Rahul Kulkarni wrote:
> Thanks much in advance for all you replies. appreciate it.
> 
> Hmm..If I understand this right..since the USERSR is valid during a
> copy{in,out} a buggy sysem call / ioctl can potentially corrupt user
> space though highly improbable.
> 
> I'm debugging a condition where a byte gets corrupted in the user
> space, (extremely hard to reproduce) and after pouring over user space
> code now trying to rule out home grown system calls/ioctls since the
> user process does make a bunch of system calls/ioctls.

in random processes, or in one particular process?

> I'm thinking ways of to generate a DSI/exception to catch/rule out
> bugs of the above type ..can you think of  any?

Yep.  But it depends on how the bug is manifesting itself.

> Is there a way to BAT map only the first 256 MB of the physical memory
> and move the copy{in,out} operations to that area?  If yes, what are
> the other implications?

No.

> Is it mandatory to BAT map the complete physical memory for certain PPC  MMU's?

Basically, yes.

-- 
Matt Thomas                     email: matt@3am-software.com
3am Software Foundry              www: http://3am-software.com/bio/matt/
Cupertino, CA              disclaimer: I avow all knowledge of this message.