1 files changed, 444 insertions, 248 deletions

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 8043a3eab52..49958cffbd8 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -5,14 +5,18 @@
 #include <linux/highmem.h>
 #include <linux/ptrace.h>
 #include <linux/pagemap.h>
+#include <linux/ptrace.h>
 #include <linux/mempolicy.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+#include <linux/seq_file.h>
 
 #include <asm/elf.h>
 #include <asm/uaccess.h>
 #include <asm/tlbflush.h>
 #include "internal.h"
 
-char *task_mem(struct mm_struct *mm, char *buffer)
+void task_mem(struct seq_file *m, struct mm_struct *mm)
 {
 	unsigned long data, text, lib;
 	unsigned long hiwater_vm, total_vm, hiwater_rss, total_rss;
@@ -34,7 +38,7 @@ char *task_mem(struct mm_struct *mm, char *buffer)
 	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;
-	buffer += sprintf(buffer,
+	seq_printf(m,
 		"VmPeak:\t%8lu kB\n"
 		"VmSize:\t%8lu kB\n"
 		"VmLck:\t%8lu kB\n"
@@ -53,7 +57,6 @@ char *task_mem(struct mm_struct *mm, char *buffer)
 		data << (PAGE_SHIFT-10),
 		mm->stack_vm << (PAGE_SHIFT-10), text, lib,
 		(PTRS_PER_PTE*sizeof(pte_t)*mm->nr_ptes) >> 10);
-	return buffer;
 }
 
 unsigned long task_vsize(struct mm_struct *mm)
@@ -72,7 +75,7 @@ int task_statm(struct mm_struct *mm, int *shared, int *text,
 	return mm->total_vm;
 }
 
-int proc_exe_link(struct inode *inode, struct dentry **dentry, struct vfsmount **mnt)
+int proc_exe_link(struct inode *inode, struct path *path)
 {
 	struct vm_area_struct * vma;
 	int result = -ENOENT;
@@ -95,8 +98,8 @@ int proc_exe_link(struct inode *inode, struct dentry **dentry, struct vfsmount *
 	}
 
 	if (vma) {
-		*mnt = mntget(vma->vm_file->f_path.mnt);
-		*dentry = dget(vma->vm_file->f_path.dentry);
+		*path = vma->vm_file->f_path;
+		path_get(&vma->vm_file->f_path);
 		result = 0;
 	}
 
@@ -114,24 +117,124 @@ static void pad_len_spaces(struct seq_file *m, int len)
 	seq_printf(m, "%*c", len, ' ');
 }
 
-struct mem_size_stats
+static void vma_stop(struct proc_maps_private *priv, 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;
-};
+	if (vma && vma != priv->tail_vma) {
+		struct mm_struct *mm = vma->vm_mm;
+		up_read(&mm->mmap_sem);
+		mmput(mm);
+	}
+}
 
-struct pmd_walker {
-	struct vm_area_struct *vma;
-	void *private;
-	void (*action)(struct vm_area_struct *, pmd_t *, unsigned long,
-		       unsigned long, void *);
-};
+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;
+
+	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 int show_map_internal(struct seq_file *m, void *v, struct mem_size_stats *mss)
+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 int show_map(struct seq_file *m, void *v)
 {
 	struct proc_maps_private *priv = m->private;
 	struct task_struct *task = priv->task;
@@ -168,7 +271,7 @@ static int show_map_internal(struct seq_file *m, void *v, struct mem_size_stats
 	 */
 	if (file) {
 		pad_len_spaces(m, len);
-		seq_path(m, file->f_path.mnt, file->f_path.dentry, "\n");
+		seq_path(m, &file->f_path, "\n");
 	} else {
 		const char *name = arch_vma_name(vma);
 		if (!name) {
@@ -191,41 +294,71 @@ static int show_map_internal(struct seq_file *m, void *v, struct mem_size_stats
 	}
 	seq_putc(m, '\n');
 
-	if (mss)
-		seq_printf(m,
-			   "Size:           %8lu kB\n"
-			   "Rss:            %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",
-			   (vma->vm_end - vma->vm_start) >> 10,
-			   mss->resident >> 10,
-			   mss->shared_clean  >> 10,
-			   mss->shared_dirty  >> 10,
-			   mss->private_clean >> 10,
-			   mss->private_dirty >> 10,
-			   mss->referenced >> 10);
-
 	if (m->count < m->size)  /* vma is copied successfully */
 		m->version = (vma != get_gate_vma(task))? vma->vm_start: 0;
 	return 0;
 }
 
-static int show_map(struct seq_file *m, void *v)
+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 show_map_internal(m, v, NULL);
+	return do_maps_open(inode, file, &proc_pid_maps_op);
 }
 
