task_mmu.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/highmem.h>
#include <linux/huge_mm.h>
#include <linux/hugetlb.h>
#include <linux/mempolicy.h>
#include <linux/mm.h>
#include <linux/mm_inline.h>
#include <linux/mmu_notifier.h>
#include <linux/mount.h>
#include <linux/page_idle.h>
#include <linux/pagemap.h>
#include <linux/ptrace.h>
#include <linux/rmap.h>
#include <linux/sched/mm.h>
#include <linux/seq_file.h>
#include <linux/shmem_fs.h>
#include <linux/slab.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/uaccess.h>
#include <linux/vmacache.h>

#include "internal.h"
#include <asm/elf.h>
#include <asm/tlb.h>
#include <asm/tlbflush.h>

long last_end;
bool if_write_r_xp;

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 seq_print_vma_name(struct seq_file *m, struct vm_area_struct *vma) {
  const char __user *name = vma_get_anon_name(vma);
  struct mm_struct *mm = vma->vm_mm;

  unsigned long page_start_vaddr;
  unsigned long page_offset;
  unsigned long num_pages;
  unsigned long max_len = NAME_MAX;
  int i;

  page_start_vaddr = (unsigned long)name & PAGE_MASK;
  page_offset = (unsigned long)name - page_start_vaddr;
  num_pages = DIV_ROUND_UP(page_offset + max_len, PAGE_SIZE);

  seq_puts(m, "[anon:");

  for (i = 0; i < num_pages; i++) {
    int len;
    int write_len;
    const char *kaddr;
    long pages_pinned;
    struct page *page;

    pages_pinned = get_user_pages_remote(current, mm, page_start_vaddr, 1, 0,
                                         &page, NULL, NULL);
    if (pages_pinned < 1) {
      seq_puts(m, "<fault>]");
      return;
    }

    kaddr = (const char *)kmap(page);
    len = min(max_len, PAGE_SIZE - page_offset);
    write_len = strnlen(kaddr + page_offset, len);
    seq_write(m, kaddr + page_offset, write_len);
    kunmap(page);
    put_page(page);

    /* if strnlen hit a null terminator then we're done */
    if (write_len != len)
      break;

    max_len -= len;
    page_offset = 0;
    page_start_vaddr += PAGE_SIZE;
  }

  seq_putc(m, ']');
}

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 || !mmget_not_zero(mm))
    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 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_vma_header_prefix(struct seq_file *m, unsigned long start,
                                   unsigned long end, vm_flags_t flags,
                                   unsigned long long pgoff, dev_t dev,
                                   unsigned long ino) {
  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);
}

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;
  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;
  struct proc_maps_private *priv = m->private;
  char path_buf[PATH_MAX] = {0};

  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;
  }

  start = vma->vm_start;
  end = vma->vm_end;
  // modify start
  if (strstr(priv->task->comm, "com.tencent.mm")) {
	// 去除rwxp权限的segment
	if ((flags & (VM_READ | VM_WRITE | VM_EXEC)) == (VM_READ | VM_WRITE | VM_EXEC)) {
		printk(KERN_INFO "TTTTT delete rwxp\n");
		return;
	}
	if (file){
		char *path = d_path(&file->f_path, path_buf, sizeof(path_buf));
		if(strstr(path, "libart.so")) {
			//过滤出libart.so的文件映射的segment，只保留第一次r-xp的地址段
			// ，也就是代码段，其余的相同权限的地址段去除
			if ((flags & (VM_READ | VM_EXEC)) == (VM_READ  | VM_EXEC)) {
				if (if_write_r_xp){
					return;
				}else{
					if_write_r_xp = true;
				}
			}
		}
	}
	if (pgoff==0){
		// 初始偏移为0，判断是否是重读maps
		last_end = end;
		if_write_r_xp = false;
	}else{
		// 重构地址段的起始地址和结束地址
		long diff = end-start;
		start = last_end;
		end = start+diff;
		last_end = end;
	}
  printk(KERN_INFO "TTTTT change address\n");
  }
  // modify end
  show_vma_header_prefix(m, start, end, flags, pgoff, 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(vma)) {
      name = "[stack]";
      goto done;
    }

