Date: Sun, 19 Jun 2005 22:49:03 -0400 From: Aziz Kezzou <french.linuxian@gmail.com> To: Andrey Simonenko <simon@comsys.ntu-kpi.kiev.ua> Cc: freebsd-hackers <freebsd-hackers@freebsd.org> Subject: Re: FreeBSD Memory Management questions ? Message-ID: <3727392705061919494ea7e0ad@mail.gmail.com> In-Reply-To: <20050614120706.GA539@pm514-9.comsys.ntu-kpi.kiev.ua> References: <37273927050614012154fdb80b@mail.gmail.com> <20050614120706.GA539@pm514-9.comsys.ntu-kpi.kiev.ua>
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> 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 ? >=20 > 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 ? Thanks for your help, -aziz
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