Re: [MiNT] Atari 030 patch for mmu030.S in current CVS

[Alan Hourihane <alanh@fairlite.demon.co.uk>]

On Mon, 2005-08-01 at 19:31 +0200, Konrad M. Kokoszkiewicz wrote:
> > I've found why FreeMiNT 1.16.x won't work on my TT, and below is a patch
> > to fix it.
> >
> > It seems that a pop from the stack had crept into the mmu030.S file.
> 
> This fix does not seem completely perfect at first glance. You rather have
> to restore the pop you deleted, and move the push to the very begin of the
> routine. Note that there are two branches to the label "normal_set", and
> both have to be inside the scope of the push/pop operation.
> 
> In other words, these lines in mmu030.S:
> 
> set_mmu:
>         tst.l   _offset_tt_ram
>         beq.s   normal_set
>         movem.l d0-d2/a0-a2,-(sp)
> 
> should look like this:
> 
> set_mmu:
>         movem.l d0-d2/a0-a2,-(sp)
>         tst.l   _offset_tt_ram
>         beq.s   normal_set
> 
> And this - and not deleting the pop - seems to fix the real bug we have in
> this procedure.

No, that's still not quite right either.

Below is the right fix taking into account the second branch to
"normal_set".

Because "normal_set" loads "crp" from the stack, which becomes corrupt
if we've already pushed it. We need to pop it before it reaches loading
of crp.

Attached is a better fix which should take care of the second call to
"normal_set" as well.

Alan.

Index: sys/arch/mmu030.S
===================================================================
RCS file: /mint/freemint/sys/arch/mmu030.S,v
retrieving revision 1.7
diff -u -r1.7 mmu030.S
--- sys/arch/mmu030.S	7 May 2005 08:58:16 -0000	1.7
+++ sys/arch/mmu030.S	1 Aug 2005 18:45:42 -0000
@@ -26,9 +26,9 @@
 	.globl	_sys_m_free
 
 _set_mmu:
+	movem.l	d0-d2/a0-a2,-(sp)
 	tst.l	_offset_tt_ram
 	beq.s	normal_set
-	movem.l	d0-d2/a0-a2,-(sp)
 	move.l	#end_set_mmu_called_st_ram - set_mmu_called_st_ram,d1
 	clr.w	-(sp)			// ST-ram
 	move.l	d1,-(sp)
@@ -66,13 +66,13 @@
 	movem.l	(sp)+,d0-d2/a0-a2
 	rts
 normal_set:
+	movem.l	(sp)+,d0-d2/a0-a2
 	pmove	(nulltc).l,tc		// turn off mmu
 	dc.l	0xf0390800,nulltc	// pmove nulltc,tt0
 	dc.l	0xf0390c00,nulltc	// pmove nulltc,tt1
 	pmove	4(sp),crp		// caution: crp is 8 bytes
 	pflusha
 	pmove	0xc(sp),tc
-	movem.l	(sp)+,d0-d2/a0-a2
 	rts
 
 set_mmu_called_st_ram: