Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1239 insertions, 0 deletions

diff --git a/lib/test_kmod.c b/lib/test_kmod.c
new file mode 100644
index 000000000..6813b183a
--- /dev/null
+++ b/lib/test_kmod.c
@@ -0,0 +1,1239 @@
+/*
+ * kmod stress test driver
+ *
+ * Copyright (C) 2017 Luis R. Rodriguez <mcgrof@kernel.org>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or at your option any
+ * later version; or, when distributed separately from the Linux kernel or
+ * when incorporated into other software packages, subject to the following
+ * license:
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of copyleft-next (version 0.3.1 or later) as published
+ * at http://copyleft-next.org/.
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+/*
+ * This driver provides an interface to trigger and test the kernel's
+ * module loader through a series of configurations and a few triggers.
+ * To test this driver use the following script as root:
+ *
+ * tools/testing/selftests/kmod/kmod.sh --help
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/kmod.h>
+#include <linux/printk.h>
+#include <linux/kthread.h>
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/miscdevice.h>
+#include <linux/vmalloc.h>
+#include <linux/slab.h>
+#include <linux/device.h>
+
+#define TEST_START_NUM_THREADS	50
+#define TEST_START_DRIVER	"test_module"
+#define TEST_START_TEST_FS	"xfs"
+#define TEST_START_TEST_CASE	TEST_KMOD_DRIVER
+
+
+static bool force_init_test = false;
+module_param(force_init_test, bool_enable_only, 0644);
+MODULE_PARM_DESC(force_init_test,
+		 "Force kicking a test immediately after driver loads");
+
+/*
+ * For device allocation / registration
+ */
+static DEFINE_MUTEX(reg_dev_mutex);
+static LIST_HEAD(reg_test_devs);
+
+/*
+ * num_test_devs actually represents the *next* ID of the next
+ * device we will allow to create.
+ */
+static int num_test_devs;
+
+/**
+ * enum kmod_test_case - linker table test case
+ *
+ * If you add a  test case, please be sure to review if you need to se
+ * @need_mod_put for your tests case.
+ *
+ * @TEST_KMOD_DRIVER: stress tests request_module()
+ * @TEST_KMOD_FS_TYPE: stress tests get_fs_type()
+ */
+enum kmod_test_case {
+	__TEST_KMOD_INVALID = 0,
+
+	TEST_KMOD_DRIVER,
+	TEST_KMOD_FS_TYPE,
+
+	__TEST_KMOD_MAX,
+};
+
+struct test_config {
+	char *test_driver;
+	char *test_fs;
+	unsigned int num_threads;
+	enum kmod_test_case test_case;
+	int test_result;
+};
+
+struct kmod_test_device;
+
+/**
+ * kmod_test_device_info - thread info
+ *
+ * @ret_sync: return value if request_module() is used, sync request for
+ * 	@TEST_KMOD_DRIVER
+ * @fs_sync: return value of get_fs_type() for @TEST_KMOD_FS_TYPE
+ * @thread_idx: thread ID
+ * @test_dev: test device test is being performed under
+ * @need_mod_put: Some tests (get_fs_type() is one) requires putting the module
+ *	(module_put(fs_sync->owner)) when done, otherwise you will not be able
+ *	to unload the respective modules and re-test. We use this to keep
+ *	accounting of when we need this and to help out in case we need to
+ *	error out and deal with module_put() on error.
+ */
+struct kmod_test_device_info {
+	int ret_sync;
+	struct file_system_type *fs_sync;
+	struct task_struct *task_sync;
+	unsigned int thread_idx;
+	struct kmod_test_device *test_dev;
+	bool need_mod_put;
+};
+
+/**
+ * kmod_test_device - test device to help test kmod
+ *
+ * @dev_idx: unique ID for test device
+ * @config: configuration for the test
+ * @misc_dev: we use a misc device under the hood
+ * @dev: pointer to misc_dev's own struct device
+ * @config_mutex: protects configuration of test
+ * @trigger_mutex: the test trigger can only be fired once at a time
+ * @thread_lock: protects @done count, and the @info per each thread
+ * @done: number of threads which have completed or failed
+ * @test_is_oom: when we run out of memory, use this to halt moving forward
+ * @kthreads_done: completion used to signal when all work is done
+ * @list: needed to be part of the reg_test_devs
