// SPDX-License-Identifier: GPL-2.0
/*
 *      linux/mm/mlock.c
 *
 *  (C) Copyright 1995 Linus Torvalds
 *  (C) Copyright 2002 Christoph Hellwig
 */

#include <linux/capability.h>
#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/sched/user.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/pagemap.h>
#include <linux/pagevec.h>
#include <linux/pagewalk.h>
#include <linux/mempolicy.h>
#include <linux/syscalls.h>
#include <linux/sched.h>
#include <linux/export.h>
#include <linux/rmap.h>
#include <linux/mmzone.h>
#include <linux/hugetlb.h>
#include <linux/memcontrol.h>
#include <linux/mm_inline.h>
#include <linux/secretmem.h>

#include "internal.h"

struct mlock_pvec {
        local_lock_t lock;
        struct pagevec vec;
};

static DEFINE_PER_CPU(struct mlock_pvec, mlock_pvec) = {
        .lock = INIT_LOCAL_LOCK(lock),
};

bool can_do_mlock(void)
{
        if (rlimit(RLIMIT_MEMLOCK) != 0)
                return true;
        if (capable(CAP_IPC_LOCK))
                return true;
        return false;
}
EXPORT_SYMBOL(can_do_mlock);

/*
 * Mlocked pages are marked with PageMlocked() flag for efficient testing
 * in vmscan and, possibly, the fault path; and to support semi-accurate
 * statistics.
 *
 * An mlocked page [PageMlocked(page)] is unevictable.  As such, it will
 * be placed on the LRU "unevictable" list, rather than the [in]active lists.
 * The unevictable list is an LRU sibling list to the [in]active lists.
 * PageUnevictable is set to indicate the unevictable state.
 */

static struct lruvec *__mlock_page(struct page *page, struct lruvec *lruvec)
{
        /* There is nothing more we can do while it's off LRU */
        if (!TestClearPageLRU(page))
                return lruvec;

        lruvec = folio_lruvec_relock_irq(page_folio(page), lruvec);

        if (unlikely(page_evictable(page))) {
                /*
                 * This is a little surprising, but quite possible:
                 * PageMlocked must have got cleared already by another CPU.
                 * Could this page be on the Unevictable LRU?  I'm not sure,
                 * but move it now if so.
                 */
                if (PageUnevictable(page)) {
                        del_page_from_lru_list(page, lruvec);
                        ClearPageUnevictable(page);
                        add_page_to_lru_list(page, lruvec);
                        __count_vm_events(UNEVICTABLE_PGRESCUED,
                                          thp_nr_pages(page));
                }
                goto out;
        }

        if (PageUnevictable(page)) {
                if (PageMlocked(page))
                        page->mlock_count++;
                goto out;
        }

        del_page_from_lru_list(page, lruvec);
        ClearPageActive(page);
        SetPageUnevictable(page);
        page->mlock_count = !!PageMlocked(page);
        add_page_to_lru_list(page, lruvec);
        __count_vm_events(UNEVICTABLE_PGCULLED, thp_nr_pages(page));
out:
        SetPageLRU(page);
        return lruvec;
}

static struct lruvec *__mlock_new_page(struct page *page, struct lruvec *lruvec)
{
        VM_BUG_ON_PAGE(PageLRU(page), page);

        lruvec = folio_lruvec_relock_irq(page_folio(page), lruvec);

        /* As above, this is a little surprising, but possible */
        if (unlikely(page_evictable(page)))
                goto out;

