/*
   *  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) 2004-2005 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      Paul Mundt <lethal@linux-sh.org>

   */

  #include <linux/module.h>

  #include <linux/mm.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/ptrace.h>
  #include <linux/blkdev.h>
  #include <linux/backing-dev.h>
  #include <linux/mount.h>
  #include <linux/personality.h>
  #include <linux/security.h>
  #include <linux/syscalls.h>
  
  #include <asm/uaccess.h>
  #include <asm/tlb.h>
  #include <asm/tlbflush.h>
  
  void *high_memory;
  struct page *mem_map;
  unsigned long max_mapnr;
  unsigned long num_physpages;
  unsigned long askedalloc, realalloc;
  atomic_t vm_committed_space = ATOMIC_INIT(0);
  int sysctl_overcommit_memory = OVERCOMMIT_GUESS; /* heuristic overcommit */
  int sysctl_overcommit_ratio = 50; /* default is 50% */
  int sysctl_max_map_count = DEFAULT_MAX_MAP_COUNT;
  int heap_stack_gap = 0;
  
  EXPORT_SYMBOL(mem_map);

  EXPORT_SYMBOL(num_physpages);

  
  /* list of shareable VMAs */
  struct rb_root nommu_vma_tree = RB_ROOT;
  DECLARE_RWSEM(nommu_vma_sem);
  
  struct vm_operations_struct generic_file_vm_ops = {
  };
  
  /*
   * Handle all mappings that got truncated by a "truncate()"
   * system call.
   *
   * NOTE! We have to be ready to update the memory sharing
   * between the file and the memory map for a potential last
   * incomplete page.  Ugly, but necessary.
   */
  int vmtruncate(struct inode *inode, loff_t offset)
  {
  	struct address_space *mapping = inode->i_mapping;
  	unsigned long limit;
  
  	if (inode->i_size < offset)
  		goto do_expand;
  	i_size_write(inode, offset);
  
  	truncate_inode_pages(mapping, offset);
  	goto out_truncate;
  
  do_expand:
  	limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
  	if (limit != RLIM_INFINITY && offset > limit)
  		goto out_sig;
  	if (offset > inode->i_sb->s_maxbytes)
  		goto out;
  	i_size_write(inode, offset);
  
  out_truncate:
  	if (inode->i_op && inode->i_op->truncate)
  		inode->i_op->truncate(inode);
  	return 0;
  out_sig:
  	send_sig(SIGXFSZ, current, 0);
  out:
  	return -EFBIG;
  }
  
  EXPORT_SYMBOL(vmtruncate);
  
  /*
   * 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 || (unsigned long)objp >= memory_end || !((page = virt_to_page(objp))))

  		return 0;
  
  	if (PageSlab(page))
  		return ksize(objp);
  
  	BUG_ON(page->index < 0);
  	BUG_ON(page->index >= MAX_ORDER);
  
  	return (PAGE_SIZE << page->index);
  }
  
  /*

   * 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

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

  	struct vm_area_struct *vma;

  	unsigned long vm_flags;
  	int i;
  
  	/* calculate required read or write permissions.
  	 * - if 'force' is set, we only require the "MAY" flags.
  	 */
  	vm_flags  = write ? (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
  	vm_flags &= force ? (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);

  
  	for (i = 0; i < len; 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 += PAGE_SIZE;
  	}

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

  }

  EXPORT_SYMBOL(get_user_pages);

  DEFINE_RWLOCK(vmlist_lock);
  struct vm_struct *vmlist;

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

  /**
   * 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);

  
  /*

   * Implement a stub for vmalloc_sync_all() if the architecture chose not to
   * have one.
   */
  void  __attribute__((weak)) vmalloc_sync_all(void)
  {
  }

  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.
   */
  asmlinkage unsigned long sys_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.
  	 */
  	return mm->brk = brk;
  }
  
  #ifdef DEBUG
  static void show_process_blocks(void)
  {
  	struct vm_list_struct *vml;
  
  	printk("Process blocks %d:", current->pid);
  
  	for (vml = &current->mm->context.vmlist; vml; vml = vml->next) {
  		printk(" %p: %p", vml, vml->vma);
  		if (vml->vma)
  			printk(" (%d @%lx #%d)",
  			       kobjsize((void *) vml->vma->vm_start),
  			       vml->vma->vm_start,
  			       atomic_read(&vml->vma->vm_usage));
  		printk(vml->next ? " ->" : ".
  ");
  	}
  }
  #endif /* DEBUG */

