text: #include <linux/mm.h>
  #include <linux/vmacache.h>
  #include <linux/hugetlb.h>
  #include <linux/huge_mm.h>
  #include <linux/mount.h>
  #include <linux/seq_file.h>
  #include <linux/highmem.h>
  #include <linux/ptrace.h>
  #include <linux/slab.h>
  #include <linux/pagemap.h>
  #include <linux/mempolicy.h>
  #include <linux/rmap.h>
  #include <linux/swap.h>
  #include <linux/swapops.h>
  #include <linux/mmu_notifier.h>
  #include <linux/page_idle.h>
  #include <linux/shmem_fs.h>
  
  #include <asm/elf.h>
  #include <asm/uaccess.h>
  #include <asm/tlbflush.h>
  #include "internal.h"
  
  void task_mem(struct seq_file *m, struct mm_struct *mm)
  {
  	unsigned long text, lib, swap, ptes, pmds, anon, file, shmem;
  	unsigned long hiwater_vm, total_vm, hiwater_rss, total_rss;
  
  	anon = get_mm_counter(mm, MM_ANONPAGES);
  	file = get_mm_counter(mm, MM_FILEPAGES);
  	shmem = get_mm_counter(mm, MM_SHMEMPAGES);
  
  	/*
  	 * Note: to minimize their overhead, mm maintains hiwater_vm and
  	 * hiwater_rss only when about to *lower* total_vm or rss.  Any
  	 * collector of these hiwater stats must therefore get total_vm
  	 * and rss too, which will usually be the higher.  Barriers? not
  	 * worth the effort, such snapshots can always be inconsistent.
  	 */
  	hiwater_vm = total_vm = mm->total_vm;
  	if (hiwater_vm < mm->hiwater_vm)
  		hiwater_vm = mm->hiwater_vm;
  	hiwater_rss = total_rss = anon + file + shmem;
  	if (hiwater_rss < mm->hiwater_rss)
  		hiwater_rss = mm->hiwater_rss;
  
  	text = (PAGE_ALIGN(mm->end_code) - (mm->start_code & PAGE_MASK)) >> 10;
  	lib = (mm->exec_vm << (PAGE_SHIFT-10)) - text;
  	swap = get_mm_counter(mm, MM_SWAPENTS);
  	ptes = PTRS_PER_PTE * sizeof(pte_t) * atomic_long_read(&mm->nr_ptes);
  	pmds = PTRS_PER_PMD * sizeof(pmd_t) * mm_nr_pmds(mm);
  	seq_printf(m,
  		"VmPeak:\t%8lu kB\n"
  		"VmSize:\t%8lu kB\n"
  		"VmLck:\t%8lu kB\n"
  		"VmPin:\t%8lu kB\n"
  		"VmHWM:\t%8lu kB\n"
  		"VmRSS:\t%8lu kB\n"
  		"RssAnon:\t%8lu kB\n"
  		"RssFile:\t%8lu kB\n"
  		"RssShmem:\t%8lu kB\n"
  		"VmData:\t%8lu kB\n"
  		"VmStk:\t%8lu kB\n"
  		"VmExe:\t%8lu kB\n"
  		"VmLib:\t%8lu kB\n"
  		"VmPTE:\t%8lu kB\n"
  		"VmPMD:\t%8lu kB\n"
  		"VmSwap:\t%8lu kB\n",
  		hiwater_vm << (PAGE_SHIFT-10),
  		total_vm << (PAGE_SHIFT-10),
  		mm->locked_vm << (PAGE_SHIFT-10),
  		mm->pinned_vm << (PAGE_SHIFT-10),
  		hiwater_rss << (PAGE_SHIFT-10),
  		total_rss << (PAGE_SHIFT-10),
  		anon << (PAGE_SHIFT-10),
  		file << (PAGE_SHIFT-10),
  		shmem << (PAGE_SHIFT-10),
  		mm->data_vm << (PAGE_SHIFT-10),
  		mm->stack_vm << (PAGE_SHIFT-10), text, lib,
  		ptes >> 10,
  		pmds >> 10,
  		swap << (PAGE_SHIFT-10));
  	hugetlb_report_usage(m, mm);
  }
  
  unsigned long task_vsize(struct mm_struct *mm)
  {
  	return PAGE_SIZE * mm->total_vm;
  }
  
  unsigned long task_statm(struct mm_struct *mm,
  			 unsigned long *shared, unsigned long *text,
  			 unsigned long *data, unsigned long *resident)
  {
  	*shared = get_mm_counter(mm, MM_FILEPAGES) +
  			get_mm_counter(mm, MM_SHMEMPAGES);
  	*text = (PAGE_ALIGN(mm->end_code) - (mm->start_code & PAGE_MASK))
  								>> PAGE_SHIFT;
  	*data = mm->data_vm + mm->stack_vm;
  	*resident = *shared + get_mm_counter(mm, MM_ANONPAGES);
  	return mm->total_vm;
  }
  
  #ifdef CONFIG_NUMA
  /*
   * Save get_task_policy() for show_numa_map().
   */
  static void hold_task_mempolicy(struct proc_maps_private *priv)
  {
  	struct task_struct *task = priv->task;
  
  	task_lock(task);
  	priv->task_mempolicy = get_task_policy(task);
  	mpol_get(priv->task_mempolicy);
  	task_unlock(task);
  }
  static void release_task_mempolicy(struct proc_maps_private *priv)
  {
  	mpol_put(priv->task_mempolicy);
  }
  #else
  static void hold_task_mempolicy(struct proc_maps_private *priv)
  {
  }
  static void release_task_mempolicy(struct proc_maps_private *priv)
  {
  }
  #endif
  
  static void vma_stop(struct proc_maps_private *priv)
  {
  	struct mm_struct *mm = priv->mm;
  
  	release_task_mempolicy(priv);
  	up_read(&mm->mmap_sem);
  	mmput(mm);
  }
  
  static struct vm_area_struct *
  m_next_vma(struct proc_maps_private *priv, struct vm_area_struct *vma)
  {
  	if (vma == priv->tail_vma)
  		return NULL;
  	return vma->vm_next ?: priv->tail_vma;
  }
  
  static void m_cache_vma(struct seq_file *m, struct vm_area_struct *vma)
  {
  	if (m->count < m->size)	/* vma is copied successfully */
  		m->version = m_next_vma(m->private, vma) ? vma->vm_end : -1UL;
  }
  
  static void *m_start(struct seq_file *m, loff_t *ppos)
  {
  	struct proc_maps_private *priv = m->private;
  	unsigned long last_addr = m->version;
  	struct mm_struct *mm;
  	struct vm_area_struct *vma;
  	unsigned int pos = *ppos;
  
  	/* See m_cache_vma(). Zero at the start or after lseek. */
  	if (last_addr == -1UL)
  		return NULL;
  
  	priv->task = get_proc_task(priv->inode);
  	if (!priv->task)
  		return ERR_PTR(-ESRCH);
  
  	mm = priv->mm;
  	if (!mm || !atomic_inc_not_zero(&mm->mm_users))
  		return NULL;
  
  	down_read(&mm->mmap_sem);
  	hold_task_mempolicy(priv);
  	priv->tail_vma = get_gate_vma(mm);
  
  	if (last_addr) {
  		vma = find_vma(mm, last_addr - 1);
  		if (vma && vma->vm_start <= last_addr)
  			vma = m_next_vma(priv, vma);
  		if (vma)
  			return vma;
  	}
  
  	m->version = 0;
  	if (pos < mm->map_count) {
  		for (vma = mm->mmap; pos; pos--) {
  			m->version = vma->vm_start;
  			vma = vma->vm_next;
  		}
  		return vma;
  	}
  
