Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 3901 insertions, 0 deletions

diff --git a/mm/mmap.c b/mm/mmap.c
new file mode 100644
index 000000000..c0f957549
--- /dev/null
+++ b/mm/mmap.c
@@ -0,0 +1,3901 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * mm/mmap.c
+ *
+ * Written by obz.
+ *
+ * Address space accounting code	<alan@lxorguk.ukuu.org.uk>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/backing-dev.h>
+#include <linux/mm.h>
+#include <linux/mm_inline.h>
+#include <linux/shm.h>
+#include <linux/mman.h>
+#include <linux/pagemap.h>
+#include <linux/swap.h>
+#include <linux/syscalls.h>
+#include <linux/capability.h>
+#include <linux/init.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/personality.h>
+#include <linux/security.h>
+#include <linux/hugetlb.h>
+#include <linux/shmem_fs.h>
+#include <linux/profile.h>
+#include <linux/export.h>
+#include <linux/mount.h>
+#include <linux/mempolicy.h>
+#include <linux/rmap.h>
+#include <linux/mmu_notifier.h>
+#include <linux/mmdebug.h>
+#include <linux/perf_event.h>
+#include <linux/audit.h>
+#include <linux/khugepaged.h>
+#include <linux/uprobes.h>
+#include <linux/notifier.h>
+#include <linux/memory.h>
+#include <linux/printk.h>
+#include <linux/userfaultfd_k.h>
+#include <linux/moduleparam.h>
+#include <linux/pkeys.h>
+#include <linux/oom.h>
+#include <linux/sched/mm.h>
+
+#include <linux/uaccess.h>
+#include <asm/cacheflush.h>
+#include <asm/tlb.h>
+#include <asm/mmu_context.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/mmap.h>
+
+#include "internal.h"
+
+#ifndef arch_mmap_check
+#define arch_mmap_check(addr, len, flags)	(0)
+#endif
+
+#ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS
+const int mmap_rnd_bits_min = CONFIG_ARCH_MMAP_RND_BITS_MIN;
+const int mmap_rnd_bits_max = CONFIG_ARCH_MMAP_RND_BITS_MAX;
+int mmap_rnd_bits __read_mostly = CONFIG_ARCH_MMAP_RND_BITS;
+#endif
+#ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
+const int mmap_rnd_compat_bits_min = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MIN;
+const int mmap_rnd_compat_bits_max = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MAX;
+int mmap_rnd_compat_bits __read_mostly = CONFIG_ARCH_MMAP_RND_COMPAT_BITS;
+#endif
+
+static bool ignore_rlimit_data;
+core_param(ignore_rlimit_data, ignore_rlimit_data, bool, 0644);
+
+static void unmap_region(struct mm_struct *mm, struct maple_tree *mt,
+		struct vm_area_struct *vma, struct vm_area_struct *prev,
+		struct vm_area_struct *next, unsigned long start,
+		unsigned long end);
+
+static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags)
+{
+	return pgprot_modify(oldprot, vm_get_page_prot(vm_flags));
+}
+
+/* Update vma->vm_page_prot to reflect vma->vm_flags. */
+void vma_set_page_prot(struct vm_area_struct *vma)
+{
+	unsigned long vm_flags = vma->vm_flags;
+	pgprot_t vm_page_prot;
+
+	vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, vm_flags);
+	if (vma_wants_writenotify(vma, vm_page_prot)) {
+		vm_flags &= ~VM_SHARED;
+		vm_page_prot = vm_pgprot_modify(vm_page_prot, vm_flags);
+	}
+	/* remove_protection_ptes reads vma->vm_page_prot without mmap_lock */
+	WRITE_ONCE(vma->vm_page_prot, vm_page_prot);
+}
+
+/*
+ * Requires inode->i_mapping->i_mmap_rwsem
+ */
+static void __remove_shared_vm_struct(struct vm_area_struct *vma,
+		struct file *file, struct address_space *mapping)
+{
+	if (vma->vm_flags & VM_SHARED)
+		mapping_unmap_writable(mapping);
+
+	flush_dcache_mmap_lock(mapping);
+	vma_interval_tree_remove(vma, &mapping->i_mmap);
+	flush_dcache_mmap_unlock(mapping);
+}
+
+/*
+ * Unlink a file-based vm structure from its interval tree, to hide
+ * vma from rmap and vmtruncate before freeing its page tables.
+ */
+void unlink_file_vma(struct vm_area_struct *vma)
+{
+	struct file *file = vma->vm_file;
+
+	if (file) {
+		struct address_space *mapping = file->f_mapping;
+		i_mmap_lock_write(mapping);
+		__remove_shared_vm_struct(vma, file, mapping);
+		i_mmap_unlock_write(mapping);
+	}
+}
+
+/*
+ * Close a vm structure and free it.
+ */
+static void remove_vma(struct vm_area_struct *vma)
+{
+	might_sleep();
+	if (vma->vm_ops && vma->vm_ops->close)
+		vma->vm_ops->close(vma);
+	if (vma->vm_file)
+		fput(vma->vm_file);
+	mpol_put(vma_policy(vma));
+	vm_area_free(vma);
+}
+
+/*
+ * check_brk_limits() - Use platform specific check of range & verify mlock
+ * limits.
+ * @addr: The address to check
+ * @len: The size of increase.
+ *
+ * Return: 0 on success.
+ */
+static int check_brk_limits(unsigned long addr, unsigned long len)
+{
+	unsigned long mapped_addr;
+
+	mapped_addr = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
+	if (IS_ERR_VALUE(mapped_addr))
+		return mapped_addr;
+
+	return mlock_future_check(current->mm, current->mm->def_flags, len);
+}
+static int do_brk_munmap(struct ma_state *mas, struct vm_area_struct *vma,
+			 unsigned long newbrk, unsigned long oldbrk,
+			 struct list_head *uf);
+static int do_brk_flags(struct ma_state *mas, struct vm_area_struct *brkvma,
+		unsigned long addr, unsigned long request, unsigned long flags);
+SYSCALL_DEFINE1(brk, unsigned long, brk)
+{
+	unsigned long newbrk, oldbrk, origbrk;
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *brkvma, *next = NULL;
+	unsigned long min_brk;
+	bool populate;
+	bool downgraded = false;
+	LIST_HEAD(uf);
+	MA_STATE(mas, &mm->mm_mt, 0, 0);
+
+	if (mmap_write_lock_killable(mm))
+		return -EINTR;
+
+	origbrk = mm->brk;
+
+#ifdef CONFIG_COMPAT_BRK
+	/*
+	 * CONFIG_COMPAT_BRK can still be overridden by setting
+	 * randomize_va_space to 2, which will still cause mm->start_brk
+	 * to be arbitrarily shifted
+	 */
+	if (current->brk_randomized)
+		min_brk = mm->start_brk;
+	else
+		min_brk = mm->end_data;
+#else
+	min_brk = mm->start_brk;
+#endif
+	if (brk < min_brk)
+		goto out;
+
+	/*
+	 * Check against rlimit here. If this check is done later after the test
+	 * of oldbrk with newbrk then it can escape the test and let the data
+	 * segment grow beyond its set limit the in case where the limit is
+	 * not page aligned -Ram Gupta
+	 */
+	if (check_data_rlimit(rlimit(RLIMIT_DATA), brk, mm->start_brk,
+			      mm->end_data, mm->start_data))
+		goto out;
+
+	newbrk = PAGE_ALIGN(brk);
+	oldbrk = PAGE_ALIGN(mm->brk);
+	if (oldbrk == newbrk) {
+		mm->brk = brk;
+		goto success;
+	}
+
+	/*
+	 * Always allow shrinking brk.
+	 * do_brk_munmap() may downgrade mmap_lock to read.
+	 */
+	if (brk <= mm->brk) {
+		int ret;
+
+		/* Search one past newbrk */
+		mas_set(&mas, newbrk);
+		brkvma = mas_find(&mas, oldbrk);
+		if (!brkvma || brkvma->vm_start >= oldbrk)
+			goto out; /* mapping intersects with an existing non-brk vma. */
+		/*
+		 * mm->brk must be protected by write mmap_lock.
+		 * do_brk_munmap() may downgrade the lock,  so update it
+		 * before calling do_brk_munmap().
+		 */
+		mm->brk = brk;
+		ret = do_brk_munmap(&mas, brkvma, newbrk, oldbrk, &uf);
+		if (ret == 1)  {
+			downgraded = true;
+			goto success;
+		} else if (!ret)
+			goto success;
+
+		mm->brk = origbrk;
+		goto out;
+	}
+
+	if (check_brk_limits(oldbrk, newbrk - oldbrk))
+		goto out;
+
+	/*
+	 * Only check if the next VMA is within the stack_guard_gap of the
+	 * expansion area
+	 */
+	mas_set(&mas, oldbrk);
+	next = mas_find(&mas, newbrk - 1 + PAGE_SIZE + stack_guard_gap);
+	if (next && newbrk + PAGE_SIZE > vm_start_gap(next))
+		goto out;
+
+	brkvma = mas_prev(&mas, mm->start_brk);
+	/* Ok, looks good - let it rip. */
+	if (do_brk_flags(&mas, brkvma, oldbrk, newbrk - oldbrk, 0) < 0)
+		goto out;
+
+	mm->brk = brk;
+
+success:
+	populate = newbrk > oldbrk && (mm->def_flags & VM_LOCKED) != 0;
+	if (downgraded)
+		mmap_read_unlock(mm);
+	else
+		mmap_write_unlock(mm);
+	userfaultfd_unmap_complete(mm, &uf);
+	if (populate)
+		mm_populate(oldbrk, newbrk - oldbrk);
+	return brk;
+
+out:
+	mmap_write_unlock(mm);
+	return origbrk;
+}
+
+#if defined(CONFIG_DEBUG_VM_MAPLE_TREE)
+extern void mt_validate(struct maple_tree *mt);
+extern void mt_dump(const struct maple_tree *mt);
+
+/* Validate the maple tree */
+static void validate_mm_mt(struct mm_struct *mm)
+{
+	struct maple_tree *mt = &mm->mm_mt;
+	struct vm_area_struct *vma_mt;
+
+	MA_STATE(mas, mt, 0, 0);
+
+	mt_validate(&mm->mm_mt);
+	mas_for_each(&mas, vma_mt, ULONG_MAX) {
+		if ((vma_mt->vm_start != mas.index) ||
+		    (vma_mt->vm_end - 1 != mas.last)) {
+			pr_emerg("issue in %s\n", current->comm);
+			dump_stack();
+			dump_vma(vma_mt);
+			pr_emerg("mt piv: %p %lu - %lu\n", vma_mt,
+				 mas.index, mas.last);
+			pr_emerg("mt vma: %p %lu - %lu\n", vma_mt,
+				 vma_mt->vm_start, vma_mt->vm_end);
+
+			mt_dump(mas.tree);
+			if (vma_mt->vm_end != mas.last + 1) {
+				pr_err("vma: %p vma_mt %lu-%lu\tmt %lu-%lu\n",
+						mm, vma_mt->vm_start, vma_mt->vm_end,
+						mas.index, mas.last);
+				mt_dump(mas.tree);
+			}
+			VM_BUG_ON_MM(vma_mt->vm_end != mas.last + 1, mm);
+			if (vma_mt->vm_start != mas.index) {
+				pr_err("vma: %p vma_mt %p %lu - %lu doesn't match\n",
+						mm, vma_mt, vma_mt->vm_start, vma_mt->vm_end);
+				mt_dump(mas.tree);
+			}
+			VM_BUG_ON_MM(vma_mt->vm_start != mas.index, mm);
+		}
+	}
+}
+
+static void validate_mm(struct mm_struct *mm)
+{
+	int bug = 0;
+	int i = 0;
+	struct vm_area_struct *vma;
+	MA_STATE(mas, &mm->mm_mt, 0, 0);
+
+	validate_mm_mt(mm);
+
+	mas_for_each(&mas, vma, ULONG_MAX) {
+#ifdef CONFIG_DEBUG_VM_RB
+		struct anon_vma *anon_vma = vma->anon_vma;
+		struct anon_vma_chain *avc;
+
+		if (anon_vma) {
+			anon_vma_lock_read(anon_vma);
+			list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
+				anon_vma_interval_tree_verify(avc);
+			anon_vma_unlock_read(anon_vma);
+		}
+#endif
+		i++;
+	}
+	if (i != mm->map_count) {
+		pr_emerg("map_count %d mas_for_each %d\n", mm->map_count, i);
+		bug = 1;
+	}
+	VM_BUG_ON_MM(bug, mm);
+}
+
+#else /* !CONFIG_DEBUG_VM_MAPLE_TREE */
+#define validate_mm_mt(root) do { } while (0)
+#define validate_mm(mm) do { } while (0)
+#endif /* CONFIG_DEBUG_VM_MAPLE_TREE */
+
+/*
+ * vma has some anon_vma assigned, and is already inserted on that
+ * anon_vma's interval trees.
+ *
+ * Before updating the vma's vm_start / vm_end / vm_pgoff fields, the
+ * vma must be removed from the anon_vma's interval trees using
+ * anon_vma_interval_tree_pre_update_vma().
+ *
+ * After the update, the vma will be reinserted using
+ * anon_vma_interval_tree_post_update_vma().
+ *
+ * The entire update must be protected by exclusive mmap_lock and by
+ * the root anon_vma's mutex.
+ */
+static inline void
+anon_vma_interval_tree_pre_update_vma(struct vm_area_struct *vma)
+{
+	struct anon_vma_chain *avc;
+
+	list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
+		anon_vma_interval_tree_remove(avc, &avc->anon_vma->rb_root);
+}
+
+static inline void
+anon_vma_interval_tree_post_update_vma(struct vm_area_struct *vma)
+{
+	struct anon_vma_chain *avc;
+
+	list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
+		anon_vma_interval_tree_insert(avc, &avc->anon_vma->rb_root);
+}
+
+static unsigned long count_vma_pages_range(struct mm_struct *mm,
+		unsigned long addr, unsigned long end)
+{
+	VMA_ITERATOR(vmi, mm, addr);
+	struct vm_area_struct *vma;
+	unsigned long nr_pages = 0;
+
+	for_each_vma_range(vmi, vma, end) {
+		unsigned long vm_start = max(addr, vma->vm_start);
+		unsigned long vm_end = min(end, vma->vm_end);
+
+		nr_pages += PHYS_PFN(vm_end - vm_start);
+	}
+
+	return nr_pages;
+}
+
+static void __vma_link_file(struct vm_area_struct *vma,
+			    struct address_space *mapping)
+{
+	if (vma->vm_flags & VM_SHARED)
+		mapping_allow_writable(mapping);
+
+	flush_dcache_mmap_lock(mapping);
+	vma_interval_tree_insert(vma, &mapping->i_mmap);
+	flush_dcache_mmap_unlock(mapping);
+}
+
+/*
+ * vma_mas_store() - Store a VMA in the maple tree.
+ * @vma: The vm_area_struct
+ * @mas: The maple state
+ *
+ * Efficient way to store a VMA in the maple tree when the @mas has already
+ * walked to the correct location.
+ *
+ * Note: the end address is inclusive in the maple tree.
+ */
+void vma_mas_store(struct vm_area_struct *vma, struct ma_state *mas)
+{
+	trace_vma_store(mas->tree, vma);
+	mas_set_range(mas, vma->vm_start, vma->vm_end - 1);
+	mas_store_prealloc(mas, vma);
+}
+
+/*
+ * vma_mas_remove() - Remove a VMA from the maple tree.
+ * @vma: The vm_area_struct
+ * @mas: The maple state
+ *
+ * Efficient way to remove a VMA from the maple tree when the @mas has already
+ * been established and points to the correct location.
+ * Note: the end address is inclusive in the maple tree.
+ */
+void vma_mas_remove(struct vm_area_struct *vma, struct ma_state *mas)
+{
+	trace_vma_mas_szero(mas->tree, vma->vm_start, vma->vm_end - 1);
+	mas->index = vma->vm_start;
+	mas->last = vma->vm_end - 1;
+	mas_store_prealloc(mas, NULL);
+}
+
+/*
+ * vma_mas_szero() - Set a given range to zero.  Used when modifying a
+ * vm_area_struct start or end.
+ *
+ * @mas: The maple tree ma_state
+ * @start: The start address to zero
+ * @end: The end address to zero.
