85xx Address space query

[kernel mailz]

Hi,

I am a newbie, trying to learn but have a few queries, nice if you could
respond
For linux on 85xx systems...

(a) Kernel code runs in PR=0 AS=0 and PID=0, which user space application
run in PR=1 AS=0 and PID 1-255.
Is this correct.

(b) I am writing a small program where the application code opens invokes a
ioctl call and passes a buffer pointer ( say 0x10000 in user space)
Now the driver code is using copy_from_user.
How this works internally ?

1. User code executes ioctl
2. interrupt goes to the kernel
3. ioctl handler in driver gets invoked
The buffer pointer still contains 0x10000.

How kernel code running in PR=0 accesses it and does the copy. I am not able
to see a address space switch in the asm code of copy_tofrom_user.

Please respond

-TRX
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.ozlabs.org/pipermail/linuxppc-dev/attachments/20090624/3326a7d2/attachment.htm>