/*
   *  linux/mm/nommu.c
   *
   *  Replacement code for mm functions to support CPU's that don't
   *  have any form of memory management unit (thus no virtual memory).
   *
   *  See Documentation/nommu-mmap.txt
   *

   *  Copyright (c) 2004-2008 David Howells <dhowells@redhat.com>

   *  Copyright (c) 2000-2003 David McCullough <davidm@snapgear.com>
   *  Copyright (c) 2000-2001 D Jeff Dionne <jeff@uClinux.org>
   *  Copyright (c) 2002      Greg Ungerer <gerg@snapgear.com>

   *  Copyright (c) 2007-2010 Paul Mundt <lethal@linux-sh.org>

   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #include <linux/export.h>

  #include <linux/mm.h>

  #include <linux/vmacache.h>

  #include <linux/mman.h>
  #include <linux/swap.h>
  #include <linux/file.h>
  #include <linux/highmem.h>
  #include <linux/pagemap.h>
  #include <linux/slab.h>
  #include <linux/vmalloc.h>

  #include <linux/blkdev.h>
  #include <linux/backing-dev.h>

  #include <linux/compiler.h>

  #include <linux/mount.h>
  #include <linux/personality.h>
  #include <linux/security.h>
  #include <linux/syscalls.h>

  #include <linux/audit.h>

  #include <linux/sched/sysctl.h>

  #include <linux/printk.h>

  
  #include <asm/uaccess.h>
  #include <asm/tlb.h>
  #include <asm/tlbflush.h>

  #include <asm/mmu_context.h>

  #include "internal.h"

  void *high_memory;

  EXPORT_SYMBOL(high_memory);

  struct page *mem_map;
  unsigned long max_mapnr;

  EXPORT_SYMBOL(max_mapnr);

  unsigned long highest_memmap_pfn;

  struct percpu_counter vm_committed_as;

  int sysctl_overcommit_memory = OVERCOMMIT_GUESS; /* heuristic overcommit */
  int sysctl_overcommit_ratio = 50; /* default is 50% */

  unsigned long sysctl_overcommit_kbytes __read_mostly;

  int sysctl_max_map_count = DEFAULT_MAX_MAP_COUNT;

  int sysctl_nr_trim_pages = CONFIG_NOMMU_INITIAL_TRIM_EXCESS;

  unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */

  unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */

  int heap_stack_gap = 0;

  atomic_long_t mmap_pages_allocated;

  /*
   * The global memory commitment made in the system can be a metric
   * that can be used to drive ballooning decisions when Linux is hosted
   * as a guest. On Hyper-V, the host implements a policy engine for dynamically
   * balancing memory across competing virtual machines that are hosted.
   * Several metrics drive this policy engine including the guest reported
   * memory commitment.
   */
  unsigned long vm_memory_committed(void)
  {
  	return percpu_counter_read_positive(&vm_committed_as);
  }
  
  EXPORT_SYMBOL_GPL(vm_memory_committed);

  EXPORT_SYMBOL(mem_map);

  /* list of mapped, potentially shareable regions */
  static struct kmem_cache *vm_region_jar;
  struct rb_root nommu_region_tree = RB_ROOT;
  DECLARE_RWSEM(nommu_region_sem);

  const struct vm_operations_struct generic_file_vm_ops = {

  };
  
  /*

   * Return the total memory allocated for this pointer, not
   * just what the caller asked for.
   *
   * Doesn't have to be accurate, i.e. may have races.
   */
  unsigned int kobjsize(const void *objp)
  {
  	struct page *page;

  	/*
  	 * If the object we have should not have ksize performed on it,
  	 * return size of 0
  	 */

  	if (!objp || !virt_addr_valid(objp))

  		return 0;
  
  	page = virt_to_head_page(objp);

  
  	/*
  	 * If the allocator sets PageSlab, we know the pointer came from
  	 * kmalloc().
  	 */

  	if (PageSlab(page))
  		return ksize(objp);

  	/*

  	 * If it's not a compound page, see if we have a matching VMA
  	 * region. This test is intentionally done in reverse order,
  	 * so if there's no VMA, we still fall through and hand back
  	 * PAGE_SIZE for 0-order pages.
  	 */
  	if (!PageCompound(page)) {
  		struct vm_area_struct *vma;
  
  		vma = find_vma(current->mm, (unsigned long)objp);
  		if (vma)
  			return vma->vm_end - vma->vm_start;
  	}
  
  	/*

  	 * The ksize() function is only guaranteed to work for pointers

  	 * returned by kmalloc(). So handle arbitrary pointers here.

  	 */

  	return PAGE_SIZE << compound_order(page);

  }

  long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
  		      unsigned long start, unsigned long nr_pages,
  		      unsigned int foll_flags, struct page **pages,
  		      struct vm_area_struct **vmas, int *nonblocking)

  {

  	struct vm_area_struct *vma;

  	unsigned long vm_flags;
  	int i;
  
  	/* calculate required read or write permissions.

  	 * If FOLL_FORCE is set, we only require the "MAY" flags.

  	 */

  	vm_flags  = (foll_flags & FOLL_WRITE) ?
  			(VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
  	vm_flags &= (foll_flags & FOLL_FORCE) ?
  			(VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);

  	for (i = 0; i < nr_pages; i++) {

  		vma = find_vma(mm, start);

  		if (!vma)
  			goto finish_or_fault;
  
  		/* protect what we can, including chardevs */

  		if ((vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
  		    !(vm_flags & vma->vm_flags))

  			goto finish_or_fault;

  		if (pages) {
  			pages[i] = virt_to_page(start);
  			if (pages[i])
  				page_cache_get(pages[i]);
  		}
  		if (vmas)

  			vmas[i] = vma;

  		start = (start + PAGE_SIZE) & PAGE_MASK;

  	}

  
  	return i;
  
  finish_or_fault:
  	return i ? : -EFAULT;

  }

  /*
   * get a list of pages in an address range belonging to the specified process
   * and indicate the VMA that covers each page
   * - this is potentially dodgy as we may end incrementing the page count of a
   *   slab page or a secondary page from a compound page
   * - don't permit access to VMAs that don't support it, such as I/O mappings
   */

  long get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
  		    unsigned long start, unsigned long nr_pages,
  		    int write, int force, struct page **pages,
  		    struct vm_area_struct **vmas)

  {
  	int flags = 0;
  
  	if (write)

  		flags |= FOLL_WRITE;

  	if (force)

  		flags |= FOLL_FORCE;

  	return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas,
  				NULL);

