John-Mark Gurney wrote:
Aziz Kezzou wrote this message on Tue, Jun 14, 2005 at 04:21 -0400:
I have two questions concerning FreeBSD Memory management :
1 - Right now to access the memory address space of a user process
from kernel mode, I only have to set, on x86 systems, the register CR3
to the right value. How can I do that on other architectures ? is
there an architecture-independant way of doing that ?
2- I have noticed that while in kernel mode the value of CR3 is equal
to that of the user process beeing interrupted. Doesn't the kernel
supposed to have its "own" page-directory, i.e it's own CR3 value ?
or is kernel virtual address resolution does not go through CR3 at
all ?
You should be using copyin(9)/copyout(9) instead of playing around with
CR3 directly... or fuword(9)/suword(9)... This provides a platform
independant way of accessing user's memory (for the current running
process)...
Not to mention that setting CR3, or whatever on other platforms, doesn't
handle accessing pages that have been swapped out. That's the real
magic that copyin/copyout does.
Scott
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