+ * @info: array of info for each thread
+ */
+struct kmod_test_device {
+	int dev_idx;
+	struct test_config config;
+	struct miscdevice misc_dev;
+	struct device *dev;
+	struct mutex config_mutex;
+	struct mutex trigger_mutex;
+	struct mutex thread_mutex;
+
+	unsigned int done;
+
+	bool test_is_oom;
+	struct completion kthreads_done;
+	struct list_head list;
+
+	struct kmod_test_device_info *info;
+};
+
+static const char *test_case_str(enum kmod_test_case test_case)
+{
+	switch (test_case) {
+	case TEST_KMOD_DRIVER:
+		return "TEST_KMOD_DRIVER";
+	case TEST_KMOD_FS_TYPE:
+		return "TEST_KMOD_FS_TYPE";
+	default:
+		return "invalid";
+	}
+}
+
+static struct miscdevice *dev_to_misc_dev(struct device *dev)
+{
+	return dev_get_drvdata(dev);
+}
+
+static struct kmod_test_device *misc_dev_to_test_dev(struct miscdevice *misc_dev)
+{
+	return container_of(misc_dev, struct kmod_test_device, misc_dev);
+}
+
+static struct kmod_test_device *dev_to_test_dev(struct device *dev)
+{
+	struct miscdevice *misc_dev;
+
+	misc_dev = dev_to_misc_dev(dev);
+
+	return misc_dev_to_test_dev(misc_dev);
+}
+
+/* Must run with thread_mutex held */
+static void kmod_test_done_check(struct kmod_test_device *test_dev,
+				 unsigned int idx)
+{
+	struct test_config *config = &test_dev->config;
+
+	test_dev->done++;
+	dev_dbg(test_dev->dev, "Done thread count: %u\n", test_dev->done);
+
+	if (test_dev->done == config->num_threads) {
+		dev_info(test_dev->dev, "Done: %u threads have all run now\n",
+			 test_dev->done);
+		dev_info(test_dev->dev, "Last thread to run: %u\n", idx);
+		complete(&test_dev->kthreads_done);
+	}
+}
+
+static void test_kmod_put_module(struct kmod_test_device_info *info)
+{
+	struct kmod_test_device *test_dev = info->test_dev;
+	struct test_config *config = &test_dev->config;
+
+	if (!info->need_mod_put)
+		return;
+
+	switch (config->test_case) {
+	case TEST_KMOD_DRIVER:
+		break;
+	case TEST_KMOD_FS_TYPE:
+		if (info && info->fs_sync && info->fs_sync->owner)
+			module_put(info->fs_sync->owner);
+		break;
+	default:
+		BUG();
+	}
+
+	info->need_mod_put = true;
+}
+
+static int run_request(void *data)
+{
+	struct kmod_test_device_info *info = data;
+	struct kmod_test_device *test_dev = info->test_dev;
+	struct test_config *config = &test_dev->config;
+
+	switch (config->test_case) {
+	case TEST_KMOD_DRIVER:
+		info->ret_sync = request_module("%s", config->test_driver);
+		break;
+	case TEST_KMOD_FS_TYPE:
+		info->fs_sync = get_fs_type(config->test_fs);
+		info->need_mod_put = true;
+		break;
+	default:
+		/* __trigger_config_run() already checked for test sanity */
+		BUG();
+		return -EINVAL;
+	}
+
+	dev_dbg(test_dev->dev, "Ran thread %u\n", info->thread_idx);
+
+	test_kmod_put_module(info);
+
+	mutex_lock(&test_dev->thread_mutex);
+	info->task_sync = NULL;
+	kmod_test_done_check(test_dev, info->thread_idx);
+	mutex_unlock(&test_dev->thread_mutex);
+
+	return 0;
+}
+
+static int tally_work_test(struct kmod_test_device_info *info)
+{
+	struct kmod_test_device *test_dev = info->test_dev;
+	struct test_config *config = &test_dev->config;
+	int err_ret = 0;
+
+	switch (config->test_case) {
+	case TEST_KMOD_DRIVER:
+		/*
+		 * Only capture errors, if one is found that's
+		 * enough, for now.
+		 */
+		if (info->ret_sync != 0)
+			err_ret = info->ret_sync;
+		dev_info(test_dev->dev,
+			 "Sync thread %d return status: %d\n",
+			 info->thread_idx, info->ret_sync);
+		break;
+	case TEST_KMOD_FS_TYPE:
+		/* For now we make this simple */
+		if (!info->fs_sync)
+			err_ret = -EINVAL;
+		dev_info(test_dev->dev, "Sync thread %u fs: %s\n",
+			 info->thread_idx, info->fs_sync ? config->test_fs :
+			 "NULL");
+		break;
+	default:
+		BUG();
+	}
+
+	return err_ret;
+}
+
+/*
+ * XXX: add result option to display if all errors did not match.
+ * For now we just keep any error code if one was found.
+ *
+ * If this ran it means *all* tasks were created fine and we
+ * are now just collecting results.
+ *
+ * Only propagate errors, do not override with a subsequent sucess case.