+ */
+static inline void vma_mas_szero(struct ma_state *mas, unsigned long start,
+				unsigned long end)
+{
+	trace_vma_mas_szero(mas->tree, start, end - 1);
+	mas_set_range(mas, start, end - 1);
+	mas_store_prealloc(mas, NULL);
+}
+
+static int vma_link(struct mm_struct *mm, struct vm_area_struct *vma)
+{
+	MA_STATE(mas, &mm->mm_mt, 0, 0);
+	struct address_space *mapping = NULL;
+
+	if (mas_preallocate(&mas, vma, GFP_KERNEL))
+		return -ENOMEM;
+
+	if (vma->vm_file) {
+		mapping = vma->vm_file->f_mapping;
+		i_mmap_lock_write(mapping);
+	}
+
+	vma_mas_store(vma, &mas);
+
+	if (mapping) {
+		__vma_link_file(vma, mapping);
+		i_mmap_unlock_write(mapping);
+	}
+
+	mm->map_count++;
+	validate_mm(mm);
+	return 0;
+}
+
+/*
+ * vma_expand - Expand an existing VMA
+ *
+ * @mas: The maple state
+ * @vma: The vma to expand
+ * @start: The start of the vma
+ * @end: The exclusive end of the vma
+ * @pgoff: The page offset of vma
+ * @next: The current of next vma.
+ *
+ * Expand @vma to @start and @end.  Can expand off the start and end.  Will
+ * expand over @next if it's different from @vma and @end == @next->vm_end.
+ * Checking if the @vma can expand and merge with @next needs to be handled by
+ * the caller.
+ *
+ * Returns: 0 on success
+ */
+inline int vma_expand(struct ma_state *mas, struct vm_area_struct *vma,
+		      unsigned long start, unsigned long end, pgoff_t pgoff,
+		      struct vm_area_struct *next)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	struct address_space *mapping = NULL;
+	struct rb_root_cached *root = NULL;
+	struct anon_vma *anon_vma = vma->anon_vma;
+	struct file *file = vma->vm_file;
+	bool remove_next = false;
+	struct vm_area_struct *anon_dup = NULL;
+
+	if (next && (vma != next) && (end == next->vm_end)) {
+		remove_next = true;
+		if (next->anon_vma && !vma->anon_vma) {
+			int error;
+
+			anon_vma = next->anon_vma;
+			vma->anon_vma = anon_vma;
+			error = anon_vma_clone(vma, next);
+			if (error)
+				return error;
+
+			anon_dup = vma;
+		}
+	}
+
+	/* Not merging but overwriting any part of next is not handled. */
+	VM_BUG_ON(next && !remove_next && next != vma && end > next->vm_start);
+	/* Only handles expanding */
+	VM_BUG_ON(vma->vm_start < start || vma->vm_end > end);
+
+	if (mas_preallocate(mas, vma, GFP_KERNEL))
+		goto nomem;
+
+	vma_adjust_trans_huge(vma, start, end, 0);
+
+	if (file) {
+		mapping = file->f_mapping;
+		root = &mapping->i_mmap;
+		uprobe_munmap(vma, vma->vm_start, vma->vm_end);
+		i_mmap_lock_write(mapping);
+	}
+
+	if (anon_vma) {
+		anon_vma_lock_write(anon_vma);
+		anon_vma_interval_tree_pre_update_vma(vma);
+	}
+
+	if (file) {
+		flush_dcache_mmap_lock(mapping);
+		vma_interval_tree_remove(vma, root);
+	}
+
+	vma->vm_start = start;
+	vma->vm_end = end;
+	vma->vm_pgoff = pgoff;
+	/* Note: mas must be pointing to the expanding VMA */
+	vma_mas_store(vma, mas);
+
+	if (file) {
+		vma_interval_tree_insert(vma, root);
+		flush_dcache_mmap_unlock(mapping);
+	}
+
+	/* Expanding over the next vma */
+	if (remove_next && file) {
+		__remove_shared_vm_struct(next, file, mapping);
+	}
+
+	if (anon_vma) {
+		anon_vma_interval_tree_post_update_vma(vma);
+		anon_vma_unlock_write(anon_vma);
+	}
+
+	if (file) {
+		i_mmap_unlock_write(mapping);
+		uprobe_mmap(vma);
+	}
+
+	if (remove_next) {
+		if (file) {
+			uprobe_munmap(next, next->vm_start, next->vm_end);
+			fput(file);
+		}
+		if (next->anon_vma)
+			anon_vma_merge(vma, next);
+		mm->map_count--;
+		mpol_put(vma_policy(next));
+		vm_area_free(next);
+	}
+
+	validate_mm(mm);
+	return 0;
+
+nomem:
+	if (anon_dup)
+		unlink_anon_vmas(anon_dup);
+
+	return -ENOMEM;
+}
+
+/*
+ * We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that
+ * is already present in an i_mmap tree without adjusting the tree.
+ * The following helper function should be used when such adjustments
+ * are necessary.  The "insert" vma (if any) is to be inserted
+ * before we drop the necessary locks.
+ */
+int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
+	unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert,
+	struct vm_area_struct *expand)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	struct vm_area_struct *next_next = NULL;	/* uninit var warning */
+	struct vm_area_struct *next = find_vma(mm, vma->vm_end);
+	struct vm_area_struct *orig_vma = vma;
+	struct address_space *mapping = NULL;
+	struct rb_root_cached *root = NULL;
+	struct anon_vma *anon_vma = NULL;
+	struct file *file = vma->vm_file;
+	bool vma_changed = false;
+	long adjust_next = 0;
+	int remove_next = 0;
+	MA_STATE(mas, &mm->mm_mt, 0, 0);
+	struct vm_area_struct *exporter = NULL, *importer = NULL;
+	struct vm_area_struct *anon_dup = NULL;
+
+	if (next && !insert) {
+		if (end >= next->vm_end) {
+			/*
+			 * vma expands, overlapping all the next, and
+			 * perhaps the one after too (mprotect case 6).
+			 * The only other cases that gets here are
+			 * case 1, case 7 and case 8.
+			 */
+			if (next == expand) {
+				/*
+				 * The only case where we don't expand "vma"
+				 * and we expand "next" instead is case 8.
+				 */
+				VM_WARN_ON(end != next->vm_end);
+				/*
+				 * remove_next == 3 means we're
+				 * removing "vma" and that to do so we
+				 * swapped "vma" and "next".
+				 */
+				remove_next = 3;
+				VM_WARN_ON(file != next->vm_file);
+				swap(vma, next);
+			} else {
+				VM_WARN_ON(expand != vma);
+				/*
+				 * case 1, 6, 7, remove_next == 2 is case 6,
+				 * remove_next == 1 is case 1 or 7.
+				 */
+				remove_next = 1 + (end > next->vm_end);
+				if (remove_next == 2)
+					next_next = find_vma(mm, next->vm_end);
+
+				VM_WARN_ON(remove_next == 2 &&
+					   end != next_next->vm_end);
+			}
+
+			exporter = next;
+			importer = vma;
+
+			/*
+			 * If next doesn't have anon_vma, import from vma after
+			 * next, if the vma overlaps with it.
+			 */
+			if (remove_next == 2 && !next->anon_vma)
+				exporter = next_next;
+
+		} else if (end > next->vm_start) {
+			/*
+			 * vma expands, overlapping part of the next:
+			 * mprotect case 5 shifting the boundary up.
+			 */
+			adjust_next = (end - next->vm_start);
+			exporter = next;
+			importer = vma;
+			VM_WARN_ON(expand != importer);
+		} else if (end < vma->vm_end) {
+			/*
+			 * vma shrinks, and !insert tells it's not
+			 * split_vma inserting another: so it must be
+			 * mprotect case 4 shifting the boundary down.
+			 */
+			adjust_next = -(vma->vm_end - end);
+			exporter = vma;
+			importer = next;
+			VM_WARN_ON(expand != importer);
+		}
+
+		/*
+		 * Easily overlooked: when mprotect shifts the boundary,
+		 * make sure the expanding vma has anon_vma set if the
+		 * shrinking vma had, to cover any anon pages imported.
+		 */
+		if (exporter && exporter->anon_vma && !importer->anon_vma) {
+			int error;
+
+			importer->anon_vma = exporter->anon_vma;
+			error = anon_vma_clone(importer, exporter);
+			if (error)
+				return error;
+
+			anon_dup = importer;
+		}
+	}
+
+	if (mas_preallocate(&mas, vma, GFP_KERNEL)) {
+		if (anon_dup)
+			unlink_anon_vmas(anon_dup);
+
+		return -ENOMEM;
+	}
+
+	vma_adjust_trans_huge(orig_vma, start, end, adjust_next);
+	if (file) {
+		mapping = file->f_mapping;
+		root = &mapping->i_mmap;
+		uprobe_munmap(vma, vma->vm_start, vma->vm_end);
+
+		if (adjust_next)
+			uprobe_munmap(next, next->vm_start, next->vm_end);
+
+		i_mmap_lock_write(mapping);
+		if (insert && insert->vm_file) {
+			/*
+			 * Put into interval tree now, so instantiated pages
+			 * are visible to arm/parisc __flush_dcache_page
+			 * throughout; but we cannot insert into address
+			 * space until vma start or end is updated.
+			 */
+			__vma_link_file(insert, insert->vm_file->f_mapping);
+		}
+	}
+
+	anon_vma = vma->anon_vma;
+	if (!anon_vma && adjust_next)
+		anon_vma = next->anon_vma;
+	if (anon_vma) {
+		VM_WARN_ON(adjust_next && next->anon_vma &&
+			   anon_vma != next->anon_vma);
+		anon_vma_lock_write(anon_vma);
+		anon_vma_interval_tree_pre_update_vma(vma);
+		if (adjust_next)
+			anon_vma_interval_tree_pre_update_vma(next);
+	}
+
+	if (file) {
+		flush_dcache_mmap_lock(mapping);
+		vma_interval_tree_remove(vma, root);
+		if (adjust_next)
+			vma_interval_tree_remove(next, root);
+	}
+
+	if (start != vma->vm_start) {
+		if ((vma->vm_start < start) &&
+		    (!insert || (insert->vm_end != start))) {
+			vma_mas_szero(&mas, vma->vm_start, start);
+			VM_WARN_ON(insert && insert->vm_start > vma->vm_start);
+		} else {
+			vma_changed = true;
+		}
+		vma->vm_start = start;
+	}
+	if (end != vma->vm_end) {
+		if (vma->vm_end > end) {
+			if ((vma->vm_end + adjust_next != end) &&
+			    (!insert || (insert->vm_start != end))) {
+				vma_mas_szero(&mas, end, vma->vm_end);
+				mas_reset(&mas);
+				VM_WARN_ON(insert &&
+					   insert->vm_end < vma->vm_end);
+			}
+		} else {
+			vma_changed = true;
+		}
+		vma->vm_end = end;
+	}
+
+	if (vma_changed)
+		vma_mas_store(vma, &mas);
+
+	vma->vm_pgoff = pgoff;
+	if (adjust_next) {
+		next->vm_start += adjust_next;
+		next->vm_pgoff += adjust_next >> PAGE_SHIFT;
+		vma_mas_store(next, &mas);
+	}
+
+	if (file) {
+		if (adjust_next)
+			vma_interval_tree_insert(next, root);
+		vma_interval_tree_insert(vma, root);
+		flush_dcache_mmap_unlock(mapping);
+	}
+
+	if (remove_next && file) {
+		__remove_shared_vm_struct(next, file, mapping);
+		if (remove_next == 2)
+			__remove_shared_vm_struct(next_next, file, mapping);
+	} else if (insert) {
+		/*
+		 * split_vma has split insert from vma, and needs
+		 * us to insert it before dropping the locks
+		 * (it may either follow vma or precede it).
+		 */
+		mas_reset(&mas);
+		vma_mas_store(insert, &mas);
+		mm->map_count++;
+	}
+
+	if (anon_vma) {
+		anon_vma_interval_tree_post_update_vma(vma);
+		if (adjust_next)
+			anon_vma_interval_tree_post_update_vma(next);
+		anon_vma_unlock_write(anon_vma);
+	}
+
+	if (file) {
+		i_mmap_unlock_write(mapping);
+		uprobe_mmap(vma);
+
+		if (adjust_next)
+			uprobe_mmap(next);
+	}
+
+	if (remove_next) {
+again:
+		if (file) {
+			uprobe_munmap(next, next->vm_start, next->vm_end);
+			fput(file);
+		}
+		if (next->anon_vma)
+			anon_vma_merge(vma, next);
+		mm->map_count--;
+		mpol_put(vma_policy(next));
+		if (remove_next != 2)
+			BUG_ON(vma->vm_end < next->vm_end);
+		vm_area_free(next);
+
+		/*
+		 * In mprotect's case 6 (see comments on vma_merge),
+		 * we must remove next_next too.
+		 */
+		if (remove_next == 2) {
+			remove_next = 1;
+			next = next_next;
+			goto again;
+		}
+	}
+	if (insert && file)
+		uprobe_mmap(insert);
+
+	mas_destroy(&mas);
+	validate_mm(mm);
+
+	return 0;
+}
+
+/*
+ * If the vma has a ->close operation then the driver probably needs to release
+ * per-vma resources, so we don't attempt to merge those.
+ */
+static inline int is_mergeable_vma(struct vm_area_struct *vma,
+				struct file *file, unsigned long vm_flags,
+				struct vm_userfaultfd_ctx vm_userfaultfd_ctx,
+				struct anon_vma_name *anon_name)
+{
+	/*
+	 * VM_SOFTDIRTY should not prevent from VMA merging, if we
+	 * match the flags but dirty bit -- the caller should mark
+	 * merged VMA as dirty. If dirty bit won't be excluded from
+	 * comparison, we increase pressure on the memory system forcing
+	 * the kernel to generate new VMAs when old one could be
+	 * extended instead.
+	 */
+	if ((vma->vm_flags ^ vm_flags) & ~VM_SOFTDIRTY)
+		return 0;
+	if (vma->vm_file != file)
+		return 0;
+	if (vma->vm_ops && vma->vm_ops->close)
+		return 0;
+	if (!is_mergeable_vm_userfaultfd_ctx(vma, vm_userfaultfd_ctx))
+		return 0;
+	if (!anon_vma_name_eq(anon_vma_name(vma), anon_name))
+		return 0;
+	return 1;
+}
+
+static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1,
+					struct anon_vma *anon_vma2,
+					struct vm_area_struct *vma)
+{
+	/*
+	 * The list_is_singular() test is to avoid merging VMA cloned from
+	 * parents. This can improve scalability caused by anon_vma lock.
+	 */
+	if ((!anon_vma1 || !anon_vma2) && (!vma ||
+		list_is_singular(&vma->anon_vma_chain)))
+		return 1;
+	return anon_vma1 == anon_vma2;
+}
+
+/*
+ * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
+ * in front of (at a lower virtual address and file offset than) the vma.
+ *
+ * We cannot merge two vmas if they have differently assigned (non-NULL)
+ * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
+ *
+ * We don't check here for the merged mmap wrapping around the end of pagecache
+ * indices (16TB on ia32) because do_mmap() does not permit mmap's which
+ * wrap, nor mmaps which cover the final page at index -1UL.
+ */
+static int
+can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags,
+		     struct anon_vma *anon_vma, struct file *file,
+		     pgoff_t vm_pgoff,
+		     struct vm_userfaultfd_ctx vm_userfaultfd_ctx,
+		     struct anon_vma_name *anon_name)
+{
+	if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx, anon_name) &&
+	    is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
+		if (vma->vm_pgoff == vm_pgoff)
+			return 1;
+	}
+	return 0;
+}
+
+/*
+ * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
+ * beyond (at a higher virtual address and file offset than) the vma.
+ *
+ * We cannot merge two vmas if they have differently assigned (non-NULL)
+ * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
+ */
+static int
+can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
+		    struct anon_vma *anon_vma, struct file *file,
+		    pgoff_t vm_pgoff,
+		    struct vm_userfaultfd_ctx vm_userfaultfd_ctx,
+		    struct anon_vma_name *anon_name)
+{
+	if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx, anon_name) &&
+	    is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
+		pgoff_t vm_pglen;
+		vm_pglen = vma_pages(vma);
+		if (vma->vm_pgoff + vm_pglen == vm_pgoff)
+			return 1;
+	}
+	return 0;
+}
+
+/*
+ * Given a mapping request (addr,end,vm_flags,file,pgoff,anon_name),
+ * figure out whether that can be merged with its predecessor or its
+ * successor.  Or both (it neatly fills a hole).
+ *
+ * In most cases - when called for mmap, brk or mremap - [addr,end) is
+ * certain not to be mapped by the time vma_merge is called; but when
+ * called for mprotect, it is certain to be already mapped (either at
+ * an offset within prev, or at the start of next), and the flags of
+ * this area are about to be changed to vm_flags - and the no-change
+ * case has already been eliminated.
