* linux PowerPC 85xx Address space query
[not found] <abe8a1fd0906240341h2ed015a2pf83785efed8de1b5@mail.gmail.com>
@ 2009-06-24 10:45 ` kernel mailz
0 siblings, 0 replies; only message in thread
From: kernel mailz @ 2009-06-24 10:45 UTC (permalink / raw)
To: linux-kernel
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
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[not found] <abe8a1fd0906240341h2ed015a2pf83785efed8de1b5@mail.gmail.com>
2009-06-24 10:45 ` linux PowerPC 85xx Address space query kernel mailz
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