  /*
   * add a VMA into a process's mm_struct in the appropriate place in the list
   * - should be called with mm->mmap_sem held writelocked
   */
  static void add_vma_to_mm(struct mm_struct *mm, struct vm_list_struct *vml)
  {
  	struct vm_list_struct **ppv;
  
  	for (ppv = &current->mm->context.vmlist; *ppv; ppv = &(*ppv)->next)
  		if ((*ppv)->vma->vm_start > vml->vma->vm_start)
  			break;
  
  	vml->next = *ppv;
  	*ppv = vml;
  }
  
  /*
   * 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_list_struct *loop, *vml;
  
  	/* search the vm_start ordered list */
  	vml = NULL;
  	for (loop = mm->context.vmlist; loop; loop = loop->next) {
  		if (loop->vma->vm_start > addr)
  			break;
  		vml = loop;
  	}
  
  	if (vml && vml->vma->vm_end > addr)
  		return vml->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);
  }

  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 inline struct vm_area_struct *find_vma_exact(struct mm_struct *mm,
  						    unsigned long addr)
  {
  	struct vm_list_struct *vml;
  
  	/* search the vm_start ordered list */
  	for (vml = mm->context.vmlist; vml; vml = vml->next) {
  		if (vml->vma->vm_start == addr)
  			return vml->vma;
  		if (vml->vma->vm_start > addr)
  			break;
  	}
  
  	return NULL;
  }
  
  /*

   * find a VMA in the global tree
   */

  static inline struct vm_area_struct *find_nommu_vma(unsigned long start)
  {
  	struct vm_area_struct *vma;
  	struct rb_node *n = nommu_vma_tree.rb_node;
  
  	while (n) {
  		vma = rb_entry(n, struct vm_area_struct, vm_rb);
  
  		if (start < vma->vm_start)
  			n = n->rb_left;
  		else if (start > vma->vm_start)
  			n = n->rb_right;
  		else
  			return vma;
  	}
  
  	return NULL;
  }

  /*
   * add a VMA in the global tree
   */

  static void add_nommu_vma(struct vm_area_struct *vma)
  {
  	struct vm_area_struct *pvma;
  	struct address_space *mapping;
  	struct rb_node **p = &nommu_vma_tree.rb_node;
  	struct rb_node *parent = NULL;
  
  	/* add the VMA to the mapping */
  	if (vma->vm_file) {
  		mapping = vma->vm_file->f_mapping;
  
  		flush_dcache_mmap_lock(mapping);
  		vma_prio_tree_insert(vma, &mapping->i_mmap);
  		flush_dcache_mmap_unlock(mapping);
  	}
  
  	/* add the VMA to the master list */
  	while (*p) {
  		parent = *p;
  		pvma = rb_entry(parent, struct vm_area_struct, vm_rb);
  
  		if (vma->vm_start < pvma->vm_start) {
  			p = &(*p)->rb_left;
  		}
  		else if (vma->vm_start > pvma->vm_start) {
  			p = &(*p)->rb_right;
  		}
  		else {
  			/* mappings are at the same address - this can only
  			 * happen for shared-mem chardevs and shared file
  			 * mappings backed by ramfs/tmpfs */
  			BUG_ON(!(pvma->vm_flags & VM_SHARED));
  
  			if (vma < pvma)
  				p = &(*p)->rb_left;
  			else if (vma > pvma)
  				p = &(*p)->rb_right;
  			else
  				BUG();
  		}
  	}
  
  	rb_link_node(&vma->vm_rb, parent, p);
  	rb_insert_color(&vma->vm_rb, &nommu_vma_tree);
  }

  /*
   * delete a VMA from the global list
   */

  static void delete_nommu_vma(struct vm_area_struct *vma)
  {
  	struct address_space *mapping;
  
  	/* remove the VMA from the mapping */
  	if (vma->vm_file) {
  		mapping = vma->vm_file->f_mapping;
  
  		flush_dcache_mmap_lock(mapping);
  		vma_prio_tree_remove(vma, &mapping->i_mmap);
  		flush_dcache_mmap_unlock(mapping);
  	}
  
  	/* remove from the master list */
  	rb_erase(&vma->vm_rb, &nommu_vma_tree);
  }
  
  /*
   * 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;
  	unsigned long reqprot = prot;
  	int ret;
  
