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
15 ACPI_MODULE_NAME("custom_method");
16 MODULE_LICENSE("GPL");
17
18 static struct dentry *cm_dentry;
19
20 /* /sys/kernel/debug/acpi/custom_method */
21
cm_write(struct file * file,const char __user * user_buf,size_t count,loff_t * ppos)22 static 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
75 static const struct file_operations cm_fops = {
76 .write = cm_write,
77 .llseek = default_llseek,
78 };
79
acpi_custom_method_init(void)80 static 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
acpi_custom_method_exit(void)93 static void __exit acpi_custom_method_exit(void)
94 {
95 if (cm_dentry)
96 debugfs_remove(cm_dentry);
97 }
98
99 module_init(acpi_custom_method_init);
100 module_exit(acpi_custom_method_exit);
101
