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

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Date:	Mon, 9 Dec 2013 16:41:38 -0800
From:	"H.J. Lu" <hjl.tools@...il.com>
To:	"H. Peter Anvin" <hpa@...or.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 Mon, Dec 9, 2013 at 4:37 PM, H. Peter Anvin <hpa@...or.com> wrote:
> 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.
>

I see.  Maybe linker can set ET_EXEC if vaddr is non-zero.


-- 
H.J.
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