// 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, const struct debug_el *ela, const 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)
{
        const 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 = get_random_u32_below(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_DESCRIPTION("list_sort() KUnit test suite");
MODULE_LICENSE("GPL");