+ */
+static void tally_up_work(struct kmod_test_device *test_dev)
+{
+	struct test_config *config = &test_dev->config;
+	struct kmod_test_device_info *info;
+	unsigned int idx;
+	int err_ret = 0;
+	int ret = 0;
+
+	mutex_lock(&test_dev->thread_mutex);
+
+	dev_info(test_dev->dev, "Results:\n");
+
+	for (idx=0; idx < config->num_threads; idx++) {
+		info = &test_dev->info[idx];
+		ret = tally_work_test(info);
+		if (ret)
+			err_ret = ret;
+	}
+
+	/*
+	 * Note: request_module() returns 256 for a module not found even
+	 * though modprobe itself returns 1.
+	 */
+	config->test_result = err_ret;
+
+	mutex_unlock(&test_dev->thread_mutex);
+}
+
+static int try_one_request(struct kmod_test_device *test_dev, unsigned int idx)
+{
+	struct kmod_test_device_info *info = &test_dev->info[idx];
+	int fail_ret = -ENOMEM;
+
+	mutex_lock(&test_dev->thread_mutex);
+
+	info->thread_idx = idx;
+	info->test_dev = test_dev;
+	info->task_sync = kthread_run(run_request, info, "%s-%u",
+				      KBUILD_MODNAME, idx);
+
+	if (!info->task_sync || IS_ERR(info->task_sync)) {
+		test_dev->test_is_oom = true;
+		dev_err(test_dev->dev, "Setting up thread %u failed\n", idx);
+		info->task_sync = NULL;
+		goto err_out;
+	} else
+		dev_dbg(test_dev->dev, "Kicked off thread %u\n", idx);
+
+	mutex_unlock(&test_dev->thread_mutex);
+
+	return 0;
+
+err_out:
+	info->ret_sync = fail_ret;
+	mutex_unlock(&test_dev->thread_mutex);
+
+	return fail_ret;
+}
+
+static void test_dev_kmod_stop_tests(struct kmod_test_device *test_dev)
+{
+	struct test_config *config = &test_dev->config;
+	struct kmod_test_device_info *info;
+	unsigned int i;
+
+	dev_info(test_dev->dev, "Ending request_module() tests\n");
+
+	mutex_lock(&test_dev->thread_mutex);
+
+	for (i=0; i < config->num_threads; i++) {
+		info = &test_dev->info[i];
+		if (info->task_sync && !IS_ERR(info->task_sync)) {
+			dev_info(test_dev->dev,
+				 "Stopping still-running thread %i\n", i);
+			kthread_stop(info->task_sync);
+		}
+
+		/*
+		 * info->task_sync is well protected, it can only be
+		 * NULL or a pointer to a struct. If its NULL we either
+		 * never ran, or we did and we completed the work. Completed
+		 * tasks *always* put the module for us. This is a sanity
+		 * check -- just in case.
+		 */
+		if (info->task_sync && info->need_mod_put)
+			test_kmod_put_module(info);
+	}
+
+	mutex_unlock(&test_dev->thread_mutex);
+}
+
+/*
+ * Only wait *iff* we did not run into any errors during all of our thread
+ * set up. If run into any issues we stop threads and just bail out with
+ * an error to the trigger. This also means we don't need any tally work
+ * for any threads which fail.
+ */
+static int try_requests(struct kmod_test_device *test_dev)
+{
+	struct test_config *config = &test_dev->config;
+	unsigned int idx;
+	int ret;
+	bool any_error = false;
+
+	for (idx=0; idx < config->num_threads; idx++) {
+		if (test_dev->test_is_oom) {
+			any_error = true;
+			break;
+		}
+
+		ret = try_one_request(test_dev, idx);
+		if (ret) {
+			any_error = true;
+			break;
+		}
+	}
+
+	if (!any_error) {
+		test_dev->test_is_oom = false;
+		dev_info(test_dev->dev,
+			 "No errors were found while initializing threads\n");
+		wait_for_completion(&test_dev->kthreads_done);
+		tally_up_work(test_dev);
+	} else {
+		test_dev->test_is_oom = true;
+		dev_info(test_dev->dev,
+			 "At least one thread failed to start, stop all work\n");
+		test_dev_kmod_stop_tests(test_dev);
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+static int run_test_driver(struct kmod_test_device *test_dev)
+{
+	struct test_config *config = &test_dev->config;
+
+	dev_info(test_dev->dev, "Test case: %s (%u)\n",
+		 test_case_str(config->test_case),
+		 config->test_case);
+	dev_info(test_dev->dev, "Test driver to load: %s\n",
+		 config->test_driver);
+	dev_info(test_dev->dev, "Number of threads to run: %u\n",
+		 config->num_threads);
+	dev_info(test_dev->dev, "Thread IDs will range from 0 - %u\n",
+		 config->num_threads - 1);
+
+	return try_requests(test_dev);
+}
+
+static int run_test_fs_type(struct kmod_test_device *test_dev)
+{
+	struct test_config *config = &test_dev->config;
+
+	dev_info(test_dev->dev, "Test case: %s (%u)\n",