  }

  EXPORT_SYMBOL(get_user_pages);

  long get_user_pages_locked(struct task_struct *tsk, struct mm_struct *mm,
  			   unsigned long start, unsigned long nr_pages,
  			   int write, int force, struct page **pages,
  			   int *locked)
  {
  	return get_user_pages(tsk, mm, start, nr_pages, write, force,
  			      pages, NULL);
  }
  EXPORT_SYMBOL(get_user_pages_locked);

  long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
  			       unsigned long start, unsigned long nr_pages,
  			       int write, int force, struct page **pages,
  			       unsigned int gup_flags)

  {
  	long ret;
  	down_read(&mm->mmap_sem);
  	ret = get_user_pages(tsk, mm, start, nr_pages, write, force,
  			     pages, NULL);
  	up_read(&mm->mmap_sem);
  	return ret;
  }

  EXPORT_SYMBOL(__get_user_pages_unlocked);
  
  long get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
  			     unsigned long start, unsigned long nr_pages,
  			     int write, int force, struct page **pages)
  {
  	return __get_user_pages_unlocked(tsk, mm, start, nr_pages, write,
  					 force, pages, 0);
  }

  EXPORT_SYMBOL(get_user_pages_unlocked);

  /**
   * follow_pfn - look up PFN at a user virtual address
   * @vma: memory mapping
   * @address: user virtual address
   * @pfn: location to store found PFN
   *
   * Only IO mappings and raw PFN mappings are allowed.
   *
   * Returns zero and the pfn at @pfn on success, -ve otherwise.
   */
  int follow_pfn(struct vm_area_struct *vma, unsigned long address,
  	unsigned long *pfn)
  {
  	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
  		return -EINVAL;
  
  	*pfn = address >> PAGE_SHIFT;
  	return 0;
  }
  EXPORT_SYMBOL(follow_pfn);

  LIST_HEAD(vmap_area_list);

  void vfree(const void *addr)

  {
  	kfree(addr);
  }

  EXPORT_SYMBOL(vfree);

  void *__vmalloc(unsigned long size, gfp_t gfp_mask, pgprot_t prot)

  {
  	/*

  	 *  You can't specify __GFP_HIGHMEM with kmalloc() since kmalloc()
  	 * returns only a logical address.

  	 */

  	return kmalloc(size, (gfp_mask | __GFP_COMP) & ~__GFP_HIGHMEM);

  }

  EXPORT_SYMBOL(__vmalloc);

  void *vmalloc_user(unsigned long size)
  {
  	void *ret;
  
  	ret = __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
  			PAGE_KERNEL);
  	if (ret) {
  		struct vm_area_struct *vma;
  
  		down_write(&current->mm->mmap_sem);
  		vma = find_vma(current->mm, (unsigned long)ret);
  		if (vma)
  			vma->vm_flags |= VM_USERMAP;
  		up_write(&current->mm->mmap_sem);
  	}
  
  	return ret;
  }
  EXPORT_SYMBOL(vmalloc_user);

  struct page *vmalloc_to_page(const void *addr)

  {
  	return virt_to_page(addr);
  }

  EXPORT_SYMBOL(vmalloc_to_page);

  unsigned long vmalloc_to_pfn(const void *addr)

  {
  	return page_to_pfn(virt_to_page(addr));
  }

  EXPORT_SYMBOL(vmalloc_to_pfn);

  
  long vread(char *buf, char *addr, unsigned long count)
  {

  	/* Don't allow overflow */
  	if ((unsigned long) buf + count < count)
  		count = -(unsigned long) buf;

  	memcpy(buf, addr, count);
  	return count;
  }
  
  long vwrite(char *buf, char *addr, unsigned long count)
  {
  	/* Don't allow overflow */
  	if ((unsigned long) addr + count < count)
  		count = -(unsigned long) addr;
  
  	memcpy(addr, buf, count);

  	return count;

  }
  
  /*
   *	vmalloc  -  allocate virtually continguos memory
   *
   *	@size:		allocation size
   *
   *	Allocate enough pages to cover @size from the page level
   *	allocator and map them into continguos kernel virtual space.
   *

   *	For tight control over page level allocator and protection flags

   *	use __vmalloc() instead.
   */
  void *vmalloc(unsigned long size)
  {
         return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL);
  }

  EXPORT_SYMBOL(vmalloc);

  /*
   *	vzalloc - allocate virtually continguos memory with zero fill
   *
   *	@size:		allocation size
   *
   *	Allocate enough pages to cover @size from the page level
   *	allocator and map them into continguos kernel virtual space.
   *	The memory allocated is set to zero.
   *
   *	For tight control over page level allocator and protection flags
   *	use __vmalloc() instead.
   */
  void *vzalloc(unsigned long size)
  {
  	return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
  			PAGE_KERNEL);
  }
  EXPORT_SYMBOL(vzalloc);
  
  /**
   * vmalloc_node - allocate memory on a specific node
   * @size:	allocation size
   * @node:	numa node
   *
   * Allocate enough pages to cover @size from the page level
   * allocator and map them into contiguous kernel virtual space.
   *
   * For tight control over page level allocator and protection flags
   * use __vmalloc() instead.
   */

  void *vmalloc_node(unsigned long size, int node)
  {
  	return vmalloc(size);
  }

  EXPORT_SYMBOL(vmalloc_node);

  
  /**
   * vzalloc_node - allocate memory on a specific node with zero fill
   * @size:	allocation size
   * @node:	numa node
   *
   * Allocate enough pages to cover @size from the page level
   * allocator and map them into contiguous kernel virtual space.
   * The memory allocated is set to zero.
   *
   * For tight control over page level allocator and protection flags
   * use __vmalloc() instead.
   */
  void *vzalloc_node(unsigned long size, int node)
  {
  	return vzalloc(size);
  }
  EXPORT_SYMBOL(vzalloc_node);

  #ifndef PAGE_KERNEL_EXEC
  # define PAGE_KERNEL_EXEC PAGE_KERNEL
  #endif
  
  /**
   *	vmalloc_exec  -  allocate virtually contiguous, executable memory
   *	@size:		allocation size
   *
   *	Kernel-internal function to allocate enough pages to cover @size
   *	the page level allocator and map them into contiguous and
   *	executable kernel virtual space.
   *
   *	For tight control over page level allocator and protection flags
   *	use __vmalloc() instead.
   */
  
  void *vmalloc_exec(unsigned long size)
  {
  	return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL_EXEC);
  }

  /**
   * vmalloc_32  -  allocate virtually contiguous memory (32bit addressable)

   *	@size:		allocation size
   *
   *	Allocate enough 32bit PA addressable pages to cover @size from the
   *	page level allocator and map them into continguos kernel virtual space.
   */
  void *vmalloc_32(unsigned long size)
  {
  	return __vmalloc(size, GFP_KERNEL, PAGE_KERNEL);
  }

  EXPORT_SYMBOL(vmalloc_32);
  
  /**
   * vmalloc_32_user - allocate zeroed virtually contiguous 32bit memory
   *	@size:		allocation size
   *
   * The resulting memory area is 32bit addressable and zeroed so it can be
   * mapped to userspace without leaking data.

