drivers/acpi/custom_method.c

   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
  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 (kernel_is_locked_down("ACPI custom methods"))
  33                 return -EPERM;
  34
  35         if (!(*ppos)) {
  36                 /* parse the table header to get the table length */
  37                 if (count <= sizeof(struct acpi_table_header))
  38                         return -EINVAL;
  39                 if (copy_from_user(&table, user_buf,
  40                                    sizeof(struct acpi_table_header)))
  41                         return -EFAULT;
  42                 uncopied_bytes = max_size = table.length;
  43                 buf = kzalloc(max_size, GFP_KERNEL);
  44                 if (!buf)
  45                         return -ENOMEM;
  46         }
  47
  48         if (buf == NULL)
  49                 return -EINVAL;
  50
  51         if ((*ppos > max_size) ||
  52             (*ppos + count > max_size) ||
  53             (*ppos + count < count) ||
  54             (count > uncopied_bytes))
  55                 return -EINVAL;
  56
  57         if (copy_from_user(buf + (*ppos), user_buf, count)) {
  58                 kfree(buf);
  59                 buf = NULL;
  60                 return -EFAULT;
  61         }
  62
  63         uncopied_bytes -= count;
  64         *ppos += count;
  65
  66         if (!uncopied_bytes) {
  67                 status = acpi_install_method(buf);
  68                 kfree(buf);
  69                 buf = NULL;
  70                 if (ACPI_FAILURE(status))
  71                         return -EINVAL;
  72                 add_taint(TAINT_OVERRIDDEN_ACPI_TABLE, LOCKDEP_NOW_UNRELIABLE);
  73         }
  74
  75         return count;
  76 }
  77
  78 static const struct file_operations cm_fops = {
  79         .write = cm_write,
  80         .llseek = default_llseek,
  81 };
  82
  83 static int __init acpi_custom_method_init(void)
  84 {
  85         if (acpi_debugfs_dir == NULL)
  86                 return -ENOENT;
  87
  88         cm_dentry = debugfs_create_file("custom_method", S_IWUSR,
  89                                         acpi_debugfs_dir, NULL, &cm_fops);
  90         if (cm_dentry == NULL)
  91                 return -ENODEV;
  92
  93         return 0;
  94 }
  95
  96 static void __exit acpi_custom_method_exit(void)
  97 {
  98         if (cm_dentry)
  99                 debugfs_remove(cm_dentry);
 100  }
 101
 102 module_init(acpi_custom_method_init);
 103 module_exit(acpi_custom_method_exit);