diff --git a/sys/arm64/arm64/db_trace.c b/sys/arm64/arm64/db_trace.c
--- a/sys/arm64/arm64/db_trace.c
+++ b/sys/arm64/arm64/db_trace.c
@@ -145,7 +145,7 @@
 		ctx = kdb_thr_ctx(thr);
 
 		frame.fp = (uintptr_t)ctx->pcb_x[PCB_FP];
-		frame.pc = (uintptr_t)ctx->pcb_lr;
+		frame.pc = (uintptr_t)ctx->pcb_x[PCB_LR];
 		db_stack_trace_cmd(thr, &frame);
 	} else
 		db_trace_self();
diff --git a/sys/arm64/arm64/gdb_machdep.c b/sys/arm64/arm64/gdb_machdep.c
--- a/sys/arm64/arm64/gdb_machdep.c
+++ b/sys/arm64/arm64/gdb_machdep.c
@@ -60,10 +60,10 @@
 	switch (regnum) {
 	case GDB_REG_SP: return (&kdb_thrctx->pcb_sp);
 	case GDB_REG_PC: /* FALLTHROUGH */
-	case GDB_REG_LR: return (&kdb_thrctx->pcb_lr);
+	case GDB_REG_LR: return (&kdb_thrctx->pcb_x[PCB_LR]);
 	default:
-		if (regnum >= GDB_REG_X0 && regnum <= GDB_REG_X29)
-			return (&kdb_thrctx->pcb_x[regnum]);
+		if (regnum >= GDB_REG_X19 && regnum <= GDB_REG_X29)
+			return (&kdb_thrctx->pcb_x[regnum - GDB_REG_X19]);
 		break;
 	}
 
@@ -89,11 +89,11 @@
 	}
 	switch (regnum) {
 	case GDB_REG_PC: /* FALLTHROUGH */
-	case GDB_REG_LR: kdb_thrctx->pcb_lr = regval; break;
+	case GDB_REG_LR: kdb_thrctx->pcb_x[PCB_LR] = regval; break;
 	case GDB_REG_SP: kdb_thrctx->pcb_sp = regval; break;
 	default:
-		if (regnum >= GDB_REG_X0 && regnum <= GDB_REG_X29) {
-			kdb_thrctx->pcb_x[regnum] = regval;
+		if (regnum >= GDB_REG_X19 && regnum <= GDB_REG_X29) {
+			kdb_thrctx->pcb_x[regnum - GDB_REG_X19] = regval;
 		}
 		break;
 	}
diff --git a/sys/arm64/arm64/genassym.c b/sys/arm64/arm64/genassym.c
--- a/sys/arm64/arm64/genassym.c
+++ b/sys/arm64/arm64/genassym.c
@@ -57,7 +57,6 @@
 ASSYM(PCB_SINGLE_STEP_SHIFT, PCB_SINGLE_STEP_SHIFT);
 ASSYM(PCB_REGS, offsetof(struct pcb, pcb_x));
 ASSYM(PCB_X19, PCB_X19);
-ASSYM(PCB_LR, offsetof(struct pcb, pcb_lr));
 ASSYM(PCB_SP, offsetof(struct pcb, pcb_sp));
 ASSYM(PCB_TPIDRRO, offsetof(struct pcb, pcb_tpidrro_el0));
 ASSYM(PCB_ONFAULT, offsetof(struct pcb, pcb_onfault));
diff --git a/sys/arm64/arm64/machdep.c b/sys/arm64/arm64/machdep.c
--- a/sys/arm64/arm64/machdep.c
+++ b/sys/arm64/arm64/machdep.c
@@ -356,10 +356,10 @@
 	int i;
 
 	for (i = 0; i < nitems(pcb->pcb_x); i++)
-		pcb->pcb_x[i] = tf->tf_x[i];
+		pcb->pcb_x[i] = tf->tf_x[i + PCB_X_START];
 