   *
   * VM_USERMAP is set on the corresponding VMA so that subsequent calls to
   * remap_vmalloc_range() are permissible.

   */
  void *vmalloc_32_user(unsigned long size)
  {

  	/*
  	 * We'll have to sort out the ZONE_DMA bits for 64-bit,
  	 * but for now this can simply use vmalloc_user() directly.
  	 */
  	return vmalloc_user(size);

  }
  EXPORT_SYMBOL(vmalloc_32_user);

  
  void *vmap(struct page **pages, unsigned int count, unsigned long flags, pgprot_t prot)
  {
  	BUG();
  	return NULL;
  }

  EXPORT_SYMBOL(vmap);

  void vunmap(const void *addr)

  {
  	BUG();
  }

  EXPORT_SYMBOL(vunmap);

  void *vm_map_ram(struct page **pages, unsigned int count, int node, pgprot_t prot)
  {
  	BUG();
  	return NULL;
  }
  EXPORT_SYMBOL(vm_map_ram);
  
  void vm_unmap_ram(const void *mem, unsigned int count)
  {
  	BUG();
  }
  EXPORT_SYMBOL(vm_unmap_ram);
  
  void vm_unmap_aliases(void)
  {
  }
  EXPORT_SYMBOL_GPL(vm_unmap_aliases);

  /*

   * Implement a stub for vmalloc_sync_all() if the architecture chose not to
   * have one.
   */

  void __weak vmalloc_sync_all(void)

  {
  }

  /**
   *	alloc_vm_area - allocate a range of kernel address space
   *	@size:		size of the area
   *
   *	Returns:	NULL on failure, vm_struct on success
   *
   *	This function reserves a range of kernel address space, and
   *	allocates pagetables to map that range.  No actual mappings
   *	are created.  If the kernel address space is not shared
   *	between processes, it syncs the pagetable across all
   *	processes.
   */

  struct vm_struct *alloc_vm_area(size_t size, pte_t **ptes)

  {
  	BUG();
  	return NULL;
  }
  EXPORT_SYMBOL_GPL(alloc_vm_area);
  
  void free_vm_area(struct vm_struct *area)
  {
  	BUG();
  }
  EXPORT_SYMBOL_GPL(free_vm_area);

  int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
  		   struct page *page)
  {
  	return -EINVAL;
  }
  EXPORT_SYMBOL(vm_insert_page);

  /*

   *  sys_brk() for the most part doesn't need the global kernel
   *  lock, except when an application is doing something nasty
   *  like trying to un-brk an area that has already been mapped
   *  to a regular file.  in this case, the unmapping will need
   *  to invoke file system routines that need the global lock.
   */

  SYSCALL_DEFINE1(brk, unsigned long, brk)

  {
  	struct mm_struct *mm = current->mm;
  
  	if (brk < mm->start_brk || brk > mm->context.end_brk)
  		return mm->brk;
  
  	if (mm->brk == brk)
  		return mm->brk;
  
  	/*
  	 * Always allow shrinking brk
  	 */
  	if (brk <= mm->brk) {
  		mm->brk = brk;
  		return brk;
  	}
  
  	/*
  	 * Ok, looks good - let it rip.
  	 */

  	flush_icache_range(mm->brk, brk);

  	return mm->brk = brk;
  }

  /*
   * initialise the VMA and region record slabs
   */
  void __init mmap_init(void)

  {

  	int ret;

  	ret = percpu_counter_init(&vm_committed_as, 0, GFP_KERNEL);

  	VM_BUG_ON(ret);

  	vm_region_jar = KMEM_CACHE(vm_region, SLAB_PANIC);

  }

  /*

   * validate the region tree
   * - the caller must hold the region lock

   */

  #ifdef CONFIG_DEBUG_NOMMU_REGIONS
  static noinline void validate_nommu_regions(void)

  {

  	struct vm_region *region, *last;
  	struct rb_node *p, *lastp;

  	lastp = rb_first(&nommu_region_tree);
  	if (!lastp)
  		return;
  
  	last = rb_entry(lastp, struct vm_region, vm_rb);

  	BUG_ON(unlikely(last->vm_end <= last->vm_start));
  	BUG_ON(unlikely(last->vm_top < last->vm_end));

  
  	while ((p = rb_next(lastp))) {
  		region = rb_entry(p, struct vm_region, vm_rb);
  		last = rb_entry(lastp, struct vm_region, vm_rb);

  		BUG_ON(unlikely(region->vm_end <= region->vm_start));
  		BUG_ON(unlikely(region->vm_top < region->vm_end));
  		BUG_ON(unlikely(region->vm_start < last->vm_top));

  		lastp = p;
  	}

  }

  #else

  static void validate_nommu_regions(void)
  {
  }

  #endif

  
  /*

   * add a region into the global tree

   */

  static void add_nommu_region(struct vm_region *region)

  {

  	struct vm_region *pregion;
  	struct rb_node **p, *parent;

  	validate_nommu_regions();

  	parent = NULL;
  	p = &nommu_region_tree.rb_node;
  	while (*p) {
  		parent = *p;
  		pregion = rb_entry(parent, struct vm_region, vm_rb);
  		if (region->vm_start < pregion->vm_start)
  			p = &(*p)->rb_left;
  		else if (region->vm_start > pregion->vm_start)
  			p = &(*p)->rb_right;
  		else if (pregion == region)
  			return;
  		else
  			BUG();

  	}

  	rb_link_node(&region->vm_rb, parent, p);
  	rb_insert_color(&region->vm_rb, &nommu_region_tree);

  	validate_nommu_regions();

  }

  
  /*

   * delete a region from the global tree

   */

  static void delete_nommu_region(struct vm_region *region)

