vm: Assert that pagesizes[] is sorted

Ensure that pmap_init() properly initialized pagesizes[].  In part, we
are making this change to document the requirement that the non-zero
elements of pagesizes[] must be in ascending order.

Reviewed by:	kib, markj

sys/vm/vm_init.c

@@ -100,6 +100,24 @@ long physmem;
 static void vm_mem_init(void *);
 SYSINIT(vm_mem, SI_SUB_VM, SI_ORDER_FIRST, vm_mem_init, NULL);
 
+#ifdef INVARIANTS
+/*
+ * Ensure that pmap_init() correctly initialized pagesizes[].
+ */
+static void
+vm_check_pagesizes(void)
+{
+	int i;
+
+	KASSERT(pagesizes[0] == PAGE_SIZE, ("pagesizes[0] != PAGE_SIZE"));
+	for (i = 1; i < MAXPAGESIZES; i++) {
+		KASSERT((pagesizes[i - 1] != 0 &&
+		    pagesizes[i - 1] < pagesizes[i]) || pagesizes[i] == 0,
+		    ("pagesizes[%d ... %d] are misconfigured", i - 1, i));
+	}
+}
+#endif
+
 /*
  *	vm_mem_init() initializes the virtual memory system.
  *	This is done only by the first cpu up.
@@ -140,6 +158,10 @@ vm_mem_init(void *dummy)
 	kmem_init_zero_region();
 	pmap_init();
 	vm_pager_init();
+
+#ifdef INVARIANTS
+	vm_check_pagesizes();
+#endif
 }
 
 void