Re: [Gumstix-users] Overo: access to "nonsecure privileged" mode

[Dave H. <dhy...@gm...>]

Hi John,

On Tue, Apr 7, 2009 at 7:04 AM, John Wilson <joh...@er...> wrote:
> How do I execute something in “nonsecure privileged” mode on the Overo?
> Specifically, I want to access the CCNT, USEREN, and PMNC registers of the
> Cortex-A8.  I know the instructions to access these registers, but for
> instance when I try to access the PMNC resister from standard user mode I
> just get a message “Illegal instruction”.

As a general rule, you can't access registers from userspace.

What can do, is do is mmap in the register space into user space and
access the registers that way, similar to what pxaregs does, or the
gpio sample (for the pxa)
<http://docswiki.gumstix.com/index.php/Sample_code/C/gpregs>

Obviously, this program won't work as presented on the OMAP, but the
mmap technique should work the same.

-- 
Dave Hylands
Shuswap, BC, Canada
http://www.DaveHylands.com/