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From:   Masahiro Yamada <yamada.masahiro@socionext.com>
Date:   Tue, 15 Jan 2019 23:58:03 +0900
Message-ID: <CAK7LNAS+YAfHQkSWDEnuLv869VTy3iaXoYpmZSOBbPrVAaF0Cw@mail.gmail.com>
Subject: Re: [PATCH] kbuild: mark prepare0 as PHONY to fix external module build
To:     Mathieu Malaterre <malat@debian.org>
Cc:     linux-kbuild <linux-kbuild@vger.kernel.org>,
        Michal Marek <michal.lkml@markovi.net>,
        Samuel Holland <samuel@sholland.org>,
        Alexey Kardashevskiy <aik@ozlabs.ru>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        LKML <linux-kernel@vger.kernel.org>,
        "linux-stable # v4 . 20" <stable@vger.kernel.org>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
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Sender: linux-kernel-owner@vger.kernel.org
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On Tue, Jan 15, 2019 at 7:35 PM Mathieu Malaterre <malat@debian.org> wrote:
>
> On Tue, Jan 15, 2019 at 8:22 AM Masahiro Yamada
> <yamada.masahiro@socionext.com> wrote:
> >
> > Commit c3ff2a5193fa ("powerpc/32: add stack protector support")
> > caused kernel panic on PowerPC if an external module is used with
> > CONFIG_STACKPROTECTOR because the 'prepare' target was not executed
> > for the external module build.
> >
> > Commit e07db28eea38 ("kbuild: fix single target build for external
> > module") turned it into a build error because the 'prepare' target is
> > now executed but the 'prepare0' target is missing for the external
> > module build.
> >
> > External module on arm/arm64 with CONFIG_STACKPROTECTOR_PER_TASK is
> > also broken in the same way.
> >
> > Move 'PHONY += prepare0' to the common place. Make is fine with missing
> > rule for phony targets.
> >
> > I minimize the change so it can be easily backported to 4.20.x
> >
> > To fix v4.20 for external modules of PowerPC, please backport
> > e07db28eea38 ("kbuild: fix single target build for external module"),
> > and then this commit.
> >
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=201891
> > Fixes: e07db28eea38 ("kbuild: fix single target build for external module")
> > Fixes: c3ff2a5193fa ("powerpc/32: add stack protector support")
> > Fixes: 189af4657186 ("ARM: smp: add support for per-task stack canaries")
> > Fixes: 0a1213fa7432 ("arm64: enable per-task stack canaries")
> > Cc: linux-stable <stable@vger.kernel.org> # v4.20
> > Reported-by: Samuel Holland <samuel@sholland.org>
> > Reported-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> > ---
> >
> >  Makefile | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/Makefile b/Makefile
> > index 499b968..789b332 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -955,6 +955,7 @@ ifdef CONFIG_STACK_VALIDATION
> >    endif
> >  endif
> >
> > +PHONY += prepare0
> >
> >  ifeq ($(KBUILD_EXTMOD),)
> >  core-y         += kernel/ certs/ mm/ fs/ ipc/ security/ crypto/ block/
> > @@ -1061,8 +1062,7 @@ scripts: scripts_basic scripts_dtc
> >  # archprepare is used in arch Makefiles and when processed asm symlink,
> >  # version.h and scripts_basic is processed / created.
> >
> > -# Listed in dependency order
>
> The above comment may need to be tweaked a bit

The comment is wrong irrespective of this patch,
and less important.

Do you have any suggestion how to tweak it?


> > -PHONY += prepare archprepare prepare0 prepare1 prepare2 prepare3
> > +PHONY += prepare archprepare prepare1 prepare2 prepare3
> >
> >  # prepare3 is used to check if we are building in a separate output directory,
> >  # and if so do:
> > --
> > 2.7.4
> >


-- 
Best Regards
Masahiro Yamada