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ref: 62b3eea2715a9e67cdb0873faa0d802344bf7683
parent: 365fd745d62e9fdc43b22a0a1916c595749eb575
author: cinap_lenrek <[email protected]>
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);