Re: [PATCH dwarves v2 0/4] btf: support btf_type_tag attribute

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

Em Tue, Nov 23, 2021 at 10:32:18AM -0800, Andrii Nakryiko escreveu:
> On Mon, Nov 22, 2021 at 8:56 PM Yonghong Song <yhs@fb.com> wrote:
> >
> > btf_type_tag is a new llvm type attribute which is used similar
> > to kernel __user/__rcu attributes. The format of btf_type_tag looks like
> >   __attribute__((btf_type_tag("tag1")))
> > For the case where the attribute applied to a pointee like
> >   #define __tag1 __attribute__((btf_type_tag("tag1")))
> >   #define __tag2 __attribute__((btf_type_tag("tag2")))
> >   int __tag1 * __tag1 __tag2 *g;
> > the information will be encoded in dwarf.
> >
> > In BTF, the attribute is encoded as a new kind
> > BTF_KIND_TYPE_TAG and latest bpf-next supports it.
> >
> > The patch added support in pahole, specifically
> > converts llvm dwarf btf_type_tag attributes to
> > BTF types. Please see individual patches for details.
> >
> > Changelog:
> >   v1 -> v2:
> >      - reorg an if condition to reduce nesting level.
> >      - add more comments to explain how to chain type tag types.
> >
> > Yonghong Song (4):
> >   libbpf: sync with latest libbpf repo
> >   dutil: move DW_TAG_LLVM_annotation definition to dutil.h
> >   dwarf_loader: support btf_type_tag attribute
> >   btf_encoder: support btf_type_tag attribute
> >
> 
> I thought that v1 was already applied, but either way LGTM. I'm not

To the next branch, and the libbpf pahole CI is failing, since a few
days, can you please take a look?

> super familiar with the DWARF loader parts, so I mostly just read it
> very superficially :)

I replaced the patches that changed, re-added the S-o-B for Yonghong and
tested it with llvm-project HEAD.

> Acked-by: Andrii Nakryiko <andrii@kernel.org>

Adding it to the csets.

Thanks!

- Arnaldo
 
> 
> >  btf_encoder.c  |   7 +++
> >  dutil.h        |   4 ++
> >  dwarf_loader.c | 140 ++++++++++++++++++++++++++++++++++++++++++++++---
> >  dwarves.h      |  38 +++++++++++++-
> >  lib/bpf        |   2 +-
> >  pahole.c       |   8 +++
> >  6 files changed, 190 insertions(+), 9 deletions(-)
> >
> > --
> > 2.30.2
> >

-- 

- Arnaldo