Mail Archives: djgpp/1999/10/07/20:57:28
Fokkema, DBRA, 1043730 wrote:
> I understand all this, but I thought it was nice if you could access all
> memory available. But if gnu cc doesn't support far pointers, and it is,
> as was suggested to me, just a flitch in the early intel processors, does
> this mean that dos c compilers are about the only ones that implement far
> pointers which they invented themselves (i.e. it is not part of the ansi-c
> standard)?
That's correct.
> : I wouldn't support it because I think there are other, better ways to
> : do things (quite apart from anything else, code that was written for
> : a segmented memory model is 100% ugly to port to any other hardware,
> : wheras if you are writing an OS, you can get all the same protection
> : benefits from paging systems which work a similar way on all hardware).
>
> How exactly do I get the same protection? By paging out all the memory
> belonging to other processes? How many platforms (and which) do support
> segmented memory models? I understand from your '100% ugly to port' statement
> that this aren't many.
Typically you have a separate set of page tables for each process, in
which only the pages belonging to that process are mapped.
And yes, there are very few other architectures that use a segmented
memory model. In fact, I can't think of any others.
--
Nate Eldredge
neldredge AT hmc DOT edu
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