// SPDX-License-Identifier: GPL-2.0
#include <linux/pagewalk.h>
#include <linux/mm_inline.h>
#include <linux/hugetlb.h>
#include <linux/huge_mm.h>
#include <linux/mount.h>
#include <linux/ksm.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/sched/mm.h>
#include <linux/leafops.h>
#include <linux/mmu_notifier.h>
#include <linux/page_idle.h>
#include <linux/shmem_fs.h>
#include <linux/uaccess.h>
#include <linux/pkeys.h>
#include <linux/minmax.h>
#include <linux/overflow.h>
#include <linux/buildid.h>

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

#define SENTINEL_VMA_END        -1
#define SENTINEL_VMA_GATE       -2

#define SEQ_PUT_DEC(str, val) \
                seq_put_decimal_ull_width(m, str, (val) << (PAGE_SHIFT-10), 8)
void task_mem(struct seq_file *m, struct mm_struct *mm)
{
        unsigned long text, lib, swap, anon, file, shmem;
        unsigned long hiwater_vm, total_vm, hiwater_rss, total_rss;

        anon = get_mm_counter_sum(mm, MM_ANONPAGES);
        file = get_mm_counter_sum(mm, MM_FILEPAGES);
        shmem = get_mm_counter_sum(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;

        /* split executable areas between text and lib */
        text = PAGE_ALIGN(mm->end_code) - (mm->start_code & PAGE_MASK);
        text = min(text, mm->exec_vm << PAGE_SHIFT);
        lib = (mm->exec_vm << PAGE_SHIFT) - text;

        swap = get_mm_counter_sum(mm, MM_SWAPENTS);
        SEQ_PUT_DEC("VmPeak:\t", hiwater_vm);
        SEQ_PUT_DEC(" kB\nVmSize:\t", total_vm);
        SEQ_PUT_DEC(" kB\nVmLck:\t", mm->locked_vm);
        SEQ_PUT_DEC(" kB\nVmPin:\t", atomic64_read(&mm->pinned_vm));
        SEQ_PUT_DEC(" kB\nVmHWM:\t", hiwater_rss);
        SEQ_PUT_DEC(" kB\nVmRSS:\t", total_rss);
        SEQ_PUT_DEC(" kB\nRssAnon:\t", anon);
        SEQ_PUT_DEC(" kB\nRssFile:\t", file);
        SEQ_PUT_DEC(" kB\nRssShmem:\t", shmem);
        SEQ_PUT_DEC(" kB\nVmData:\t", mm->data_vm);
        SEQ_PUT_DEC(" kB\nVmStk:\t", mm->stack_vm);
        seq_put_decimal_ull_width(m,
                    " kB\nVmExe:\t", text >> 10, 8);
        seq_put_decimal_ull_width(m,
                    " kB\nVmLib:\t", lib >> 10, 8);
        seq_put_decimal_ull_width(m,
                    " kB\nVmPTE:\t", mm_pgtables_bytes(mm) >> 10, 8);
        SEQ_PUT_DEC(" kB\nVmSwap:\t", swap);
        seq_puts(m, " kB\n");
        hugetlb_report_usage(m, mm);
}
#undef SEQ_PUT_DEC

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_sum(mm, MM_FILEPAGES) +
                        get_mm_counter_sum(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_sum(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

#ifdef CONFIG_PER_VMA_LOCK

static void reset_lock_ctx(struct proc_maps_locking_ctx *lock_ctx)
{
        lock_ctx->locked_vma = NULL;
        lock_ctx->mmap_locked = false;
}

static void unlock_ctx_vma(struct proc_maps_locking_ctx *lock_ctx)
{
        if (lock_ctx->locked_vma) {
                vma_end_read(lock_ctx->locked_vma);
                lock_ctx->locked_vma = NULL;
        }
}

static const struct seq_operations proc_pid_maps_op;

static inline bool lock_vma_range(struct seq_file *m,
                                  struct proc_maps_locking_ctx *lock_ctx)
{
        /*
         * smaps and numa_maps perform page table walk, therefore require
         * mmap_lock but maps can be read with locking just the vma and
         * walking the vma tree under rcu read protection.
         */
        if (m->op != &proc_pid_maps_op) {
                if (mmap_read_lock_killable(lock_ctx->mm))
                        return false;

                lock_ctx->mmap_locked = true;
        } else {
                rcu_read_lock();
                reset_lock_ctx(lock_ctx);
        }

        return true;
}

static inline void unlock_vma_range(struct proc_maps_locking_ctx *lock_ctx)
{
        if (lock_ctx->mmap_locked) {
                mmap_read_unlock(lock_ctx->mm);
        } else {
                unlock_ctx_vma(lock_ctx);
                rcu_read_unlock();
        }
}

static struct vm_area_struct *get_next_vma(struct proc_maps_private *priv,
                                           loff_t last_pos)
{
        struct proc_maps_locking_ctx *lock_ctx = &priv->lock_ctx;
        struct vm_area_struct *vma;

        if (lock_ctx->mmap_locked)
                return vma_next(&priv->iter);

        unlock_ctx_vma(lock_ctx);
        vma = lock_next_vma(lock_ctx->mm, &priv->iter, last_pos);
        if (!IS_ERR_OR_NULL(vma))
                lock_ctx->locked_vma = vma;

        return vma;
}

static inline bool fallback_to_mmap_lock(struct proc_maps_private *priv,
                                         loff_t pos)
{
        struct proc_maps_locking_ctx *lock_ctx = &priv->lock_ctx;

        if (lock_ctx->mmap_locked)
                return false;

        rcu_read_unlock();
        mmap_read_lock(lock_ctx->mm);
        /* Reinitialize the iterator after taking mmap_lock */
        vma_iter_set(&priv->iter, pos);
        lock_ctx->mmap_locked = true;

        return true;
}

#else /* CONFIG_PER_VMA_LOCK */

static inline bool lock_vma_range(struct seq_file *m,
                                  struct proc_maps_locking_ctx *lock_ctx)
{
        return mmap_read_lock_killable(lock_ctx->mm) == 0;
}

static inline void unlock_vma_range(struct proc_maps_locking_ctx *lock_ctx)
{
        mmap_read_unlock(lock_ctx->mm);
}

static struct vm_area_struct *get_next_vma(struct proc_maps_private *priv,
                                           loff_t last_pos)
{
        return vma_next(&priv->iter);
}

static inline bool fallback_to_mmap_lock(struct proc_maps_private *priv,
                                         loff_t pos)
{
        return false;
}

#endif /* CONFIG_PER_VMA_LOCK */

static struct vm_area_struct *proc_get_vma(struct seq_file *m, loff_t *ppos)
{
        struct proc_maps_private *priv = m->private;
        struct vm_area_struct *vma;

retry:
        vma = get_next_vma(priv, *ppos);
        /* EINTR of EAGAIN is possible */
        if (IS_ERR(vma)) {
                if (PTR_ERR(vma) == -EAGAIN && fallback_to_mmap_lock(priv, *ppos))
                        goto retry;

                return vma;
        }

        /* Store previous position to be able to restart if needed */
        priv->last_pos = *ppos;
        if (vma) {
                /*
                 * Track the end of the reported vma to ensure position changes
                 * even if previous vma was merged with the next vma and we
                 * found the extended vma with the same vm_start.
                 */
                *ppos = vma->vm_end;
        } else {
                *ppos = SENTINEL_VMA_GATE;
                vma = get_gate_vma(priv->lock_ctx.mm);
        }

        return vma;
}

static void *m_start(struct seq_file *m, loff_t *ppos)
{
        struct proc_maps_private *priv = m->private;
        struct proc_maps_locking_ctx *lock_ctx;
        loff_t last_addr = *ppos;
        struct mm_struct *mm;

        /* See m_next(). Zero at the start or after lseek. */
        if (last_addr == SENTINEL_VMA_END)
                return NULL;

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

        lock_ctx = &priv->lock_ctx;
        mm = lock_ctx->mm;
        if (!mm || !mmget_not_zero(mm)) {
                put_task_struct(priv->task);
                priv->task = NULL;
                return NULL;
        }

        if (!lock_vma_range(m, lock_ctx)) {
                mmput(mm);
                put_task_struct(priv->task);
                priv->task = NULL;
                return ERR_PTR(-EINTR);
        }

        /*
         * Reset current position if last_addr was set before
         * and it's not a sentinel.
         */
        if (last_addr > 0)
                *ppos = last_addr = priv->last_pos;
        vma_iter_init(&priv->iter, mm, (unsigned long)last_addr);
        hold_task_mempolicy(priv);
        if (last_addr == SENTINEL_VMA_GATE)
                return get_gate_vma(mm);

        return proc_get_vma(m, ppos);
}

static void *m_next(struct seq_file *m, void *v, loff_t *ppos)
{
        if (*ppos == SENTINEL_VMA_GATE) {
                *ppos = SENTINEL_VMA_END;
                return NULL;
        }
        return proc_get_vma(m, ppos);
}

static void m_stop(struct seq_file *m, void *v)
{
        struct proc_maps_private *priv = m->private;
        struct mm_struct *mm = priv->lock_ctx.mm;

        if (!priv->task)
                return;

        release_task_mempolicy(priv);
        unlock_vma_range(&priv->lock_ctx);
        mmput(mm);
        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->lock_ctx.mm = proc_mem_open(inode, PTRACE_MODE_READ);
        if (IS_ERR(priv->lock_ctx.mm)) {
                int err = PTR_ERR(priv->lock_ctx.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->lock_ctx.mm)
                mmdrop(priv->lock_ctx.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));
}

static void get_vma_name(struct vm_area_struct *vma,
                         const struct path **path,
                         const char **name,
                         const char **name_fmt)
{
        struct anon_vma_name *anon_name = vma->vm_mm ? anon_vma_name(vma) : NULL;

        *name = NULL;
        *path = NULL;
        *name_fmt = NULL;

        /*
         * Print the dentry name for named mappings, and a
         * special [heap] marker for the heap:
         */
        if (vma->vm_file) {
                /*
                 * If user named this anon shared memory via
                 * prctl(PR_SET_VMA ..., use the provided name.
                 */
                if (anon_name) {
                        *name_fmt = "[anon_shmem:%s]";
                        *name = anon_name->name;
                } else {
                        *path = file_user_path(vma->vm_file);
                }
                return;
        }

        if (vma->vm_ops && vma->vm_ops->name) {
                *name = vma->vm_ops->name(vma);
                if (*name)
                        return;
        }

