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
@@ -104,10 +104,10 @@
 
 #include <dev/smbios/smbios.h>
 
-_Static_assert(sizeof(struct pcb) == 1216, "struct pcb is incorrect size");
+_Static_assert(sizeof(struct pcb) == 1248, "struct pcb is incorrect size");
 _Static_assert(offsetof(struct pcb, pcb_fpusaved) == 136,
     "pcb_fpusaved changed offset");
-_Static_assert(offsetof(struct pcb, pcb_fpustate) == 160,
+_Static_assert(offsetof(struct pcb, pcb_fpustate) == 192,
     "pcb_fpustate changed offset");
 
 enum arm64_bus arm64_bus_method = ARM64_BUS_NONE;
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
@@ -67,7 +67,7 @@
 /* The bits passed to userspace in get_fpcontext */
 #define	PCB_FP_USERMASK	(PCB_FP_STARTED)
 	u_int		pcb_vfpcpu;	/* Last cpu this thread ran VFP code */
-	uint64_t	pcb_pad2;
+	uint64_t	pcb_reserved[5];
 
 	/*
 	 * The userspace VFP state. The pcb_fpusaved pointer will point to
diff --git a/sys/arm64/include/pmap.h b/sys/arm64/include/pmap.h
--- a/sys/arm64/include/pmap.h
+++ b/sys/arm64/include/pmap.h
@@ -95,6 +95,7 @@
 	struct asid_set		*pm_asid_set;	/* The ASID/VMID set to use */
 	enum pmap_stage		pm_stage;
 	int			pm_levels;
+	uint64_t		pm_reserved[4];
 };
 typedef struct pmap *pmap_t;
 
diff --git a/sys/arm64/include/proc.h b/sys/arm64/include/proc.h
--- a/sys/arm64/include/proc.h
+++ b/sys/arm64/include/proc.h
@@ -63,6 +63,8 @@
 	struct {
 		struct ptrauth_key apia;
 	} md_ptrauth_kern;
+
+	uint64_t md_reserved[4];
 };
 
 struct mdproc {