  {

  	BUG_ON(!nommu_region_tree.rb_node);

  	validate_nommu_regions();
  	rb_erase(&region->vm_rb, &nommu_region_tree);
  	validate_nommu_regions();

  }

  /*

   * free a contiguous series of pages

   */

  static void free_page_series(unsigned long from, unsigned long to)

  {

  	for (; from < to; from += PAGE_SIZE) {
  		struct page *page = virt_to_page(from);

  		atomic_long_dec(&mmap_pages_allocated);

  		put_page(page);

  	}

  }
  
  /*

   * release a reference to a region

   * - the caller must hold the region semaphore for writing, which this releases

   * - the region may not have been added to the tree yet, in which case vm_top

   *   will equal vm_start

   */

  static void __put_nommu_region(struct vm_region *region)
  	__releases(nommu_region_sem)

  {

  	BUG_ON(!nommu_region_tree.rb_node);

  	if (--region->vm_usage == 0) {

  		if (region->vm_top > region->vm_start)

  			delete_nommu_region(region);
  		up_write(&nommu_region_sem);
  
  		if (region->vm_file)
  			fput(region->vm_file);
  
  		/* IO memory and memory shared directly out of the pagecache
  		 * from ramfs/tmpfs mustn't be released here */

  		if (region->vm_flags & VM_MAPPED_COPY)

  			free_page_series(region->vm_start, region->vm_top);

  		kmem_cache_free(vm_region_jar, region);
  	} else {
  		up_write(&nommu_region_sem);

  	}

  }

  /*
   * release a reference to a region
   */
  static void put_nommu_region(struct vm_region *region)
  {
  	down_write(&nommu_region_sem);
  	__put_nommu_region(region);

  }

  /*

   * update protection on a vma
   */
  static void protect_vma(struct vm_area_struct *vma, unsigned long flags)
  {
  #ifdef CONFIG_MPU
  	struct mm_struct *mm = vma->vm_mm;
  	long start = vma->vm_start & PAGE_MASK;
  	while (start < vma->vm_end) {
  		protect_page(mm, start, flags);
  		start += PAGE_SIZE;
  	}
  	update_protections(mm);
  #endif
  }
  
  /*

   * add a VMA into a process's mm_struct in the appropriate place in the list
   * and tree and add to the address space's page tree also if not an anonymous
   * page
   * - should be called with mm->mmap_sem held writelocked

   */

  static void add_vma_to_mm(struct mm_struct *mm, struct vm_area_struct *vma)

  {

  	struct vm_area_struct *pvma, *prev;

  	struct address_space *mapping;

  	struct rb_node **p, *parent, *rb_prev;

  	BUG_ON(!vma->vm_region);
  
  	mm->map_count++;
  	vma->vm_mm = mm;

  	protect_vma(vma, vma->vm_flags);

  	/* add the VMA to the mapping */
  	if (vma->vm_file) {
  		mapping = vma->vm_file->f_mapping;

  		i_mmap_lock_write(mapping);

  		flush_dcache_mmap_lock(mapping);

  		vma_interval_tree_insert(vma, &mapping->i_mmap);

  		flush_dcache_mmap_unlock(mapping);

  		i_mmap_unlock_write(mapping);

  	}

  	/* add the VMA to the tree */

  	parent = rb_prev = NULL;

  	p = &mm->mm_rb.rb_node;

  	while (*p) {
  		parent = *p;
  		pvma = rb_entry(parent, struct vm_area_struct, vm_rb);

  		/* sort by: start addr, end addr, VMA struct addr in that order
  		 * (the latter is necessary as we may get identical VMAs) */
  		if (vma->vm_start < pvma->vm_start)

  			p = &(*p)->rb_left;

  		else if (vma->vm_start > pvma->vm_start) {
  			rb_prev = parent;

  			p = &(*p)->rb_right;

  		} else if (vma->vm_end < pvma->vm_end)

  			p = &(*p)->rb_left;

  		else if (vma->vm_end > pvma->vm_end) {
  			rb_prev = parent;

  			p = &(*p)->rb_right;

  		} else if (vma < pvma)

  			p = &(*p)->rb_left;

  		else if (vma > pvma) {
  			rb_prev = parent;

  			p = &(*p)->rb_right;

  		} else

  			BUG();

  	}
  
  	rb_link_node(&vma->vm_rb, parent, p);

  	rb_insert_color(&vma->vm_rb, &mm->mm_rb);
  
  	/* add VMA to the VMA list also */

  	prev = NULL;
  	if (rb_prev)
  		prev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);

  	__vma_link_list(mm, vma, prev, parent);

  }

  /*

   * delete a VMA from its owning mm_struct and address space

   */

  static void delete_vma_from_mm(struct vm_area_struct *vma)

  {

  	int i;

  	struct address_space *mapping;

  	struct mm_struct *mm = vma->vm_mm;

  	struct task_struct *curr = current;

  	protect_vma(vma, 0);

  	mm->map_count--;

  	for (i = 0; i < VMACACHE_SIZE; i++) {
  		/* if the vma is cached, invalidate the entire cache */
  		if (curr->vmacache[i] == vma) {

  			vmacache_invalidate(mm);

  			break;
  		}
  	}

  
  	/* remove the VMA from the mapping */
  	if (vma->vm_file) {
  		mapping = vma->vm_file->f_mapping;

  		i_mmap_lock_write(mapping);

  		flush_dcache_mmap_lock(mapping);

  		vma_interval_tree_remove(vma, &mapping->i_mmap);

  		flush_dcache_mmap_unlock(mapping);

  		i_mmap_unlock_write(mapping);

  	}

  	/* remove from the MM's tree and list */
  	rb_erase(&vma->vm_rb, &mm->mm_rb);

  
  	if (vma->vm_prev)
  		vma->vm_prev->vm_next = vma->vm_next;
  	else
  		mm->mmap = vma->vm_next;
  
  	if (vma->vm_next)
  		vma->vm_next->vm_prev = vma->vm_prev;

  }
  
  /*
   * destroy a VMA record
   */
  static void delete_vma(struct mm_struct *mm, struct vm_area_struct *vma)
  {

  	if (vma->vm_ops && vma->vm_ops->close)
  		vma->vm_ops->close(vma);

  	if (vma->vm_file)

  		fput(vma->vm_file);

  	put_nommu_region(vma->vm_region);
  	kmem_cache_free(vm_area_cachep, vma);
  }
  
  /*
   * look up the first VMA in which addr resides, NULL if none
   * - should be called with mm->mmap_sem at least held readlocked
   */
  struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
  {
  	struct vm_area_struct *vma;

