Date: Tue, 14 Jun 2005 14:22:14 -0700 From: John-Mark Gurney <gurney_j@resnet.uoregon.edu> To: Aziz Kezzou <french.linuxian@gmail.com> Cc: freebsd-hackers <freebsd-hackers@freebsd.org>, freebsd-net <freebsd-net@freebsd.org> Subject: Re: FreeBSD Memory Management questions ? Message-ID: <20050614212214.GK742@funkthat.com> In-Reply-To: <37273927050614012154fdb80b@mail.gmail.com> References: <37273927050614012154fdb80b@mail.gmail.com>
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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)...
--
John-Mark Gurney Voice: +1 415 225 5579
"All that I will do, has been done, All that I have, has not."
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