// SPDX-License-Identifier: GPL-2.0-only

  /* Inject a hwpoison memory failure on a arbitrary pfn */

  #include <linux/module.h>
  #include <linux/debugfs.h>
  #include <linux/kernel.h>
  #include <linux/mm.h>

  #include <linux/swap.h>
  #include <linux/pagemap.h>

  #include <linux/hugetlb.h>

  #include "internal.h"

  static struct dentry *hwpoison_dir;

  
  static int hwpoison_inject(void *data, u64 val)
  {

  	unsigned long pfn = val;
  	struct page *p;

  	struct page *hpage;

  	int err;

  	if (!capable(CAP_SYS_ADMIN))
  		return -EPERM;

  
  	if (!pfn_valid(pfn))
  		return -ENXIO;
  
  	p = pfn_to_page(pfn);

  	hpage = compound_head(p);

  	if (!hwpoison_filter_enable)
  		goto inject;

  	shake_page(hpage, 0);

  	/*
  	 * This implies unable to support non-LRU pages.
  	 */

  	if (!PageLRU(hpage) && !PageHuge(p))

  		return 0;

  
  	/*

  	 * do a racy check to make sure PG_hwpoison will only be set for
  	 * the targeted owner (or on a free page).

  	 * memory_failure() will redo the check reliably inside page lock.

  	 */

  	err = hwpoison_filter(hpage);

  	if (err)

  		return 0;

  inject:

  	pr_info("Injecting memory failure at pfn %#lx
  ", pfn);

  	return memory_failure(pfn, 0);

  }

  static int hwpoison_unpoison(void *data, u64 val)
  {
  	if (!capable(CAP_SYS_ADMIN))
  		return -EPERM;
  
  	return unpoison_memory(val);
  }

  DEFINE_DEBUGFS_ATTRIBUTE(hwpoison_fops, NULL, hwpoison_inject, "%lli
  ");
  DEFINE_DEBUGFS_ATTRIBUTE(unpoison_fops, NULL, hwpoison_unpoison, "%lli
  ");

  
  static void pfn_inject_exit(void)
  {

  	debugfs_remove_recursive(hwpoison_dir);

  }
  
  static int pfn_inject_init(void)
  {
  	hwpoison_dir = debugfs_create_dir("hwpoison", NULL);

  
  	/*
  	 * Note that the below poison/unpoison interfaces do not involve
  	 * hardware status change, hence do not require hardware support.
  	 * They are mainly for testing hwpoison in software level.
  	 */

  	debugfs_create_file("corrupt-pfn", 0200, hwpoison_dir, NULL,
  			    &hwpoison_fops);
  
  	debugfs_create_file("unpoison-pfn", 0200, hwpoison_dir, NULL,
  			    &unpoison_fops);
  
  	debugfs_create_u32("corrupt-filter-enable", 0600, hwpoison_dir,
  			   &hwpoison_filter_enable);
  
  	debugfs_create_u32("corrupt-filter-dev-major", 0600, hwpoison_dir,
  			   &hwpoison_filter_dev_major);
  
  	debugfs_create_u32("corrupt-filter-dev-minor", 0600, hwpoison_dir,
  			   &hwpoison_filter_dev_minor);
  
  	debugfs_create_u64("corrupt-filter-flags-mask", 0600, hwpoison_dir,
  			   &hwpoison_filter_flags_mask);
  
  	debugfs_create_u64("corrupt-filter-flags-value", 0600, hwpoison_dir,
  			   &hwpoison_filter_flags_value);

  #ifdef CONFIG_MEMCG

  	debugfs_create_u64("corrupt-filter-memcg", 0600, hwpoison_dir,
  			   &hwpoison_filter_memcg);

  #endif

  	return 0;
  }
  
  module_init(pfn_inject_init);
  module_exit(pfn_inject_exit);
  MODULE_LICENSE("GPL");