book e idea

[Paul Mackerras]

Ralph Blach writes:

> could the OS be run in translation state 0, and and the users in 
> translation state 1?

Yes, it is possible.  The main problem that it would introduce is that
copy_to_user, copy_from_user, put_user, get_user etc. would no longer
be able to access user space directly but would instead have to set up
page mappings, and would therefore become bigger and slower.

> The advantage to this would be is that user task could have true 4 gb 
> addressing on a and so could the kernel.

Yes.  There doesn't seem to be a lot of pressure for giving userspace
more than 2GB in the embedded world though.

Paul.