From aa1d61a2dcc0e99b518fccd594990faceac1d762 Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Wed, 29 Dec 1993 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 1993-12-29

---
 carrera/dat.h       |  1 +
 carrera/faultmips.c |  2 ++
 carrera/trap.c      |  9 +++++++++
 pc/devvga.c         |  2 +-
 pc/l.s              | 31 +++++++++++++++++++++++++++++++
 5 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/carrera/dat.h b/carrera/dat.h
index 3bde0df8612eaaf282456d7bb4b312fc82f36cc3..cdcefaf6af2264c64f2bbeb24fbb286225d1160a 100644
--- a/carrera/dat.h
+++ b/carrera/dat.h
@@ -102,6 +102,7 @@ struct Mach
 	Label	sched;			/* scheduler wakeup */
 	int	lastpid;		/* last pid allocated on this machine */
 	Proc*	pidproc[NTLBPID];	/* proc that owns tlbpid on this mach */
+	ulong	vaddrtst;		/* address probe by tstbadvaddr */
 	Ureg*	ur;
 	KMap*	kactive;		/* active on this machine */
 	int	knext;
diff --git a/carrera/faultmips.c b/carrera/faultmips.c
index 3b83a962d958c35cc979c220fad2c42827b12284..7e4e85f784adf61d7017b19832352d887fc5882d 100644
--- a/carrera/faultmips.c
+++ b/carrera/faultmips.c
@@ -26,7 +26,9 @@ tstbadvaddr(Ureg *ur, int read)
 	if(seg(up, iw, 0) == 0)
 		return 0;
 
+	m->vaddrtst = iw;
 	iw = *(ulong*)iw;
+	m->vaddrtst = 0;
 
 /*	print("iw: %lux\n", iw);	/**/
 
diff --git a/carrera/trap.c b/carrera/trap.c
index cdadf9c6c3b80900b36bf5df589b4812a0a803f2..6de4c7ab0164b6f5a94439dd4dca8f88fd004b0f 100644
--- a/carrera/trap.c
+++ b/carrera/trap.c
@@ -172,6 +172,15 @@ trap(Ureg *ur)
 	int user, cop, x, fpchk;
 	char buf[2*ERRLEN], buf1[ERRLEN], *fpexcep;
 
+	/*
+	 * Retry failed probes of legal addresses from tstbadvaddr
+	 * workaround for the R4400 >2.3
+	 */
+	if(m->vaddrtst) {
+		m->vaddrtst = 0;
+		return;
+	}
+
 	ecode = (ur->cause>>2)&EXCMASK;
 	user = ur->status&KUSER;
 
diff --git a/pc/devvga.c b/pc/devvga.c
index 86f45cf4aee34734960ed2cb698ef18b2b0e3db9..1e2c61c9cdd17db9939a9dd8de20e0e5d3621749 100644
--- a/pc/devvga.c
+++ b/pc/devvga.c
@@ -608,7 +608,7 @@ screenupdate(void)
 	switch(gscreen.ldepth){
 	case 0:
 		r.min.x &= ~15;		/* 16 pixel alignment for l0update() */
-		f = memmove;
+		f = l0update;
 		len = (r.max.x + 7)/8 - r.min.x/8;
 		if(len & 1)
 			len++;		/* 16 bit alignment for l0update() */
diff --git a/pc/l.s b/pc/l.s
index 7c079a0ccfcdd878c34550c900837573234437d9..c0c53ffa83bff5feda3b8589ec758d658b88e096 100644
--- a/pc/l.s
+++ b/pc/l.s
@@ -617,6 +617,37 @@ TEXT	config(SB),$0
 #define	SR	0x3C5		/* sequence registers */
 #define Smmask	0x02		/*  map mask */
 
+/*
+ *  invert the ldepth 0 bitmap
+ */
+TEXT	l0update(SB),$0
+	MOVL	from+4(FP),SI
+	MOVL	to+0(FP),DI
+	MOVL	len+8(FP),BX
+
+	MOVL	BX,CX
+	SHRL	$2,CX
+	JZ	l01
+l00:
+	MOVL	-4(SI)(CX*4),AX
+	NOTL	AX
+	MOVL	AX,-4(DI)(CX*4)
+	LOOP	l00
+l01:
+	MOVL	BX,CX
+	ANDL	$(~3),BX
+	ANDL	$3,CX
+	JZ	l03
+	ADDL	BX,SI
+	ADDL	BX,DI
+l02:
+	MOVB	-1(SI)(CX*1),AL
+	NOTL	AX
+	MOVB	AL,-1(DI)(CX*1)
+	LOOP	l02
+l03:
+	RET
+
 /*
  *  separate ldepth 1 bitmap into 2 bit planes
  */