  	/* we do not bother to update m->version in this case */
  	if (pos == mm->map_count && priv->tail_vma)
  		return priv->tail_vma;
  
  	vma_stop(priv);
  	return NULL;
  }
  
  static void *m_next(struct seq_file *m, void *v, loff_t *pos)
  {
  	struct proc_maps_private *priv = m->private;
  	struct vm_area_struct *next;
  
  	(*pos)++;
  	next = m_next_vma(priv, v);
  	if (!next)
  		vma_stop(priv);
  	return next;
  }
  
  static void m_stop(struct seq_file *m, void *v)
  {
  	struct proc_maps_private *priv = m->private;
  
  	if (!IS_ERR_OR_NULL(v))
  		vma_stop(priv);
  	if (priv->task) {
  		put_task_struct(priv->task);
  		priv->task = NULL;
  	}
  }
  
  static int proc_maps_open(struct inode *inode, struct file *file,
  			const struct seq_operations *ops, int psize)
  {
  	struct proc_maps_private *priv = __seq_open_private(file, ops, psize);
  
  	if (!priv)
  		return -ENOMEM;
  
  	priv->inode = inode;
  	priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
  	if (IS_ERR(priv->mm)) {
  		int err = PTR_ERR(priv->mm);
  
  		seq_release_private(inode, file);
  		return err;
  	}
  
  	return 0;
  }
  
  static int proc_map_release(struct inode *inode, struct file *file)
  {
  	struct seq_file *seq = file->private_data;
  	struct proc_maps_private *priv = seq->private;
  
  	if (priv->mm)
  		mmdrop(priv->mm);
  
  	return seq_release_private(inode, file);
  }
  
  static int do_maps_open(struct inode *inode, struct file *file,
  			const struct seq_operations *ops)
  {
  	return proc_maps_open(inode, file, ops,
  				sizeof(struct proc_maps_private));
  }
  
  /*
   * Indicate if the VMA is a stack for the given task; for
   * /proc/PID/maps that is the stack of the main task.
   */
  static int is_stack(struct proc_maps_private *priv,
  		    struct vm_area_struct *vma)
  {
  	/*
  	 * We make no effort to guess what a given thread considers to be
  	 * its "stack".  It's not even well-defined for programs written
  	 * languages like Go.
  	 */
  	return vma->vm_start <= vma->vm_mm->start_stack &&
  		vma->vm_end >= vma->vm_mm->start_stack;
  }
  
  static void
  show_map_vma(struct seq_file *m, struct vm_area_struct *vma, int is_pid)
  {
  	struct mm_struct *mm = vma->vm_mm;
  	struct file *file = vma->vm_file;
  	struct proc_maps_private *priv = m->private;
  	vm_flags_t flags = vma->vm_flags;
  	unsigned long ino = 0;
  	unsigned long long pgoff = 0;
  	unsigned long start, end;
  	dev_t dev = 0;
  	const char *name = NULL;
  
  	if (file) {
  		struct inode *inode = file_inode(vma->vm_file);
  		dev = inode->i_sb->s_dev;
  		ino = inode->i_ino;
  		pgoff = ((loff_t)vma->vm_pgoff) << PAGE_SHIFT;
  	}
  
  	/* We don't show the stack guard page in /proc/maps */
  	start = vma->vm_start;
  	if (stack_guard_page_start(vma, start))
  		start += PAGE_SIZE;
  	end = vma->vm_end;
  	if (stack_guard_page_end(vma, end))
  		end -= PAGE_SIZE;
  
  	seq_setwidth(m, 25 + sizeof(void *) * 6 - 1);
  	seq_printf(m, "%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu ",
  			start,
  			end,
  			flags & VM_READ ? 'r' : '-',
  			flags & VM_WRITE ? 'w' : '-',
  			flags & VM_EXEC ? 'x' : '-',
  			flags & VM_MAYSHARE ? 's' : 'p',
  			pgoff,
  			MAJOR(dev), MINOR(dev), ino);
  
  	/*
  	 * Print the dentry name for named mappings, and a
  	 * special [heap] marker for the heap:
  	 */
  	if (file) {
  		seq_pad(m, ' ');
  		seq_file_path(m, file, "\n");
  		goto done;
  	}
  
  	if (vma->vm_ops && vma->vm_ops->name) {
  		name = vma->vm_ops->name(vma);
  		if (name)
  			goto done;
  	}
  
  	name = arch_vma_name(vma);
  	if (!name) {
  		if (!mm) {
  			name = "[vdso]";
  			goto done;
  		}
  
  		if (vma->vm_start <= mm->brk &&
  		    vma->vm_end >= mm->start_brk) {
  			name = "[heap]";
  			goto done;
  		}
  
  		if (is_stack(priv, vma))
  			name = "[stack]";
  	}
  
  done:
  	if (name) {
  		seq_pad(m, ' ');
  		seq_puts(m, name);
  	}
  	seq_putc(m, '\n');
  }
  
  static int show_map(struct seq_file *m, void *v, int is_pid)
  {
  	show_map_vma(m, v, is_pid);
  	m_cache_vma(m, v);
  	return 0;
  }
  
  static int show_pid_map(struct seq_file *m, void *v)
  {
  	return show_map(m, v, 1);
  }
  
  static int show_tid_map(struct seq_file *m, void *v)
  {
  	return show_map(m, v, 0);
  }
  
  static const struct seq_operations proc_pid_maps_op = {
  	.start	= m_start,
  	.next	= m_next,
  	.stop	= m_stop,
  	.show	= show_pid_map
  };
  
  static const struct seq_operations proc_tid_maps_op = {
  	.start	= m_start,
  	.next	= m_next,
  	.stop	= m_stop,
  	.show	= show_tid_map
  };
  
  static int pid_maps_open(struct inode *inode, struct file *file)
  {
  	return do_maps_open(inode, file, &proc_pid_maps_op);
  }
  
  static int tid_maps_open(struct inode *inode, struct file *file)
  {
  	return do_maps_open(inode, file, &proc_tid_maps_op);
  }
  
  const struct file_operations proc_pid_maps_operations = {
  	.open		= pid_maps_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= proc_map_release,
  };
  
  const struct file_operations proc_tid_maps_operations = {
  	.open		= tid_maps_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= proc_map_release,
  };
  
  /*
   * Proportional Set Size(PSS): my share of RSS.
   *
   * PSS of a process is the count of pages it has in memory, where each
   * page is divided by the number of processes sharing it.  So if a
   * process has 1000 pages all to itself, and 1000 shared with one other
   * process, its PSS will be 1500.
   *
   * To keep (accumulated) division errors low, we adopt a 64bit
   * fixed-point pss counter to minimize division errors. So (pss >>
   * PSS_SHIFT) would be the real byte count.
   *
   * A shift of 12 before division means (assuming 4K page size):
   * 	- 1M 3-user-pages add up to 8KB errors;
   * 	- supports mapcount up to 2^24, or 16M;
   * 	- supports PSS up to 2^52 bytes, or 4PB.
   */
  #define PSS_SHIFT 12
  
