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Accessing CP14 from user mode

Note: This was originally posted on 9th July 2009 at http://forums.arm.com

Hello,

I'm currently trying to change the frequency of a PXA270 processor, the system I'm working on is a Linux OS, and I would like to write a code that allows an user to change the frequency, to do so I need to write in a register of coprocessor 14. According to ARM documentation i need to use MRC/MCR instructions, I tried but I got an error : "Illegal instruction".

So I think I need to switch to supervisor mode, it seems that I could do it using SWI but even after reading some documentation I don't know how I should implement this.
I'm not even sure that what I want to do is possible, but if it is, does someone have any idea of the code I should write to switch to supervisor mode and use MRC or MCR instruction?

Thanks,

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ivan lovric over 12 years ago

Note: This was originally posted on 13th July 2009 at http://forums.arm.com

Hi,

I managed to access coprocessor 14 and 15 of the ARM from the user space. I built an small prog which modifies the registers depending on user requirements.

It was difficult to achieve, but now it workd fine and I can modify clock speed or power management from the user space.

If interested, I can send you the prog.

Regards,
____________
Ivan Lovric
ESECO SYSTEMS
Web3.0 for security
[url="http://www.eseco.fr"]http://www.eseco.fr[/url]
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ivan lovric over 12 years ago

Note: This was originally posted on 13th July 2009 at http://forums.arm.com

Hi,

I managed to access coprocessor 14 and 15 of the ARM from the user space. I built an small prog which modifies the registers depending on user requirements.

It was difficult to achieve, but now it workd fine and I can modify clock speed or power management from the user space.

If interested, I can send you the prog.

Regards,
____________
Ivan Lovric
ESECO SYSTEMS
Web3.0 for security
[url="http://www.eseco.fr"]http://www.eseco.fr[/url]
Cancel
Vote up 0 Vote down

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