linux-kernel - Re: [PATCH] x86: vdso: Use $LD instead of $CC to link

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Date:   Fri, 3 Aug 2018 10:29:04 -0700
From:   Alistair Strachan <astrachan@...gle.com>
To:     tglx@...utronix.de
Cc:     linux-kernel@...r.kernel.org, luto@...nel.org, mingo@...hat.com,
        hpa@...or.com, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        x86@...nel.org, kernel-team@...roid.com, joel@...lfernandes.com
Subject: Re: [PATCH] x86: vdso: Use $LD instead of $CC to link

On Fri, Aug 3, 2018 at 3:26 AM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> On Wed, 18 Jul 2018, Alistair Strachan wrote:
> >  export CPPFLAGS_vdso.lds += -P -C
> >
> > -VDSO_LDFLAGS_vdso.lds = -m64 -Wl,-soname=linux-vdso.so.1 \
> > -                     -Wl,--no-undefined \
> > -                     -Wl,-z,max-page-size=4096 -Wl,-z,common-page-size=4096 \
> > -                     $(DISABLE_LTO)
> > +VDSO_LDFLAGS_vdso.lds = -m elf_x86_64 -soname linux-vdso.so.1 --no-undefined \
> > +                     -z max-page-size=4096 -z common-page-size=4096
>
> Aside of the fact that it does not apply to upstream,

It seems to apply fine to Linus's tree (0585df4), but I'll send a v2
which is rediffed.

> why is this dropping
> the $(DISABLE_LTO) part?
>
> The changelog is utterly silent about that.

$ git grep DISABLE_LTO
arch/sparc/vdso/Makefile:KBUILD_CFLAGS += $(DISABLE_LTO)
arch/sparc/vdso/Makefile:                       $(DISABLE_LTO)
arch/x86/entry/vdso/Makefile:KBUILD_CFLAGS += $(DISABLE_LTO)
arch/x86/entry/vdso/Makefile:                   $(DISABLE_LTO)
kernel/Makefile:CFLAGS_sys_ni.o = $(DISABLE_LTO)
scripts/Makefile.build:cmd_cc_s_c       = $(CC) $(c_flags)
$(DISABLE_LTO) -fverbose-asm -S -o $@ $<

Looks like a dead option to me, but maybe somebody else knows better.
v2 will explain this removal.

> Thanks,
>
>         tglx