linux-kernel - Re: [PATCH v2 2/3] MIPS: VDSO: Move disabling the VDSO logic to Kconfig

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Date:   Thu, 23 Apr 2020 23:41:56 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     Sedat Dilek <sedat.dilek@...il.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        linux-mips@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Clang-Built-Linux ML <clang-built-linux@...glegroups.com>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Dmitry Golovin <dima@...ovin.in>
Subject: Re: [PATCH v2 2/3] MIPS: VDSO: Move disabling the VDSO logic to Kconfig

On Tue, Apr 21, 2020 at 11:43 AM Nathan Chancellor
<natechancellor@...il.com> wrote:
>
> On Mon, Apr 20, 2020 at 11:53:55AM +0200, Sedat Dilek wrote:
> > On Sun, Apr 19, 2020 at 10:21 PM Nathan Chancellor
> > <natechancellor@...il.com> wrote:
> > >
> > > After commit 9553d16fa671 ("init/kconfig: Add LD_VERSION Kconfig"), we
> > > have access to GNU ld's version at configuration time. As a result, we
> > > can make it clearer under what configuration circumstances the MIPS VDSO
> > > needs to be disabled.
> > >
> > > This is a prerequisite for getting rid of the MIPS VDSO binutils
> > > warning and linking the VDSO when LD is ld.lld. Wrapping the call to
> > > ld-ifversion with CONFIG_LD_IS_LLD does not work because the config
> > > values are wiped away during 'make clean'.
> > >
> > > Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> > > ---
> > >
> > > v1 -> v2:
> > >
> > > * New patch.
> > >
> > >  arch/mips/Kconfig         |  2 ++
> > >  arch/mips/vdso/Kconfig    | 18 ++++++++++++++++++
> > >  arch/mips/vdso/Makefile   | 30 ++----------------------------
> > >  arch/mips/vdso/vdso.lds.S |  2 +-
> > >  4 files changed, 23 insertions(+), 29 deletions(-)
> > >  create mode 100644 arch/mips/vdso/Kconfig
> > >
> > > diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> > > index 690718b3701a..45220e4b8a65 100644
> > > --- a/arch/mips/Kconfig
> > > +++ b/arch/mips/Kconfig
> > > @@ -3275,3 +3275,5 @@ endmenu
> > >  source "drivers/firmware/Kconfig"
> > >
> > >  source "arch/mips/kvm/Kconfig"
> > > +
> > > +source "arch/mips/vdso/Kconfig"
> > > diff --git a/arch/mips/vdso/Kconfig b/arch/mips/vdso/Kconfig
> > ...
> > > --- /dev/null
> > > +++ b/arch/mips/vdso/Kconfig
> > ...
> > > +config MIPS_DISABLE_VDSO
> > > +       def_bool CPU_MICROMIPS || (!CPU_MIPSR6 && !MIPS_LD_CAN_LINK_VDSO)
> > ...
> > > diff --git a/arch/mips/vdso/vdso.lds.S b/arch/mips/vdso/vdso.lds.S
> > ...
> > > --- a/arch/mips/vdso/vdso.lds.S
> > > +++ b/arch/mips/vdso/vdso.lds.S
> > ...
> > > -#ifndef DISABLE_MIPS_VDSO
> > > +#ifndef CONFIG_DISABLE_MIPS_VDSO
> >
> > Should be s/CONFIG_DISABLE_MIPS_VDSO/CONFIG_MIPS_DISABLE_VDSO ?
> >
> > - Sedat -
>
> Ugh yes, thank you much for pointing it out.
>
> I'll send a v3 once I get further feedback on the series.


I just wondered if we could raise the minimal binutils
version from 2.23 to 2.25, but it might be too aggressive...
I do not know.

Other than what Sedat pointed out, this looks good me.

-- 
Best Regards
Masahiro Yamada