+ *
+ * The following mprotect cases have to be considered, where AAAA is
+ * the area passed down from mprotect_fixup, never extending beyond one
+ * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
+ *
+ *     AAAA             AAAA                   AAAA
+ *    PPPPPPNNNNNN    PPPPPPNNNNNN       PPPPPPNNNNNN
+ *    cannot merge    might become       might become
+ *                    PPNNNNNNNNNN       PPPPPPPPPPNN
+ *    mmap, brk or    case 4 below       case 5 below
+ *    mremap move:
+ *                        AAAA               AAAA
+ *                    PPPP    NNNN       PPPPNNNNXXXX
+ *                    might become       might become
+ *                    PPPPPPPPPPPP 1 or  PPPPPPPPPPPP 6 or
+ *                    PPPPPPPPNNNN 2 or  PPPPPPPPXXXX 7 or
+ *                    PPPPNNNNNNNN 3     PPPPXXXXXXXX 8
+ *
+ * It is important for case 8 that the vma NNNN overlapping the
+ * region AAAA is never going to extended over XXXX. Instead XXXX must
+ * be extended in region AAAA and NNNN must be removed. This way in
+ * all cases where vma_merge succeeds, the moment vma_adjust drops the
+ * rmap_locks, the properties of the merged vma will be already
+ * correct for the whole merged range. Some of those properties like
+ * vm_page_prot/vm_flags may be accessed by rmap_walks and they must
+ * be correct for the whole merged range immediately after the
+ * rmap_locks are released. Otherwise if XXXX would be removed and
+ * NNNN would be extended over the XXXX range, remove_migration_ptes
+ * or other rmap walkers (if working on addresses beyond the "end"
+ * parameter) may establish ptes with the wrong permissions of NNNN
+ * instead of the right permissions of XXXX.
+ */
+struct vm_area_struct *vma_merge(struct mm_struct *mm,
+			struct vm_area_struct *prev, unsigned long addr,
+			unsigned long end, unsigned long vm_flags,
+			struct anon_vma *anon_vma, struct file *file,
+			pgoff_t pgoff, struct mempolicy *policy,
+			struct vm_userfaultfd_ctx vm_userfaultfd_ctx,
+			struct anon_vma_name *anon_name)
+{
+	pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
+	struct vm_area_struct *mid, *next, *res;
+	int err = -1;
+	bool merge_prev = false;
+	bool merge_next = false;
+
+	/*
+	 * We later require that vma->vm_flags == vm_flags,
+	 * so this tests vma->vm_flags & VM_SPECIAL, too.
+	 */
+	if (vm_flags & VM_SPECIAL)
+		return NULL;
+
+	next = find_vma(mm, prev ? prev->vm_end : 0);
+	mid = next;
+	if (next && next->vm_end == end)		/* cases 6, 7, 8 */
+		next = find_vma(mm, next->vm_end);
+
+	/* verify some invariant that must be enforced by the caller */
+	VM_WARN_ON(prev && addr <= prev->vm_start);
+	VM_WARN_ON(mid && end > mid->vm_end);
+	VM_WARN_ON(addr >= end);
+
+	/* Can we merge the predecessor? */
+	if (prev && prev->vm_end == addr &&
+			mpol_equal(vma_policy(prev), policy) &&
+			can_vma_merge_after(prev, vm_flags,
+					    anon_vma, file, pgoff,
+					    vm_userfaultfd_ctx, anon_name)) {
+		merge_prev = true;
+	}
+	/* Can we merge the successor? */
+	if (next && end == next->vm_start &&
+			mpol_equal(policy, vma_policy(next)) &&
+			can_vma_merge_before(next, vm_flags,
+					     anon_vma, file, pgoff+pglen,
+					     vm_userfaultfd_ctx, anon_name)) {
+		merge_next = true;
+	}
+	/* Can we merge both the predecessor and the successor? */
+	if (merge_prev && merge_next &&
+			is_mergeable_anon_vma(prev->anon_vma,
+				next->anon_vma, NULL)) {	 /* cases 1, 6 */
+		err = __vma_adjust(prev, prev->vm_start,
+					next->vm_end, prev->vm_pgoff, NULL,
+					prev);
+		res = prev;
+	} else if (merge_prev) {			/* cases 2, 5, 7 */
+		err = __vma_adjust(prev, prev->vm_start,
+					end, prev->vm_pgoff, NULL, prev);
+		res = prev;
+	} else if (merge_next) {
+		if (prev && addr < prev->vm_end)	/* case 4 */
+			err = __vma_adjust(prev, prev->vm_start,
+					addr, prev->vm_pgoff, NULL, next);
+		else					/* cases 3, 8 */
+			err = __vma_adjust(mid, addr, next->vm_end,
+					next->vm_pgoff - pglen, NULL, next);
+		res = next;
+	}
+
+	/*
+	 * Cannot merge with predecessor or successor or error in __vma_adjust?
+	 */
+	if (err)
+		return NULL;
+	khugepaged_enter_vma(res, vm_flags);
+	return res;
+}
+
+/*
+ * Rough compatibility check to quickly see if it's even worth looking
+ * at sharing an anon_vma.
+ *
+ * They need to have the same vm_file, and the flags can only differ
+ * in things that mprotect may change.
+ *
+ * NOTE! The fact that we share an anon_vma doesn't _have_ to mean that
+ * we can merge the two vma's. For example, we refuse to merge a vma if
+ * there is a vm_ops->close() function, because that indicates that the
+ * driver is doing some kind of reference counting. But that doesn't
+ * really matter for the anon_vma sharing case.
+ */
+static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct *b)
+{
+	return a->vm_end == b->vm_start &&
+		mpol_equal(vma_policy(a), vma_policy(b)) &&
+		a->vm_file == b->vm_file &&
+		!((a->vm_flags ^ b->vm_flags) & ~(VM_ACCESS_FLAGS | VM_SOFTDIRTY)) &&
+		b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT);
+}
+
+/*
+ * Do some basic sanity checking to see if we can re-use the anon_vma
+ * from 'old'. The 'a'/'b' vma's are in VM order - one of them will be
+ * the same as 'old', the other will be the new one that is trying
+ * to share the anon_vma.
+ *
+ * NOTE! This runs with mmap_lock held for reading, so it is possible that
+ * the anon_vma of 'old' is concurrently in the process of being set up
+ * by another page fault trying to merge _that_. But that's ok: if it
+ * is being set up, that automatically means that it will be a singleton
+ * acceptable for merging, so we can do all of this optimistically. But
+ * we do that READ_ONCE() to make sure that we never re-load the pointer.
+ *
+ * IOW: that the "list_is_singular()" test on the anon_vma_chain only
+ * matters for the 'stable anon_vma' case (ie the thing we want to avoid
+ * is to return an anon_vma that is "complex" due to having gone through
+ * a fork).
+ *
+ * We also make sure that the two vma's are compatible (adjacent,
+ * and with the same memory policies). That's all stable, even with just
+ * a read lock on the mmap_lock.
+ */
+static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_area_struct *a, struct vm_area_struct *b)
+{
+	if (anon_vma_compatible(a, b)) {
+		struct anon_vma *anon_vma = READ_ONCE(old->anon_vma);
+
+		if (anon_vma && list_is_singular(&old->anon_vma_chain))
+			return anon_vma;
+	}
+	return NULL;
+}
+
+/*
+ * find_mergeable_anon_vma is used by anon_vma_prepare, to check
+ * neighbouring vmas for a suitable anon_vma, before it goes off
+ * to allocate a new anon_vma.  It checks because a repetitive
+ * sequence of mprotects and faults may otherwise lead to distinct
+ * anon_vmas being allocated, preventing vma merge in subsequent
+ * mprotect.
+ */
+struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
+{
+	MA_STATE(mas, &vma->vm_mm->mm_mt, vma->vm_end, vma->vm_end);
+	struct anon_vma *anon_vma = NULL;
+	struct vm_area_struct *prev, *next;
+
+	/* Try next first. */
+	next = mas_walk(&mas);
+	if (next) {
+		anon_vma = reusable_anon_vma(next, vma, next);
+		if (anon_vma)
+			return anon_vma;
+	}
+
+	prev = mas_prev(&mas, 0);
+	VM_BUG_ON_VMA(prev != vma, vma);
+	prev = mas_prev(&mas, 0);
+	/* Try prev next. */
+	if (prev)
+		anon_vma = reusable_anon_vma(prev, prev, vma);
+
+	/*
+	 * We might reach here with anon_vma == NULL if we can't find
+	 * any reusable anon_vma.
+	 * There's no absolute need to look only at touching neighbours:
+	 * we could search further afield for "compatible" anon_vmas.
+	 * But it would probably just be a waste of time searching,
+	 * or lead to too many vmas hanging off the same anon_vma.
+	 * We're trying to allow mprotect remerging later on,
+	 * not trying to minimize memory used for anon_vmas.
+	 */
+	return anon_vma;
+}
+
+/*
+ * If a hint addr is less than mmap_min_addr change hint to be as
+ * low as possible but still greater than mmap_min_addr
+ */
+static inline unsigned long round_hint_to_min(unsigned long hint)
+{
+	hint &= PAGE_MASK;
+	if (((void *)hint != NULL) &&
+	    (hint < mmap_min_addr))
+		return PAGE_ALIGN(mmap_min_addr);
+	return hint;
+}
+
+int mlock_future_check(struct mm_struct *mm, unsigned long flags,
+		       unsigned long len)
+{
+	unsigned long locked, lock_limit;
+
+	/*  mlock MCL_FUTURE? */
+	if (flags & VM_LOCKED) {
+		locked = len >> PAGE_SHIFT;
+		locked += mm->locked_vm;
+		lock_limit = rlimit(RLIMIT_MEMLOCK);
+		lock_limit >>= PAGE_SHIFT;
+		if (locked > lock_limit && !capable(CAP_IPC_LOCK))
+			return -EAGAIN;
+	}
+	return 0;
+}
+
+static inline u64 file_mmap_size_max(struct file *file, struct inode *inode)
+{
+	if (S_ISREG(inode->i_mode))
+		return MAX_LFS_FILESIZE;
+
+	if (S_ISBLK(inode->i_mode))
+		return MAX_LFS_FILESIZE;
+
+	if (S_ISSOCK(inode->i_mode))
+		return MAX_LFS_FILESIZE;
+
+	/* Special "we do even unsigned file positions" case */
+	if (file->f_mode & FMODE_UNSIGNED_OFFSET)
+		return 0;
+
+	/* Yes, random drivers might want more. But I'm tired of buggy drivers */
+	return ULONG_MAX;
+}
+
+static inline bool file_mmap_ok(struct file *file, struct inode *inode,
+				unsigned long pgoff, unsigned long len)
+{
+	u64 maxsize = file_mmap_size_max(file, inode);
+
+	if (maxsize && len > maxsize)
+		return false;
+	maxsize -= len;
+	if (pgoff > maxsize >> PAGE_SHIFT)
+		return false;
+	return true;
+}
+
+/*
+ * The caller must write-lock current->mm->mmap_lock.
+ */
+unsigned long do_mmap(struct file *file, unsigned long addr,
+			unsigned long len, unsigned long prot,
+			unsigned long flags, unsigned long pgoff,
+			unsigned long *populate, struct list_head *uf)
+{
+	struct mm_struct *mm = current->mm;
+	vm_flags_t vm_flags;
+	int pkey = 0;
+
+	validate_mm(mm);
+	*populate = 0;
+
+	if (!len)
+		return -EINVAL;
+
+	/*
+	 * Does the application expect PROT_READ to imply PROT_EXEC?
+	 *
+	 * (the exception is when the underlying filesystem is noexec
+	 *  mounted, in which case we dont add PROT_EXEC.)
+	 */
+	if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
+		if (!(file && path_noexec(&file->f_path)))
+			prot |= PROT_EXEC;
+
+	/* force arch specific MAP_FIXED handling in get_unmapped_area */
+	if (flags & MAP_FIXED_NOREPLACE)
+		flags |= MAP_FIXED;
+
+	if (!(flags & MAP_FIXED))
+		addr = round_hint_to_min(addr);
+
+	/* Careful about overflows.. */
+	len = PAGE_ALIGN(len);
+	if (!len)
+		return -ENOMEM;
+
+	/* offset overflow? */
+	if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
+		return -EOVERFLOW;
+
+	/* Too many mappings? */
+	if (mm->map_count > sysctl_max_map_count)
+		return -ENOMEM;
+
+	/* Obtain the address to map to. we verify (or select) it and ensure
+	 * that it represents a valid section of the address space.
+	 */
+	addr = get_unmapped_area(file, addr, len, pgoff, flags);
+	if (IS_ERR_VALUE(addr))
+		return addr;
+
+	if (flags & MAP_FIXED_NOREPLACE) {
+		if (find_vma_intersection(mm, addr, addr + len))
+			return -EEXIST;
+	}
+
+	if (prot == PROT_EXEC) {
+		pkey = execute_only_pkey(mm);
+		if (pkey < 0)
+			pkey = 0;
+	}
+
+	/* Do simple checking here so the lower-level routines won't have
+	 * to. we assume access permissions have been handled by the open
+	 * of the memory object, so we don't do any here.
+	 */
+	vm_flags = calc_vm_prot_bits(prot, pkey) | calc_vm_flag_bits(flags) |
+			mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
+
+	if (flags & MAP_LOCKED)
+		if (!can_do_mlock())
+			return -EPERM;
+
+	if (mlock_future_check(mm, vm_flags, len))
+		return -EAGAIN;
+
+	if (file) {
+		struct inode *inode = file_inode(file);
+		unsigned long flags_mask;
+
+		if (!file_mmap_ok(file, inode, pgoff, len))
+			return -EOVERFLOW;
+
+		flags_mask = LEGACY_MAP_MASK | file->f_op->mmap_supported_flags;
+
+		switch (flags & MAP_TYPE) {
+		case MAP_SHARED:
+			/*
+			 * Force use of MAP_SHARED_VALIDATE with non-legacy
+			 * flags. E.g. MAP_SYNC is dangerous to use with
+			 * MAP_SHARED as you don't know which consistency model
+			 * you will get. We silently ignore unsupported flags
+			 * with MAP_SHARED to preserve backward compatibility.
+			 */
+			flags &= LEGACY_MAP_MASK;
+			fallthrough;
+		case MAP_SHARED_VALIDATE:
+			if (flags & ~flags_mask)
+				return -EOPNOTSUPP;
+			if (prot & PROT_WRITE) {
+				if (!(file->f_mode & FMODE_WRITE))
+					return -EACCES;
+				if (IS_SWAPFILE(file->f_mapping->host))
+					return -ETXTBSY;
+			}
+
+			/*
+			 * Make sure we don't allow writing to an append-only
+			 * file..
+			 */
+			if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE))
+				return -EACCES;
+
+			vm_flags |= VM_SHARED | VM_MAYSHARE;
+			if (!(file->f_mode & FMODE_WRITE))
+				vm_flags &= ~(VM_MAYWRITE | VM_SHARED);
+			fallthrough;
+		case MAP_PRIVATE:
+			if (!(file->f_mode & FMODE_READ))
+				return -EACCES;
+			if (path_noexec(&file->f_path)) {
+				if (vm_flags & VM_EXEC)
+					return -EPERM;
+				vm_flags &= ~VM_MAYEXEC;
+			}
+
+			if (!file->f_op->mmap)
+				return -ENODEV;
+			if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
+				return -EINVAL;
+			break;
+
+		default:
+			return -EINVAL;
+		}
+	} else {
+		switch (flags & MAP_TYPE) {
+		case MAP_SHARED:
+			if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
+				return -EINVAL;
+			/*
+			 * Ignore pgoff.
+			 */
+			pgoff = 0;
+			vm_flags |= VM_SHARED | VM_MAYSHARE;
+			break;
+		case MAP_PRIVATE:
+			/*
+			 * Set pgoff according to addr for anon_vma.
+			 */
+			pgoff = addr >> PAGE_SHIFT;
+			break;
+		default:
+			return -EINVAL;
+		}
+	}
+
+	/*
+	 * Set 'VM_NORESERVE' if we should not account for the
+	 * memory use of this mapping.