  	/* do the simple checks first */
  	if (flags & MAP_FIXED || addr) {
  		printk(KERN_DEBUG
  		       "%d: Can't do fixed-address/overlay mmap of RAM
  ",
  		       current->pid);
  		return -EINVAL;
  	}
  
  	if ((flags & MAP_TYPE) != MAP_PRIVATE &&
  	    (flags & MAP_TYPE) != MAP_SHARED)
  		return -EINVAL;

  	if (!len)

  		return -EINVAL;

  	/* Careful about overflows.. */
  	len = PAGE_ALIGN(len);
  	if (!len || len > TASK_SIZE)
  		return -ENOMEM;

  	/* offset overflow? */
  	if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)

  		return -EOVERFLOW;

  
  	if (file) {
  		/* validate file mapping requests */
  		struct address_space *mapping;
  
  		/* files must support mmap */
  		if (!file->f_op || !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
  		 */
  		mapping = file->f_mapping;
  		if (!mapping)

  			mapping = file->f_path.dentry->d_inode->i_mapping;

  
  		capabilities = 0;
  		if (mapping && mapping->backing_dev_info)
  			capabilities = mapping->backing_dev_info->capabilities;
  
  		if (!capabilities) {
  			/* no explicit capabilities set, so assume some
  			 * defaults */

  			switch (file->f_path.dentry->d_inode->i_mode & S_IFMT) {

  			case S_IFREG:
  			case S_IFBLK:
  				capabilities = BDI_CAP_MAP_COPY;
  				break;
  
  			case S_IFCHR:
  				capabilities =
  					BDI_CAP_MAP_DIRECT |
  					BDI_CAP_READ_MAP |
  					BDI_CAP_WRITE_MAP;
  				break;
  
  			default:
  				return -EINVAL;
  			}
  		}
  
  		/* eliminate any capabilities that we can't support on this
  		 * device */
  		if (!file->f_op->get_unmapped_area)
  			capabilities &= ~BDI_CAP_MAP_DIRECT;
  		if (!file->f_op->read)
  			capabilities &= ~BDI_CAP_MAP_COPY;
  
  		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->f_path.dentry->d_inode) &&

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

  			if (locks_verify_locked(file->f_path.dentry->d_inode))

  				return -EAGAIN;
  
  			if (!(capabilities & BDI_CAP_MAP_DIRECT))
  				return -ENODEV;
  
  			if (((prot & PROT_READ)  && !(capabilities & BDI_CAP_READ_MAP))  ||
  			    ((prot & PROT_WRITE) && !(capabilities & BDI_CAP_WRITE_MAP)) ||
  			    ((prot & PROT_EXEC)  && !(capabilities & BDI_CAP_EXEC_MAP))
  			    ) {
  				printk("MAP_SHARED not completely supported on !MMU
  ");
  				return -EINVAL;
  			}
  
  			/* we mustn't privatise shared mappings */
  			capabilities &= ~BDI_CAP_MAP_COPY;
  		}
  		else {
  			/* we're going to read the file into private memory we
  			 * allocate */
  			if (!(capabilities & BDI_CAP_MAP_COPY))
  				return -ENODEV;
  
  			/* we don't permit a private writable mapping to be
  			 * shared with the backing device */
  			if (prot & PROT_WRITE)
  				capabilities &= ~BDI_CAP_MAP_DIRECT;
  		}
  
  		/* 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 & BDI_CAP_EXEC_MAP)
  					prot |= PROT_EXEC;
  			}
  		}
  		else if ((prot & PROT_READ) &&
  			 (prot & PROT_EXEC) &&
  			 !(capabilities & BDI_CAP_EXEC_MAP)
  			 ) {
  			/* backing file is not executable, try to copy */
  			capabilities &= ~BDI_CAP_MAP_DIRECT;
  		}
  	}
  	else {
  		/* anonymous mappings are always memory backed and can be
  		 * privately mapped
  		 */
  		capabilities = BDI_CAP_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_file_mmap(file, reqprot, prot, flags, addr, 0);

  	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 |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
  	/* vm_flags |= mm->def_flags; */
  
  	if (!(capabilities & BDI_CAP_MAP_DIRECT)) {
  		/* attempt to share read-only copies of mapped file chunks */
  		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 */
  		if (flags & MAP_SHARED)
  			vm_flags |= VM_MAYSHARE | VM_SHARED;
  		else if ((((vm_flags & capabilities) ^ vm_flags) & BDI_CAP_VMFLAGS) == 0)
  			vm_flags |= VM_MAYSHARE;
  	}
  