+		 test_case_str(config->test_case),
+		 config->test_case);
+	dev_info(test_dev->dev, "Test filesystem to load: %s\n",
+		 config->test_fs);
+	dev_info(test_dev->dev, "Number of threads to run: %u\n",
+		 config->num_threads);
+	dev_info(test_dev->dev, "Thread IDs will range from 0 - %u\n",
+		 config->num_threads - 1);
+
+	return try_requests(test_dev);
+}
+
+static ssize_t config_show(struct device *dev,
+			   struct device_attribute *attr,
+			   char *buf)
+{
+	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
+	struct test_config *config = &test_dev->config;
+	int len = 0;
+
+	mutex_lock(&test_dev->config_mutex);
+
+	len += snprintf(buf, PAGE_SIZE,
+			"Custom trigger configuration for: %s\n",
+			dev_name(dev));
+
+	len += snprintf(buf+len, PAGE_SIZE - len,
+			"Number of threads:\t%u\n",
+			config->num_threads);
+
+	len += snprintf(buf+len, PAGE_SIZE - len,
+			"Test_case:\t%s (%u)\n",
+			test_case_str(config->test_case),
+			config->test_case);
+
+	if (config->test_driver)
+		len += snprintf(buf+len, PAGE_SIZE - len,
+				"driver:\t%s\n",
+				config->test_driver);
+	else
+		len += snprintf(buf+len, PAGE_SIZE - len,
+				"driver:\tEMPTY\n");
+
+	if (config->test_fs)
+		len += snprintf(buf+len, PAGE_SIZE - len,
+				"fs:\t%s\n",
+				config->test_fs);
+	else
+		len += snprintf(buf+len, PAGE_SIZE - len,
+				"fs:\tEMPTY\n");
+
+	mutex_unlock(&test_dev->config_mutex);
+
+	return len;
+}
+static DEVICE_ATTR_RO(config);
+
+/*
+ * This ensures we don't allow kicking threads through if our configuration
+ * is faulty.
+ */
+static int __trigger_config_run(struct kmod_test_device *test_dev)
+{
+	struct test_config *config = &test_dev->config;
+
+	test_dev->done = 0;
+
+	switch (config->test_case) {
+	case TEST_KMOD_DRIVER:
+		return run_test_driver(test_dev);
+	case TEST_KMOD_FS_TYPE:
+		return run_test_fs_type(test_dev);
+	default:
+		dev_warn(test_dev->dev,
+			 "Invalid test case requested: %u\n",
+			 config->test_case);
+		return -EINVAL;
+	}
+}
+
+static int trigger_config_run(struct kmod_test_device *test_dev)
+{
+	struct test_config *config = &test_dev->config;
+	int ret;
+
+	mutex_lock(&test_dev->trigger_mutex);
+	mutex_lock(&test_dev->config_mutex);
+
+	ret = __trigger_config_run(test_dev);
+	if (ret < 0)
+		goto out;
+	dev_info(test_dev->dev, "General test result: %d\n",
+		 config->test_result);
+
+	/*
+	 * We must return 0 after a trigger even unless something went
+	 * wrong with the setup of the test. If the test setup went fine
+	 * then userspace must just check the result of config->test_result.
+	 * One issue with relying on the return from a call in the kernel
+	 * is if the kernel returns a possitive value using this trigger
+	 * will not return the value to userspace, it would be lost.
+	 *
+	 * By not relying on capturing the return value of tests we are using
+	 * through the trigger it also us to run tests with set -e and only
+	 * fail when something went wrong with the driver upon trigger
+	 * requests.
+	 */
+	ret = 0;
+
+out:
+	mutex_unlock(&test_dev->config_mutex);
+	mutex_unlock(&test_dev->trigger_mutex);
+
+	return ret;
+}
+
+static ssize_t
+trigger_config_store(struct device *dev,
+		     struct device_attribute *attr,
+		     const char *buf, size_t count)
+{
+	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
+	int ret;
+
+	if (test_dev->test_is_oom)
+		return -ENOMEM;
+
+	/* For all intents and purposes we don't care what userspace
+	 * sent this trigger, we care only that we were triggered.
+	 * We treat the return value only for caputuring issues with
+	 * the test setup. At this point all the test variables should
+	 * have been allocated so typically this should never fail.
+	 */
+	ret = trigger_config_run(test_dev);
+	if (unlikely(ret < 0))
+		goto out;
+
+	/*
+	 * Note: any return > 0 will be treated as success
+	 * and the error value will not be available to userspace.
+	 * Do not rely on trying to send to userspace a test value
+	 * return value as possitive return errors will be lost.
+	 */
+	if (WARN_ON(ret > 0))
+		return -EINVAL;
+
+	ret = count;
+out:
+	return ret;
+}
+static DEVICE_ATTR_WO(trigger_config);
+
+/*
+ * XXX: move to kstrncpy() once merged.
