linux-kernel - Re: [PATCH v1] Arm64: ASLR: fix text randomization

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Message-ID: <20141008112154.GF26140@arm.com>
Date:	Wed, 8 Oct 2014 12:21:55 +0100
From:	Will Deacon <will.deacon@....com>
To:	Arun Chandran <achandran@...sta.com>
Cc:	Mark Rutland <Mark.Rutland@....com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Anton Blanchard <anton@...ba.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [PATCH v1] Arm64: ASLR: fix text randomization

On Wed, Oct 08, 2014 at 07:51:54AM +0100, Arun Chandran wrote:
> On Tue, Oct 7, 2014 at 7:13 PM, Mark Rutland <mark.rutland@....com> wrote:
> > I wasn't able to spot where the randomness came from in the
> > ARCH_BINFMT_ELF_RANDOMIZE_PIE case, so it's not clear to me if the
> > generic implementation behaves identically other than disabling
> > randomization when told to via proc.
> 
> I also don't know from where it is coming; but it works on arm and x86 :)

The randomness will come from elf_map, since that will descend into the mmap
code and end up with a randomised base address (see mmap_base and
arch_pick_mmap_layout).

Will
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