fs/proc/task_mmu.c - kernel/msm-4.19 - Gitiles

 #include <linux/mm.h>
 #include <linux/hugetlb.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/swap.h>
 #include <linux/swapops.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 data, text, lib, swap;
 	unsigned long hiwater_vm, total_vm, hiwater_rss, total_rss;

 	/*
 	 * 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 = get_mm_rss(mm);
 	if (hiwater_rss < mm->hiwater_rss)
 		hiwater_rss = mm->hiwater_rss;

 	data = mm->total_vm - mm->shared_vm - mm->stack_vm;
 	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);
 	seq_printf(m,
 		"VmPeak:\t%8lu kB\n"
 		"VmSize:\t%8lu kB\n"
 		"VmLck:\t%8lu kB\n"
 		"VmHWM:\t%8lu kB\n"
 		"VmRSS:\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"
 		"VmSwap:\t%8lu kB\n",
 		hiwater_vm << (PAGE_SHIFT-10),
 		(total_vm - mm->reserved_vm) << (PAGE_SHIFT-10),
 		mm->locked_vm << (PAGE_SHIFT-10),
 		hiwater_rss << (PAGE_SHIFT-10),
 		total_rss << (PAGE_SHIFT-10),
 		data << (PAGE_SHIFT-10),
 		mm->stack_vm << (PAGE_SHIFT-10), text, lib,
 		(PTRS_PER_PTE*sizeof(pte_t)*mm->nr_ptes) >> 10,
 		swap << (PAGE_SHIFT-10));
 }

 unsigned long task_vsize(struct mm_struct *mm)
 {
 	return PAGE_SIZE * mm->total_vm;
 }

 int task_statm(struct mm_struct *mm, int *shared, int *text,
 	       int *data, int *resident)
 {
 	*shared = get_mm_counter(mm, MM_FILEPAGES);
 	*text = (PAGE_ALIGN(mm->end_code) - (mm->start_code & PAGE_MASK))
 								>> PAGE_SHIFT;
 	*data = mm->total_vm - mm->shared_vm;
 	*resident = *shared + get_mm_counter(mm, MM_ANONPAGES);
 	return mm->total_vm;
 }

 static void pad_len_spaces(struct seq_file *m, int len)
 {
 	len = 25 + sizeof(void*) * 6 - len;
 	if (len < 1)
 		len = 1;
 	seq_printf(m, "%*c", len, ' ');
 }

 static void vma_stop(struct proc_maps_private *priv, struct vm_area_struct *vma)
 {
 	if (vma && vma != priv->tail_vma) {
 		struct mm_struct *mm = vma->vm_mm;
 		up_read(&mm->mmap_sem);
 		mmput(mm);
 	}
 }

 static void *m_start(struct seq_file *m, loff_t *pos)
 {
 	struct proc_maps_private *priv = m->private;
 	unsigned long last_addr = m->version;
 	struct mm_struct *mm;
 	struct vm_area_struct *vma, *tail_vma = NULL;
 	loff_t l = *pos;

 	/* Clear the per syscall fields in priv */
 	priv->task = NULL;
 	priv->tail_vma = NULL;

 	/*
 	 * We remember last_addr rather than next_addr to hit with
 	 * mmap_cache most of the time. We have zero last_addr at
 	 * the beginning and also after lseek. We will have -1 last_addr
 	 * after the end of the vmas.
 	 */

 	if (last_addr == -1UL)
 		return NULL;

 	priv->task = get_pid_task(priv->pid, PIDTYPE_PID);
 	if (!priv->task)
 		return NULL;

 	mm = mm_for_maps(priv->task);
 	if (!mm)
 		return NULL;
 	down_read(&mm->mmap_sem);

 	tail_vma = get_gate_vma(priv->task);
 	priv->tail_vma = tail_vma;

 	/* Start with last addr hint */
 	vma = find_vma(mm, last_addr);
 	if (last_addr && vma) {
 		vma = vma->vm_next;
 		goto out;
 	}

 	/*
 	 * Check the vma index is within the range and do
 	 * sequential scan until m_index.
 	 */
 	vma = NULL;
 	if ((unsigned long)l < mm->map_count) {
 		vma = mm->mmap;
 		while (l-- && vma)
 			vma = vma->vm_next;
 		goto out;
 	}

 	if (l != mm->map_count)
 		tail_vma = NULL; /* After gate vma */

 out:
 	if (vma)
 		return vma;

 	/* End of vmas has been reached */
 	m->version = (tail_vma != NULL)? 0: -1UL;
 	up_read(&mm->mmap_sem);
 	mmput(mm);
 	return tail_vma;
 }

 static void *m_next(struct seq_file *m, void *v, loff_t *pos)
 {
 	struct proc_maps_private *priv = m->private;
 	struct vm_area_struct *vma = v;
 	struct vm_area_struct *tail_vma = priv->tail_vma;

