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SubjectRe: [PATCH] kbuild: reuse vmlinux.o in vmlinux_link
On Fri, May 22, 2020 at 5:27 AM Sami Tolvanen <samitolvanen@google.com> wrote:
>
> Instead of linking all compilation units again each time vmlinux_link is
> called, reuse vmlinux.o from modpost_link.
>
> With x86_64 allyesconfig, vmlinux_link is called three times and reusing
> vmlinux.o reduces the build time ~38 seconds on my system (59% reduction
> in the time spent in vmlinux_link).
>
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> ---
> scripts/link-vmlinux.sh | 5 +----
> 1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> index d09ab4afbda4..c6cc4305950c 100755
> --- a/scripts/link-vmlinux.sh
> +++ b/scripts/link-vmlinux.sh
> @@ -77,11 +77,8 @@ vmlinux_link()
>
> if [ "${SRCARCH}" != "um" ]; then
> objects="--whole-archive \
> - ${KBUILD_VMLINUX_OBJS} \
> + vmlinux.o \
> --no-whole-archive \
> - --start-group \
> - ${KBUILD_VMLINUX_LIBS} \
> - --end-group \
> ${@}"
>
> ${LD} ${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux} \
>
> base-commit: b85051e755b0e9d6dd8f17ef1da083851b83287d
> --
> 2.27.0.rc0.183.gde8f92d652-goog
>


I like this patch irrespective of CLANG_LTO, but
unfortunately, my build test failed.


ARCH=powerpc failed to build as follows:



MODPOST vmlinux.o
MODINFO modules.builtin.modinfo
GEN modules.builtin
LD .tmp_vmlinux.kallsyms1
vmlinux.o:(__ftr_alt_97+0x20): relocation truncated to fit:
R_PPC64_REL14 against `.text'+4b1c
vmlinux.o:(__ftr_alt_97+0x164): relocation truncated to fit:
R_PPC64_REL14 against `.text'+1cf78
vmlinux.o:(__ftr_alt_97+0x288): relocation truncated to fit:
R_PPC64_REL14 against `.text'+1dac4
vmlinux.o:(__ftr_alt_97+0x2f0): relocation truncated to fit:
R_PPC64_REL14 against `.text'+1e254
make: *** [Makefile:1125: vmlinux] Error 1



I used powerpc-linux-gcc
available at
https://mirrors.edge.kernel.org/pub/tools/crosstool/files/bin/x86_64/9.2.0/


Build command:

make -j24 ARCH=powerpc CROSS_COMPILE=powerpc-linux- defconfig all


Could you check it please?



I will apply it to my test branch.
Perhaps, 0-day bot may find more failure cases.


--
Best Regards
Masahiro Yamada

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