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

Nicolas Schier
2025-09-18T04:09:11Z

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