 	(*pos)++;
 	if (vma && (vma != tail_vma) && vma->vm_next)
 		return vma->vm_next;
 	vma_stop(priv, vma);
 	return (vma != tail_vma)? tail_vma: NULL;
 }

 static void m_stop(struct seq_file *m, void *v)
 {
 	struct proc_maps_private *priv = m->private;
 	struct vm_area_struct *vma = v;

 	vma_stop(priv, vma);
 	if (priv->task)
 		put_task_struct(priv->task);
 }

 static int do_maps_open(struct inode *inode, struct file *file,
 			const struct seq_operations *ops)
 {
 	struct proc_maps_private *priv;
 	int ret = -ENOMEM;
 	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 	if (priv) {
 		priv->pid = proc_pid(inode);
 		ret = seq_open(file, ops);
 		if (!ret) {
 			struct seq_file *m = file->private_data;
 			m->private = priv;
 		} else {
 			kfree(priv);
 		}
 	}
 	return ret;
 }

 static void show_map_vma(struct seq_file *m, struct vm_area_struct *vma)
 {
 	struct mm_struct *mm = vma->vm_mm;
 	struct file *file = vma->vm_file;
 	int flags = vma->vm_flags;
 	unsigned long ino = 0;
 	unsigned long long pgoff = 0;
 	unsigned long start;
 	dev_t dev = 0;
 	int len;

 	if (file) {
 		struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
 		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 (vma->vm_flags & VM_GROWSDOWN)
 		if (!vma_stack_continue(vma->vm_prev, vma->vm_start))
 			start += PAGE_SIZE;

 	seq_printf(m, "%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu %n",
 			start,
 			vma->vm_end,
 			flags & VM_READ ? 'r' : '-',
 			flags & VM_WRITE ? 'w' : '-',
 			flags & VM_EXEC ? 'x' : '-',
 			flags & VM_MAYSHARE ? 's' : 'p',
 			pgoff,
 			MAJOR(dev), MINOR(dev), ino, &len);

 	/*
 	 * Print the dentry name for named mappings, and a
 	 * special [heap] marker for the heap:
 	 */
 	if (file) {
 		pad_len_spaces(m, len);
 		seq_path(m, &file->f_path, "\n");
 	} else {
 		const char *name = arch_vma_name(vma);
 		if (!name) {
 			if (mm) {
 				if (vma->vm_start <= mm->start_brk &&
 						vma->vm_end >= mm->brk) {
 					name = "[heap]";
 				} else if (vma->vm_start <= mm->start_stack &&
 					   vma->vm_end >= mm->start_stack) {
 					name = "[stack]";
 				}
 			} else {
 				name = "[vdso]";
 			}
 		}
 		if (name) {
 			pad_len_spaces(m, len);
 			seq_puts(m, name);
 		}
 	}
 	seq_putc(m, '\n');
 }

 static int show_map(struct seq_file *m, void *v)
 {
 	struct vm_area_struct *vma = v;
 	struct proc_maps_private *priv = m->private;
 	struct task_struct *task = priv->task;

 	show_map_vma(m, vma);

 	if (m->count < m->size)  /* vma is copied successfully */
 		m->version = (vma != get_gate_vma(task))? vma->vm_start: 0;
 	return 0;
 }

 static const struct seq_operations proc_pid_maps_op = {
 	.start	= m_start,
 	.next	= m_next,
 	.stop	= m_stop,
 	.show	= show_map
 };

 static int maps_open(struct inode *inode, struct file *file)
 {
 	return do_maps_open(inode, file, &proc_pid_maps_op);
 }

 const struct file_operations proc_maps_operations = {
 	.open		= maps_open,
 	.read		= seq_read,
 	.llseek		= seq_lseek,
 	.release	= seq_release_private,
 };

 /*
  * 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 {
 	struct vm_area_struct *vma;
 	unsigned long resident;
 	unsigned long shared_clean;
 	unsigned long shared_dirty;
 	unsigned long private_clean;
 	unsigned long private_dirty;
 	unsigned long referenced;
 	unsigned long swap;
 	u64 pss;
 };

 static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 			   struct mm_walk *walk)
 {
 	struct mem_size_stats *mss = walk->private;
 	struct vm_area_struct *vma = mss->vma;
 	pte_t *pte, ptent;
 	spinlock_t *ptl;
 	struct page *page;
 	int mapcount;

 	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
 	for (; addr != end; pte++, addr += PAGE_SIZE) {
 		ptent = *pte;

 		if (is_swap_pte(ptent)) {
 			mss->swap += PAGE_SIZE;
 			continue;
 		}

 		if (!pte_present(ptent))
 			continue;

 		page = vm_normal_page(vma, addr, ptent);
 		if (!page)
 			continue;

 		mss->resident += PAGE_SIZE;
 		/* Accumulate the size in pages that have been accessed. */
 		if (pte_young(ptent) || PageReferenced(page))
 			mss->referenced += PAGE_SIZE;
 		mapcount = page_mapcount(page);
 		if (mapcount >= 2) {
 			if (pte_dirty(ptent) || PageDirty(page))
 				mss->shared_dirty += PAGE_SIZE;
 			else
 				mss->shared_clean += PAGE_SIZE;
 			mss->pss += (PAGE_SIZE << PSS_SHIFT) / mapcount;
 		} else {
 			if (pte_dirty(ptent) || PageDirty(page))
 				mss->private_dirty += PAGE_SIZE;
 			else
 				mss->private_clean += PAGE_SIZE;
 			mss->pss += (PAGE_SIZE << PSS_SHIFT);
 		}
 	}
 	pte_unmap_unlock(pte - 1, ptl);
 	cond_resched();
 	return 0;
 }

 static int show_smap(struct seq_file *m, void *v)
 {
 	struct proc_maps_private *priv = m->private;
 	struct task_struct *task = priv->task;
 	struct vm_area_struct *vma = v;
 	struct mem_size_stats mss;
 	struct mm_walk smaps_walk = {
 		.pmd_entry = smaps_pte_range,
 		.mm = vma->vm_mm,
 		.private = &mss,
 	};

 	memset(&mss, 0, sizeof mss);
 	mss.vma = vma;
 	/* mmap_sem is held in m_start */
 	if (vma->vm_mm && !is_vm_hugetlb_page(vma))
 		walk_page_range(vma->vm_start, vma->vm_end, &smaps_walk);

 	show_map_vma(m, vma);

