fix bug in stack limit calculation - was setting limit reg in wrong place.

R=ken
OCL=14981
CL=14981

src/runtime/proc.c

@@ -463,8 +463,6 @@ oldstack(void)
 
 	top = (Stktop*)m->curg->stackbase;
 
-	m->curg->stackbase = top->oldbase;
-	m->curg->stackguard = top->oldguard;
 	siz2 = (top->magic>>32) & 0xffffLL;
 
 	sp = (byte*)top;
@@ -474,15 +472,12 @@ oldstack(void)
 		mcpy(top->oldsp+16, sp, siz2);
 	}
 
+	// call  no more functions after this point - limit register disagrees with R15
+	m->curg->stackbase = top->oldbase;
+	m->curg->stackguard = top->oldguard;
 	m->morestack.SP = top->oldsp+8;
 	m->morestack.PC = (byte*)(*(uint64*)(top->oldsp+8));
 
-// prints("oldstack sp=");
-// sys·printpointer(m->morestack.SP);
-// prints(" pc=");
-// sys·printpointer(m->morestack.PC);
-// prints("\n");
-
 	gogoret(&m->morestack, m->cret);
 }
 

src/runtime/sys_amd64_linux.s

@@ -81,6 +81,7 @@ TEXT	sigtramp(SB),7,$24-16
 
 TEXT	sys·mmap(SB),7,$0-32
 	MOVQ	8(SP), DI
+	MOVQ	$0, SI
 	MOVL	16(SP), SI
 	MOVL	20(SP), DX
 	MOVL	24(SP), R10
@@ -103,7 +104,7 @@ TEXT	sys·mmap(SB),7,$0-32
 	RET
 
 TEXT	notok(SB),7,$0
-	MOVL	$0xf1, BP
+	MOVQ	$0xf1, BP
 	MOVQ	BP, (BP)
 	RET