Update PS2 R5900 to kernel 4.x?

[Fredrik Noring <noring@xxxxxxxxxx>]

Hello MIPS maintainers,

I'm trying update the PS2 R5900 patch to kernel version 4.x. I started
at 2.6.35 and it was easy up to v3.9-rc1 commit 64b3122 which crashes with
a memory fault at boot:

  commit 64b3122df48b81a40366a11f299ab819138c96e8
  Author: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
  Date:   Thu Dec 27 11:52:32 2012 -0500
  
      mips: take the "zero newsp means inherit the parent's one" to copy_thread()
      
      Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>

I've pushed the patched (working) parent commit here:

  https://github.com/frno7/linux/tree/ps2-v3.9-rc1-974fdb3

The whole PS2 R5900 patch is quite large, but I suspect the problem is limited
to changes in arch/mips/kernel, more specifically:

  arch/mips/kernel/process.c
  arch/mips/kernel/scall32-n32.S
  arch/mips/kernel/syscall.c

(Several system calls etc. have been rearranged since 2.6.35.) I've been stuck
for a couple of days trying to get this to work. Would anyone be able to help?

Many thanks,
Fredrik