linux-kernel - Re: powerpc: Fix Text randomization

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Message-ID: <CAOpNGcsgX0wVOgMN77+RuKVsb_iHQ7XQk8U_05-up__wC6zuZQ@mail.gmail.com>
Date:	Wed, 15 Oct 2014 12:08:29 +0530
From:	Vineeth Vijayan <vvijayan@...sta.com>
To:	Michael Ellerman <mpe@...erman.id.au>
Cc:	benh@...nel.crashing.org, linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org
Subject: Re: powerpc: Fix Text randomization

On Wed, Oct 15, 2014 at 7:38 AM, Michael Ellerman <mpe@...erman.id.au> wrote:
> On Fri, 2014-10-10 at 05:45:26 UTC, Vineeth Vijayan wrote:
>> Right now there is no way to disable TEXT randomization on a PPC32
>> machine. text randomization happens even in the case of "echo 0 >
>> /proc/sys/kernel/randomize_va_space"
>
> Yeah it seems to happen on ppc64 too.
>
>> This happens due to the incorrect definition of ELF_ET_DYN_BASE at
>> arch/powerpc/include/asm/elf.h
>
> What is incorrect about it? We are not the only arch that does that.
>

I think we are one of the arch which does it.
The same has been tested on x86 and arm, where ELF_ET_DYN_BASE doesn’t
use randomize_et_dyn call, and it works properly as per the user-space
definition of randomization;

(i.e when at "echo 0 > /proc/sys/kernel/randomize_va_space", TEXT
randomization should not happen.)

> I'm not clear on what has changed to break this?
>
> cheers
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