        *name = arch_vma_name(vma);
        if (*name)
                return;

        if (!vma->vm_mm) {
                *name = "[vdso]";
                return;
        }

        if (vma_is_initial_heap(vma)) {
                *name = "[heap]";
                return;
        }

        if (vma_is_initial_stack(vma)) {
                *name = "[stack]";
                return;
        }

        if (anon_name) {
                *name_fmt = "[anon:%s]";
                *name = anon_name->name;
                return;
        }
}

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_put_hex_ll(m, NULL, start, 8);
        seq_put_hex_ll(m, "-", end, 8);
        seq_putc(m, ' ');
        seq_putc(m, flags & VM_READ ? 'r' : '-');
        seq_putc(m, flags & VM_WRITE ? 'w' : '-');
        seq_putc(m, flags & VM_EXEC ? 'x' : '-');
        seq_putc(m, flags & VM_MAYSHARE ? 's' : 'p');
        seq_put_hex_ll(m, " ", pgoff, 8);
        seq_put_hex_ll(m, " ", MAJOR(dev), 2);
        seq_put_hex_ll(m, ":", MINOR(dev), 2);
        seq_put_decimal_ull(m, " ", ino);
        seq_putc(m, ' ');
}

static void
show_map_vma(struct seq_file *m, struct vm_area_struct *vma)
{
        const struct path *path;
        const char *name_fmt, *name;
        vm_flags_t flags = vma->vm_flags;
        unsigned long ino = 0;
        unsigned long long pgoff = 0;
        unsigned long start, end;
        dev_t dev = 0;

        if (vma->vm_file) {
                const struct inode *inode = file_user_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;
        show_vma_header_prefix(m, start, end, flags, pgoff, dev, ino);

        get_vma_name(vma, &path, &name, &name_fmt);
        if (path) {
                seq_pad(m, ' ');
                seq_path(m, path, "\n");
        } else if (name_fmt) {
                seq_pad(m, ' ');
                seq_printf(m, name_fmt, name);
        } else 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);
        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);
}

#define PROCMAP_QUERY_VMA_FLAGS (                               \
                PROCMAP_QUERY_VMA_READABLE |                    \
                PROCMAP_QUERY_VMA_WRITABLE |                    \
                PROCMAP_QUERY_VMA_EXECUTABLE |                  \
                PROCMAP_QUERY_VMA_SHARED                        \
)

#define PROCMAP_QUERY_VALID_FLAGS_MASK (                        \
                PROCMAP_QUERY_COVERING_OR_NEXT_VMA |            \
                PROCMAP_QUERY_FILE_BACKED_VMA |                 \
                PROCMAP_QUERY_VMA_FLAGS                         \
)

#ifdef CONFIG_PER_VMA_LOCK

static int query_vma_setup(struct proc_maps_locking_ctx *lock_ctx)
{
        reset_lock_ctx(lock_ctx);

        return 0;
}

static void query_vma_teardown(struct proc_maps_locking_ctx *lock_ctx)
{
        if (lock_ctx->mmap_locked) {
                mmap_read_unlock(lock_ctx->mm);
                lock_ctx->mmap_locked = false;
        } else {
                unlock_ctx_vma(lock_ctx);
        }
}

static struct vm_area_struct *query_vma_find_by_addr(struct proc_maps_locking_ctx *lock_ctx,
                                                     unsigned long addr)
{
        struct mm_struct *mm = lock_ctx->mm;
        struct vm_area_struct *vma;
        struct vma_iterator vmi;

        if (lock_ctx->mmap_locked)
                return find_vma(mm, addr);

        /* Unlock previously locked VMA and find the next one under RCU */
        unlock_ctx_vma(lock_ctx);
        rcu_read_lock();
        vma_iter_init(&vmi, mm, addr);
        vma = lock_next_vma(mm, &vmi, addr);
        rcu_read_unlock();

        if (!vma)
                return NULL;

        if (!IS_ERR(vma)) {
                lock_ctx->locked_vma = vma;
                return vma;
        }

        if (PTR_ERR(vma) == -EAGAIN) {
                /* Fallback to mmap_lock on vma->vm_refcnt overflow */
                mmap_read_lock(mm);
                vma = find_vma(mm, addr);
                lock_ctx->mmap_locked = true;
        }

        return vma;
}

#else /* CONFIG_PER_VMA_LOCK */

static int query_vma_setup(struct proc_maps_locking_ctx *lock_ctx)
{
        return mmap_read_lock_killable(lock_ctx->mm);
}

static void query_vma_teardown(struct proc_maps_locking_ctx *lock_ctx)
{
        mmap_read_unlock(lock_ctx->mm);
}

static struct vm_area_struct *query_vma_find_by_addr(struct proc_maps_locking_ctx *lock_ctx,
                                                     unsigned long addr)
{
        return find_vma(lock_ctx->mm, addr);
}

#endif  /* CONFIG_PER_VMA_LOCK */

static struct vm_area_struct *query_matching_vma(struct proc_maps_locking_ctx *lock_ctx,
                                                 unsigned long addr, u32 flags)
{
        struct vm_area_struct *vma;

next_vma:
        vma = query_vma_find_by_addr(lock_ctx, addr);
        if (IS_ERR(vma))
                return vma;

        if (!vma)
                goto no_vma;

        /* user requested only file-backed VMA, keep iterating */
        if ((flags & PROCMAP_QUERY_FILE_BACKED_VMA) && !vma->vm_file)
                goto skip_vma;

        /* VMA permissions should satisfy query flags */
        if (flags & PROCMAP_QUERY_VMA_FLAGS) {
                u32 perm = 0;

                if (flags & PROCMAP_QUERY_VMA_READABLE)
                        perm |= VM_READ;
                if (flags & PROCMAP_QUERY_VMA_WRITABLE)
                        perm |= VM_WRITE;
                if (flags & PROCMAP_QUERY_VMA_EXECUTABLE)
                        perm |= VM_EXEC;
                if (flags & PROCMAP_QUERY_VMA_SHARED)
                        perm |= VM_MAYSHARE;

                if ((vma->vm_flags & perm) != perm)
                        goto skip_vma;
        }

        /* found covering VMA or user is OK with the matching next VMA */
        if ((flags & PROCMAP_QUERY_COVERING_OR_NEXT_VMA) || vma->vm_start <= addr)
                return vma;

skip_vma:
        /*
         * If the user needs closest matching VMA, keep iterating.
         */
        addr = vma->vm_end;
        if (flags & PROCMAP_QUERY_COVERING_OR_NEXT_VMA)
                goto next_vma;

no_vma:
        return ERR_PTR(-ENOENT);
}

static int do_procmap_query(struct mm_struct *mm, void __user *uarg)
{
        struct proc_maps_locking_ctx lock_ctx = { .mm = mm };
        struct procmap_query karg;
        struct vm_area_struct *vma;
        struct file *vm_file = NULL;
        const char *name = NULL;
        char build_id_buf[BUILD_ID_SIZE_MAX], *name_buf = NULL;
        __u64 usize;
        int err;

        if (copy_from_user(&usize, (void __user *)uarg, sizeof(usize)))
                return -EFAULT;
        /* argument struct can never be that large, reject abuse */
        if (usize > PAGE_SIZE)
                return -E2BIG;
        /* argument struct should have at least query_flags and query_addr fields */
        if (usize < offsetofend(struct procmap_query, query_addr))
                return -EINVAL;
        err = copy_struct_from_user(&karg, sizeof(karg), uarg, usize);
        if (err)
                return err;

        /* reject unknown flags */
        if (karg.query_flags & ~PROCMAP_QUERY_VALID_FLAGS_MASK)
                return -EINVAL;
        /* either both buffer address and size are set, or both should be zero */
        if (!!karg.vma_name_size != !!karg.vma_name_addr)
                return -EINVAL;
        if (!!karg.build_id_size != !!karg.build_id_addr)
                return -EINVAL;

        if (!mm || !mmget_not_zero(mm))
                return -ESRCH;

        err = query_vma_setup(&lock_ctx);
        if (err) {
                mmput(mm);
                return err;
        }

        vma = query_matching_vma(&lock_ctx, karg.query_addr, karg.query_flags);
        if (IS_ERR(vma)) {
                err = PTR_ERR(vma);
                vma = NULL;
                goto out;
        }

        karg.vma_start = vma->vm_start;
        karg.vma_end = vma->vm_end;

        karg.vma_flags = 0;
        if (vma->vm_flags & VM_READ)
                karg.vma_flags |= PROCMAP_QUERY_VMA_READABLE;
        if (vma->vm_flags & VM_WRITE)
                karg.vma_flags |= PROCMAP_QUERY_VMA_WRITABLE;
        if (vma->vm_flags & VM_EXEC)
                karg.vma_flags |= PROCMAP_QUERY_VMA_EXECUTABLE;
        if (vma->vm_flags & VM_MAYSHARE)
                karg.vma_flags |= PROCMAP_QUERY_VMA_SHARED;

        karg.vma_page_size = vma_kernel_pagesize(vma);

        if (vma->vm_file) {
                const struct inode *inode = file_user_inode(vma->vm_file);

                karg.vma_offset = ((__u64)vma->vm_pgoff) << PAGE_SHIFT;
                karg.dev_major = MAJOR(inode->i_sb->s_dev);
                karg.dev_minor = MINOR(inode->i_sb->s_dev);
                karg.inode = inode->i_ino;
        } else {
                karg.vma_offset = 0;
                karg.dev_major = 0;
                karg.dev_minor = 0;
                karg.inode = 0;
        }

        if (karg.vma_name_size) {
                size_t name_buf_sz = min_t(size_t, PATH_MAX, karg.vma_name_size);
                const struct path *path;
                const char *name_fmt;
                size_t name_sz = 0;

                get_vma_name(vma, &path, &name, &name_fmt);

                if (path || name_fmt || name) {
                        name_buf = kmalloc(name_buf_sz, GFP_KERNEL);
                        if (!name_buf) {
                                err = -ENOMEM;
                                goto out;
                        }
                }
                if (path) {
                        name = d_path(path, name_buf, name_buf_sz);
                        if (IS_ERR(name)) {
                                err = PTR_ERR(name);
                                goto out;
                        }
                        name_sz = name_buf + name_buf_sz - name;
                } else if (name || name_fmt) {
                        name_sz = 1 + snprintf(name_buf, name_buf_sz, name_fmt ?: "%s", name);
                        name = name_buf;
                }
                if (name_sz > name_buf_sz) {
                        err = -ENAMETOOLONG;
                        goto out;
                }
                karg.vma_name_size = name_sz;
        }

        if (karg.build_id_size && vma->vm_file)
                vm_file = get_file(vma->vm_file);