  	/* 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 & PT_PTRACED))
  		vm_flags &= ~VM_MAYSHARE;
  
  	return vm_flags;
  }
  
  /*
   * set up a shared mapping on a file
   */
  static int do_mmap_shared_file(struct vm_area_struct *vma, unsigned long len)
  {
  	int ret;
  
  	ret = vma->vm_file->f_op->mmap(vma->vm_file, vma);
  	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 fall
  	 * through to making a private copy of the data and mapping
  	 * that if we can */
  	return -ENODEV;
  }
  
  /*
   * set up a private mapping or an anonymous shared mapping
   */
  static int do_mmap_private(struct vm_area_struct *vma, unsigned long len)
  {
  	void *base;
  	int ret;
  
  	/* 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 (vma->vm_file) {
  		ret = vma->vm_file->f_op->mmap(vma->vm_file, vma);
  		if (ret != -ENOSYS) {
  			/* shouldn't return success if we're not sharing */
  			BUG_ON(ret == 0 && !(vma->vm_flags & VM_MAYSHARE));
  			return ret; /* success or a real error */
  		}
  
  		/* 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
  	 */

  	base = kmalloc(len, GFP_KERNEL|__GFP_COMP);

  	if (!base)
  		goto enomem;
  
  	vma->vm_start = (unsigned long) base;
  	vma->vm_end = vma->vm_start + len;
  	vma->vm_flags |= VM_MAPPED_COPY;
  
  #ifdef WARN_ON_SLACK
  	if (len + WARN_ON_SLACK <= kobjsize(result))
  		printk("Allocation of %lu bytes from process %d has %lu bytes of slack
  ",
  		       len, current->pid, kobjsize(result) - len);
  #endif
  
  	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 = vma->vm_file->f_op->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);
  
  	} else {
  		/* if it's an anonymous mapping, then just clear it */
  		memset(base, 0, len);
  	}
  
  	return 0;
  
  error_free:
  	kfree(base);
  	vma->vm_start = 0;
  	return ret;
  
  enomem:
  	printk("Allocation of length %lu from process %d failed
  ",
  	       len, current->pid);
  	show_free_areas();
  	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)
  {
  	struct vm_list_struct *vml = NULL;
  	struct vm_area_struct *vma = NULL;
  	struct rb_node *rb;
  	unsigned long capabilities, vm_flags;
  	void *result;
  	int ret;

  	if (!(flags & MAP_FIXED))
  		addr = round_hint_to_min(addr);

  	/* 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'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 if it works */

  	vml = kzalloc(sizeof(struct vm_list_struct), GFP_KERNEL);

  	if (!vml)
  		goto error_getting_vml;

  
  	down_write(&nommu_vma_sem);
  
  	/* if we want to share, we need to check for VMAs created by other
  	 * mmap() calls that overlap with our proposed mapping
  	 * - we can only share with an exact 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) {
  		unsigned long pglen = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
  		unsigned long vmpglen;

  		/* suppress VMA sharing for shared regions */
  		if (vm_flags & VM_SHARED &&
  		    capabilities & BDI_CAP_MAP_DIRECT)
  			goto dont_share_VMAs;

  		for (rb = rb_first(&nommu_vma_tree); rb; rb = rb_next(rb)) {
  			vma = rb_entry(rb, struct vm_area_struct, vm_rb);
  
  			if (!(vma->vm_flags & VM_MAYSHARE))
  				continue;
  
  			/* search for overlapping mappings on the same file */

  			if (vma->vm_file->f_path.dentry->d_inode != file->f_path.dentry->d_inode)

  				continue;
  
  			if (vma->vm_pgoff >= pgoff + pglen)
  				continue;
  
  			vmpglen = vma->vm_end - vma->vm_start + PAGE_SIZE - 1;
  			vmpglen >>= PAGE_SHIFT;
  			if (pgoff >= vma->vm_pgoff + vmpglen)
  				continue;
  
  			/* handle inexactly overlapping matches between mappings */
  			if (vma->vm_pgoff != pgoff || vmpglen != pglen) {
  				if (!(capabilities & BDI_CAP_MAP_DIRECT))
  					goto sharing_violation;
  				continue;
  			}
  
  			/* we've found a VMA we can share */
  			atomic_inc(&vma->vm_usage);
  
  			vml->vma = vma;
  			result = (void *) vma->vm_start;
  			goto shared;
  		}

  	dont_share_VMAs:

  		vma = NULL;
  