  
  	/* check the cache first */

  	vma = vmacache_find(mm, addr);
  	if (likely(vma))

  		return vma;

  	/* trawl the list (there may be multiple mappings in which addr

  	 * resides) */

  	for (vma = mm->mmap; vma; vma = vma->vm_next) {

  		if (vma->vm_start > addr)
  			return NULL;
  		if (vma->vm_end > addr) {

  			vmacache_update(addr, vma);

  			return vma;
  		}
  	}
  
  	return NULL;
  }
  EXPORT_SYMBOL(find_vma);
  
  /*
   * find a VMA
   * - we don't extend stack VMAs under NOMMU conditions
   */
  struct vm_area_struct *find_extend_vma(struct mm_struct *mm, unsigned long addr)
  {

  	return find_vma(mm, addr);

  }
  
  /*
   * expand a stack to a given address
   * - not supported under NOMMU conditions
   */
  int expand_stack(struct vm_area_struct *vma, unsigned long address)
  {
  	return -ENOMEM;
  }
  
  /*
   * look up the first VMA exactly that exactly matches addr
   * - should be called with mm->mmap_sem at least held readlocked
   */
  static struct vm_area_struct *find_vma_exact(struct mm_struct *mm,
  					     unsigned long addr,
  					     unsigned long len)
  {
  	struct vm_area_struct *vma;

  	unsigned long end = addr + len;
  
  	/* check the cache first */

  	vma = vmacache_find_exact(mm, addr, end);
  	if (vma)

  		return vma;

  	/* trawl the list (there may be multiple mappings in which addr

  	 * resides) */

  	for (vma = mm->mmap; vma; vma = vma->vm_next) {

  		if (vma->vm_start < addr)
  			continue;
  		if (vma->vm_start > addr)
  			return NULL;
  		if (vma->vm_end == end) {

  			vmacache_update(addr, vma);

  			return vma;
  		}
  	}
  
  	return NULL;

  }
  
  /*
   * determine whether a mapping should be permitted and, if so, what sort of
   * mapping we're capable of supporting
   */
  static int validate_mmap_request(struct file *file,
  				 unsigned long addr,
  				 unsigned long len,
  				 unsigned long prot,
  				 unsigned long flags,
  				 unsigned long pgoff,
  				 unsigned long *_capabilities)
  {

  	unsigned long capabilities, rlen;

  	int ret;
  
  	/* do the simple checks first */

  	if (flags & MAP_FIXED)

  		return -EINVAL;

  
  	if ((flags & MAP_TYPE) != MAP_PRIVATE &&
  	    (flags & MAP_TYPE) != MAP_SHARED)
  		return -EINVAL;

  	if (!len)

  		return -EINVAL;

  	/* Careful about overflows.. */

  	rlen = PAGE_ALIGN(len);
  	if (!rlen || rlen > TASK_SIZE)

  		return -ENOMEM;

  	/* offset overflow? */

  	if ((pgoff + (rlen >> PAGE_SHIFT)) < pgoff)

  		return -EOVERFLOW;

  
  	if (file) {

  		/* files must support mmap */

  		if (!file->f_op->mmap)

  			return -ENODEV;
  
  		/* work out if what we've got could possibly be shared
  		 * - we support chardevs that provide their own "memory"
  		 * - we support files/blockdevs that are memory backed
  		 */

  		if (file->f_op->mmap_capabilities) {
  			capabilities = file->f_op->mmap_capabilities(file);
  		} else {

  			/* no explicit capabilities set, so assume some
  			 * defaults */

  			switch (file_inode(file)->i_mode & S_IFMT) {

  			case S_IFREG:
  			case S_IFBLK:

  				capabilities = NOMMU_MAP_COPY;

  				break;
  
  			case S_IFCHR:
  				capabilities =

  					NOMMU_MAP_DIRECT |
  					NOMMU_MAP_READ |
  					NOMMU_MAP_WRITE;

  				break;
  
  			default:
  				return -EINVAL;
  			}
  		}
  
  		/* eliminate any capabilities that we can't support on this
  		 * device */
  		if (!file->f_op->get_unmapped_area)

  			capabilities &= ~NOMMU_MAP_DIRECT;

  		if (!(file->f_mode & FMODE_CAN_READ))

  			capabilities &= ~NOMMU_MAP_COPY;

  		/* The file shall have been opened with read permission. */
  		if (!(file->f_mode & FMODE_READ))
  			return -EACCES;

  		if (flags & MAP_SHARED) {
  			/* do checks for writing, appending and locking */
  			if ((prot & PROT_WRITE) &&
  			    !(file->f_mode & FMODE_WRITE))
  				return -EACCES;

  			if (IS_APPEND(file_inode(file)) &&

  			    (file->f_mode & FMODE_WRITE))
  				return -EACCES;

  			if (locks_verify_locked(file))

  				return -EAGAIN;

  			if (!(capabilities & NOMMU_MAP_DIRECT))

  				return -ENODEV;

  			/* we mustn't privatise shared mappings */

  			capabilities &= ~NOMMU_MAP_COPY;

  		} else {

  			/* we're going to read the file into private memory we
  			 * allocate */

  			if (!(capabilities & NOMMU_MAP_COPY))

  				return -ENODEV;
  
  			/* we don't permit a private writable mapping to be
  			 * shared with the backing device */
  			if (prot & PROT_WRITE)

  				capabilities &= ~NOMMU_MAP_DIRECT;

  		}

  		if (capabilities & NOMMU_MAP_DIRECT) {
  			if (((prot & PROT_READ)  && !(capabilities & NOMMU_MAP_READ))  ||
  			    ((prot & PROT_WRITE) && !(capabilities & NOMMU_MAP_WRITE)) ||
  			    ((prot & PROT_EXEC)  && !(capabilities & NOMMU_MAP_EXEC))

  			    ) {

  				capabilities &= ~NOMMU_MAP_DIRECT;

  				if (flags & MAP_SHARED) {

  					pr_warn("MAP_SHARED not completely supported on !MMU
  ");

  					return -EINVAL;
  				}
  			}
  		}

  		/* handle executable mappings and implied executable
  		 * mappings */

  		if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) {

  			if (prot & PROT_EXEC)
  				return -EPERM;

