default-asm-syntax={pseudoc,normal}
>
> so that GCC can be built to use whatever selected syntax as default.
> Distros and people can then decide what to do.
distros just ship stuff.
It's our job to pick good defaults.
I agree with Yonghong that -g should imply -gbtf for bpf target
and -mco-re doesn't need to be a flag at all.
Compiler should do it when it sees those special attributes in C code.
-masm=pseudoc is a good default as well, since that's what
everyone in bpf community is used to.
