Re: [RESEND] BTF is not generated for gcc-built kernel with the latest pahole

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

Em Thu, Jul 27, 2023 at 09:38:14AM +0900, Masami Hiramatsu escreveu:
> On Wed, 26 Jul 2023 15:46:03 +0100
> Alan Maguire <alan.maguire@oracle.com> wrote:
> 
> > On 26/07/2023 12:07, Masami Hiramatsu (Google) wrote:
> > > Hi Jiri,
> > > 
> > > On Wed, 26 Jul 2023 12:04:08 +0200
> > > Jiri Olsa <olsajiri@gmail.com> wrote:
> > > 
> > >> On Wed, Jul 26, 2023 at 10:25:34AM +0900, Masami Hiramatsu wrote:
> > >>> Hello,
> > >>> (I resend this because kconfig was too big)
> > >>>
> > >>> I found that BTF is not generated for gcc-built kernel with that latest
> > >>> pahole (v1.25).
> > >>
> > >> hi,
> > >> I can't reproduce on my setup with your .config
> > >>
> > >> does 'bpftool btf dump file ./vmlinux' show any error?
> > >>
> > >> is there any error in the kernel build output?
> > > 
> > > Yes, here it is. I saw these 2 lines.
> > > 
> > > die__process: DW_TAG_compile_unit, DW_TAG_type_unit, DW_TAG_partial_unit or DW_TAG_skeleton_unit expected got INVALID (0x0)!
> > > die__process: DW_TAG_compile_unit, DW_TAG_type_unit, DW_TAG_partial_unit or DW_TAG_skeleton_unit expected got INVALID (0x0)!
> > 
> > This is strange, looks like some CUs were encoded incorrectly or we are
> > parsing incorrectly. The error originates in die__process() and happens
> > if the dwarf_tag() associated with the DIE isn't an expected unit; it's
> > not even a valid tag value (0) it looks like. I've not built with gcc 13
> > yet so it's possible that's the reason you're seeing this, I'll try to
> > reproduce it..
> 
> And this warning message is not good for debugging. It would better dump
> the message with DIE index so that we can analyze the DWARF with other
> tools.

Good idea, I'll add that.
 
- Arnaldo