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Date: Sat, 23 May 2020 03:16:49 +0900 From: Masahiro Yamada <masahiroy@...nel.org> To: Kees Cook <keescook@...omium.org> Cc: Sami Tolvanen <samitolvanen@...gle.com>, Michal Marek <michal.lkml@...kovi.net>, Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: [PATCH] kbuild: reuse vmlinux.o in vmlinux_link On Fri, May 22, 2020 at 7:08 AM Kees Cook <keescook@...omium.org> wrote: > > On Thu, May 21, 2020 at 01:27:16PM -0700, Sami Tolvanen 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). > > Nice! Any time savings at final link is a big cumulative win. > > > Signed-off-by: Sami Tolvanen <samitolvanen@...gle.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} \ > > I think the "um" case can be updated as well too, yes? I agree. I changed the um part, then ARCH=um build is successful. > Also, I think the comment above modpost_link() needs to be updated now > to reflect the nature of how vmlinux.o gets used after this patch. > > -- > Kees Cook -- Best Regards Masahiro Yamada
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