* [PATCH v4 2/2] char: misc: add test cases
2025-04-23 8:45 [PATCH v4 0/2] char: misc: improve test and dynamic allocation Thadeu Lima de Souza Cascardo
2025-04-23 8:45 ` [PATCH v4 1/2] char: misc: restrict the dynamic range to exclude reserved minors Thadeu Lima de Souza Cascardo
@ 2025-04-23 8:45 ` Thadeu Lima de Souza Cascardo
1 sibling, 0 replies; 3+ messages in thread
From: Thadeu Lima de Souza Cascardo @ 2025-04-23 8:45 UTC (permalink / raw)
To: Arnd Bergmann, Greg Kroah-Hartman
Cc: Andrew Morton, Dirk VanDerMerwe, Vimal Agrawal, linux-kernel,
Thadeu Lima de Souza Cascardo, kernel-dev
Add test cases for static and dynamic minor number allocation and
deallocation.
While at it, improve description and test suite name.
Some of the cases include:
- that static and dynamic allocation reserved the expected minors.
- that registering duplicate minors or duplicate names will fail.
- that failing to create a sysfs file (due to duplicate names) will
deallocate the dynamic minor correctly.
- that dynamic allocation does not allocate a minor number in the static
range.
- that there are no collisions when mixing dynamic and static allocations.
- that opening devices with various minor device numbers work.
- that registering a static number in the dynamic range won't conflict with
a dynamic allocation.
This last test verifies the bug fixed by commit 6d04d2b554b1 ("misc:
misc_minor_alloc to use ida for all dynamic/misc dynamic minors") has not
regressed.
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
---
drivers/misc/misc_minor_kunit.c | 589 +++++++++++++++++++++++++++++++++++++++-
1 file changed, 587 insertions(+), 2 deletions(-)
diff --git a/drivers/misc/misc_minor_kunit.c b/drivers/misc/misc_minor_kunit.c
index 293e0fb7e43edc330842722e1132d16cd23e3aa8..30eceac5f1b6402b0f918af6f56602ed1a6c14ec 100644
--- a/drivers/misc/misc_minor_kunit.c
+++ b/drivers/misc/misc_minor_kunit.c
@@ -3,6 +3,9 @@
#include <kunit/test-bug.h>
#include <linux/module.h>
#include <linux/miscdevice.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/init_syscalls.h>
/* dynamic minor (2) */
static struct miscdevice dev_dynamic_minor = {
@@ -51,19 +54,601 @@ static void kunit_misc_dynamic_minor(struct kunit *test)
misc_deregister(&dev_misc_dynamic_minor);
}
+struct miscdev_test_case {
+ const char *str;
+ int minor;
+};
+
+static struct miscdev_test_case miscdev_test_ranges[] = {
+ {
+ .str = "lower static range, top",
+ .minor = 15,
+ },
+ {
+ .str = "upper static range, bottom",
+ .minor = 130,
+ },
+ {
+ .str = "lower static range, bottom",
+ .minor = 0,
+ },
+ {
+ .str = "upper static range, top",
+ .minor = MISC_DYNAMIC_MINOR - 1,
+ },
+};
+
+KUNIT_ARRAY_PARAM_DESC(miscdev, miscdev_test_ranges, str);
+
+static int miscdev_find_minors(struct kunit_suite *suite)
+{
+ int ret;
+ struct miscdevice miscstat = {
+ .name = "miscstat",
+ };
+ int i;
+
+ for (i = 15; i >= 0; i--) {
+ miscstat.minor = i;