  #ifdef CONFIG_PROC_PAGE_MONITOR
  struct mem_size_stats {
  	unsigned long resident;
  	unsigned long shared_clean;
  	unsigned long shared_dirty;
  	unsigned long private_clean;
  	unsigned long private_dirty;
  	unsigned long referenced;
  	unsigned long anonymous;
  	unsigned long anonymous_thp;
  	unsigned long shmem_thp;
  	unsigned long swap;
  	unsigned long shared_hugetlb;
  	unsigned long private_hugetlb;
  	u64 pss;
  	u64 swap_pss;
  	bool check_shmem_swap;
  };
  
  static void smaps_account(struct mem_size_stats *mss, struct page *page,
  		bool compound, bool young, bool dirty)
  {
  	int i, nr = compound ? 1 << compound_order(page) : 1;
  	unsigned long size = nr * PAGE_SIZE;
  
  	if (PageAnon(page))
  		mss->anonymous += size;
  
  	mss->resident += size;
  	/* Accumulate the size in pages that have been accessed. */
  	if (young || page_is_young(page) || PageReferenced(page))
  		mss->referenced += size;
  
  	/*
  	 * page_count(page) == 1 guarantees the page is mapped exactly once.
  	 * If any subpage of the compound page mapped with PTE it would elevate
  	 * page_count().
  	 */
  	if (page_count(page) == 1) {
  		if (dirty || PageDirty(page))
  			mss->private_dirty += size;
  		else
  			mss->private_clean += size;
  		mss->pss += (u64)size << PSS_SHIFT;
  		return;
  	}
  
  	for (i = 0; i < nr; i++, page++) {
  		int mapcount = page_mapcount(page);
  
  		if (mapcount >= 2) {
  			if (dirty || PageDirty(page))
  				mss->shared_dirty += PAGE_SIZE;
  			else
  				mss->shared_clean += PAGE_SIZE;
  			mss->pss += (PAGE_SIZE << PSS_SHIFT) / mapcount;
  		} else {
  			if (dirty || PageDirty(page))
  				mss->private_dirty += PAGE_SIZE;
  			else
  				mss->private_clean += PAGE_SIZE;
  			mss->pss += PAGE_SIZE << PSS_SHIFT;
  		}
  	}
  }
  
  #ifdef CONFIG_SHMEM
  static int smaps_pte_hole(unsigned long addr, unsigned long end,
  		struct mm_walk *walk)
  {
  	struct mem_size_stats *mss = walk->private;
  
  	mss->swap += shmem_partial_swap_usage(
  			walk->vma->vm_file->f_mapping, addr, end);
  
  	return 0;
  }
  #endif
  
  static void smaps_pte_entry(pte_t *pte, unsigned long addr,
  		struct mm_walk *walk)
  {
  	struct mem_size_stats *mss = walk->private;
  	struct vm_area_struct *vma = walk->vma;
  	struct page *page = NULL;
  
  	if (pte_present(*pte)) {
  		page = vm_normal_page(vma, addr, *pte);
  	} else if (is_swap_pte(*pte)) {
  		swp_entry_t swpent = pte_to_swp_entry(*pte);
  
  		if (!non_swap_entry(swpent)) {
  			int mapcount;
  
  			mss->swap += PAGE_SIZE;
  			mapcount = swp_swapcount(swpent);
  			if (mapcount >= 2) {
  				u64 pss_delta = (u64)PAGE_SIZE << PSS_SHIFT;
  
  				do_div(pss_delta, mapcount);
  				mss->swap_pss += pss_delta;
  			} else {
  				mss->swap_pss += (u64)PAGE_SIZE << PSS_SHIFT;
  			}
  		} else if (is_migration_entry(swpent))
  			page = migration_entry_to_page(swpent);
  	} else if (unlikely(IS_ENABLED(CONFIG_SHMEM) && mss->check_shmem_swap
  							&& pte_none(*pte))) {
  		page = find_get_entry(vma->vm_file->f_mapping,
  						linear_page_index(vma, addr));
  		if (!page)
  			return;
  
  		if (radix_tree_exceptional_entry(page))
  			mss->swap += PAGE_SIZE;
  		else
  			put_page(page);
  
  		return;
  	}
  
  	if (!page)
  		return;
  
  	smaps_account(mss, page, false, pte_young(*pte), pte_dirty(*pte));
  }
  
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
  		struct mm_walk *walk)
  {
  	struct mem_size_stats *mss = walk->private;
  	struct vm_area_struct *vma = walk->vma;
  	struct page *page;
  
  	/* FOLL_DUMP will return -EFAULT on huge zero page */
  	page = follow_trans_huge_pmd(vma, addr, pmd, FOLL_DUMP);
  	if (IS_ERR_OR_NULL(page))
  		return;
  	if (PageAnon(page))
  		mss->anonymous_thp += HPAGE_PMD_SIZE;
  	else if (PageSwapBacked(page))
  		mss->shmem_thp += HPAGE_PMD_SIZE;
  	else if (is_zone_device_page(page))
  		/* pass */;
  	else
  		VM_BUG_ON_PAGE(1, page);
  	smaps_account(mss, page, true, pmd_young(*pmd), pmd_dirty(*pmd));
  }
  #else
  static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
  		struct mm_walk *walk)
  {
  }
  #endif
  
  static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
  			   struct mm_walk *walk)
  {
  	struct vm_area_struct *vma = walk->vma;
  	pte_t *pte;
  	spinlock_t *ptl;
  
  	ptl = pmd_trans_huge_lock(pmd, vma);
  	if (ptl) {
  		smaps_pmd_entry(pmd, addr, walk);
  		spin_unlock(ptl);
  		return 0;
  	}
  
  	if (pmd_trans_unstable(pmd))
  		return 0;
  	/*
  	 * The mmap_sem held all the way back in m_start() is what
  	 * keeps khugepaged out of here and from collapsing things
  	 * in here.
  	 */
  	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
  	for (; addr != end; pte++, addr += PAGE_SIZE)
  		smaps_pte_entry(pte, addr, walk);
  	pte_unmap_unlock(pte - 1, ptl);
  	cond_resched();
  	return 0;
  }
  
  static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
  {
  	/*
  	 * Don't forget to update Documentation/ on changes.
  	 */
  	static const char mnemonics[BITS_PER_LONG][2] = {
  		/*
  		 * In case if we meet a flag we don't know about.
  		 */
  		[0 ... (BITS_PER_LONG-1)] = "??",
  
  		[ilog2(VM_READ)]	= "rd",
  		[ilog2(VM_WRITE)]	= "wr",
  		[ilog2(VM_EXEC)]	= "ex",
  		[ilog2(VM_SHARED)]	= "sh",
  		[ilog2(VM_MAYREAD)]	= "mr",
  		[ilog2(VM_MAYWRITE)]	= "mw",
  		[ilog2(VM_MAYEXEC)]	= "me",
  		[ilog2(VM_MAYSHARE)]	= "ms",
  		[ilog2(VM_GROWSDOWN)]	= "gd",
  		[ilog2(VM_PFNMAP)]	= "pf",
  		[ilog2(VM_DENYWRITE)]	= "dw",
  #ifdef CONFIG_X86_INTEL_MPX
  		[ilog2(VM_MPX)]		= "mp",
  #endif
  		[ilog2(VM_LOCKED)]	= "lo",
  		[ilog2(VM_IO)]		= "io",
  		[ilog2(VM_SEQ_READ)]	= "sr",
  		[ilog2(VM_RAND_READ)]	= "rr",
  		[ilog2(VM_DONTCOPY)]	= "dc",
  		[ilog2(VM_DONTEXPAND)]	= "de",
  		[ilog2(VM_ACCOUNT)]	= "ac",
  		[ilog2(VM_NORESERVE)]	= "nr",
  		[ilog2(VM_HUGETLB)]	= "ht",
  		[ilog2(VM_ARCH_1)]	= "ar",
  		[ilog2(VM_DONTDUMP)]	= "dd",
  #ifdef CONFIG_MEM_SOFT_DIRTY
  		[ilog2(VM_SOFTDIRTY)]	= "sd",
  #endif
  		[ilog2(VM_MIXEDMAP)]	= "mm",
  		[ilog2(VM_HUGEPAGE)]	= "hg",
  		[ilog2(VM_NOHUGEPAGE)]	= "nh",
  		[ilog2(VM_MERGEABLE)]	= "mg",
  		[ilog2(VM_UFFD_MISSING)]= "um",
  		[ilog2(VM_UFFD_WP)]	= "uw",
  #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
  		/* These come out via ProtectionKey: */
  		[ilog2(VM_PKEY_BIT0)]	= "",
  		[ilog2(VM_PKEY_BIT1)]	= "",
  		[ilog2(VM_PKEY_BIT2)]	= "",
  		[ilog2(VM_PKEY_BIT3)]	= "",
  #endif
  	};
  	size_t i;
  