+ *
+ * Users should use kfree_const() when freeing these.
+ */
+static int __kstrncpy(char **dst, const char *name, size_t count, gfp_t gfp)
+{
+	*dst = kstrndup(name, count, gfp);
+	if (!*dst)
+		return -ENOSPC;
+	return count;
+}
+
+static int config_copy_test_driver_name(struct test_config *config,
+				    const char *name,
+				    size_t count)
+{
+	return __kstrncpy(&config->test_driver, name, count, GFP_KERNEL);
+}
+
+
+static int config_copy_test_fs(struct test_config *config, const char *name,
+			       size_t count)
+{
+	return __kstrncpy(&config->test_fs, name, count, GFP_KERNEL);
+}
+
+static void __kmod_config_free(struct test_config *config)
+{
+	if (!config)
+		return;
+
+	kfree_const(config->test_driver);
+	config->test_driver = NULL;
+
+	kfree_const(config->test_fs);
+	config->test_fs = NULL;
+}
+
+static void kmod_config_free(struct kmod_test_device *test_dev)
+{
+	struct test_config *config;
+
+	if (!test_dev)
+		return;
+
+	config = &test_dev->config;
+
+	mutex_lock(&test_dev->config_mutex);
+	__kmod_config_free(config);
+	mutex_unlock(&test_dev->config_mutex);
+}
+
+static ssize_t config_test_driver_store(struct device *dev,
+					struct device_attribute *attr,
+					const char *buf, size_t count)
+{
+	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
+	struct test_config *config = &test_dev->config;
+	int copied;
+
+	mutex_lock(&test_dev->config_mutex);
+
+	kfree_const(config->test_driver);
+	config->test_driver = NULL;
+
+	copied = config_copy_test_driver_name(config, buf, count);
+	mutex_unlock(&test_dev->config_mutex);
+
+	return copied;
+}
+
+/*
+ * As per sysfs_kf_seq_show() the buf is max PAGE_SIZE.
+ */
+static ssize_t config_test_show_str(struct mutex *config_mutex,
+				    char *dst,
+				    char *src)
+{
+	int len;
+
+	mutex_lock(config_mutex);
+	len = snprintf(dst, PAGE_SIZE, "%s\n", src);
+	mutex_unlock(config_mutex);
+
+	return len;
+}
+
+static ssize_t config_test_driver_show(struct device *dev,
+					struct device_attribute *attr,
+					char *buf)
+{
+	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
+	struct test_config *config = &test_dev->config;
+
+	return config_test_show_str(&test_dev->config_mutex, buf,
+				    config->test_driver);
+}
+static DEVICE_ATTR_RW(config_test_driver);
+
+static ssize_t config_test_fs_store(struct device *dev,
+				    struct device_attribute *attr,
+				    const char *buf, size_t count)
+{
+	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
+	struct test_config *config = &test_dev->config;
+	int copied;
+
+	mutex_lock(&test_dev->config_mutex);
+
+	kfree_const(config->test_fs);
+	config->test_fs = NULL;
+
+	copied = config_copy_test_fs(config, buf, count);
+	mutex_unlock(&test_dev->config_mutex);
+
+	return copied;
+}
+
+static ssize_t config_test_fs_show(struct device *dev,
+				   struct device_attribute *attr,
+				   char *buf)
+{
+	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
+	struct test_config *config = &test_dev->config;
+
+	return config_test_show_str(&test_dev->config_mutex, buf,
+				    config->test_fs);
+}
+static DEVICE_ATTR_RW(config_test_fs);
+
+static int trigger_config_run_type(struct kmod_test_device *test_dev,
+				   enum kmod_test_case test_case,
+				   const char *test_str)
+{
+	int copied = 0;
+	struct test_config *config = &test_dev->config;
+
+	mutex_lock(&test_dev->config_mutex);
+
+	switch (test_case) {
+	case TEST_KMOD_DRIVER:
+		kfree_const(config->test_driver);
+		config->test_driver = NULL;
+		copied = config_copy_test_driver_name(config, test_str,
+						      strlen(test_str));
+		break;
+	case TEST_KMOD_FS_TYPE:
+		kfree_const(config->test_fs);
+		config->test_fs = NULL;
+		copied = config_copy_test_fs(config, test_str,
+					     strlen(test_str));
+		break;
+	default:
+		mutex_unlock(&test_dev->config_mutex);
+		return -EINVAL;
+	}
+
+	config->test_case = test_case;
+
+	mutex_unlock(&test_dev->config_mutex);
+
+	if (copied <= 0 || copied != strlen(test_str)) {
+		test_dev->test_is_oom = true;
+		return -ENOMEM;
+	}
+
+	test_dev->test_is_oom = false;
+
+	return trigger_config_run(test_dev);
+}
+
+static void free_test_dev_info(struct kmod_test_device *test_dev)
+{
+	vfree(test_dev->info);
+	test_dev->info = NULL;
+}
+
+static int kmod_config_sync_info(struct kmod_test_device *test_dev)
+{
+	struct test_config *config = &test_dev->config;
+
+	free_test_dev_info(test_dev);
+	test_dev->info =
+		vzalloc(array_size(sizeof(struct kmod_test_device_info),
+				   config->num_threads));
+	if (!test_dev->info)
+		return -ENOMEM;
+
+	return 0;
+}
+
+/*
+ * Old kernels may not have this, if you want to port this code to
+ * test it on older kernels.
