But then again, a PIII Xeon will do much more :)
On Wed, 7 Feb 2001, Stephen D. Cohen wrote:
>
>
> > -----Original Message-----
> > Todd Gearheart Wrote:
> > You can also "access" private data in kernel address space
> > from user mode
> > programs, by employing a simple trick. A user program can
> > request access to
> > a section of private kernel address space (via fifos, shared
> > memory, or
> > whatever). Then a kernel module can copy the requested
> > section of the kernel
> > private address space "needed in user space" into shared
> > memory. Then user
> > mode program can view/modify the shared memory area and
> > signal/indicate the
> > change(s) made. Finally the kernel module can take care of
> > "updating" the
> > changes back into the kernel private address space (from the
> > shared memory
> > area).
> >
> > I was able to implement a similar "swapping technique" in my simulator
> > application. It allows access to ALL kernel real-time storage
> > from the user
> > side as well...
>
> OK, lots of quoting to maintain the context...
>
> Of course, all of this can be done quite simply with RTL FIFOs. Why
> invent low-level mechanisms to complicate matters when a nice mechanism
> already exists? Then all you need to do is define your higher level
> protocols and synchronization and such.
>
> This also minimizes the number of tunnels from one world (RTL) to
> the other (Linux). Such tunnels are safety concerns as errant pointers and
> such cause unpredictable results (to say the least).
>
> The only reason I can think of to use mmap or statically mapped
> memory or any such is if you have a troughput requirement that exceeds what
> can be done with FIFOs. Of course, on my 400MHz Celeron the FIFOs will do
> more than 20MB per second...
>
> Regards,
>
> Steve
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