/*
   * This module provides an interface to trigger and test firmware loading.
   *
   * It is designed to be used for basic evaluation of the firmware loading
   * subsystem (for example when validating firmware verification). It lacks
   * any extra dependencies, and will not normally be loaded by the system
   * unless explicitly requested by name.
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/printk.h>

  #include <linux/completion.h>

  #include <linux/firmware.h>
  #include <linux/device.h>
  #include <linux/fs.h>
  #include <linux/miscdevice.h>
  #include <linux/slab.h>
  #include <linux/uaccess.h>
  
  static DEFINE_MUTEX(test_fw_mutex);
  static const struct firmware *test_firmware;
  
  static ssize_t test_fw_misc_read(struct file *f, char __user *buf,
  				 size_t size, loff_t *offset)
  {
  	ssize_t rc = 0;
  
  	mutex_lock(&test_fw_mutex);
  	if (test_firmware)
  		rc = simple_read_from_buffer(buf, size, offset,
  					     test_firmware->data,
  					     test_firmware->size);
  	mutex_unlock(&test_fw_mutex);
  	return rc;
  }
  
  static const struct file_operations test_fw_fops = {
  	.owner          = THIS_MODULE,
  	.read           = test_fw_misc_read,
  };
  
  static struct miscdevice test_fw_misc_device = {
  	.minor          = MISC_DYNAMIC_MINOR,
  	.name           = "test_firmware",
  	.fops           = &test_fw_fops,
  };
  
  static ssize_t trigger_request_store(struct device *dev,
  				     struct device_attribute *attr,
  				     const char *buf, size_t count)
  {
  	int rc;
  	char *name;

  	name = kstrndup(buf, count, GFP_KERNEL);

  	if (!name)
  		return -ENOSPC;

  
  	pr_info("loading '%s'
  ", name);
  
  	mutex_lock(&test_fw_mutex);
  	release_firmware(test_firmware);
  	test_firmware = NULL;
  	rc = request_firmware(&test_firmware, name, dev);

  	if (rc) {

  		pr_info("load of '%s' failed: %d
  ", name, rc);

  		goto out;
  	}
  	pr_info("loaded: %zu
  ", test_firmware->size);
  	rc = count;
  
  out:

  	mutex_unlock(&test_fw_mutex);
  
  	kfree(name);

  	return rc;

  }
  static DEVICE_ATTR_WO(trigger_request);

  static DECLARE_COMPLETION(async_fw_done);
  
  static void trigger_async_request_cb(const struct firmware *fw, void *context)
  {
  	test_firmware = fw;
  	complete(&async_fw_done);
  }
  
  static ssize_t trigger_async_request_store(struct device *dev,
  					   struct device_attribute *attr,
  					   const char *buf, size_t count)
  {
  	int rc;
  	char *name;
  
  	name = kstrndup(buf, count, GFP_KERNEL);
  	if (!name)
  		return -ENOSPC;
  
  	pr_info("loading '%s'
  ", name);
  
  	mutex_lock(&test_fw_mutex);
  	release_firmware(test_firmware);
  	test_firmware = NULL;
  	rc = request_firmware_nowait(THIS_MODULE, 1, name, dev, GFP_KERNEL,
  				     NULL, trigger_async_request_cb);
  	if (rc) {
  		pr_info("async load of '%s' failed: %d
  ", name, rc);
  		kfree(name);
  		goto out;
  	}
  	/* Free 'name' ASAP, to test for race conditions */
  	kfree(name);
  
  	wait_for_completion(&async_fw_done);
  
  	if (test_firmware) {
  		pr_info("loaded: %zu
  ", test_firmware->size);
  		rc = count;
  	} else {
  		pr_err("failed to async load firmware
  ");
  		rc = -ENODEV;
  	}
  
  out:
  	mutex_unlock(&test_fw_mutex);
  
  	return rc;
  }
  static DEVICE_ATTR_WO(trigger_async_request);

  static int __init test_firmware_init(void)
  {
  	int rc;
  
  	rc = misc_register(&test_fw_misc_device);
  	if (rc) {
  		pr_err("could not register misc device: %d
  ", rc);
  		return rc;
  	}
  	rc = device_create_file(test_fw_misc_device.this_device,
  				&dev_attr_trigger_request);
  	if (rc) {
  		pr_err("could not create sysfs interface: %d
  ", rc);
  		goto dereg;
  	}

  	rc = device_create_file(test_fw_misc_device.this_device,
  				&dev_attr_trigger_async_request);
  	if (rc) {
  		pr_err("could not create async sysfs interface: %d
  ", rc);
  		goto remove_file;
  	}

  	pr_warn("interface ready
  ");
  
  	return 0;

  
  remove_file:
  	device_remove_file(test_fw_misc_device.this_device,
  			   &dev_attr_trigger_async_request);

  dereg:
  	misc_deregister(&test_fw_misc_device);
  	return rc;
  }
  
  module_init(test_firmware_init);
  
  static void __exit test_firmware_exit(void)
  {
  	release_firmware(test_firmware);
  	device_remove_file(test_fw_misc_device.this_device,

  			   &dev_attr_trigger_async_request);
  	device_remove_file(test_fw_misc_device.this_device,

  			   &dev_attr_trigger_request);
  	misc_deregister(&test_fw_misc_device);
  	pr_warn("removed interface
  ");
  }
  
  module_exit(test_firmware_exit);
  
  MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
  MODULE_LICENSE("GPL");