+	 */
+	if (flags & MAP_NORESERVE) {
+		/* We honor MAP_NORESERVE if allowed to overcommit */
+		if (sysctl_overcommit_memory != OVERCOMMIT_NEVER)
+			vm_flags |= VM_NORESERVE;
+
+		/* hugetlb applies strict overcommit unless MAP_NORESERVE */
+		if (file && is_file_hugepages(file))
+			vm_flags |= VM_NORESERVE;
+	}
+
+	addr = mmap_region(file, addr, len, vm_flags, pgoff, uf);
+	if (!IS_ERR_VALUE(addr) &&
+	    ((vm_flags & VM_LOCKED) ||
+	     (flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE))
+		*populate = len;
+	return addr;
+}
+
+unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
+			      unsigned long prot, unsigned long flags,
+			      unsigned long fd, unsigned long pgoff)
+{
+	struct file *file = NULL;
+	unsigned long retval;
+
+	if (!(flags & MAP_ANONYMOUS)) {
+		audit_mmap_fd(fd, flags);
+		file = fget(fd);
+		if (!file)
+			return -EBADF;
+		if (is_file_hugepages(file)) {
+			len = ALIGN(len, huge_page_size(hstate_file(file)));
+		} else if (unlikely(flags & MAP_HUGETLB)) {
+			retval = -EINVAL;
+			goto out_fput;
+		}
+	} else if (flags & MAP_HUGETLB) {
+		struct hstate *hs;
+
+		hs = hstate_sizelog((flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
+		if (!hs)
+			return -EINVAL;
+
+		len = ALIGN(len, huge_page_size(hs));
+		/*
+		 * VM_NORESERVE is used because the reservations will be
+		 * taken when vm_ops->mmap() is called
+		 */
+		file = hugetlb_file_setup(HUGETLB_ANON_FILE, len,
+				VM_NORESERVE,
+				HUGETLB_ANONHUGE_INODE,
+				(flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
+		if (IS_ERR(file))
+			return PTR_ERR(file);
+	}
+
+	retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
+out_fput:
+	if (file)
+		fput(file);
+	return retval;
+}
+
+SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
+		unsigned long, prot, unsigned long, flags,
+		unsigned long, fd, unsigned long, pgoff)
+{
+	return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
+}
+
+#ifdef __ARCH_WANT_SYS_OLD_MMAP
+struct mmap_arg_struct {
+	unsigned long addr;
+	unsigned long len;
+	unsigned long prot;
+	unsigned long flags;
+	unsigned long fd;
+	unsigned long offset;
+};
+
+SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
+{
+	struct mmap_arg_struct a;
+
+	if (copy_from_user(&a, arg, sizeof(a)))
+		return -EFAULT;
+	if (offset_in_page(a.offset))
+		return -EINVAL;
+
+	return ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
+			       a.offset >> PAGE_SHIFT);
+}
+#endif /* __ARCH_WANT_SYS_OLD_MMAP */
+
+/*
+ * Some shared mappings will want the pages marked read-only
+ * to track write events. If so, we'll downgrade vm_page_prot
+ * to the private version (using protection_map[] without the
+ * VM_SHARED bit).
+ */
+int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot)
+{
+	vm_flags_t vm_flags = vma->vm_flags;
+	const struct vm_operations_struct *vm_ops = vma->vm_ops;
+
+	/* If it was private or non-writable, the write bit is already clear */
+	if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED)))
+		return 0;
+
+	/* The backer wishes to know when pages are first written to? */
+	if (vm_ops && (vm_ops->page_mkwrite || vm_ops->pfn_mkwrite))
+		return 1;
+
+	/* The open routine did something to the protections that pgprot_modify
+	 * won't preserve? */
+	if (pgprot_val(vm_page_prot) !=
+	    pgprot_val(vm_pgprot_modify(vm_page_prot, vm_flags)))
+		return 0;
+
+	/*
+	 * Do we need to track softdirty? hugetlb does not support softdirty
+	 * tracking yet.
+	 */
+	if (vma_soft_dirty_enabled(vma) && !is_vm_hugetlb_page(vma))
+		return 1;
+
+	/* Do we need write faults for uffd-wp tracking? */
+	if (userfaultfd_wp(vma))
+		return 1;
+
+	/* Specialty mapping? */
+	if (vm_flags & VM_PFNMAP)
+		return 0;
+
+	/* Can the mapping track the dirty pages? */
+	return vma->vm_file && vma->vm_file->f_mapping &&
+		mapping_can_writeback(vma->vm_file->f_mapping);
+}
+
+/*
+ * We account for memory if it's a private writeable mapping,
+ * not hugepages and VM_NORESERVE wasn't set.
+ */
+static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags)
+{
+	/*
+	 * hugetlb has its own accounting separate from the core VM
+	 * VM_HUGETLB may not be set yet so we cannot check for that flag.
+	 */
+	if (file && is_file_hugepages(file))
+		return 0;
+
+	return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
+}
+
+/**
+ * unmapped_area() - Find an area between the low_limit and the high_limit with
+ * the correct alignment and offset, all from @info. Note: current->mm is used
+ * for the search.
+ *
+ * @info: The unmapped area information including the range (low_limit -
+ * hight_limit), the alignment offset and mask.
+ *
+ * Return: A memory address or -ENOMEM.
+ */
+static unsigned long unmapped_area(struct vm_unmapped_area_info *info)
+{
+	unsigned long length, gap, low_limit;
+	struct vm_area_struct *tmp;
+
+	MA_STATE(mas, &current->mm->mm_mt, 0, 0);
+
+	/* Adjust search length to account for worst case alignment overhead */
+	length = info->length + info->align_mask;
+	if (length < info->length)
+		return -ENOMEM;
+
+	low_limit = info->low_limit;
+retry:
+	if (mas_empty_area(&mas, low_limit, info->high_limit - 1, length))
+		return -ENOMEM;
+
+	gap = mas.index;
+	gap += (info->align_offset - gap) & info->align_mask;
+	tmp = mas_next(&mas, ULONG_MAX);
+	if (tmp && (tmp->vm_flags & VM_GROWSDOWN)) { /* Avoid prev check if possible */
+		if (vm_start_gap(tmp) < gap + length - 1) {
+			low_limit = tmp->vm_end;
+			mas_reset(&mas);
+			goto retry;
+		}
+	} else {
+		tmp = mas_prev(&mas, 0);
+		if (tmp && vm_end_gap(tmp) > gap) {
+			low_limit = vm_end_gap(tmp);
+			mas_reset(&mas);
+			goto retry;
+		}
+	}
+
+	return gap;
+}
+
+/**
+ * unmapped_area_topdown() - Find an area between the low_limit and the
+ * high_limit with * the correct alignment and offset at the highest available
+ * address, all from @info. Note: current->mm is used for the search.
+ *
+ * @info: The unmapped area information including the range (low_limit -
+ * hight_limit), the alignment offset and mask.
+ *
+ * Return: A memory address or -ENOMEM.
+ */
+static unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
+{
+	unsigned long length, gap, high_limit, gap_end;
+	struct vm_area_struct *tmp;
+
+	MA_STATE(mas, &current->mm->mm_mt, 0, 0);
+	/* Adjust search length to account for worst case alignment overhead */
+	length = info->length + info->align_mask;
+	if (length < info->length)
+		return -ENOMEM;
+
+	high_limit = info->high_limit;
+retry:
+	if (mas_empty_area_rev(&mas, info->low_limit, high_limit - 1,
+				length))
+		return -ENOMEM;
+
+	gap = mas.last + 1 - info->length;
+	gap -= (gap - info->align_offset) & info->align_mask;
+	gap_end = mas.last;
+	tmp = mas_next(&mas, ULONG_MAX);
+	if (tmp && (tmp->vm_flags & VM_GROWSDOWN)) { /* Avoid prev check if possible */
+		if (vm_start_gap(tmp) <= gap_end) {
+			high_limit = vm_start_gap(tmp);
+			mas_reset(&mas);
+			goto retry;
+		}
+	} else {
+		tmp = mas_prev(&mas, 0);
+		if (tmp && vm_end_gap(tmp) > gap) {
+			high_limit = tmp->vm_start;
+			mas_reset(&mas);
+			goto retry;
+		}
+	}
+
+	return gap;
+}
+
+/*
+ * Search for an unmapped address range.
+ *
+ * We are looking for a range that:
+ * - does not intersect with any VMA;
+ * - is contained within the [low_limit, high_limit) interval;
+ * - is at least the desired size.
+ * - satisfies (begin_addr & align_mask) == (align_offset & align_mask)
+ */
+unsigned long vm_unmapped_area(struct vm_unmapped_area_info *info)
+{
+	unsigned long addr;
+
+	if (info->flags & VM_UNMAPPED_AREA_TOPDOWN)
+		addr = unmapped_area_topdown(info);
+	else
+		addr = unmapped_area(info);
+
+	trace_vm_unmapped_area(addr, info);
+	return addr;
+}
+
+/* Get an address range which is currently unmapped.
+ * For shmat() with addr=0.
+ *
+ * Ugly calling convention alert:
+ * Return value with the low bits set means error value,
+ * ie
+ *	if (ret & ~PAGE_MASK)
+ *		error = ret;
+ *
+ * This function "knows" that -ENOMEM has the bits set.
+ */
+unsigned long
+generic_get_unmapped_area(struct file *filp, unsigned long addr,
+			  unsigned long len, unsigned long pgoff,
+			  unsigned long flags)
+{
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma, *prev;
+	struct vm_unmapped_area_info info;
+	const unsigned long mmap_end = arch_get_mmap_end(addr, len, flags);
+
+	if (len > mmap_end - mmap_min_addr)
+		return -ENOMEM;
+
+	if (flags & MAP_FIXED)
+		return addr;
+
+	if (addr) {
+		addr = PAGE_ALIGN(addr);
+		vma = find_vma_prev(mm, addr, &prev);
+		if (mmap_end - len >= addr && addr >= mmap_min_addr &&
+		    (!vma || addr + len <= vm_start_gap(vma)) &&
+		    (!prev || addr >= vm_end_gap(prev)))
+			return addr;
+	}
+
+	info.flags = 0;
+	info.length = len;
+	info.low_limit = mm->mmap_base;
+	info.high_limit = mmap_end;
+	info.align_mask = 0;
+	info.align_offset = 0;
+	return vm_unmapped_area(&info);
+}
+
+#ifndef HAVE_ARCH_UNMAPPED_AREA
+unsigned long
+arch_get_unmapped_area(struct file *filp, unsigned long addr,
+		       unsigned long len, unsigned long pgoff,
+		       unsigned long flags)
+{
+	return generic_get_unmapped_area(filp, addr, len, pgoff, flags);
+}
+#endif
+
+/*
+ * This mmap-allocator allocates new areas top-down from below the
+ * stack's low limit (the base):
+ */
+unsigned long
+generic_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
+				  unsigned long len, unsigned long pgoff,
+				  unsigned long flags)
+{
+	struct vm_area_struct *vma, *prev;
+	struct mm_struct *mm = current->mm;
+	struct vm_unmapped_area_info info;
+	const unsigned long mmap_end = arch_get_mmap_end(addr, len, flags);
+
+	/* requested length too big for entire address space */
+	if (len > mmap_end - mmap_min_addr)
+		return -ENOMEM;
+
+	if (flags & MAP_FIXED)
+		return addr;
+
+	/* requesting a specific address */
+	if (addr) {
+		addr = PAGE_ALIGN(addr);
+		vma = find_vma_prev(mm, addr, &prev);
+		if (mmap_end - len >= addr && addr >= mmap_min_addr &&
+				(!vma || addr + len <= vm_start_gap(vma)) &&
+				(!prev || addr >= vm_end_gap(prev)))
+			return addr;
+	}
+
+	info.flags = VM_UNMAPPED_AREA_TOPDOWN;
+	info.length = len;
+	info.low_limit = max(PAGE_SIZE, mmap_min_addr);
+	info.high_limit = arch_get_mmap_base(addr, mm->mmap_base);
+	info.align_mask = 0;
+	info.align_offset = 0;
+	addr = vm_unmapped_area(&info);
+
+	/*
+	 * A failed mmap() very likely causes application failure,
+	 * so fall back to the bottom-up function here. This scenario
+	 * can happen with large stack limits and large mmap()
+	 * allocations.
+	 */
+	if (offset_in_page(addr)) {
+		VM_BUG_ON(addr != -ENOMEM);
+		info.flags = 0;
+		info.low_limit = TASK_UNMAPPED_BASE;
+		info.high_limit = mmap_end;
+		addr = vm_unmapped_area(&info);
+	}
+
+	return addr;
+}
+
+#ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
+unsigned long
+arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
+			       unsigned long len, unsigned long pgoff,
+			       unsigned long flags)
+{
+	return generic_get_unmapped_area_topdown(filp, addr, len, pgoff, flags);
+}
+#endif
+
+unsigned long
+get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
+		unsigned long pgoff, unsigned long flags)
+{
+	unsigned long (*get_area)(struct file *, unsigned long,
+				  unsigned long, unsigned long, unsigned long);
+
+	unsigned long error = arch_mmap_check(addr, len, flags);
+	if (error)
+		return error;
+
+	/* Careful about overflows.. */
+	if (len > TASK_SIZE)
+		return -ENOMEM;
+
+	get_area = current->mm->get_unmapped_area;
+	if (file) {
+		if (file->f_op->get_unmapped_area)
+			get_area = file->f_op->get_unmapped_area;
+	} else if (flags & MAP_SHARED) {
+		/*
+		 * mmap_region() will call shmem_zero_setup() to create a file,
+		 * so use shmem's get_unmapped_area in case it can be huge.
+		 * do_mmap() will clear pgoff, so match alignment.
+		 */
+		pgoff = 0;
+		get_area = shmem_get_unmapped_area;
+	}
+
+	addr = get_area(file, addr, len, pgoff, flags);
+	if (IS_ERR_VALUE(addr))
+		return addr;
+
+	if (addr > TASK_SIZE - len)
+		return -ENOMEM;
+	if (offset_in_page(addr))
+		return -EINVAL;
+
+	error = security_mmap_addr(addr);
+	return error ? error : addr;
+}
+
+EXPORT_SYMBOL(get_unmapped_area);
+
+/**
+ * find_vma_intersection() - Look up the first VMA which intersects the interval
+ * @mm: The process address space.
+ * @start_addr: The inclusive start user address.
+ * @end_addr: The exclusive end user address.
+ *
+ * Returns: The first VMA within the provided range, %NULL otherwise.  Assumes
+ * start_addr < end_addr.
+ */
+struct vm_area_struct *find_vma_intersection(struct mm_struct *mm,
+					     unsigned long start_addr,
+					     unsigned long end_addr)
+{
+	unsigned long index = start_addr;
+
+	mmap_assert_locked(mm);
+	return mt_find(&mm->mm_mt, &index, end_addr - 1);
+}
+EXPORT_SYMBOL(find_vma_intersection);
+
+/**
+ * find_vma() - Find the VMA for a given address, or the next VMA.
+ * @mm: The mm_struct to check
+ * @addr: The address
+ *
+ * Returns: The VMA associated with addr, or the next VMA.
+ * May return %NULL in the case of no VMA at addr or above.
+ */
+struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
+{
+	unsigned long index = addr;
+
+	mmap_assert_locked(mm);
+	return mt_find(&mm->mm_mt, &index, ULONG_MAX);
+}
+EXPORT_SYMBOL(find_vma);
+
+/**
+ * find_vma_prev() - Find the VMA for a given address, or the next vma and
+ * set %pprev to the previous VMA, if any.
+ * @mm: The mm_struct to check
+ * @addr: The address
+ * @pprev: The pointer to set to the previous VMA
+ *
+ * Note that RCU lock is missing here since the external mmap_lock() is used
+ * instead.
+ *
+ * Returns: The VMA associated with @addr, or the next vma.
+ * May return %NULL in the case of no vma at addr or above.
+ */
+struct vm_area_struct *
+find_vma_prev(struct mm_struct *mm, unsigned long addr,
+			struct vm_area_struct **pprev)
+{
+	struct vm_area_struct *vma;
+	MA_STATE(mas, &mm->mm_mt, addr, addr);
+
+	vma = mas_walk(&mas);
+	*pprev = mas_prev(&mas, 0);
+	if (!vma)
+		vma = mas_next(&mas, ULONG_MAX);
+	return vma;
+}
+
+/*
+ * Verify that the stack growth is acceptable and
+ * update accounting. This is shared with both the
+ * grow-up and grow-down cases.
+ */
+static int acct_stack_growth(struct vm_area_struct *vma,
+			     unsigned long size, unsigned long grow)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	unsigned long new_start;
+
+	/* address space limit tests */
+	if (!may_expand_vm(mm, vma->vm_flags, grow))
+		return -ENOMEM;
+
+	/* Stack limit test */
+	if (size > rlimit(RLIMIT_STACK))
+		return -ENOMEM;
+
+	/* mlock limit tests */
+	if (mlock_future_check(mm, vma->vm_flags, grow << PAGE_SHIFT))
+		return -ENOMEM;
+
+	/* Check to ensure the stack will not grow into a hugetlb-only region */
+	new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start :
+			vma->vm_end - size;
+	if (is_hugepage_only_range(vma->vm_mm, new_start, size))
+		return -EFAULT;
+
+	/*
+	 * Overcommit..  This must be the final test, as it will
+	 * update security statistics.