  		} else if ((prot & PROT_READ) && !(prot & PROT_EXEC)) {

  			/* handle implication of PROT_EXEC by PROT_READ */
  			if (current->personality & READ_IMPLIES_EXEC) {

  				if (capabilities & NOMMU_MAP_EXEC)

  					prot |= PROT_EXEC;
  			}

  		} else if ((prot & PROT_READ) &&

  			 (prot & PROT_EXEC) &&

  			 !(capabilities & NOMMU_MAP_EXEC)

  			 ) {
  			/* backing file is not executable, try to copy */

  			capabilities &= ~NOMMU_MAP_DIRECT;

  		}

  	} else {

  		/* anonymous mappings are always memory backed and can be
  		 * privately mapped
  		 */

  		capabilities = NOMMU_MAP_COPY;

  
  		/* handle PROT_EXEC implication by PROT_READ */
  		if ((prot & PROT_READ) &&
  		    (current->personality & READ_IMPLIES_EXEC))
  			prot |= PROT_EXEC;
  	}
  
  	/* allow the security API to have its say */

  	ret = security_mmap_addr(addr);
  	if (ret < 0)
  		return ret;

  
  	/* looks okay */
  	*_capabilities = capabilities;
  	return 0;
  }
  
  /*
   * we've determined that we can make the mapping, now translate what we
   * now know into VMA flags
   */
  static unsigned long determine_vm_flags(struct file *file,
  					unsigned long prot,
  					unsigned long flags,
  					unsigned long capabilities)
  {
  	unsigned long vm_flags;
  
  	vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags);

  	/* vm_flags |= mm->def_flags; */

  	if (!(capabilities & NOMMU_MAP_DIRECT)) {

  		/* attempt to share read-only copies of mapped file chunks */

  		vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;

  		if (file && !(prot & PROT_WRITE))
  			vm_flags |= VM_MAYSHARE;

  	} else {

  		/* overlay a shareable mapping on the backing device or inode
  		 * if possible - used for chardevs, ramfs/tmpfs/shmfs and
  		 * romfs/cramfs */

  		vm_flags |= VM_MAYSHARE | (capabilities & NOMMU_VMFLAGS);

  		if (flags & MAP_SHARED)

  			vm_flags |= VM_SHARED;

  	}
  
  	/* refuse to let anyone share private mappings with this process if
  	 * it's being traced - otherwise breakpoints set in it may interfere
  	 * with another untraced process
  	 */

  	if ((flags & MAP_PRIVATE) && current->ptrace)

  		vm_flags &= ~VM_MAYSHARE;
  
  	return vm_flags;
  }
  
  /*

   * set up a shared mapping on a file (the driver or filesystem provides and
   * pins the storage)

   */

  static int do_mmap_shared_file(struct vm_area_struct *vma)

  {
  	int ret;
  
  	ret = vma->vm_file->f_op->mmap(vma->vm_file, vma);

  	if (ret == 0) {
  		vma->vm_region->vm_top = vma->vm_region->vm_end;

  		return 0;

  	}

  	if (ret != -ENOSYS)
  		return ret;

  	/* getting -ENOSYS indicates that direct mmap isn't possible (as
  	 * opposed to tried but failed) so we can only give a suitable error as
  	 * it's not possible to make a private copy if MAP_SHARED was given */

  	return -ENODEV;
  }
  
  /*
   * set up a private mapping or an anonymous shared mapping
   */

  static int do_mmap_private(struct vm_area_struct *vma,
  			   struct vm_region *region,

  			   unsigned long len,
  			   unsigned long capabilities)

  {

  	unsigned long total, point;

  	void *base;

  	int ret, order;

  
  	/* invoke the file's mapping function so that it can keep track of
  	 * shared mappings on devices or memory
  	 * - VM_MAYSHARE will be set if it may attempt to share
  	 */

  	if (capabilities & NOMMU_MAP_DIRECT) {

  		ret = vma->vm_file->f_op->mmap(vma->vm_file, vma);

  		if (ret == 0) {

  			/* shouldn't return success if we're not sharing */

  			BUG_ON(!(vma->vm_flags & VM_MAYSHARE));
  			vma->vm_region->vm_top = vma->vm_region->vm_end;

  			return 0;

  		}

  		if (ret != -ENOSYS)
  			return ret;

  
  		/* getting an ENOSYS error indicates that direct mmap isn't
  		 * possible (as opposed to tried but failed) so we'll try to
  		 * make a private copy of the data and map that instead */
  	}

  	/* allocate some memory to hold the mapping
  	 * - note that this may not return a page-aligned address if the object
  	 *   we're allocating is smaller than a page
  	 */

  	order = get_order(len);

  	total = 1 << order;

  	point = len >> PAGE_SHIFT;

  	/* we don't want to allocate a power-of-2 sized page set */

  	if (sysctl_nr_trim_pages && total - point >= sysctl_nr_trim_pages)

  		total = point;

  	base = alloc_pages_exact(total << PAGE_SHIFT, GFP_KERNEL);

  	if (!base)
  		goto enomem;
  
  	atomic_long_add(total, &mmap_pages_allocated);

  	region->vm_flags = vma->vm_flags |= VM_MAPPED_COPY;
  	region->vm_start = (unsigned long) base;

  	region->vm_end   = region->vm_start + len;

  	region->vm_top   = region->vm_start + (total << PAGE_SHIFT);

  
  	vma->vm_start = region->vm_start;
  	vma->vm_end   = region->vm_start + len;

  
  	if (vma->vm_file) {
  		/* read the contents of a file into the copy */
  		mm_segment_t old_fs;
  		loff_t fpos;
  
  		fpos = vma->vm_pgoff;
  		fpos <<= PAGE_SHIFT;
  
  		old_fs = get_fs();
  		set_fs(KERNEL_DS);

  		ret = __vfs_read(vma->vm_file, base, len, &fpos);

  		set_fs(old_fs);
  
  		if (ret < 0)
  			goto error_free;
  
  		/* clear the last little bit */

  		if (ret < len)
  			memset(base + ret, 0, len - ret);

  	}
  
  	return 0;
  
  error_free:

  	free_page_series(region->vm_start, region->vm_top);

  	region->vm_start = vma->vm_start = 0;
  	region->vm_end   = vma->vm_end = 0;

  	region->vm_top   = 0;

  	return ret;
  
  enomem:

  	pr_err("Allocation of length %lu from process %d (%s) failed
  ",

  	       len, current->pid, current->comm);

  	show_free_areas(0);

  	return -ENOMEM;
  }
  
  /*
   * handle mapping creation for uClinux
   */

  unsigned long do_mmap_pgoff(struct file *file,

  			    unsigned long addr,
  			    unsigned long len,
  			    unsigned long prot,
  			    unsigned long flags,

  			    unsigned long pgoff,

  			    unsigned long *populate)

