linux-kernel - Re: [PATCH v7 3/8] kbuild: keep .modinfo section in vmlinux.unstripped

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Message-ID: <aMqrrjXZxYXN0zdY@example.org>
Date: Wed, 17 Sep 2025 14:38:06 +0200
From: Alexey Gladkov <legion@...nel.org>
To: Nicolas Schier <nsc@...nel.org>
Cc: Nathan Chancellor <nathan@...nel.org>, Petr Pavlu <petr.pavlu@...e.com>,
	Luis Chamberlain <mcgrof@...nel.org>,
	Sami Tolvanen <samitolvanen@...gle.com>,
	Daniel Gomez <da.gomez@...sung.com>, linux-kernel@...r.kernel.org,
	linux-modules@...r.kernel.org, linux-kbuild@...r.kernel.org,
	Masahiro Yamada <masahiroy@...nel.org>
Subject: Re: [PATCH v7 3/8] kbuild: keep .modinfo section in
 vmlinux.unstripped

On Wed, Sep 17, 2025 at 01:55:36PM +0200, Nicolas Schier wrote:
> On Tue, Sep 16, 2025 at 02:42:48PM +0200, Nicolas Schier wrote:
> > On Tue, Sep 16, 2025 at 01:30:20PM +0200, Alexey Gladkov wrote:
> ...
> > > I think in the case of .modinfo, we can change the flag in the section
> > > since we are going to delete it anyway.
> > > 
> > > diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux
> > > index dbbe3bf0cf23..9a118b31d0dc 100644
> > > --- a/scripts/Makefile.vmlinux
> > > +++ b/scripts/Makefile.vmlinux
> > > @@ -87,7 +87,8 @@ remove-section-$(CONFIG_ARCH_VMLINUX_NEEDS_RELOCS) += '.rel*'
> > >  remove-symbols := -w --strip-symbol='__mod_device_table__*'
> > >  
> > >  quiet_cmd_strip_relocs = OBJCOPY $@
> > > -      cmd_strip_relocs = $(OBJCOPY) $(addprefix --remove-section=,$(remove-section-y)) \
> > > +      cmd_strip_relocs = $(OBJCOPY) $(patsubst %,--set-section-flags %=noload,$(remove-section-y)) $< && \
> > > +                         $(OBJCOPY) $(addprefix --remove-section=,$(remove-section-y)) \
> > >                           $(remove-symbols) $< $@
> > >  
> > >  targets += vmlinux
> > 
> > Ah, great!  I thought we had to fiddle around with linker scripts et al.
> > I needed to use an intermediate file:
> > 
> > diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux
> > index e2ceeb9e168d..516d51ca634b 100644
> > --- a/scripts/Makefile.vmlinux
> > +++ b/scripts/Makefile.vmlinux
> > @@ -90,6 +90,9 @@ remove-section-y                                   := .modinfo
> >  remove-section-$(CONFIG_ARCH_VMLINUX_NEEDS_RELOCS) += '.rel*'
> >  
> >  quiet_cmd_strip_relocs = OBJCOPY $@
> > -      cmd_strip_relocs = $(OBJCOPY) $(addprefix --remove-section=,$(remove-section-y)) $< $@
> > +      cmd_strip_relocs = set -e; \
> > +                        trap 'rm $<.noload' EXIT HUP INT; \
> > +                        $(OBJCOPY) $(patsubst %,--set-section-flags %=noload,$(remove-section-y)) $< $<.noload && \
> > +                        $(OBJCOPY) $(addprefix --remove-section=,$(remove-section-y)) $<.noload $@
> >  
> >  targets += vmlinux
> 
> I'd like to suggest another version closer to yours, as mine has several flaws:
> 
> diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux
> index dbbe3bf0cf23..9a118b31d0dc 100644
> --- a/scripts/Makefile.vmlinux
> +++ b/scripts/Makefile.vmlinux
> @@ -87,7 +87,8 @@ remove-section-$(CONFIG_ARCH_VMLINUX_NEEDS_RELOCS) += '.rel*'
>  remove-symbols := -w --strip-symbol='__mod_device_table__*'
>  
>  quiet_cmd_strip_relocs = OBJCOPY $@
> -      cmd_strip_relocs = $(OBJCOPY) $(addprefix --remove-section=,$(remove-section-y)) \
> +      cmd_strip_relocs = $(OBJCOPY) $(patsubst %,--set-section-flags %=noload,$(remove-section-y)) $< $@; \
> +                         $(OBJCOPY) $(addprefix --remove-section=,$(remove-section-y)) \
>                           $(remove-symbols) $@
>  
>  targets += vmlinux
> 
> 
> 
> Rationale (mainly for myself to not walk into that trap too often again):
> 
>   * Use ';' instead of '&&' as 'cmd_' is evaluated in a 'set -e'
>     environment ('cmd') and thus '&&' may hide a possible error exit
>     code.

No, it can't hide exit code. The exit code will be correct even if
‘set -e’ is not used.

$ (exit 0) && (exit 2) && (exit 3); echo $?
2

Actually ‘&&’ is protection against the absence of ‘set -e’.

>   * Create 'vmlinux' already with the first objcopy and let the second
>     one modify it in order to not need a temporary file; iff one or the
>     other objcopy exists with an error exit code, the 'set -e + trap'
>     ('delete-on-interrupt') shell will remove a possibly existing
>     vmlinux file.

That makes totally sense. This will avoid a temporary file. I will use it
in the new version.

-- 
Rgrds, legion