+	 */
+	if (security_vm_enough_memory_mm(mm, grow))
+		return -ENOMEM;
+
+	return 0;
+}
+
+#if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
+/*
+ * PA-RISC uses this for its stack; IA64 for its Register Backing Store.
+ * vma is the last one with address > vma->vm_end.  Have to extend vma.
+ */
+static int expand_upwards(struct vm_area_struct *vma, unsigned long address)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	struct vm_area_struct *next;
+	unsigned long gap_addr;
+	int error = 0;
+	MA_STATE(mas, &mm->mm_mt, 0, 0);
+
+	if (!(vma->vm_flags & VM_GROWSUP))
+		return -EFAULT;
+
+	/* Guard against exceeding limits of the address space. */
+	address &= PAGE_MASK;
+	if (address >= (TASK_SIZE & PAGE_MASK))
+		return -ENOMEM;
+	address += PAGE_SIZE;
+
+	/* Enforce stack_guard_gap */
+	gap_addr = address + stack_guard_gap;
+
+	/* Guard against overflow */
+	if (gap_addr < address || gap_addr > TASK_SIZE)
+		gap_addr = TASK_SIZE;
+
+	next = find_vma_intersection(mm, vma->vm_end, gap_addr);
+	if (next && vma_is_accessible(next)) {
+		if (!(next->vm_flags & VM_GROWSUP))
+			return -ENOMEM;
+		/* Check that both stack segments have the same anon_vma? */
+	}
+
+	if (mas_preallocate(&mas, vma, GFP_KERNEL))
+		return -ENOMEM;
+
+	/* We must make sure the anon_vma is allocated. */
+	if (unlikely(anon_vma_prepare(vma))) {
+		mas_destroy(&mas);
+		return -ENOMEM;
+	}
+
+	/*
+	 * vma->vm_start/vm_end cannot change under us because the caller
+	 * is required to hold the mmap_lock in read mode.  We need the
+	 * anon_vma lock to serialize against concurrent expand_stacks.
+	 */
+	anon_vma_lock_write(vma->anon_vma);
+
+	/* Somebody else might have raced and expanded it already */
+	if (address > vma->vm_end) {
+		unsigned long size, grow;
+
+		size = address - vma->vm_start;
+		grow = (address - vma->vm_end) >> PAGE_SHIFT;
+
+		error = -ENOMEM;
+		if (vma->vm_pgoff + (size >> PAGE_SHIFT) >= vma->vm_pgoff) {
+			error = acct_stack_growth(vma, size, grow);
+			if (!error) {
+				/*
+				 * We only hold a shared mmap_lock lock here, so
+				 * we need to protect against concurrent vma
+				 * expansions.  anon_vma_lock_write() doesn't
+				 * help here, as we don't guarantee that all
+				 * growable vmas in a mm share the same root
+				 * anon vma.  So, we reuse mm->page_table_lock
+				 * to guard against concurrent vma expansions.
+				 */
+				spin_lock(&mm->page_table_lock);
+				if (vma->vm_flags & VM_LOCKED)
+					mm->locked_vm += grow;
+				vm_stat_account(mm, vma->vm_flags, grow);
+				anon_vma_interval_tree_pre_update_vma(vma);
+				vma->vm_end = address;
+				/* Overwrite old entry in mtree. */
+				vma_mas_store(vma, &mas);
+				anon_vma_interval_tree_post_update_vma(vma);
+				spin_unlock(&mm->page_table_lock);
+
+				perf_event_mmap(vma);
+			}
+		}
+	}
+	anon_vma_unlock_write(vma->anon_vma);
+	khugepaged_enter_vma(vma, vma->vm_flags);
+	mas_destroy(&mas);
+	return error;
+}
+#endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
+
+/*
+ * vma is the first one with address < vma->vm_start.  Have to extend vma.
+ * mmap_lock held for writing.
+ */
+int expand_downwards(struct vm_area_struct *vma, unsigned long address)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	MA_STATE(mas, &mm->mm_mt, vma->vm_start, vma->vm_start);
+	struct vm_area_struct *prev;
+	int error = 0;
+
+	if (!(vma->vm_flags & VM_GROWSDOWN))
+		return -EFAULT;
+
+	address &= PAGE_MASK;
+	if (address < mmap_min_addr || address < FIRST_USER_ADDRESS)
+		return -EPERM;
+
+	/* Enforce stack_guard_gap */
+	prev = mas_prev(&mas, 0);
+	/* Check that both stack segments have the same anon_vma? */
+	if (prev) {
+		if (!(prev->vm_flags & VM_GROWSDOWN) &&
+		    vma_is_accessible(prev) &&
+		    (address - prev->vm_end < stack_guard_gap))
+			return -ENOMEM;
+	}
+
+	if (mas_preallocate(&mas, vma, GFP_KERNEL))
+		return -ENOMEM;
+
+	/* We must make sure the anon_vma is allocated. */
+	if (unlikely(anon_vma_prepare(vma))) {
+		mas_destroy(&mas);
+		return -ENOMEM;
+	}
+
+	/*
+	 * vma->vm_start/vm_end cannot change under us because the caller
+	 * is required to hold the mmap_lock in read mode.  We need the
+	 * anon_vma lock to serialize against concurrent expand_stacks.
+	 */
+	anon_vma_lock_write(vma->anon_vma);
+
+	/* Somebody else might have raced and expanded it already */
+	if (address < vma->vm_start) {
+		unsigned long size, grow;
+
+		size = vma->vm_end - address;
+		grow = (vma->vm_start - address) >> PAGE_SHIFT;
+
+		error = -ENOMEM;
+		if (grow <= vma->vm_pgoff) {
+			error = acct_stack_growth(vma, size, grow);
+			if (!error) {
+				/*
+				 * We only hold a shared mmap_lock lock here, so
+				 * we need to protect against concurrent vma
+				 * expansions.  anon_vma_lock_write() doesn't
+				 * help here, as we don't guarantee that all
+				 * growable vmas in a mm share the same root
+				 * anon vma.  So, we reuse mm->page_table_lock
+				 * to guard against concurrent vma expansions.
+				 */
+				spin_lock(&mm->page_table_lock);
+				if (vma->vm_flags & VM_LOCKED)
+					mm->locked_vm += grow;
+				vm_stat_account(mm, vma->vm_flags, grow);
+				anon_vma_interval_tree_pre_update_vma(vma);
+				vma->vm_start = address;
+				vma->vm_pgoff -= grow;
+				/* Overwrite old entry in mtree. */
+				vma_mas_store(vma, &mas);
+				anon_vma_interval_tree_post_update_vma(vma);
+				spin_unlock(&mm->page_table_lock);
+
+				perf_event_mmap(vma);
+			}
+		}
+	}
+	anon_vma_unlock_write(vma->anon_vma);
+	khugepaged_enter_vma(vma, vma->vm_flags);
+	mas_destroy(&mas);
+	return error;
+}
+
+/* enforced gap between the expanding stack and other mappings. */
+unsigned long stack_guard_gap = 256UL<<PAGE_SHIFT;
+
+static int __init cmdline_parse_stack_guard_gap(char *p)
+{
+	unsigned long val;
+	char *endptr;
+
+	val = simple_strtoul(p, &endptr, 10);
+	if (!*endptr)
+		stack_guard_gap = val << PAGE_SHIFT;
+
+	return 1;
+}
+__setup("stack_guard_gap=", cmdline_parse_stack_guard_gap);
+
+#ifdef CONFIG_STACK_GROWSUP
+int expand_stack_locked(struct vm_area_struct *vma, unsigned long address)
+{
+	return expand_upwards(vma, address);
+}
+
+struct vm_area_struct *find_extend_vma_locked(struct mm_struct *mm, unsigned long addr)
+{
+	struct vm_area_struct *vma, *prev;
+
+	addr &= PAGE_MASK;
+	vma = find_vma_prev(mm, addr, &prev);
+	if (vma && (vma->vm_start <= addr))
+		return vma;
+	if (!prev)
+		return NULL;
+	if (expand_stack_locked(prev, addr))
+		return NULL;
+	if (prev->vm_flags & VM_LOCKED)
+		populate_vma_page_range(prev, addr, prev->vm_end, NULL);
+	return prev;
+}
+#else
+int expand_stack_locked(struct vm_area_struct *vma, unsigned long address)
+{
+	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
+		return -EINVAL;
+	return expand_downwards(vma, address);
+}
+
+struct vm_area_struct *find_extend_vma_locked(struct mm_struct *mm, unsigned long addr)
+{
+	struct vm_area_struct *vma;
+	unsigned long start;
+
+	addr &= PAGE_MASK;
+	vma = find_vma(mm, addr);
+	if (!vma)
+		return NULL;
+	if (vma->vm_start <= addr)
+		return vma;
+	start = vma->vm_start;
+	if (expand_stack_locked(vma, addr))
+		return NULL;
+	if (vma->vm_flags & VM_LOCKED)
+		populate_vma_page_range(vma, addr, start, NULL);
+	return vma;
+}
+#endif
+
+/*
+ * IA64 has some horrid mapping rules: it can expand both up and down,
+ * but with various special rules.
+ *
+ * We'll get rid of this architecture eventually, so the ugliness is
+ * temporary.
+ */
+#ifdef CONFIG_IA64
+static inline bool vma_expand_ok(struct vm_area_struct *vma, unsigned long addr)
+{
+	return REGION_NUMBER(addr) == REGION_NUMBER(vma->vm_start) &&
+		REGION_OFFSET(addr) < RGN_MAP_LIMIT;
+}
+
+/*
+ * IA64 stacks grow down, but there's a special register backing store
+ * that can grow up. Only sequentially, though, so the new address must
+ * match vm_end.
+ */
+static inline int vma_expand_up(struct vm_area_struct *vma, unsigned long addr)
+{
+	if (!vma_expand_ok(vma, addr))
+		return -EFAULT;
+	if (vma->vm_end != (addr & PAGE_MASK))
+		return -EFAULT;
+	return expand_upwards(vma, addr);
+}
+
+static inline bool vma_expand_down(struct vm_area_struct *vma, unsigned long addr)
+{
+	if (!vma_expand_ok(vma, addr))
+		return -EFAULT;
+	return expand_downwards(vma, addr);
+}
+
+#elif defined(CONFIG_STACK_GROWSUP)
+
+#define vma_expand_up(vma,addr) expand_upwards(vma, addr)
+#define vma_expand_down(vma, addr) (-EFAULT)
+
+#else
+
+#define vma_expand_up(vma,addr) (-EFAULT)
+#define vma_expand_down(vma, addr) expand_downwards(vma, addr)
+
+#endif
+
+/*
+ * expand_stack(): legacy interface for page faulting. Don't use unless
+ * you have to.
+ *
+ * This is called with the mm locked for reading, drops the lock, takes
+ * the lock for writing, tries to look up a vma again, expands it if
+ * necessary, and downgrades the lock to reading again.
+ *
+ * If no vma is found or it can't be expanded, it returns NULL and has
+ * dropped the lock.
+ */
+struct vm_area_struct *expand_stack(struct mm_struct *mm, unsigned long addr)
+{
+	struct vm_area_struct *vma, *prev;
+
+	mmap_read_unlock(mm);
+	if (mmap_write_lock_killable(mm))
+		return NULL;
+
+	vma = find_vma_prev(mm, addr, &prev);
+	if (vma && vma->vm_start <= addr)
+		goto success;
+
+	if (prev && !vma_expand_up(prev, addr)) {
+		vma = prev;
+		goto success;
+	}
+
+	if (vma && !vma_expand_down(vma, addr))
+		goto success;
+
+	mmap_write_unlock(mm);
+	return NULL;
+
+success:
+	mmap_write_downgrade(mm);
+	return vma;
+}
+
+/*
+ * Ok - we have the memory areas we should free on a maple tree so release them,
+ * and do the vma updates.
+ *
+ * Called with the mm semaphore held.
+ */
+static inline void remove_mt(struct mm_struct *mm, struct ma_state *mas)
+{
+	unsigned long nr_accounted = 0;
+	struct vm_area_struct *vma;
+
+	/* Update high watermark before we lower total_vm */
+	update_hiwater_vm(mm);
+	mas_for_each(mas, vma, ULONG_MAX) {
+		long nrpages = vma_pages(vma);
+
+		if (vma->vm_flags & VM_ACCOUNT)
+			nr_accounted += nrpages;
+		vm_stat_account(mm, vma->vm_flags, -nrpages);
+		remove_vma(vma);
+	}
+	vm_unacct_memory(nr_accounted);
+	validate_mm(mm);
+}
+
+/*
+ * Get rid of page table information in the indicated region.
+ *
+ * Called with the mm semaphore held.
+ */
+static void unmap_region(struct mm_struct *mm, struct maple_tree *mt,
+		struct vm_area_struct *vma, struct vm_area_struct *prev,
+		struct vm_area_struct *next,
+		unsigned long start, unsigned long end)
+{
+	struct mmu_gather tlb;
+
+	lru_add_drain();
+	tlb_gather_mmu(&tlb, mm);
+	update_hiwater_rss(mm);
+	unmap_vmas(&tlb, mt, vma, start, end);
+	free_pgtables(&tlb, mt, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
+				 next ? next->vm_start : USER_PGTABLES_CEILING);
+	tlb_finish_mmu(&tlb);
+}
+
+/*
+ * __split_vma() bypasses sysctl_max_map_count checking.  We use this where it
+ * has already been checked or doesn't make sense to fail.
+ */
+int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
+		unsigned long addr, int new_below)
+{
+	struct vm_area_struct *new;
+	int err;
+	validate_mm_mt(mm);
+
+	if (vma->vm_ops && vma->vm_ops->may_split) {
+		err = vma->vm_ops->may_split(vma, addr);
+		if (err)
+			return err;
+	}
+
+	new = vm_area_dup(vma);
+	if (!new)
+		return -ENOMEM;
+
+	if (new_below)
+		new->vm_end = addr;
+	else {
+		new->vm_start = addr;
+		new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
+	}
+
+	err = vma_dup_policy(vma, new);
+	if (err)
+		goto out_free_vma;
+
+	err = anon_vma_clone(new, vma);
+	if (err)
+		goto out_free_mpol;
+
+	if (new->vm_file)
+		get_file(new->vm_file);
+
+	if (new->vm_ops && new->vm_ops->open)
+		new->vm_ops->open(new);
+
+	if (new_below)
+		err = vma_adjust(vma, addr, vma->vm_end, vma->vm_pgoff +
+			((addr - new->vm_start) >> PAGE_SHIFT), new);
+	else
+		err = vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new);
+
+	/* Success. */
+	if (!err)
+		return 0;
+
+	/* Avoid vm accounting in close() operation */
+	new->vm_start = new->vm_end;
+	new->vm_pgoff = 0;
+	/* Clean everything up if vma_adjust failed. */
+	if (new->vm_ops && new->vm_ops->close)
+		new->vm_ops->close(new);
+	if (new->vm_file)
+		fput(new->vm_file);
+	unlink_anon_vmas(new);
+ out_free_mpol:
+	mpol_put(vma_policy(new));
+ out_free_vma:
+	vm_area_free(new);
+	validate_mm_mt(mm);
+	return err;
+}
+
+/*
+ * Split a vma into two pieces at address 'addr', a new vma is allocated
+ * either for the first part or the tail.
+ */
+int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
+	      unsigned long addr, int new_below)
+{
+	if (mm->map_count >= sysctl_max_map_count)
+		return -ENOMEM;
+
+	return __split_vma(mm, vma, addr, new_below);
+}
+
+/*
+ * do_mas_align_munmap() - munmap the aligned region from @start to @end.
+ * @mas: The maple_state, ideally set up to alter the correct tree location.
+ * @vma: The starting vm_area_struct
+ * @mm: The mm_struct
+ * @start: The aligned start address to munmap.
+ * @end: The aligned end address to munmap.
+ * @uf: The userfaultfd list_head
+ * @downgrade: Set to true to attempt a write downgrade of the mmap_sem
+ *
+ * If @downgrade is true, check return code for potential release of the lock.
+ */
+static int
+do_mas_align_munmap(struct ma_state *mas, struct vm_area_struct *vma,
+		    struct mm_struct *mm, unsigned long start,
+		    unsigned long end, struct list_head *uf, bool downgrade)
+{
+	struct vm_area_struct *prev, *next = NULL;
+	struct maple_tree mt_detach;
+	int count = 0;
+	int error = -ENOMEM;
+	unsigned long locked_vm = 0;
+	MA_STATE(mas_detach, &mt_detach, 0, 0);
+	mt_init_flags(&mt_detach, mas->tree->ma_flags & MT_FLAGS_LOCK_MASK);
+	mt_set_external_lock(&mt_detach, &mm->mmap_lock);
+
+	if (mas_preallocate(mas, vma, GFP_KERNEL))
+		return -ENOMEM;
+
+	mas->last = end - 1;
+	/*
+	 * If we need to split any vma, do it now to save pain later.