+ */
+#ifdef get_kmod_umh_limit
+static unsigned int kmod_init_test_thread_limit(void)
+{
+	return get_kmod_umh_limit();
+}
+#else
+static unsigned int kmod_init_test_thread_limit(void)
+{
+	return TEST_START_NUM_THREADS;
+}
+#endif
+
+static int __kmod_config_init(struct kmod_test_device *test_dev)
+{
+	struct test_config *config = &test_dev->config;
+	int ret = -ENOMEM, copied;
+
+	__kmod_config_free(config);
+
+	copied = config_copy_test_driver_name(config, TEST_START_DRIVER,
+					      strlen(TEST_START_DRIVER));
+	if (copied != strlen(TEST_START_DRIVER))
+		goto err_out;
+
+	copied = config_copy_test_fs(config, TEST_START_TEST_FS,
+				     strlen(TEST_START_TEST_FS));
+	if (copied != strlen(TEST_START_TEST_FS))
+		goto err_out;
+
+	config->num_threads = kmod_init_test_thread_limit();
+	config->test_result = 0;
+	config->test_case = TEST_START_TEST_CASE;
+
+	ret = kmod_config_sync_info(test_dev);
+	if (ret)
+		goto err_out;
+
+	test_dev->test_is_oom = false;
+
+	return 0;
+
+err_out:
+	test_dev->test_is_oom = true;
+	WARN_ON(test_dev->test_is_oom);
+
+	__kmod_config_free(config);
+
+	return ret;
+}
+
+static ssize_t reset_store(struct device *dev,
+			   struct device_attribute *attr,
+			   const char *buf, size_t count)
+{
+	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
+	int ret;
+
+	mutex_lock(&test_dev->trigger_mutex);
+	mutex_lock(&test_dev->config_mutex);
+
+	ret = __kmod_config_init(test_dev);
+	if (ret < 0) {
+		ret = -ENOMEM;
+		dev_err(dev, "could not alloc settings for config trigger: %d\n",
+		       ret);
+		goto out;
+	}
+
+	dev_info(dev, "reset\n");
+	ret = count;
+
+out:
+	mutex_unlock(&test_dev->config_mutex);
+	mutex_unlock(&test_dev->trigger_mutex);
+
+	return ret;
+}
+static DEVICE_ATTR_WO(reset);
+
+static int test_dev_config_update_uint_sync(struct kmod_test_device *test_dev,
+					    const char *buf, size_t size,
+					    unsigned int *config,
+					    int (*test_sync)(struct kmod_test_device *test_dev))
+{
+	int ret;
+	unsigned long new;
+	unsigned int old_val;
+
+	ret = kstrtoul(buf, 10, &new);
+	if (ret)
+		return ret;
+
+	if (new > UINT_MAX)
+		return -EINVAL;
+
+	mutex_lock(&test_dev->config_mutex);
+
+	old_val = *config;
+	*(unsigned int *)config = new;
+
+	ret = test_sync(test_dev);
+	if (ret) {
+		*(unsigned int *)config = old_val;
+
+		ret = test_sync(test_dev);
+		WARN_ON(ret);
+
+		mutex_unlock(&test_dev->config_mutex);
+		return -EINVAL;
+	}
+
+	mutex_unlock(&test_dev->config_mutex);
+	/* Always return full write size even if we didn't consume all */
+	return size;
+}
+
+static int test_dev_config_update_uint_range(struct kmod_test_device *test_dev,
+					     const char *buf, size_t size,
+					     unsigned int *config,
+					     unsigned int min,
+					     unsigned int max)
+{
+	int ret;
+	unsigned long new;
+
+	ret = kstrtoul(buf, 10, &new);
+	if (ret)
+		return ret;
+
+	if (new < min || new > max)
+		return -EINVAL;
+
+	mutex_lock(&test_dev->config_mutex);
+	*config = new;
+	mutex_unlock(&test_dev->config_mutex);
+
+	/* Always return full write size even if we didn't consume all */
+	return size;
+}
+
+static int test_dev_config_update_int(struct kmod_test_device *test_dev,
+				      const char *buf, size_t size,
+				      int *config)
+{
+	int ret;
+	long new;
+
+	ret = kstrtol(buf, 10, &new);
+	if (ret)
+		return ret;
+
+	if (new < INT_MIN || new > INT_MAX)
+		return -EINVAL;
+
+	mutex_lock(&test_dev->config_mutex);
+	*config = new;
+	mutex_unlock(&test_dev->config_mutex);
+	/* Always return full write size even if we didn't consume all */
+	return size;
+}
+
