R5900 binary patcher

[llsant]

According to this:

https://github.com/frno7/linux/wiki/R5900-processor-specific-ABI-%28psABI%29

It seems like the main impediment for running, let's say, a precompiled debian mipsel binary, is the short loop bug.

At least from what I understand from that wiki page, even if the EE has some extra instructions (some from MIPS IV and various SIMD operations), it shouldn't matter if they're not used by generic MIPS III, 64 bit, little endian binaries. The LL, SC and FPU behavior is already trapped and emulated by the PS2 Linux kernel. There's already a tool in this repo that can scan and detect short loops in binaries, so my question is:

Would it be possible to improve that detector into a patcher? A piece of software that can rewrite these short loops to convert a generic Linux MIPS III, 64 bit Little Endian executable into something suitable for PS2 Linux. In principle, copying the code into another ELF segment, padding it to avoid the short loop bug, and calling it from the original place should be possible.

Such a tool would be useful because it could be used to patch whole precompiled debian mipsel packages and make them run on PS2 Linux.

If this is not possible, what exactly, apart from the short loop bug, makes a regular MIPS III, 64 bit, LE, Linux binary unrunnable on this R5900 kernel?

Have a nice day.

[frno7]

I suppose preexisting libraries and programs could be patched for the short loop erratum, in principle. But it seems easier to let official Debian/MIPS packages be compiled with the -mfix-r5900 option, don’t you think? That’s what precompiled Gentoo/MIPS packages have since gentoo/catalyst@85c6f6a.

[immolo]

Looking at the Debian docs it does seems like this is possible to have -mfix-r5900 if someone wanted to contact the Debian MIPS team. I'd imagine before the release of Bookworm would have been the perfect time to ask however better late than never.

I'll list some pages I've found that will help anyone that wants to take up the mantle for a Debian port:

Debian MIPS Project
PortsDocs/New System
PortsDocs/New

Likely though all that will be required is someone to email mailing list and or speaking on their IRC server in #debian-mips and asking if they will add the CFLAG option, then write up some documentation for showing other how to do it.