  {

  	struct vm_area_struct *vma;
  	struct vm_region *region;

  	struct rb_node *rb;

  	unsigned long capabilities, vm_flags, result;

  	int ret;

  	*populate = 0;

  	/* decide whether we should attempt the mapping, and if so what sort of
  	 * mapping */
  	ret = validate_mmap_request(file, addr, len, prot, flags, pgoff,
  				    &capabilities);

  	if (ret < 0)

  		return ret;

  	/* we ignore the address hint */
  	addr = 0;

  	len = PAGE_ALIGN(len);

  	/* we've determined that we can make the mapping, now translate what we
  	 * now know into VMA flags */
  	vm_flags = determine_vm_flags(file, prot, flags, capabilities);

  	/* we're going to need to record the mapping */
  	region = kmem_cache_zalloc(vm_region_jar, GFP_KERNEL);
  	if (!region)
  		goto error_getting_region;
  
  	vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
  	if (!vma)
  		goto error_getting_vma;

  	region->vm_usage = 1;

  	region->vm_flags = vm_flags;
  	region->vm_pgoff = pgoff;

  	INIT_LIST_HEAD(&vma->anon_vma_chain);

  	vma->vm_flags = vm_flags;
  	vma->vm_pgoff = pgoff;

  	if (file) {

  		region->vm_file = get_file(file);
  		vma->vm_file = get_file(file);

  	}
  
  	down_write(&nommu_region_sem);
  
  	/* if we want to share, we need to check for regions created by other

  	 * mmap() calls that overlap with our proposed mapping

  	 * - we can only share with a superset match on most regular files

  	 * - shared mappings on character devices and memory backed files are
  	 *   permitted to overlap inexactly as far as we are concerned for in
  	 *   these cases, sharing is handled in the driver or filesystem rather
  	 *   than here
  	 */
  	if (vm_flags & VM_MAYSHARE) {

  		struct vm_region *pregion;
  		unsigned long pglen, rpglen, pgend, rpgend, start;

  		pglen = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
  		pgend = pgoff + pglen;

  		for (rb = rb_first(&nommu_region_tree); rb; rb = rb_next(rb)) {
  			pregion = rb_entry(rb, struct vm_region, vm_rb);

  			if (!(pregion->vm_flags & VM_MAYSHARE))

  				continue;
  
  			/* search for overlapping mappings on the same file */

  			if (file_inode(pregion->vm_file) !=
  			    file_inode(file))

  				continue;

  			if (pregion->vm_pgoff >= pgend)

  				continue;

  			rpglen = pregion->vm_end - pregion->vm_start;
  			rpglen = (rpglen + PAGE_SIZE - 1) >> PAGE_SHIFT;
  			rpgend = pregion->vm_pgoff + rpglen;
  			if (pgoff >= rpgend)

  				continue;

  			/* handle inexactly overlapping matches between
  			 * mappings */
  			if ((pregion->vm_pgoff != pgoff || rpglen != pglen) &&
  			    !(pgoff >= pregion->vm_pgoff && pgend <= rpgend)) {
  				/* new mapping is not a subset of the region */

  				if (!(capabilities & NOMMU_MAP_DIRECT))

  					goto sharing_violation;
  				continue;
  			}

  			/* we've found a region we can share */

  			pregion->vm_usage++;

  			vma->vm_region = pregion;
  			start = pregion->vm_start;
  			start += (pgoff - pregion->vm_pgoff) << PAGE_SHIFT;
  			vma->vm_start = start;
  			vma->vm_end = start + len;

  			if (pregion->vm_flags & VM_MAPPED_COPY)

  				vma->vm_flags |= VM_MAPPED_COPY;

  			else {

  				ret = do_mmap_shared_file(vma);
  				if (ret < 0) {
  					vma->vm_region = NULL;
  					vma->vm_start = 0;
  					vma->vm_end = 0;

  					pregion->vm_usage--;

  					pregion = NULL;
  					goto error_just_free;
  				}
  			}
  			fput(region->vm_file);
  			kmem_cache_free(vm_region_jar, region);
  			region = pregion;
  			result = start;
  			goto share;

  		}

  		/* obtain the address at which to make a shared mapping
  		 * - this is the hook for quasi-memory character devices to
  		 *   tell us the location of a shared mapping
  		 */

  		if (capabilities & NOMMU_MAP_DIRECT) {

  			addr = file->f_op->get_unmapped_area(file, addr, len,
  							     pgoff, flags);

  			if (IS_ERR_VALUE(addr)) {

  				ret = addr;

  				if (ret != -ENOSYS)

  					goto error_just_free;

  
  				/* the driver refused to tell us where to site
  				 * the mapping so we'll have to attempt to copy
  				 * it */

  				ret = -ENODEV;

  				if (!(capabilities & NOMMU_MAP_COPY))

  					goto error_just_free;

  				capabilities &= ~NOMMU_MAP_DIRECT;

  			} else {
  				vma->vm_start = region->vm_start = addr;
  				vma->vm_end = region->vm_end = addr + len;

  			}
  		}
  	}

  	vma->vm_region = region;

  	/* set up the mapping

  	 * - the region is filled in if NOMMU_MAP_DIRECT is still set

  	 */

  	if (file && vma->vm_flags & VM_SHARED)

  		ret = do_mmap_shared_file(vma);

  	else

  		ret = do_mmap_private(vma, region, len, capabilities);

  	if (ret < 0)

  		goto error_just_free;
  	add_nommu_region(region);

  	/* clear anonymous mappings that don't ask for uninitialized data */
  	if (!vma->vm_file && !(flags & MAP_UNINITIALIZED))
  		memset((void *)region->vm_start, 0,
  		       region->vm_end - region->vm_start);

  	/* okay... we have a mapping; now we have to register it */

  	result = vma->vm_start;

  	current->mm->total_vm += len >> PAGE_SHIFT;

  share:
  	add_vma_to_mm(current->mm, vma);