        /* unlock vma or mmap_lock, and put mm_struct before copying data to user */
        query_vma_teardown(&lock_ctx);
        mmput(mm);

        if (karg.build_id_size) {
                __u32 build_id_sz;

                if (vm_file)
                        err = build_id_parse_file(vm_file, build_id_buf, &build_id_sz);
                else
                        err = -ENOENT;
                if (err) {
                        karg.build_id_size = 0;
                } else {
                        if (karg.build_id_size < build_id_sz) {
                                err = -ENAMETOOLONG;
                                goto out_file;
                        }
                        karg.build_id_size = build_id_sz;
                }
        }

        if (vm_file)
                fput(vm_file);

        if (karg.vma_name_size && copy_to_user(u64_to_user_ptr(karg.vma_name_addr),
                                               name, karg.vma_name_size)) {
                kfree(name_buf);
                return -EFAULT;
        }
        kfree(name_buf);

        if (karg.build_id_size && copy_to_user(u64_to_user_ptr(karg.build_id_addr),
                                               build_id_buf, karg.build_id_size))
                return -EFAULT;

        if (copy_to_user(uarg, &karg, min_t(size_t, sizeof(karg), usize)))
                return -EFAULT;

        return 0;

out:
        query_vma_teardown(&lock_ctx);
        mmput(mm);
out_file:
        if (vm_file)
                fput(vm_file);
        kfree(name_buf);
        return err;
}

static long procfs_procmap_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        struct seq_file *seq = file->private_data;
        struct proc_maps_private *priv = seq->private;

        switch (cmd) {
        case PROCMAP_QUERY:
                /* priv->lock_ctx.mm is set during file open operation */
                return do_procmap_query(priv->lock_ctx.mm, (void __user *)arg);
        default:
                return -ENOIOCTLCMD;
        }
}

const struct file_operations proc_pid_maps_operations = {
        .open           = pid_maps_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = proc_map_release,
        .unlocked_ioctl = procfs_procmap_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
};

/*
 * 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 file_thp;
        unsigned long swap;
        unsigned long shared_hugetlb;
        unsigned long private_hugetlb;
        unsigned long ksm;
        u64 pss;
        u64 pss_anon;
        u64 pss_file;
        u64 pss_shmem;
        u64 pss_dirty;
        u64 pss_locked;
        u64 swap_pss;
};

static void smaps_page_accumulate(struct mem_size_stats *mss,
                struct folio *folio, unsigned long size, unsigned long pss,
                bool dirty, bool locked, bool private)
{
        mss->pss += pss;

        if (folio_test_anon(folio))
                mss->pss_anon += pss;
        else if (folio_test_swapbacked(folio))
                mss->pss_shmem += pss;
        else
                mss->pss_file += pss;

        if (locked)
                mss->pss_locked += pss;

        if (dirty || folio_test_dirty(folio)) {
                mss->pss_dirty += pss;
                if (private)
                        mss->private_dirty += size;
                else
                        mss->shared_dirty += size;
        } else {
                if (private)
                        mss->private_clean += size;
                else
                        mss->shared_clean += size;
        }
}

static void smaps_account(struct mem_size_stats *mss, struct page *page,
                bool compound, bool young, bool dirty, bool locked,
                bool present)
{
        struct folio *folio = page_folio(page);
        int i, nr = compound ? compound_nr(page) : 1;
        unsigned long size = nr * PAGE_SIZE;
        bool exclusive;
        int mapcount;

        /*
         * First accumulate quantities that depend only on |size| and the type
         * of the compound page.
         */
        if (folio_test_anon(folio)) {
                mss->anonymous += size;
                if (!folio_test_swapbacked(folio) && !dirty &&
                    !folio_test_dirty(folio))
                        mss->lazyfree += size;
        }

        if (folio_test_ksm(folio))
                mss->ksm += size;

        mss->resident += size;
        /* Accumulate the size in pages that have been accessed. */
        if (young || folio_test_young(folio) || folio_test_referenced(folio))
                mss->referenced += size;

        /*
         * Then accumulate quantities that may depend on sharing, or that may
         * differ page-by-page.
         *
         * refcount == 1 for present entries guarantees that the folio is mapped
         * exactly once. For large folios this implies that exactly one
         * PTE/PMD/... maps (a part of) this folio.
         *
         * Treat all non-present entries (where relying on the mapcount and
         * refcount doesn't make sense) as "maybe shared, but not sure how
         * often". We treat device private entries as being fake-present.
         *
         * Note that it would not be safe to read the mapcount especially for
         * pages referenced by migration entries, even with the PTL held.
         */
        if (folio_ref_count(folio) == 1 || !present) {
                smaps_page_accumulate(mss, folio, size, size << PSS_SHIFT,
                                      dirty, locked, present);
                return;
        }

        if (IS_ENABLED(CONFIG_NO_PAGE_MAPCOUNT)) {
                mapcount = folio_average_page_mapcount(folio);
                exclusive = !folio_maybe_mapped_shared(folio);
        }

        /*
         * We obtain a snapshot of the mapcount. Without holding the folio lock
         * this snapshot can be slightly wrong as we cannot always read the
         * mapcount atomically.
         */
        for (i = 0; i < nr; i++, page++) {
                unsigned long pss = PAGE_SIZE << PSS_SHIFT;

                if (IS_ENABLED(CONFIG_PAGE_MAPCOUNT)) {
                        mapcount = folio_precise_page_mapcount(folio, page);
                        exclusive = mapcount < 2;
                }

                if (mapcount >= 2)
                        pss /= mapcount;
                smaps_page_accumulate(mss, folio, PAGE_SIZE, pss,
                                dirty, locked, exclusive);
        }
}

#ifdef CONFIG_SHMEM
static int smaps_pte_hole(unsigned long addr, unsigned long end,
                          __always_unused int depth, struct mm_walk *walk)
{
        struct mem_size_stats *mss = walk->private;
        struct vm_area_struct *vma = walk->vma;

        mss->swap += shmem_partial_swap_usage(walk->vma->vm_file->f_mapping,
                                              linear_page_index(vma, addr),
                                              linear_page_index(vma, end));

        return 0;
}
#else
#define smaps_pte_hole          NULL
#endif /* CONFIG_SHMEM */

static void smaps_pte_hole_lookup(unsigned long addr, struct mm_walk *walk)
{
#ifdef CONFIG_SHMEM
        if (walk->ops->pte_hole) {
                /* depth is not used */
                smaps_pte_hole(addr, addr + PAGE_SIZE, 0, walk);
        }
#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;
        bool present = false, young = false, dirty = false;
        pte_t ptent = ptep_get(pte);

        if (pte_present(ptent)) {
                page = vm_normal_page(vma, addr, ptent);
                young = pte_young(ptent);
                dirty = pte_dirty(ptent);
                present = true;
        } else if (pte_none(ptent)) {
                smaps_pte_hole_lookup(addr, walk);
        } else {
                const softleaf_t entry = softleaf_from_pte(ptent);

                if (softleaf_is_swap(entry)) {
                        int mapcount;

                        mss->swap += PAGE_SIZE;
                        mapcount = swp_swapcount(entry);
                        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 (softleaf_has_pfn(entry)) {
                        if (softleaf_is_device_private(entry))
                                present = true;
                        page = softleaf_to_page(entry);
                }
        }

        if (!page)
                return;

        smaps_account(mss, page, false, young, dirty, locked, present);
}

#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 = NULL;
        bool present = false;
        struct folio *folio;

        if (pmd_none(*pmd))
                return;
        if (pmd_present(*pmd)) {
                page = vm_normal_page_pmd(vma, addr, *pmd);
                present = true;
        } else if (unlikely(thp_migration_supported())) {
                const softleaf_t entry = softleaf_from_pmd(*pmd);

                if (softleaf_has_pfn(entry))
                        page = softleaf_to_page(entry);
        }
        if (IS_ERR_OR_NULL(page))
                return;
        folio = page_folio(page);
        if (folio_test_anon(folio))
                mss->anonymous_thp += HPAGE_PMD_SIZE;
        else if (folio_test_swapbacked(folio))
                mss->shmem_thp += HPAGE_PMD_SIZE;
        else if (folio_is_zone_device(folio))
                /* pass */;
        else
                mss->file_thp += HPAGE_PMD_SIZE;

        smaps_account(mss, page, true, pmd_young(*pmd), pmd_dirty(*pmd),
                      locked, present);
}
#else
static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
                struct mm_walk *walk)
{
}
#endif

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

        ptl = pmd_trans_huge_lock(pmd, vma);
        if (ptl) {
                smaps_pmd_entry(pmd, addr, walk);
                spin_unlock(ptl);
                goto out;
        }

        pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
        if (!pte) {
                walk->action = ACTION_AGAIN;
                return 0;
        }
        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.
         *
         * The length of the second argument of mnemonics[]
         * needs to be 3 instead of previously set 2
         * (i.e. from [BITS_PER_LONG][2] to [BITS_PER_LONG][3])
         * to avoid spurious
         * -Werror=unterminated-string-initialization warning
         *  with GCC 15
         */
        static const char mnemonics[BITS_PER_LONG][3] = {
                /*
                 * 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_MAYBE_GUARD)] = "gu",
                [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_LOCKONFAULT)] = "lf",
                [ilog2(VM_ACCOUNT)]     = "ac",
                [ilog2(VM_NORESERVE)]   = "nr",
                [ilog2(VM_HUGETLB)]     = "ht",
                [ilog2(VM_SYNC)]        = "sf",
                [ilog2(VM_ARCH_1)]      = "ar",
                [ilog2(VM_WIPEONFORK)]  = "wf",
                [ilog2(VM_DONTDUMP)]    = "dd",
#ifdef CONFIG_ARM64_BTI
                [ilog2(VM_ARM64_BTI)]   = "bt",
#endif
#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_ARM64_MTE
                [ilog2(VM_MTE)]         = "mt",
                [ilog2(VM_MTE_ALLOWED)] = "",
#endif
#ifdef CONFIG_ARCH_HAS_PKEYS
                /* These come out via ProtectionKey: */
                [ilog2(VM_PKEY_BIT0)]   = "",
                [ilog2(VM_PKEY_BIT1)]   = "",
                [ilog2(VM_PKEY_BIT2)]   = "",
#if CONFIG_ARCH_PKEY_BITS > 3
                [ilog2(VM_PKEY_BIT3)]   = "",
#endif
#if CONFIG_ARCH_PKEY_BITS > 4
                [ilog2(VM_PKEY_BIT4)]   = "",
#endif
#endif /* CONFIG_ARCH_HAS_PKEYS */
#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
                [ilog2(VM_UFFD_MINOR)]  = "ui",
#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_MINOR */
#ifdef CONFIG_ARCH_HAS_USER_SHADOW_STACK
                [ilog2(VM_SHADOW_STACK)] = "ss",
#endif
#if defined(CONFIG_64BIT) || defined(CONFIG_PPC32)
                [ilog2(VM_DROPPABLE)] = "dp",
#endif
#ifdef CONFIG_64BIT
                [ilog2(VM_SEALED)] = "sl",
#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, "%s ", mnemonics[i]);
        }
        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 folio *folio = NULL;
        bool present = false;
        spinlock_t *ptl;
        pte_t ptent;

