Re: [PATCH -v1.1] kbuild: Steal gcc's pie from the very beginning

[Michal Marek <mmarek@suse.com>]

On Mon, Nov 14, 2016 at 09:45:29PM +0100, Borislav Petkov wrote:
> From: Borislav Petkov <bp@suse.de>
> Date: Mon, 14 Nov 2016 19:41:31 +0100
> Subject: [PATCH] kbuild: Steal gcc's pie from the very beginning
> 
> So Sebastian turned off the PIE for kernel builds but that was too late
> - Kbuild.include already uses KBUILD_CFLAGS and trying to disable gcc
> options with, say cc-disable-warning, fails:
> 
>   gcc -D__KERNEL__ -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs
>   ...
>   -Wno-sign-compare -fno-asynchronous-unwind-tables -Wframe-address -c -x c /dev/null -o .31392.tmp
>   /dev/null:1:0: error: code model kernel does not support PIC mode
> 
> because that returns an error and we can't disable the warning. For
> example in this case:
> 
> KBUILD_CFLAGS   += $(call cc-disable-warning,frame-address,)
> 
> which leads to gcc issuing all those warnings again.
> 
> So let's turn off PIE/PIC at the earliest possible moment, when we
> declare KBUILD_CFLAGS so that cc-disable-warning picks it up too.
> 
> Also, we need the $(call cc-option ...) because -fno-PIE is supported
> since gcc v3.4 and our lowest supported gcc version is 3.2 right now.
> 
> Signed-off-by: Borislav Petkov <bp@suse.de>
> Cc: stable@vger.kernel.org
> Cc: Ben Hutchings <ben@decadent.org.uk>
> Cc: Michal Marek <mmarek@suse.com>
> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Thanks, applied to kbuild.git#rc-fixes.

Michal