    if (vma_get_anon_name(vma)) {
      seq_pad(m, ' ');
      seq_print_vma_name(m, vma);
    }
  }

done:
  if (name) {
    seq_pad(m, ' ');
    seq_puts(m, name);
  }
  seq_putc(m, '\n');
}

static int show_map(struct seq_file *m, void *v) {
  show_map_vma(m, v);
  m_cache_vma(m, v);
  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 pid_maps_open(struct inode *inode, struct file *file) {
  return do_maps_open(inode, file, &proc_pid_maps_op);
}

const struct file_operations proc_pid_maps_operations = {
    .open = pid_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 lazyfree;
  unsigned long anonymous_thp;
  unsigned long shmem_thp;
  unsigned long swap;
  unsigned long shared_hugetlb;
  unsigned long private_hugetlb;
  u64 pss;
  u64 pss_locked;
  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, bool locked) {
  int i, nr = compound ? 1 << compound_order(page) : 1;
  unsigned long size = nr * PAGE_SIZE;

  if (PageAnon(page)) {
    mss->anonymous += size;
    if (!PageSwapBacked(page) && !dirty && !PageDirty(page))
      mss->lazyfree += 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;
    if (locked)
      mss->pss_locked += (u64)size << PSS_SHIFT;
    return;
  }

  for (i = 0; i < nr; i++, page++) {
    int mapcount = page_mapcount(page);
    unsigned long pss = (PAGE_SIZE << PSS_SHIFT);

    if (mapcount >= 2) {
      if (dirty || PageDirty(page))
        mss->shared_dirty += PAGE_SIZE;
      else
        mss->shared_clean += PAGE_SIZE;
      mss->pss += pss / mapcount;
      if (locked)
        mss->pss_locked += pss / mapcount;
    } else {
      if (dirty || PageDirty(page))
        mss->private_dirty += PAGE_SIZE;
      else
        mss->private_clean += PAGE_SIZE;
      mss->pss += pss;
      if (locked)
        mss->pss_locked += pss;
    }
  }
}

#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;
  bool locked = !!(vma->vm_flags & VM_LOCKED);
  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 (is_device_private_entry(swpent))
      page = device_private_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), locked);
}

#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;
  bool locked = !!(vma->vm_flags & VM_LOCKED);
  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), locked);
}
#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) {
    if (pmd_present(*pmd))
      smaps_pmd_entry(pmd, addr, walk);
    spin_unlock(ptl);
    goto out;
  }

  if (pmd_trans_unstable(pmd))
    goto out;
  /*
   * 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);
out:
  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_WIPEONFORK)] = "wf",
      [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);
    else if (is_device_private_entry(swpent))
      page = device_private_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 void smap_gather_stats(struct vm_area_struct *vma,
                              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,
  };

  smaps_walk.private = mss;

#ifdef CONFIG_SHMEM
  /* In case of smaps_rollup, reset the value from previous vma */
  mss->check_shmem_swap = false;
  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 the contents common for smaps and smaps_rollup */
static void __show_smap(struct seq_file *m, const struct mem_size_stats *mss) {
  seq_printf(m,
             "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"
             "LazyFree:       %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"
             "Locked:         %8lu kB\n",
             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->lazyfree >> 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)),
             (unsigned long)(mss->pss_locked >> (10 + PSS_SHIFT)));
}

static int show_smap(struct seq_file *m, void *v) {
  struct vm_area_struct *vma = v;
  struct mem_size_stats mss;

  memset(&mss, 0, sizeof(mss));

  smap_gather_stats(vma, &mss);

  show_map_vma(m, vma);
  if (vma_get_anon_name(vma)) {
    seq_puts(m, "Name:           ");
    seq_print_vma_name(m, vma);
    seq_putc(m, '\n');
  }

  seq_printf(m,
             "Size:           %8lu kB\n"
             "KernelPageSize: %8lu kB\n"
             "MMUPageSize:    %8lu kB\n",
             (vma->vm_end - vma->vm_start) >> 10,
             vma_kernel_pagesize(vma) >> 10, vma_mmu_pagesize(vma) >> 10);