  	seq_puts(m, "VmFlags: ");
  	for (i = 0; i < BITS_PER_LONG; i++) {
  		if (!mnemonics[i][0])
  			continue;
  		if (vma->vm_flags & (1UL << i)) {
  			seq_printf(m, "%c%c ",
  				   mnemonics[i][0], mnemonics[i][1]);
  		}
  	}
  	seq_putc(m, '\n');
  }
  
  #ifdef CONFIG_HUGETLB_PAGE
  static int smaps_hugetlb_range(pte_t *pte, unsigned long hmask,
  				 unsigned long addr, unsigned long end,
  				 struct mm_walk *walk)
  {
  	struct mem_size_stats *mss = walk->private;
  	struct vm_area_struct *vma = walk->vma;
  	struct page *page = NULL;
  
  	if (pte_present(*pte)) {
  		page = vm_normal_page(vma, addr, *pte);
  	} else if (is_swap_pte(*pte)) {
  		swp_entry_t swpent = pte_to_swp_entry(*pte);
  
  		if (is_migration_entry(swpent))
  			page = migration_entry_to_page(swpent);
  	}
  	if (page) {
  		int mapcount = page_mapcount(page);
  
  		if (mapcount >= 2)
  			mss->shared_hugetlb += huge_page_size(hstate_vma(vma));
  		else
  			mss->private_hugetlb += huge_page_size(hstate_vma(vma));
  	}
  	return 0;
  }
  #endif /* HUGETLB_PAGE */
  
  void __weak arch_show_smap(struct seq_file *m, struct vm_area_struct *vma)
  {
  }
  
  static int show_smap(struct seq_file *m, void *v, int is_pid)
  {
  	struct vm_area_struct *vma = v;
  	struct mem_size_stats mss;
  	struct mm_walk smaps_walk = {
  		.pmd_entry = smaps_pte_range,
  #ifdef CONFIG_HUGETLB_PAGE
  		.hugetlb_entry = smaps_hugetlb_range,
  #endif
  		.mm = vma->vm_mm,
  		.private = &mss,
  	};
  
  	memset(&mss, 0, sizeof mss);
  
  #ifdef CONFIG_SHMEM
  	if (vma->vm_file && shmem_mapping(vma->vm_file->f_mapping)) {
  		/*
  		 * For shared or readonly shmem mappings we know that all
  		 * swapped out pages belong to the shmem object, and we can
  		 * obtain the swap value much more efficiently. For private
  		 * writable mappings, we might have COW pages that are
  		 * not affected by the parent swapped out pages of the shmem
  		 * object, so we have to distinguish them during the page walk.
  		 * Unless we know that the shmem object (or the part mapped by
  		 * our VMA) has no swapped out pages at all.
  		 */
  		unsigned long shmem_swapped = shmem_swap_usage(vma);
  
  		if (!shmem_swapped || (vma->vm_flags & VM_SHARED) ||
  					!(vma->vm_flags & VM_WRITE)) {
  			mss.swap = shmem_swapped;
  		} else {
  			mss.check_shmem_swap = true;
  			smaps_walk.pte_hole = smaps_pte_hole;
  		}
  	}
  #endif
  
  	/* mmap_sem is held in m_start */
  	walk_page_vma(vma, &smaps_walk);
  
  	show_map_vma(m, vma, is_pid);
  
  	seq_printf(m,
  		   "Size:           %8lu kB\n"
  		   "Rss:            %8lu kB\n"
  		   "Pss:            %8lu kB\n"
  		   "Shared_Clean:   %8lu kB\n"
  		   "Shared_Dirty:   %8lu kB\n"
  		   "Private_Clean:  %8lu kB\n"
  		   "Private_Dirty:  %8lu kB\n"
  		   "Referenced:     %8lu kB\n"
  		   "Anonymous:      %8lu kB\n"
  		   "AnonHugePages:  %8lu kB\n"
  		   "ShmemPmdMapped: %8lu kB\n"
  		   "Shared_Hugetlb: %8lu kB\n"
  		   "Private_Hugetlb: %7lu kB\n"
  		   "Swap:           %8lu kB\n"
  		   "SwapPss:        %8lu kB\n"
  		   "KernelPageSize: %8lu kB\n"
  		   "MMUPageSize:    %8lu kB\n"
  		   "Locked:         %8lu kB\n",
  		   (vma->vm_end - vma->vm_start) >> 10,
  		   mss.resident >> 10,
  		   (unsigned long)(mss.pss >> (10 + PSS_SHIFT)),
  		   mss.shared_clean  >> 10,
  		   mss.shared_dirty  >> 10,
  		   mss.private_clean >> 10,
  		   mss.private_dirty >> 10,
  		   mss.referenced >> 10,
  		   mss.anonymous >> 10,
  		   mss.anonymous_thp >> 10,
  		   mss.shmem_thp >> 10,
  		   mss.shared_hugetlb >> 10,
  		   mss.private_hugetlb >> 10,
  		   mss.swap >> 10,
  		   (unsigned long)(mss.swap_pss >> (10 + PSS_SHIFT)),
  		   vma_kernel_pagesize(vma) >> 10,
  		   vma_mmu_pagesize(vma) >> 10,
  		   (vma->vm_flags & VM_LOCKED) ?
  			(unsigned long)(mss.pss >> (10 + PSS_SHIFT)) : 0);
  
  	arch_show_smap(m, vma);
  	show_smap_vma_flags(m, vma);
  	m_cache_vma(m, vma);
  	return 0;
  }
  
  static int show_pid_smap(struct seq_file *m, void *v)
  {
  	return show_smap(m, v, 1);
  }
  
  static int show_tid_smap(struct seq_file *m, void *v)
  {
  	return show_smap(m, v, 0);
  }
  
  static const struct seq_operations proc_pid_smaps_op = {
  	.start	= m_start,
  	.next	= m_next,
  	.stop	= m_stop,
  	.show	= show_pid_smap
  };
  
  static const struct seq_operations proc_tid_smaps_op = {
  	.start	= m_start,
  	.next	= m_next,
  	.stop	= m_stop,
  	.show	= show_tid_smap
  };
  
  static int pid_smaps_open(struct inode *inode, struct file *file)
  {
  	return do_maps_open(inode, file, &proc_pid_smaps_op);
  }
  
  static int tid_smaps_open(struct inode *inode, struct file *file)
  {
  	return do_maps_open(inode, file, &proc_tid_smaps_op);
  }
  
  const struct file_operations proc_pid_smaps_operations = {
  	.open		= pid_smaps_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= proc_map_release,
  };
  
  const struct file_operations proc_tid_smaps_operations = {
  	.open		= tid_smaps_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= proc_map_release,
  };
  
  enum clear_refs_types {
  	CLEAR_REFS_ALL = 1,
  	CLEAR_REFS_ANON,
  	CLEAR_REFS_MAPPED,
  	CLEAR_REFS_SOFT_DIRTY,
  	CLEAR_REFS_MM_HIWATER_RSS,
  	CLEAR_REFS_LAST,
  };
  
  struct clear_refs_private {
  	enum clear_refs_types type;
  };
  
