task_mmu.c

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#include <linux/mm.h>
#include <linux/hugetlb.h>
#include <linux/huge_mm.h>
#include <linux/mount.h>
#include <linux/seq_file.h>
#include <linux/highmem.h>
#include <linux/ptrace.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/mempolicy.h>
#include <linux/rmap.h>
#include <linux/swap.h>
#include <linux/swapops.h>

#include <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"
        "VmPin:\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 << (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),
        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;
}

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);
    *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, ' ');
}

#ifdef CONFIG_NUMA
/*
 * These functions are for numa_maps but called in generic **maps seq_file
 * ->start(), ->stop() ops.
 *
 * numa_maps scans all vmas under mmap_sem and checks their mempolicy.
 * Each mempolicy object is controlled by reference counting. The problem here
 * is how to avoid accessing dead mempolicy object.
 *
 * Because we're holding mmap_sem while reading seq_file, it's safe to access
 * each vma's mempolicy, no vma objects will never drop refs to mempolicy.
 *
 * A task's mempolicy (task->mempolicy) has different behavior. task->mempolicy
 * is set and replaced under mmap_sem but unrefed and cleared under task_lock().
 * So, without task_lock(), we cannot trust get_vma_policy() because we cannot
 * gurantee the task never exits under us. But taking task_lock() around
 * get_vma_plicy() causes lock order problem.
 *
 * To access task->mempolicy without lock, we hold a reference count of an
 * object pointed by task->mempolicy and remember it. This will guarantee
 * that task->mempolicy points to an alive object or NULL in numa_maps accesses.
 */
static void hold_task_mempolicy(struct proc_maps_private *priv)
{
    struct task_struct *task = priv->task;

    task_lock(task);
    priv->task_mempolicy = task->mempolicy;
    mpol_get(priv->task_mempolicy);
    task_unlock(task);
}
static void release_task_mempolicy(struct proc_maps_private *priv)
{
    mpol_put(priv->task_mempolicy);
}
#else
static void hold_task_mempolicy(struct proc_maps_private *priv)
{
}
static void release_task_mempolicy(struct proc_maps_private *priv)
{
}
#endif

static void vma_stop(struct proc_maps_private *priv, struct vm_area_struct *vma)
{
    if (vma && vma != priv->tail_vma) {
        struct mm_struct *mm = vma->vm_mm;
        release_task_mempolicy(priv);
        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 ERR_PTR(-ESRCH);

    mm = mm_access(priv->task, PTRACE_MODE_READ);
    if (!mm || IS_ERR(mm))
        return mm;
    down_read(&mm->mmap_sem);

    tail_vma = get_gate_vma(priv->task->mm);
    priv->tail_vma = tail_vma;
    hold_task_mempolicy(priv);
    /* 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;

    release_task_mempolicy(priv);
    /* 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;

    if (!IS_ERR(vma))
        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, int is_pid)
{
    struct mm_struct *mm = vma->vm_mm;
    struct file *file = vma->vm_file;
    struct proc_maps_private *priv = m->private;
    struct task_struct *task = priv->task;
    vm_flags_t flags = vma->vm_flags;
    unsigned long ino = 0;
    unsigned long long pgoff = 0;
    unsigned long start, end;
    dev_t dev = 0;
    int len;
    const char *name = NULL;

    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 (stack_guard_page_start(vma, start))
        start += PAGE_SIZE;
    end = vma->vm_end;
    if (stack_guard_page_end(vma, end))
        end -= PAGE_SIZE;

    seq_printf(m, "%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu %n",
            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, &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");
        goto done;
    }

    name = arch_vma_name(vma);
    if (!name) {
        pid_t tid;

        if (!mm) {
            name = "[vdso]";
            goto done;
        }

        if (vma->vm_start <= mm->brk &&
            vma->vm_end >= mm->start_brk) {
            name = "[heap]";
            goto done;
        }

        tid = vm_is_stack(task, vma, is_pid);

