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
test_fw_misc_read(struct file * f,char __user * buf,size_t size,loff_t * offset)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
trigger_request_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)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
test_firmware_init(void)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
test_firmware_exit(void)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");
118