Re: [MiNT] memory protection on Afterburner04

[joska@nuts.edu (Jo Even Skarstein)]

On 1 May 99 11:06:39 +0000, Petr Stehlik wrote:

> thanks to Gryf and other FreeMiNT programmers I finally could see the
> MiNT running with memory protection. My usual KGMD setup booted OK
> (after disabling ST-Guide). Later it killed ZCONTROL and JCLKTOOL (I
> kinda liked that - a nice alert instead of TOS bombs, even if I didn´t
> know these two ACCs should have been ill).

I'm using memory-protection on my AB040 too, and it seems to work very
well indeed :-) I'm also using the very latest Thing-beta, it catches
VA-problems very nicely and helped me debug some problems. The following
programs had to have their memory set to READABLE:

TosWin 2.3
StringServer
URLserver
aMail
ST-Guide
ZControl

Other than that I haven't had any problems, except that Sweet Sixteen (2.73)
don't work, it freeze my Falcon when I try to play back a song. Does anyody
know of a multitasking-friendly, interrupt-driven SMF-player?

> Then I tried to play with some ´dirty´ programs like a HexEdit (direct
> memory editor). I was quite surprised I could edit memory at 0x8xx
> without any alert - why? The memory allocated before MiNT has started is
> not write protected? Probably not. This is still a weak place. But
> protecting such memory would require MiNT to learn where the screen
> memory is and where the cookies are etc. Probably too complicated?
> Is memory protection tied with User/Supervisor mode anyhow? Would it be
> possible to protect such low memory addresses in user mode only?

I don't know how desirable this is. Remember, all TSR's are loaded into
this area, and in many cases they install cookies with pointers to
structures in their own memory-space. This means that any program that
access these structures in user-mode (most do, just think about your own
Clocky...) will be killed.

> Later I started GemBench because the system seemed to be slower than
> usually. All but RAM/ROM tests went fine and showed that the memory

I also noticed this but I wonder if this can have anything to do with the
fact that I usually enable the copyback-cache after MiNT. Will the toolkit-
-driver work as usual with memory-protection enabled? If it doesn't, then I'm
running without copyback which means 20% slowdown...


/*
** Jo Even Skarstein    http://www.stud.ntnu.no/~josk/
**
**    beer - maria mckee - atari falcon - babylon 5
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