-static void smaps_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
-			    unsigned long addr, unsigned long end,
-			    void *private)
+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;
+	u64 pss;
+};
+
+static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
+			   void *private)
 {
 	struct mem_size_stats *mss = 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) {
@@ -242,26 +375,88 @@ static void smaps_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 		/* Accumulate the size in pages that have been accessed. */
 		if (pte_young(ptent) || PageReferenced(page))
 			mss->referenced += PAGE_SIZE;
-		if (page_mapcount(page) >= 2) {
+		mapcount = page_mapcount(page);
+		if (mapcount >= 2) {
 			if (pte_dirty(ptent))
 				mss->shared_dirty += PAGE_SIZE;
 			else
 				mss->shared_clean += PAGE_SIZE;
+			mss->pss += (PAGE_SIZE << PSS_SHIFT) / mapcount;
 		} else {
 			if (pte_dirty(ptent))
 				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 struct mm_walk smaps_walk = { .pmd_entry = smaps_pte_range };
+
+static int show_smap(struct seq_file *m, void *v)
+{
+	struct vm_area_struct *vma = v;
+	struct mem_size_stats mss;
+	int ret;
+
+	memset(&mss, 0, sizeof mss);
+	mss.vma = vma;
+	if (vma->vm_mm && !is_vm_hugetlb_page(vma))
+		walk_page_range(vma->vm_mm, vma->vm_start, vma->vm_end,
+				&smaps_walk, &mss);
+
+	ret = show_map(m, v);
+	if (ret)
+		return ret;
+
+	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",
+		   (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);
+
+	return ret;
+}
+
+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);
 }
 
-static void clear_refs_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
-				 unsigned long addr, unsigned long end,
-				 void *private)
+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, void *private)
 {
+	struct vm_area_struct *vma = private;
 	pte_t *pte, ptent;
 	spinlock_t *ptl;
 	struct page *page;
@@ -282,235 +477,248 @@ static void clear_refs_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 	}
 	pte_unmap_unlock(pte - 1, ptl);
 	cond_resched();
+	return 0;
 }
 
-static inline void walk_pmd_range(struct pmd_walker *walker, pud_t *pud,
-				  unsigned long addr, unsigned long end)
+static struct mm_walk clear_refs_walk = { .pmd_entry = clear_refs_pte_range };
+
+static ssize_t clear_refs_write(struct file *file, const char __user *buf,
+				size_t count, loff_t *ppos)
 {
-	pmd_t *pmd;
-	unsigned long next;
+	struct task_struct *task;
+	char buffer[PROC_NUMBUF], *end;
+	struct mm_struct *mm;
+	struct vm_area_struct *vma;
 
-	for (pmd = pmd_offset(pud, addr); addr != end;
-	     pmd++, addr = next) {
-		next = pmd_addr_end(addr, end);
-		if (pmd_none_or_clear_bad(pmd))
-			continue;
-		walker->action(walker->vma, pmd, addr, next, walker->private);
+	memset(buffer, 0, sizeof(buffer));
+	if (count > sizeof(buffer) - 1)
+		count = sizeof(buffer) - 1;
+	if (copy_from_user(buffer, buf, count))
+		return -EFAULT;
+	if (!simple_strtol(buffer, &end, 0))
+		return -EINVAL;
+	if (*end == '\n')
+		end++;
+	task = get_proc_task(file->f_path.dentry->d_inode);
+	if (!task)
+		return -ESRCH;
+	mm = get_task_mm(task);
+	if (mm) {
+		down_read(&mm->mmap_sem);
+		for (vma = mm->mmap; vma; vma = vma->vm_next)
+			if (!is_vm_hugetlb_page(vma))
+				walk_page_range(mm, vma->vm_start, vma->vm_end,
+						&clear_refs_walk, vma);
+		flush_tlb_mm(mm);
+		up_read(&mm->mmap_sem);
+		mmput(mm);
 	}
+	put_task_struct(task);
+	if (end - buffer == 0)
+		return -EIO;
+	return end - buffer;
 }
 
-static inline void walk_pud_range(struct pmd_walker *walker, pgd_t *pgd,
-				  unsigned long addr, unsigned long end)
-{
-	pud_t *pud;
-	unsigned long next;
+const struct file_operations proc_clear_refs_operations = {
+	.write		= clear_refs_write,
+};
 