        if (tid != 0) {
            /*
             * Thread stack in /proc/PID/task/TID/maps or
             * the main process stack.
             */
            if (!is_pid || (vma->vm_start <= mm->start_stack &&
                vma->vm_end >= mm->start_stack)) {
                name = "[stack]";
            } else {
                /* Thread stack in /proc/PID/maps */
                pad_len_spaces(m, len);
                seq_printf(m, "[stack:%d]", tid);
            }
        }
    }

done:
    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, int is_pid)
{
    struct vm_area_struct *vma = v;
    struct proc_maps_private *priv = m->private;
    struct task_struct *task = priv->task;

    show_map_vma(m, vma, is_pid);

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

static int show_pid_map(struct seq_file *m, void *v)
{
    return show_map(m, v, 1);
}

static int show_tid_map(struct seq_file *m, void *v)
{
    return show_map(m, v, 0);
}

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

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

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

static int tid_maps_open(struct inode *inode, struct file *file)
{
    return do_maps_open(inode, file, &proc_tid_maps_op);
}

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

const struct file_operations proc_tid_maps_operations = {
    .open       = tid_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 anonymous;
    unsigned long anonymous_thp;
    unsigned long swap;
    unsigned long nonlinear;
    u64 pss;
};


static void smaps_pte_entry(pte_t ptent, unsigned long addr,
        unsigned long ptent_size, struct mm_walk *walk)
{
    struct mem_size_stats *mss = walk->private;
    struct vm_area_struct *vma = mss->vma;
    pgoff_t pgoff = linear_page_index(vma, addr);
    struct page *page = NULL;
    int mapcount;

    if (pte_present(ptent)) {
        page = vm_normal_page(vma, addr, ptent);
    } else if (is_swap_pte(ptent)) {
        swp_entry_t swpent = pte_to_swp_entry(ptent);

        if (!non_swap_entry(swpent))
            mss->swap += ptent_size;
        else if (is_migration_entry(swpent))
            page = migration_entry_to_page(swpent);
    } else if (pte_file(ptent)) {
        if (pte_to_pgoff(ptent) != pgoff)
            mss->nonlinear += ptent_size;
    }

    if (!page)
        return;

    if (PageAnon(page))
        mss->anonymous += ptent_size;

    if (page->index != pgoff)
        mss->nonlinear += ptent_size;

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

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;
    spinlock_t *ptl;

    if (pmd_trans_huge_lock(pmd, vma) == 1) {
        smaps_pte_entry(*(pte_t *)pmd, addr, HPAGE_PMD_SIZE, walk);
        spin_unlock(&walk->mm->page_table_lock);
        mss->anonymous_thp += HPAGE_PMD_SIZE;
        return 0;
    }

    if (pmd_trans_unstable(pmd))
        return 0;
    /*
     * The mmap_sem held all the way back in m_start() is what
     * keeps khugepaged out of here and from collapsing things
     * in here.
     */
    pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
    for (; addr != end; pte++, addr += PAGE_SIZE)
        smaps_pte_entry(*pte, addr, PAGE_SIZE, walk);
    pte_unmap_unlock(pte - 1, ptl);
    cond_resched();
    return 0;
}

static int show_smap(struct seq_file *m, void *v, int is_pid)
{
    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, is_pid);

    seq_printf(m,
           "Size:           %8lu kB\n"
           "Rss:            %8lu kB\n"
           "Pss:            %8lu kB\n"
           "Shared_Clean:   %8lu kB\n"
           "Shared_Dirty:   %8lu kB\n"
           "Private_Clean:  %8lu kB\n"
           "Private_Dirty:  %8lu kB\n"
           "Referenced:     %8lu kB\n"
           "Anonymous:      %8lu kB\n"
           "AnonHugePages:  %8lu kB\n"
           "Swap:           %8lu kB\n"
           "KernelPageSize: %8lu kB\n"
           "MMUPageSize:    %8lu kB\n"
           "Locked:         %8lu kB\n",
           (vma->vm_end - vma->vm_start) >> 10,
           mss.resident >> 10,
           (unsigned long)(mss.pss >> (10 + PSS_SHIFT)),
           mss.shared_clean  >> 10,
           mss.shared_dirty  >> 10,
           mss.private_clean >> 10,
           mss.private_dirty >> 10,
           mss.referenced >> 10,
           mss.anonymous >> 10,
           mss.anonymous_thp >> 10,
           mss.swap >> 10,
           vma_kernel_pagesize(vma) >> 10,
           vma_mmu_pagesize(vma) >> 10,
           (vma->vm_flags & VM_LOCKED) ?
            (unsigned long)(mss.pss >> (10 + PSS_SHIFT)) : 0);