        ptl = huge_pte_lock(hstate_vma(vma), walk->mm, pte);
        ptent = huge_ptep_get(walk->mm, addr, pte);
        if (pte_present(ptent)) {
                folio = page_folio(pte_page(ptent));
                present = true;
        } else {
                const softleaf_t entry = softleaf_from_pte(ptent);

                if (softleaf_has_pfn(entry))
                        folio = softleaf_to_folio(entry);
        }

        if (folio) {
                /* We treat non-present entries as "maybe shared". */
                if (!present || folio_maybe_mapped_shared(folio) ||
                    hugetlb_pmd_shared(pte))
                        mss->shared_hugetlb += huge_page_size(hstate_vma(vma));
                else
                        mss->private_hugetlb += huge_page_size(hstate_vma(vma));
        }
        spin_unlock(ptl);
        return 0;
}
#else
#define smaps_hugetlb_range     NULL
#endif /* HUGETLB_PAGE */

static const struct mm_walk_ops smaps_walk_ops = {
        .pmd_entry              = smaps_pte_range,
        .hugetlb_entry          = smaps_hugetlb_range,
        .walk_lock              = PGWALK_RDLOCK,
};

static const struct mm_walk_ops smaps_shmem_walk_ops = {
        .pmd_entry              = smaps_pte_range,
        .hugetlb_entry          = smaps_hugetlb_range,
        .pte_hole               = smaps_pte_hole,
        .walk_lock              = PGWALK_RDLOCK,
};

/*
 * Gather mem stats from @vma with the indicated beginning
 * address @start, and keep them in @mss.
 *
 * Use vm_start of @vma as the beginning address if @start is 0.
 */
static void smap_gather_stats(struct vm_area_struct *vma,
                struct mem_size_stats *mss, unsigned long start)
{
        const struct mm_walk_ops *ops = &smaps_walk_ops;

        /* Invalid start */
        if (start >= vma->vm_end)
                return;

        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 (!start && (!shmem_swapped || (vma->vm_flags & VM_SHARED) ||
                                        !(vma->vm_flags & VM_WRITE))) {
                        mss->swap += shmem_swapped;
                } else {
                        ops = &smaps_shmem_walk_ops;
                }
        }

        /* mmap_lock is held in m_start */
        if (!start)
                walk_page_vma(vma, ops, mss);
        else
                walk_page_range(vma->vm_mm, start, vma->vm_end, ops, mss);
}

#define SEQ_PUT_DEC(str, val) \
                seq_put_decimal_ull_width(m, str, (val) >> 10, 8)

/* Show the contents common for smaps and smaps_rollup */
static void __show_smap(struct seq_file *m, const struct mem_size_stats *mss,
        bool rollup_mode)
{
        SEQ_PUT_DEC("Rss:            ", mss->resident);
        SEQ_PUT_DEC(" kB\nPss:            ", mss->pss >> PSS_SHIFT);
        SEQ_PUT_DEC(" kB\nPss_Dirty:      ", mss->pss_dirty >> PSS_SHIFT);
        if (rollup_mode) {
                /*
                 * These are meaningful only for smaps_rollup, otherwise two of
                 * them are zero, and the other one is the same as Pss.
                 */
                SEQ_PUT_DEC(" kB\nPss_Anon:       ",
                        mss->pss_anon >> PSS_SHIFT);
                SEQ_PUT_DEC(" kB\nPss_File:       ",
                        mss->pss_file >> PSS_SHIFT);
                SEQ_PUT_DEC(" kB\nPss_Shmem:      ",
                        mss->pss_shmem >> PSS_SHIFT);
        }
        SEQ_PUT_DEC(" kB\nShared_Clean:   ", mss->shared_clean);
        SEQ_PUT_DEC(" kB\nShared_Dirty:   ", mss->shared_dirty);
        SEQ_PUT_DEC(" kB\nPrivate_Clean:  ", mss->private_clean);
        SEQ_PUT_DEC(" kB\nPrivate_Dirty:  ", mss->private_dirty);
        SEQ_PUT_DEC(" kB\nReferenced:     ", mss->referenced);
        SEQ_PUT_DEC(" kB\nAnonymous:      ", mss->anonymous);
        SEQ_PUT_DEC(" kB\nKSM:            ", mss->ksm);
        SEQ_PUT_DEC(" kB\nLazyFree:       ", mss->lazyfree);
        SEQ_PUT_DEC(" kB\nAnonHugePages:  ", mss->anonymous_thp);
        SEQ_PUT_DEC(" kB\nShmemPmdMapped: ", mss->shmem_thp);
        SEQ_PUT_DEC(" kB\nFilePmdMapped:  ", mss->file_thp);
        SEQ_PUT_DEC(" kB\nShared_Hugetlb: ", mss->shared_hugetlb);
        seq_put_decimal_ull_width(m, " kB\nPrivate_Hugetlb: ",
                                  mss->private_hugetlb >> 10, 7);
        SEQ_PUT_DEC(" kB\nSwap:           ", mss->swap);
        SEQ_PUT_DEC(" kB\nSwapPss:        ",
                                        mss->swap_pss >> PSS_SHIFT);
        SEQ_PUT_DEC(" kB\nLocked:         ",
                                        mss->pss_locked >> PSS_SHIFT);
        seq_puts(m, " kB\n");
}

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

        smap_gather_stats(vma, &mss, 0);

        show_map_vma(m, vma);

        SEQ_PUT_DEC("Size:           ", vma->vm_end - vma->vm_start);
        SEQ_PUT_DEC(" kB\nKernelPageSize: ", vma_kernel_pagesize(vma));
        SEQ_PUT_DEC(" kB\nMMUPageSize:    ", vma_mmu_pagesize(vma));
        seq_puts(m, " kB\n");

        __show_smap(m, &mss, false);

        seq_printf(m, "THPeligible:    %8u\n",
                   !!thp_vma_allowable_orders(vma, vma->vm_flags, TVA_SMAPS,
                                              THP_ORDERS_ALL));

        if (arch_pkeys_enabled())
                seq_printf(m, "ProtectionKey:  %8u\n", vma_pkey(vma));
        show_smap_vma_flags(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 = priv->lock_ctx.mm;
        struct vm_area_struct *vma;
        unsigned long vma_start = 0, last_vma_end = 0;
        int ret = 0;
        VMA_ITERATOR(vmi, mm, 0);

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

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

        ret = mmap_read_lock_killable(mm);
        if (ret)
                goto out_put_mm;

        hold_task_mempolicy(priv);
        vma = vma_next(&vmi);

        if (unlikely(!vma))
                goto empty_set;

        vma_start = vma->vm_start;
        do {
                smap_gather_stats(vma, &mss, 0);
                last_vma_end = vma->vm_end;

                /*
                 * Release mmap_lock temporarily if someone wants to
                 * access it for write request.
                 */
                if (mmap_lock_is_contended(mm)) {
                        vma_iter_invalidate(&vmi);
                        mmap_read_unlock(mm);
                        ret = mmap_read_lock_killable(mm);
                        if (ret) {
                                release_task_mempolicy(priv);
                                goto out_put_mm;
                        }

                        /*
                         * After dropping the lock, there are four 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:
                         *
                         *    vma_next(vmi) will return VMA3.
                         *    In this case, just continue from VMA3.
                         *
                         * 2) VMA2 still exists:
                         *
                         *    vma_next(vmi) will return VMA3.
                         *    In this case, just continue from VMA3.
                         *
                         * 3) No more VMAs can be found:
                         *
                         *    vma_next(vmi) will return NULL.
                         *    No more things to do, just break.
                         *
                         * 4) (last_vma_end - 1) is the middle of a vma (VMA'):
                         *
                         *    vma_next(vmi) will return VMA' whose range
                         *    contains last_vma_end.
                         *    Iterate VMA' from last_vma_end.
                         */
                        vma = vma_next(&vmi);
                        /* Case 3 above */
                        if (!vma)
                                break;

                        /* Case 1 and 2 above */
                        if (vma->vm_start >= last_vma_end) {
                                smap_gather_stats(vma, &mss, 0);
                                last_vma_end = vma->vm_end;
                                continue;
                        }

                        /* Case 4 above */
                        if (vma->vm_end > last_vma_end) {
                                smap_gather_stats(vma, &mss, last_vma_end);
                                last_vma_end = vma->vm_end;
                        }
                }
        } for_each_vma(vmi, vma);

empty_set:
        show_vma_header_prefix(m, vma_start, last_vma_end, 0, 0, 0, 0);
        seq_pad(m, ' ');
        seq_puts(m, "[rollup]\n");

        __show_smap(m, &mss, true);

        release_task_mempolicy(priv);
        mmap_read_unlock(mm);

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

        return ret;
}
#undef SEQ_PUT_DEC

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_obj(*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->lock_ctx.mm = proc_mem_open(inode, PTRACE_MODE_READ);
        if (IS_ERR_OR_NULL(priv->lock_ctx.mm)) {
                ret = priv->lock_ctx.mm ? PTR_ERR(priv->lock_ctx.mm) : -ESRCH;

