linux-kernel - Re: [PATCH v5 03/10] kbuild: keep .modinfo section in vmlinux.unstripped

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Message-ID: <CAK7LNARQvydrykp=4tf3w4aymTt-pBYnVnekWsOrVjHbTj3x8w@mail.gmail.com>
Date: Tue, 29 Jul 2025 22:54:51 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Alexander Gordeev <agordeev@...ux.ibm.com>
Cc: Alexey Gladkov <legion@...nel.org>, Petr Pavlu <petr.pavlu@...e.com>, 
	Luis Chamberlain <mcgrof@...nel.org>, Sami Tolvanen <samitolvanen@...gle.com>, 
	Daniel Gomez <da.gomez@...sung.com>, Nathan Chancellor <nathan@...nel.org>, 
	Nicolas Schier <nicolas.schier@...ux.dev>, linux-kernel@...r.kernel.org, 
	linux-modules@...r.kernel.org, linux-kbuild@...r.kernel.org
Subject: Re: [PATCH v5 03/10] kbuild: keep .modinfo section in vmlinux.unstripped

On Mon, Jul 28, 2025 at 10:58 PM Alexander Gordeev
<agordeev@...ux.ibm.com> wrote:
>
> On Thu, Jul 24, 2025 at 03:49:40PM +0200, Alexey Gladkov wrote:
>
> Hi Alexey, Masahiro,
>
> > From: Masahiro Yamada <masahiroy@...nel.org>
> >
> > Keep the .modinfo section during linking, but strip it from the final
> > vmlinux.
> >
> > Adjust scripts/mksysmap to exclude modinfo symbols from kallsyms.
> >
> > This change will allow the next commit to extract the .modinfo section
> > from the vmlinux.unstripped intermediate.
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> > ---
> >  include/asm-generic/vmlinux.lds.h | 2 +-
> >  scripts/Makefile.vmlinux          | 2 +-
> >  scripts/mksysmap                  | 3 +++
> >  3 files changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> > index fa5f19b8d53a..1791665006f9 100644
> > --- a/include/asm-generic/vmlinux.lds.h
> > +++ b/include/asm-generic/vmlinux.lds.h
> > @@ -831,6 +831,7 @@ defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG)
> >
> >  /* Required sections not related to debugging. */
> >  #define ELF_DETAILS                                                  \
> > +             .modinfo : { *(.modinfo) }                              \
>
> FWIW, to me .modinfo logically does not quite belong to ELF_DETAILS,
> since it is not about ELF.
>
> I would guess, that you want to make a minimal code impact to the
> linker scripts, but with that you turn .modinfo the only section
> among ones that do not make it to the final image:
>
>         STABS_DEBUG
>         DWARF_DEBUG
>         ELF_DETAILS
>
> That immediately breaks s390, but also is a call for trouble in
> the future, as far as I am concerned.
>
> Would it makes sense to introduce e.g MODINFO instead?

I am open to MODINFO addition, if Alexey is happy about
modifying linker scripts for all arches.
Yeah, it is tedious, though...




>
> >               .comment 0 : { *(.comment) }                            \
> >               .symtab 0 : { *(.symtab) }                              \
> >               .strtab 0 : { *(.strtab) }                              \
> > @@ -1044,7 +1045,6 @@ defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG)
> >       *(.discard.*)                                                   \
> >       *(.export_symbol)                                               \
> >       *(.no_trim_symbol)                                              \
> > -     *(.modinfo)                                                     \
> >       /* ld.bfd warns about .gnu.version* even when not emitted */    \
> >       *(.gnu.version*)                                                \
>
> Thanks!



-- 
Best Regards
Masahiro Yamada