    if (vma->vm_flags & VM_NONLINEAR)
        seq_printf(m, "Nonlinear:      %8lu kB\n",
                mss.nonlinear >> 10);

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

static int show_pid_smap(struct seq_file *m, void *v)
{
    return show_smap(m, v, 1);
}

static int show_tid_smap(struct seq_file *m, void *v)
{
    return show_smap(m, v, 0);
}

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

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

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

static int tid_smaps_open(struct inode *inode, struct file *file)
{
    return do_maps_open(inode, file, &proc_tid_smaps_op);
}

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

const struct file_operations proc_tid_smaps_operations = {
    .open       = tid_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;

    split_huge_page_pmd(walk->mm, pmd);
    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 (!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;
    int type;
    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, &type);
    if (rv < 0)
        return rv;
    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,
};

typedef struct {
    u64 pme;
} pagemap_entry_t;

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

#define PAGEMAP_WALK_SIZE   (PMD_SIZE)
#define PAGEMAP_WALK_MASK   (PMD_MASK)

#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_FILE             PM_STATUS(1LL)
#define PM_NOT_PRESENT      PM_PSHIFT(PAGE_SHIFT)
#define PM_END_OF_BUFFER    1

static inline pagemap_entry_t make_pme(u64 val)
{
    return (pagemap_entry_t) { .pme = val };
}

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;
    int err = 0;
    pagemap_entry_t pme = make_pme(PM_NOT_PRESENT);

    for (addr = start; addr < end; addr += PAGE_SIZE) {
        err = add_to_pagemap(addr, &pme, pm);
        if (err)
            break;
    }
    return err;
}

static void pte_to_pagemap_entry(pagemap_entry_t *pme,
        struct vm_area_struct *vma, unsigned long addr, pte_t pte)
{
    u64 frame, flags;
    struct page *page = NULL;

    if (pte_present(pte)) {
        frame = pte_pfn(pte);
        flags = PM_PRESENT;
        page = vm_normal_page(vma, addr, pte);
    } else if (is_swap_pte(pte)) {
        swp_entry_t entry = pte_to_swp_entry(pte);

        frame = swp_type(entry) |
            (swp_offset(entry) << MAX_SWAPFILES_SHIFT);
        flags = PM_SWAP;
        if (is_migration_entry(entry))
            page = migration_entry_to_page(entry);
    } else {
        *pme = make_pme(PM_NOT_PRESENT);
        return;
    }

    if (page && !PageAnon(page))
        flags |= PM_FILE;

    *pme = make_pme(PM_PFRAME(frame) | PM_PSHIFT(PAGE_SHIFT) | flags);
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
static void thp_pmd_to_pagemap_entry(pagemap_entry_t *pme,
                    pmd_t pmd, int offset)
{
    /*
     * Currently pmd for thp is always present because thp can not be
     * swapped-out, migrated, or HWPOISONed (split in such cases instead.)
     * This if-check is just to prepare for future implementation.
     */
    if (pmd_present(pmd))
        *pme = make_pme(PM_PFRAME(pmd_pfn(pmd) + offset)
                | PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT);
    else
        *pme = make_pme(PM_NOT_PRESENT);
}
#else
static inline void thp_pmd_to_pagemap_entry(pagemap_entry_t *pme,
                        pmd_t pmd, int offset)
{
}
#endif