+static ssize_t test_dev_config_show_int(struct kmod_test_device *test_dev,
+					char *buf,
+					int config)
+{
+	int val;
+
+	mutex_lock(&test_dev->config_mutex);
+	val = config;
+	mutex_unlock(&test_dev->config_mutex);
+
+	return snprintf(buf, PAGE_SIZE, "%d\n", val);
+}
+
+static ssize_t test_dev_config_show_uint(struct kmod_test_device *test_dev,
+					 char *buf,
+					 unsigned int config)
+{
+	unsigned int val;
+
+	mutex_lock(&test_dev->config_mutex);
+	val = config;
+	mutex_unlock(&test_dev->config_mutex);
+
+	return snprintf(buf, PAGE_SIZE, "%u\n", val);
+}
+
+static ssize_t test_result_store(struct device *dev,
+				 struct device_attribute *attr,
+				 const char *buf, size_t count)
+{
+	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
+	struct test_config *config = &test_dev->config;
+
+	return test_dev_config_update_int(test_dev, buf, count,
+					  &config->test_result);
+}
+
+static ssize_t config_num_threads_store(struct device *dev,
+					struct device_attribute *attr,
+					const char *buf, size_t count)
+{
+	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
+	struct test_config *config = &test_dev->config;
+
+	return test_dev_config_update_uint_sync(test_dev, buf, count,
+						&config->num_threads,
+						kmod_config_sync_info);
+}
+
+static ssize_t config_num_threads_show(struct device *dev,
+				       struct device_attribute *attr,
+				       char *buf)
+{
+	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
+	struct test_config *config = &test_dev->config;
+
+	return test_dev_config_show_int(test_dev, buf, config->num_threads);
+}
+static DEVICE_ATTR_RW(config_num_threads);
+
+static ssize_t config_test_case_store(struct device *dev,
+				      struct device_attribute *attr,
+				      const char *buf, size_t count)
+{
+	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
+	struct test_config *config = &test_dev->config;
+
+	return test_dev_config_update_uint_range(test_dev, buf, count,
+						 &config->test_case,
+						 __TEST_KMOD_INVALID + 1,
+						 __TEST_KMOD_MAX - 1);
+}
+
+static ssize_t config_test_case_show(struct device *dev,
+				     struct device_attribute *attr,
+				     char *buf)
+{
+	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
+	struct test_config *config = &test_dev->config;
+
+	return test_dev_config_show_uint(test_dev, buf, config->test_case);
+}
+static DEVICE_ATTR_RW(config_test_case);
+
+static ssize_t test_result_show(struct device *dev,
+				struct device_attribute *attr,
+				char *buf)
+{
+	struct kmod_test_device *test_dev = dev_to_test_dev(dev);
+	struct test_config *config = &test_dev->config;
+
+	return test_dev_config_show_int(test_dev, buf, config->test_result);
+}
+static DEVICE_ATTR_RW(test_result);
+
+#define TEST_KMOD_DEV_ATTR(name)		&dev_attr_##name.attr
+
+static struct attribute *test_dev_attrs[] = {
+	TEST_KMOD_DEV_ATTR(trigger_config),
+	TEST_KMOD_DEV_ATTR(config),
+	TEST_KMOD_DEV_ATTR(reset),
+
+	TEST_KMOD_DEV_ATTR(config_test_driver),
+	TEST_KMOD_DEV_ATTR(config_test_fs),
+	TEST_KMOD_DEV_ATTR(config_num_threads),
+	TEST_KMOD_DEV_ATTR(config_test_case),
+	TEST_KMOD_DEV_ATTR(test_result),
+
+	NULL,
+};
+
+ATTRIBUTE_GROUPS(test_dev);
+
+static int kmod_config_init(struct kmod_test_device *test_dev)
+{
+	int ret;
+
+	mutex_lock(&test_dev->config_mutex);
+	ret = __kmod_config_init(test_dev);
+	mutex_unlock(&test_dev->config_mutex);
+
+	return ret;
+}
+
+static struct kmod_test_device *alloc_test_dev_kmod(int idx)
+{
+	int ret;
+	struct kmod_test_device *test_dev;
+	struct miscdevice *misc_dev;
+
+	test_dev = vzalloc(sizeof(struct kmod_test_device));
