From: kernel mailz <kernelmailz@googlemail.com>
To: linuxppc-dev@ozlabs.org
Subject: 85xx Address space query
Date: Wed, 24 Jun 2009 15:14:31 +0530 [thread overview]
Message-ID: <abe8a1fd0906240244i6e33c260xadff5cf462df7b8c@mail.gmail.com> (raw)
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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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next reply other threads:[~2009-06-24 9:44 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-24 9:44 kernel mailz [this message]
2009-06-24 13:15 ` 85xx Address space query Kumar Gala
2009-06-24 17:46 ` kernel mailz
2009-06-24 22:52 ` Scott Wood
2009-06-25 10:51 ` kernel mailz
2009-06-25 17:32 ` Kumar Gala
2009-06-25 17:52 ` kernel mailz
2009-06-25 17:58 ` Kumar Gala
2009-06-25 19:34 ` Scott Wood
2009-06-25 11:33 ` Benjamin Herrenschmidt
2009-06-25 11:32 ` Benjamin Herrenschmidt
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