linux-kernel - Re: [PATCH] binfmt_elf: fix PIE load with randomization disabled

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Message-ID: <52A66235.3010405@zytor.com>
Date:	Mon, 09 Dec 2013 16:37:09 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"H.J. Lu" <hjl.tools@...il.com>
CC:	Jiri Kosina <jkosina@...e.cz>, LKML <linux-kernel@...r.kernel.org>,
	Josh Boyer <jwboyer@...hat.com>
Subject: Re: [PATCH] binfmt_elf: fix PIE load with randomization disabled

On 12/09/2013 03:53 PM, H.J. Lu wrote:
>>>
>>> x86-64 small model is limited to 4GB in size.  You can't build
>>> a dynamic executable in small model larger than 4GB.
>>>
>>> There are medium and large models.  But they are slower than
>>> small models as well as small models in PIE.  Also there are
>>> no glibc run-times for medium and large models.
>>>
>> Compiling for the small PIC model shouldn't automatically mean
>> generating a PIE (ET_DYN) executable, though (and if those are
>> inherently linked, that is a fundamental bug IMNSHO.)
> 
> PIE uses PIC. But GCC has -fPIE and -fPIC.  They aren't
> the same.   You build PIE with
> 
> 1. Compile with -fPIE.
> 2. Link with -pie.
> 

I'm talking about the memory model ("small PIC model").  I don't see why
it should be encapsulated in a PIE (ET_DYN) container if the user
doesn't want it to be relocatable.

	-hpa

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