drivers/acpi/custom_method.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * custom_method.c - debugfs interface for customizing ACPI control method
   4  */
   5
   6 #include <linux/init.h>
   7 #include <linux/module.h>
   8 #include <linux/kernel.h>
   9 #include <linux/uaccess.h>
  10 #include <linux/debugfs.h>
  11 #include <linux/acpi.h>
  12
  13 #include "internal.h"
  14
  15 #define _COMPONENT              ACPI_SYSTEM_COMPONENT
  16 ACPI_MODULE_NAME("custom_method");
  17 MODULE_LICENSE("GPL");
  18
  19 static struct dentry *cm_dentry;
  20
  21 /* /sys/kernel/debug/acpi/custom_method */
  22
  23 static ssize_t cm_write(struct file *file, const char __user * user_buf,
  24                         size_t count, loff_t *ppos)
  25 {
  26         static char *buf;
  27         static u32 max_size;
  28         static u32 uncopied_bytes;
  29
  30         struct acpi_table_header table;
  31         acpi_status status;
  32
  33         if (!(*ppos)) {
  34                 /* parse the table header to get the table length */
  35                 if (count <= sizeof(struct acpi_table_header))
  36                         return -EINVAL;
  37                 if (copy_from_user(&table, user_buf,
  38                                    sizeof(struct acpi_table_header)))
  39                         return -EFAULT;
  40                 uncopied_bytes = max_size = table.length;
  41                 buf = kzalloc(max_size, GFP_KERNEL);
  42                 if (!buf)
  43                         return -ENOMEM;
  44         }
  45
  46         if (buf == NULL)
  47                 return -EINVAL;
  48
  49         if ((*ppos > max_size) ||
  50             (*ppos + count > max_size) ||
  51             (*ppos + count < count) ||
  52             (count > uncopied_bytes))
  53                 return -EINVAL;
  54
  55         if (copy_from_user(buf + (*ppos), user_buf, count)) {
  56                 kfree(buf);
  57                 buf = NULL;
  58                 return -EFAULT;
  59         }
  60
  61         uncopied_bytes -= count;
  62         *ppos += count;
  63
  64         if (!uncopied_bytes) {
  65                 status = acpi_install_method(buf);
  66                 kfree(buf);
  67                 buf = NULL;
  68                 if (ACPI_FAILURE(status))
  69                         return -EINVAL;
  70                 add_taint(TAINT_OVERRIDDEN_ACPI_TABLE, LOCKDEP_NOW_UNRELIABLE);
  71         }
  72
  73         return count;
  74 }
  75
  76 static const struct file_operations cm_fops = {
  77         .write = cm_write,
  78         .llseek = default_llseek,
  79 };
  80
  81 static int __init acpi_custom_method_init(void)
  82 {
  83         cm_dentry = debugfs_create_file("custom_method", S_IWUSR,
  84                                         acpi_debugfs_dir, NULL, &cm_fops);
  85         return 0;
  86 }
  87
  88 static void __exit acpi_custom_method_exit(void)
  89 {
  90         debugfs_remove(cm_dentry);
  91 }
  92
  93 module_init(acpi_custom_method_init);
  94 module_exit(acpi_custom_method_exit);