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 (!(*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                 /* make sure the buf is not allocated */
  41                 kfree(buf);
  42                 buf = kzalloc(max_size, GFP_KERNEL);
  43                 if (!buf)
  44                         return -ENOMEM;
  45         }
  46
  47         if (buf == NULL)
  48                 return -EINVAL;
  49
  50         if ((*ppos > max_size) ||
  51             (*ppos + count > max_size) ||
  52             (*ppos + count < count) ||
  53             (count > uncopied_bytes)) {
  54                 kfree(buf);
  55                 buf = NULL;
  56                 return -EINVAL;
  57         }
  58
  59         if (copy_from_user(buf + (*ppos), user_buf, count)) {
  60                 kfree(buf);
  61                 buf = NULL;
  62                 return -EFAULT;
  63         }
  64
  65         uncopied_bytes -= count;
  66         *ppos += count;
  67
  68         if (!uncopied_bytes) {
  69                 status = acpi_install_method(buf);
  70                 kfree(buf);
  71                 buf = NULL;
  72                 if (ACPI_FAILURE(status))
  73                         return -EINVAL;
  74                 add_taint(TAINT_OVERRIDDEN_ACPI_TABLE, LOCKDEP_NOW_UNRELIABLE);
  75         }
  76
  77         return count;
  78 }
  79
  80 static const struct file_operations cm_fops = {
  81         .write = cm_write,
  82         .llseek = default_llseek,
  83 };
  84
  85 static int __init acpi_custom_method_init(void)
  86 {
  87         if (acpi_debugfs_dir == NULL)
  88                 return -ENOENT;
  89
  90         cm_dentry = debugfs_create_file("custom_method", S_IWUSR,
  91                                         acpi_debugfs_dir, NULL, &cm_fops);
  92         if (cm_dentry == NULL)
  93                 return -ENODEV;
  94
  95         return 0;
  96 }
  97
  98 static void __exit acpi_custom_method_exit(void)
  99 {
 100         if (cm_dentry)
 101                 debugfs_remove(cm_dentry);
 102  }
 103
 104 module_init(acpi_custom_method_init);
 105 module_exit(acpi_custom_method_exit);