Date: Mon, 14 Nov 2005 16:12:49 -0800 From: John-Mark Gurney <gurney_j@resnet.uoregon.edu> To: John Giacomoni <John.Giacomoni@colorado.edu> Cc: freebsd-hackers@freebsd.org Subject: Re: Sharing the same VM address space between Kernel and UserSpace Message-ID: <20051115001249.GA79020@funkthat.com> In-Reply-To: <AA4AEE17-32CC-4D47-96C0-0B0B0BC13B68@colorado.edu> References: <AA4AEE17-32CC-4D47-96C0-0B0B0BC13B68@colorado.edu>
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John Giacomoni wrote this message on Mon, Nov 14, 2005 at 13:39 -0700:
> I am in need of a way to share memory between kernel space and possibly
> multiple different user-space processes for an extended period of time.
> This memory would need to be a single unpageable region.
>
> I am using the vm routines as cribbed from mmap, however I'd like the
> address spaces to be viewed as the same regardless of which process I'm
> in to avoid swizzling pointers as I'm storing data structures in the
> shared memory region.
>
> I imagine I'd need to find a way to expose part of the kernel address
> space to user space to accomplish this.
>
> Is there a way to do this?
Getting a common address between userland processes is easy, as you
can always just use fixed mappings using the MAP_FIXED flag to mmap..
Getting the same address will take some kernel vm magic, and also not
be very portable across platforms, since each platform may/can have a
different code address (though we try to keep them the same)...
--
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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