  #ifdef CONFIG_MEM_SOFT_DIRTY
  static inline void clear_soft_dirty(struct vm_area_struct *vma,
  		unsigned long addr, pte_t *pte)
  {
  	/*
  	 * The soft-dirty tracker uses #PF-s to catch writes
  	 * to pages, so write-protect the pte as well. See the
  	 * Documentation/vm/soft-dirty.txt for full description
  	 * of how soft-dirty works.
  	 */
  	pte_t ptent = *pte;
  
  	if (pte_present(ptent)) {
  		ptent = ptep_modify_prot_start(vma->vm_mm, addr, pte);
  		ptent = pte_wrprotect(ptent);
  		ptent = pte_clear_soft_dirty(ptent);
  		ptep_modify_prot_commit(vma->vm_mm, addr, pte, ptent);
  	} else if (is_swap_pte(ptent)) {
  		ptent = pte_swp_clear_soft_dirty(ptent);
  		set_pte_at(vma->vm_mm, addr, pte, ptent);
  	}
  }
  #else
  static inline void clear_soft_dirty(struct vm_area_struct *vma,
  		unsigned long addr, pte_t *pte)
  {
  }
  #endif
  
  #if defined(CONFIG_MEM_SOFT_DIRTY) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
  static inline void clear_soft_dirty_pmd(struct vm_area_struct *vma,
  		unsigned long addr, pmd_t *pmdp)
  {
  	pmd_t pmd = pmdp_huge_get_and_clear(vma->vm_mm, addr, pmdp);
  
  	pmd = pmd_wrprotect(pmd);
  	pmd = pmd_clear_soft_dirty(pmd);
  
  	set_pmd_at(vma->vm_mm, addr, pmdp, pmd);
  }
  #else
  static inline void clear_soft_dirty_pmd(struct vm_area_struct *vma,
  		unsigned long addr, pmd_t *pmdp)
  {
  }
  #endif
  
  static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr,
  				unsigned long end, struct mm_walk *walk)
  {
  	struct clear_refs_private *cp = walk->private;
  	struct vm_area_struct *vma = walk->vma;
  	pte_t *pte, ptent;
  	spinlock_t *ptl;
  	struct page *page;
  
  	ptl = pmd_trans_huge_lock(pmd, vma);
  	if (ptl) {
  		if (cp->type == CLEAR_REFS_SOFT_DIRTY) {
  			clear_soft_dirty_pmd(vma, addr, pmd);
  			goto out;
  		}
  
  		page = pmd_page(*pmd);
  
  		/* Clear accessed and referenced bits. */
  		pmdp_test_and_clear_young(vma, addr, pmd);
  		test_and_clear_page_young(page);
  		ClearPageReferenced(page);
  out:
  		spin_unlock(ptl);
  		return 0;
  	}
  
  	if (pmd_trans_unstable(pmd))
  		return 0;
  
  	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
  	for (; addr != end; pte++, addr += PAGE_SIZE) {
  		ptent = *pte;
  
  		if (cp->type == CLEAR_REFS_SOFT_DIRTY) {
  			clear_soft_dirty(vma, addr, pte);
  			continue;
  		}
  
  		if (!pte_present(ptent))
  			continue;
  
  		page = vm_normal_page(vma, addr, ptent);
  		if (!page)
  			continue;
  
  		/* Clear accessed and referenced bits. */
  		ptep_test_and_clear_young(vma, addr, pte);
  		test_and_clear_page_young(page);
  		ClearPageReferenced(page);
  	}
  	pte_unmap_unlock(pte - 1, ptl);
  	cond_resched();
  	return 0;
  }
  
  static int clear_refs_test_walk(unsigned long start, unsigned long end,
  				struct mm_walk *walk)
  {
  	struct clear_refs_private *cp = walk->private;
  	struct vm_area_struct *vma = walk->vma;
  
  	if (vma->vm_flags & VM_PFNMAP)
  		return 1;
  
  	/*
  	 * Writing 1 to /proc/pid/clear_refs affects all pages.
  	 * Writing 2 to /proc/pid/clear_refs only affects anonymous pages.
  	 * Writing 3 to /proc/pid/clear_refs only affects file mapped pages.
  	 * Writing 4 to /proc/pid/clear_refs affects all pages.
  	 */
  	if (cp->type == CLEAR_REFS_ANON && vma->vm_file)
  		return 1;
  	if (cp->type == CLEAR_REFS_MAPPED && !vma->vm_file)
  		return 1;
  	return 0;
  }
  
  static ssize_t clear_refs_write(struct file *file, const char __user *buf,
  				size_t count, loff_t *ppos)
  {
  	struct task_struct *task;
  	char buffer[PROC_NUMBUF];
  	struct mm_struct *mm;
  	struct vm_area_struct *vma;
  	enum clear_refs_types type;
  	int itype;
  	int rv;
  
  	memset(buffer, 0, sizeof(buffer));
  	if (count > sizeof(buffer) - 1)
  		count = sizeof(buffer) - 1;
  	if (copy_from_user(buffer, buf, count))
  		return -EFAULT;
  	rv = kstrtoint(strstrip(buffer), 10, &itype);
  	if (rv < 0)
  		return rv;
  	type = (enum clear_refs_types)itype;
  	if (type < CLEAR_REFS_ALL || type >= CLEAR_REFS_LAST)
  		return -EINVAL;
  
  	task = get_proc_task(file_inode(file));
  	if (!task)
  		return -ESRCH;
  	mm = get_task_mm(task);
  	if (mm) {
  		struct clear_refs_private cp = {
  			.type = type,
  		};
  		struct mm_walk clear_refs_walk = {
  			.pmd_entry = clear_refs_pte_range,
  			.test_walk = clear_refs_test_walk,
  			.mm = mm,
  			.private = &cp,
  		};
  
  		if (type == CLEAR_REFS_MM_HIWATER_RSS) {
  			if (down_write_killable(&mm->mmap_sem)) {
  				count = -EINTR;
  				goto out_mm;
  			}
  
  			/*
  			 * Writing 5 to /proc/pid/clear_refs resets the peak
  			 * resident set size to this mm's current rss value.
  			 */
  			reset_mm_hiwater_rss(mm);
  			up_write(&mm->mmap_sem);
  			goto out_mm;
  		}
  
  		down_read(&mm->mmap_sem);
  		if (type == CLEAR_REFS_SOFT_DIRTY) {
  			for (vma = mm->mmap; vma; vma = vma->vm_next) {
  				if (!(vma->vm_flags & VM_SOFTDIRTY))
  					continue;
  				up_read(&mm->mmap_sem);
  				if (down_write_killable(&mm->mmap_sem)) {
  					count = -EINTR;
  					goto out_mm;
  				}
  				for (vma = mm->mmap; vma; vma = vma->vm_next) {
  					vma->vm_flags &= ~VM_SOFTDIRTY;
  					vma_set_page_prot(vma);
  				}
  				downgrade_write(&mm->mmap_sem);
  				break;
  			}
  			mmu_notifier_invalidate_range_start(mm, 0, -1);
  		}
  		walk_page_range(0, mm->highest_vm_end, &clear_refs_walk);
  		if (type == CLEAR_REFS_SOFT_DIRTY)
  			mmu_notifier_invalidate_range_end(mm, 0, -1);
  		flush_tlb_mm(mm);
  		up_read(&mm->mmap_sem);
  out_mm:
  		mmput(mm);
  	}
  	put_task_struct(task);
  
  	return count;
  }
  
  const struct file_operations proc_clear_refs_operations = {
  	.write		= clear_refs_write,
  	.llseek		= noop_llseek,
  };
  
  typedef struct {
  	u64 pme;
  } pagemap_entry_t;
  
  struct pagemapread {
  	int pos, len;		/* units: PM_ENTRY_BYTES, not bytes */
  	pagemap_entry_t *buffer;
  	bool show_pfn;
  };
  