                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->lock_ctx.mm)
                mmdrop(priv->lock_ctx.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;
};

static inline bool pte_is_pinned(struct vm_area_struct *vma, unsigned long addr, pte_t pte)
{
        struct folio *folio;

        if (!pte_write(pte))
                return false;
        if (!is_cow_mapping(vma->vm_flags))
                return false;
        if (likely(!mm_flags_test(MMF_HAS_PINNED, vma->vm_mm)))
                return false;
        folio = vm_normal_folio(vma, addr, pte);
        if (!folio)
                return false;
        return folio_maybe_dma_pinned(folio);
}

static inline void clear_soft_dirty(struct vm_area_struct *vma,
                unsigned long addr, pte_t *pte)
{
        if (!pgtable_supports_soft_dirty())
                return;
        /*
         * The soft-dirty tracker uses #PF-s to catch writes
         * to pages, so write-protect the pte as well. See the
         * Documentation/admin-guide/mm/soft-dirty.rst for full description
         * of how soft-dirty works.
         */
        pte_t ptent = ptep_get(pte);

        if (pte_none(ptent))
                return;

        if (pte_present(ptent)) {
                pte_t old_pte;

                if (pte_is_pinned(vma, addr, ptent))
                        return;
                old_pte = ptep_modify_prot_start(vma, addr, pte);
                ptent = pte_wrprotect(old_pte);
                ptent = pte_clear_soft_dirty(ptent);
                ptep_modify_prot_commit(vma, addr, pte, old_pte, ptent);
        } else {
                ptent = pte_swp_clear_soft_dirty(ptent);
                set_pte_at(vma->vm_mm, addr, pte, ptent);
        }
}

#if defined(CONFIG_TRANSPARENT_HUGEPAGE)
static inline void clear_soft_dirty_pmd(struct vm_area_struct *vma,
                unsigned long addr, pmd_t *pmdp)
{
        pmd_t old, pmd = *pmdp;

        if (!pgtable_supports_soft_dirty())
                return;

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

        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;

                folio = pmd_folio(*pmd);

                /* Clear accessed and referenced bits. */
                pmdp_test_and_clear_young(vma, addr, pmd);
                folio_test_clear_young(folio);
                folio_clear_referenced(folio);
out:
                spin_unlock(ptl);
                return 0;
        }

        pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
        if (!pte) {
                walk->action = ACTION_AGAIN;
                return 0;
        }
        for (; addr != end; pte++, addr += PAGE_SIZE) {
                ptent = ptep_get(pte);

                if (cp->type == CLEAR_REFS_SOFT_DIRTY) {
                        clear_soft_dirty(vma, addr, pte);
                        continue;
                }

                if (!pte_present(ptent))
                        continue;

                folio = vm_normal_folio(vma, addr, ptent);
                if (!folio)
                        continue;

                /* Clear accessed and referenced bits. */
                ptep_test_and_clear_young(vma, addr, pte);
                folio_test_clear_young(folio);
                folio_clear_referenced(folio);
        }
        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 const struct mm_walk_ops clear_refs_walk_ops = {
        .pmd_entry              = clear_refs_pte_range,
        .test_walk              = clear_refs_test_walk,
        .walk_lock              = PGWALK_WRLOCK,
};

static ssize_t clear_refs_write(struct file *file, const char __user *buf,
                                size_t count, loff_t *ppos)
{
        struct task_struct *task;
        char buffer[PROC_NUMBUF] = {};
        struct mm_struct *mm;
        struct vm_area_struct *vma;
        enum clear_refs_types type;
        int itype;
        int rv;

        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) {
                VMA_ITERATOR(vmi, mm, 0);
                struct mmu_notifier_range range;
                struct clear_refs_private cp = {
                        .type = type,
                };

                if (mmap_write_lock_killable(mm)) {
                        count = -EINTR;
                        goto out_mm;
                }
                if (type == CLEAR_REFS_MM_HIWATER_RSS) {
                        /*
                         * 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);
                        goto out_unlock;
                }

                if (type == CLEAR_REFS_SOFT_DIRTY) {
                        for_each_vma(vmi, vma) {
                                if (!(vma->vm_flags & VM_SOFTDIRTY))
                                        continue;
                                vm_flags_clear(vma, VM_SOFTDIRTY);
                                vma_set_page_prot(vma);
                        }

                        inc_tlb_flush_pending(mm);
                        mmu_notifier_range_init(&range, MMU_NOTIFY_SOFT_DIRTY,
                                                0, mm, 0, -1UL);
                        mmu_notifier_invalidate_range_start(&range);
                }
                walk_page_range(mm, 0, -1, &clear_refs_walk_ops, &cp);
                if (type == CLEAR_REFS_SOFT_DIRTY) {
                        mmu_notifier_invalidate_range_end(&range);
                        flush_tlb_mm(mm);
                        dec_tlb_flush_pending(mm);
                }
out_unlock:
                mmap_write_unlock(mm);
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_UFFD_WP              BIT_ULL(57)
#define PM_GUARD_REGION         BIT_ULL(58)
#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(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 bool __folio_page_mapped_exclusively(struct folio *folio, struct page *page)
{
        if (IS_ENABLED(CONFIG_PAGE_MAPCOUNT))
                return folio_precise_page_mapcount(folio, page) == 1;
        return !folio_maybe_mapped_shared(folio);
}

static int pagemap_pte_hole(unsigned long start, unsigned long end,
                            __always_unused int depth, 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(&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(&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;
        struct folio *folio;

        if (pte_none(pte))
                goto out;

        if (pte_present(pte)) {
                if (pm->show_pfn)
                        frame = pte_pfn(pte);
                flags |= PM_PRESENT;
                page = vm_normal_page(vma, addr, pte);
                if (pte_soft_dirty(pte))
                        flags |= PM_SOFT_DIRTY;
                if (pte_uffd_wp(pte))
                        flags |= PM_UFFD_WP;
        } else {
                softleaf_t entry;

                if (pte_swp_soft_dirty(pte))
                        flags |= PM_SOFT_DIRTY;
                if (pte_swp_uffd_wp(pte))
                        flags |= PM_UFFD_WP;
                entry = softleaf_from_pte(pte);
                if (pm->show_pfn) {
                        pgoff_t offset;

                        /*
                         * For PFN swap offsets, keeping the offset field
                         * to be PFN only to be compatible with old smaps.
                         */
                        if (softleaf_has_pfn(entry))
                                offset = softleaf_to_pfn(entry);
                        else
                                offset = swp_offset(entry);
                        frame = swp_type(entry) |
                            (offset << MAX_SWAPFILES_SHIFT);
                }
                flags |= PM_SWAP;
                if (softleaf_has_pfn(entry))
                        page = softleaf_to_page(entry);
                if (softleaf_is_uffd_wp_marker(entry))
                        flags |= PM_UFFD_WP;
                if (softleaf_is_guard_marker(entry))
                        flags |=  PM_GUARD_REGION;
        }

        if (page) {
                folio = page_folio(page);
                if (!folio_test_anon(folio))
                        flags |= PM_FILE;
                if ((flags & PM_PRESENT) &&
                    __folio_page_mapped_exclusively(folio, page))
                        flags |= PM_MMAP_EXCLUSIVE;
        }

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

        return make_pme(frame, flags);
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
static int pagemap_pmd_range_thp(pmd_t *pmdp, unsigned long addr,
                unsigned long end, struct vm_area_struct *vma,
                struct pagemapread *pm)
{
        unsigned int idx = (addr & ~PMD_MASK) >> PAGE_SHIFT;
        u64 flags = 0, frame = 0;
        pmd_t pmd = *pmdp;
        struct page *page = NULL;
        struct folio *folio = NULL;
        int err = 0;

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

        if (pmd_none(pmd))
                goto populate_pagemap;

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

                flags |= PM_PRESENT;
                if (pmd_soft_dirty(pmd))
                        flags |= PM_SOFT_DIRTY;
                if (pmd_uffd_wp(pmd))
                        flags |= PM_UFFD_WP;
                if (pm->show_pfn)
                        frame = pmd_pfn(pmd) + idx;
        } else if (thp_migration_supported()) {
                const softleaf_t entry = softleaf_from_pmd(pmd);
                unsigned long offset;

                if (pm->show_pfn) {
                        if (softleaf_has_pfn(entry))
                                offset = softleaf_to_pfn(entry) + idx;
                        else
                                offset = swp_offset(entry) + idx;
                        frame = swp_type(entry) |
                                (offset << MAX_SWAPFILES_SHIFT);
                }
                flags |= PM_SWAP;
                if (pmd_swp_soft_dirty(pmd))
                        flags |= PM_SOFT_DIRTY;
                if (pmd_swp_uffd_wp(pmd))
                        flags |= PM_UFFD_WP;
                VM_WARN_ON_ONCE(!pmd_is_migration_entry(pmd));
                page = softleaf_to_page(entry);
        }

        if (page) {
                folio = page_folio(page);
                if (!folio_test_anon(folio))
                        flags |= PM_FILE;
        }

populate_pagemap:
        for (; addr != end; addr += PAGE_SIZE, idx++) {
                u64 cur_flags = flags;
                pagemap_entry_t pme;

                if (folio && (flags & PM_PRESENT) &&
                    __folio_page_mapped_exclusively(folio, page))
                        cur_flags |= PM_MMAP_EXCLUSIVE;

                pme = make_pme(frame, cur_flags);
                err = add_to_pagemap(&pme, pm);
                if (err)
                        break;
                if (pm->show_pfn) {
                        if (flags & PM_PRESENT)
                                frame++;
                        else if (flags & PM_SWAP)
                                frame += (1 << MAX_SWAPFILES_SHIFT);
                }
        }
        return err;
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

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) {
                err = pagemap_pmd_range_thp(pmdp, addr, end, vma, pm);
                spin_unlock(ptl);
                return err;
        }
#endif

        /*
         * 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);
        if (!pte) {
                walk->action = ACTION_AGAIN;
                return err;
        }
        for (; addr < end; pte++, addr += PAGE_SIZE) {
                pagemap_entry_t pme;

                pme = pte_to_pagemap_entry(pm, vma, addr, ptep_get(pte));
                err = add_to_pagemap(&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;
        spinlock_t *ptl;
        int err = 0;
        pte_t pte;

