On Mon, Apr 18, 2011 at 9:17 PM, limp <johnkyr83@xxxxxxxxxxx> wrote:
Hi all,
I am trying to understand in what extend the PGD (page global directory)
value stored in the CR3 register indicate the running process/thread by the
Linux scheduler.
I know that each process has its own PGD value but what I am confused about
is the value of CR3 register when kernel threads are scheduled.
yes, each process has its own CR3 value -> u can easily see this when u do a printk() of it....and it is always equal to the process (which is "insmod" usually) that started the kernel module. i experimented it here:
AFAIK, a "kernel thread" can 'borrow' the page-directory that belongs to
another process (i.e. its address space). Does this apply *only* to threads
yes, "borrow" in the sense that: kernel thread DOES NOT have any process context, and so it can be executed in any process context, and which ever process context it is executing, when u print the CR3 value, it will belong to that process which the kernel thread is currently executing under.
read this:
of the same process (i.e. all the threads of process A are using the PGD
entry of process A) or could also apply to threads not relevant to process
A?
That is, if a thread is executed and the value of CR3 at the time is
0x1E107000, does this *necessary* mean that a thread of the process with PGD
0xDE107000 is executed *or* a thread not relevant with that process could
have 'borrowed' its PGD entry?
Any help will be greatly appreciated.
John K.
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Regards,
Peter Teoh
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