Re: [PATCH dwarves 0/4] BTF ELF writing changes

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Wed, Jan 27, 2021 at 01:10:40AM +0000, Giuliano Procida escreveu:
> Hi.
> 
> On Tue, 26 Jan 2021 at 19:56, Jiri Olsa <jolsa@redhat.com> wrote:
> >
> > On Mon, Jan 25, 2021 at 01:06:21PM +0000, Giuliano Procida wrote:
> > > Hi.
> > >
> > > This follows on from my change to improve the error handling around
> > > llvm-objcopy in libbtf.c.
> > >
> > > Note on recipients: Please let me know if I should adjust To or CC.
> > >
> > > Note on style: I've generally placed declarations as allowed by C99,
> > > closest to point of use. Let me know if you'd prefer otherwise.
> > >
> > > 1. Improve ELF error reporting
> > >
> > > 2. Add .BTF section using libelf
> > >
> > > This shows the minimal amount of code needed to drive libelf. However,
> > > it leaves layout up to libelf, which is almost certainly not wanted.
> > >
> > > As an unexpcted side-effect, vmlinux is larger than before. It seems
> > > llvm-objcopy likes to trim down .strtab.
> > >
> > > 3. Manually lay out updated ELF sections
> > >
> > > This does full layout of new and updated ELF sections. If the update
> > > ELF sections were not the last ones in the file by offset, then it can
> > > leave gaps between sections.
> > >
> > > 4. Align .BTF section to 8 bytes
> > >
> > > This was my original aim.
> > >
> > > Regards.
> > >
> > > Giuliano Procida (4):
> > >   btf_encoder: Improve ELF error reporting
> > >   btf_encoder: Add .BTF section using libelf
> > >   btf_encoder: Manually lay out updated ELF sections
> > >   btf_encoder: Align .BTF section to 8 bytes
> >
> > hi,
> > I can't apply this on dwarves git master, which commit is it based on?
> >
> 
> It's based on:
> https://www.spinics.net/lists/dwarves/msg00775.html (0/3)
> https://www.spinics.net/lists/dwarves/msg00774.html (1/3, unrelated fix)
> https://www.spinics.net/lists/dwarves/msg00773.html (2/3, this is the
> one you'll need for a clean git am; obsoleted by this new series)
> (3/3 was abandoned)
> 
> Arnaldo did say the two commits were applied... but perhaps they
> haven't been pushed to public master yet.

I pushed what I have now, please check if anything is missing.

I'm now working on DWARF4's DW_AT_data_bit_offset, that gcc uses when
dwarf-5 is asked for, I should have something usable tomorrow and
hopefully this will be the last stuff to get into 1.20.

dd

thanks,

- Arnaldo
 
> > thanks,
> > jirka
> >
> 
> You're welcome.
> Giuliano.
> 
> > >
> > >  libbtf.c | 222 +++++++++++++++++++++++++++++++++++++++++++------------
> > >  1 file changed, 175 insertions(+), 47 deletions(-)
> > >
> > > --
> > > 2.30.0.280.ga3ce27912f-goog
> > >
> >

-- 

- Arnaldo