From 97a2e35a0c4a408285f2e94667f6ae069bb462e8 Mon Sep 17 00:00:00 2001
From: cinap_lenrek <cinap_lenrek@felloff.net>
Date: Sat, 8 Sep 2018 22:24:36 +0200
Subject: devarch: fix /dev/msr (thanks joe9, aiju)

the end condition port < offset+n could never become
false when offset truncated to 32 bit signed port is
negative. change the condition variables to unsigned
int.

msr's are not byte addressible, so advance reads by
one instead of 8.
---
 sys/src/9/pc/devarch.c | 50 +++++++++++++++++++++++++-------------------------
 1 file changed, 25 insertions(+), 25 deletions(-)

diff --git a/sys/src/9/pc/devarch.c b/sys/src/9/pc/devarch.c
index b7b0200ca..561e441ab 100644
--- a/sys/src/9/pc/devarch.c
+++ b/sys/src/9/pc/devarch.c
@@ -355,47 +355,47 @@ static long
 archread(Chan *c, void *a, long n, vlong offset)
 {
 	char buf[32], *p;
-	int port, i;
+	uint port, end;
+	int i;
 	ushort *sp;
 	ulong *lp;
 	vlong *vp;
 	IOMap *m;
 	Rdwrfn *fn;
 
+	port = offset;
+	end = port+n;
 	switch((ulong)c->qid.path){
 	case Qdir:
 		return devdirread(c, a, n, archdir, narchdir, devgen);
 
 	case Qiob:
-		port = offset;
-		checkport(offset, offset+n);
-		for(p = a; port < offset+n; port++)
+		checkport(port, end);
+		for(p = a; port < end; port++)
 			*p++ = inb(port);
 		return n;
 
 	case Qiow:
 		if(n & 1)
 			error(Ebadarg);
-		checkport(offset, offset+n);
-		sp = a;
-		for(port = offset; port < offset+n; port += 2)
+		checkport(port, end);
+		for(sp = a; port < end; port += 2)
 			*sp++ = ins(port);
 		return n;
 
 	case Qiol:
 		if(n & 3)
 			error(Ebadarg);
-		checkport(offset, offset+n);
-		lp = a;
-		for(port = offset; port < offset+n; port += 4)
+		checkport(port, end);
+		for(lp = a; port < end; port += 4)
 			*lp++ = inl(port);
 		return n;
 
 	case Qmsr:
 		if(n & 7)
 			error(Ebadarg);
-		vp = a;
-		for(port = offset; port < offset+n; port += 8)
+		end = port+(n/8);
+		for(vp = a; port < end; port++)
 			if(rdmsr(port, vp++) < 0)
 				error(Ebadarg);
 		return n;
@@ -404,7 +404,8 @@ archread(Chan *c, void *a, long n, vlong offset)
 		lock(&iomap);
 		i = 0;
 		for(m = iomap.m; m != nil; m = m->next){
-			i = snprint(buf, sizeof(buf), "%8lux %8lux %-12.12s\n", m->start, m->end-1, m->tag);
+			i = snprint(buf, sizeof(buf), "%8lux %8lux %-12.12s\n",
+				m->start, m->end-1, m->tag);
 			offset -= i;
 			if(offset < 0)
 				break;
@@ -429,44 +430,43 @@ archread(Chan *c, void *a, long n, vlong offset)
 static long
 archwrite(Chan *c, void *a, long n, vlong offset)
 {
+	uint port, end;
 	char *p;
-	int port;
 	ushort *sp;
 	ulong *lp;
 	vlong *vp;
 	Rdwrfn *fn;
 
+	port = offset;
+	end = port+n;
 	switch((ulong)c->qid.path){
 	case Qiob:
-		p = a;
-		checkport(offset, offset+n);
-		for(port = offset; port < offset+n; port++)
+		checkport(port, end);
+		for(p = a; port < end; port++)
 			outb(port, *p++);
 		return n;
 
 	case Qiow:
 		if(n & 1)
 			error(Ebadarg);
-		checkport(offset, offset+n);
-		sp = a;
-		for(port = offset; port < offset+n; port += 2)
+		checkport(port, end);
+		for(sp = a; port < end; port += 2)
 			outs(port, *sp++);
 		return n;
 
 	case Qiol:
 		if(n & 3)
 			error(Ebadarg);
-		checkport(offset, offset+n);
-		lp = a;
-		for(port = offset; port < offset+n; port += 4)
+		checkport(port, end);
+		for(lp = a; port < end; port += 4)
 			outl(port, *lp++);
 		return n;
 
 	case Qmsr:
 		if(n & 7)
 			error(Ebadarg);
-		vp = a;
-		for(port = offset; port < offset+n; port += 8)
+		end = port+(n/8);
+		for(vp = a; port < end; port++)
 			if(wrmsr(port, *vp++) < 0)
 				error(Ebadarg);
 		return n;
-- 
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