  #define PAGEMAP_WALK_SIZE	(PMD_SIZE)
  #define PAGEMAP_WALK_MASK	(PMD_MASK)
  
  #define PM_ENTRY_BYTES		sizeof(pagemap_entry_t)
  #define PM_PFRAME_BITS		55
  #define PM_PFRAME_MASK		GENMASK_ULL(PM_PFRAME_BITS - 1, 0)
  #define PM_SOFT_DIRTY		BIT_ULL(55)
  #define PM_MMAP_EXCLUSIVE	BIT_ULL(56)
  #define PM_FILE			BIT_ULL(61)
  #define PM_SWAP			BIT_ULL(62)
  #define PM_PRESENT		BIT_ULL(63)
  
  #define PM_END_OF_BUFFER    1
  
  static inline pagemap_entry_t make_pme(u64 frame, u64 flags)
  {
  	return (pagemap_entry_t) { .pme = (frame & PM_PFRAME_MASK) | flags };
  }
  
  static int add_to_pagemap(unsigned long addr, pagemap_entry_t *pme,
  			  struct pagemapread *pm)
  {
  	pm->buffer[pm->pos++] = *pme;
  	if (pm->pos >= pm->len)
  		return PM_END_OF_BUFFER;
  	return 0;
  }
  
  static int pagemap_pte_hole(unsigned long start, unsigned long end,
  				struct mm_walk *walk)
  {
  	struct pagemapread *pm = walk->private;
  	unsigned long addr = start;
  	int err = 0;
  
  	while (addr < end) {
  		struct vm_area_struct *vma = find_vma(walk->mm, addr);
  		pagemap_entry_t pme = make_pme(0, 0);
  		/* End of address space hole, which we mark as non-present. */
  		unsigned long hole_end;
  
  		if (vma)
  			hole_end = min(end, vma->vm_start);
  		else
  			hole_end = end;
  
  		for (; addr < hole_end; addr += PAGE_SIZE) {
  			err = add_to_pagemap(addr, &pme, pm);
  			if (err)
  				goto out;
  		}
  
  		if (!vma)
  			break;
  
  		/* Addresses in the VMA. */
  		if (vma->vm_flags & VM_SOFTDIRTY)
  			pme = make_pme(0, PM_SOFT_DIRTY);
  		for (; addr < min(end, vma->vm_end); addr += PAGE_SIZE) {
  			err = add_to_pagemap(addr, &pme, pm);
  			if (err)
  				goto out;
  		}
  	}
  out:
  	return err;
  }
  
  static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm,
  		struct vm_area_struct *vma, unsigned long addr, pte_t pte)
  {
  	u64 frame = 0, flags = 0;
  	struct page *page = NULL;
  
  	if (pte_present(pte)) {
  		if (pm->show_pfn)
  			frame = pte_pfn(pte);
  		flags |= PM_PRESENT;
  		page = vm_normal_page(vma, addr, pte);
  		if (pte_soft_dirty(pte))
  			flags |= PM_SOFT_DIRTY;
  	} else if (is_swap_pte(pte)) {
  		swp_entry_t entry;
  		if (pte_swp_soft_dirty(pte))
  			flags |= PM_SOFT_DIRTY;
  		entry = pte_to_swp_entry(pte);
  		frame = swp_type(entry) |
  			(swp_offset(entry) << MAX_SWAPFILES_SHIFT);
  		flags |= PM_SWAP;
  		if (is_migration_entry(entry))
  			page = migration_entry_to_page(entry);
  	}
  
  	if (page && !PageAnon(page))
  		flags |= PM_FILE;
  	if (page && page_mapcount(page) == 1)
  		flags |= PM_MMAP_EXCLUSIVE;
  	if (vma->vm_flags & VM_SOFTDIRTY)
  		flags |= PM_SOFT_DIRTY;
  
  	return make_pme(frame, flags);
  }
  
  static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end,
  			     struct mm_walk *walk)
  {
  	struct vm_area_struct *vma = walk->vma;
  	struct pagemapread *pm = walk->private;
  	spinlock_t *ptl;
  	pte_t *pte, *orig_pte;
  	int err = 0;
  
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  	ptl = pmd_trans_huge_lock(pmdp, vma);
  	if (ptl) {
  		u64 flags = 0, frame = 0;
  		pmd_t pmd = *pmdp;
  
  		if ((vma->vm_flags & VM_SOFTDIRTY) || pmd_soft_dirty(pmd))
  			flags |= PM_SOFT_DIRTY;
  
  		/*
  		 * Currently pmd for thp is always present because thp
  		 * can not be swapped-out, migrated, or HWPOISONed
  		 * (split in such cases instead.)
  		 * This if-check is just to prepare for future implementation.
  		 */
  		if (pmd_present(pmd)) {
  			struct page *page = pmd_page(pmd);
  
  			if (page_mapcount(page) == 1)
  				flags |= PM_MMAP_EXCLUSIVE;
  
  			flags |= PM_PRESENT;
  			if (pm->show_pfn)
  				frame = pmd_pfn(pmd) +
  					((addr & ~PMD_MASK) >> PAGE_SHIFT);
  		}
  
  		for (; addr != end; addr += PAGE_SIZE) {
  			pagemap_entry_t pme = make_pme(frame, flags);
  
  			err = add_to_pagemap(addr, &pme, pm);
  			if (err)
  				break;
  			if (pm->show_pfn && (flags & PM_PRESENT))
  				frame++;
  		}
  		spin_unlock(ptl);
  		return err;
  	}
  
  	if (pmd_trans_unstable(pmdp))
  		return 0;
  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
  
  	/*
  	 * We can assume that @vma always points to a valid one and @end never
  	 * goes beyond vma->vm_end.
  	 */
  	orig_pte = pte = pte_offset_map_lock(walk->mm, pmdp, addr, &ptl);
  	for (; addr < end; pte++, addr += PAGE_SIZE) {
  		pagemap_entry_t pme;
  
  		pme = pte_to_pagemap_entry(pm, vma, addr, *pte);
  		err = add_to_pagemap(addr, &pme, pm);
  		if (err)
  			break;
  	}
  	pte_unmap_unlock(orig_pte, ptl);
  
  	cond_resched();
  
  	return err;
  }
  
  #ifdef CONFIG_HUGETLB_PAGE
  /* This function walks within one hugetlb entry in the single call */
  static int pagemap_hugetlb_range(pte_t *ptep, unsigned long hmask,
  				 unsigned long addr, unsigned long end,
  				 struct mm_walk *walk)
  {
  	struct pagemapread *pm = walk->private;
  	struct vm_area_struct *vma = walk->vma;
  	u64 flags = 0, frame = 0;
  	int err = 0;
  	pte_t pte;
  
  	if (vma->vm_flags & VM_SOFTDIRTY)
  		flags |= PM_SOFT_DIRTY;
  
