FreeBSD Memory Management questions ?

[John Baldwin]

On Sunday 19 June 2005 10:49 pm, Aziz Kezzou wrote:
> > On Tue, Jun 14, 2005 at 04:21:41AM -0400, Aziz Kezzou wrote:
> > > 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 ?
> >
> > Addition to the previous answer.  It is also possible to temporally
> > map several pages of user memory into the kernel address space.
> > Check pmap_qenter(9) and see physio -> vmapbuf, for example, how to
> > use it.  Another method, it is possible to COW a single user page and
> > then use it in the kernel, but with this method an user process will
> > not see any modification in this page made by the kernel and vice
> > versa. Check socow_setup -> vm_page_cowsetup, for example, how to
> > use it.
>
> Very interesting !
>
> Right now I am using the fact that the kernel address space is maped
> on i386 machines into the user address space. So when I am executing a
> system call I can access kernel memory.
> I am wondering if there is an architecture-independant way of doing
> that ? (Notice that I need not only read kernel memory but also free
> it. e.g, mbufs ) or at least could you tell me if that's  possible on
> other architectures ?

Are you modifying kernel memory from userland or are you trying to access user 
memory from kernel code?

-- 
John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org