-	for (pud = pud_offset(pgd, addr); addr != end;
-	     pud++, addr = next) {
-		next = pud_addr_end(addr, end);
-		if (pud_none_or_clear_bad(pud))
-			continue;
-		walk_pmd_range(walker, pud, addr, next);
+struct pagemapread {
+	char __user *out, *end;
+};
+
+#define PM_ENTRY_BYTES sizeof(u64)
+#define PM_RESERVED_BITS    3
+#define PM_RESERVED_OFFSET  (64 - PM_RESERVED_BITS)
+#define PM_RESERVED_MASK    (((1LL<<PM_RESERVED_BITS)-1) << PM_RESERVED_OFFSET)
+#define PM_SPECIAL(nr)      (((nr) << PM_RESERVED_OFFSET) | PM_RESERVED_MASK)
+#define PM_NOT_PRESENT      PM_SPECIAL(1LL)
+#define PM_SWAP             PM_SPECIAL(2LL)
+#define PM_END_OF_BUFFER    1
+
+static int add_to_pagemap(unsigned long addr, u64 pfn,
+			  struct pagemapread *pm)
+{
+	/*
+	 * Make sure there's room in the buffer for an
+	 * entire entry.  Otherwise, only copy part of
+	 * the pfn.
+	 */
+	if (pm->out + PM_ENTRY_BYTES >= pm->end) {
+		if (copy_to_user(pm->out, &pfn, pm->end - pm->out))
+			return -EFAULT;
+		pm->out = pm->end;
+		return PM_END_OF_BUFFER;
 	}
+
+	if (put_user(pfn, pm->out))
+		return -EFAULT;
+	pm->out += PM_ENTRY_BYTES;
+	return 0;
 }
 
-/*
- * walk_page_range - walk the page tables of a VMA with a callback
- * @vma - VMA to walk
- * @action - callback invoked for every bottom-level (PTE) page table
- * @private - private data passed to the callback function
- *
- * Recursively walk the page table for the memory area in a VMA, calling
- * a callback for every bottom-level (PTE) page table.
- */
-static inline void walk_page_range(struct vm_area_struct *vma,
-				   void (*action)(struct vm_area_struct *,
-						  pmd_t *, unsigned long,
-						  unsigned long, void *),
-				   void *private)
+static int pagemap_pte_hole(unsigned long start, unsigned long end,
+				void *private)
 {
-	unsigned long addr = vma->vm_start;
-	unsigned long end = vma->vm_end;
-	struct pmd_walker walker = {
-		.vma		= vma,
-		.private	= private,
-		.action		= action,
-	};
-	pgd_t *pgd;
-	unsigned long next;
-
-	for (pgd = pgd_offset(vma->vm_mm, addr); addr != end;
-	     pgd++, addr = next) {
-		next = pgd_addr_end(addr, end);
-		if (pgd_none_or_clear_bad(pgd))
-			continue;
-		walk_pud_range(&walker, pgd, addr, next);
+	struct pagemapread *pm = 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 int show_smap(struct seq_file *m, void *v)
+u64 swap_pte_to_pagemap_entry(pte_t pte)
 {
-	struct vm_area_struct *vma = v;
-	struct mem_size_stats mss;
-
-	memset(&mss, 0, sizeof mss);
-	if (vma->vm_mm && !is_vm_hugetlb_page(vma))
-		walk_page_range(vma, smaps_pte_range, &mss);
-	return show_map_internal(m, v, &mss);
+	swp_entry_t e = pte_to_swp_entry(pte);
+	return PM_SWAP | swp_type(e) | (swp_offset(e) << MAX_SWAPFILES_SHIFT);
 }
 
-void clear_refs_smap(struct mm_struct *mm)
+static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
+			     void *private)
 {
-	struct vm_area_struct *vma;
+	struct pagemapread *pm = private;
+	pte_t *pte;
+	int err = 0;
+
+	for (; addr != end; addr += PAGE_SIZE) {
+		u64 pfn = PM_NOT_PRESENT;
+		pte = pte_offset_map(pmd, addr);
+		if (is_swap_pte(*pte))
+			pfn = swap_pte_to_pagemap_entry(*pte);
+		else if (pte_present(*pte))
+			pfn = pte_pfn(*pte);
+		/* unmap so we're not in atomic when we copy to userspace */
+		pte_unmap(pte);
+		err = add_to_pagemap(addr, pfn, pm);
+		if (err)
+			return err;
+	}
 
-	down_read(&mm->mmap_sem);
-	for (vma = mm->mmap; vma; vma = vma->vm_next)
-		if (vma->vm_mm && !is_vm_hugetlb_page(vma))
-			walk_page_range(vma, clear_refs_pte_range, NULL);
-	flush_tlb_mm(mm);
-	up_read(&mm->mmap_sem);
+	cond_resched();
+
+	return err;
 }
 