+	if (!test_dev)
+		goto err_out;
+
+	mutex_init(&test_dev->config_mutex);
+	mutex_init(&test_dev->trigger_mutex);
+	mutex_init(&test_dev->thread_mutex);
+
+	init_completion(&test_dev->kthreads_done);
+
+	ret = kmod_config_init(test_dev);
+	if (ret < 0) {
+		pr_err("Cannot alloc kmod_config_init()\n");
+		goto err_out_free;
+	}
+
+	test_dev->dev_idx = idx;
+	misc_dev = &test_dev->misc_dev;
+
+	misc_dev->minor = MISC_DYNAMIC_MINOR;
+	misc_dev->name = kasprintf(GFP_KERNEL, "test_kmod%d", idx);
+	if (!misc_dev->name) {
+		pr_err("Cannot alloc misc_dev->name\n");
+		goto err_out_free_config;
+	}
+	misc_dev->groups = test_dev_groups;
+
+	return test_dev;
+
+err_out_free_config:
+	free_test_dev_info(test_dev);
+	kmod_config_free(test_dev);
+err_out_free:
+	vfree(test_dev);
+	test_dev = NULL;
+err_out:
+	return NULL;
+}
+
+static void free_test_dev_kmod(struct kmod_test_device *test_dev)
+{
+	if (test_dev) {
+		kfree_const(test_dev->misc_dev.name);
+		test_dev->misc_dev.name = NULL;
+		free_test_dev_info(test_dev);
+		kmod_config_free(test_dev);
+		vfree(test_dev);
+		test_dev = NULL;
+	}
+}
+
+static struct kmod_test_device *register_test_dev_kmod(void)
+{
+	struct kmod_test_device *test_dev = NULL;
+	int ret;
+
+	mutex_lock(&reg_dev_mutex);
+
+	/* int should suffice for number of devices, test for wrap */
+	if (num_test_devs + 1 == INT_MAX) {
+		pr_err("reached limit of number of test devices\n");
+		goto out;
+	}
+
+	test_dev = alloc_test_dev_kmod(num_test_devs);
+	if (!test_dev)
+		goto out;
+
+	ret = misc_register(&test_dev->misc_dev);
+	if (ret) {
+		pr_err("could not register misc device: %d\n", ret);
+		free_test_dev_kmod(test_dev);
+		test_dev = NULL;
+		goto out;
+	}
+
+	test_dev->dev = test_dev->misc_dev.this_device;
+	list_add_tail(&test_dev->list, &reg_test_devs);
+	dev_info(test_dev->dev, "interface ready\n");
+
+	num_test_devs++;
+
+out:
+	mutex_unlock(&reg_dev_mutex);
+
+	return test_dev;
+
+}
+
+static int __init test_kmod_init(void)
+{
+	struct kmod_test_device *test_dev;
+	int ret;
+
+	test_dev = register_test_dev_kmod();
+	if (!test_dev) {
+		pr_err("Cannot add first test kmod device\n");
+		return -ENODEV;
+	}
+
+	/*
+	 * With some work we might be able to gracefully enable
+	 * testing with this driver built-in, for now this seems
+	 * rather risky. For those willing to try have at it,
+	 * and enable the below. Good luck! If that works, try
+	 * lowering the init level for more fun.
+	 */
+	if (force_init_test) {
+		ret = trigger_config_run_type(test_dev,
+					      TEST_KMOD_DRIVER, "tun");
+		if (WARN_ON(ret))
+			return ret;
+		ret = trigger_config_run_type(test_dev,
+					      TEST_KMOD_FS_TYPE, "btrfs");
+		if (WARN_ON(ret))
+			return ret;
+	}
+
+	return 0;
+}
+late_initcall(test_kmod_init);
+
+static
+void unregister_test_dev_kmod(struct kmod_test_device *test_dev)
+{
+	mutex_lock(&test_dev->trigger_mutex);
+	mutex_lock(&test_dev->config_mutex);
+
+	test_dev_kmod_stop_tests(test_dev);
+
+	dev_info(test_dev->dev, "removing interface\n");
+	misc_deregister(&test_dev->misc_dev);
+
+	mutex_unlock(&test_dev->config_mutex);
+	mutex_unlock(&test_dev->trigger_mutex);
+
+	free_test_dev_kmod(test_dev);
+}
+
+static void __exit test_kmod_exit(void)
+{
+	struct kmod_test_device *test_dev, *tmp;
+
+	mutex_lock(&reg_dev_mutex);
+	list_for_each_entry_safe(test_dev, tmp, &reg_test_devs, list) {
+		list_del(&test_dev->list);
+		unregister_test_dev_kmod(test_dev);
+	}
+	mutex_unlock(&reg_dev_mutex);
+}
+module_exit(test_kmod_exit);
+
+MODULE_AUTHOR("Luis R. Rodriguez <mcgrof@kernel.org>");
+MODULE_LICENSE("GPL");