lib/test_firmware.c

   1 /*
   2  * This module provides an interface to trigger and test firmware loading.
   3  *
   4  * It is designed to be used for basic evaluation of the firmware loading
   5  * subsystem (for example when validating firmware verification). It lacks
   6  * any extra dependencies, and will not normally be loaded by the system
   7  * unless explicitly requested by name.
   8  */
   9
  10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  11
  12 #include <linux/init.h>
  13 #include <linux/module.h>
  14 #include <linux/printk.h>
  15 #include <linux/firmware.h>
  16 #include <linux/device.h>
  17 #include <linux/fs.h>
  18 #include <linux/miscdevice.h>
  19 #include <linux/slab.h>
  20 #include <linux/uaccess.h>
  21
  22 static DEFINE_MUTEX(test_fw_mutex);
  23 static const struct firmware *test_firmware;
  24
  25 static ssize_t test_fw_misc_read(struct file *f, char __user *buf,
  26                                  size_t size, loff_t *offset)
  27 {
  28         ssize_t rc = 0;
  29
  30         mutex_lock(&test_fw_mutex);
  31         if (test_firmware)
  32                 rc = simple_read_from_buffer(buf, size, offset,
  33                                              test_firmware->data,
  34                                              test_firmware->size);
  35         mutex_unlock(&test_fw_mutex);
  36         return rc;
  37 }
  38
  39 static const struct file_operations test_fw_fops = {
  40         .owner          = THIS_MODULE,
  41         .read           = test_fw_misc_read,
  42 };
  43
  44 static struct miscdevice test_fw_misc_device = {
  45         .minor          = MISC_DYNAMIC_MINOR,
  46         .name           = "test_firmware",
  47         .fops           = &test_fw_fops,
  48 };
  49
  50 static ssize_t trigger_request_store(struct device *dev,
  51                                      struct device_attribute *attr,
  52                                      const char *buf, size_t count)
  53 {
  54         int rc;
  55         char *name;
  56
  57         name = kstrndup(buf, count, GFP_KERNEL);
  58         if (!name)
  59                 return -ENOSPC;
  60
  61         pr_info("loading '%s'\n", name);
  62
  63         mutex_lock(&test_fw_mutex);
  64         release_firmware(test_firmware);
  65         test_firmware = NULL;
  66         rc = request_firmware(&test_firmware, name, dev);
  67         if (rc) {
  68                 pr_info("load of '%s' failed: %d\n", name, rc);
  69                 goto out;
  70         }
  71         pr_info("loaded: %zu\n", test_firmware->size);
  72         rc = count;
  73
  74 out:
  75         mutex_unlock(&test_fw_mutex);
  76
  77         kfree(name);
  78
  79         return rc;
  80 }
  81 static DEVICE_ATTR_WO(trigger_request);
  82
  83 static int __init test_firmware_init(void)
  84 {
  85         int rc;
  86
  87         rc = misc_register(&test_fw_misc_device);
  88         if (rc) {
  89                 pr_err("could not register misc device: %d\n", rc);
  90                 return rc;
  91         }
  92         rc = device_create_file(test_fw_misc_device.this_device,
  93                                 &dev_attr_trigger_request);
  94         if (rc) {
  95                 pr_err("could not create sysfs interface: %d\n", rc);
  96                 goto dereg;
  97         }
  98
  99         pr_warn("interface ready\n");
 100
 101         return 0;
 102 dereg:
 103         misc_deregister(&test_fw_misc_device);
 104         return rc;
 105 }
 106
 107 module_init(test_firmware_init);
 108
 109 static void __exit test_firmware_exit(void)
 110 {
 111         release_firmware(test_firmware);
 112         device_remove_file(test_fw_misc_device.this_device,
 113                            &dev_attr_trigger_request);
 114         misc_deregister(&test_fw_misc_device);
 115         pr_warn("removed interface\n");
 116 }
 117
 118 module_exit(test_firmware_exit);
 119
 120 MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
 121 MODULE_LICENSE("GPL");