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
22static DEFINE_MUTEX(test_fw_mutex);
23static const struct firmware *test_firmware;
24
25static 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
39static const struct file_operations test_fw_fops = {
40	.owner          = THIS_MODULE,
41	.read           = test_fw_misc_read,
42};
43
44static struct miscdevice test_fw_misc_device = {
45	.minor          = MISC_DYNAMIC_MINOR,
46	.name           = "test_firmware",
47	.fops           = &test_fw_fops,
48};
49
50static 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}
77static DEVICE_ATTR_WO(trigger_request);
78
79static 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;
98dereg:
99	misc_deregister(&test_fw_misc_device);
100	return rc;
101}
102
103module_init(test_firmware_init);
104
105static 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
114module_exit(test_firmware_exit);
115
116MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
117MODULE_LICENSE("GPL");
118