        SetPageUnevictable(page);
        page->mlock_count = !!PageMlocked(page);
        __count_vm_events(UNEVICTABLE_PGCULLED, thp_nr_pages(page));
out:
        add_page_to_lru_list(page, lruvec);
        SetPageLRU(page);
        return lruvec;
}

static struct lruvec *__munlock_page(struct page *page, struct lruvec *lruvec)
{
        int nr_pages = thp_nr_pages(page);
        bool isolated = false;

        if (!TestClearPageLRU(page))
                goto munlock;

        isolated = true;
        lruvec = folio_lruvec_relock_irq(page_folio(page), lruvec);

        if (PageUnevictable(page)) {
                /* Then mlock_count is maintained, but might undercount */
                if (page->mlock_count)
                        page->mlock_count--;
                if (page->mlock_count)
                        goto out;
        }
        /* else assume that was the last mlock: reclaim will fix it if not */

munlock:
        if (TestClearPageMlocked(page)) {
                __mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
                if (isolated || !PageUnevictable(page))
                        __count_vm_events(UNEVICTABLE_PGMUNLOCKED, nr_pages);
                else
                        __count_vm_events(UNEVICTABLE_PGSTRANDED, nr_pages);
        }

        /* page_evictable() has to be checked *after* clearing Mlocked */
        if (isolated && PageUnevictable(page) && page_evictable(page)) {
                del_page_from_lru_list(page, lruvec);
                ClearPageUnevictable(page);
                add_page_to_lru_list(page, lruvec);
                __count_vm_events(UNEVICTABLE_PGRESCUED, nr_pages);
        }
out:
        if (isolated)
                SetPageLRU(page);
        return lruvec;
}

/*
 * Flags held in the low bits of a struct page pointer on the mlock_pvec.
 */
#define LRU_PAGE 0x1
#define NEW_PAGE 0x2
static inline struct page *mlock_lru(struct page *page)
{
        return (struct page *)((unsigned long)page + LRU_PAGE);
}

static inline struct page *mlock_new(struct page *page)
{
        return (struct page *)((unsigned long)page + NEW_PAGE);
}

/*
 * mlock_pagevec() is derived from pagevec_lru_move_fn():
 * perhaps that can make use of such page pointer flags in future,
 * but for now just keep it for mlock.  We could use three separate
 * pagevecs instead, but one feels better (munlocking a full pagevec
 * does not need to drain mlocking pagevecs first).
 */
static void mlock_pagevec(struct pagevec *pvec)
{
        struct lruvec *lruvec = NULL;
        unsigned long mlock;
        struct page *page;
        int i;

        for (i = 0; i < pagevec_count(pvec); i++) {
                page = pvec->pages[i];
                mlock = (unsigned long)page & (LRU_PAGE | NEW_PAGE);
                page = (struct page *)((unsigned long)page - mlock);
                pvec->pages[i] = page;

                if (mlock & LRU_PAGE)
                        lruvec = __mlock_page(page, lruvec);
                else if (mlock & NEW_PAGE)
                        lruvec = __mlock_new_page(page, lruvec);
                else
                        lruvec = __munlock_page(page, lruvec);
        }

        if (lruvec)
                unlock_page_lruvec_irq(lruvec);
        release_pages(pvec->pages, pvec->nr);
        pagevec_reinit(pvec);
}

void mlock_page_drain_local(void)
{
        struct pagevec *pvec;

        local_lock(&mlock_pvec.lock);
        pvec = this_cpu_ptr(&mlock_pvec.vec);
        if (pagevec_count(pvec))
                mlock_pagevec(pvec);
        local_unlock(&mlock_pvec.lock);
}

void mlock_page_drain_remote(int cpu)
{
        struct pagevec *pvec;

        WARN_ON_ONCE(cpu_online(cpu));
        pvec = &per_cpu(mlock_pvec.vec, cpu);
        if (pagevec_count(pvec))
                mlock_pagevec(pvec);
}

bool need_mlock_page_drain(int cpu)
{
        return pagevec_count(&per_cpu(mlock_pvec.vec, cpu));
}

