linux-kernel - Re: [PATCH 5.15 102/107] kbuild: Add skip_encoding_btf

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Message-ID: <YyRzpJ1dzAPpMBz7@krava>
Date:   Fri, 16 Sep 2022 15:01:24 +0200
From:   Jiri Olsa <olsajiri@...il.com>
To:     Thorsten Leemhuis <linux@...mhuis.info>
Cc:     Martin Rodriguez Reboredo <yakoyoku@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH 5.15 102/107] kbuild: Add skip_encoding_btf_enum64 option
 to pahole

On Fri, Sep 16, 2022 at 11:21:46AM +0100, Thorsten Leemhuis wrote:
> On 06.09.22 14:31, Greg Kroah-Hartman wrote:
> > From: Martin Rodriguez Reboredo <yakoyoku@...il.com>
> > 
> > New pahole (version 1.24) generates by default new BTF_KIND_ENUM64 BTF tag,
> > which is not supported by stable kernel.
> 
> Martin, when you wrote "not supported by stable kernel", did you mean
> just 5.15.y or 5.19.y as well? Because I ran into...
> 
> > As a result the kernel with CONFIG_DEBUG_INFO_BTF option will fail to
> > compile with following error:
> > 
> >   BTFIDS  vmlinux
> > FAILED: load BTF from vmlinux: Invalid argument
> 
> ...this compile error when compiling 5.19.9 for F37 and from a quick
> look into this it seems this was caused by a update of dwarves to 1.24
> that recently landed in that distribution. This patch seems to fix the
> problem (it got past the point of the error, but modules are still
> compiling).

hi,
IIUC Martin planned to send that for 5.19, I can do that if needed

jirka

> 
> Ciao, Thorsten
> 
> > New pahole provides --skip_encoding_btf_enum64 option to skip BTF_KIND_ENUM64
> > generation and produce BTF supported by stable kernel.
> > 
> > Adding this option to scripts/pahole-flags.sh.
> > 
> > This change does not have equivalent commit in linus tree, because linus tree
> > has support for BTF_KIND_ENUM64 tag, so it does not need to be disabled.
> > 
> > Signed-off-by: Martin Rodriguez Reboredo <yakoyoku@...il.com>
> > Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > ---
> >  scripts/pahole-flags.sh |    4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > --- a/scripts/pahole-flags.sh
> > +++ b/scripts/pahole-flags.sh
> > @@ -17,4 +17,8 @@ if [ "${pahole_ver}" -ge "121" ]; then
> >  	extra_paholeopt="${extra_paholeopt} --btf_gen_floats"
> >  fi
> >  
> > +if [ "${pahole_ver}" -ge "124" ]; then
> > +	extra_paholeopt="${extra_paholeopt} --skip_encoding_btf_enum64"
> > +fi
> > +
> >  echo ${extra_paholeopt}
> > 
> >