  		/* 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 (file && file->f_op->get_unmapped_area) {
  			addr = file->f_op->get_unmapped_area(file, addr, len,
  							     pgoff, flags);
  			if (IS_ERR((void *) addr)) {
  				ret = addr;
  				if (ret != (unsigned long) -ENOSYS)
  					goto error;
  
  				/* the driver refused to tell us where to site
  				 * the mapping so we'll have to attempt to copy
  				 * it */
  				ret = (unsigned long) -ENODEV;
  				if (!(capabilities & BDI_CAP_MAP_COPY))
  					goto error;
  
  				capabilities &= ~BDI_CAP_MAP_DIRECT;
  			}
  		}
  	}
  
  	/* we're going to need a VMA struct as well */

  	vma = kzalloc(sizeof(struct vm_area_struct), GFP_KERNEL);

  	if (!vma)
  		goto error_getting_vma;

  	INIT_LIST_HEAD(&vma->anon_vma_node);
  	atomic_set(&vma->vm_usage, 1);

  	if (file) {

  		get_file(file);

  		if (vm_flags & VM_EXECUTABLE) {
  			added_exe_file_vma(current->mm);
  			vma->vm_mm = current->mm;
  		}
  	}

  	vma->vm_file	= file;
  	vma->vm_flags	= vm_flags;
  	vma->vm_start	= addr;
  	vma->vm_end	= addr + len;
  	vma->vm_pgoff	= pgoff;
  
  	vml->vma = vma;
  
  	/* set up the mapping */
  	if (file && vma->vm_flags & VM_SHARED)
  		ret = do_mmap_shared_file(vma, len);
  	else
  		ret = do_mmap_private(vma, len);
  	if (ret < 0)
  		goto error;
  
  	/* okay... we have a mapping; now we have to register it */
  	result = (void *) vma->vm_start;
  
  	if (vma->vm_flags & VM_MAPPED_COPY) {
  		realalloc += kobjsize(result);
  		askedalloc += len;
  	}
  
  	realalloc += kobjsize(vma);
  	askedalloc += sizeof(*vma);
  
  	current->mm->total_vm += len >> PAGE_SHIFT;
  
  	add_nommu_vma(vma);
  
   shared:
  	realalloc += kobjsize(vml);
  	askedalloc += sizeof(*vml);

  	add_vma_to_mm(current->mm, vml);

  
  	up_write(&nommu_vma_sem);
  
  	if (prot & PROT_EXEC)
  		flush_icache_range((unsigned long) result,
  				   (unsigned long) result + len);
  
  #ifdef DEBUG
  	printk("do_mmap:
  ");
  	show_process_blocks();
  #endif
  
  	return (unsigned long) result;
  
   error:
  	up_write(&nommu_vma_sem);
  	kfree(vml);
  	if (vma) {

  		if (vma->vm_file) {

  			fput(vma->vm_file);

  			if (vma->vm_flags & VM_EXECUTABLE)
  				removed_exe_file_vma(vma->vm_mm);
  		}

  		kfree(vma);
  	}
  	return ret;
  
   sharing_violation:
  	up_write(&nommu_vma_sem);
  	printk("Attempt to share mismatched mappings
  ");
  	kfree(vml);
  	return -EINVAL;
  
   error_getting_vma:
  	up_write(&nommu_vma_sem);
  	kfree(vml);

  	printk("Allocation of vma for %lu byte allocation from process %d failed
  ",

  	       len, current->pid);
  	show_free_areas();
  	return -ENOMEM;
  
   error_getting_vml:
  	printk("Allocation of vml for %lu byte allocation from process %d failed
  ",
  	       len, current->pid);
  	show_free_areas();
  	return -ENOMEM;
  }

  EXPORT_SYMBOL(do_mmap_pgoff);

  
  /*
   * handle mapping disposal for uClinux
   */

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

  {
  	if (vma) {
  		down_write(&nommu_vma_sem);
  
  		if (atomic_dec_and_test(&vma->vm_usage)) {
  			delete_nommu_vma(vma);
  
  			if (vma->vm_ops && vma->vm_ops->close)
  				vma->vm_ops->close(vma);
  
