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Subject: Re: [RFC PATCH kernel] powerpc/stack_protector: Fix external modules
 building
To:     Masahiro Yamada <yamada.masahiro@socionext.com>
Cc:     linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Christophe Leroy <christophe.leroy@c-s.fr>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
References: <20190110054216.74248-1-aik@ozlabs.ru>
 <CAK7LNAQUDMhXxku2wqq=VX2cbntMWgsvrFL4C5Bk=x1TU79wjg@mail.gmail.com>
From:   Alexey Kardashevskiy <aik@ozlabs.ru>
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Message-ID: <5e10e136-5c9f-91bf-bf5e-f546635b9ee6@ozlabs.ru>
Date:   Fri, 11 Jan 2019 15:09:55 +1100
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On 11/01/2019 14:08, Masahiro Yamada wrote:
> On Thu, Jan 10, 2019 at 2:44 PM Alexey Kardashevskiy <aik@ozlabs.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@ozlabs.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?

YES! Thanks :)

> 
> 
> 
> 
>>  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
>>
> 
> 

-- 
Alexey