  	pte = huge_ptep_get(ptep);
  	if (pte_present(pte)) {
  		struct page *page = pte_page(pte);
  
  		if (!PageAnon(page))
  			flags |= PM_FILE;
  
  		if (page_mapcount(page) == 1)
  			flags |= PM_MMAP_EXCLUSIVE;
  
  		flags |= PM_PRESENT;
  		if (pm->show_pfn)
  			frame = pte_pfn(pte) +
  				((addr & ~hmask) >> PAGE_SHIFT);
  	}
  
  	for (; addr != end; addr += PAGE_SIZE) {
  		pagemap_entry_t pme = make_pme(frame, flags);
  
  		err = add_to_pagemap(addr, &pme, pm);
  		if (err)
  			return err;
  		if (pm->show_pfn && (flags & PM_PRESENT))
  			frame++;
  	}
  
  	cond_resched();
  
  	return err;
  }
  #endif /* HUGETLB_PAGE */
  
  /*
   * /proc/pid/pagemap - an array mapping virtual pages to pfns
   *
   * For each page in the address space, this file contains one 64-bit entry
   * consisting of the following:
   *
   * Bits 0-54  page frame number (PFN) if present
   * Bits 0-4   swap type if swapped
   * Bits 5-54  swap offset if swapped
   * Bit  55    pte is soft-dirty (see Documentation/vm/soft-dirty.txt)
   * Bit  56    page exclusively mapped
   * Bits 57-60 zero
   * Bit  61    page is file-page or shared-anon
   * Bit  62    page swapped
   * Bit  63    page present
   *
   * If the page is not present but in swap, then the PFN contains an
   * encoding of the swap file number and the page's offset into the
   * swap. Unmapped pages return a null PFN. This allows determining
   * precisely which pages are mapped (or in swap) and comparing mapped
   * pages between processes.
   *
   * Efficient users of this interface will use /proc/pid/maps to
   * determine which areas of memory are actually mapped and llseek to
   * skip over unmapped regions.
   */
  static ssize_t pagemap_read(struct file *file, char __user *buf,
  			    size_t count, loff_t *ppos)
  {
  	struct mm_struct *mm = file->private_data;
  	struct pagemapread pm;
  	struct mm_walk pagemap_walk = {};
  	unsigned long src;
  	unsigned long svpfn;
  	unsigned long start_vaddr;
  	unsigned long end_vaddr;
  	int ret = 0, copied = 0;
  
  	if (!mm || !atomic_inc_not_zero(&mm->mm_users))
  		goto out;
  
  	ret = -EINVAL;
  	/* file position must be aligned */
  	if ((*ppos % PM_ENTRY_BYTES) || (count % PM_ENTRY_BYTES))
  		goto out_mm;
  
  	ret = 0;
  	if (!count)
  		goto out_mm;
  
  	/* do not disclose physical addresses: attack vector */
  	pm.show_pfn = file_ns_capable(file, &init_user_ns, CAP_SYS_ADMIN);
  
  	pm.len = (PAGEMAP_WALK_SIZE >> PAGE_SHIFT);
  	pm.buffer = kmalloc(pm.len * PM_ENTRY_BYTES, GFP_TEMPORARY);
  	ret = -ENOMEM;
  	if (!pm.buffer)
  		goto out_mm;
  
  	pagemap_walk.pmd_entry = pagemap_pmd_range;
  	pagemap_walk.pte_hole = pagemap_pte_hole;
  #ifdef CONFIG_HUGETLB_PAGE
  	pagemap_walk.hugetlb_entry = pagemap_hugetlb_range;
  #endif
  	pagemap_walk.mm = mm;
  	pagemap_walk.private = &pm;
  
  	src = *ppos;
  	svpfn = src / PM_ENTRY_BYTES;
  	start_vaddr = svpfn << PAGE_SHIFT;
  	end_vaddr = mm->task_size;
  
  	/* watch out for wraparound */
  	if (svpfn > mm->task_size >> PAGE_SHIFT)
  		start_vaddr = end_vaddr;
  
  	/*
  	 * The odds are that this will stop walking way
  	 * before end_vaddr, because the length of the
  	 * user buffer is tracked in "pm", and the walk
  	 * will stop when we hit the end of the buffer.
  	 */
  	ret = 0;
  	while (count && (start_vaddr < end_vaddr)) {
  		int len;
  		unsigned long end;
  
  		pm.pos = 0;
  		end = (start_vaddr + PAGEMAP_WALK_SIZE) & PAGEMAP_WALK_MASK;
  		/* overflow ? */
  		if (end < start_vaddr || end > end_vaddr)
  			end = end_vaddr;
  		down_read(&mm->mmap_sem);
  		ret = walk_page_range(start_vaddr, end, &pagemap_walk);
  		up_read(&mm->mmap_sem);
  		start_vaddr = end;
  
  		len = min(count, PM_ENTRY_BYTES * pm.pos);
  		if (copy_to_user(buf, pm.buffer, len)) {
  			ret = -EFAULT;
  			goto out_free;
  		}
  		copied += len;
  		buf += len;
  		count -= len;
  	}
  	*ppos += copied;
  	if (!ret || ret == PM_END_OF_BUFFER)
  		ret = copied;
  
  out_free:
  	kfree(pm.buffer);
  out_mm:
  	mmput(mm);
  out:
  	return ret;
  }
  
  static int pagemap_open(struct inode *inode, struct file *file)
  {
  	struct mm_struct *mm;
  
  	mm = proc_mem_open(inode, PTRACE_MODE_READ);
  	if (IS_ERR(mm))
  		return PTR_ERR(mm);
  	file->private_data = mm;
  	return 0;
  }
  
  static int pagemap_release(struct inode *inode, struct file *file)
  {
  	struct mm_struct *mm = file->private_data;
  
  	if (mm)
  		mmdrop(mm);
  	return 0;
  }
  
  const struct file_operations proc_pagemap_operations = {
  	.llseek		= mem_lseek, /* borrow this */
  	.read		= pagemap_read,
  	.open		= pagemap_open,
  	.release	= pagemap_release,
  };
  #endif /* CONFIG_PROC_PAGE_MONITOR */
  
  #ifdef CONFIG_NUMA
  
  struct numa_maps {
  	unsigned long pages;
  	unsigned long anon;
  	unsigned long active;
  	unsigned long writeback;
  	unsigned long mapcount_max;
  	unsigned long dirty;
  	unsigned long swapcache;
  	unsigned long node[MAX_NUMNODES];
  };
  
  struct numa_maps_private {
  	struct proc_maps_private proc_maps;
  	struct numa_maps md;
  };
  
  static void gather_stats(struct page *page, struct numa_maps *md, int pte_dirty,
  			unsigned long nr_pages)
  {
  	int count = page_mapcount(page);
  
  	md->pages += nr_pages;
  	if (pte_dirty || PageDirty(page))
  		md->dirty += nr_pages;
  
  	if (PageSwapCache(page))
  		md->swapcache += nr_pages;
  
  	if (PageActive(page) || PageUnevictable(page))
  		md->active += nr_pages;
  
  	if (PageWriteback(page))
  		md->writeback += nr_pages;
  
  	if (PageAnon(page))
  		md->anon += nr_pages;
  
  	if (count > md->mapcount_max)
  		md->mapcount_max = count;
  
  	md->node[page_to_nid(page)] += nr_pages;
  }
  
  static struct page *can_gather_numa_stats(pte_t pte, struct vm_area_struct *vma,
  		unsigned long addr)
  {
  	struct page *page;
  	int nid;
  
  	if (!pte_present(pte))
  		return NULL;
  
