--- kernel/kern/zalloc.c	2018/04/24 18:26:07	1.1.1.1
+++ kernel/kern/zalloc.c	2018/04/24 18:32:12	1.1.1.2
@@ -84,9 +84,42 @@
 #include <vm/vm_kern.h>
 #endif
 
+#if DIAGNOSTIC
+vm_offset_t	zlowest = (vm_offset_t)(-1);
+vm_offset_t	zhighest = (vm_offset_t)0;
+#define WATERMARK_ZONE(zone, element)					\
+MACRO_BEGIN								\
+	if ((element) < (zone)->lowest)					\
+		(zone)->lowest = (element);				\
+		if ((element) < zlowest)				\
+			zlowest = (element);				\
+	if ((element) > (zone)->highest)				\
+		(zone)->highest = (element);				\
+		if ((element) > zhighest)				\
+			zhighest = (element);				\
+MACRO_END
+#else
+#define WATERMARK_ZONE(zone, element)
+#endif
+
+/*
+ * 1 - fill freed memory with 0xdeadface
+ * 2 - check_zone at zfree
+ * 4 - check_zone at zget
+ * 8 - check_zone at zalloc
+ * 10 - duplicate the free list pointer chain
+ */
+unsigned zone_check = 0;
+
+void *memset __P((void *, int , size_t));
+
 #define ADD_TO_ZONE(zone, element)					\
 MACRO_BEGIN								\
 	vm_offset_t	cur, *last;					\
+		if (zone_check & 1)					\
+                	(void) memset((void *)(element), 0xdeadface,	\
+                		      (size_t) (zone)->elem_size);	\
+		WATERMARK_ZONE((zone), (element));			\
 		if (		(zone)->last_insert != 0 	&&	\
 				(element) > (zone)->last_insert	)	\
 			(vm_offset_t)last = (zone)->last_insert;	\
@@ -96,6 +129,8 @@ MACRO_BEGIN								\
 				(element) > cur		)		\
 			(vm_offset_t)last = cur;			\
 		*(vm_offset_t *)(element) = cur;			\
+		if (zone_check & 0x10)					\
+			*((vm_offset_t *)(element) + 1) = cur;		\
 		*last = (element);					\
 		(zone)->last_insert = (element);			\
 		(zone)->count--;					\
@@ -652,6 +687,10 @@ zone_t zinit(size, max, alloc, pageable,
 	z->max_size = max;
 	z->elem_size = size;
 
+#if DIAGNOSTIC
+	z->lowest = (vm_offset_t)(-1);
+	z->highest = (vm_offset_t)0;
+#endif
 	z->alloc_size = alloc;
 	z->pageable = pageable;
 	z->zone_name = name;
@@ -1394,6 +1433,29 @@ void zone_init(void)
 				 zone_map_size, FALSE);
 }
 
+void
+check_zone(zone, elem)
+	zone_t	zone;
+	vm_offset_t	elem;
+{
+	vm_offset_t this;
+	/*
+	 * check the zone's consistency
+	 */
+#if !DIAGNOSTIC
+	if (!elem)
+		return;
+#endif
+	for (this = zone->free_elements;
+	     this != 0;
+	     this = * (vm_offset_t *) this)
+		if (this == elem)
+			panic("check_zone: argument already free");
+#if DIAGNOSTIC
+		else if (this < zone->lowest || this > zone->highest)
+			panic("check_zone: item out of range");
+#endif
+}
 
 /*
  *	zalloc returns an element from the specified zone.
@@ -1409,6 +1471,8 @@ vm_offset_t zalloc_canblock(zone, canblo
 		panic ("zalloc: null zone");
 
 	lock_zone(zone);
+	if (zone_check & 8)
+		check_zone(zone, 0);
 	REMOVE_FROM_ZONE(zone, addr, vm_offset_t);
 	while (addr == 0) {
 		/*
@@ -1473,6 +1537,8 @@ vm_offset_t zalloc_canblock(zone, canblo
 				/* XXX check before doing this */
 				thread_wakeup((event_t)&zone->doing_alloc);
 
+				if (zone_check & 8)
+					check_zone(zone, 0);
 				REMOVE_FROM_ZONE(zone, addr, vm_offset_t);
 			} else {
 				addr = zget_space(
@@ -1488,6 +1554,7 @@ vm_offset_t zalloc_canblock(zone, canblo
 				lock_zone(zone);
 				zone->count++;
 				zone->cur_size += zone->elem_size;
+				WATERMARK_ZONE(zone, addr);
 				unlock_zone(zone);
 				return(addr);
 			}
@@ -1527,30 +1594,26 @@ vm_offset_t zget(zone)
 		panic ("zalloc: null zone");
 
 	lock_zone(zone);
+	if (zone_check & 4)
+		check_zone(zone, 0);
 	REMOVE_FROM_ZONE(zone, addr, vm_offset_t);
 	unlock_zone(zone);
 
 	return(addr);
 }
 
-boolean_t zone_check = FALSE;
-
-void zfree(zone, elem)
+void
+zfree(zone, elem)
 	register zone_t	zone;
 	vm_offset_t	elem;
 {
 	lock_zone(zone);
-	if (zone_check) {
-		vm_offset_t this;
-
-		/* check the zone's consistency */
-
-		for (this = zone->free_elements;
-		     this != 0;
-		     this = * (vm_offset_t *) this)
-			if (this == elem)
-				panic("zfree");
-	}
+#if DIAGNOSTIC
+	if (elem < zone->lowest || elem > zone->highest)
+		panic("zfree: argument out of range");
+#endif
+	if (zone_check & 2)
+		check_zone(zone, elem);
 	ADD_TO_ZONE(zone, elem);
 	unlock_zone(zone);
 }