Re: [PATCH v5 11/17] kbuild: Add generic hook for architectures to use before the final vmlinux link

[Masahiro Yamada]

On Mon, Sep 16, 2024 at 5:58 AM Hari Bathini <hbathini@xxxxxxxxxxxxx> wrote:
>
> From: Naveen N Rao <naveen@xxxxxxxxxx>
>
> 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 Makefile.vmlinux that architectures can use for this purpose.
>
> Architectures need to select CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX and must
> provide arch/<arch>/tools/Makefile with .arch.vmlinux.o target, which
> will be invoked prior to the final vmlinux link step.
>
> Signed-off-by: Naveen N Rao <naveen@xxxxxxxxxx>
> Signed-off-by: Hari Bathini <hbathini@xxxxxxxxxxxxx>
> ---
>
> Changes in v5:
> * Intermediate files named .vmlinux.arch.* instead of .arch.vmlinux.*
>
>
>  arch/Kconfig             | 6 ++++++
>  scripts/Makefile.vmlinux | 7 +++++++
>  scripts/link-vmlinux.sh  | 7 ++++++-
>  3 files changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/arch/Kconfig b/arch/Kconfig
> index 975dd22a2dbd..ef868ff8156a 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -1643,4 +1643,10 @@ config CC_HAS_SANE_FUNCTION_ALIGNMENT
>  config ARCH_NEED_CMPXCHG_1_EMU
>         bool
>
> +config ARCH_WANTS_PRE_LINK_VMLINUX
> +       def_bool n


Redundant default. This line should be "bool".






> +       help
> +         An architecture can select this if it provides arch/<arch>/tools/Makefile
> +         with .arch.vmlinux.o target to be linked into vmlinux.
> +
>  endmenu
> diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux
> index 49946cb96844..edf6fae8d960 100644
> --- a/scripts/Makefile.vmlinux
> +++ b/scripts/Makefile.vmlinux
> @@ -22,6 +22,13 @@ targets += .vmlinux.export.o
>  vmlinux: .vmlinux.export.o
>  endif
>
> +ifdef CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX
> +vmlinux: arch/$(SRCARCH)/tools/.vmlinux.arch.o

If you move this to arch/*/tools/, there is no reason
to make it a hidden file.


vmlinux: arch/$(SRCARCH)/tools/vmlinux.arch.o




> +arch/$(SRCARCH)/tools/.vmlinux.arch.o: vmlinux.o

FORCE is missing.


arch/$(SRCARCH)/tools/vmlinux.arch.o: vmlinux.o FORCE



> +       $(Q)$(MAKE) $(build)=arch/$(SRCARCH)/tools $@
> +endif
> +
>  ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)
>
>  # Final link of vmlinux with optional arch pass after final link
> diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> index f7b2503cdba9..b3a940c0e6c2 100755
> --- a/scripts/link-vmlinux.sh
> +++ b/scripts/link-vmlinux.sh
> @@ -100,7 +100,7 @@ vmlinux_link()
>         ${ld} ${ldflags} -o ${output}                                   \
>                 ${wl}--whole-archive ${objs} ${wl}--no-whole-archive    \
>                 ${wl}--start-group ${libs} ${wl}--end-group             \
> -               ${kallsymso} ${btf_vmlinux_bin_o} ${ldlibs}
> +               ${kallsymso} ${btf_vmlinux_bin_o} ${arch_vmlinux_o} ${ldlibs}
>  }
>
>  # generate .BTF typeinfo from DWARF debuginfo
> @@ -214,6 +214,11 @@ fi
>
>  ${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init init/version-timestamp.o
>
> +arch_vmlinux_o=""
> +if is_enabled CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX; then
> +       arch_vmlinux_o=arch/${SRCARCH}/tools/.vmlinux.arch.o


arch_vmlinux_o=arch/${SRCARCH}/tools/vmlinux.arch.o



> +fi
> +
>  btf_vmlinux_bin_o=
>  kallsymso=
>  strip_debug=
> --
> 2.46.0
>


--
Best Regards
Masahiro Yamada