1 files changed, 13 insertions, 68 deletions

diff --git a/src/cmd/5g/gsubr.c b/src/cmd/5g/gsubr.c
index 6f0a072cc..481174b21 100644
--- a/src/cmd/5g/gsubr.c
+++ b/src/cmd/5g/gsubr.c
@@ -1189,48 +1189,6 @@ gregshift(int as, Node *lhs, int32 stype, Node *reg, Node *rhs)
 	return p;
 }
 
-// Generate an instruction referencing *n
-// to force segv on nil pointer dereference.
-void
-checkref(Node *n, int force)
-{
-	Node m1, m2;
-
-	if(!force && isptr[n->type->etype] && n->type->type->width < unmappedzero)
-		return;
-
-	regalloc(&m1, types[TUINTPTR], n);
-	regalloc(&m2, types[TUINT8], n);
-	cgen(n, &m1);
-	m1.xoffset = 0;
-	m1.op = OINDREG;
-	m1.type = types[TUINT8];
-	gins(AMOVB, &m1, &m2);
-	regfree(&m2);
-	regfree(&m1);
-}
-
-static void
-checkoffset(Addr *a, int canemitcode)
-{
-	Prog *p;
-	Node n1;
-
-	if(a->offset < unmappedzero)
-		return;
-	if(!canemitcode)
-		fatal("checkoffset %#x, cannot emit code", a->offset);
-
-	// cannot rely on unmapped nil page at 0 to catch
-	// reference with large offset.  instead, emit explicit
-	// test of 0(reg).
-	regalloc(&n1, types[TUINTPTR], N);
-	p = gins(AMOVB, N, &n1);
-	p->from = *a;
-	p->from.offset = 0;
-	regfree(&n1);
-}
-
 /*
  * generate code to compute n;
  * make a refer to result.
@@ -1294,7 +1252,6 @@ naddr(Node *n, Addr *a, int canemitcode)
 		a->reg = n->val.u.reg;
 		a->sym = n->sym;
 		a->offset = n->xoffset;
-		checkoffset(a, canemitcode);
 		break;
 
 	case OPARAM:
@@ -1402,8 +1359,6 @@ naddr(Node *n, Addr *a, int canemitcode)
 		a->etype = TINT32;
 		if(a->type == D_CONST && a->offset == 0)
 			break;	// len(nil)
-		if(a->offset >= unmappedzero && a->offset-Array_nel < unmappedzero)
-			checkoffset(a, canemitcode);
 		break;
 
 	case OLEN:
@@ -1413,8 +1368,6 @@ naddr(Node *n, Addr *a, int canemitcode)
 		if(a->type == D_CONST && a->offset == 0)
 			break;	// len(nil)
 		a->offset += Array_nel;
-		if(a->offset >= unmappedzero && a->offset-Array_nel < unmappedzero)
-			checkoffset(a, canemitcode);
 		break;
 
 	case OCAP:
@@ -1424,8 +1377,6 @@ naddr(Node *n, Addr *a, int canemitcode)
 		if(a->type == D_CONST && a->offset == 0)
 			break;	// cap(nil)
 		a->offset += Array_cap;
-		if(a->offset >= unmappedzero && a->offset-Array_cap < unmappedzero)
-			checkoffset(a, canemitcode);
 		break;
 
 	case OADDR:
@@ -1932,6 +1883,7 @@ odot:
 		n1.xoffset = oary[0];
 	} else {
 		cgen(nn, reg);
+		cgen_checknil(reg);
 		n1.xoffset = -(oary[0]+1);
 	}
 
@@ -1939,6 +1891,7 @@ odot:
 		if(oary[i] >= 0)
 			fatal("can't happen");
 		gins(AMOVW, &n1, reg);
+		cgen_checknil(reg);
 		n1.xoffset = -(oary[i]+1);
 	}
 
@@ -1986,9 +1939,10 @@ oindex:
 	// load the array (reg)
 	if(l->ullman > r->ullman) {
 		regalloc(reg, types[tptr], N);
-		if(o & OPtrto)
+		if(o & OPtrto) {
 			cgen(l, reg);
-		else
+			cgen_checknil(reg);
+		} else
 			agen(l, reg);
 	}
 
@@ -2005,9 +1959,10 @@ oindex:
 	// load the array (reg)
 	if(l->ullman <= r->ullman) {
 		regalloc(reg, types[tptr], N);
-		if(o & OPtrto)
+		if(o & OPtrto) {
 			cgen(l, reg);
-		else
+			cgen_checknil(reg);
+		} else
 			agen(l, reg);
 	}
 
@@ -2019,20 +1974,10 @@ oindex:
 			n2.type = types[tptr];
 			n2.xoffset = Array_nel;
 		} else {
-			if(l->type->width >= unmappedzero && l->op == OIND) {
-				// cannot rely on page protections to
-				// catch array ptr == 0, so dereference.
-				n2 = *reg;
-				n2.op = OINDREG;
-				n2.type = types[TUINTPTR];
-				n2.xoffset = 0;
-				regalloc(&n3, n2.type, N);
-				gins(AMOVW, &n2, &n3);
-				regfree(&n3);
-			}
-			nodconst(&n2, types[TUINT32], l->type->bound);
 			if(o & OPtrto)
 				nodconst(&n2, types[TUINT32], l->type->type->bound);
+			else
+				nodconst(&n2, types[TUINT32], l->type->bound);
 		}
 		regalloc(&n3, n2.type, N);
 		cgen(&n2, &n3);
@@ -2080,14 +2025,14 @@ oindex_const:
 	// can multiply by width statically
 
 	regalloc(reg, types[tptr], N);
-	if(o & OPtrto)
+	if(o & OPtrto) {
 		cgen(l, reg);
-	else
+		cgen_checknil(reg);
+	} else
 		agen(l, reg);
 
 	v = mpgetfix(r->val.u.xval);
 	if(o & ODynam) {
-
 		if(!debug['B'] && !n->bounded) {
 			n1 = *reg;
 			n1.op = OINDREG;