Re: [RFT] pahole 1.20 RC was Re: [PATCH] btf_encoder: Add extra checks for symbol names

[Sedat Dilek <sedat.dilek@gmail.com>]

On Tue, Feb 2, 2021 at 8:48 AM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Thu, Jan 28, 2021 at 12:00 PM Arnaldo Carvalho de Melo
> <arnaldo.melo@gmail.com> wrote:
> >
> > Em Thu, Jan 21, 2021 at 08:11:17PM -0800, Andrii Nakryiko escreveu:
> > > On Thu, Jan 21, 2021 at 6:07 PM Sedat Dilek <sedat.dilek@gmail.com> wrote:
> > > > Do you want Nick's DWARF v5 patch-series as a base?
> >
> > > Arnaldo was going to figure out the DWARF v5 problem, so I'm leaving
> > > it up to him. I'm curious about DWARF v4 problems because no one yet
> > > reported that previously.
> >
> > I think I have the reported one fixed, Andrii, can you please do
> > whatever pre-release tests you can in your environment with what is in:
> >
>
> Hi Arnaldo,
>
> Sorry for the delay, just back from a short PTO.
>
> It all looks to be working fine on my side. There is a compilation
> error in our libbpf CI when building the latest pahole from sources
> due to DW_FORM_implicit_const being undefined. I'm updating our VMs to
> use Ubuntu Focal 20.04, up from Bionic 18.04, and that should
> hopefully solve the issue due to newer versions of libdw. If you worry
> about breaking others, though, we might want to add #ifndef guards and
> re-define DW_FORM_implicit_const as 0x21 explicitly in pahole source
> code.
>
> But otherwise, all good from what I can see in my environment. Looking
> forward to 1.20 release! I'll let you know if, after updating to
> Ubuntu Focal, any new pahole issues crop up.
>

Last weekend I did some testing with
<pahole.git#DW_AT_data_bit_offset> and DWARF-v5 support for the
Linux-kernel.

The good: I was able to compile :-).
The bad: My build-log grew up to 1.2GiB and I could not boot in QEMU.
The ugly: I killed the archive which had all relevant material.

Yesterday, I compiled latest pahole.git:

$ git describe
v1.19-25-g8d6f06f053a0

$ git log -1 --oneline
8d6f06f053a0 (HEAD -> master, origin/master, origin/HEAD)
dwarf_loader: Add conditional DW_FORM_implicit_const definition for
older system

I cannot promise to test it with Nick Desaulniers' DWARF-v5 patchset
but the recent DWARF changes within pahole.git look promising.

- Sedat -

>
> > https://git.kernel.org/pub/scm/devel/pahole/pahole.git/log/?h=DW_AT_data_bit_offset
> >
> > ?
> >
> > The cset has the tests I performed and the references to the bugzilla
> > ticket and Daniel has tested as well for his XDR + gcc 11 problem.
> >
> > Thanks,
> >
> > - Arnaldo