// SPDX-License-Identifier: GPL-2.0

  #include <linux/bootmem.h>
  #include <linux/compiler.h>
  #include <linux/fs.h>
  #include <linux/init.h>

  #include <linux/ksm.h>

  #include <linux/mm.h>
  #include <linux/mmzone.h>

  #include <linux/huge_mm.h>

  #include <linux/proc_fs.h>
  #include <linux/seq_file.h>

  #include <linux/hugetlb.h>

  #include <linux/memcontrol.h>

  #include <linux/mmu_notifier.h>
  #include <linux/page_idle.h>

  #include <linux/kernel-page-flags.h>

  #include <linux/uaccess.h>

  #include "internal.h"
  
  #define KPMSIZE sizeof(u64)
  #define KPMMASK (KPMSIZE - 1)

  #define KPMBITS (KPMSIZE * BITS_PER_BYTE)

  /* /proc/kpagecount - an array exposing page counts
   *
   * Each entry is a u64 representing the corresponding
   * physical page count.
   */
  static ssize_t kpagecount_read(struct file *file, char __user *buf,
  			     size_t count, loff_t *ppos)
  {
  	u64 __user *out = (u64 __user *)buf;
  	struct page *ppage;
  	unsigned long src = *ppos;
  	unsigned long pfn;
  	ssize_t ret = 0;
  	u64 pcount;
  
  	pfn = src / KPMSIZE;
  	count = min_t(size_t, count, (max_pfn * KPMSIZE) - src);
  	if (src & KPMMASK || count & KPMMASK)
  		return -EINVAL;
  
  	while (count > 0) {

  		if (pfn_valid(pfn))
  			ppage = pfn_to_page(pfn);

  		else
  			ppage = NULL;

  		if (!ppage || PageSlab(ppage))

  			pcount = 0;
  		else
  			pcount = page_mapcount(ppage);

  		if (put_user(pcount, out)) {

  			ret = -EFAULT;
  			break;
  		}

  		pfn++;
  		out++;

  		count -= KPMSIZE;

  
  		cond_resched();

  	}
  
  	*ppos += (char __user *)out - buf;
  	if (!ret)
  		ret = (char __user *)out - buf;
  	return ret;
  }
  
  static const struct file_operations proc_kpagecount_operations = {
  	.llseek = mem_lseek,
  	.read = kpagecount_read,
  };
  
  /* /proc/kpageflags - an array exposing page flags
   *
   * Each entry is a u64 representing the corresponding
   * physical page flags.
   */

  static inline u64 kpf_copy_bit(u64 kflags, int ubit, int kbit)
  {
  	return ((kflags >> kbit) & 1) << ubit;
  }

  u64 stable_page_flags(struct page *page)

  {
  	u64 k;
  	u64 u;
  
  	/*
  	 * pseudo flag: KPF_NOPAGE
  	 * it differentiates a memory hole from a page with no flags
  	 */
  	if (!page)
  		return 1 << KPF_NOPAGE;
  
  	k = page->flags;
  	u = 0;
  
  	/*
  	 * pseudo flags for the well known (anonymous) memory mapped pages
  	 *
  	 * Note that page->_mapcount is overloaded in SLOB/SLUB/SLQB, so the

  	 * simple test in page_mapped() is not enough.

  	 */

  	if (!PageSlab(page) && page_mapped(page))

  		u |= 1 << KPF_MMAP;
  	if (PageAnon(page))
  		u |= 1 << KPF_ANON;

  	if (PageKsm(page))
  		u |= 1 << KPF_KSM;

  
  	/*
  	 * compound pages: export both head/tail info
  	 * they together define a compound page's start/end pos and order
  	 */
  	if (PageHead(page))
  		u |= 1 << KPF_COMPOUND_HEAD;
  	if (PageTail(page))
  		u |= 1 << KPF_COMPOUND_TAIL;
  	if (PageHuge(page))
  		u |= 1 << KPF_HUGE;

  	/*
  	 * PageTransCompound can be true for non-huge compound pages (slab
  	 * pages or pages allocated by drivers with __GFP_COMP) because it

  	 * just checks PG_head/PG_tail, so we need to check PageLRU/PageAnon
  	 * to make sure a given page is a thp, not a non-huge compound page.

  	 */

  	else if (PageTransCompound(page)) {
  		struct page *head = compound_head(page);
  
  		if (PageLRU(head) || PageAnon(head))
  			u |= 1 << KPF_THP;
  		else if (is_huge_zero_page(head)) {
  			u |= 1 << KPF_ZERO_PAGE;
  			u |= 1 << KPF_THP;
  		}
  	} else if (is_zero_pfn(page_to_pfn(page)))
  		u |= 1 << KPF_ZERO_PAGE;

  	/*

  	 * Caveats on high order pages: page->_refcount will only be set

  	 * -1 on the head page; SLUB/SLQB do the same for PG_slab;
  	 * SLOB won't set PG_slab at all on compound pages.

