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         pr_info("loaded: %zu\n", test_firmware ? test_firmware->size : 0);
  71         mutex_unlock(&test_fw_mutex);
  72
  73         kfree(name);
  74
  75         return count;
  76 }
  77 static DEVICE_ATTR_WO(trigger_request);
  78
  79 static int __init test_firmware_init(void)
  80 {
  81         int rc;
  82
  83         rc = misc_register(&test_fw_misc_device);
  84         if (rc) {
  85                 pr_err("could not register misc device: %d\n", rc);
  86                 return rc;
  87         }
  88         rc = device_create_file(test_fw_misc_device.this_device,
  89                                 &dev_attr_trigger_request);
  90         if (rc) {
  91                 pr_err("could not create sysfs interface: %d\n", rc);
  92                 goto dereg;
  93         }
  94
  95         pr_warn("interface ready\n");
  96
  97         return 0;
  98 dereg:
  99         misc_deregister(&test_fw_misc_device);
 100         return rc;
 101 }
 102
 103 module_init(test_firmware_init);
 104
 105 static void __exit test_firmware_exit(void)
 106 {
 107         release_firmware(test_firmware);
 108         device_remove_file(test_fw_misc_device.this_device,
 109                            &dev_attr_trigger_request);
 110         misc_deregister(&test_fw_misc_device);
 111         pr_warn("removed interface\n");
 112 }
 113
 114 module_exit(test_firmware_exit);
 115
 116 MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
 117 MODULE_LICENSE("GPL");