[RFC PATCH v2 4/5] kbuild: Add generic hook for architectures to use before the final vmlinux link

[Masahiro Yamada]

On Tue, Jun 11, 2024 at 2:20 AM Naveen N Rao <naveen at kernel.org> wrote:
>
> On Mon, Jun 10, 2024 at 06:14:51PM GMT, Masahiro Yamada wrote:
> > On Mon, Jun 10, 2024 at 5:39 PM Naveen N Rao <naveen at kernel.org> wrote:
> > >
> > > On powerpc, we would like to be able to make a pass on vmlinux.o and
> > > generate a new object file to be linked into vmlinux. Add a generic pass
> > > in link-vmlinux.sh that architectures can use for this purpose.
> > > Architectures need to select CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX and must
> > > provide arch/<arch>/tools/vmlinux_o.sh, which will be invoked prior to
> > > the final vmlinux link step.
> > >
> > > Signed-off-by: Naveen N Rao <naveen at kernel.org>
> > > ---
> > >  arch/Kconfig            |  3 +++
> > >  scripts/link-vmlinux.sh | 18 +++++++++++++++---
> > >  2 files changed, 18 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/arch/Kconfig b/arch/Kconfig
> > > index 975dd22a2dbd..649f0903e7ef 100644
> > > --- a/arch/Kconfig
> > > +++ b/arch/Kconfig
> > > @@ -1643,4 +1643,7 @@ config CC_HAS_SANE_FUNCTION_ALIGNMENT
> > >  config ARCH_NEED_CMPXCHG_1_EMU
> > >         bool
> > >
> > > +config ARCH_WANTS_PRE_LINK_VMLINUX
> > > +       def_bool n
> > > +
> > >  endmenu
> > > diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> > > index 46ce5d04dbeb..07f70e105d82 100755
> > > --- a/scripts/link-vmlinux.sh
> > > +++ b/scripts/link-vmlinux.sh
> ...
> > >
> > > +arch_vmlinux_o=""
> > > +if is_enabled CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX; then
> > > +       arch_vmlinux_o=.arch.vmlinux.o
> > > +       info "ARCH" ${arch_vmlinux_o}
> > > +       if ! ${srctree}/arch/${SRCARCH}/tools/vmlinux_o.sh ${arch_vmlinux_o} ; then
> > > +               echo >&2 "Failed to generate ${arch_vmlinux_o}"
> > > +               echo >&2 "Try to disable CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX"
> > > +               exit 1
> > > +       fi
> > > +fi
> >
> >
> >
> > This is wrong because scripts/link-vmlinux.sh is not triggered
> > even when source files under arch/powerpc/tools/ are changed.
> >
> > Presumably, scripts/Makefile.vmlinux will be the right place.
>
> Ah, yes. Something like this?
>
> diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux
> index 49946cb96844..77d90b6ac53e 100644
> --- a/scripts/Makefile.vmlinux
> +++ b/scripts/Makefile.vmlinux
> @@ -22,6 +22,10 @@ targets += .vmlinux.export.o
>  vmlinux: .vmlinux.export.o
>  endif
>
> +ifdef CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX
> +vmlinux: $(srctree)/arch/$(SRCARCH)/tools/vmlinux_o.sh
> +endif
> +
>  ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)
>
>  # Final link of vmlinux with optional arch pass after final link
>
>
> Thanks,
> Naveen
>



No.

Something like below.

Then, you can do everything in Makefile, not a shell script.



ifdef CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX
vmlinux: .arch.vmlinux.o

.arch.vmlinux.o: FORCE
        $(Q)$(MAKE) $(build)=arch/$(SRCARCH)/tools .arch.vmlinux.o

endif



I did not test it, though.








-- 
Best Regards
Masahiro Yamada