ring on PowerPC

Wang, Baojun wangbj at lzu.edu.cn
Wed Oct 31 17:12:34 EST 2007

On Wednesday 31 October 2007 13:05:16, Bai Shuwei wrote:
> Hi, everyone
>    As we know, the program on the X86 can run on the differnt ring(0, 1, 2,
> 3) and the linux kernel run in the ring 0 and user program in the ring 3.
> And now I want to know wether there is a simple mechanism on the PowerPC
> architecture? thx all!
> best regards!
> Buroc

powerpc has a machine state register(MSR), bit MSR_PR present the current 
privilege level, if msr & MSR_PR, then it's from user space, otherwise(msr & 
MSR_PR == 0) it's kernel space.

besides, the linux implementation only use ring0 and ring3 under i386, ring0 
is highest(kernel space), ring3 is lowest (userspace)

Wang, Baojun                                        Lanzhou University
Distributed & Embedded System Lab              http://dslab.lzu.edu.cn
School of Information Science and Engeneering        wangbj at lzu.edu.cn
Tianshui South Road 222. Lanzhou 730000                     .P.R.China
Tel:+86-931-8912025                                Fax:+86-931-8912022
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