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

        ptl = huge_pte_lock(hstate_vma(vma), walk->mm, ptep);
        pte = huge_ptep_get(walk->mm, addr, ptep);
        if (pte_present(pte)) {
                struct folio *folio = page_folio(pte_page(pte));

                if (!folio_test_anon(folio))
                        flags |= PM_FILE;

                if (!folio_maybe_mapped_shared(folio) &&
                    !hugetlb_pmd_shared(ptep))
                        flags |= PM_MMAP_EXCLUSIVE;

                if (huge_pte_uffd_wp(pte))
                        flags |= PM_UFFD_WP;

                flags |= PM_PRESENT;
                if (pm->show_pfn)
                        frame = pte_pfn(pte) +
                                ((addr & ~hmask) >> PAGE_SHIFT);
        } else if (pte_swp_uffd_wp_any(pte)) {
                flags |= PM_UFFD_WP;
        }

        for (; addr != end; addr += PAGE_SIZE) {
                pagemap_entry_t pme = make_pme(frame, flags);

                err = add_to_pagemap(&pme, pm);
                if (err)
                        break;
                if (pm->show_pfn && (flags & PM_PRESENT))
                        frame++;
        }

        spin_unlock(ptl);
        cond_resched();

        return err;
}
#else
#define pagemap_hugetlb_range   NULL
#endif /* HUGETLB_PAGE */

static const struct mm_walk_ops pagemap_ops = {
        .pmd_entry      = pagemap_pmd_range,
        .pte_hole       = pagemap_pte_hole,
        .hugetlb_entry  = pagemap_hugetlb_range,
        .walk_lock      = PGWALK_RDLOCK,
};

/*
 * /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/admin-guide/mm/soft-dirty.rst)
 * Bit  56    page exclusively mapped
 * Bit  57    pte is uffd-wp write-protected
 * Bit  58    pte is a guard region
 * Bits 59-60 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;
        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_array(pm.len, PM_ENTRY_BYTES, GFP_KERNEL);
        ret = -ENOMEM;
        if (!pm.buffer)
                goto out_mm;

        src = *ppos;
        svpfn = src / PM_ENTRY_BYTES;
        end_vaddr = mm->task_size;

        /* watch out for wraparound */
        start_vaddr = end_vaddr;
        if (svpfn <= (ULONG_MAX >> PAGE_SHIFT)) {
                unsigned long end;

                ret = mmap_read_lock_killable(mm);
                if (ret)
                        goto out_free;
                start_vaddr = untagged_addr_remote(mm, svpfn << PAGE_SHIFT);
                mmap_read_unlock(mm);

                end = start_vaddr + ((count / PM_ENTRY_BYTES) << PAGE_SHIFT);
                if (end >= start_vaddr && end < mm->task_size)
                        end_vaddr = end;
        }

        /* Ensure the address is inside the task */
        if (start_vaddr > mm->task_size)
                start_vaddr = end_vaddr;

        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;
                ret = mmap_read_lock_killable(mm);
                if (ret)
                        goto out_free;
                ret = walk_page_range(mm, start_vaddr, end, &pagemap_ops, &pm);
                mmap_read_unlock(mm);
                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_OR_NULL(mm))
                return mm ? PTR_ERR(mm) : -ESRCH;
        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;
}

#define PM_SCAN_CATEGORIES      (PAGE_IS_WPALLOWED | PAGE_IS_WRITTEN |  \
                                 PAGE_IS_FILE | PAGE_IS_PRESENT |       \
                                 PAGE_IS_SWAPPED | PAGE_IS_PFNZERO |    \
                                 PAGE_IS_HUGE | PAGE_IS_SOFT_DIRTY |    \
                                 PAGE_IS_GUARD)
#define PM_SCAN_FLAGS           (PM_SCAN_WP_MATCHING | PM_SCAN_CHECK_WPASYNC)

struct pagemap_scan_private {
        struct pm_scan_arg arg;
        unsigned long masks_of_interest, cur_vma_category;
        struct page_region *vec_buf;
        unsigned long vec_buf_len, vec_buf_index, found_pages;
        struct page_region __user *vec_out;
};

static unsigned long pagemap_page_category(struct pagemap_scan_private *p,
                                           struct vm_area_struct *vma,
                                           unsigned long addr, pte_t pte)
{
        unsigned long categories;

        if (pte_none(pte))
                return 0;

        if (pte_present(pte)) {
                struct page *page;

                categories = PAGE_IS_PRESENT;

                if (!pte_uffd_wp(pte))
                        categories |= PAGE_IS_WRITTEN;

                if (p->masks_of_interest & PAGE_IS_FILE) {
                        page = vm_normal_page(vma, addr, pte);
                        if (page && !PageAnon(page))
                                categories |= PAGE_IS_FILE;
                }

                if (is_zero_pfn(pte_pfn(pte)))
                        categories |= PAGE_IS_PFNZERO;
                if (pte_soft_dirty(pte))
                        categories |= PAGE_IS_SOFT_DIRTY;
        } else {
                softleaf_t entry;

                categories = PAGE_IS_SWAPPED;

                if (!pte_swp_uffd_wp_any(pte))
                        categories |= PAGE_IS_WRITTEN;

                entry = softleaf_from_pte(pte);
                if (softleaf_is_guard_marker(entry))
                        categories |= PAGE_IS_GUARD;
                else if ((p->masks_of_interest & PAGE_IS_FILE) &&
                         softleaf_has_pfn(entry) &&
                         !folio_test_anon(softleaf_to_folio(entry)))
                        categories |= PAGE_IS_FILE;

                if (pte_swp_soft_dirty(pte))
                        categories |= PAGE_IS_SOFT_DIRTY;
        }

        return categories;
}

static void make_uffd_wp_pte(struct vm_area_struct *vma,
                             unsigned long addr, pte_t *pte, pte_t ptent)
{
        if (pte_present(ptent)) {
                pte_t old_pte;

                old_pte = ptep_modify_prot_start(vma, addr, pte);
                ptent = pte_mkuffd_wp(old_pte);
                ptep_modify_prot_commit(vma, addr, pte, old_pte, ptent);
        } else if (pte_none(ptent)) {
                set_pte_at(vma->vm_mm, addr, pte,
                           make_pte_marker(PTE_MARKER_UFFD_WP));
        } else {
                ptent = pte_swp_mkuffd_wp(ptent);
                set_pte_at(vma->vm_mm, addr, pte, ptent);
        }
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
static unsigned long pagemap_thp_category(struct pagemap_scan_private *p,
                                          struct vm_area_struct *vma,
                                          unsigned long addr, pmd_t pmd)
{
        unsigned long categories = PAGE_IS_HUGE;

        if (pmd_none(pmd))
                return categories;

        if (pmd_present(pmd)) {
                struct page *page;

                categories |= PAGE_IS_PRESENT;
                if (!pmd_uffd_wp(pmd))
                        categories |= PAGE_IS_WRITTEN;

                if (p->masks_of_interest & PAGE_IS_FILE) {
                        page = vm_normal_page_pmd(vma, addr, pmd);
                        if (page && !PageAnon(page))
                                categories |= PAGE_IS_FILE;
                }

                if (is_huge_zero_pmd(pmd))
                        categories |= PAGE_IS_PFNZERO;
                if (pmd_soft_dirty(pmd))
                        categories |= PAGE_IS_SOFT_DIRTY;
        } else {
                categories |= PAGE_IS_SWAPPED;
                if (!pmd_swp_uffd_wp(pmd))
                        categories |= PAGE_IS_WRITTEN;
                if (pmd_swp_soft_dirty(pmd))
                        categories |= PAGE_IS_SOFT_DIRTY;

                if (p->masks_of_interest & PAGE_IS_FILE) {
                        const softleaf_t entry = softleaf_from_pmd(pmd);

                        if (softleaf_has_pfn(entry) &&
                            !folio_test_anon(softleaf_to_folio(entry)))
                                categories |= PAGE_IS_FILE;
                }
        }

        return categories;
}

static void make_uffd_wp_pmd(struct vm_area_struct *vma,
                             unsigned long addr, pmd_t *pmdp)
{
        pmd_t old, pmd = *pmdp;

        if (pmd_present(pmd)) {
                old = pmdp_invalidate_ad(vma, addr, pmdp);
                pmd = pmd_mkuffd_wp(old);
                set_pmd_at(vma->vm_mm, addr, pmdp, pmd);
        } else if (pmd_is_migration_entry(pmd)) {
                pmd = pmd_swp_mkuffd_wp(pmd);
                set_pmd_at(vma->vm_mm, addr, pmdp, pmd);
        }
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

#ifdef CONFIG_HUGETLB_PAGE
static unsigned long pagemap_hugetlb_category(pte_t pte)
{
        unsigned long categories = PAGE_IS_HUGE;

        if (pte_none(pte))
                return categories;

        /*
         * According to pagemap_hugetlb_range(), file-backed HugeTLB
         * page cannot be swapped. So PAGE_IS_FILE is not checked for
         * swapped pages.
         */
        if (pte_present(pte)) {
                categories |= PAGE_IS_PRESENT;

                if (!huge_pte_uffd_wp(pte))
                        categories |= PAGE_IS_WRITTEN;
                if (!PageAnon(pte_page(pte)))
                        categories |= PAGE_IS_FILE;
                if (is_zero_pfn(pte_pfn(pte)))
                        categories |= PAGE_IS_PFNZERO;
                if (pte_soft_dirty(pte))
                        categories |= PAGE_IS_SOFT_DIRTY;
        } else {
                categories |= PAGE_IS_SWAPPED;

                if (!pte_swp_uffd_wp_any(pte))
                        categories |= PAGE_IS_WRITTEN;
                if (pte_swp_soft_dirty(pte))
                        categories |= PAGE_IS_SOFT_DIRTY;
        }

        return categories;
}

static void make_uffd_wp_huge_pte(struct vm_area_struct *vma,
                                  unsigned long addr, pte_t *ptep,
                                  pte_t ptent)
{
        const unsigned long psize = huge_page_size(hstate_vma(vma));
        softleaf_t entry;

        if (huge_pte_none(ptent)) {
                set_huge_pte_at(vma->vm_mm, addr, ptep,
                                make_pte_marker(PTE_MARKER_UFFD_WP), psize);
                return;
        }

        entry = softleaf_from_pte(ptent);
        if (softleaf_is_hwpoison(entry) || softleaf_is_marker(entry))
                return;

        if (softleaf_is_migration(entry))
                set_huge_pte_at(vma->vm_mm, addr, ptep,
                                pte_swp_mkuffd_wp(ptent), psize);
        else
                huge_ptep_modify_prot_commit(vma, addr, ptep, ptent,
                                             huge_pte_mkuffd_wp(ptent));
}
#endif /* CONFIG_HUGETLB_PAGE */