-static void *m_start(struct seq_file *m, loff_t *pos)
+static struct mm_walk pagemap_walk = {
+	.pmd_entry = pagemap_pte_range,
+	.pte_hole = pagemap_pte_hole
+};
+
+/*
+ * /proc/pid/pagemap - an array mapping virtual pages to pfns
+ *
+ * For each page in the address space, this file contains one 64-bit
+ * entry representing the corresponding physical page frame number
+ * (PFN) if the page is present. If there is a swap entry for the
+ * physical page, then an encoding of the swap file number and the
+ * page's offset into the swap file are returned. If no page is
+ * present at all, PM_NOT_PRESENT is returned. 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 proc_maps_private *priv = m->private;
-	unsigned long last_addr = m->version;
+	struct task_struct *task = get_proc_task(file->f_path.dentry->d_inode);
+	struct page **pages, *page;
+	unsigned long uaddr, uend;
 	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;
+	struct pagemapread pm;
+	int pagecount;
+	int ret = -ESRCH;
 
-	/*
-	 * 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 (!task)
+		goto out;
 
-	if (last_addr == -1UL)
-		return NULL;
+	ret = -EACCES;
+	if (!ptrace_may_attach(task))
+		goto out;
 
-	priv->task = get_pid_task(priv->pid, PIDTYPE_PID);
-	if (!priv->task)
-		return NULL;
+	ret = -EINVAL;
+	/* file position must be aligned */
+	if (*ppos % PM_ENTRY_BYTES)
+		goto out;
 
-	mm = mm_for_maps(priv->task);
+	ret = 0;
+	mm = get_task_mm(task);
 	if (!mm)
-		return NULL;
-
-	priv->tail_vma = tail_vma = get_gate_vma(priv->task);
-
-	/* Start with last addr hint */
-	if (last_addr && (vma = find_vma(mm, last_addr))) {
-		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;
-	}
+	ret = -ENOMEM;
+	uaddr = (unsigned long)buf & PAGE_MASK;
+	uend = (unsigned long)(buf + count);
+	pagecount = (PAGE_ALIGN(uend) - uaddr) / PAGE_SIZE;
+	pages = kmalloc(pagecount * sizeof(struct page *), GFP_KERNEL);
+	if (!pages)
+		goto out_task;
 
-	if (l != mm->map_count)
-		tail_vma = NULL; /* After gate vma */
+	down_read(&current->mm->mmap_sem);
+	ret = get_user_pages(current, current->mm, uaddr, pagecount,
+			     1, 0, pages, NULL);
+	up_read(&current->mm->mmap_sem);
 
-out:
-	if (vma)
-		return vma;
+	if (ret < 0)
+		goto out_free;
 
-	/* End of vmas has been reached */
-	m->version = (tail_vma != NULL)? 0: -1UL;
-	up_read(&mm->mmap_sem);
-	mmput(mm);
-	return tail_vma;
-}
+	pm.out = buf;
+	pm.end = buf + count;
 
-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);
+	if (!ptrace_may_attach(task)) {
+		ret = -EIO;
+	} else {
+		unsigned long src = *ppos;
+		unsigned long svpfn = src / PM_ENTRY_BYTES;
+		unsigned long start_vaddr = svpfn << PAGE_SHIFT;
+		unsigned long 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 = walk_page_range(mm, start_vaddr, end_vaddr,
+					&pagemap_walk, &pm);
+		if (ret == PM_END_OF_BUFFER)
+			ret = 0;
+		/* don't need mmap_sem for these, but this looks cleaner */
+		*ppos += pm.out - buf;
+		if (!ret)
+			ret = pm.out - buf;
 	}
-}
-
-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 struct seq_operations proc_pid_maps_op = {
-	.start	= m_start,
-	.next	= m_next,
-	.stop	= m_stop,
-	.show	= show_map
-};
-
-static struct seq_operations proc_pid_smaps_op = {
-	.start	= m_start,
-	.next	= m_next,
-	.stop	= m_stop,
-	.show	= show_smap
-};
 
-static int do_maps_open(struct inode *inode, struct file *file,
-			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);
-		}
+	for (; pagecount; pagecount--) {
+		page = pages[pagecount-1];
+		if (!PageReserved(page))
+			SetPageDirty(page);
+		page_cache_release(page);
 	}
+	mmput(mm);
+out_free:
+	kfree(pages);
+out_task:
+	put_task_struct(task);
+out:
 	return ret;
 }
 
-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,
+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);
@@ -526,7 +734,7 @@ static int show_numa_map_checked(struct seq_file *m, void *v)
 	return show_numa_map(m, v);
 }
 
-static struct seq_operations proc_pid_numa_maps_op = {
+static const struct seq_operations proc_pid_numa_maps_op = {
         .start  = m_start,
         .next   = m_next,
         .stop   = m_stop,
@@ -545,15 +753,3 @@ const struct file_operations proc_numa_maps_operations = {
 	.release	= seq_release_private,
 };
 #endif
-
-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,
-};