1/*
2 * custom_method.c - debugfs interface for customizing ACPI control method
3 */
4
5#include <linux/init.h>
6#include <linux/module.h>
7#include <linux/kernel.h>
8#include <linux/uaccess.h>
9#include <linux/debugfs.h>
10#include <linux/acpi.h>
11
12#include "internal.h"
13
14#define _COMPONENT		ACPI_SYSTEM_COMPONENT
15ACPI_MODULE_NAME("custom_method");
16MODULE_LICENSE("GPL");
17
18static struct dentry *cm_dentry;
19
20/* /sys/kernel/debug/acpi/custom_method */
21
22static ssize_t cm_write(struct file *file, const char __user * user_buf,
23			size_t count, loff_t *ppos)
24{
25	static char *buf;
26	static u32 max_size;
27	static u32 uncopied_bytes;
28
29	struct acpi_table_header table;
30	acpi_status status;
31
32	if (!(*ppos)) {
33		/* parse the table header to get the table length */
34		if (count <= sizeof(struct acpi_table_header))
35			return -EINVAL;
36		if (copy_from_user(&table, user_buf,
37				   sizeof(struct acpi_table_header)))
38			return -EFAULT;
39		uncopied_bytes = max_size = table.length;
40		buf = kzalloc(max_size, GFP_KERNEL);
41		if (!buf)
42			return -ENOMEM;
43	}
44
45	if (buf == NULL)
46		return -EINVAL;
47
48	if ((*ppos > max_size) ||
49	    (*ppos + count > max_size) ||
50	    (*ppos + count < count) ||
51	    (count > uncopied_bytes))
52		return -EINVAL;
53
54	if (copy_from_user(buf + (*ppos), user_buf, count)) {
55		kfree(buf);
56		buf = NULL;
57		return -EFAULT;
58	}
59
60	uncopied_bytes -= count;
61	*ppos += count;
62
63	if (!uncopied_bytes) {
64		status = acpi_install_method(buf);
65		kfree(buf);
66		buf = NULL;
67		if (ACPI_FAILURE(status))
68			return -EINVAL;
69		add_taint(TAINT_OVERRIDDEN_ACPI_TABLE, LOCKDEP_NOW_UNRELIABLE);
70	}
71
72	return count;
73}
74
75static const struct file_operations cm_fops = {
76	.write = cm_write,
77	.llseek = default_llseek,
78};
79
80static int __init acpi_custom_method_init(void)
81{
82	if (acpi_debugfs_dir == NULL)
83		return -ENOENT;
84
85	cm_dentry = debugfs_create_file("custom_method", S_IWUSR,
86					acpi_debugfs_dir, NULL, &cm_fops);
87	if (cm_dentry == NULL)
88		return -ENODEV;
89
90	return 0;
91}
92
93static void __exit acpi_custom_method_exit(void)
94{
95	if (cm_dentry)
96		debugfs_remove(cm_dentry);
97 }
98
99module_init(acpi_custom_method_init);
100module_exit(acpi_custom_method_exit);
101