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;
    pagemap_entry_t pme = make_pme(PM_NOT_PRESENT);

    /* find the first VMA at or above 'addr' */
    vma = find_vma(walk->mm, addr);
    if (vma && pmd_trans_huge_lock(pmd, vma) == 1) {
        for (; addr != end; addr += PAGE_SIZE) {
            unsigned long offset;

            offset = (addr & ~PAGEMAP_WALK_MASK) >>
                    PAGE_SHIFT;
            thp_pmd_to_pagemap_entry(&pme, *pmd, offset);
            err = add_to_pagemap(addr, &pme, pm);
            if (err)
                break;
        }
        spin_unlock(&walk->mm->page_table_lock);
        return err;
    }

    if (pmd_trans_unstable(pmd))
        return 0;
    for (; addr != end; addr += PAGE_SIZE) {

        /* 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);
            pme = make_pme(PM_NOT_PRESENT);
        }

        /* 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);
            pte_to_pagemap_entry(&pme, vma, addr, *pte);
            /* unmap before userspace copy */
            pte_unmap(pte);
        }
        err = add_to_pagemap(addr, &pme, pm);
        if (err)
            return err;
    }

    cond_resched();

    return err;
}

#ifdef CONFIG_HUGETLB_PAGE
static void huge_pte_to_pagemap_entry(pagemap_entry_t *pme,
                    pte_t pte, int offset)
{
    if (pte_present(pte))
        *pme = make_pme(PM_PFRAME(pte_pfn(pte) + offset)
                | PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT);
    else
        *pme = make_pme(PM_NOT_PRESENT);
}

/* 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;
    pagemap_entry_t pme;

    for (; addr != end; addr += PAGE_SIZE) {
        int offset = (addr & ~hmask) >> PAGE_SHIFT;
        huge_pte_to_pagemap_entry(&pme, *pte, offset);
        err = add_to_pagemap(addr, &pme, 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 0-54  page frame number (PFN) if present
 * Bits 0-4   swap type if swapped
 * Bits 5-54  swap offset if swapped
 * Bits 55-60 page shift (page size = 1<<page shift)
 * 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 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 = -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;

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

    mm = mm_access(task, PTRACE_MODE_READ);
    ret = PTR_ERR(mm);
    if (!mm || IS_ERR(mm))
        goto out_free;

    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) & 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_mm;
        }
        copied += len;
        buf += len;
        count -= len;
    }
    *ppos += copied;
    if (!ret || ret == PM_END_OF_BUFFER)
        ret = copied;

out_mm:
    mmput(mm);
out_free:
    kfree(pm.buffer);
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

struct numa_maps {
    struct vm_area_struct *vma;
    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_HIGH_MEMORY]))
        return NULL;

    return page;
}

static int gather_pte_stats(pmd_t *pmd, unsigned long addr,
        unsigned long end, struct mm_walk *walk)
{
    struct numa_maps *md;
    spinlock_t *ptl;
    pte_t *orig_pte;
    pte_t *pte;

    md = walk->private;

    if (pmd_trans_huge_lock(pmd, md->vma) == 1) {
        pte_t huge_pte = *(pte_t *)pmd;
        struct page *page;

        page = can_gather_numa_stats(huge_pte, md->vma, addr);
        if (page)
            gather_stats(page, md, pte_dirty(huge_pte),
                     HPAGE_PMD_SIZE/PAGE_SIZE);
        spin_unlock(&walk->mm->page_table_lock);
        return 0;
    }

    if (pmd_trans_unstable(pmd))
        return 0;
    orig_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
    do {
        struct page *page = can_gather_numa_stats(*pte, md->vma, addr);
        if (!page)
            continue;
        gather_stats(page, md, pte_dirty(*pte), 1);

