On 6/20/05, John Baldwin <[EMAIL PROTECTED]> wrote: > 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? >
I want to be able to modify BOTH user and kernel memory in kernel mode. Typically, a user process invoques a system call. While executing the system call I need to have r/w access to the calling process's memory (which is normally OK) and also r/w access to kernel's memory. Note : the user pages that are access from kernel mode are wired to avoid a page-fault inside the kernel, is that necessary ? Also is there a way of sharing part of the user memory space with the kernel. In a way that both have access to it and both see each others work (i.e, no copy-on-write ) ? Thanks, -aziz _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[EMAIL PROTECTED]"