+ ret = misc_register(&miscstat);
+ if (ret == 0)
+ break;
+ }
+
+ if (ret == 0) {
+ kunit_info(suite, "found misc device minor %d available\n",
+ miscstat.minor);
+ miscdev_test_ranges[0].minor = miscstat.minor;
+ misc_deregister(&miscstat);
+ } else {
+ return ret;
+ }
+
+ for (i = 128; i < MISC_DYNAMIC_MINOR; i++) {
+ miscstat.minor = i;
+ ret = misc_register(&miscstat);
+ if (ret == 0)
+ break;
+ }
+
+ if (ret == 0) {
+ kunit_info(suite, "found misc device minor %d available\n",
+ miscstat.minor);
+ miscdev_test_ranges[1].minor = miscstat.minor;
+ misc_deregister(&miscstat);
+ } else {
+ return ret;
+ }
+
+ for (i = 0; i < miscdev_test_ranges[0].minor; i++) {
+ miscstat.minor = i;
+ ret = misc_register(&miscstat);
+ if (ret == 0)
+ break;
+ }
+
+ if (ret == 0) {
+ kunit_info(suite, "found misc device minor %d available\n",
+ miscstat.minor);
+ miscdev_test_ranges[2].minor = miscstat.minor;
+ misc_deregister(&miscstat);
+ } else {
+ return ret;
+ }
+
+ for (i = MISC_DYNAMIC_MINOR - 1; i > miscdev_test_ranges[1].minor; i--) {
+ miscstat.minor = i;
+ ret = misc_register(&miscstat);
+ if (ret == 0)
+ break;
+ }
+
+ if (ret == 0) {
+ kunit_info(suite, "found misc device minor %d available\n",
+ miscstat.minor);
+ miscdev_test_ranges[3].minor = miscstat.minor;
+ misc_deregister(&miscstat);
+ }
+
+ return ret;
+}
+
+static bool is_valid_dynamic_minor(int minor)
+{
+ if (minor < 0)
+ return false;
+ if (minor == MISC_DYNAMIC_MINOR)
+ return false;
+ if (minor >= 0 && minor <= 15)
+ return false;
+ if (minor >= 128 && minor < MISC_DYNAMIC_MINOR)
+ return false;
+ return true;
+}
+
+static int miscdev_test_open(struct inode *inode, struct file *file)
+{
+ return 0;
+}
+
+static const struct file_operations miscdev_test_fops = {
+ .open = miscdev_test_open,
+};
+
+static void __init miscdev_test_can_open(struct kunit *test, struct miscdevice *misc)
+{
+ int ret;
+ struct file *filp;
+ char *devname;
+
+ devname = kasprintf(GFP_KERNEL, "/dev/%s", misc->name);
+ ret = init_mknod(devname, S_IFCHR | 0600,
+ new_encode_dev(MKDEV(MISC_MAJOR, misc->minor)));
+ if (ret != 0)
+ KUNIT_FAIL(test, "failed to create node\n");
+
+ filp = filp_open(devname, O_RDONLY, 0);
+ if (IS_ERR_OR_NULL(filp))
+ KUNIT_FAIL(test, "failed to open misc device: %ld\n", PTR_ERR(filp));
+ else
+ fput(filp);
+
+ init_unlink(devname);
+ kfree(devname);
+}
+
+static void __init miscdev_test_static_basic(struct kunit *test)
+{
+ struct miscdevice misc_test = {
+ .name = "misc_test",
+ .fops = &miscdev_test_fops,
+ };
+ int ret;
+ const struct miscdev_test_case *params = test->param_value;
+
+ misc_test.minor = params->minor;
+
+ ret = misc_register(&misc_test);
+ KUNIT_EXPECT_EQ(test, ret, 0);
+ KUNIT_EXPECT_EQ(test, misc_test.minor, params->minor);
+
+ if (ret == 0) {
+ miscdev_test_can_open(test, &misc_test);
+ misc_deregister(&misc_test);
+ }
+}
+
+static void __init miscdev_test_dynamic_basic(struct kunit *test)
+{
+ struct miscdevice misc_test = {