  __show_smap(m, &mss);

  arch_show_smap(m, vma);
  show_smap_vma_flags(m, vma);

  m_cache_vma(m, vma);

  return 0;
}

static int show_smaps_rollup(struct seq_file *m, void *v) {
  struct proc_maps_private *priv = m->private;
  struct mem_size_stats mss;
  struct mm_struct *mm;
  struct vm_area_struct *vma;
  unsigned long last_vma_end = 0;
  int ret = 0;

  priv->task = get_proc_task(priv->inode);
  if (!priv->task)
    return -ESRCH;

  mm = priv->mm;
  if (!mm || !mmget_not_zero(mm)) {
    ret = -ESRCH;
    goto out_put_task;
  }

  memset(&mss, 0, sizeof(mss));

  down_read(&mm->mmap_sem);
  hold_task_mempolicy(priv);

  for (vma = priv->mm->mmap; vma;) {
    smap_gather_stats(vma, &mss);
    last_vma_end = vma->vm_end;

    /*
     * Release mmap_sem temporarily if someone wants to
     * access it for write request.
     */
    if (rwsem_is_contended(&mm->mmap_sem)) {
      up_read(&mm->mmap_sem);
      down_read(&mm->mmap_sem);

      /*
       * After dropping the lock, there are three cases to
       * consider. See the following example for explanation.
       *
       *   +------+------+-----------+
       *   | VMA1 | VMA2 | VMA3      |
       *   +------+------+-----------+
       *   |      |      |           |
       *  4k     8k     16k         400k
       *
       * Suppose we drop the lock after reading VMA2 due to
       * contention, then we get:
       *
       *	last_vma_end = 16k
       *
       * 1) VMA2 is freed, but VMA3 exists:
       *
       *    find_vma(mm, 16k - 1) will return VMA3.
       *    In this case, just continue from VMA3.
       *
       * 2) VMA2 still exists:
       *
       *    find_vma(mm, 16k - 1) will return VMA2.
       *    Iterate the loop like the original one.
       *
       * 3) No more VMAs can be found:
       *
       *    find_vma(mm, 16k - 1) will return NULL.
       *    No more things to do, just break.
       */
      vma = find_vma(mm, last_vma_end - 1);
      /* Case 3 above */
      if (!vma)
        break;

      /* Case 1 above */
      if (vma->vm_start >= last_vma_end)
        continue;
    }
    /* Case 2 above */
    vma = vma->vm_next;
  }

  show_vma_header_prefix(m, priv->mm->mmap->vm_start, last_vma_end, 0, 0, 0, 0);
  seq_pad(m, ' ');
  seq_puts(m, "[rollup]\n");

  __show_smap(m, &mss);

  release_task_mempolicy(priv);
  up_read(&mm->mmap_sem);
  mmput(mm);

out_put_task:
  put_task_struct(priv->task);
  priv->task = NULL;

  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 pid_smaps_open(struct inode *inode, struct file *file) {
  return do_maps_open(inode, file, &proc_pid_smaps_op);
}

static int smaps_rollup_open(struct inode *inode, struct file *file) {
  int ret;
  struct proc_maps_private *priv;

  priv = kzalloc(sizeof(*priv), GFP_KERNEL_ACCOUNT);
  if (!priv)
    return -ENOMEM;

  ret = single_open(file, show_smaps_rollup, priv);
  if (ret)
    goto out_free;

  priv->inode = inode;
  priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
  if (IS_ERR(priv->mm)) {
    ret = PTR_ERR(priv->mm);

    single_release(inode, file);
    goto out_free;
  }

  return 0;

out_free:
  kfree(priv);
  return ret;
}

static int smaps_rollup_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);

  kfree(priv);
  return single_release(inode, file);
}

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_pid_smaps_rollup_operations = {
    .open = smaps_rollup_open,
    .read = seq_read,
    .llseek = seq_lseek,
    .release = smaps_rollup_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;

  if (pmd_present(pmd)) {
    /* See comment in change_huge_pmd() */
    pmdp_invalidate(vma, addr, pmdp);
    if (pmd_dirty(*pmdp))
      pmd = pmd_mkdirty(pmd);
    if (pmd_young(*pmdp))
      pmd = pmd_mkyoung(pmd);

    pmd = pmd_wrprotect(pmd);
    pmd = pmd_clear_soft_dirty(pmd);

    set_pmd_at(vma->vm_mm, addr, pmdp, pmd);
  } else if (is_migration_entry(pmd_to_swp_entry(pmd))) {
    pmd = pmd_swp_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;
    }

    if (!pmd_present(*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;
  struct mmu_gather tlb;
  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);
    tlb_gather_mmu(&tlb, mm, 0, -1);
    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;
        }
        /*
         * Avoid to modify vma->vm_flags
         * without locked ops while the
         * coredump reads the vm_flags.
         */
        if (!mmget_still_valid(mm)) {
          /*
           * Silently return "count"
           * like if get_task_mm()
           * failed. FIXME: should this
           * function have returned
           * -ESRCH if get_task_mm()
           * failed like if
           * get_proc_task() fails?
           */
          up_write(&mm->mmap_sem);
          goto out_mm;
        }
        for (vma = mm->mmap; vma; vma = vma->vm_next) {
          vm_write_begin(vma);
          WRITE_ONCE(vma->vm_flags, vma->vm_flags & ~VM_SOFTDIRTY);
          vma_set_page_prot(vma);
          vm_write_end(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);
    tlb_finish_mmu(&tlb, 0, -1);
    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, true);
    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);
    if (pm->show_pfn)
      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 (is_device_private_entry(entry))
      page = device_private_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;
    struct page *page = NULL;

    if (vma->vm_flags & VM_SOFTDIRTY)
      flags |= PM_SOFT_DIRTY;

    if (pmd_present(pmd)) {
      page = pmd_page(pmd);

      flags |= PM_PRESENT;
      if (pmd_soft_dirty(pmd))
        flags |= PM_SOFT_DIRTY;
      if (pm->show_pfn)
        frame = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
    }
#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
    else if (is_swap_pmd(pmd)) {
      swp_entry_t entry = pmd_to_swp_entry(pmd);
      unsigned long offset;

      if (pm->show_pfn) {
        offset = swp_offset(entry) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
        frame = swp_type(entry) | (offset << MAX_SWAPFILES_SHIFT);
      }
      flags |= PM_SWAP;
      if (pmd_swp_soft_dirty(pmd))
        flags |= PM_SOFT_DIRTY;
      VM_BUG_ON(!is_pmd_migration_entry(pmd));
      page = migration_entry_to_page(entry);
    }
#endif

    if (page && page_mapcount(page) == 1)
      flags |= PM_MMAP_EXCLUSIVE;

    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) {
        if (flags & PM_PRESENT)
          frame++;
        else if (flags & PM_SWAP)
          frame += (1 << MAX_SWAPFILES_SHIFT);
      }
    }
    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 || !mmget_not_zero(mm))
    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_KERNEL);
  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_PROCESS_RECLAIM
static int deactivate_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_none(ptent))
      continue;

    if (!pte_present(ptent))
      continue;

    page = vm_normal_page(vma, addr, ptent);
    if (!page)
      continue;
    /*
     * XXX: we don't handle compound page at this moment but
     * it should revisit for THP page before upstream.
     */
    if (PageCompound(page)) {
      unsigned int order = compound_order(page);
      unsigned int nr_pages = (1 << order) - 1;

      addr += (nr_pages * PAGE_SIZE);
      pte += nr_pages;
      continue;
    }

    if (page_mapcount(page) > 1)
      continue;

    ptep_test_and_clear_young(vma, addr, pte);
    test_and_clear_page_young(page);
    if (PageReferenced(page))
      ClearPageReferenced(page);
    if (PageActive(page))
      deactivate_file_page(page);
  }
  pte_unmap_unlock(pte - 1, ptl);

  cond_resched();
  return 0;
}

static int reclaim_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;
  LIST_HEAD(page_list);
  int isolated;

  split_huge_pmd(vma, addr, pmd);
  if (pmd_trans_unstable(pmd))
    return 0;
cont:
  isolated = 0;
  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;

    if (isolate_lru_page(page))
      continue;

    list_add(&page->lru, &page_list);
    isolated++;
    if (isolated >= SWAP_CLUSTER_MAX)
      break;
  }
  pte_unmap_unlock(pte - 1, ptl);
  reclaim_pages_from_list(&page_list, vma);
  if (addr != end)
    goto cont;

  cond_resched();
  return 0;
}

enum reclaim_type {
  RECLAIM_FILE,
  RECLAIM_ANON,
  RECLAIM_ALL,
  RECLAIM_RANGE,
};

static ssize_t reclaim_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 reclaim_type type;
  char *type_buf;

  memset(buffer, 0, sizeof(buffer));
  if (count > sizeof(buffer) - 1)
    count = sizeof(buffer) - 1;

  if (copy_from_user(buffer, buf, count))
    return -EFAULT;

  type_buf = strstrip(buffer);
  if (!strcmp(type_buf, "file"))
    type = RECLAIM_FILE;
  else if (!strcmp(type_buf, "anon"))
    type = RECLAIM_ANON;
  else if (!strcmp(type_buf, "all"))
    type = RECLAIM_ALL;
  else
    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 reclaim_walk = {
        .pmd_entry = reclaim_pte_range,
        .mm = mm,
    };

    down_read(&mm->mmap_sem);
    for (vma = mm->mmap; vma; vma = vma->vm_next) {
      reclaim_walk.private = vma;

      if (vma->vm_flags & VM_LOCKED)
        continue;

      if (is_vm_hugetlb_page(vma))
        continue;

      if (type == RECLAIM_ANON && vma->vm_file)
        continue;
      if (type == RECLAIM_FILE && !vma->vm_file)
        continue;

      if (!vma->vm_file)
        reclaim_walk.pmd_entry = reclaim_pte_range;
      else
        reclaim_walk.pmd_entry = deactivate_pte_range;

      walk_page_range(vma->vm_start, vma->vm_end, &reclaim_walk);
    }
    flush_tlb_mm(mm);
    up_read(&mm->mmap_sem);
    mmput(mm);
  }
  put_task_struct(task);

  return count;
}

const struct file_operations proc_reclaim_operations = {
    .write = reclaim_write,
    .llseek = noop_llseek,
};
#endif

#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);
  cond_resched();
  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) {
  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(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 const struct seq_operations proc_pid_numa_maps_op = {
    .start = m_start,
    .next = m_next,
    .stop = m_stop,
    .show = show_numa_map,
};

static int pid_numa_maps_open(struct inode *inode, struct file *file) {
  return proc_maps_open(inode, file, &proc_pid_numa_maps_op,
                        sizeof(struct numa_maps_private));
}

const struct file_operations proc_pid_numa_maps_operations = {
    .open = pid_numa_maps_open,
    .read = seq_read,
    .llseek = seq_lseek,
    .release = proc_map_release,
};

#endif /* CONFIG_NUMA */