/**
 * mlock_folio - mlock a folio already on (or temporarily off) LRU
 * @folio: folio to be mlocked.
 */
void mlock_folio(struct folio *folio)
{
        struct pagevec *pvec;

        local_lock(&mlock_pvec.lock);
        pvec = this_cpu_ptr(&mlock_pvec.vec);

        if (!folio_test_set_mlocked(folio)) {
                int nr_pages = folio_nr_pages(folio);

                zone_stat_mod_folio(folio, NR_MLOCK, nr_pages);
                __count_vm_events(UNEVICTABLE_PGMLOCKED, nr_pages);
        }

        folio_get(folio);
        if (!pagevec_add(pvec, mlock_lru(&folio->page)) ||
            folio_test_large(folio) || lru_cache_disabled())
                mlock_pagevec(pvec);
        local_unlock(&mlock_pvec.lock);
}

/**
 * mlock_new_page - mlock a newly allocated page not yet on LRU
 * @page: page to be mlocked, either a normal page or a THP head.
 */
void mlock_new_page(struct page *page)
{
        struct pagevec *pvec;
        int nr_pages = thp_nr_pages(page);

        local_lock(&mlock_pvec.lock);
        pvec = this_cpu_ptr(&mlock_pvec.vec);
        SetPageMlocked(page);
        mod_zone_page_state(page_zone(page), NR_MLOCK, nr_pages);
        __count_vm_events(UNEVICTABLE_PGMLOCKED, nr_pages);

        get_page(page);
        if (!pagevec_add(pvec, mlock_new(page)) ||
            PageHead(page) || lru_cache_disabled())
                mlock_pagevec(pvec);
        local_unlock(&mlock_pvec.lock);
}

/**
 * munlock_page - munlock a page
 * @page: page to be munlocked, either a normal page or a THP head.
 */
void munlock_page(struct page *page)
{
        struct pagevec *pvec;

        local_lock(&mlock_pvec.lock);
        pvec = this_cpu_ptr(&mlock_pvec.vec);
        /*
         * TestClearPageMlocked(page) must be left to __munlock_page(),
         * which will check whether the page is multiply mlocked.
         */

        get_page(page);
        if (!pagevec_add(pvec, page) ||
            PageHead(page) || lru_cache_disabled())
                mlock_pagevec(pvec);
        local_unlock(&mlock_pvec.lock);
}

static int mlock_pte_range(pmd_t *pmd, unsigned long addr,
                           unsigned long end, struct mm_walk *walk)

{
        struct vm_area_struct *vma = walk->vma;
        spinlock_t *ptl;
        pte_t *start_pte, *pte;
        struct page *page;

        ptl = pmd_trans_huge_lock(pmd, vma);
        if (ptl) {
                if (!pmd_present(*pmd))
                        goto out;
                if (is_huge_zero_pmd(*pmd))
                        goto out;
                page = pmd_page(*pmd);
                if (vma->vm_flags & VM_LOCKED)
                        mlock_folio(page_folio(page));
                else
                        munlock_page(page);
                goto out;
        }

        start_pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
        for (pte = start_pte; addr != end; pte++, addr += PAGE_SIZE) {
                if (!pte_present(*pte))
                        continue;
                page = vm_normal_page(vma, addr, *pte);
                if (!page)
                        continue;
                if (PageTransCompound(page))
                        continue;
                if (vma->vm_flags & VM_LOCKED)
                        mlock_folio(page_folio(page));
                else
                        munlock_page(page);
        }
        pte_unmap(start_pte);
out:
        spin_unlock(ptl);
        cond_resched();
        return 0;
}

/*
 * mlock_vma_pages_range() - mlock any pages already in the range,
 *                           or munlock all pages in the range.
 * @vma - vma containing range to be mlock()ed or munlock()ed
 * @start - start address in @vma of the range
 * @end - end of range in @vma
 * @newflags - the new set of flags for @vma.
 *
 * Called for mlock(), mlock2() and mlockall(), to set @vma VM_LOCKED;
 * called for munlock() and munlockall(), to clear VM_LOCKED from @vma.
 */
static void mlock_vma_pages_range(struct vm_area_struct *vma,
        unsigned long start, unsigned long end, vm_flags_t newflags)
{
        static const struct mm_walk_ops mlock_walk_ops = {
                .pmd_entry = mlock_pte_range,
        };

