Index: sys/arch/arm/arm32/fault.c
===================================================================
RCS file: /cvsroot/src/sys/arch/arm/arm32/fault.c,v
retrieving revision 1.116
diff -u -p -r1.116 fault.c
--- sys/arch/arm/arm32/fault.c	1 Feb 2021 19:31:34 -0000	1.116
+++ sys/arch/arm/arm32/fault.c	7 Feb 2021 15:12:01 -0000
@@ -810,6 +810,10 @@ prefetch_abort_handler(trapframe_t *tf)
 	struct pcb *pcb __diagused;
 	struct vm_map *map;
 	vaddr_t fault_pc, va;
+	static struct last_fault {
+		pmap_t lf_pm;
+		vaddr_t lf_pc;
+	} lfs[MAXCPUS] __diagused;
 	ksiginfo_t ksi;
 	int error, user;
 
@@ -881,6 +885,16 @@ prefetch_abort_handler(trapframe_t *tf)
 		goto do_trapsignal;
 	}
 
+	/* Unaligned PCs are bad. */
+	if (__predict_false((fault_pc & 3) != 0)) {
+		KSI_INIT_TRAP(&ksi);
+		ksi.ksi_signo = SIGSEGV;
+		ksi.ksi_code = SEGV_ACCERR;
+		ksi.ksi_addr = (uint32_t *)(intptr_t) fault_pc;
+		ksi.ksi_trap = fault_pc;
+		goto do_trapsignal;
+	}
+
 	map = &l->l_proc->p_vmspace->vm_map;
 	va = trunc_page(fault_pc);
 
@@ -890,6 +904,11 @@ prefetch_abort_handler(trapframe_t *tf)
 #if defined(DEBUG) && !defined(MULTIPROCESSOR)
 	last_fault_code = -1;
 #endif
+	struct last_fault *lf = &lfs[cpu_index(curcpu())];
+	KASSERTMSG(map->pmap != lf->lf_pm || va != lf->lf_pc, "pmap %p va %lx", map->pmap, va);
+	lf->lf_pc = va;
+	lf->lf_pm = map->pmap;
+
 	if (pmap_fault_fixup(map->pmap, va, VM_PROT_READ|VM_PROT_EXECUTE, 1)) {
 		UVMHIST_LOG (maphist, " <- emulated", 0, 0, 0, 0);
 		goto out;