--- researchv9/sys/sun3/trap.c	2018/04/24 17:21:59	1.1.1.1
+++ researchv9/sys/sun3/trap.c	2018/04/24 17:30:09	1.1.1.2
@@ -379,6 +379,7 @@ trap(type, regs, fmt)
 		goto out;
 
 	case T_BRKPT + USER:		/* bpt instruction (trap #15) fault */
+		locregs->r_pc = locregs->r_pc - 2;
 		u.u_code = TRAP_BKPT;
 		i = SIGTRAP;
 		break;