        /*
         * There is a slight chance that concurrent page migration,
         * or page reclaim finding a page of this now-VM_LOCKED vma,
         * will call mlock_vma_page() and raise page's mlock_count:
         * double counting, leaving the page unevictable indefinitely.
         * Communicate this danger to mlock_vma_page() with VM_IO,
         * which is a VM_SPECIAL flag not allowed on VM_LOCKED vmas.
         * mmap_lock is held in write mode here, so this weird
         * combination should not be visible to other mmap_lock users;
         * but WRITE_ONCE so rmap walkers must see VM_IO if VM_LOCKED.
         */
        if (newflags & VM_LOCKED)
                newflags |= VM_IO;
        WRITE_ONCE(vma->vm_flags, newflags);

        lru_add_drain();
        walk_page_range(vma->vm_mm, start, end, &mlock_walk_ops, NULL);
        lru_add_drain();

        if (newflags & VM_IO) {
                newflags &= ~VM_IO;
                WRITE_ONCE(vma->vm_flags, newflags);
        }
}

/*
 * mlock_fixup  - handle mlock[all]/munlock[all] requests.
 *
 * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
 * munlock is a no-op.  However, for some special vmas, we go ahead and
 * populate the ptes.
 *
 * For vmas that pass the filters, merge/split as appropriate.
 */
static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
        unsigned long start, unsigned long end, vm_flags_t newflags)
{
        struct mm_struct *mm = vma->vm_mm;
        pgoff_t pgoff;
        int nr_pages;
        int ret = 0;
        vm_flags_t oldflags = vma->vm_flags;

        if (newflags == oldflags || (oldflags & VM_SPECIAL) ||
            is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm) ||
            vma_is_dax(vma) || vma_is_secretmem(vma))
                /* don't set VM_LOCKED or VM_LOCKONFAULT and don't count */
                goto out;

        pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
        *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
                          vma->vm_file, pgoff, vma_policy(vma),
                          vma->vm_userfaultfd_ctx, anon_vma_name(vma));
        if (*prev) {
                vma = *prev;
                goto success;
        }

        if (start != vma->vm_start) {
                ret = split_vma(mm, vma, start, 1);
                if (ret)
                        goto out;
        }

        if (end != vma->vm_end) {
                ret = split_vma(mm, vma, end, 0);
                if (ret)
                        goto out;
        }

success:
        /*
         * Keep track of amount of locked VM.
         */
        nr_pages = (end - start) >> PAGE_SHIFT;
        if (!(newflags & VM_LOCKED))
                nr_pages = -nr_pages;
        else if (oldflags & VM_LOCKED)
                nr_pages = 0;
        mm->locked_vm += nr_pages;

        /*
         * vm_flags is protected by the mmap_lock held in write mode.
         * It's okay if try_to_unmap_one unmaps a page just after we
         * set VM_LOCKED, populate_vma_page_range will bring it back.
         */

        if ((newflags & VM_LOCKED) && (oldflags & VM_LOCKED)) {
                /* No work to do, and mlocking twice would be wrong */
                vma->vm_flags = newflags;
        } else {
                mlock_vma_pages_range(vma, start, end, newflags);
        }
out:
        *prev = vma;
        return ret;
}

static int apply_vma_lock_flags(unsigned long start, size_t len,
                                vm_flags_t flags)
{
        unsigned long nstart, end, tmp;
        struct vm_area_struct *vma, *prev;
        int error;

        VM_BUG_ON(offset_in_page(start));
        VM_BUG_ON(len != PAGE_ALIGN(len));
        end = start + len;
        if (end < start)
                return -EINVAL;
        if (end == start)
                return 0;
        vma = find_vma(current->mm, start);
        if (!vma || vma->vm_start > start)
                return -ENOMEM;

        prev = vma->vm_prev;
        if (start > vma->vm_start)
                prev = vma;

        for (nstart = start ; ; ) {
                vm_flags_t newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;

                newflags |= flags;

