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

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Message-ID: <aMqhuFQGAGtYFbRV@levanger>
Date: Wed, 17 Sep 2025 13:55:36 +0200
From: Nicolas Schier <nsc@...nel.org>
To: Alexey Gladkov <legion@...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 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.

  * 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.

Kind regards,
Nicolas