    } while (pte++, addr += PAGE_SIZE, addr != end);
    pte_unmap_unlock(orig_pte, ptl);
    return 0;
}
#ifdef CONFIG_HUGETLB_PAGE
static int gather_hugetbl_stats(pte_t *pte, unsigned long hmask,
        unsigned long addr, unsigned long end, struct mm_walk *walk)
{
    struct numa_maps *md;
    struct page *page;

    if (pte_none(*pte))
        return 0;

    page = pte_page(*pte);
    if (!page)
        return 0;

    md = walk->private;
    gather_stats(page, md, pte_dirty(*pte), 1);
    return 0;
}

#else
static int gather_hugetbl_stats(pte_t *pte, unsigned long hmask,
        unsigned long addr, unsigned long end, struct mm_walk *walk)
{
    return 0;
}
#endif

/*
 * Display pages allocated per node and memory policy via /proc.
 */
static int show_numa_map(struct seq_file *m, void *v, int is_pid)
{
    struct numa_maps_private *numa_priv = m->private;
    struct proc_maps_private *proc_priv = &numa_priv->proc_maps;
    struct vm_area_struct *vma = v;
    struct numa_maps *md = &numa_priv->md;
    struct file *file = vma->vm_file;
    struct task_struct *task = proc_priv->task;
    struct mm_struct *mm = vma->vm_mm;
    struct mm_walk walk = {};
    struct mempolicy *pol;
    int n;
    char buffer[50];

    if (!mm)
        return 0;

    /* Ensure we start with an empty set of numa_maps statistics. */
    memset(md, 0, sizeof(*md));

    md->vma = vma;

    walk.hugetlb_entry = gather_hugetbl_stats;
    walk.pmd_entry = gather_pte_stats;
    walk.private = md;
    walk.mm = mm;

    pol = get_vma_policy(task, vma, vma->vm_start);
    mpol_to_str(buffer, sizeof(buffer), pol, 0);
    mpol_cond_put(pol);

    seq_printf(m, "%08lx %s", vma->vm_start, buffer);

    if (file) {
        seq_printf(m, " file=");
        seq_path(m, &file->f_path, "\n\t= ");
    } else if (vma->vm_start <= mm->brk && vma->vm_end >= mm->start_brk) {
        seq_printf(m, " heap");
    } else {
        pid_t tid = vm_is_stack(task, vma, is_pid);
        if (tid != 0) {
            /*
             * Thread stack in /proc/PID/task/TID/maps or
             * the main process stack.
             */
            if (!is_pid || (vma->vm_start <= mm->start_stack &&
                vma->vm_end >= mm->start_stack))
                seq_printf(m, " stack");
            else
                seq_printf(m, " stack:%d", tid);
        }
    }

    if (is_vm_hugetlb_page(vma))
        seq_printf(m, " huge");

    walk_page_range(vma->vm_start, vma->vm_end, &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(n, N_HIGH_MEMORY)
        if (md->node[n])
            seq_printf(m, " N%d=%lu", n, md->node[n]);
out:
    seq_putc(m, '\n');

    if (m->count < m->size)
        m->version = (vma != proc_priv->tail_vma) ? vma->vm_start : 0;
    return 0;
}

static int show_pid_numa_map(struct seq_file *m, void *v)
{
    return show_numa_map(m, v, 1);
}

static int show_tid_numa_map(struct seq_file *m, void *v)
{
    return show_numa_map(m, v, 0);
}

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

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

static int numa_maps_open(struct inode *inode, struct file *file,
              const struct seq_operations *ops)
{
    struct numa_maps_private *priv;
    int ret = -ENOMEM;
    priv = kzalloc(sizeof(*priv), GFP_KERNEL);
    if (priv) {
        priv->proc_maps.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 pid_numa_maps_open(struct inode *inode, struct file *file)
{
    return numa_maps_open(inode, file, &proc_pid_numa_maps_op);
}

static int tid_numa_maps_open(struct inode *inode, struct file *file)
{
    return numa_maps_open(inode, file, &proc_tid_numa_maps_op);
}

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

const struct file_operations proc_tid_numa_maps_operations = {
    .open       = tid_numa_maps_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = seq_release_private,
};
#endif /* CONFIG_NUMA */