+	 *
+	 * Note: mremap's move_vma VM_ACCOUNT handling assumes a partially
+	 * unmapped vm_area_struct will remain in use: so lower split_vma
+	 * places tmp vma above, and higher split_vma places tmp vma below.
+	 */
+
+	/* Does it split the first one? */
+	if (start > vma->vm_start) {
+
+		/*
+		 * Make sure that map_count on return from munmap() will
+		 * not exceed its limit; but let map_count go just above
+		 * its limit temporarily, to help free resources as expected.
+		 */
+		if (end < vma->vm_end && mm->map_count >= sysctl_max_map_count)
+			goto map_count_exceeded;
+
+		/*
+		 * mas_pause() is not needed since mas->index needs to be set
+		 * differently than vma->vm_end anyways.
+		 */
+		error = __split_vma(mm, vma, start, 0);
+		if (error)
+			goto start_split_failed;
+
+		mas_set(mas, start);
+		vma = mas_walk(mas);
+	}
+
+	prev = mas_prev(mas, 0);
+	if (unlikely((!prev)))
+		mas_set(mas, start);
+
+	/*
+	 * Detach a range of VMAs from the mm. Using next as a temp variable as
+	 * it is always overwritten.
+	 */
+	mas_for_each(mas, next, end - 1) {
+		/* Does it split the end? */
+		if (next->vm_end > end) {
+			struct vm_area_struct *split;
+
+			error = __split_vma(mm, next, end, 1);
+			if (error)
+				goto end_split_failed;
+
+			mas_set(mas, end);
+			split = mas_prev(mas, 0);
+			mas_set_range(&mas_detach, split->vm_start, split->vm_end - 1);
+			error = mas_store_gfp(&mas_detach, split, GFP_KERNEL);
+			if (error)
+				goto munmap_gather_failed;
+			if (split->vm_flags & VM_LOCKED)
+				locked_vm += vma_pages(split);
+
+			count++;
+			if (vma == next)
+				vma = split;
+			break;
+		}
+		mas_set_range(&mas_detach, next->vm_start, next->vm_end - 1);
+		error = mas_store_gfp(&mas_detach, next, GFP_KERNEL);
+		if (error)
+			goto munmap_gather_failed;
+		if (next->vm_flags & VM_LOCKED)
+			locked_vm += vma_pages(next);
+
+		count++;
+#ifdef CONFIG_DEBUG_VM_MAPLE_TREE
+		BUG_ON(next->vm_start < start);
+		BUG_ON(next->vm_start > end);
+#endif
+	}
+
+	if (!next)
+		next = mas_next(mas, ULONG_MAX);
+
+	if (unlikely(uf)) {
+		/*
+		 * If userfaultfd_unmap_prep returns an error the vmas
+		 * will remain split, but userland will get a
+		 * highly unexpected error anyway. This is no
+		 * different than the case where the first of the two
+		 * __split_vma fails, but we don't undo the first
+		 * split, despite we could. This is unlikely enough
+		 * failure that it's not worth optimizing it for.
+		 */
+		error = userfaultfd_unmap_prep(mm, start, end, uf);
+
+		if (error)
+			goto userfaultfd_error;
+	}
+
+	/* Point of no return */
+	mas_set_range(mas, start, end - 1);
+#if defined(CONFIG_DEBUG_VM_MAPLE_TREE)
+	/* Make sure no VMAs are about to be lost. */
+	{
+		MA_STATE(test, &mt_detach, start, end - 1);
+		struct vm_area_struct *vma_mas, *vma_test;
+		int test_count = 0;
+
+		rcu_read_lock();
+		vma_test = mas_find(&test, end - 1);
+		mas_for_each(mas, vma_mas, end - 1) {
+			BUG_ON(vma_mas != vma_test);
+			test_count++;
+			vma_test = mas_next(&test, end - 1);
+		}
+		rcu_read_unlock();
+		BUG_ON(count != test_count);
+		mas_set_range(mas, start, end - 1);
+	}
+#endif
+	/* Point of no return */
+	mas_store_prealloc(mas, NULL);
+
+	mm->locked_vm -= locked_vm;
+	mm->map_count -= count;
+	/*
+	 * Do not downgrade mmap_lock if we are next to VM_GROWSDOWN or
+	 * VM_GROWSUP VMA. Such VMAs can change their size under
+	 * down_read(mmap_lock) and collide with the VMA we are about to unmap.
+	 */
+	if (downgrade) {
+		if (next && (next->vm_flags & VM_GROWSDOWN))
+			downgrade = false;
+		else if (prev && (prev->vm_flags & VM_GROWSUP))
+			downgrade = false;
+		else
+			mmap_write_downgrade(mm);
+	}
+
+	unmap_region(mm, &mt_detach, vma, prev, next, start, end);
+	/* Statistics and freeing VMAs */
+	mas_set(&mas_detach, start);
+	remove_mt(mm, &mas_detach);
+	__mt_destroy(&mt_detach);
+
+
+	validate_mm(mm);
+	return downgrade ? 1 : 0;
+
+userfaultfd_error:
+munmap_gather_failed:
+end_split_failed:
+	__mt_destroy(&mt_detach);
+start_split_failed:
+map_count_exceeded:
+	mas_destroy(mas);
+	return error;
+}
+
+/*
+ * do_mas_munmap() - munmap a given range.
+ * @mas: The maple state
+ * @mm: The mm_struct
+ * @start: The start address to munmap
+ * @len: The length of the range to munmap
+ * @uf: The userfaultfd list_head
+ * @downgrade: set to true if the user wants to attempt to write_downgrade the
+ * mmap_sem
+ *
+ * This function takes a @mas that is either pointing to the previous VMA or set
+ * to MA_START and sets it up to remove the mapping(s).  The @len will be
+ * aligned and any arch_unmap work will be preformed.
+ *
+ * Returns: -EINVAL on failure, 1 on success and unlock, 0 otherwise.
+ */
+int do_mas_munmap(struct ma_state *mas, struct mm_struct *mm,
+		  unsigned long start, size_t len, struct list_head *uf,
+		  bool downgrade)
+{
+	unsigned long end;
+	struct vm_area_struct *vma;
+
+	if ((offset_in_page(start)) || start > TASK_SIZE || len > TASK_SIZE-start)
+		return -EINVAL;
+
+	end = start + PAGE_ALIGN(len);
+	if (end == start)
+		return -EINVAL;
+
+	 /* arch_unmap() might do unmaps itself.  */
+	arch_unmap(mm, start, end);
+
+	/* Find the first overlapping VMA */
+	vma = mas_find(mas, end - 1);
+	if (!vma)
+		return 0;
+
+	return do_mas_align_munmap(mas, vma, mm, start, end, uf, downgrade);
+}
+
+/* do_munmap() - Wrapper function for non-maple tree aware do_munmap() calls.
+ * @mm: The mm_struct
+ * @start: The start address to munmap
+ * @len: The length to be munmapped.
+ * @uf: The userfaultfd list_head
+ */
+int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
+	      struct list_head *uf)
+{
+	MA_STATE(mas, &mm->mm_mt, start, start);
+
+	return do_mas_munmap(&mas, mm, start, len, uf, false);
+}
+
+unsigned long mmap_region(struct file *file, unsigned long addr,
+		unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
+		struct list_head *uf)
+{
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma = NULL;
+	struct vm_area_struct *next, *prev, *merge;
+	pgoff_t pglen = len >> PAGE_SHIFT;
+	unsigned long charged = 0;
+	unsigned long end = addr + len;
+	unsigned long merge_start = addr, merge_end = end;
+	pgoff_t vm_pgoff;
+	int error;
+	MA_STATE(mas, &mm->mm_mt, addr, end - 1);
+
+	/* Check against address space limit. */
+	if (!may_expand_vm(mm, vm_flags, len >> PAGE_SHIFT)) {
+		unsigned long nr_pages;
+
+		/*
+		 * MAP_FIXED may remove pages of mappings that intersects with
+		 * requested mapping. Account for the pages it would unmap.
+		 */
+		nr_pages = count_vma_pages_range(mm, addr, end);
+
+		if (!may_expand_vm(mm, vm_flags,
+					(len >> PAGE_SHIFT) - nr_pages))
+			return -ENOMEM;
+	}
+
+	/* Unmap any existing mapping in the area */
+	if (do_mas_munmap(&mas, mm, addr, len, uf, false))
+		return -ENOMEM;
+
+	/*
+	 * Private writable mapping: check memory availability
+	 */
+	if (accountable_mapping(file, vm_flags)) {
+		charged = len >> PAGE_SHIFT;
+		if (security_vm_enough_memory_mm(mm, charged))
+			return -ENOMEM;
+		vm_flags |= VM_ACCOUNT;
+	}
+
+	next = mas_next(&mas, ULONG_MAX);
+	prev = mas_prev(&mas, 0);
+	if (vm_flags & VM_SPECIAL)
+		goto cannot_expand;
+
+	/* Attempt to expand an old mapping */
+	/* Check next */
+	if (next && next->vm_start == end && !vma_policy(next) &&
+	    can_vma_merge_before(next, vm_flags, NULL, file, pgoff+pglen,
+				 NULL_VM_UFFD_CTX, NULL)) {
+		merge_end = next->vm_end;
+		vma = next;
+		vm_pgoff = next->vm_pgoff - pglen;
+	}
+
+	/* Check prev */
+	if (prev && prev->vm_end == addr && !vma_policy(prev) &&
+	    (vma ? can_vma_merge_after(prev, vm_flags, vma->anon_vma, file,
+				       pgoff, vma->vm_userfaultfd_ctx, NULL) :
+		   can_vma_merge_after(prev, vm_flags, NULL, file, pgoff,
+				       NULL_VM_UFFD_CTX, NULL))) {
+		merge_start = prev->vm_start;
+		vma = prev;
+		vm_pgoff = prev->vm_pgoff;
+	}
+
+
+	/* Actually expand, if possible */
+	if (vma &&
+	    !vma_expand(&mas, vma, merge_start, merge_end, vm_pgoff, next)) {
+		khugepaged_enter_vma(vma, vm_flags);
+		goto expanded;
+	}
+
+	mas.index = addr;
+	mas.last = end - 1;
+cannot_expand:
+	/*
+	 * Determine the object being mapped and call the appropriate
+	 * specific mapper. the address has already been validated, but
+	 * not unmapped, but the maps are removed from the list.
+	 */
+	vma = vm_area_alloc(mm);
+	if (!vma) {
+		error = -ENOMEM;
+		goto unacct_error;
+	}
+
+	vma->vm_start = addr;
+	vma->vm_end = end;
+	vma->vm_flags = vm_flags;
+	vma->vm_page_prot = vm_get_page_prot(vm_flags);
+	vma->vm_pgoff = pgoff;
+
+	if (file) {
+		if (vm_flags & VM_SHARED) {
+			error = mapping_map_writable(file->f_mapping);
+			if (error)
+				goto free_vma;
+		}
+
+		vma->vm_file = get_file(file);
+		error = call_mmap(file, vma);
+		if (error)
+			goto unmap_and_free_vma;
+
+		/*
+		 * Expansion is handled above, merging is handled below.
+		 * Drivers should not alter the address of the VMA.
+		 */
+		if (WARN_ON((addr != vma->vm_start))) {
+			error = -EINVAL;
+			goto close_and_free_vma;
+		}
+		mas_reset(&mas);
+
+		/*
+		 * If vm_flags changed after call_mmap(), we should try merge
+		 * vma again as we may succeed this time.
+		 */
+		if (unlikely(vm_flags != vma->vm_flags && prev)) {
+			merge = vma_merge(mm, prev, vma->vm_start, vma->vm_end, vma->vm_flags,
+				NULL, vma->vm_file, vma->vm_pgoff, NULL, NULL_VM_UFFD_CTX, NULL);
+			if (merge) {
+				/*
+				 * ->mmap() can change vma->vm_file and fput
+				 * the original file. So fput the vma->vm_file
+				 * here or we would add an extra fput for file
+				 * and cause general protection fault
+				 * ultimately.
+				 */
+				fput(vma->vm_file);
+				vm_area_free(vma);
+				vma = merge;
+				/* Update vm_flags to pick up the change. */
+				vm_flags = vma->vm_flags;
+				goto unmap_writable;
+			}
+		}
+
+		vm_flags = vma->vm_flags;
+	} else if (vm_flags & VM_SHARED) {
+		error = shmem_zero_setup(vma);
+		if (error)
+			goto free_vma;
+	} else {
+		vma_set_anonymous(vma);
+	}
+
+	/* Allow architectures to sanity-check the vm_flags */
+	if (!arch_validate_flags(vma->vm_flags)) {
+		error = -EINVAL;
+		if (file)
+			goto close_and_free_vma;
+		else if (vma->vm_file)
+			goto unmap_and_free_vma;
+		else
+			goto free_vma;
+	}
+
+	if (mas_preallocate(&mas, vma, GFP_KERNEL)) {
+		error = -ENOMEM;
+		if (file)
+			goto close_and_free_vma;
+		else if (vma->vm_file)
+			goto unmap_and_free_vma;
+		else
+			goto free_vma;
+	}
+
+	if (vma->vm_file)
+		i_mmap_lock_write(vma->vm_file->f_mapping);
+
+	vma_mas_store(vma, &mas);
+	mm->map_count++;
+	if (vma->vm_file) {
+		if (vma->vm_flags & VM_SHARED)
+			mapping_allow_writable(vma->vm_file->f_mapping);
+
+		flush_dcache_mmap_lock(vma->vm_file->f_mapping);
+		vma_interval_tree_insert(vma, &vma->vm_file->f_mapping->i_mmap);
+		flush_dcache_mmap_unlock(vma->vm_file->f_mapping);
+		i_mmap_unlock_write(vma->vm_file->f_mapping);
+	}
+
+	/*
+	 * vma_merge() calls khugepaged_enter_vma() either, the below
+	 * call covers the non-merge case.
+	 */
+	khugepaged_enter_vma(vma, vma->vm_flags);
+
+	/* Once vma denies write, undo our temporary denial count */
+unmap_writable:
+	if (file && vm_flags & VM_SHARED)
+		mapping_unmap_writable(file->f_mapping);
+	file = vma->vm_file;
+expanded:
+	perf_event_mmap(vma);
+
+	vm_stat_account(mm, vm_flags, len >> PAGE_SHIFT);
+	if (vm_flags & VM_LOCKED) {
+		if ((vm_flags & VM_SPECIAL) || vma_is_dax(vma) ||
+					is_vm_hugetlb_page(vma) ||
+					vma == get_gate_vma(current->mm))
+			vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
+		else
+			mm->locked_vm += (len >> PAGE_SHIFT);
+	}
+
+	if (file)
+		uprobe_mmap(vma);
+
+	/*
+	 * New (or expanded) vma always get soft dirty status.
+	 * Otherwise user-space soft-dirty page tracker won't
+	 * be able to distinguish situation when vma area unmapped,
+	 * then new mapped in-place (which must be aimed as
+	 * a completely new data area).
+	 */
+	vma->vm_flags |= VM_SOFTDIRTY;
+
+	vma_set_page_prot(vma);
+
+	validate_mm(mm);
+	return addr;
+
+close_and_free_vma:
+	if (vma->vm_ops && vma->vm_ops->close)
+		vma->vm_ops->close(vma);
+unmap_and_free_vma:
+	fput(vma->vm_file);
+	vma->vm_file = NULL;
+
+	/* Undo any partial mapping done by a device driver. */
+	unmap_region(mm, mas.tree, vma, prev, next, vma->vm_start, vma->vm_end);
+	if (file && (vm_flags & VM_SHARED))
+		mapping_unmap_writable(file->f_mapping);
+free_vma:
+	vm_area_free(vma);
+unacct_error:
+	if (charged)
+		vm_unacct_memory(charged);
+	validate_mm(mm);
+	return error;
+}
+
+static int __vm_munmap(unsigned long start, size_t len, bool downgrade)
+{
+	int ret;
+	struct mm_struct *mm = current->mm;
+	LIST_HEAD(uf);
+	MA_STATE(mas, &mm->mm_mt, start, start);
+
+	if (mmap_write_lock_killable(mm))
+		return -EINTR;
+
+	ret = do_mas_munmap(&mas, mm, start, len, &uf, downgrade);
+	/*
+	 * Returning 1 indicates mmap_lock is downgraded.