 	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"
 		   "Swap:           %8lu kB\n"
 		   "KernelPageSize: %8lu kB\n"
 		   "MMUPageSize:    %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.swap >> 10,
 		   vma_kernel_pagesize(vma) >> 10,
 		   vma_mmu_pagesize(vma) >> 10);

 	if (m->count < m->size)  /* vma is copied successfully */
 		m->version = (vma != get_gate_vma(task)) ? vma->vm_start : 0;
 	return 0;
 }

 static const struct seq_operations proc_pid_smaps_op = {
 	.start	= m_start,
 	.next	= m_next,
 	.stop	= m_stop,
 	.show	= show_smap
 };

 static int smaps_open(struct inode *inode, struct file *file)
 {
 	return do_maps_open(inode, file, &proc_pid_smaps_op);
 }

 const struct file_operations proc_smaps_operations = {
 	.open		= smaps_open,
 	.read		= seq_read,
 	.llseek		= seq_lseek,
 	.release	= seq_release_private,
 };

 static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr,
 				unsigned long end, struct mm_walk *walk)
 {
 	struct vm_area_struct *vma = walk->private;
 	pte_t *pte, ptent;
 	spinlock_t *ptl;
 	struct page *page;

 	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
 	for (; addr != end; pte++, addr += PAGE_SIZE) {
 		ptent = *pte;
 		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);
 		ClearPageReferenced(page);
 	}
 	pte_unmap_unlock(pte - 1, ptl);
 	cond_resched();
 	return 0;
 }

 #define CLEAR_REFS_ALL 1
 #define CLEAR_REFS_ANON 2
 #define CLEAR_REFS_MAPPED 3

 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;
 	long type;

 	memset(buffer, 0, sizeof(buffer));
 	if (count > sizeof(buffer) - 1)
 		count = sizeof(buffer) - 1;
 	if (copy_from_user(buffer, buf, count))
 		return -EFAULT;
 	if (strict_strtol(strstrip(buffer), 10, &type))
 		return -EINVAL;
 	if (type < CLEAR_REFS_ALL || type > CLEAR_REFS_MAPPED)
 		return -EINVAL;
 	task = get_proc_task(file->f_path.dentry->d_inode);
 	if (!task)
 		return -ESRCH;
 	mm = get_task_mm(task);
 	if (mm) {
 		struct mm_walk clear_refs_walk = {
 			.pmd_entry = clear_refs_pte_range,
 			.mm = mm,
 		};
 		down_read(&mm->mmap_sem);
 		for (vma = mm->mmap; vma; vma = vma->vm_next) {
 			clear_refs_walk.private = vma;
 			if (is_vm_hugetlb_page(vma))
 				continue;
 			/*
 			 * 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.
 			 */
 			if (type == CLEAR_REFS_ANON && vma->vm_file)
 				continue;
 			if (type == CLEAR_REFS_MAPPED && !vma->vm_file)
 				continue;
 			walk_page_range(vma->vm_start, vma->vm_end,
 					&clear_refs_walk);
 		}
 		flush_tlb_mm(mm);
 		up_read(&mm->mmap_sem);
 		mmput(mm);
 	}
 	put_task_struct(task);

 	return count;
 }

 const struct file_operations proc_clear_refs_operations = {
 	.write		= clear_refs_write,
 	.llseek		= noop_llseek,
 };

 struct pagemapread {
 	int pos, len;
 	u64 *buffer;
 };

 #define PM_ENTRY_BYTES      sizeof(u64)
 #define PM_STATUS_BITS      3
 #define PM_STATUS_OFFSET    (64 - PM_STATUS_BITS)
 #define PM_STATUS_MASK      (((1LL << PM_STATUS_BITS) - 1) << PM_STATUS_OFFSET)
 #define PM_STATUS(nr)       (((nr) << PM_STATUS_OFFSET) & PM_STATUS_MASK)
 #define PM_PSHIFT_BITS      6
 #define PM_PSHIFT_OFFSET    (PM_STATUS_OFFSET - PM_PSHIFT_BITS)
 #define PM_PSHIFT_MASK      (((1LL << PM_PSHIFT_BITS) - 1) << PM_PSHIFT_OFFSET)
 #define PM_PSHIFT(x)        (((u64) (x) << PM_PSHIFT_OFFSET) & PM_PSHIFT_MASK)
 #define PM_PFRAME_MASK      ((1LL << PM_PSHIFT_OFFSET) - 1)
 #define PM_PFRAME(x)        ((x) & PM_PFRAME_MASK)

 #define PM_PRESENT          PM_STATUS(4LL)
 #define PM_SWAP             PM_STATUS(2LL)
 #define PM_NOT_PRESENT      PM_PSHIFT(PAGE_SHIFT)
 #define PM_END_OF_BUFFER    1

 static int add_to_pagemap(unsigned long addr, u64 pfn,
 			  struct pagemapread *pm)
 {
 	pm->buffer[pm->pos++] = pfn;
 	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;
 	int err = 0;
 	for (addr = start; addr < end; addr += PAGE_SIZE) {
 		err = add_to_pagemap(addr, PM_NOT_PRESENT, pm);
 		if (err)
 			break;
 	}
 	return err;
 }

 static u64 swap_pte_to_pagemap_entry(pte_t pte)
 {
 	swp_entry_t e = pte_to_swp_entry(pte);
 	return swp_type(e) | (swp_offset(e) << MAX_SWAPFILES_SHIFT);
 }

 static u64 pte_to_pagemap_entry(pte_t pte)
 {
 	u64 pme = 0;
 	if (is_swap_pte(pte))
 		pme = PM_PFRAME(swap_pte_to_pagemap_entry(pte))
 			| PM_PSHIFT(PAGE_SHIFT) | PM_SWAP;
 	else if (pte_present(pte))
 		pme = PM_PFRAME(pte_pfn(pte))
 			| PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT;
 	return pme;
 }

 static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 			     struct mm_walk *walk)
 {
 	struct vm_area_struct *vma;
 	struct pagemapread *pm = walk->private;
 	pte_t *pte;
 	int err = 0;

 	/* find the first VMA at or above 'addr' */
 	vma = find_vma(walk->mm, addr);
 	for (; addr != end; addr += PAGE_SIZE) {
 		u64 pfn = PM_NOT_PRESENT;

 		/* check to see if we've left 'vma' behind
 		 * and need a new, higher one */
 		if (vma && (addr >= vma->vm_end))
 			vma = find_vma(walk->mm, addr);

 		/* check that 'vma' actually covers this address,
 		 * and that it isn't a huge page vma */
 		if (vma && (vma->vm_start <= addr) &&
 		    !is_vm_hugetlb_page(vma)) {
 			pte = pte_offset_map(pmd, addr);
 			pfn = pte_to_pagemap_entry(*pte);
 			/* unmap before userspace copy */
 			pte_unmap(pte);
 		}
 		err = add_to_pagemap(addr, pfn, pm);
 		if (err)
 			return err;
 	}

 	cond_resched();

 	return err;
 }

 #ifdef CONFIG_HUGETLB_PAGE
 static u64 huge_pte_to_pagemap_entry(pte_t pte, int offset)
 {
 	u64 pme = 0;
 	if (pte_present(pte))
 		pme = PM_PFRAME(pte_pfn(pte) + offset)
 			| PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT;
 	return pme;
 }

 /* This function walks within one hugetlb entry in the single call */
 static int pagemap_hugetlb_range(pte_t *pte, unsigned long hmask,
 				 unsigned long addr, unsigned long end,
 				 struct mm_walk *walk)
 {
 	struct pagemapread *pm = walk->private;
 	int err = 0;
 	u64 pfn;

 	for (; addr != end; addr += PAGE_SIZE) {
 		int offset = (addr & ~hmask) >> PAGE_SHIFT;
 		pfn = huge_pte_to_pagemap_entry(*pte, offset);
 		err = add_to_pagemap(addr, pfn, pm);
 		if (err)
 			return err;
 	}

 	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 0-55  page frame number (PFN) if present
  * Bits 0-4   swap type if swapped
  * Bits 5-55  swap offset if swapped
  * Bits 55-60 page shift (page size = 1<<page shift)
  * Bit  61    reserved for future use
  * 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.
  */
 #define PAGEMAP_WALK_SIZE	(PMD_SIZE)
 static ssize_t pagemap_read(struct file *file, char __user *buf,
 			    size_t count, loff_t *ppos)
 {
 	struct task_struct *task = get_proc_task(file->f_path.dentry->d_inode);
 	struct mm_struct *mm;
 	struct pagemapread pm;
 	int ret = -ESRCH;
 	struct mm_walk pagemap_walk = {};
 	unsigned long src;
 	unsigned long svpfn;
 	unsigned long start_vaddr;
 	unsigned long end_vaddr;
 	int copied = 0;

 	if (!task)
 		goto out;

 	ret = -EACCES;
 	if (!ptrace_may_access(task, PTRACE_MODE_READ))
 		goto out_task;

 	ret = -EINVAL;
 	/* file position must be aligned */
 	if ((*ppos % PM_ENTRY_BYTES) || (count % PM_ENTRY_BYTES))
 		goto out_task;

 	ret = 0;

 	if (!count)
 		goto out_task;

 	mm = get_task_mm(task);
 	if (!mm)
 		goto out_task;

 	pm.len = PM_ENTRY_BYTES * (PAGEMAP_WALK_SIZE >> PAGE_SHIFT);
 	pm.buffer = kmalloc(pm.len, GFP_TEMPORARY);
 	ret = -ENOMEM;
 	if (!pm.buffer)
 		goto out_mm;

 	pagemap_walk.pmd_entry = pagemap_pte_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 = TASK_SIZE_OF(task);

 	/* watch out for wraparound */
 	if (svpfn > TASK_SIZE_OF(task) >> 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;
 		/* 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_task:
 	put_task_struct(task);
 out:
 	return ret;
 }

 const struct file_operations proc_pagemap_operations = {
 	.llseek		= mem_lseek, /* borrow this */
 	.read		= pagemap_read,
 };
 #endif /* CONFIG_PROC_PAGE_MONITOR */

 #ifdef CONFIG_NUMA
 extern int show_numa_map(struct seq_file *m, void *v);

 static const struct seq_operations proc_pid_numa_maps_op = {
         .start  = m_start,
         .next   = m_next,
         .stop   = m_stop,
         .show   = show_numa_map,
 };

 static int numa_maps_open(struct inode *inode, struct file *file)
 {
 	return do_maps_open(inode, file, &proc_pid_numa_maps_op);
 }

 const struct file_operations proc_numa_maps_operations = {
 	.open		= numa_maps_open,
 	.read		= seq_read,
 	.llseek		= seq_lseek,
 	.release	= seq_release_private,
 };
 #endif
	#include <linux/mm.h>
	#include <linux/hugetlb.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/swap.h>
	#include <linux/swapops.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 data, text, lib, swap;
	unsigned long hiwater_vm, total_vm, hiwater_rss, total_rss;

	/*
	* 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 = get_mm_rss(mm);
	if (hiwater_rss < mm->hiwater_rss)
	hiwater_rss = mm->hiwater_rss;

	data = mm->total_vm - mm->shared_vm - mm->stack_vm;
	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);
	seq_printf(m,
	"VmPeak:\t%8lu kB\n"
	"VmSize:\t%8lu kB\n"
	"VmLck:\t%8lu kB\n"
	"VmHWM:\t%8lu kB\n"
	"VmRSS:\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"
	"VmSwap:\t%8lu kB\n",
	hiwater_vm << (PAGE_SHIFT-10),
	(total_vm - mm->reserved_vm) << (PAGE_SHIFT-10),
	mm->locked_vm << (PAGE_SHIFT-10),
	hiwater_rss << (PAGE_SHIFT-10),
	total_rss << (PAGE_SHIFT-10),
	data << (PAGE_SHIFT-10),
	mm->stack_vm << (PAGE_SHIFT-10), text, lib,
	(PTRS_PER_PTEsizeof(pte_t)mm->nr_ptes) >> 10,
	swap << (PAGE_SHIFT-10));
	}

	unsigned long task_vsize(struct mm_struct *mm)
	{
	return PAGE_SIZE * mm->total_vm;
	}

	int task_statm(struct mm_struct mm, int shared, int *text,
	int data, int resident)
	{
	*shared = get_mm_counter(mm, MM_FILEPAGES);
	*text = (PAGE_ALIGN(mm->end_code) - (mm->start_code & PAGE_MASK))
	>> PAGE_SHIFT;
	*data = mm->total_vm - mm->shared_vm;
	resident = shared + get_mm_counter(mm, MM_ANONPAGES);
	return mm->total_vm;
	}

	static void pad_len_spaces(struct seq_file *m, int len)
	{
	len = 25 + sizeof(void) 6 - len;
	if (len < 1)
	len = 1;
	seq_printf(m, "%*c", len, ' ');
	}

	static void vma_stop(struct proc_maps_private priv, struct vm_area_struct vma)
	{
	if (vma && vma != priv->tail_vma) {
	struct mm_struct *mm = vma->vm_mm;
	up_read(&mm->mmap_sem);
	mmput(mm);
	}
	}

	static void m_start(struct seq_file m, loff_t *pos)
	{
	struct proc_maps_private *priv = m->private;
	unsigned long last_addr = m->version;
	struct mm_struct *mm;
	struct vm_area_struct vma, tail_vma = NULL;
	loff_t l = *pos;

	/* Clear the per syscall fields in priv */
	priv->task = NULL;
	priv->tail_vma = NULL;

	/*
	* We remember last_addr rather than next_addr to hit with
	* mmap_cache most of the time. We have zero last_addr at
	* the beginning and also after lseek. We will have -1 last_addr
	* after the end of the vmas.
	*/

	if (last_addr == -1UL)
	return NULL;

	priv->task = get_pid_task(priv->pid, PIDTYPE_PID);
	if (!priv->task)
	return NULL;

	mm = mm_for_maps(priv->task);
	if (!mm)
	return NULL;
	down_read(&mm->mmap_sem);

	tail_vma = get_gate_vma(priv->task);
	priv->tail_vma = tail_vma;

	/* Start with last addr hint */
	vma = find_vma(mm, last_addr);
	if (last_addr && vma) {
	vma = vma->vm_next;
	goto out;
	}

	/*
	* Check the vma index is within the range and do
	* sequential scan until m_index.
	*/
	vma = NULL;
	if ((unsigned long)l < mm->map_count) {
	vma = mm->mmap;
	while (l-- && vma)
	vma = vma->vm_next;
	goto out;
	}

	if (l != mm->map_count)
	tail_vma = NULL; /* After gate vma */

	out:
	if (vma)
	return vma;

	/* End of vmas has been reached */
	m->version = (tail_vma != NULL)? 0: -1UL;
	up_read(&mm->mmap_sem);
	mmput(mm);
	return tail_vma;
	}

	static void m_next(struct seq_file m, void v, loff_t pos)
	{
	struct proc_maps_private *priv = m->private;
	struct vm_area_struct *vma = v;
	struct vm_area_struct *tail_vma = priv->tail_vma;

	(*pos)++;
	if (vma && (vma != tail_vma) && vma->vm_next)
	return vma->vm_next;
	vma_stop(priv, vma);
	return (vma != tail_vma)? tail_vma: NULL;
	}

	static void m_stop(struct seq_file m, void v)
	{
	struct proc_maps_private *priv = m->private;
	struct vm_area_struct *vma = v;

	vma_stop(priv, vma);
	if (priv->task)
	put_task_struct(priv->task);
	}

	static int do_maps_open(struct inode inode, struct file file,
	const struct seq_operations *ops)
	{
	struct proc_maps_private *priv;
	int ret = -ENOMEM;
	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
	if (priv) {
	priv->pid = proc_pid(inode);
	ret = seq_open(file, ops);
	if (!ret) {
	struct seq_file *m = file->private_data;
	m->private = priv;
	} else {
	kfree(priv);
	}
	}
	return ret;
	}

	static void show_map_vma(struct seq_file m, struct vm_area_struct vma)
	{
	struct mm_struct *mm = vma->vm_mm;
	struct file *file = vma->vm_file;
	int flags = vma->vm_flags;
	unsigned long ino = 0;
	unsigned long long pgoff = 0;
	unsigned long start;
	dev_t dev = 0;
	int len;

	if (file) {
	struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
	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 (vma->vm_flags & VM_GROWSDOWN)
	if (!vma_stack_continue(vma->vm_prev, vma->vm_start))
	start += PAGE_SIZE;

	seq_printf(m, "%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu %n",
	start,
	vma->vm_end,
	flags & VM_READ ? 'r' : '-',
	flags & VM_WRITE ? 'w' : '-',
	flags & VM_EXEC ? 'x' : '-',
	flags & VM_MAYSHARE ? 's' : 'p',
	pgoff,
	MAJOR(dev), MINOR(dev), ino, &len);

	/*
	* Print the dentry name for named mappings, and a
	* special [heap] marker for the heap:
	*/
	if (file) {
	pad_len_spaces(m, len);
	seq_path(m, &file->f_path, "\n");
	} else {
	const char *name = arch_vma_name(vma);
	if (!name) {
	if (mm) {
	if (vma->vm_start <= mm->start_brk &&
	vma->vm_end >= mm->brk) {
	name = "[heap]";
	} else if (vma->vm_start <= mm->start_stack &&
	vma->vm_end >= mm->start_stack) {
	name = "[stack]";
	}
	} else {
	name = "[vdso]";
	}
	}
	if (name) {
	pad_len_spaces(m, len);
	seq_puts(m, name);
	}
	}
	seq_putc(m, '\n');
	}

	static int show_map(struct seq_file m, void v)
	{
	struct vm_area_struct *vma = v;
	struct proc_maps_private *priv = m->private;
	struct task_struct *task = priv->task;

	show_map_vma(m, vma);

	if (m->count < m->size) /* vma is copied successfully */
	m->version = (vma != get_gate_vma(task))? vma->vm_start: 0;
	return 0;
	}

	static const struct seq_operations proc_pid_maps_op = {
	.start = m_start,
	.next = m_next,
	.stop = m_stop,
	.show = show_map
	};

	static int maps_open(struct inode inode, struct file file)
	{
	return do_maps_open(inode, file, &proc_pid_maps_op);
	}

	const struct file_operations proc_maps_operations = {
	.open = maps_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = seq_release_private,
	};

	/*
	* 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 {
	struct vm_area_struct *vma;
	unsigned long resident;
	unsigned long shared_clean;
	unsigned long shared_dirty;
	unsigned long private_clean;
	unsigned long private_dirty;
	unsigned long referenced;
	unsigned long swap;
	u64 pss;
	};

	static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
	struct mm_walk *walk)
	{
	struct mem_size_stats *mss = walk->private;
	struct vm_area_struct *vma = mss->vma;
	pte_t *pte, ptent;
	spinlock_t *ptl;
	struct page *page;
	int mapcount;

	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
	for (; addr != end; pte++, addr += PAGE_SIZE) {
	ptent = *pte;

	if (is_swap_pte(ptent)) {
	mss->swap += PAGE_SIZE;
	continue;
	}

	if (!pte_present(ptent))
	continue;

	page = vm_normal_page(vma, addr, ptent);
	if (!page)
	continue;

	mss->resident += PAGE_SIZE;
	/* Accumulate the size in pages that have been accessed. */
	if (pte_young(ptent) \|\| PageReferenced(page))
	mss->referenced += PAGE_SIZE;
	mapcount = page_mapcount(page);
	if (mapcount >= 2) {
	if (pte_dirty(ptent) \|\| PageDirty(page))
	mss->shared_dirty += PAGE_SIZE;
	else
	mss->shared_clean += PAGE_SIZE;
	mss->pss += (PAGE_SIZE << PSS_SHIFT) / mapcount;
	} else {
	if (pte_dirty(ptent) \|\| PageDirty(page))
	mss->private_dirty += PAGE_SIZE;
	else
	mss->private_clean += PAGE_SIZE;
	mss->pss += (PAGE_SIZE << PSS_SHIFT);
	}
	}
	pte_unmap_unlock(pte - 1, ptl);
	cond_resched();
	return 0;
	}

	static int show_smap(struct seq_file m, void v)
	{
	struct proc_maps_private *priv = m->private;
	struct task_struct *task = priv->task;
	struct vm_area_struct *vma = v;
	struct mem_size_stats mss;
	struct mm_walk smaps_walk = {
	.pmd_entry = smaps_pte_range,
	.mm = vma->vm_mm,
	.private = &mss,
	};

	memset(&mss, 0, sizeof mss);
	mss.vma = vma;
	/* mmap_sem is held in m_start */
	if (vma->vm_mm && !is_vm_hugetlb_page(vma))
	walk_page_range(vma->vm_start, vma->vm_end, &smaps_walk);

	show_map_vma(m, vma);

	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"
	"Swap: %8lu kB\n"
	"KernelPageSize: %8lu kB\n"
	"MMUPageSize: %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.swap >> 10,
	vma_kernel_pagesize(vma) >> 10,
	vma_mmu_pagesize(vma) >> 10);

	if (m->count < m->size) /* vma is copied successfully */
	m->version = (vma != get_gate_vma(task)) ? vma->vm_start : 0;
	return 0;
	}

	static const struct seq_operations proc_pid_smaps_op = {
	.start = m_start,
	.next = m_next,
	.stop = m_stop,
	.show = show_smap
	};

	static int smaps_open(struct inode inode, struct file file)
	{
	return do_maps_open(inode, file, &proc_pid_smaps_op);
	}

	const struct file_operations proc_smaps_operations = {
	.open = smaps_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = seq_release_private,
	};

	static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr,
	unsigned long end, struct mm_walk *walk)
	{
	struct vm_area_struct *vma = walk->private;
	pte_t *pte, ptent;
	spinlock_t *ptl;
	struct page *page;

	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
	for (; addr != end; pte++, addr += PAGE_SIZE) {
	ptent = *pte;
	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);
	ClearPageReferenced(page);
	}
	pte_unmap_unlock(pte - 1, ptl);
	cond_resched();
	return 0;
	}

	#define CLEAR_REFS_ALL 1
	#define CLEAR_REFS_ANON 2
	#define CLEAR_REFS_MAPPED 3

	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;
	long type;

	memset(buffer, 0, sizeof(buffer));
	if (count > sizeof(buffer) - 1)
	count = sizeof(buffer) - 1;
	if (copy_from_user(buffer, buf, count))
	return -EFAULT;
	if (strict_strtol(strstrip(buffer), 10, &type))
	return -EINVAL;
	if (type < CLEAR_REFS_ALL \|\| type > CLEAR_REFS_MAPPED)
	return -EINVAL;
	task = get_proc_task(file->f_path.dentry->d_inode);
	if (!task)
	return -ESRCH;
	mm = get_task_mm(task);
	if (mm) {
	struct mm_walk clear_refs_walk = {
	.pmd_entry = clear_refs_pte_range,
	.mm = mm,
	};
	down_read(&mm->mmap_sem);
	for (vma = mm->mmap; vma; vma = vma->vm_next) {
	clear_refs_walk.private = vma;
	if (is_vm_hugetlb_page(vma))
	continue;
	/*
	* 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.
	*/
	if (type == CLEAR_REFS_ANON && vma->vm_file)
	continue;
	if (type == CLEAR_REFS_MAPPED && !vma->vm_file)
	continue;
	walk_page_range(vma->vm_start, vma->vm_end,
	&clear_refs_walk);
	}
	flush_tlb_mm(mm);
	up_read(&mm->mmap_sem);
	mmput(mm);
	}
	put_task_struct(task);

	return count;
	}

	const struct file_operations proc_clear_refs_operations = {
	.write = clear_refs_write,
	.llseek = noop_llseek,
	};

	struct pagemapread {
	int pos, len;
	u64 *buffer;
	};

	#define PM_ENTRY_BYTES sizeof(u64)
	#define PM_STATUS_BITS 3
	#define PM_STATUS_OFFSET (64 - PM_STATUS_BITS)
	#define PM_STATUS_MASK (((1LL << PM_STATUS_BITS) - 1) << PM_STATUS_OFFSET)
	#define PM_STATUS(nr) (((nr) << PM_STATUS_OFFSET) & PM_STATUS_MASK)
	#define PM_PSHIFT_BITS 6
	#define PM_PSHIFT_OFFSET (PM_STATUS_OFFSET - PM_PSHIFT_BITS)
	#define PM_PSHIFT_MASK (((1LL << PM_PSHIFT_BITS) - 1) << PM_PSHIFT_OFFSET)
	#define PM_PSHIFT(x) (((u64) (x) << PM_PSHIFT_OFFSET) & PM_PSHIFT_MASK)
	#define PM_PFRAME_MASK ((1LL << PM_PSHIFT_OFFSET) - 1)
	#define PM_PFRAME(x) ((x) & PM_PFRAME_MASK)

	#define PM_PRESENT PM_STATUS(4LL)
	#define PM_SWAP PM_STATUS(2LL)
	#define PM_NOT_PRESENT PM_PSHIFT(PAGE_SHIFT)
	#define PM_END_OF_BUFFER 1

	static int add_to_pagemap(unsigned long addr, u64 pfn,
	struct pagemapread *pm)
	{
	pm->buffer[pm->pos++] = pfn;
	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;
	int err = 0;
	for (addr = start; addr < end; addr += PAGE_SIZE) {
	err = add_to_pagemap(addr, PM_NOT_PRESENT, pm);
	if (err)
	break;
	}
	return err;
	}

	static u64 swap_pte_to_pagemap_entry(pte_t pte)
	{
	swp_entry_t e = pte_to_swp_entry(pte);
	return swp_type(e) \| (swp_offset(e) << MAX_SWAPFILES_SHIFT);
	}

	static u64 pte_to_pagemap_entry(pte_t pte)
	{
	u64 pme = 0;
	if (is_swap_pte(pte))
	pme = PM_PFRAME(swap_pte_to_pagemap_entry(pte))
	\| PM_PSHIFT(PAGE_SHIFT) \| PM_SWAP;
	else if (pte_present(pte))
	pme = PM_PFRAME(pte_pfn(pte))
	\| PM_PSHIFT(PAGE_SHIFT) \| PM_PRESENT;
	return pme;
	}

	static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
	struct mm_walk *walk)
	{
	struct vm_area_struct *vma;
	struct pagemapread *pm = walk->private;
	pte_t *pte;
	int err = 0;

	/* find the first VMA at or above 'addr' */
	vma = find_vma(walk->mm, addr);
	for (; addr != end; addr += PAGE_SIZE) {
	u64 pfn = PM_NOT_PRESENT;

	/* check to see if we've left 'vma' behind
	* and need a new, higher one */
	if (vma && (addr >= vma->vm_end))
	vma = find_vma(walk->mm, addr);

	/* check that 'vma' actually covers this address,
	* and that it isn't a huge page vma */
	if (vma && (vma->vm_start <= addr) &&
	!is_vm_hugetlb_page(vma)) {
	pte = pte_offset_map(pmd, addr);
	pfn = pte_to_pagemap_entry(*pte);
	/* unmap before userspace copy */
	pte_unmap(pte);
	}
	err = add_to_pagemap(addr, pfn, pm);
	if (err)
	return err;
	}

	cond_resched();

	return err;
	}

	#ifdef CONFIG_HUGETLB_PAGE
	static u64 huge_pte_to_pagemap_entry(pte_t pte, int offset)
	{
	u64 pme = 0;
	if (pte_present(pte))
	pme = PM_PFRAME(pte_pfn(pte) + offset)
	\| PM_PSHIFT(PAGE_SHIFT) \| PM_PRESENT;
	return pme;
	}

	/* This function walks within one hugetlb entry in the single call */
	static int pagemap_hugetlb_range(pte_t *pte, unsigned long hmask,
	unsigned long addr, unsigned long end,
	struct mm_walk *walk)
	{
	struct pagemapread *pm = walk->private;
	int err = 0;
	u64 pfn;

	for (; addr != end; addr += PAGE_SIZE) {
	int offset = (addr & ~hmask) >> PAGE_SHIFT;
	pfn = huge_pte_to_pagemap_entry(*pte, offset);
	err = add_to_pagemap(addr, pfn, pm);
	if (err)
	return err;
	}

	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 0-55 page frame number (PFN) if present
	* Bits 0-4 swap type if swapped
	* Bits 5-55 swap offset if swapped
	* Bits 55-60 page shift (page size = 1<<page shift)
	* Bit 61 reserved for future use
	* 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.
	*/
	#define PAGEMAP_WALK_SIZE (PMD_SIZE)
	static ssize_t pagemap_read(struct file file, char __user buf,
	size_t count, loff_t *ppos)
	{
	struct task_struct *task = get_proc_task(file->f_path.dentry->d_inode);
	struct mm_struct *mm;
	struct pagemapread pm;
	int ret = -ESRCH;
	struct mm_walk pagemap_walk = {};
	unsigned long src;
	unsigned long svpfn;
	unsigned long start_vaddr;
	unsigned long end_vaddr;
	int copied = 0;

	if (!task)
	goto out;

	ret = -EACCES;
	if (!ptrace_may_access(task, PTRACE_MODE_READ))
	goto out_task;

	ret = -EINVAL;
	/* file position must be aligned */
	if ((*ppos % PM_ENTRY_BYTES) \|\| (count % PM_ENTRY_BYTES))
	goto out_task;

	ret = 0;

	if (!count)
	goto out_task;

	mm = get_task_mm(task);
	if (!mm)
	goto out_task;

	pm.len = PM_ENTRY_BYTES * (PAGEMAP_WALK_SIZE >> PAGE_SHIFT);
	pm.buffer = kmalloc(pm.len, GFP_TEMPORARY);
	ret = -ENOMEM;
	if (!pm.buffer)
	goto out_mm;

	pagemap_walk.pmd_entry = pagemap_pte_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 = TASK_SIZE_OF(task);

	/* watch out for wraparound */
	if (svpfn > TASK_SIZE_OF(task) >> 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;
	/* 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_task:
	put_task_struct(task);
	out:
	return ret;
	}

	const struct file_operations proc_pagemap_operations = {
	.llseek = mem_lseek, /* borrow this */
	.read = pagemap_read,
	};
	#endif /* CONFIG_PROC_PAGE_MONITOR */

	#ifdef CONFIG_NUMA
	extern int show_numa_map(struct seq_file m, void v);

	static const struct seq_operations proc_pid_numa_maps_op = {
	.start = m_start,
	.next = m_next,
	.stop = m_stop,
	.show = show_numa_map,
	};

	static int numa_maps_open(struct inode inode, struct file file)
	{
	return do_maps_open(inode, file, &proc_pid_numa_maps_op);
	}

	const struct file_operations proc_numa_maps_operations = {
	.open = numa_maps_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = seq_release_private,
	};
	#endif