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 = kzalloc(count + 1, GFP_KERNEL);
  58         if (!name)
  59                 return -ENOSPC;
  60         memcpy(name, buf, count);
  61
  62         pr_info("loading '%s'\n", name);
  63
  64         mutex_lock(&test_fw_mutex);
  65         release_firmware(test_firmware);
  66         test_firmware = NULL;
  67         rc = request_firmware(&test_firmware, name, dev);
  68         if (rc) {
  69                 pr_info("load of '%s' failed: %d\n", name, rc);
  70                 goto out;
  71         }
  72         pr_info("loaded: %zu\n", test_firmware->size);
  73         rc = count;
  74
  75 out:
  76         mutex_unlock(&test_fw_mutex);
  77
  78         kfree(name);
  79
  80         return rc;
  81 }
  82 static DEVICE_ATTR_WO(trigger_request);
  83
  84 static int __init test_firmware_init(void)
  85 {
  86         int rc;
  87
  88         rc = misc_register(&test_fw_misc_device);
  89         if (rc) {
  90                 pr_err("could not register misc device: %d\n", rc);
  91                 return rc;
  92         }
  93         rc = device_create_file(test_fw_misc_device.this_device,
  94                                 &dev_attr_trigger_request);
  95         if (rc) {
  96                 pr_err("could not create sysfs interface: %d\n", rc);
  97                 goto dereg;
  98         }
  99
 100         pr_warn("interface ready\n");
 101
 102         return 0;
 103 dereg:
 104         misc_deregister(&test_fw_misc_device);
 105         return rc;
 106 }
 107
 108 module_init(test_firmware_init);
 109
 110 static void __exit test_firmware_exit(void)
 111 {
 112         release_firmware(test_firmware);
 113         device_remove_file(test_fw_misc_device.this_device,
 114                            &dev_attr_trigger_request);
 115         misc_deregister(&test_fw_misc_device);
 116         pr_warn("removed interface\n");
 117 }
 118
 119 module_exit(test_firmware_exit);
 120
 121 MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
 122 MODULE_LICENSE("GPL");