+ .minor = MISC_DYNAMIC_MINOR,
+ .name = "misc_test",
+ .fops = &miscdev_test_fops,
+ };
+ int ret;
+
+ ret = misc_register(&misc_test);
+ KUNIT_EXPECT_EQ(test, ret, 0);
+ KUNIT_EXPECT_TRUE(test, is_valid_dynamic_minor(misc_test.minor));
+
+ if (ret == 0) {
+ miscdev_test_can_open(test, &misc_test);
+ misc_deregister(&misc_test);
+ }
+}
+
+static void miscdev_test_twice(struct kunit *test)
+{
+ struct miscdevice misc_test = {
+ .name = "misc_test",
+ .fops = &miscdev_test_fops,
+ };
+ int ret;
+ const struct miscdev_test_case *params = test->param_value;
+
+ misc_test.minor = params->minor;
+
+ ret = misc_register(&misc_test);
+ KUNIT_EXPECT_EQ(test, ret, 0);
+ KUNIT_EXPECT_EQ(test, misc_test.minor, params->minor);
+ if (ret == 0)
+ misc_deregister(&misc_test);
+
+ ret = misc_register(&misc_test);
+ KUNIT_EXPECT_EQ(test, ret, 0);
+ KUNIT_EXPECT_EQ(test, misc_test.minor, params->minor);
+ if (ret == 0)
+ misc_deregister(&misc_test);
+}
+
+static void miscdev_test_duplicate_minor(struct kunit *test)
+{
+ struct miscdevice misc1 = {
+ .name = "misc1",
+ .fops = &miscdev_test_fops,
+ };
+ struct miscdevice misc2 = {
+ .name = "misc2",
+ .fops = &miscdev_test_fops,
+ };
+ int ret;
+ const struct miscdev_test_case *params = test->param_value;
+
+ misc1.minor = params->minor;
+ misc2.minor = params->minor;
+
+ ret = misc_register(&misc1);
+ KUNIT_EXPECT_EQ(test, ret, 0);
+ KUNIT_EXPECT_EQ(test, misc1.minor, params->minor);
+
+ ret = misc_register(&misc2);
+ KUNIT_EXPECT_EQ(test, ret, -EBUSY);
+ if (ret == 0)
+ misc_deregister(&misc2);
+
+ misc_deregister(&misc1);
+}
+
+static void miscdev_test_duplicate_name(struct kunit *test)
+{
+ struct miscdevice misc1 = {
+ .minor = MISC_DYNAMIC_MINOR,
+ .name = "misc1",
+ .fops = &miscdev_test_fops,
+ };
+ struct miscdevice misc2 = {
+ .minor = MISC_DYNAMIC_MINOR,
+ .name = "misc1",
+ .fops = &miscdev_test_fops,
+ };
+ int ret;
+
+ ret = misc_register(&misc1);
+ KUNIT_EXPECT_EQ(test, ret, 0);
+ KUNIT_EXPECT_TRUE(test, is_valid_dynamic_minor(misc1.minor));
+
+ ret = misc_register(&misc2);
+ KUNIT_EXPECT_EQ(test, ret, -EEXIST);
+ if (ret == 0)
+ misc_deregister(&misc2);
+
+ misc_deregister(&misc1);
+}
+
+/*
+ * Test that after a duplicate name failure, the reserved minor number is
+ * freed to be allocated next.
+ */
+static void miscdev_test_duplicate_name_leak(struct kunit *test)
+{
+ struct miscdevice misc1 = {
+ .minor = MISC_DYNAMIC_MINOR,
+ .name = "misc1",
+ .fops = &miscdev_test_fops,
+ };
+ struct miscdevice misc2 = {
+ .minor = MISC_DYNAMIC_MINOR,
+ .name = "misc1",
+ .fops = &miscdev_test_fops,
+ };
+ struct miscdevice misc3 = {
+ .minor = MISC_DYNAMIC_MINOR,
+ .name = "misc3",
+ .fops = &miscdev_test_fops,
+ };
+ int ret;
+ int dyn_minor;
+
+ ret = misc_register(&misc1);
+ KUNIT_EXPECT_EQ(test, ret, 0);
+ KUNIT_EXPECT_TRUE(test, is_valid_dynamic_minor(misc1.minor));
+
+ /*
+ * Find out what is the next minor number available.
