From mboxrd@z Thu Jan  1 00:00:00 1970
From: vladimir.murzin@arm.com (Vladimir Murzin)
Date: Thu, 11 Oct 2018 15:23:05 +0100
Subject: [RFC 17/17] arm64: compile the kernel with ptrauth
 -msign-return-address
In-Reply-To: <20181005084754.20950-18-kristina.martsenko@arm.com>
References: <20181005084754.20950-1-kristina.martsenko@arm.com>
 <20181005084754.20950-18-kristina.martsenko@arm.com>
Message-ID: <d0e36e1f-fa1a-f4ab-5a83-11e095801fef@arm.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

Hi Kristina,

On 05/10/18 09:47, Kristina Martsenko wrote:
> diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
> index 106039d25e2f..dbcd43ea99d8 100644
> --- a/arch/arm64/Makefile
> +++ b/arch/arm64/Makefile
> @@ -56,6 +56,10 @@ KBUILD_AFLAGS	+= $(lseinstr) $(brokengasinst)
>  KBUILD_CFLAGS	+= $(call cc-option,-mabi=lp64)
>  KBUILD_AFLAGS	+= $(call cc-option,-mabi=lp64)
>  
> +ifeq ($(CONFIG_ARM64_PTR_AUTH),y)
> +KBUILD_CFLAGS	+= -msign-return-address=all
> +endif

Should not it be done via cc-option so old toolchains keep working [1]?

[1]
$ aarch64-linux-gnu-gcc --version
aarch64-linux-gnu-gcc (Linaro GCC 2014.11) 4.9.3 20141031 (prerelease)
Copyright (C) 2014 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ aarch64-linux-gnu-gcc -msign-return-address=all
aarch64-linux-gnu-gcc: error: unrecognized command line option '-msign-return-address=all'
...

Cheers
Vladimir