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// SPDX-License-Identifier: GPL-2.0-only
/*
* custom_method.c - debugfs interface for customizing ACPI control method
*/
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/uaccess.h>
#include <linux/debugfs.h>
#include <linux/acpi.h>
#include <linux/security.h>
#include "internal.h"
MODULE_LICENSE("GPL");
static struct dentry *cm_dentry;
/* /sys/kernel/debug/acpi/custom_method */
static ssize_t cm_write(struct file *file, const char __user *user_buf,
size_t count, loff_t *ppos)
{
static char *buf;
static u32 max_size;
static u32 uncopied_bytes;
struct acpi_table_header table;
acpi_status status;
int ret;
ret = security_locked_down(LOCKDOWN_ACPI_TABLES);
if (ret)
return ret;
if (!(*ppos)) {
/* parse the table header to get the table length */
if (count <= sizeof(struct acpi_table_header))
return -EINVAL;
if (copy_from_user(&table, user_buf,
sizeof(struct acpi_table_header)))
return -EFAULT;
uncopied_bytes = max_size = table.length;
/* make sure the buf is not allocated */
kfree(buf);
buf = kzalloc(max_size, GFP_KERNEL);
if (!buf)
return -ENOMEM;
}
if (buf == NULL)
return -EINVAL;
if ((*ppos > max_size) ||
(*ppos + count > max_size) ||
(*ppos + count < count) ||
(count > uncopied_bytes)) {
kfree(buf);
buf = NULL;
return -EINVAL;
}
if (copy_from_user(buf + (*ppos), user_buf, count)) {
kfree(buf);
buf = NULL;
return -EFAULT;
}
uncopied_bytes -= count;
*ppos += count;
if (!uncopied_bytes) {
status = acpi_install_method(buf);
kfree(buf);
buf = NULL;
if (ACPI_FAILURE(status))
return -EINVAL;
add_taint(TAINT_OVERRIDDEN_ACPI_TABLE, LOCKDEP_NOW_UNRELIABLE);
}
return count;
}
static const struct file_operations cm_fops = {
.write = cm_write,
.llseek = default_llseek,
};
static int __init acpi_custom_method_init(void)
{
cm_dentry = debugfs_create_file("custom_method", S_IWUSR,
acpi_debugfs_dir, NULL, &cm_fops);
return 0;
}
static void __exit acpi_custom_method_exit(void)
{
debugfs_remove(cm_dentry);
}
module_init(acpi_custom_method_init);
module_exit(acpi_custom_method_exit);
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