+ */
+ ret = misc_register(&misc3);
+ KUNIT_EXPECT_EQ(test, ret, 0);
+ KUNIT_EXPECT_TRUE(test, is_valid_dynamic_minor(misc3.minor));
+ dyn_minor = misc3.minor;
+ misc_deregister(&misc3);
+ misc3.minor = MISC_DYNAMIC_MINOR;
+
+ ret = misc_register(&misc2);
+ KUNIT_EXPECT_EQ(test, ret, -EEXIST);
+ if (ret == 0)
+ misc_deregister(&misc2);
+
+ /*
+ * Now check that we can still get the same minor we found before.
+ */
+ ret = misc_register(&misc3);
+ KUNIT_EXPECT_EQ(test, ret, 0);
+ KUNIT_EXPECT_TRUE(test, is_valid_dynamic_minor(misc3.minor));
+ KUNIT_EXPECT_EQ(test, misc3.minor, dyn_minor);
+ misc_deregister(&misc3);
+
+ misc_deregister(&misc1);
+}
+
+/*
+ * Try to register a static minor with a duplicate name. That might not
+ * deallocate the minor, preventing it from being used again.
+ */
+static void miscdev_test_duplicate_error(struct kunit *test)
+{
+ struct miscdevice miscdyn = {
+ .minor = MISC_DYNAMIC_MINOR,
+ .name = "name1",
+ .fops = &miscdev_test_fops,
+ };
+ struct miscdevice miscstat = {
+ .name = "name1",
+ .fops = &miscdev_test_fops,
+ };
+ struct miscdevice miscnew = {
+ .name = "name2",
+ .fops = &miscdev_test_fops,
+ };
+ int ret;
+ const struct miscdev_test_case *params = test->param_value;
+
+ miscstat.minor = params->minor;
+ miscnew.minor = params->minor;
+
+ ret = misc_register(&miscdyn);
+ KUNIT_EXPECT_EQ(test, ret, 0);
+ KUNIT_EXPECT_TRUE(test, is_valid_dynamic_minor(miscdyn.minor));
+
+ ret = misc_register(&miscstat);
+ KUNIT_EXPECT_EQ(test, ret, -EEXIST);
+ if (ret == 0)
+ misc_deregister(&miscstat);
+
+ ret = misc_register(&miscnew);
+ KUNIT_EXPECT_EQ(test, ret, 0);
+ KUNIT_EXPECT_EQ(test, miscnew.minor, params->minor);
+ if (ret == 0)
+ misc_deregister(&miscnew);
+
+ misc_deregister(&miscdyn);
+}
+
+static void __init miscdev_test_dynamic_only_range(struct kunit *test)
+{
+ int ret;
+ struct miscdevice *miscdev;
+ const int dynamic_minors = 256;
+ int i;
+
+ miscdev = kunit_kmalloc_array(test, dynamic_minors,
+ sizeof(struct miscdevice),
+ GFP_KERNEL | __GFP_ZERO);
+
+ for (i = 0; i < dynamic_minors; i++) {
+ miscdev[i].minor = MISC_DYNAMIC_MINOR;
+ miscdev[i].name = kasprintf(GFP_KERNEL, "misc_test%d", i);
+ miscdev[i].fops = &miscdev_test_fops;
+ ret = misc_register(&miscdev[i]);
+ if (ret != 0)
+ break;
+ /*
+ * This is the bug we are looking for!
+ * We asked for a dynamic minor and got a minor in the static range space.
