linux-kernel - Re: [RFC PATCH kernel] powerpc/stack_protector: Fix external modules building

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Date:   Fri, 11 Jan 2019 12:08:04 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Alexey Kardashevskiy <aik@...abs.ru>
Cc:     linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Christophe Leroy <christophe.leroy@....fr>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH kernel] powerpc/stack_protector: Fix external modules building

On Thu, Jan 10, 2019 at 2:44 PM Alexey Kardashevskiy <aik@...abs.ru> wrote:
>
> c3ff2a519 "powerpc/32: add stack protector support" addes stack protector
> support so now powerpc's "prepare" target depends on prepare0 (via
> stack_protector_prepare target).
>
> It works fine until we try build an external module where it fails with:
> Run: 'make -j128 SYSSRC=/home/aik/p/kernel SYSOUT=/home/aik/pbuild/kernel-le-pseries/ ARCH=powerpc'
> make[1]: Entering directory '/home/aik/p/kernel'
> make[2]: Entering directory '/home/aik/pbuild/kernel-le-pseries'
> make[2]: *** No rule to make target 'prepare0', needed by 'stack_protector_prepare'.  Stop.
>
> The reason for that is that the main Linux Makefile defines "prepare0"
> only if KBUILD_EXTMOD=="".
>
> This hacks powerpc's Makefile to make external modules build again.
>
> Fixes: c3ff2a519 "powerpc/32: add stack protector support"
> Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
> ---
>
>
> It has been suggested that there is a better way of fixing this hence RFC.
>
>
> ---
>  arch/powerpc/Makefile | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
> index 488c9ed..0492f62 100644
> --- a/arch/powerpc/Makefile
> +++ b/arch/powerpc/Makefile
> @@ -419,7 +419,11 @@ archheaders:
>  ifdef CONFIG_STACKPROTECTOR
>  prepare: stack_protector_prepare
>
> +ifeq ($(KBUILD_EXTMOD),)
>  stack_protector_prepare: prepare0
> +else
> +stack_protector_prepare:
> +endif


Honestly, I think this is ugly.

Do you want me to send an alternative solution?




>  ifdef CONFIG_PPC64
>         $(eval KBUILD_CFLAGS += -mstack-protector-guard-offset=$(shell awk '{if ($$2 == "PACA_CANARY") print $$3;}' include/generated/asm-offsets.h))
>  else
> --
> 2.17.1
>


-- 
Best Regards
Masahiro Yamada