/* 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);
  	/*
  	 * This implies unable to support free buddy pages.
  	 */
  	if (!get_page_unless_zero(hpage))
  		return 0;
  
  	if (!hwpoison_filter_enable)
  		goto inject;
  
  	if (!PageLRU(p) && !PageHuge(p))
  		shake_page(p, 0);
  	/*
  	 * This implies unable to support non-LRU pages.
  	 */
  	if (!PageLRU(p) && !PageHuge(p))
  		return 0;
  
  	/*
  	 * do a racy check with elevated page count, to make sure PG_hwpoison
  	 * will only be set for the targeted owner (or on a free page).
  	 * We temporarily take page lock for try_get_mem_cgroup_from_page().
  	 * memory_failure() will redo the check reliably inside page lock.
  	 */
  	lock_page(hpage);
  	err = hwpoison_filter(hpage);
  	unlock_page(hpage);
  	if (err)
  		return 0;
  
  inject:
  	pr_info("Injecting memory failure at pfn %#lx
  ", pfn);
  	return memory_failure(pfn, 18, MF_COUNT_INCREASED);
  }
  
  static int hwpoison_unpoison(void *data, u64 val)
  {
  	if (!capable(CAP_SYS_ADMIN))
  		return -EPERM;
  
  	return unpoison_memory(val);
  }
  
  DEFINE_SIMPLE_ATTRIBUTE(hwpoison_fops, NULL, hwpoison_inject, "%lli
  ");
  DEFINE_SIMPLE_ATTRIBUTE(unpoison_fops, NULL, hwpoison_unpoison, "%lli
  ");
  
  static void pfn_inject_exit(void)
  {
  	if (hwpoison_dir)
  		debugfs_remove_recursive(hwpoison_dir);
  }
  
  static int pfn_inject_init(void)
  {
  	struct dentry *dentry;
  
  	hwpoison_dir = debugfs_create_dir("hwpoison", NULL);
  	if (hwpoison_dir == NULL)
  		return -ENOMEM;
  
  	/*
  	 * 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.
  	 */
  	dentry = debugfs_create_file("corrupt-pfn", 0200, hwpoison_dir,
  					  NULL, &hwpoison_fops);
  	if (!dentry)
  		goto fail;
  
  	dentry = debugfs_create_file("unpoison-pfn", 0200, hwpoison_dir,
  				     NULL, &unpoison_fops);
  	if (!dentry)
  		goto fail;
  
  	dentry = debugfs_create_u32("corrupt-filter-enable", 0600,
  				    hwpoison_dir, &hwpoison_filter_enable);
  	if (!dentry)
  		goto fail;
  
  	dentry = debugfs_create_u32("corrupt-filter-dev-major", 0600,
  				    hwpoison_dir, &hwpoison_filter_dev_major);
  	if (!dentry)
  		goto fail;
  
  	dentry = debugfs_create_u32("corrupt-filter-dev-minor", 0600,
  				    hwpoison_dir, &hwpoison_filter_dev_minor);
  	if (!dentry)
  		goto fail;
  
  	dentry = debugfs_create_u64("corrupt-filter-flags-mask", 0600,
  				    hwpoison_dir, &hwpoison_filter_flags_mask);
  	if (!dentry)
  		goto fail;
  
  	dentry = debugfs_create_u64("corrupt-filter-flags-value", 0600,
  				    hwpoison_dir, &hwpoison_filter_flags_value);
  	if (!dentry)
  		goto fail;
  
  #ifdef CONFIG_MEMCG_SWAP
  	dentry = debugfs_create_u64("corrupt-filter-memcg", 0600,
  				    hwpoison_dir, &hwpoison_filter_memcg);
  	if (!dentry)
  		goto fail;
  #endif
  
  	return 0;
  fail:
  	pfn_inject_exit();
  	return -ENOMEM;
  }
  
  module_init(pfn_inject_init);
  module_exit(pfn_inject_exit);
  MODULE_LICENSE("GPL");