#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLB_PAGE)
static void pagemap_scan_backout_range(struct pagemap_scan_private *p,
                                       unsigned long addr, unsigned long end)
{
        struct page_region *cur_buf = &p->vec_buf[p->vec_buf_index];

        if (!p->vec_buf)
                return;

        if (cur_buf->start != addr)
                cur_buf->end = addr;
        else
                cur_buf->start = cur_buf->end = 0;

        p->found_pages -= (end - addr) / PAGE_SIZE;
}
#endif

static bool pagemap_scan_is_interesting_page(unsigned long categories,
                                             const struct pagemap_scan_private *p)
{
        categories ^= p->arg.category_inverted;
        if ((categories & p->arg.category_mask) != p->arg.category_mask)
                return false;
        if (p->arg.category_anyof_mask && !(categories & p->arg.category_anyof_mask))
                return false;

        return true;
}

static bool pagemap_scan_is_interesting_vma(unsigned long categories,
                                            const struct pagemap_scan_private *p)
{
        unsigned long required = p->arg.category_mask & PAGE_IS_WPALLOWED;

        categories ^= p->arg.category_inverted;
        if ((categories & required) != required)
                return false;

        return true;
}

static int pagemap_scan_test_walk(unsigned long start, unsigned long end,
                                  struct mm_walk *walk)
{
        struct pagemap_scan_private *p = walk->private;
        struct vm_area_struct *vma = walk->vma;
        unsigned long vma_category = 0;
        bool wp_allowed = userfaultfd_wp_async(vma) &&
            userfaultfd_wp_use_markers(vma);

        if (!wp_allowed) {
                /* User requested explicit failure over wp-async capability */
                if (p->arg.flags & PM_SCAN_CHECK_WPASYNC)
                        return -EPERM;
                /*
                 * User requires wr-protect, and allows silently skipping
                 * unsupported vmas.
                 */
                if (p->arg.flags & PM_SCAN_WP_MATCHING)
                        return 1;
                /*
                 * Then the request doesn't involve wr-protects at all,
                 * fall through to the rest checks, and allow vma walk.
                 */
        }

        if (vma->vm_flags & VM_PFNMAP)
                return 1;

        if (wp_allowed)
                vma_category |= PAGE_IS_WPALLOWED;

        if (vma->vm_flags & VM_SOFTDIRTY)
                vma_category |= PAGE_IS_SOFT_DIRTY;

        if (!pagemap_scan_is_interesting_vma(vma_category, p))
                return 1;

        p->cur_vma_category = vma_category;

        return 0;
}

static bool pagemap_scan_push_range(unsigned long categories,
                                    struct pagemap_scan_private *p,
                                    unsigned long addr, unsigned long end)
{
        struct page_region *cur_buf = &p->vec_buf[p->vec_buf_index];

        /*
         * When there is no output buffer provided at all, the sentinel values
         * won't match here. There is no other way for `cur_buf->end` to be
         * non-zero other than it being non-empty.
         */
        if (addr == cur_buf->end && categories == cur_buf->categories) {
                cur_buf->end = end;
                return true;
        }

        if (cur_buf->end) {
                if (p->vec_buf_index >= p->vec_buf_len - 1)
                        return false;

                cur_buf = &p->vec_buf[++p->vec_buf_index];
        }

        cur_buf->start = addr;
        cur_buf->end = end;
        cur_buf->categories = categories;

        return true;
}

static int pagemap_scan_output(unsigned long categories,
                               struct pagemap_scan_private *p,
                               unsigned long addr, unsigned long *end)
{
        unsigned long n_pages, total_pages;
        int ret = 0;

        if (!p->vec_buf)
                return 0;

        categories &= p->arg.return_mask;

        n_pages = (*end - addr) / PAGE_SIZE;
        if (check_add_overflow(p->found_pages, n_pages, &total_pages) ||
            total_pages > p->arg.max_pages) {
                size_t n_too_much = total_pages - p->arg.max_pages;
                *end -= n_too_much * PAGE_SIZE;
                n_pages -= n_too_much;
                ret = -ENOSPC;
        }

        if (!pagemap_scan_push_range(categories, p, addr, *end)) {
                *end = addr;
                n_pages = 0;
                ret = -ENOSPC;
        }

        p->found_pages += n_pages;
        if (ret)
                p->arg.walk_end = *end;

        return ret;
}

static int pagemap_scan_thp_entry(pmd_t *pmd, unsigned long start,
                                  unsigned long end, struct mm_walk *walk)
{
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
        struct pagemap_scan_private *p = walk->private;
        struct vm_area_struct *vma = walk->vma;
        unsigned long categories;
        spinlock_t *ptl;
        int ret = 0;

        ptl = pmd_trans_huge_lock(pmd, vma);
        if (!ptl)
                return -ENOENT;

        categories = p->cur_vma_category |
                     pagemap_thp_category(p, vma, start, *pmd);

        if (!pagemap_scan_is_interesting_page(categories, p))
                goto out_unlock;

        ret = pagemap_scan_output(categories, p, start, &end);
        if (start == end)
                goto out_unlock;

        if (~p->arg.flags & PM_SCAN_WP_MATCHING)
                goto out_unlock;
        if (~categories & PAGE_IS_WRITTEN)
                goto out_unlock;

        /*
         * Break huge page into small pages if the WP operation
         * needs to be performed on a portion of the huge page.
         */
        if (end != start + HPAGE_SIZE) {
                spin_unlock(ptl);
                split_huge_pmd(vma, pmd, start);
                pagemap_scan_backout_range(p, start, end);
                /* Report as if there was no THP */
                return -ENOENT;
        }

        make_uffd_wp_pmd(vma, start, pmd);
        flush_tlb_range(vma, start, end);
out_unlock:
        spin_unlock(ptl);
        return ret;
#else /* !CONFIG_TRANSPARENT_HUGEPAGE */
        return -ENOENT;
#endif
}

static int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start,
                                  unsigned long end, struct mm_walk *walk)
{
        struct pagemap_scan_private *p = walk->private;
        struct vm_area_struct *vma = walk->vma;
        unsigned long addr, flush_end = 0;
        pte_t *pte, *start_pte;
        spinlock_t *ptl;
        int ret;

        ret = pagemap_scan_thp_entry(pmd, start, end, walk);
        if (ret != -ENOENT)
                return ret;

        ret = 0;
        start_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl);
        if (!pte) {
                walk->action = ACTION_AGAIN;
                return 0;
        }

        lazy_mmu_mode_enable();

        if ((p->arg.flags & PM_SCAN_WP_MATCHING) && !p->vec_out) {
                /* Fast path for performing exclusive WP */
                for (addr = start; addr != end; pte++, addr += PAGE_SIZE) {
                        pte_t ptent = ptep_get(pte);

                        if ((pte_present(ptent) && pte_uffd_wp(ptent)) ||
                            pte_swp_uffd_wp_any(ptent))
                                continue;
                        make_uffd_wp_pte(vma, addr, pte, ptent);
                        if (!flush_end)
                                start = addr;
                        flush_end = addr + PAGE_SIZE;
                }
                goto flush_and_return;
        }

        if (!p->arg.category_anyof_mask && !p->arg.category_inverted &&
            p->arg.category_mask == PAGE_IS_WRITTEN &&
            p->arg.return_mask == PAGE_IS_WRITTEN) {
                for (addr = start; addr < end; pte++, addr += PAGE_SIZE) {
                        unsigned long next = addr + PAGE_SIZE;
                        pte_t ptent = ptep_get(pte);

                        if ((pte_present(ptent) && pte_uffd_wp(ptent)) ||
                            pte_swp_uffd_wp_any(ptent))
                                continue;
                        ret = pagemap_scan_output(p->cur_vma_category | PAGE_IS_WRITTEN,
                                                  p, addr, &next);
                        if (next == addr)
                                break;
                        if (~p->arg.flags & PM_SCAN_WP_MATCHING)
                                continue;
                        make_uffd_wp_pte(vma, addr, pte, ptent);
                        if (!flush_end)
                                start = addr;
                        flush_end = next;
                }
                goto flush_and_return;
        }

        for (addr = start; addr != end; pte++, addr += PAGE_SIZE) {
                pte_t ptent = ptep_get(pte);
                unsigned long categories = p->cur_vma_category |
                                           pagemap_page_category(p, vma, addr, ptent);
                unsigned long next = addr + PAGE_SIZE;

                if (!pagemap_scan_is_interesting_page(categories, p))
                        continue;

                ret = pagemap_scan_output(categories, p, addr, &next);
                if (next == addr)
                        break;

                if (~p->arg.flags & PM_SCAN_WP_MATCHING)
                        continue;
                if (~categories & PAGE_IS_WRITTEN)
                        continue;

                make_uffd_wp_pte(vma, addr, pte, ptent);
                if (!flush_end)
                        start = addr;
                flush_end = next;
        }

flush_and_return:
        if (flush_end)
                flush_tlb_range(vma, start, addr);

        lazy_mmu_mode_disable();
        pte_unmap_unlock(start_pte, ptl);

        cond_resched();
        return ret;
}

#ifdef CONFIG_HUGETLB_PAGE
static int pagemap_scan_hugetlb_entry(pte_t *ptep, unsigned long hmask,
                                      unsigned long start, unsigned long end,
                                      struct mm_walk *walk)
{
        struct pagemap_scan_private *p = walk->private;
        struct vm_area_struct *vma = walk->vma;
        unsigned long categories;
        spinlock_t *ptl;
        int ret = 0;
        pte_t pte;

        if (~p->arg.flags & PM_SCAN_WP_MATCHING) {
                /* Go the short route when not write-protecting pages. */

                pte = huge_ptep_get(walk->mm, start, ptep);
                categories = p->cur_vma_category | pagemap_hugetlb_category(pte);

                if (!pagemap_scan_is_interesting_page(categories, p))
                        return 0;

                return pagemap_scan_output(categories, p, start, &end);
        }

        i_mmap_lock_write(vma->vm_file->f_mapping);
        ptl = huge_pte_lock(hstate_vma(vma), vma->vm_mm, ptep);

        pte = huge_ptep_get(walk->mm, start, ptep);
        categories = p->cur_vma_category | pagemap_hugetlb_category(pte);

        if (!pagemap_scan_is_interesting_page(categories, p))
                goto out_unlock;

        ret = pagemap_scan_output(categories, p, start, &end);
        if (start == end)
                goto out_unlock;

        if (~categories & PAGE_IS_WRITTEN)
                goto out_unlock;

        if (end != start + HPAGE_SIZE) {
                /* Partial HugeTLB page WP isn't possible. */
                pagemap_scan_backout_range(p, start, end);
                p->arg.walk_end = start;
                ret = 0;
                goto out_unlock;
        }

