// SPDX-License-Identifier: GPL-2.0-only

  #include <kunit/test.h>

  
  #include <linux/kernel.h>
  #include <linux/list_sort.h>
  #include <linux/list.h>
  #include <linux/module.h>
  #include <linux/printk.h>
  #include <linux/slab.h>
  #include <linux/random.h>
  
  /*
   * 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 int serial;

  };

  static void check(struct kunit *test, struct debug_el *ela, struct debug_el *elb)

  {

  	struct debug_el **elts = test->priv;
  
  	KUNIT_EXPECT_LT_MSG(test, ela->serial, (unsigned int)TEST_LIST_LEN, "incorrect serial");
  	KUNIT_EXPECT_LT_MSG(test, elb->serial, (unsigned int)TEST_LIST_LEN, "incorrect serial");
  
  	KUNIT_EXPECT_PTR_EQ_MSG(test, elts[ela->serial], ela, "phantom element");
  	KUNIT_EXPECT_PTR_EQ_MSG(test, elts[elb->serial], elb, "phantom element");
  
  	KUNIT_EXPECT_EQ_MSG(test, ela->poison1, TEST_POISON1, "bad poison");
  	KUNIT_EXPECT_EQ_MSG(test, ela->poison2, TEST_POISON2, "bad poison");
  
  	KUNIT_EXPECT_EQ_MSG(test, elb->poison1, TEST_POISON1, "bad poison");
  	KUNIT_EXPECT_EQ_MSG(test, elb->poison2, TEST_POISON2, "bad poison");

  }

  /* `priv` is the test pointer so check() can fail the test if the list is invalid. */
  static int cmp(void *priv, const struct list_head *a, const 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(priv, ela, elb);

  	return ela->value - elb->value;
  }

  static void list_sort_test(struct kunit *test)

  {

  	int i, count = 1;
  	struct debug_el *el, **elts;

  	struct list_head *cur;
  	LIST_HEAD(head);

  	elts = kunit_kcalloc(test, TEST_LIST_LEN, sizeof(*elts), GFP_KERNEL);
  	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, elts);
  	test->priv = elts;

  
  	for (i = 0; i < TEST_LIST_LEN; i++) {

  		el = kunit_kmalloc(test, sizeof(*el), GFP_KERNEL);
  		KUNIT_ASSERT_NOT_ERR_OR_NULL(test, el);

  		 /* force some equivalencies */
  		el->value = prandom_u32() % (TEST_LIST_LEN / 3);
  		el->serial = i;
  		el->poison1 = TEST_POISON1;
  		el->poison2 = TEST_POISON2;
  		elts[i] = el;
  		list_add_tail(&el->list, &head);
  	}

  	list_sort(test, &head, cmp);

  	for (cur = head.next; cur->next != &head; cur = cur->next) {
  		struct debug_el *el1;
  		int cmp_result;

  		KUNIT_ASSERT_PTR_EQ_MSG(test, cur->next->prev, cur,
  					"list is corrupted");

  		cmp_result = cmp(test, cur, cur->next);
  		KUNIT_ASSERT_LE_MSG(test, cmp_result, 0, "list is not sorted");

  
  		el = container_of(cur, struct debug_el, list);
  		el1 = container_of(cur->next, struct debug_el, list);

  		if (cmp_result == 0) {
  			KUNIT_ASSERT_LE_MSG(test, el->serial, el1->serial,
  					    "order of equivalent elements not preserved");

  		}

  		check(test, el, el1);

  		count++;
  	}

  	KUNIT_EXPECT_PTR_EQ_MSG(test, head.prev, cur, "list is corrupted");

  	KUNIT_EXPECT_EQ_MSG(test, count, TEST_LIST_LEN,
  			    "list length changed after sorting!");
  }

  static struct kunit_case list_sort_cases[] = {
  	KUNIT_CASE(list_sort_test),
  	{}
  };
  
  static struct kunit_suite list_sort_suite = {
  	.name = "list_sort",
  	.test_cases = list_sort_cases,
  };
  
  kunit_test_suites(&list_sort_suite);

  MODULE_LICENSE("GPL");