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

[Nicolas Schier <nsc@kernel.org>]

On Wed, Sep 17, 2025 at 02:38:06PM +0200, Alexey Gladkov wrote:
> 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’.

That is correct for such a simple command sequence.

Putting a compound 'command1 && command2' sequence in a cmd_* macro leads to a
mixture of non-comound and compound statements:

    ( set -e; (exit 0) && (exit 2) && (exit 3); printf 'bye\n' ); echo $?

thus we have a case as described in [1, "-e"], so that the exit code 2
gets lost due to the following successful 'printf'.

[1]: https://pubs.opengroup.org/onlinepubs/9799919799/utilities/V3_chap02.html#tag_19_26


> 
> >   * 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
> 

-- 
Nicolas