  	/* we flush the region from the icache only when the first executable
  	 * mapping of it is made  */
  	if (vma->vm_flags & VM_EXEC && !region->vm_icache_flushed) {
  		flush_icache_range(region->vm_start, region->vm_end);
  		region->vm_icache_flushed = true;
  	}

  	up_write(&nommu_region_sem);

  	return result;

  error_just_free:
  	up_write(&nommu_region_sem);
  error:

  	if (region->vm_file)
  		fput(region->vm_file);

  	kmem_cache_free(vm_region_jar, region);

  	if (vma->vm_file)
  		fput(vma->vm_file);

  	kmem_cache_free(vm_area_cachep, vma);

  	return ret;
  
  sharing_violation:
  	up_write(&nommu_region_sem);

  	pr_warn("Attempt to share mismatched mappings
  ");

  	ret = -EINVAL;
  	goto error;

  error_getting_vma:
  	kmem_cache_free(vm_region_jar, region);

  	pr_warn("Allocation of vma for %lu byte allocation from process %d failed
  ",
  			len, current->pid);

  	show_free_areas(0);

  	return -ENOMEM;

  error_getting_region:

  	pr_warn("Allocation of vm region for %lu byte allocation from process %d failed
  ",
  			len, current->pid);

  	show_free_areas(0);

  	return -ENOMEM;
  }

  SYSCALL_DEFINE6(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 = -EBADF;

  	audit_mmap_fd(fd, flags);

  	if (!(flags & MAP_ANONYMOUS)) {
  		file = fget(fd);
  		if (!file)
  			goto out;
  	}
  
  	flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);

  	retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);

  
  	if (file)
  		fput(file);
  out:
  	return retval;
  }

  #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 (a.offset & ~PAGE_MASK)
  		return -EINVAL;
  
  	return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
  			      a.offset >> PAGE_SHIFT);
  }
  #endif /* __ARCH_WANT_SYS_OLD_MMAP */

  /*

   * 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)

  {

  	struct vm_area_struct *new;
  	struct vm_region *region;
  	unsigned long npages;

  	/* we're only permitted to split anonymous regions (these should have
  	 * only a single usage on the region) */
  	if (vma->vm_file)

  		return -ENOMEM;

  	if (mm->map_count >= sysctl_max_map_count)
  		return -ENOMEM;

  	region = kmem_cache_alloc(vm_region_jar, GFP_KERNEL);
  	if (!region)
  		return -ENOMEM;

  	new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
  	if (!new) {
  		kmem_cache_free(vm_region_jar, region);
  		return -ENOMEM;
  	}
  
  	/* most fields are the same, copy all, and then fixup */
  	*new = *vma;
  	*region = *vma->vm_region;
  	new->vm_region = region;
  
  	npages = (addr - vma->vm_start) >> PAGE_SHIFT;
  
  	if (new_below) {

  		region->vm_top = region->vm_end = new->vm_end = addr;

  	} else {
  		region->vm_start = new->vm_start = addr;
  		region->vm_pgoff = new->vm_pgoff += npages;

  	}

  
  	if (new->vm_ops && new->vm_ops->open)
  		new->vm_ops->open(new);
  
  	delete_vma_from_mm(vma);
  	down_write(&nommu_region_sem);
  	delete_nommu_region(vma->vm_region);
  	if (new_below) {
  		vma->vm_region->vm_start = vma->vm_start = addr;
  		vma->vm_region->vm_pgoff = vma->vm_pgoff += npages;
  	} else {
  		vma->vm_region->vm_end = vma->vm_end = addr;

  		vma->vm_region->vm_top = addr;

  	}
  	add_nommu_region(vma->vm_region);
  	add_nommu_region(new->vm_region);
  	up_write(&nommu_region_sem);
  	add_vma_to_mm(mm, vma);
  	add_vma_to_mm(mm, new);
  	return 0;

  }

  /*

   * shrink a VMA by removing the specified chunk from either the beginning or
   * the end

   */

  static int shrink_vma(struct mm_struct *mm,
  		      struct vm_area_struct *vma,
  		      unsigned long from, unsigned long to)

  {

  	struct vm_region *region;

  	/* adjust the VMA's pointers, which may reposition it in the MM's tree
  	 * and list */
  	delete_vma_from_mm(vma);
  	if (from > vma->vm_start)
  		vma->vm_end = from;
  	else
  		vma->vm_start = to;
  	add_vma_to_mm(mm, vma);

  	/* cut the backing region down to size */
  	region = vma->vm_region;

  	BUG_ON(region->vm_usage != 1);

  
  	down_write(&nommu_region_sem);
  	delete_nommu_region(region);

  	if (from > region->vm_start) {
  		to = region->vm_top;
  		region->vm_top = region->vm_end = from;
  	} else {

  		region->vm_start = to;

  	}

  	add_nommu_region(region);
  	up_write(&nommu_region_sem);
  
  	free_page_series(from, to);
  	return 0;
  }

  /*
   * release a mapping
   * - under NOMMU conditions the chunk to be unmapped must be backed by a single
   *   VMA, though it need not cover the whole VMA
   */
  int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
  {
  	struct vm_area_struct *vma;

  	unsigned long end;

  	int ret;

  	len = PAGE_ALIGN(len);

  	if (len == 0)
  		return -EINVAL;

  	end = start + len;

  	/* find the first potentially overlapping VMA */
  	vma = find_vma(mm, start);
  	if (!vma) {

  		static int limit;

  		if (limit < 5) {

  			pr_warn("munmap of memory not mmapped by process %d (%s): 0x%lx-0x%lx
  ",
  					current->pid, current->comm,
  					start, start + len - 1);

  			limit++;
  		}

  		return -EINVAL;
  	}

  	/* we're allowed to split an anonymous VMA but not a file-backed one */
  	if (vma->vm_file) {
  		do {

  			if (start > vma->vm_start)

  				return -EINVAL;

  			if (end == vma->vm_end)
  				goto erase_whole_vma;

  			vma = vma->vm_next;
  		} while (vma);

  		return -EINVAL;
  	} else {
  		/* the chunk must be a subset of the VMA found */
  		if (start == vma->vm_start && end == vma->vm_end)
  			goto erase_whole_vma;

  		if (start < vma->vm_start || end > vma->vm_end)

  			return -EINVAL;

  		if (start & ~PAGE_MASK)

  			return -EINVAL;

  		if (end != vma->vm_end && end & ~PAGE_MASK)

  			return -EINVAL;

  		if (start != vma->vm_start && end != vma->vm_end) {
  			ret = split_vma(mm, vma, start, 1);

  			if (ret < 0)

  				return ret;

  		}
  		return shrink_vma(mm, vma, start, end);
  	}

  erase_whole_vma:
  	delete_vma_from_mm(vma);
  	delete_vma(mm, vma);

  	return 0;
  }