+	 * But 1 is not legal return value of vm_munmap() and munmap(), reset
+	 * it to 0 before return.
+	 */
+	if (ret == 1) {
+		mmap_read_unlock(mm);
+		ret = 0;
+	} else
+		mmap_write_unlock(mm);
+
+	userfaultfd_unmap_complete(mm, &uf);
+	return ret;
+}
+
+int vm_munmap(unsigned long start, size_t len)
+{
+	return __vm_munmap(start, len, false);
+}
+EXPORT_SYMBOL(vm_munmap);
+
+SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
+{
+	addr = untagged_addr(addr);
+	return __vm_munmap(addr, len, true);
+}
+
+
+/*
+ * Emulation of deprecated remap_file_pages() syscall.
+ */
+SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
+		unsigned long, prot, unsigned long, pgoff, unsigned long, flags)
+{
+
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
+	unsigned long populate = 0;
+	unsigned long ret = -EINVAL;
+	struct file *file;
+
+	pr_warn_once("%s (%d) uses deprecated remap_file_pages() syscall. See Documentation/mm/remap_file_pages.rst.\n",
+		     current->comm, current->pid);
+
+	if (prot)
+		return ret;
+	start = start & PAGE_MASK;
+	size = size & PAGE_MASK;
+
+	if (start + size <= start)
+		return ret;
+
+	/* Does pgoff wrap? */
+	if (pgoff + (size >> PAGE_SHIFT) < pgoff)
+		return ret;
+
+	if (mmap_write_lock_killable(mm))
+		return -EINTR;
+
+	vma = vma_lookup(mm, start);
+
+	if (!vma || !(vma->vm_flags & VM_SHARED))
+		goto out;
+
+	if (start + size > vma->vm_end) {
+		VMA_ITERATOR(vmi, mm, vma->vm_end);
+		struct vm_area_struct *next, *prev = vma;
+
+		for_each_vma_range(vmi, next, start + size) {
+			/* hole between vmas ? */
+			if (next->vm_start != prev->vm_end)
+				goto out;
+
+			if (next->vm_file != vma->vm_file)
+				goto out;
+
+			if (next->vm_flags != vma->vm_flags)
+				goto out;
+
+			if (start + size <= next->vm_end)
+				break;
+
+			prev = next;
+		}
+
+		if (!next)
+			goto out;
+	}
+
+	prot |= vma->vm_flags & VM_READ ? PROT_READ : 0;
+	prot |= vma->vm_flags & VM_WRITE ? PROT_WRITE : 0;
+	prot |= vma->vm_flags & VM_EXEC ? PROT_EXEC : 0;
+
+	flags &= MAP_NONBLOCK;
+	flags |= MAP_SHARED | MAP_FIXED | MAP_POPULATE;
+	if (vma->vm_flags & VM_LOCKED)
+		flags |= MAP_LOCKED;
+
+	file = get_file(vma->vm_file);
+	ret = do_mmap(vma->vm_file, start, size,
+			prot, flags, pgoff, &populate, NULL);
+	fput(file);
+out:
+	mmap_write_unlock(mm);
+	if (populate)
+		mm_populate(ret, populate);
+	if (!IS_ERR_VALUE(ret))
+		ret = 0;
+	return ret;
+}
+
+/*
+ * brk_munmap() - Unmap a parital vma.
+ * @mas: The maple tree state.
+ * @vma: The vma to be modified
+ * @newbrk: the start of the address to unmap
+ * @oldbrk: The end of the address to unmap
+ * @uf: The userfaultfd list_head
+ *
+ * Returns: 1 on success.
+ * unmaps a partial VMA mapping.  Does not handle alignment, downgrades lock if
+ * possible.
+ */
+static int do_brk_munmap(struct ma_state *mas, struct vm_area_struct *vma,
+			 unsigned long newbrk, unsigned long oldbrk,
+			 struct list_head *uf)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	int ret;
+
+	arch_unmap(mm, newbrk, oldbrk);
+	ret = do_mas_align_munmap(mas, vma, mm, newbrk, oldbrk, uf, true);
+	validate_mm_mt(mm);
+	return ret;
+}
+
+/*
+ * do_brk_flags() - Increase the brk vma if the flags match.
+ * @mas: The maple tree state.
+ * @addr: The start address
+ * @len: The length of the increase
+ * @vma: The vma,
+ * @flags: The VMA Flags
+ *
+ * Extend the brk VMA from addr to addr + len.  If the VMA is NULL or the flags
+ * do not match then create a new anonymous VMA.  Eventually we may be able to
+ * do some brk-specific accounting here.
+ */
+static int do_brk_flags(struct ma_state *mas, struct vm_area_struct *vma,
+		unsigned long addr, unsigned long len, unsigned long flags)
+{
+	struct mm_struct *mm = current->mm;
+
+	validate_mm_mt(mm);
+	/*
+	 * Check against address space limits by the changed size
+	 * Note: This happens *after* clearing old mappings in some code paths.
+	 */
+	flags |= VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
+	if (!may_expand_vm(mm, flags, len >> PAGE_SHIFT))
+		return -ENOMEM;
+
+	if (mm->map_count > sysctl_max_map_count)
+		return -ENOMEM;
+
+	if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT))
+		return -ENOMEM;
+
+	/*
+	 * Expand the existing vma if possible; Note that singular lists do not
+	 * occur after forking, so the expand will only happen on new VMAs.
+	 */
+	if (vma && vma->vm_end == addr && !vma_policy(vma) &&
+	    can_vma_merge_after(vma, flags, NULL, NULL,
+				addr >> PAGE_SHIFT, NULL_VM_UFFD_CTX, NULL)) {
+		mas_set_range(mas, vma->vm_start, addr + len - 1);
+		if (mas_preallocate(mas, vma, GFP_KERNEL))
+			return -ENOMEM;
+
+		vma_adjust_trans_huge(vma, vma->vm_start, addr + len, 0);
+		if (vma->anon_vma) {
+			anon_vma_lock_write(vma->anon_vma);
+			anon_vma_interval_tree_pre_update_vma(vma);
+		}
+		vma->vm_end = addr + len;
+		vma->vm_flags |= VM_SOFTDIRTY;
+		mas_store_prealloc(mas, vma);
+
+		if (vma->anon_vma) {
+			anon_vma_interval_tree_post_update_vma(vma);
+			anon_vma_unlock_write(vma->anon_vma);
+		}
+		khugepaged_enter_vma(vma, flags);
+		goto out;
+	}
+
+	/* create a vma struct for an anonymous mapping */
+	vma = vm_area_alloc(mm);
+	if (!vma)
+		goto vma_alloc_fail;
+
+	vma_set_anonymous(vma);
+	vma->vm_start = addr;
+	vma->vm_end = addr + len;
+	vma->vm_pgoff = addr >> PAGE_SHIFT;
+	vma->vm_flags = flags;
+	vma->vm_page_prot = vm_get_page_prot(flags);
+	mas_set_range(mas, vma->vm_start, addr + len - 1);
+	if (mas_store_gfp(mas, vma, GFP_KERNEL))
+		goto mas_store_fail;
+
+	mm->map_count++;
+out:
+	perf_event_mmap(vma);
+	mm->total_vm += len >> PAGE_SHIFT;
+	mm->data_vm += len >> PAGE_SHIFT;
+	if (flags & VM_LOCKED)
+		mm->locked_vm += (len >> PAGE_SHIFT);
+	vma->vm_flags |= VM_SOFTDIRTY;
+	validate_mm(mm);
+	return 0;
+
+mas_store_fail:
+	vm_area_free(vma);
+vma_alloc_fail:
+	vm_unacct_memory(len >> PAGE_SHIFT);
+	return -ENOMEM;
+}
+
+int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags)
+{
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma = NULL;
+	unsigned long len;
+	int ret;
+	bool populate;
+	LIST_HEAD(uf);
+	MA_STATE(mas, &mm->mm_mt, addr, addr);
+
+	len = PAGE_ALIGN(request);
+	if (len < request)
+		return -ENOMEM;
+	if (!len)
+		return 0;
+
+	/* Until we need other flags, refuse anything except VM_EXEC. */
+	if ((flags & (~VM_EXEC)) != 0)
+		return -EINVAL;
+
+	if (mmap_write_lock_killable(mm))
+		return -EINTR;
+
+	ret = check_brk_limits(addr, len);
+	if (ret)
+		goto limits_failed;
+
+	ret = do_mas_munmap(&mas, mm, addr, len, &uf, 0);
+	if (ret)
+		goto munmap_failed;
+
+	vma = mas_prev(&mas, 0);
+	ret = do_brk_flags(&mas, vma, addr, len, flags);
+	populate = ((mm->def_flags & VM_LOCKED) != 0);
+	mmap_write_unlock(mm);
+	userfaultfd_unmap_complete(mm, &uf);
+	if (populate && !ret)
+		mm_populate(addr, len);
+	return ret;
+
+munmap_failed:
+limits_failed:
+	mmap_write_unlock(mm);
+	return ret;
+}
+EXPORT_SYMBOL(vm_brk_flags);
+
+int vm_brk(unsigned long addr, unsigned long len)
+{
+	return vm_brk_flags(addr, len, 0);
+}
+EXPORT_SYMBOL(vm_brk);
+
+/* Release all mmaps. */
+void exit_mmap(struct mm_struct *mm)
+{
+	struct mmu_gather tlb;
+	struct vm_area_struct *vma;
+	unsigned long nr_accounted = 0;
+	MA_STATE(mas, &mm->mm_mt, 0, 0);
+	int count = 0;
+
+	/* mm's last user has gone, and its about to be pulled down */
+	mmu_notifier_release(mm);
+
+	mmap_read_lock(mm);
+	arch_exit_mmap(mm);
+
+	vma = mas_find(&mas, ULONG_MAX);
+	if (!vma) {
+		/* Can happen if dup_mmap() received an OOM */
+		mmap_read_unlock(mm);
+		return;
+	}
+
+	lru_add_drain();
+	flush_cache_mm(mm);
+	tlb_gather_mmu_fullmm(&tlb, mm);
+	/* update_hiwater_rss(mm) here? but nobody should be looking */
+	/* Use ULONG_MAX here to ensure all VMAs in the mm are unmapped */
+	unmap_vmas(&tlb, &mm->mm_mt, vma, 0, ULONG_MAX);
+	mmap_read_unlock(mm);
+
+	/*
+	 * Set MMF_OOM_SKIP to hide this task from the oom killer/reaper
+	 * because the memory has been already freed.
+	 */
+	set_bit(MMF_OOM_SKIP, &mm->flags);
+	mmap_write_lock(mm);
+	mt_clear_in_rcu(&mm->mm_mt);
+	free_pgtables(&tlb, &mm->mm_mt, vma, FIRST_USER_ADDRESS,
+		      USER_PGTABLES_CEILING);
+	tlb_finish_mmu(&tlb);
+
+	/*
+	 * Walk the list again, actually closing and freeing it, with preemption
+	 * enabled, without holding any MM locks besides the unreachable
+	 * mmap_write_lock.
+	 */
+	do {
+		if (vma->vm_flags & VM_ACCOUNT)
+			nr_accounted += vma_pages(vma);
+		remove_vma(vma);
+		count++;
+		cond_resched();
+	} while ((vma = mas_find(&mas, ULONG_MAX)) != NULL);
+
+	BUG_ON(count != mm->map_count);
+
+	trace_exit_mmap(mm);
+	__mt_destroy(&mm->mm_mt);
+	mmap_write_unlock(mm);
+	vm_unacct_memory(nr_accounted);
+}
+
+/* Insert vm structure into process list sorted by address
+ * and into the inode's i_mmap tree.  If vm_file is non-NULL
+ * then i_mmap_rwsem is taken here.
+ */
+int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
+{
+	unsigned long charged = vma_pages(vma);
+
+
+	if (find_vma_intersection(mm, vma->vm_start, vma->vm_end))
+		return -ENOMEM;
+
+	if ((vma->vm_flags & VM_ACCOUNT) &&
+	     security_vm_enough_memory_mm(mm, charged))
+		return -ENOMEM;
+
+	/*
+	 * The vm_pgoff of a purely anonymous vma should be irrelevant
+	 * until its first write fault, when page's anon_vma and index
+	 * are set.  But now set the vm_pgoff it will almost certainly
+	 * end up with (unless mremap moves it elsewhere before that
+	 * first wfault), so /proc/pid/maps tells a consistent story.
+	 *
+	 * By setting it to reflect the virtual start address of the
+	 * vma, merges and splits can happen in a seamless way, just
+	 * using the existing file pgoff checks and manipulations.
+	 * Similarly in do_mmap and in do_brk_flags.
+	 */
+	if (vma_is_anonymous(vma)) {
+		BUG_ON(vma->anon_vma);
+		vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
+	}
+
+	if (vma_link(mm, vma)) {
+		vm_unacct_memory(charged);
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+/*
+ * Copy the vma structure to a new location in the same mm,
+ * prior to moving page table entries, to effect an mremap move.
+ */
+struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
+	unsigned long addr, unsigned long len, pgoff_t pgoff,
+	bool *need_rmap_locks)
+{
+	struct vm_area_struct *vma = *vmap;
+	unsigned long vma_start = vma->vm_start;
+	struct mm_struct *mm = vma->vm_mm;
+	struct vm_area_struct *new_vma, *prev;
+	bool faulted_in_anon_vma = true;
+
+	validate_mm_mt(mm);
+	/*
+	 * If anonymous vma has not yet been faulted, update new pgoff
+	 * to match new location, to increase its chance of merging.
+	 */
+	if (unlikely(vma_is_anonymous(vma) && !vma->anon_vma)) {
+		pgoff = addr >> PAGE_SHIFT;
+		faulted_in_anon_vma = false;
+	}
+
+	new_vma = find_vma_prev(mm, addr, &prev);
+	if (new_vma && new_vma->vm_start < addr + len)
+		return NULL;	/* should never get here */
+
+	new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
+			    vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
+			    vma->vm_userfaultfd_ctx, anon_vma_name(vma));
+	if (new_vma) {
+		/*
+		 * Source vma may have been merged into new_vma
+		 */
+		if (unlikely(vma_start >= new_vma->vm_start &&
+			     vma_start < new_vma->vm_end)) {
+			/*
+			 * The only way we can get a vma_merge with
+			 * self during an mremap is if the vma hasn't
+			 * been faulted in yet and we were allowed to
+			 * reset the dst vma->vm_pgoff to the
+			 * destination address of the mremap to allow
+			 * the merge to happen. mremap must change the
+			 * vm_pgoff linearity between src and dst vmas
+			 * (in turn preventing a vma_merge) to be
+			 * safe. It is only safe to keep the vm_pgoff
+			 * linear if there are no pages mapped yet.
+			 */
+			VM_BUG_ON_VMA(faulted_in_anon_vma, new_vma);
+			*vmap = vma = new_vma;
+		}
+		*need_rmap_locks = (new_vma->vm_pgoff <= vma->vm_pgoff);
+	} else {
+		new_vma = vm_area_dup(vma);
+		if (!new_vma)
+			goto out;
+		new_vma->vm_start = addr;
+		new_vma->vm_end = addr + len;
+		new_vma->vm_pgoff = pgoff;
+		if (vma_dup_policy(vma, new_vma))
+			goto out_free_vma;
+		if (anon_vma_clone(new_vma, vma))
+			goto out_free_mempol;
+		if (new_vma->vm_file)
+			get_file(new_vma->vm_file);
+		if (new_vma->vm_ops && new_vma->vm_ops->open)
+			new_vma->vm_ops->open(new_vma);
+		if (vma_link(mm, new_vma))
+			goto out_vma_link;
+		*need_rmap_locks = false;
+	}
+	validate_mm_mt(mm);
+	return new_vma;
+
+out_vma_link:
+	if (new_vma->vm_ops && new_vma->vm_ops->close)
+		new_vma->vm_ops->close(new_vma);
+
+	if (new_vma->vm_file)
+		fput(new_vma->vm_file);
+
+	unlink_anon_vmas(new_vma);
+out_free_mempol:
+	mpol_put(vma_policy(new_vma));
+out_free_vma:
+	vm_area_free(new_vma);
+out:
+	validate_mm_mt(mm);
+	return NULL;
+}
+
+/*
+ * Return true if the calling process may expand its vm space by the passed
+ * number of pages
+ */
+bool may_expand_vm(struct mm_struct *mm, vm_flags_t flags, unsigned long npages)
+{
+	if (mm->total_vm + npages > rlimit(RLIMIT_AS) >> PAGE_SHIFT)
+		return false;
+
+	if (is_data_mapping(flags) &&
+	    mm->data_vm + npages > rlimit(RLIMIT_DATA) >> PAGE_SHIFT) {
+		/* Workaround for Valgrind */
+		if (rlimit(RLIMIT_DATA) == 0 &&
+		    mm->data_vm + npages <= rlimit_max(RLIMIT_DATA) >> PAGE_SHIFT)
+			return true;
+
+		pr_warn_once("%s (%d): VmData %lu exceed data ulimit %lu. Update limits%s.\n",
+			     current->comm, current->pid,
+			     (mm->data_vm + npages) << PAGE_SHIFT,
+			     rlimit(RLIMIT_DATA),
+			     ignore_rlimit_data ? "" : " or use boot option ignore_rlimit_data");
+
+		if (!ignore_rlimit_data)
+			return false;
+	}
+
+	return true;
+}
+
+void vm_stat_account(struct mm_struct *mm, vm_flags_t flags, long npages)
+{
+	WRITE_ONCE(mm->total_vm, READ_ONCE(mm->total_vm)+npages);
+
+	if (is_exec_mapping(flags))
+		mm->exec_vm += npages;
+	else if (is_stack_mapping(flags))
+		mm->stack_vm += npages;
+	else if (is_data_mapping(flags))
+		mm->data_vm += npages;
+}
+
+static vm_fault_t special_mapping_fault(struct vm_fault *vmf);
+
+/*
+ * Having a close hook prevents vma merging regardless of flags.
