From: kernel mailz <kernelmailz@googlemail.com>
To: linux-kernel@vger.kernel.org
Subject: linux PowerPC 85xx Address space query
Date: Wed, 24 Jun 2009 16:15:41 +0530 [thread overview]
Message-ID: <abe8a1fd0906240345y3e50e8bck59e7c8682c81713e@mail.gmail.com> (raw)
In-Reply-To: <abe8a1fd0906240341h2ed015a2pf83785efed8de1b5@mail.gmail.com>
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
parent reply other threads:[~2009-06-24 10:45 UTC|newest]
Thread overview: expand[flat|nested] mbox.gz Atom feed
[parent not found: <abe8a1fd0906240341h2ed015a2pf83785efed8de1b5@mail.gmail.com>]
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