  	 */

  	if (PageBuddy(page))
  		u |= 1 << KPF_BUDDY;

  	else if (page_count(page) == 0 && is_free_buddy_page(page))
  		u |= 1 << KPF_BUDDY;

  	if (PageBalloon(page))
  		u |= 1 << KPF_BALLOON;

  	if (page_is_idle(page))
  		u |= 1 << KPF_IDLE;

  	u |= kpf_copy_bit(k, KPF_LOCKED,	PG_locked);

  	u |= kpf_copy_bit(k, KPF_SLAB,		PG_slab);

  	if (PageTail(page) && PageSlab(compound_head(page)))
  		u |= 1 << KPF_SLAB;

  
  	u |= kpf_copy_bit(k, KPF_ERROR,		PG_error);
  	u |= kpf_copy_bit(k, KPF_DIRTY,		PG_dirty);
  	u |= kpf_copy_bit(k, KPF_UPTODATE,	PG_uptodate);
  	u |= kpf_copy_bit(k, KPF_WRITEBACK,	PG_writeback);
  
  	u |= kpf_copy_bit(k, KPF_LRU,		PG_lru);
  	u |= kpf_copy_bit(k, KPF_REFERENCED,	PG_referenced);
  	u |= kpf_copy_bit(k, KPF_ACTIVE,	PG_active);
  	u |= kpf_copy_bit(k, KPF_RECLAIM,	PG_reclaim);

  	if (PageSwapCache(page))
  		u |= 1 << KPF_SWAPCACHE;

  	u |= kpf_copy_bit(k, KPF_SWAPBACKED,	PG_swapbacked);

  	u |= kpf_copy_bit(k, KPF_UNEVICTABLE,	PG_unevictable);
  	u |= kpf_copy_bit(k, KPF_MLOCKED,	PG_mlocked);

  #ifdef CONFIG_MEMORY_FAILURE
  	u |= kpf_copy_bit(k, KPF_HWPOISON,	PG_hwpoison);
  #endif

  #ifdef CONFIG_ARCH_USES_PG_UNCACHED

  	u |= kpf_copy_bit(k, KPF_UNCACHED,	PG_uncached);
  #endif
  
  	u |= kpf_copy_bit(k, KPF_RESERVED,	PG_reserved);
  	u |= kpf_copy_bit(k, KPF_MAPPEDTODISK,	PG_mappedtodisk);
  	u |= kpf_copy_bit(k, KPF_PRIVATE,	PG_private);
  	u |= kpf_copy_bit(k, KPF_PRIVATE_2,	PG_private_2);
  	u |= kpf_copy_bit(k, KPF_OWNER_PRIVATE,	PG_owner_priv_1);
  	u |= kpf_copy_bit(k, KPF_ARCH,		PG_arch_1);
  
  	return u;
  };

  
  static ssize_t kpageflags_read(struct file *file, char __user *buf,
  			     size_t count, loff_t *ppos)
  {
  	u64 __user *out = (u64 __user *)buf;
  	struct page *ppage;
  	unsigned long src = *ppos;
  	unsigned long pfn;
  	ssize_t ret = 0;

  
  	pfn = src / KPMSIZE;
  	count = min_t(unsigned long, count, (max_pfn * KPMSIZE) - src);
  	if (src & KPMMASK || count & KPMMASK)
  		return -EINVAL;
  
  	while (count > 0) {

  		if (pfn_valid(pfn))
  			ppage = pfn_to_page(pfn);

  		else
  			ppage = NULL;

  		if (put_user(stable_page_flags(ppage), out)) {

  			ret = -EFAULT;
  			break;
  		}

  		pfn++;
  		out++;

  		count -= KPMSIZE;

  
  		cond_resched();

  	}
  
  	*ppos += (char __user *)out - buf;
  	if (!ret)
  		ret = (char __user *)out - buf;
  	return ret;
  }
  
  static const struct file_operations proc_kpageflags_operations = {
  	.llseek = mem_lseek,
  	.read = kpageflags_read,
  };

  #ifdef CONFIG_MEMCG
  static ssize_t kpagecgroup_read(struct file *file, char __user *buf,
  				size_t count, loff_t *ppos)
  {
  	u64 __user *out = (u64 __user *)buf;
  	struct page *ppage;
  	unsigned long src = *ppos;
  	unsigned long pfn;
  	ssize_t ret = 0;
  	u64 ino;
  
  	pfn = src / KPMSIZE;
  	count = min_t(unsigned long, count, (max_pfn * KPMSIZE) - src);
  	if (src & KPMMASK || count & KPMMASK)
  		return -EINVAL;
  
  	while (count > 0) {
  		if (pfn_valid(pfn))
  			ppage = pfn_to_page(pfn);
  		else
  			ppage = NULL;
  
  		if (ppage)
  			ino = page_cgroup_ino(ppage);
  		else
  			ino = 0;
  
  		if (put_user(ino, out)) {
  			ret = -EFAULT;
  			break;
  		}
  
  		pfn++;
  		out++;
  		count -= KPMSIZE;

  
  		cond_resched();

  	}
  
  	*ppos += (char __user *)out - buf;
  	if (!ret)
  		ret = (char __user *)out - buf;
  	return ret;
  }
  
  static const struct file_operations proc_kpagecgroup_operations = {
  	.llseek = mem_lseek,
  	.read = kpagecgroup_read,
  };
  #endif /* CONFIG_MEMCG */

  static int __init proc_page_init(void)
  {
  	proc_create("kpagecount", S_IRUSR, NULL, &proc_kpagecount_operations);
  	proc_create("kpageflags", S_IRUSR, NULL, &proc_kpageflags_operations);

  #ifdef CONFIG_MEMCG
  	proc_create("kpagecgroup", S_IRUSR, NULL, &proc_kpagecgroup_operations);
  #endif

  	return 0;
  }

  fs_initcall(proc_page_init);