Index: head/sys/dev/efidev/efirt.c
===================================================================
--- head/sys/dev/efidev/efirt.c
+++ head/sys/dev/efidev/efirt.c
@@ -99,6 +99,25 @@
 
 static struct mtx efi_lock;
 
+static bool
+efi_is_in_map(struct efi_md *map, int ndesc, int descsz, vm_offset_t addr)
+{
+	struct efi_md *p;
+	int i;
+
+	for (i = 0, p = map; i < ndesc; i++, p = efi_next_descriptor(p,
+	    descsz)) {
+		if ((p->md_attr & EFI_MD_ATTR_RT) == 0)
+			continue;
+
+		if (addr >= (uintptr_t)p->md_virt &&
+		    addr < (uintptr_t)p->md_virt + p->md_pages * PAGE_SIZE)
+			return (true);
+	}
+
+	return (false);
+}
+
 static int
 efi_init(void)
 {
@@ -160,6 +179,24 @@
 	if (efi_runtime == NULL) {
 		if (bootverbose)
 			printf("EFI runtime services table is not present\n");
+		efi_destroy_1t1_map();
+		return (ENXIO);
+	}
+
+	/*
+	 * Some UEFI implementations have multiple implementations of the
+	 * RS->GetTime function. They switch from one we can only use early
+	 * in the boot process to one valid as a RunTime service only when we
+	 * call RS->SetVirtualAddressMap. As this is not always the case, e.g.
+	 * with an old loader.efi, check if the RS->GetTime function is within
+	 * the EFI map, and fail to attach if not.
+	 */
+	if (!efi_is_in_map(map, efihdr->memory_size / efihdr->descriptor_size,
+	    efihdr->descriptor_size, (vm_offset_t)efi_runtime->rt_gettime)) {
+		if (bootverbose)
+			printf(
+			 "EFI runtime services table has an invalid pointer\n");
+		efi_runtime = NULL;
 		efi_destroy_1t1_map();
 		return (ENXIO);
 	}