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Re: RFC: Adding non-PIC executable support to MIPS

To: binutils@sourceware.org, gcc@gcc.gnu.org, linux-mips@linux-mips.org, dan@codesourcery.com, rdsandiford@googlemail.com
Subject: Re: RFC: Adding non-PIC executable support to MIPS
From: David VomLehn <dvomlehn@cisco.com>
Date: Mon, 30 Jun 2008 13:59:19 -0700
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Richard Sandiford wrote:
[Sorry for the 3-way crosspost!]

One of the big holes in the MIPS ABI has always been the lack of support
for non-PIC executables.
...

I'll describe my implementation
below, then compare it to what I understand CS's version to be.
CS folks: please correct me if I'm wrong.

This sounds like really good stuff and, on first reading, it all seems to make sense to me. My only real concern is documentation of these changes. The MIPS ABI (http://math-atlas.sourceforge.net/devel/assembly/mipsabi32.pdf) is currently moribund. The document that describes it hasn't been updated in since 1996 and gcc is not fully conformant (see, for example, the assumptions required for correct stack backtracing). It would take significant work to resurrect this but it certainly would be helpful to have a current document that completely describes the MIPS ABI, or at least the current ELF format, as currently implemented on Linux, especially if it is to be extended. The logical home for something like this would probably be the Linux Standard Base project hosted by the Linux Foundation.

--
David VomLehn, dvomlehn@cisco.com
The opinions expressed herein are likely mine, but might not be my employer's...




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