  	page = vm_normal_page(vma, addr, pte);
  	if (!page)
  		return NULL;
  
  	if (PageReserved(page))
  		return NULL;
  
  	nid = page_to_nid(page);
  	if (!node_isset(nid, node_states[N_MEMORY]))
  		return NULL;
  
  	return page;
  }
  
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  static struct page *can_gather_numa_stats_pmd(pmd_t pmd,
  					      struct vm_area_struct *vma,
  					      unsigned long addr)
  {
  	struct page *page;
  	int nid;
  
  	if (!pmd_present(pmd))
  		return NULL;
  
  	page = vm_normal_page_pmd(vma, addr, pmd);
  	if (!page)
  		return NULL;
  
  	if (PageReserved(page))
  		return NULL;
  
  	nid = page_to_nid(page);
  	if (!node_isset(nid, node_states[N_MEMORY]))
  		return NULL;
  
  	return page;
  }
  #endif
  
  static int gather_pte_stats(pmd_t *pmd, unsigned long addr,
  		unsigned long end, struct mm_walk *walk)
  {
  	struct numa_maps *md = walk->private;
  	struct vm_area_struct *vma = walk->vma;
  	spinlock_t *ptl;
  	pte_t *orig_pte;
  	pte_t *pte;
  
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  	ptl = pmd_trans_huge_lock(pmd, vma);
  	if (ptl) {
  		struct page *page;
  
  		page = can_gather_numa_stats_pmd(*pmd, vma, addr);
  		if (page)
  			gather_stats(page, md, pmd_dirty(*pmd),
  				     HPAGE_PMD_SIZE/PAGE_SIZE);
  		spin_unlock(ptl);
  		return 0;
  	}
  
  	if (pmd_trans_unstable(pmd))
  		return 0;
  #endif
  	orig_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
  	do {
  		struct page *page = can_gather_numa_stats(*pte, vma, addr);
  		if (!page)
  			continue;
  		gather_stats(page, md, pte_dirty(*pte), 1);
  
  	} while (pte++, addr += PAGE_SIZE, addr != end);
  	pte_unmap_unlock(orig_pte, ptl);
  	return 0;
  }
  #ifdef CONFIG_HUGETLB_PAGE
  static int gather_hugetlb_stats(pte_t *pte, unsigned long hmask,
  		unsigned long addr, unsigned long end, struct mm_walk *walk)
  {
  	pte_t huge_pte = huge_ptep_get(pte);
  	struct numa_maps *md;
  	struct page *page;
  
  	if (!pte_present(huge_pte))
  		return 0;
  
  	page = pte_page(huge_pte);
  	if (!page)
  		return 0;
  
  	md = walk->private;
  	gather_stats(page, md, pte_dirty(huge_pte), 1);
  	return 0;
  }
  
  #else
  static int gather_hugetlb_stats(pte_t *pte, unsigned long hmask,
  		unsigned long addr, unsigned long end, struct mm_walk *walk)
  {
  	return 0;
  }
  #endif
  
  /*
   * Display pages allocated per node and memory policy via /proc.
   */
  static int show_numa_map(struct seq_file *m, void *v, int is_pid)
  {
  	struct numa_maps_private *numa_priv = m->private;
  	struct proc_maps_private *proc_priv = &numa_priv->proc_maps;
  	struct vm_area_struct *vma = v;
  	struct numa_maps *md = &numa_priv->md;
  	struct file *file = vma->vm_file;
  	struct mm_struct *mm = vma->vm_mm;
  	struct mm_walk walk = {
  		.hugetlb_entry = gather_hugetlb_stats,
  		.pmd_entry = gather_pte_stats,
  		.private = md,
  		.mm = mm,
  	};
  	struct mempolicy *pol;
  	char buffer[64];
  	int nid;
  
  	if (!mm)
  		return 0;
  
  	/* Ensure we start with an empty set of numa_maps statistics. */
  	memset(md, 0, sizeof(*md));
  
  	pol = __get_vma_policy(vma, vma->vm_start);
  	if (pol) {
  		mpol_to_str(buffer, sizeof(buffer), pol);
  		mpol_cond_put(pol);
  	} else {
  		mpol_to_str(buffer, sizeof(buffer), proc_priv->task_mempolicy);
  	}
  
  	seq_printf(m, "%08lx %s", vma->vm_start, buffer);
  
  	if (file) {
  		seq_puts(m, " file=");
  		seq_file_path(m, file, "\n\t= ");
  	} else if (vma->vm_start <= mm->brk && vma->vm_end >= mm->start_brk) {
  		seq_puts(m, " heap");
  	} else if (is_stack(proc_priv, vma)) {
  		seq_puts(m, " stack");
  	}
  
  	if (is_vm_hugetlb_page(vma))
  		seq_puts(m, " huge");
  
  	/* mmap_sem is held by m_start */
  	walk_page_vma(vma, &walk);
  
  	if (!md->pages)
  		goto out;
  
  	if (md->anon)
  		seq_printf(m, " anon=%lu", md->anon);
  
  	if (md->dirty)
  		seq_printf(m, " dirty=%lu", md->dirty);
  
  	if (md->pages != md->anon && md->pages != md->dirty)
  		seq_printf(m, " mapped=%lu", md->pages);
  
  	if (md->mapcount_max > 1)
  		seq_printf(m, " mapmax=%lu", md->mapcount_max);
  
  	if (md->swapcache)
  		seq_printf(m, " swapcache=%lu", md->swapcache);
  
  	if (md->active < md->pages && !is_vm_hugetlb_page(vma))
  		seq_printf(m, " active=%lu", md->active);
  
  	if (md->writeback)
  		seq_printf(m, " writeback=%lu", md->writeback);
  
  	for_each_node_state(nid, N_MEMORY)
  		if (md->node[nid])
  			seq_printf(m, " N%d=%lu", nid, md->node[nid]);
  
  	seq_printf(m, " kernelpagesize_kB=%lu", vma_kernel_pagesize(vma) >> 10);
  out:
  	seq_putc(m, '\n');
  	m_cache_vma(m, vma);
  	return 0;
  }
  
  static int show_pid_numa_map(struct seq_file *m, void *v)
  {
  	return show_numa_map(m, v, 1);
  }
  
  static int show_tid_numa_map(struct seq_file *m, void *v)
  {
  	return show_numa_map(m, v, 0);
  }
  
  static const struct seq_operations proc_pid_numa_maps_op = {
  	.start  = m_start,
  	.next   = m_next,
  	.stop   = m_stop,
  	.show   = show_pid_numa_map,
  };
  
  static const struct seq_operations proc_tid_numa_maps_op = {
  	.start  = m_start,
  	.next   = m_next,
  	.stop   = m_stop,
  	.show   = show_tid_numa_map,
  };
  
  static int numa_maps_open(struct inode *inode, struct file *file,
  			  const struct seq_operations *ops)
  {
  	return proc_maps_open(inode, file, ops,
  				sizeof(struct numa_maps_private));
  }
  
  static int pid_numa_maps_open(struct inode *inode, struct file *file)
  {
  	return numa_maps_open(inode, file, &proc_pid_numa_maps_op);
  }
  
  static int tid_numa_maps_open(struct inode *inode, struct file *file)
  {
  	return numa_maps_open(inode, file, &proc_tid_numa_maps_op);
  }
  
  const struct file_operations proc_pid_numa_maps_operations = {
  	.open		= pid_numa_maps_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= proc_map_release,
  };
  
  const struct file_operations proc_tid_numa_maps_operations = {
  	.open		= tid_numa_maps_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= proc_map_release,
  };
  #endif /* CONFIG_NUMA */
  