-	/* NB: pcb_lr is the PC, see PC_REGS() in db_machdep.h */
-	pcb->pcb_lr = tf->tf_elr;
+	/* NB: pcb_x[PCB_LR] is the PC, see PC_REGS() in db_machdep.h */
+	pcb->pcb_x[PCB_LR] = tf->tf_elr;
 	pcb->pcb_sp = tf->tf_sp;
 }
 
diff --git a/sys/arm64/arm64/stack_machdep.c b/sys/arm64/arm64/stack_machdep.c
--- a/sys/arm64/arm64/stack_machdep.c
+++ b/sys/arm64/arm64/stack_machdep.c
@@ -69,7 +69,7 @@
 		return (EOPNOTSUPP);
 
 	frame.fp = td->td_pcb->pcb_x[PCB_FP];
-	frame.pc = ADDR_MAKE_CANONICAL(td->td_pcb->pcb_lr);
+	frame.pc = ADDR_MAKE_CANONICAL(td->td_pcb->pcb_x[PCB_LR]);
 
 	stack_capture(td, st, &frame);
 	return (0);
diff --git a/sys/arm64/arm64/vm_machdep.c b/sys/arm64/arm64/vm_machdep.c
--- a/sys/arm64/arm64/vm_machdep.c
+++ b/sys/arm64/arm64/vm_machdep.c
@@ -107,7 +107,7 @@
 	/* Set the return value registers for fork() */
 	td2->td_pcb->pcb_x[PCB_X19] = (uintptr_t)fork_return;
 	td2->td_pcb->pcb_x[PCB_X20] = (uintptr_t)td2;
-	td2->td_pcb->pcb_lr = (uintptr_t)fork_trampoline;
+	td2->td_pcb->pcb_x[PCB_LR] = (uintptr_t)fork_trampoline;
 	td2->td_pcb->pcb_sp = (uintptr_t)td2->td_frame;
 
 	vfp_new_thread(td2, td1, true);
@@ -185,7 +185,7 @@
 
 	td->td_pcb->pcb_x[PCB_X19] = (uintptr_t)fork_return;
 	td->td_pcb->pcb_x[PCB_X20] = (uintptr_t)td;
-	td->td_pcb->pcb_lr = (uintptr_t)fork_trampoline;
+	td->td_pcb->pcb_x[PCB_LR] = (uintptr_t)fork_trampoline;
 	td->td_pcb->pcb_sp = (uintptr_t)td->td_frame;
 
 	/* Update VFP state for the new thread */
diff --git a/sys/arm64/include/db_machdep.h b/sys/arm64/include/db_machdep.h
--- a/sys/arm64/include/db_machdep.h
+++ b/sys/arm64/include/db_machdep.h
@@ -44,7 +44,7 @@
 typedef vm_offset_t	db_addr_t;
 typedef long		db_expr_t;
 
-#define	PC_REGS()	((db_addr_t)kdb_thrctx->pcb_lr)
+#define	PC_REGS()	((db_addr_t)kdb_thrctx->pcb_x[PCB_LR])
 
 #define	BKPT_INST	(0xd4200000)
 #define	BKPT_SIZE	(4)
@@ -52,7 +52,7 @@
 
 #define	BKPT_SKIP do {				\
 	kdb_frame->tf_elr += BKPT_SIZE;		\
-	kdb_thrctx->pcb_lr += BKPT_SIZE;	\
+	kdb_thrctx->pcb_x[PCB_LR] += BKPT_SIZE;	\
 } while (0)
 
 #define	db_clear_single_step	kdb_cpu_clear_singlestep
diff --git a/sys/arm64/include/gdb_machdep.h b/sys/arm64/include/gdb_machdep.h
--- a/sys/arm64/include/gdb_machdep.h
+++ b/sys/arm64/include/gdb_machdep.h
@@ -34,6 +34,7 @@
 #define	GDB_BUFSZ	4096
 #define	GDB_NREGS	68
 #define	GDB_REG_X0	0
+#define	GDB_REG_X19	19
 #define	GDB_REG_X29	29
 #define	GDB_REG_LR	30
 #define	GDB_REG_SP	31
diff --git a/sys/arm64/include/pcb.h b/sys/arm64/include/pcb.h
--- a/sys/arm64/include/pcb.h
+++ b/sys/arm64/include/pcb.h
@@ -36,14 +36,16 @@
 
 struct trapframe;
 
-#define	PCB_X19		19
-#define	PCB_X20		20
-#define	PCB_FP		29
+/* The first register in pcb_x is x19 */
+#define	PCB_X_START	19
+
+#define	PCB_X19		0
+#define	PCB_X20		1
+#define	PCB_FP		10
+#define	PCB_LR		11
 
 struct pcb {
-	uint64_t	pcb_x[30];
-	uint64_t	pcb_lr;
-	uint64_t	_reserved;	/* Was pcb_pc */
+	uint64_t	pcb_x[12];
 	/* These two need to be in order as we access them together */
 	uint64_t	pcb_sp;
 	uint64_t	pcb_tpidr_el0;