linux/drivers/acpi/custom_method.c
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   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 <acpi/acpi_drivers.h>
  11
  12#include "internal.h"
  13
  14#define _COMPONENT              ACPI_SYSTEM_COMPONENT
  15ACPI_MODULE_NAME("custom_method");
  16MODULE_LICENSE("GPL");
  17
  18static struct dentry *cm_dentry;
  19
  20/* /sys/kernel/debug/acpi/custom_method */
  21
  22static 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
  75static const struct file_operations cm_fops = {
  76        .write = cm_write,
  77        .llseek = default_llseek,
  78};
  79
  80static 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
  93static void __exit acpi_custom_method_exit(void)
  94{
  95        if (cm_dentry)
  96                debugfs_remove(cm_dentry);
  97 }
  98
  99module_init(acpi_custom_method_init);
 100module_exit(acpi_custom_method_exit);
 101
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