                /* Here we know that  vma->vm_start <= nstart < vma->vm_end. */
                tmp = vma->vm_end;
                if (tmp > end)
                        tmp = end;
                error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
                if (error)
                        break;
                nstart = tmp;
                if (nstart < prev->vm_end)
                        nstart = prev->vm_end;
                if (nstart >= end)
                        break;

                vma = prev->vm_next;
                if (!vma || vma->vm_start != nstart) {
                        error = -ENOMEM;
                        break;
                }
        }
        return error;
}

/*
 * Go through vma areas and sum size of mlocked
 * vma pages, as return value.
 * Note deferred memory locking case(mlock2(,,MLOCK_ONFAULT)
 * is also counted.
 * Return value: previously mlocked page counts
 */
static unsigned long count_mm_mlocked_page_nr(struct mm_struct *mm,
                unsigned long start, size_t len)
{
        struct vm_area_struct *vma;
        unsigned long count = 0;

        if (mm == NULL)
                mm = current->mm;

        vma = find_vma(mm, start);
        if (vma == NULL)
                return 0;

        for (; vma ; vma = vma->vm_next) {
                if (start >= vma->vm_end)
                        continue;
                if (start + len <=  vma->vm_start)
                        break;
                if (vma->vm_flags & VM_LOCKED) {
                        if (start > vma->vm_start)
                                count -= (start - vma->vm_start);
                        if (start + len < vma->vm_end) {
                                count += start + len - vma->vm_start;
                                break;
                        }
                        count += vma->vm_end - vma->vm_start;
                }
        }

        return count >> PAGE_SHIFT;
}

/*
 * convert get_user_pages() return value to posix mlock() error
 */
static int __mlock_posix_error_return(long retval)
{
        if (retval == -EFAULT)
                retval = -ENOMEM;
        else if (retval == -ENOMEM)
                retval = -EAGAIN;
        return retval;
}

static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t flags)
{
        unsigned long locked;
        unsigned long lock_limit;
        int error = -ENOMEM;

        start = untagged_addr(start);

        if (!can_do_mlock())
                return -EPERM;

        len = PAGE_ALIGN(len + (offset_in_page(start)));
        start &= PAGE_MASK;

        lock_limit = rlimit(RLIMIT_MEMLOCK);
        lock_limit >>= PAGE_SHIFT;
        locked = len >> PAGE_SHIFT;

        if (mmap_write_lock_killable(current->mm))
                return -EINTR;

        locked += current->mm->locked_vm;
        if ((locked > lock_limit) && (!capable(CAP_IPC_LOCK))) {
                /*
                 * It is possible that the regions requested intersect with
                 * previously mlocked areas, that part area in "mm->locked_vm"
                 * should not be counted to new mlock increment count. So check
                 * and adjust locked count if necessary.
                 */
                locked -= count_mm_mlocked_page_nr(current->mm,
                                start, len);
        }

        /* check against resource limits */
        if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
                error = apply_vma_lock_flags(start, len, flags);

        mmap_write_unlock(current->mm);
        if (error)
                return error;

        error = __mm_populate(start, len, 0);
        if (error)
                return __mlock_posix_error_return(error);
        return 0;
}

SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
{
        return do_mlock(start, len, VM_LOCKED);
}

