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Date: Thu, 12 Dec 2013 07:42:24 -0800
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Subject: Re: RFC: binutils PATCH: Set e_type to ET_EXEC for -pie -Ttext-segment=
From: "H.J. Lu" <hjl.tools@gmail.com>
To: LKML <linux-kernel@vger.kernel.org>, Binutils <binutils@sourceware.org>
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On Tue, Dec 10, 2013 at 2:47 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Tue, Dec 10, 2013 at 2:36 PM, Alan Modra <amodra@gmail.com> wrote:
>> On Mon, Dec 09, 2013 at 07:10:23PM -0800, H.J. Lu wrote:
>>> Linker sets e_type in ELF header to ET_DYN for -pie -Ttext-segment=0xXXX.
>>> When I added -Ttext-segment=0xXXX, one goal was to load
>>> small model executable above 4GB on Linux/x86-64, which
>>> was done with -pie -Ttext-segment=0xXXX.  But -pie sets
>>> e_type in ELF header to ET_DYN and kernel may ignore
>>> p_vaddr in ELF header to load ET_DYN binary at a random
>>> address.  This patch changes ld to set e_type in ELF header
>>> to ET_EXEC if the first PT_LOAD segment has non-zero
>>> p_vaddr.  If this is unacceptable as generic ELF change,
>>> I can make it specific to x86.
>>
>> Well, I suppose it's a hack to use ET_DYN for executables in the first
>> place, so one more hack in the linker hardly matters.  Why not just
>> patch the kernel though?  The kernel can look at the first PT_LOAD
>> header just as easily as the linker, and it's the kernel that is doing
>> the loading after all.
>>
>
> Kernel should have some freedom on where to load ET_DYN object.
> But when -Ttext-segment= is used, programmer expects the
> executable will be loaded at the specified address.  Setting
> ET_EXEC will guarantee that it will be loaded at that address.
>

I checked it in with 2 testcases.

-- 
H.J.