[uClinux-dev] Re: Porting Linux programs to uClinux and other

[Mike Frysinger]

On Monday 05 November 2007, Gavin Lambert wrote:
> Quoth Mike Frysinger:
> > while some processors lack an MMU, then do not lack an MPU (memory
> > protection unit).  for example, the Blackfin processor has an MPU which
> > means the Blackfin Linux port can (and does) prevent user space from
> > accessing peripherals.  we can (and have an experimental/in-development
> > patch) also protect processes from other processes and kernel space
> > from user space, but the overhead here seems to be noticeable since the
> > hardware table can only contain 16 entries.
>
> Many Coldfire CPUs also support memory protection, although last time I
> checked the kernel didn't enforce it.

we'll probably go the route of offering it but not enabling it by default due 
to performance impact

i think FRV also has some stuff, but the way it's implemented in hardware 
makes it useless to Linux (memory protection violation occurs *after* 
instruction execution rather than *before* so the modification happens (!) 
and then the processor tells software about it)
-mike
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 827 bytes
Desc: This is a digitally signed message part.
Url : http://mailman.uclinux.org/pipermail/uclinux-dev/attachments/20071105/a03c071a/attachment.pgp