2008-07-29 10:15:35     blackfin uclinux and memory protection

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2008-07-29 10:15:35     blackfin uclinux and memory protection

murti iki (GERMANY)

Message: 59553   

 

Hello

 

I am wondering if a user space application can access the hardware registers directly. So far

 

I thought that since a user space application runs in user_mode, accessing a hardware

 

register would cause an exception to occur. However I have recently came across the

 

"makig the blackfin perform" article in wiki and there CYCLES register is accessed directly

 

from a user space program.

 

Is it the case that some hardware registers like CYCLES can be accessed while peripheral

 

registers cannot?

 

thank you for your help

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2008-07-29 11:08:44     Re: blackfin uclinux and memory protection

Mike Frysinger (UNITED STATES)

Message: 59558   

 

CYCLES is a core register, it is not a system or core register (MMR).  unfortunately, it is R/W for user and higher.

 

review the Blackfin PRM/HRM if you really want to know access permission modes (user vs supervisor vs emulation).

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