SYSCALL_DEFINE3(mlock2, unsigned long, start, size_t, len, int, flags)
{
        vm_flags_t vm_flags = VM_LOCKED;

        if (flags & ~MLOCK_ONFAULT)
                return -EINVAL;

        if (flags & MLOCK_ONFAULT)
                vm_flags |= VM_LOCKONFAULT;

        return do_mlock(start, len, vm_flags);
}

SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
{
        int ret;

        start = untagged_addr(start);

        len = PAGE_ALIGN(len + (offset_in_page(start)));
        start &= PAGE_MASK;

        if (mmap_write_lock_killable(current->mm))
                return -EINTR;
        ret = apply_vma_lock_flags(start, len, 0);
        mmap_write_unlock(current->mm);

        return ret;
}

/*
 * Take the MCL_* flags passed into mlockall (or 0 if called from munlockall)
 * and translate into the appropriate modifications to mm->def_flags and/or the
 * flags for all current VMAs.
 *
 * There are a couple of subtleties with this.  If mlockall() is called multiple
 * times with different flags, the values do not necessarily stack.  If mlockall
 * is called once including the MCL_FUTURE flag and then a second time without
 * it, VM_LOCKED and VM_LOCKONFAULT will be cleared from mm->def_flags.
 */
static int apply_mlockall_flags(int flags)
{
        struct vm_area_struct *vma, *prev = NULL;
        vm_flags_t to_add = 0;

        current->mm->def_flags &= VM_LOCKED_CLEAR_MASK;
        if (flags & MCL_FUTURE) {
                current->mm->def_flags |= VM_LOCKED;

                if (flags & MCL_ONFAULT)
                        current->mm->def_flags |= VM_LOCKONFAULT;

                if (!(flags & MCL_CURRENT))
                        goto out;
        }

        if (flags & MCL_CURRENT) {
                to_add |= VM_LOCKED;
                if (flags & MCL_ONFAULT)
                        to_add |= VM_LOCKONFAULT;
        }

        for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
                vm_flags_t newflags;

                newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
                newflags |= to_add;

                /* Ignore errors */
                mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
                cond_resched();
        }
out:
        return 0;
}

SYSCALL_DEFINE1(mlockall, int, flags)
{
        unsigned long lock_limit;
        int ret;

        if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT)) ||
            flags == MCL_ONFAULT)
                return -EINVAL;

        if (!can_do_mlock())
                return -EPERM;

        lock_limit = rlimit(RLIMIT_MEMLOCK);
        lock_limit >>= PAGE_SHIFT;

        if (mmap_write_lock_killable(current->mm))
                return -EINTR;

        ret = -ENOMEM;
        if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
            capable(CAP_IPC_LOCK))
                ret = apply_mlockall_flags(flags);
        mmap_write_unlock(current->mm);
        if (!ret && (flags & MCL_CURRENT))
                mm_populate(0, TASK_SIZE);

        return ret;
}

SYSCALL_DEFINE0(munlockall)
{
        int ret;

        if (mmap_write_lock_killable(current->mm))
                return -EINTR;
        ret = apply_mlockall_flags(0);
        mmap_write_unlock(current->mm);
        return ret;
}

/*
 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
 * shm segments) get accounted against the user_struct instead.
 */
static DEFINE_SPINLOCK(shmlock_user_lock);

int user_shm_lock(size_t size, struct ucounts *ucounts)
{
        unsigned long lock_limit, locked;
        long memlock;
        int allowed = 0;

        locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
        lock_limit = rlimit(RLIMIT_MEMLOCK);
        if (lock_limit != RLIM_INFINITY)
                lock_limit >>= PAGE_SHIFT;
        spin_lock(&shmlock_user_lock);
        memlock = inc_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, locked);

        if ((memlock == LONG_MAX || memlock > lock_limit) && !capable(CAP_IPC_LOCK)) {
                dec_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, locked);
                goto out;
        }
        if (!get_ucounts(ucounts)) {
                dec_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, locked);
                allowed = 0;
                goto out;
        }
        allowed = 1;
out:
        spin_unlock(&shmlock_user_lock);
        return allowed;
}

void user_shm_unlock(size_t size, struct ucounts *ucounts)
{
        spin_lock(&shmlock_user_lock);
        dec_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, (size + PAGE_SIZE - 1) >> PAGE_SHIFT);
        spin_unlock(&shmlock_user_lock);
        put_ucounts(ucounts);
}