+ */
+ if (miscdev[i].minor >= 0 && miscdev[i].minor <= 15) {
+ KUNIT_FAIL(test, "misc_register allocated minor %d\n", miscdev[i].minor);
+ i++;
+ break;
+ }
+ KUNIT_EXPECT_TRUE(test, is_valid_dynamic_minor(miscdev[i].minor));
+ }
+
+ for (i--; i >= 0; i--) {
+ miscdev_test_can_open(test, &miscdev[i]);
+ misc_deregister(&miscdev[i]);
+ kfree_const(miscdev[i].name);
+ }
+
+ KUNIT_EXPECT_EQ(test, ret, 0);
+}
+
+static void __init miscdev_test_collision(struct kunit *test)
+{
+ int ret;
+ struct miscdevice *miscdev;
+ struct miscdevice miscstat = {
+ .name = "miscstat",
+ .fops = &miscdev_test_fops,
+ };
+ const int dynamic_minors = 256;
+ int i;
+
+ miscdev = kunit_kmalloc_array(test, dynamic_minors,
+ sizeof(struct miscdevice),
+ GFP_KERNEL | __GFP_ZERO);
+
+ miscstat.minor = miscdev_test_ranges[0].minor;
+ ret = misc_register(&miscstat);
+ KUNIT_ASSERT_EQ(test, ret, 0);
+ KUNIT_EXPECT_EQ(test, miscstat.minor, miscdev_test_ranges[0].minor);
+
+ for (i = 0; i < dynamic_minors; i++) {
+ miscdev[i].minor = MISC_DYNAMIC_MINOR;
+ miscdev[i].name = kasprintf(GFP_KERNEL, "misc_test%d", i);
+ miscdev[i].fops = &miscdev_test_fops;
+ ret = misc_register(&miscdev[i]);
+ if (ret != 0)
+ break;
+ KUNIT_EXPECT_TRUE(test, is_valid_dynamic_minor(miscdev[i].minor));
+ }
+
+ for (i--; i >= 0; i--) {
+ miscdev_test_can_open(test, &miscdev[i]);
+ misc_deregister(&miscdev[i]);
+ kfree_const(miscdev[i].name);
+ }
+
+ misc_deregister(&miscstat);
+
+ KUNIT_EXPECT_EQ(test, ret, 0);
+}
+
+static void __init miscdev_test_collision_reverse(struct kunit *test)
+{
+ int ret;
+ struct miscdevice *miscdev;
+ struct miscdevice miscstat = {
+ .name = "miscstat",
+ .fops = &miscdev_test_fops,
+ };
+ const int dynamic_minors = 256;
+ int i;
+
+ miscdev = kunit_kmalloc_array(test, dynamic_minors,
+ sizeof(struct miscdevice),
+ GFP_KERNEL | __GFP_ZERO);
+
+ for (i = 0; i < dynamic_minors; i++) {
+ miscdev[i].minor = MISC_DYNAMIC_MINOR;
+ miscdev[i].name = kasprintf(GFP_KERNEL, "misc_test%d", i);
+ miscdev[i].fops = &miscdev_test_fops;
+ ret = misc_register(&miscdev[i]);
+ if (ret != 0)
+ break;
+ KUNIT_EXPECT_TRUE(test, is_valid_dynamic_minor(miscdev[i].minor));
+ }
+
+ KUNIT_EXPECT_EQ(test, ret, 0);
+
+ miscstat.minor = miscdev_test_ranges[0].minor;
+ ret = misc_register(&miscstat);
+ KUNIT_EXPECT_EQ(test, ret, 0);
+ KUNIT_EXPECT_EQ(test, miscstat.minor, miscdev_test_ranges[0].minor);
+ if (ret == 0)
+ misc_deregister(&miscstat);
+
+ for (i--; i >= 0; i--) {
+ miscdev_test_can_open(test, &miscdev[i]);
+ misc_deregister(&miscdev[i]);
+ kfree_const(miscdev[i].name);
+ }
+}
+
+static void __init miscdev_test_conflict(struct kunit *test)
+{
+ int ret;
+ struct miscdevice miscdyn = {
+ .name = "miscdyn",
+ .minor = MISC_DYNAMIC_MINOR,
+ .fops = &miscdev_test_fops,
+ };
+ struct miscdevice miscstat = {
+ .name = "miscstat",
+ .fops = &miscdev_test_fops,
+ };
+
+ ret = misc_register(&miscdyn);
+ KUNIT_ASSERT_EQ(test, ret, 0);
+ KUNIT_EXPECT_TRUE(test, is_valid_dynamic_minor(miscdyn.minor));
+
+ /*
+ * Try to register a static minor with the same minor as the
+ * dynamic one.
