git: 9front

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ref: 8f63d48a00251d74b67e7244c908e436cb540d2c
parent: addcf037ca4dc1060318cfbd044f473ea594afe6
author: cinap_lenrek <cinap_lenrek@gmx.de>
date: Mon Sep 23 21:52:20 EDT 2013 

syssem*: eleminate redundant validaddr() checks

validaddr looks up the segments for an address range
and checks the flags and if the address range lies
within bounds on the segments.

as we'r going to lookup the segment in the syssem*
syscalls anyway, we can do the checks ourselfs avoiding
the double segment array lookups.

the implication of this tho is that now a semaphore cannot
span multiple segments. but this would be highly unusual
given that segments are page aligned.


--- a/sys/src/9/port/sysproc.c
+++ b/sys/src/9/port/sysproc.c
@@ -1109,13 +1109,15 @@
 	long *addr;
 	Segment *s;
 
-	validaddr(arg[0], sizeof(long), 1);
 	evenaddr(arg[0]);
 	addr = (long*)arg[0];
 	block = arg[1];
-	
-	if((s = seg(up, (ulong)addr, 0)) == nil)
+
+	s = seg(up, (ulong)addr, 0);
+	if(s == nil || (s->type&SG_RONLY) != 0 || (ulong)addr+sizeof(long) > s->top){
+		validaddr((ulong)addr, sizeof(long), 1);
 		error(Ebadarg);
+	}
 	if(*addr < 0)
 		error(Ebadarg);
 	return semacquire(s, addr, block);
@@ -1128,13 +1130,15 @@
 	ulong ms;
 	Segment *s;
 
-	validaddr(arg[0], sizeof(long), 1);
 	evenaddr(arg[0]);
 	addr = (long*)arg[0];
 	ms = arg[1];
 
-	if((s = seg(up, (ulong)addr, 0)) == nil)
+	s = seg(up, (ulong)addr, 0);
+	if(s == nil || (s->type&SG_RONLY) != 0 || (ulong)addr+sizeof(long) > s->top){
+		validaddr((ulong)addr, sizeof(long), 1);
 		error(Ebadarg);
+	}
 	if(*addr < 0)
 		error(Ebadarg);
 	return tsemacquire(s, addr, ms);
@@ -1146,13 +1150,15 @@
 	long *addr, delta;
 	Segment *s;
 
-	validaddr(arg[0], sizeof(long), 1);
 	evenaddr(arg[0]);
 	addr = (long*)arg[0];
 	delta = arg[1];
 
-	if((s = seg(up, (ulong)addr, 0)) == nil)
+	s = seg(up, (ulong)addr, 0);
+	if(s == nil || (s->type&SG_RONLY) != 0 || (ulong)addr+sizeof(long) > s->top){
+		validaddr((ulong)addr, sizeof(long), 1);
 		error(Ebadarg);
+	}
 	/* delta == 0 is a no-op, not a release */
 	if(delta < 0 || *addr < 0)
 		error(Ebadarg);
-- 
⑨