Re: __copy_user bug

[Paul M. <le...@li...>]

On Thu, Nov 01, 2007 at 07:55:57PM +0000, Stuart MENEFY wrote:
> Looking at the code, there is a movca.l in there, which IIRC isn't
> available on an SH3.
> 
> Although given that, I don't understand how this even builds.
> 
In order for it to blow up the ISA tuning has to be just right, or else
any supported opcode won't complain. This is part of why the ISA
selection in arch/sh/Makefile is such a pain, especially as the various
toolchains make it a total grab-bag with regards to what flags can be
supported and which ones can't.

Initially it was helpful on SH-2/SH-2A for finding all of the register
bank accessors, as otherwise they would all build in successfully and
just generate some fairly interesting bugs.

Some places manage to elude the ISA tuning completely as well by just
hardcoding the opcodes and operands in hex due to certain toolchains not
undertanding the opcode mnemonics at all. This happens with the DSP state
save/restore, for example.

It's something we can slowly fix up, but there are unfortunately far too
many varied toolchains out in the wild with utterl conflicting behaviour.