dupok, gcc compile fix, sync and syscall asm fix

R=rsc
APPROVED=rsc
DELTA=27  (18 added, 0 deleted, 9 changed)
OCL=35503
CL=35505

src/cmd/5l/l.h

@@ -123,6 +123,7 @@ struct	Sym
 	short	become;
 	short	frame;
 	uchar	subtype;
+	uchar	dupok;
 	uchar	reachable;
 	int32	value;
 	int32	sig;

src/cmd/5l/obj.c

@@ -564,6 +564,8 @@ loop:
 		}
 		if(p->to.offset > s->value)
 			s->value = p->to.offset;
+		if(p->reg & DUPOK)
+			s->dupok = 1;
 		break;
 
 	case ADYNT:
@@ -627,10 +629,15 @@ loop:
 		break;
 
 	case ADATA:
+		// Assume that AGLOBL comes after ADATA.
+		// If we've seen an AGLOBL that said this sym was DUPOK,
+		// ignore any more ADATA we see, which must be
+		// redefinitions.
 		s = p->from.sym;
-		if(s == S) {
-			diag("DATA without a sym\n%P", p);
-			break;
+		if(s != S && s->dupok) {
+			if(debug['v'])
+				Bprint(&bso, "skipping %s in %s: dupok\n", s->name, pn);
+			goto loop;
 		}
 		if(s != S) {
 			p->dlink = s->data;

src/cmd/ld/lib.c

@@ -561,10 +561,15 @@ find1(int32 l, int c)
 int
 find2(int32 l, int c)
 {
+	union {
+		int32 l;
+		short p[2];
+	} u;
 	short *p;
 	int i;
 
-	p = (short*)&l;
+	u.l = l;
+	p = u.p;
 	for(i=0; i<4; i+=2) {
 		if(((*p >> 8) & 0xff) == c)
 			return i;

src/pkg/syscall/asm_linux_arm.s

@@ -22,7 +22,8 @@ TEXT	syscall·Syscall(SB),7,$0
 	SWI		$SYS_syscall
 	MOVW	R0, 20(SP)	// r1
 	MOVW	R1, 24(SP)	// r2
-	MOVW	$0, 28(SP)	// errno
+	MOVW	$0, R0
+	MOVW	R0, 28(SP)	// errno
 	BL		sys·exitsyscall(SB)
 	RET
 
@@ -40,7 +41,8 @@ TEXT	syscall·Syscall6(SB),7,$0
 	SWI		$SYS_syscall
 	MOVW	R0, 32(SP)	// r1
 	MOVW	R1, 36(SP)	// r2
-	MOVW	$0, 40(SP)	// errno
+	MOVW	$0, R0
+	MOVW	R0, 40(SP)	// errno
 	BL		sys·exitsyscall(SB)
 	RET
 
@@ -53,5 +55,6 @@ TEXT syscall·RawSyscall(SB),7,$0
 	SWI		$SYS_syscall
 	MOVW	R0, 20(SP)	// r1
 	MOVW	R1, 24(SP)	// r2
-	MOVW	$0, 28(SP)	// errno
+	MOVW	$0, R0
+	MOVW	R0, 28(SP)	// errno
 	RET