lib/list_sort: test: check element addresses

Improve 'lib_sort()' test and check that:
o 'cmp()' is called only for elements which were present in the original list,
i.e., the 'a' and 'b' parameters are valid
o the resulted (sorted) list consists onlly of the original elements
o intdoruce "poison" fields to make sure data around 'struc list_head' field
are not corrupted.

Signed-off-by: Artem Bityutskiy <[e-mail]>
Cc: Don Mullis <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

lib/list_sort.c

···
 
 #include <linux/random.h>
 
-struct debug_el {
-	struct list_head list;
-	int value;
-	unsigned serial;
-};
-
-static int cmp(void *priv, struct list_head *a, struct list_head *b)
-{
-	return container_of(a, struct debug_el, list)->value
-	     - container_of(b, struct debug_el, list)->value;
-}
-
 /*
  * The pattern of set bits in the list length determines which cases
  * are hit in list_sort().
  */
 #define TEST_LIST_LEN (512+128+2) /* not including head */
+
+#define TEST_POISON1 0xDEADBEEF
+#define TEST_POISON2 0xA324354C
+
+struct debug_el {
+	unsigned int poison1;
+	struct list_head list;
+	unsigned int poison2;
+	int value;
+	unsigned serial;
+};
+
+/* Array, containing pointers to all elements in the test list */
+static struct debug_el **elts __initdata;
+
+static int __init check(struct debug_el *ela, struct debug_el *elb)
+{
+	if (ela->serial >= TEST_LIST_LEN) {
+		printk(KERN_ERR "list_sort_test: error: incorrect serial %d\n",
+				ela->serial);
+		return -EINVAL;
+	}
+	if (elb->serial >= TEST_LIST_LEN) {
+		printk(KERN_ERR "list_sort_test: error: incorrect serial %d\n",
+				elb->serial);
+		return -EINVAL;
+	}
+	if (elts[ela->serial] != ela || elts[elb->serial] != elb) {
+		printk(KERN_ERR "list_sort_test: error: phantom element\n");
+		return -EINVAL;
+	}
+	if (ela->poison1 != TEST_POISON1 || ela->poison2 != TEST_POISON2) {
+		printk(KERN_ERR "list_sort_test: error: bad poison: %#x/%#x\n",
+				ela->poison1, ela->poison2);
+		return -EINVAL;
+	}
+	if (elb->poison1 != TEST_POISON1 || elb->poison2 != TEST_POISON2) {
+		printk(KERN_ERR "list_sort_test: error: bad poison: %#x/%#x\n",
+				elb->poison1, elb->poison2);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static int __init cmp(void *priv, struct list_head *a, struct list_head *b)
+{
+	struct debug_el *ela, *elb;
+
+	ela = container_of(a, struct debug_el, list);
+	elb = container_of(b, struct debug_el, list);
+
+	check(ela, elb);
+	return ela->value - elb->value;
+}
 
 static int __init list_sort_test(void)
 {
···
 	LIST_HEAD(head);
 
 	printk(KERN_DEBUG "list_sort_test: start testing list_sort()\n");
+
+	elts = kmalloc(sizeof(void *) * TEST_LIST_LEN, GFP_KERNEL);
+	if (!elts) {
+		printk(KERN_ERR "list_sort_test: error: cannot allocate "
+				"memory\n");
+		goto exit;
+	}
 
 	for (i = 0; i < TEST_LIST_LEN; i++) {
 		el = kmalloc(sizeof(*el), GFP_KERNEL);
···
 		 /* force some equivalencies */
 		el->value = random32() % (TEST_LIST_LEN/3);
 		el->serial = i;
+		el->poison1 = TEST_POISON1;
+		el->poison2 = TEST_POISON2;
+		elts[i] = el;
 		list_add_tail(&el->list, &head);
 	}
 
···
 					"equivalent elements not preserved\n");
 			goto exit;
 		}
+
+		if (check(el, el1)) {
+			printk(KERN_ERR "list_sort_test: error: element check "
+					"failed\n");
+			goto exit;
+		}
 		count++;
 	}
 
···
 
 	err = 0;
 exit:
+	kfree(elts);
 	list_for_each_safe(cur, tmp, &head) {
 		list_del(cur);
 		kfree(container_of(cur, struct debug_el, list));