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                 kfree(buf);
  54                 return -EINVAL;
  55         }
  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         kfree(buf);
  76         return count;
  77 }
  78
  79 static const struct file_operations cm_fops = {
  80         .write = cm_write,
  81         .llseek = default_llseek,
  82 };
  83
  84 static int __init acpi_custom_method_init(void)
  85 {
  86         cm_dentry = debugfs_create_file("custom_method", S_IWUSR,
  87                                         acpi_debugfs_dir, NULL, &cm_fops);
  88         return 0;
  89 }
  90
  91 static void __exit acpi_custom_method_exit(void)
  92 {
  93         debugfs_remove(cm_dentry);
  94 }
  95
  96 module_init(acpi_custom_method_init);
  97 module_exit(acpi_custom_method_exit);