        make_uffd_wp_huge_pte(vma, start, ptep, pte);
        flush_hugetlb_tlb_range(vma, start, end);

out_unlock:
        spin_unlock(ptl);
        i_mmap_unlock_write(vma->vm_file->f_mapping);

        return ret;
}
#else
#define pagemap_scan_hugetlb_entry NULL
#endif

static int pagemap_scan_pte_hole(unsigned long addr, unsigned long end,
                                 int depth, struct mm_walk *walk)
{
        struct pagemap_scan_private *p = walk->private;
        struct vm_area_struct *vma = walk->vma;
        int ret, err;

        if (!vma || !pagemap_scan_is_interesting_page(p->cur_vma_category, p))
                return 0;

        ret = pagemap_scan_output(p->cur_vma_category, p, addr, &end);
        if (addr == end)
                return ret;

        if (~p->arg.flags & PM_SCAN_WP_MATCHING)
                return ret;

        err = uffd_wp_range(vma, addr, end - addr, true);
        if (err < 0)
                ret = err;

        return ret;
}

static const struct mm_walk_ops pagemap_scan_ops = {
        .test_walk = pagemap_scan_test_walk,
        .pmd_entry = pagemap_scan_pmd_entry,
        .pte_hole = pagemap_scan_pte_hole,
        .hugetlb_entry = pagemap_scan_hugetlb_entry,
};

static int pagemap_scan_get_args(struct pm_scan_arg *arg,
                                 unsigned long uarg)
{
        if (copy_from_user(arg, (void __user *)uarg, sizeof(*arg)))
                return -EFAULT;

        if (arg->size != sizeof(struct pm_scan_arg))
                return -EINVAL;

        /* Validate requested features */
        if (arg->flags & ~PM_SCAN_FLAGS)
                return -EINVAL;
        if ((arg->category_inverted | arg->category_mask |
             arg->category_anyof_mask | arg->return_mask) & ~PM_SCAN_CATEGORIES)
                return -EINVAL;

        arg->start = untagged_addr((unsigned long)arg->start);
        arg->end = untagged_addr((unsigned long)arg->end);
        arg->vec = untagged_addr((unsigned long)arg->vec);

        /* Validate memory pointers */
        if (!IS_ALIGNED(arg->start, PAGE_SIZE))
                return -EINVAL;
        if (!access_ok((void __user *)(long)arg->start, arg->end - arg->start))
                return -EFAULT;
        if (!arg->vec && arg->vec_len)
                return -EINVAL;
        if (UINT_MAX == SIZE_MAX && arg->vec_len > SIZE_MAX)
                return -EINVAL;
        if (arg->vec && !access_ok((void __user *)(long)arg->vec,
                                   size_mul(arg->vec_len, sizeof(struct page_region))))
                return -EFAULT;

        /* Fixup default values */
        arg->end = ALIGN(arg->end, PAGE_SIZE);
        arg->walk_end = 0;
        if (!arg->max_pages)
                arg->max_pages = ULONG_MAX;

        return 0;
}

static int pagemap_scan_writeback_args(struct pm_scan_arg *arg,
                                       unsigned long uargl)
{
        struct pm_scan_arg __user *uarg = (void __user *)uargl;

        if (copy_to_user(&uarg->walk_end, &arg->walk_end, sizeof(arg->walk_end)))
                return -EFAULT;

        return 0;
}

static int pagemap_scan_init_bounce_buffer(struct pagemap_scan_private *p)
{
        if (!p->arg.vec_len)
                return 0;

        p->vec_buf_len = min_t(size_t, PAGEMAP_WALK_SIZE >> PAGE_SHIFT,
                               p->arg.vec_len);
        p->vec_buf = kmalloc_objs(*p->vec_buf, p->vec_buf_len);
        if (!p->vec_buf)
                return -ENOMEM;

        p->vec_buf->start = p->vec_buf->end = 0;
        p->vec_out = (struct page_region __user *)(long)p->arg.vec;

        return 0;
}

static long pagemap_scan_flush_buffer(struct pagemap_scan_private *p)
{
        const struct page_region *buf = p->vec_buf;
        long n = p->vec_buf_index;

        if (!p->vec_buf)
                return 0;

        if (buf[n].end != buf[n].start)
                n++;

        if (!n)
                return 0;

        if (copy_to_user(p->vec_out, buf, n * sizeof(*buf)))
                return -EFAULT;

        p->arg.vec_len -= n;
        p->vec_out += n;

        p->vec_buf_index = 0;
        p->vec_buf_len = min_t(size_t, p->vec_buf_len, p->arg.vec_len);
        p->vec_buf->start = p->vec_buf->end = 0;

        return n;
}

static long do_pagemap_scan(struct mm_struct *mm, unsigned long uarg)
{
        struct pagemap_scan_private p = {0};
        unsigned long walk_start;
        size_t n_ranges_out = 0;
        int ret;

        ret = pagemap_scan_get_args(&p.arg, uarg);
        if (ret)
                return ret;

        p.masks_of_interest = p.arg.category_mask | p.arg.category_anyof_mask |
                              p.arg.return_mask;
        ret = pagemap_scan_init_bounce_buffer(&p);
        if (ret)
                return ret;

        for (walk_start = p.arg.start; walk_start < p.arg.end;
                        walk_start = p.arg.walk_end) {
                struct mmu_notifier_range range;
                long n_out;

                if (fatal_signal_pending(current)) {
                        ret = -EINTR;
                        break;
                }

                ret = mmap_read_lock_killable(mm);
                if (ret)
                        break;

                /* Protection change for the range is going to happen. */
                if (p.arg.flags & PM_SCAN_WP_MATCHING) {
                        mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0,
                                                mm, walk_start, p.arg.end);
                        mmu_notifier_invalidate_range_start(&range);
                }

                ret = walk_page_range(mm, walk_start, p.arg.end,
                                      &pagemap_scan_ops, &p);

                if (p.arg.flags & PM_SCAN_WP_MATCHING)
                        mmu_notifier_invalidate_range_end(&range);

                mmap_read_unlock(mm);

                n_out = pagemap_scan_flush_buffer(&p);
                if (n_out < 0)
                        ret = n_out;
                else
                        n_ranges_out += n_out;

                if (ret != -ENOSPC)
                        break;

                if (p.arg.vec_len == 0 || p.found_pages == p.arg.max_pages)
                        break;
        }

        /* ENOSPC signifies early stop (buffer full) from the walk. */
        if (!ret || ret == -ENOSPC)
                ret = n_ranges_out;

        /* The walk_end isn't set when ret is zero */
        if (!p.arg.walk_end)
                p.arg.walk_end = p.arg.end;
        if (pagemap_scan_writeback_args(&p.arg, uarg))
                ret = -EFAULT;

        kfree(p.vec_buf);
        return ret;
}

static long do_pagemap_cmd(struct file *file, unsigned int cmd,
                           unsigned long arg)
{
        struct mm_struct *mm = file->private_data;

        switch (cmd) {
        case PAGEMAP_SCAN:
                return do_pagemap_scan(mm, arg);

        default:
                return -EINVAL;
        }
}

const struct file_operations proc_pagemap_operations = {
        .llseek         = mem_lseek, /* borrow this */
        .read           = pagemap_read,
        .open           = pagemap_open,
        .release        = pagemap_release,
        .unlocked_ioctl = do_pagemap_cmd,
        .compat_ioctl   = do_pagemap_cmd,
};
#endif /* CONFIG_PROC_PAGE_MONITOR */

#ifdef CONFIG_NUMA

struct numa_maps {
        unsigned long pages;
        unsigned long anon;
        unsigned long active;
        unsigned long writeback;
        unsigned long mapcount_max;
        unsigned long dirty;
        unsigned long swapcache;
        unsigned long node[MAX_NUMNODES];
};

struct numa_maps_private {
        struct proc_maps_private proc_maps;
        struct numa_maps md;
};

static void gather_stats(struct page *page, struct numa_maps *md, int pte_dirty,
                        unsigned long nr_pages)
{
        struct folio *folio = page_folio(page);
        int count;

        if (IS_ENABLED(CONFIG_PAGE_MAPCOUNT))
                count = folio_precise_page_mapcount(folio, page);
        else
                count = folio_average_page_mapcount(folio);

        md->pages += nr_pages;
        if (pte_dirty || folio_test_dirty(folio))
                md->dirty += nr_pages;

        if (folio_test_swapcache(folio))
                md->swapcache += nr_pages;

        if (folio_test_active(folio) || folio_test_unevictable(folio))
                md->active += nr_pages;

        if (folio_test_writeback(folio))
                md->writeback += nr_pages;

        if (folio_test_anon(folio))
                md->anon += nr_pages;

        if (count > md->mapcount_max)
                md->mapcount_max = count;

        md->node[folio_nid(folio)] += 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 || is_zone_device_page(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;
        }
#endif
        orig_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
        if (!pte) {
                walk->action = ACTION_AGAIN;
                return 0;
        }
        do {
                pte_t ptent = ptep_get(pte);
                struct page *page = can_gather_numa_stats(ptent, vma, addr);
                if (!page)
                        continue;
                gather_stats(page, md, pte_dirty(ptent), 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;
        struct numa_maps *md;
        struct page *page;
        spinlock_t *ptl;

        ptl = huge_pte_lock(hstate_vma(walk->vma), walk->mm, pte);
        huge_pte = huge_ptep_get(walk->mm, addr, pte);
        if (!pte_present(huge_pte))
                goto out;

        page = pte_page(huge_pte);

        md = walk->private;
        gather_stats(page, md, pte_dirty(huge_pte), 1);
out:
        spin_unlock(ptl);
        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

static const struct mm_walk_ops show_numa_ops = {
        .hugetlb_entry = gather_hugetlb_stats,
        .pmd_entry = gather_pte_stats,
        .walk_lock = PGWALK_RDLOCK,
};

/*
 * 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;
        char buffer[64];
        struct mempolicy *pol;
        pgoff_t ilx;
        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, &ilx);
        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_path(m, file_user_path(file), "\n\t= ");
        } else if (vma_is_initial_heap(vma)) {
                seq_puts(m, " heap");
        } else if (vma_is_initial_stack(vma)) {
                seq_puts(m, " stack");
        }

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

        /* mmap_lock is held by m_start */
        walk_page_vma(vma, &show_numa_ops, md);

        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');
        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 */