lib: add CONFIG_TEST_SORT to enable self-test of sort()

Along with the addition made to Kconfig.debug, the prior existing but
permanently disabled test function has been slightly refactored.

Patch has been tested using QEMU 2.1.2 with a .config obtained through
'make defconfig' (x86_64) and manually enabling the option.

[arnd@arndb.de: move sort self-test into a separate file]
  Link: http://lkml.kernel.org/r/20170112110657.3123790-1-arnd@arndb.de
Link: http://lkml.kernel.org/r/HE1PR09MB0394B0418D504DCD27167D4FD49B0@HE1PR09MB0394.eurprd09.prod.outlook.com
Signed-off-by: Kostenzer Felix <fkostenzer@live.at>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 43 insertions, 0 deletions

diff --git a/lib/test_sort.c b/lib/test_sort.c
new file mode 100644
index 0000000000000..d389c1cc2f6cf
--- /dev/null
+++ b/lib/test_sort.c
@@ -0,0 +1,43 @@
+#include <linux/sort.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+
+/* a simple boot-time regression test */
+
+#define TEST_LEN 1000
+
+static int __init cmpint(const void *a, const void *b)
+{
+	return *(int *)a - *(int *)b;
+}
+
+static int __init test_sort_init(void)
+{
+	int *a, i, r = 1, err = -ENOMEM;
+
+	a = kmalloc_array(TEST_LEN, sizeof(*a), GFP_KERNEL);
+	if (!a)
+		return err;
+
+	for (i = 0; i < TEST_LEN; i++) {
+		r = (r * 725861) % 6599;
+		a[i] = r;
+	}
+
+	sort(a, TEST_LEN, sizeof(*a), cmpint, NULL);
+
+	err = -EINVAL;
+	for (i = 0; i < TEST_LEN-1; i++)
+		if (a[i] > a[i+1]) {
+			pr_err("test has failed\n");
+			goto exit;
+		}
+	err = 0;
+	pr_info("test passed\n");
+exit:
+	kfree(a);
+	return err;
+}
+
+module_init(test_sort_init);
+MODULE_LICENSE("GPL");