+ */
+ miscstat.minor = miscdyn.minor;
+ ret = misc_register(&miscstat);
+ KUNIT_EXPECT_EQ(test, ret, -EBUSY);
+ if (ret == 0)
+ misc_deregister(&miscstat);
+
+ miscdev_test_can_open(test, &miscdyn);
+
+ misc_deregister(&miscdyn);
+}
+
+static void __init miscdev_test_conflict_reverse(struct kunit *test)
+{
+ int ret;
+ struct miscdevice miscdyn = {
+ .name = "miscdyn",
+ .minor = MISC_DYNAMIC_MINOR,
+ .fops = &miscdev_test_fops,
+ };
+ struct miscdevice miscstat = {
+ .name = "miscstat",
+ .fops = &miscdev_test_fops,
+ };
+
+ /*
+ * Find the first available dynamic minor to use it as a static
+ * minor later on.
+ */
+ ret = misc_register(&miscdyn);
+ KUNIT_ASSERT_EQ(test, ret, 0);
+ KUNIT_EXPECT_TRUE(test, is_valid_dynamic_minor(miscdyn.minor));
+ miscstat.minor = miscdyn.minor;
+ misc_deregister(&miscdyn);
+
+ ret = misc_register(&miscstat);
+ KUNIT_EXPECT_EQ(test, ret, 0);
+ KUNIT_EXPECT_EQ(test, miscstat.minor, miscdyn.minor);
+
+ /*
+ * Try to register a dynamic minor after registering a static minor
+ * within the dynamic range. It should work but get a different
+ * minor.
+ */
+ miscdyn.minor = MISC_DYNAMIC_MINOR;
+ ret = misc_register(&miscdyn);
+ KUNIT_EXPECT_EQ(test, ret, 0);
+ KUNIT_EXPECT_NE(test, miscdyn.minor, miscstat.minor);
+ KUNIT_EXPECT_TRUE(test, is_valid_dynamic_minor(miscdyn.minor));
+ if (ret == 0)
+ misc_deregister(&miscdyn);
+
+ miscdev_test_can_open(test, &miscstat);
+
+ misc_deregister(&miscstat);
+}
+
static struct kunit_case test_cases[] = {
KUNIT_CASE(kunit_dynamic_minor),
KUNIT_CASE(kunit_static_minor),
KUNIT_CASE(kunit_misc_dynamic_minor),
+ KUNIT_CASE_PARAM(miscdev_test_twice, miscdev_gen_params),
+ KUNIT_CASE_PARAM(miscdev_test_duplicate_minor, miscdev_gen_params),
+ KUNIT_CASE(miscdev_test_duplicate_name),
+ KUNIT_CASE(miscdev_test_duplicate_name_leak),
+ KUNIT_CASE_PARAM(miscdev_test_duplicate_error, miscdev_gen_params),
{}
};
static struct kunit_suite test_suite = {
- .name = "misc_minor_test",
+ .name = "miscdev",
+ .suite_init = miscdev_find_minors,
.test_cases = test_cases,
};
kunit_test_suite(test_suite);
+static struct kunit_case __refdata test_init_cases[] = {
+ KUNIT_CASE_PARAM(miscdev_test_static_basic, miscdev_gen_params),
+ KUNIT_CASE(miscdev_test_dynamic_basic),
+ KUNIT_CASE(miscdev_test_dynamic_only_range),
+ KUNIT_CASE(miscdev_test_collision),
+ KUNIT_CASE(miscdev_test_collision_reverse),
+ KUNIT_CASE(miscdev_test_conflict),
+ KUNIT_CASE(miscdev_test_conflict_reverse),
+ {}
+};
+
+static struct kunit_suite test_init_suite = {
+ .name = "miscdev_init",
+ .suite_init = miscdev_find_minors,
+ .test_cases = test_init_cases,
+};
+kunit_test_init_section_suite(test_init_suite);
+
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Vimal Agrawal");
-MODULE_DESCRIPTION("misc minor testing");
+MODULE_AUTHOR("Thadeu Lima de Souza Cascardo <cascardo@igalia.com>");
+MODULE_DESCRIPTION("Test module for misc character devices");
--
2.47.2
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