linux-kernel - Re: [RFC PATCH] kbuild: add -fno-PIE

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Message-ID: <87eg33kni0.fsf@turtle.gmx.de>
Date:   Wed, 26 Oct 2016 19:51:03 +0200
From:   Sven Joachim <svenjoac@....de>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Joe Perches <joe@...ches.com>, Adam Borowski <kilobyte@...band.pl>,
        Michal Marek <mmarek@...e.com>, linux-kbuild@...r.kernel.org,
        linux-kernel@...r.kernel.org, ben@...adent.org.uk
Subject: Re: [RFC PATCH] kbuild: add -fno-PIE

On 2016-10-25 09:30 +0200, Sebastian Andrzej Siewior wrote:

> On 2016-10-24 19:32:30 [+0200], Sven Joachim wrote:
>> On 2016-10-24 09:43 +0200, Sebastian Andrzej Siewior wrote:
>> 
>> > On 2016-10-24 09:38:49 [+0200], Sven Joachim wrote:
>> >> 
>> >> But make still fails with it. :-(
>> >
>> > try setting CONFIG_CC_STACKPROTECTOR_NONE=y and please let me know if
>> > the resulting kernel built with v3.2 gcc boots & works.
>> 
>> Sorry, I don't have gcc 3.2 around, and my gcc 3.3 environment produces
>> assembler errors in arch/x86/entry/entry_32.S.  Maybe binutils 2.15 is
>> not recent enough anymore?

I have done a few more tests, and I can confirm that binutils 2.17 is
the oldest version that works.  Also, I have succeeded installing gcc
3.2 in a Debian 4.0 chroot now.

> so we use stone age gcc but take latest binutils and kernel? What about
> lifting the limit of gcc 3.2?

Would probably make sense, since gcc 3.2 cannot compile kernel/bounds.c,
at least not on x86.

,----
|   CC      kernel/bounds.s
| In file included from /tmp/linux/arch/x86/include/asm/bitops.h:512,
|                  from include/linux/bitops.h:22,
|                  from include/linux/kernel.h:10,
|                  from include/asm-generic/bug.h:13,
|                  from /tmp/linux/arch/x86/include/asm/bug.h:38,
|                  from include/linux/bug.h:4,
|                  from include/linux/page-flags.h:9,
|                  from kernel/bounds.c:9:
| /tmp/linux/arch/x86/include/asm/arch_hweight.h: In function `__arch_hweight32':
| /tmp/linux/arch/x86/include/asm/arch_hweight.h:29: syntax error before string constant
| make[1]: *** [kernel/bounds.s] Error 1
`----

Building with gcc 3.3 is apparently still possible, although it produces
tons of warnings and a modpost section mismatch.  Still, requiring gcc
4.1 or newer would not be unreasonable, I think (still released a few
months earlier than binutils 2.17).

Cheers,
       Sven