Re: mapping user space buffer to kernel address space

From: Eric Lowe (
Date: Fri Oct 13 2000 - 07:20:23 EST


> On 13 Oct 00 at 15:31, wrote:
> > I have a user buffer and i want to map it to kernel address space
> > can anyone tell how to do this like in AIX we have xmattach
> Look at mm/memory.c:map_user_kiobuf. It is used by drivers/char/raw.c,
> or by drivers/media/video/bttv-driver.c, for example. It is 2.4 solution.
> For 2.2 solution, you have to
> (1) pagein page to memory (getuser(c, (char*)addr)),
> (2) walk pagetables (yourself, as p[gm]d_offset and pte_offset are 2.3 things),
> (3) increment page reference count (get_page(mem_map + pagenr))
> I believe that it is implemented by 2.2 drivers/char/bttv.c, and by
> vmware's vmmon module.

You can also apply the raw I/O patches to 2.2 and export the kiobuf
functions. I have a patch against 2.2.17 (with bugfixes), anyone who
needs it e-mail me and I'll send it along. This provides a *nearly*
compatible solution to 2.4, and it's much cleaner than driver-specific

Eric Lowe
Software Engineer, Systran Corporation

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