+ */
+static void special_mapping_close(struct vm_area_struct *vma)
+{
+}
+
+static const char *special_mapping_name(struct vm_area_struct *vma)
+{
+	return ((struct vm_special_mapping *)vma->vm_private_data)->name;
+}
+
+static int special_mapping_mremap(struct vm_area_struct *new_vma)
+{
+	struct vm_special_mapping *sm = new_vma->vm_private_data;
+
+	if (WARN_ON_ONCE(current->mm != new_vma->vm_mm))
+		return -EFAULT;
+
+	if (sm->mremap)
+		return sm->mremap(sm, new_vma);
+
+	return 0;
+}
+
+static int special_mapping_split(struct vm_area_struct *vma, unsigned long addr)
+{
+	/*
+	 * Forbid splitting special mappings - kernel has expectations over
+	 * the number of pages in mapping. Together with VM_DONTEXPAND
+	 * the size of vma should stay the same over the special mapping's
+	 * lifetime.
+	 */
+	return -EINVAL;
+}
+
+static const struct vm_operations_struct special_mapping_vmops = {
+	.close = special_mapping_close,
+	.fault = special_mapping_fault,
+	.mremap = special_mapping_mremap,
+	.name = special_mapping_name,
+	/* vDSO code relies that VVAR can't be accessed remotely */
+	.access = NULL,
+	.may_split = special_mapping_split,
+};
+
+static const struct vm_operations_struct legacy_special_mapping_vmops = {
+	.close = special_mapping_close,
+	.fault = special_mapping_fault,
+};
+
+static vm_fault_t special_mapping_fault(struct vm_fault *vmf)
+{
+	struct vm_area_struct *vma = vmf->vma;
+	pgoff_t pgoff;
+	struct page **pages;
+
+	if (vma->vm_ops == &legacy_special_mapping_vmops) {
+		pages = vma->vm_private_data;
+	} else {
+		struct vm_special_mapping *sm = vma->vm_private_data;
+
+		if (sm->fault)
+			return sm->fault(sm, vmf->vma, vmf);
+
+		pages = sm->pages;
+	}
+
+	for (pgoff = vmf->pgoff; pgoff && *pages; ++pages)
+		pgoff--;
+
+	if (*pages) {
+		struct page *page = *pages;
+		get_page(page);
+		vmf->page = page;
+		return 0;
+	}
+
+	return VM_FAULT_SIGBUS;
+}
+
+static struct vm_area_struct *__install_special_mapping(
+	struct mm_struct *mm,
+	unsigned long addr, unsigned long len,
+	unsigned long vm_flags, void *priv,
+	const struct vm_operations_struct *ops)
+{
+	int ret;
+	struct vm_area_struct *vma;
+
+	validate_mm_mt(mm);
+	vma = vm_area_alloc(mm);
+	if (unlikely(vma == NULL))
+		return ERR_PTR(-ENOMEM);
+
+	vma->vm_start = addr;
+	vma->vm_end = addr + len;
+
+	vma->vm_flags = vm_flags | mm->def_flags | VM_DONTEXPAND | VM_SOFTDIRTY;
+	vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
+	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
+
+	vma->vm_ops = ops;
+	vma->vm_private_data = priv;
+
+	ret = insert_vm_struct(mm, vma);
+	if (ret)
+		goto out;
+
+	vm_stat_account(mm, vma->vm_flags, len >> PAGE_SHIFT);
+
+	perf_event_mmap(vma);
+
+	validate_mm_mt(mm);
+	return vma;
+
+out:
+	vm_area_free(vma);
+	validate_mm_mt(mm);
+	return ERR_PTR(ret);
+}
+
+bool vma_is_special_mapping(const struct vm_area_struct *vma,
+	const struct vm_special_mapping *sm)
+{
+	return vma->vm_private_data == sm &&
+		(vma->vm_ops == &special_mapping_vmops ||
+		 vma->vm_ops == &legacy_special_mapping_vmops);
+}
+
+/*
+ * Called with mm->mmap_lock held for writing.
+ * Insert a new vma covering the given region, with the given flags.
+ * Its pages are supplied by the given array of struct page *.
+ * The array can be shorter than len >> PAGE_SHIFT if it's null-terminated.
+ * The region past the last page supplied will always produce SIGBUS.
+ * The array pointer and the pages it points to are assumed to stay alive
+ * for as long as this mapping might exist.
+ */
+struct vm_area_struct *_install_special_mapping(
+	struct mm_struct *mm,
+	unsigned long addr, unsigned long len,
+	unsigned long vm_flags, const struct vm_special_mapping *spec)
+{
+	return __install_special_mapping(mm, addr, len, vm_flags, (void *)spec,
+					&special_mapping_vmops);
+}
+
+int install_special_mapping(struct mm_struct *mm,
+			    unsigned long addr, unsigned long len,
+			    unsigned long vm_flags, struct page **pages)
+{
+	struct vm_area_struct *vma = __install_special_mapping(
+		mm, addr, len, vm_flags, (void *)pages,
+		&legacy_special_mapping_vmops);
+
+	return PTR_ERR_OR_ZERO(vma);
+}
+
+static DEFINE_MUTEX(mm_all_locks_mutex);
+
+static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma)
+{
+	if (!test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_root.rb_node)) {
+		/*
+		 * The LSB of head.next can't change from under us
+		 * because we hold the mm_all_locks_mutex.
+		 */
+		down_write_nest_lock(&anon_vma->root->rwsem, &mm->mmap_lock);
+		/*
+		 * We can safely modify head.next after taking the
+		 * anon_vma->root->rwsem. If some other vma in this mm shares
+		 * the same anon_vma we won't take it again.
+		 *
+		 * No need of atomic instructions here, head.next
+		 * can't change from under us thanks to the
+		 * anon_vma->root->rwsem.
+		 */
+		if (__test_and_set_bit(0, (unsigned long *)
+				       &anon_vma->root->rb_root.rb_root.rb_node))
+			BUG();
+	}
+}
+
+static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping)
+{
+	if (!test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
+		/*
+		 * AS_MM_ALL_LOCKS can't change from under us because
+		 * we hold the mm_all_locks_mutex.
+		 *
+		 * Operations on ->flags have to be atomic because
+		 * even if AS_MM_ALL_LOCKS is stable thanks to the
+		 * mm_all_locks_mutex, there may be other cpus
+		 * changing other bitflags in parallel to us.
+		 */
+		if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags))
+			BUG();
+		down_write_nest_lock(&mapping->i_mmap_rwsem, &mm->mmap_lock);
+	}
+}
+
+/*
+ * This operation locks against the VM for all pte/vma/mm related
+ * operations that could ever happen on a certain mm. This includes
+ * vmtruncate, try_to_unmap, and all page faults.
+ *
+ * The caller must take the mmap_lock in write mode before calling
+ * mm_take_all_locks(). The caller isn't allowed to release the
+ * mmap_lock until mm_drop_all_locks() returns.
+ *
+ * mmap_lock in write mode is required in order to block all operations
+ * that could modify pagetables and free pages without need of
+ * altering the vma layout. It's also needed in write mode to avoid new
+ * anon_vmas to be associated with existing vmas.
+ *
+ * A single task can't take more than one mm_take_all_locks() in a row
+ * or it would deadlock.
+ *
+ * The LSB in anon_vma->rb_root.rb_node and the AS_MM_ALL_LOCKS bitflag in
+ * mapping->flags avoid to take the same lock twice, if more than one
+ * vma in this mm is backed by the same anon_vma or address_space.
+ *
+ * We take locks in following order, accordingly to comment at beginning
+ * of mm/rmap.c:
+ *   - all hugetlbfs_i_mmap_rwsem_key locks (aka mapping->i_mmap_rwsem for
+ *     hugetlb mapping);
+ *   - all i_mmap_rwsem locks;
+ *   - all anon_vma->rwseml
+ *
+ * We can take all locks within these types randomly because the VM code
+ * doesn't nest them and we protected from parallel mm_take_all_locks() by
+ * mm_all_locks_mutex.
+ *
+ * mm_take_all_locks() and mm_drop_all_locks are expensive operations
+ * that may have to take thousand of locks.
+ *
+ * mm_take_all_locks() can fail if it's interrupted by signals.
+ */
+int mm_take_all_locks(struct mm_struct *mm)
+{
+	struct vm_area_struct *vma;
+	struct anon_vma_chain *avc;
+	MA_STATE(mas, &mm->mm_mt, 0, 0);
+
+	mmap_assert_write_locked(mm);
+
+	mutex_lock(&mm_all_locks_mutex);
+
+	mas_for_each(&mas, vma, ULONG_MAX) {
+		if (signal_pending(current))
+			goto out_unlock;
+		if (vma->vm_file && vma->vm_file->f_mapping &&
+				is_vm_hugetlb_page(vma))
+			vm_lock_mapping(mm, vma->vm_file->f_mapping);
+	}
+
+	mas_set(&mas, 0);
+	mas_for_each(&mas, vma, ULONG_MAX) {
+		if (signal_pending(current))
+			goto out_unlock;
+		if (vma->vm_file && vma->vm_file->f_mapping &&
+				!is_vm_hugetlb_page(vma))
+			vm_lock_mapping(mm, vma->vm_file->f_mapping);
+	}
+
+	mas_set(&mas, 0);
+	mas_for_each(&mas, vma, ULONG_MAX) {
+		if (signal_pending(current))
+			goto out_unlock;
+		if (vma->anon_vma)
+			list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
+				vm_lock_anon_vma(mm, avc->anon_vma);
+	}
+
+	return 0;
+
+out_unlock:
+	mm_drop_all_locks(mm);
+	return -EINTR;
+}
+
+static void vm_unlock_anon_vma(struct anon_vma *anon_vma)
+{
+	if (test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_root.rb_node)) {
+		/*
+		 * The LSB of head.next can't change to 0 from under
+		 * us because we hold the mm_all_locks_mutex.
+		 *
+		 * We must however clear the bitflag before unlocking
+		 * the vma so the users using the anon_vma->rb_root will
+		 * never see our bitflag.
+		 *
+		 * No need of atomic instructions here, head.next
+		 * can't change from under us until we release the
+		 * anon_vma->root->rwsem.
+		 */
+		if (!__test_and_clear_bit(0, (unsigned long *)
+					  &anon_vma->root->rb_root.rb_root.rb_node))
+			BUG();
+		anon_vma_unlock_write(anon_vma);
+	}
+}
+
+static void vm_unlock_mapping(struct address_space *mapping)
+{
+	if (test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
+		/*
+		 * AS_MM_ALL_LOCKS can't change to 0 from under us
+		 * because we hold the mm_all_locks_mutex.
+		 */
+		i_mmap_unlock_write(mapping);
+		if (!test_and_clear_bit(AS_MM_ALL_LOCKS,
+					&mapping->flags))
+			BUG();
+	}
+}
+
+/*
+ * The mmap_lock cannot be released by the caller until
+ * mm_drop_all_locks() returns.
+ */
+void mm_drop_all_locks(struct mm_struct *mm)
+{
+	struct vm_area_struct *vma;
+	struct anon_vma_chain *avc;
+	MA_STATE(mas, &mm->mm_mt, 0, 0);
+
+	mmap_assert_write_locked(mm);
+	BUG_ON(!mutex_is_locked(&mm_all_locks_mutex));
+
+	mas_for_each(&mas, vma, ULONG_MAX) {
+		if (vma->anon_vma)
+			list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
+				vm_unlock_anon_vma(avc->anon_vma);
+		if (vma->vm_file && vma->vm_file->f_mapping)
+			vm_unlock_mapping(vma->vm_file->f_mapping);
+	}
+
+	mutex_unlock(&mm_all_locks_mutex);
+}
+
+/*
+ * initialise the percpu counter for VM
+ */
+void __init mmap_init(void)
+{
+	int ret;
+
+	ret = percpu_counter_init(&vm_committed_as, 0, GFP_KERNEL);
+	VM_BUG_ON(ret);
+}
+
+/*
+ * Initialise sysctl_user_reserve_kbytes.
+ *
+ * This is intended to prevent a user from starting a single memory hogging
+ * process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER
+ * mode.
+ *
+ * The default value is min(3% of free memory, 128MB)
+ * 128MB is enough to recover with sshd/login, bash, and top/kill.
+ */
+static int init_user_reserve(void)
+{
+	unsigned long free_kbytes;
+
+	free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
+
+	sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17);
+	return 0;
+}
+subsys_initcall(init_user_reserve);
+
+/*
+ * Initialise sysctl_admin_reserve_kbytes.
+ *
+ * The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin
+ * to log in and kill a memory hogging process.
+ *
+ * Systems with more than 256MB will reserve 8MB, enough to recover
+ * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
+ * only reserve 3% of free pages by default.
+ */
+static int init_admin_reserve(void)
+{
+	unsigned long free_kbytes;
+
+	free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
+
+	sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
+	return 0;
+}
+subsys_initcall(init_admin_reserve);
+
+/*
+ * Reinititalise user and admin reserves if memory is added or removed.
+ *
+ * The default user reserve max is 128MB, and the default max for the
+ * admin reserve is 8MB. These are usually, but not always, enough to
+ * enable recovery from a memory hogging process using login/sshd, a shell,
+ * and tools like top. It may make sense to increase or even disable the
+ * reserve depending on the existence of swap or variations in the recovery
+ * tools. So, the admin may have changed them.
+ *
+ * If memory is added and the reserves have been eliminated or increased above
+ * the default max, then we'll trust the admin.
+ *
+ * If memory is removed and there isn't enough free memory, then we
+ * need to reset the reserves.
+ *
+ * Otherwise keep the reserve set by the admin.
+ */
+static int reserve_mem_notifier(struct notifier_block *nb,
+			     unsigned long action, void *data)
+{
+	unsigned long tmp, free_kbytes;
+
+	switch (action) {
+	case MEM_ONLINE:
+		/* Default max is 128MB. Leave alone if modified by operator. */
+		tmp = sysctl_user_reserve_kbytes;
+		if (0 < tmp && tmp < (1UL << 17))
+			init_user_reserve();
+
+		/* Default max is 8MB.  Leave alone if modified by operator. */
+		tmp = sysctl_admin_reserve_kbytes;
+		if (0 < tmp && tmp < (1UL << 13))
+			init_admin_reserve();
+
+		break;
+	case MEM_OFFLINE:
+		free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
+
+		if (sysctl_user_reserve_kbytes > free_kbytes) {
+			init_user_reserve();
+			pr_info("vm.user_reserve_kbytes reset to %lu\n",
+				sysctl_user_reserve_kbytes);
+		}
+
+		if (sysctl_admin_reserve_kbytes > free_kbytes) {
+			init_admin_reserve();
+			pr_info("vm.admin_reserve_kbytes reset to %lu\n",
+				sysctl_admin_reserve_kbytes);
+		}
+		break;
+	default:
+		break;
+	}
+	return NOTIFY_OK;
+}
+
+static struct notifier_block reserve_mem_nb = {
+	.notifier_call = reserve_mem_notifier,
+};
+
+static int __meminit init_reserve_notifier(void)
+{
+	if (register_hotmemory_notifier(&reserve_mem_nb))
+		pr_err("Failed registering memory add/remove notifier for admin reserve\n");
+
+	return 0;
+}
+subsys_initcall(init_reserve_notifier);