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Re: [MiNT] memory protection on Afterburner040



Hi!

On Sun, May 02, 1999 at 12:28:30AM +0000, Jo Even Skarstein wrote:
> A less complicated method would be to write-protect the TEXT-segment of
> the kernel. It's not nearly as effective as real write-protection, but
> a lot better than nothing.

But this could only protect parts of MiNT's TEXT segmen without a
deicated loader, because it may very likely start at - for example -
0x2001, which means the first 0x1fff byte couldn't be protected because
the segment doesn't begin on a page boundary (or otherwise, memory we
don't know of would be write-protected).

Additionally, MiNT's TPA has to be 8K-aligned, but as this can be easily
done by shrinking the BSS as needed, it's not a real problem.

> Btw. I've discovered one rather annoying side-effect of MP on my Afterburner:
> I can't reset anymore! Reset-button, keyboard, shutdown... Nothing works, I
> have to switch my Falcon off and on again.

Have you looked where _resvector points to (type of memory protection
there, can be determined by looking at the MMU dump created by either
Ctrl-Shift-Alt-F9 (-DDEBUG_INFO-kernel) or mmudump) and where 0x4 points
to? Is the VBR != 0?

What exactly happens when you try to reset per software, for example via

Supexec(Setexc(1, -1L));

or

Shutdown(1);

?


Ciao

Thomas


-- 
Thomas Binder (Gryf @ IRCNet)  gryf@hrzpub.tu-darmstadt.de
PGP-key available on request!  binder@rbg.informatik.tu-darmstadt.de

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