  			/* IO memory and memory shared directly out of the pagecache from
  			 * ramfs/tmpfs mustn't be released here */
  			if (vma->vm_flags & VM_MAPPED_COPY) {
  				realalloc -= kobjsize((void *) vma->vm_start);
  				askedalloc -= vma->vm_end - vma->vm_start;
  				kfree((void *) vma->vm_start);
  			}
  
  			realalloc -= kobjsize(vma);
  			askedalloc -= sizeof(*vma);

  			if (vma->vm_file) {

  				fput(vma->vm_file);

  				if (vma->vm_flags & VM_EXECUTABLE)
  					removed_exe_file_vma(mm);
  			}

  			kfree(vma);
  		}
  
  		up_write(&nommu_vma_sem);
  	}
  }

  /*
   * release a mapping
   * - under NOMMU conditions the parameters must match exactly to the mapping to
   *   be removed
   */

  int do_munmap(struct mm_struct *mm, unsigned long addr, size_t len)
  {
  	struct vm_list_struct *vml, **parent;
  	unsigned long end = addr + len;
  
  #ifdef DEBUG
  	printk("do_munmap:
  ");
  #endif

  	for (parent = &mm->context.vmlist; *parent; parent = &(*parent)->next) {
  		if ((*parent)->vma->vm_start > addr)
  			break;

  		if ((*parent)->vma->vm_start == addr &&

  		    ((len == 0) || ((*parent)->vma->vm_end == end)))

  			goto found;

  	}

  
  	printk("munmap of non-mmaped memory by process %d (%s): %p
  ",
  	       current->pid, current->comm, (void *) addr);
  	return -EINVAL;
  
   found:
  	vml = *parent;

  	put_vma(mm, vml->vma);

  
  	*parent = vml->next;
  	realalloc -= kobjsize(vml);
  	askedalloc -= sizeof(*vml);
  	kfree(vml);

  
  	update_hiwater_vm(mm);

  	mm->total_vm -= len >> PAGE_SHIFT;
  
  #ifdef DEBUG
  	show_process_blocks();
  #endif
  
  	return 0;
  }

  EXPORT_SYMBOL(do_munmap);

  asmlinkage long sys_munmap(unsigned long addr, size_t len)
  {
  	int ret;
  	struct mm_struct *mm = current->mm;
  
  	down_write(&mm->mmap_sem);
  	ret = do_munmap(mm, addr, len);
  	up_write(&mm->mmap_sem);
  	return ret;
  }
  
  /*
   * Release all mappings
   */

  void exit_mmap(struct mm_struct * mm)
  {
  	struct vm_list_struct *tmp;
  
  	if (mm) {
  #ifdef DEBUG
  		printk("Exit_mmap:
  ");
  #endif
  
  		mm->total_vm = 0;
  
  		while ((tmp = mm->context.vmlist)) {
  			mm->context.vmlist = tmp->next;

  			put_vma(mm, tmp->vma);

  
  			realalloc -= kobjsize(tmp);
  			askedalloc -= sizeof(*tmp);
  			kfree(tmp);
  		}
  
  #ifdef DEBUG
  		show_process_blocks();
  #endif
  	}
  }

  unsigned long do_brk(unsigned long addr, unsigned long len)
  {
  	return -ENOMEM;
  }
  
  /*

   * expand (or shrink) an existing mapping, potentially moving it at the same
   * time (controlled by the MREMAP_MAYMOVE flag and available VM space)

   *

   * under NOMMU conditions, we only permit changing a mapping's size, and only
   * as long as it stays within the hole allocated by the kmalloc() call in
   * do_mmap_pgoff() and the block is not shareable

   *

   * MREMAP_FIXED is not supported under NOMMU conditions

   */
  unsigned long do_mremap(unsigned long addr,
  			unsigned long old_len, unsigned long new_len,
  			unsigned long flags, unsigned long new_addr)
  {

  	struct vm_area_struct *vma;

  
  	/* insanity checks first */
  	if (new_len == 0)
  		return (unsigned long) -EINVAL;
  
  	if (flags & MREMAP_FIXED && new_addr != addr)
  		return (unsigned long) -EINVAL;

  	vma = find_vma_exact(current->mm, addr);
  	if (!vma)
  		return (unsigned long) -EINVAL;

  	if (vma->vm_end != vma->vm_start + old_len)

  		return (unsigned long) -EFAULT;

  	if (vma->vm_flags & VM_MAYSHARE)

  		return (unsigned long) -EPERM;
  
  	if (new_len > kobjsize((void *) addr))
  		return (unsigned long) -ENOMEM;
  
  	/* all checks complete - do it */

  	vma->vm_end = vma->vm_start + new_len;

  
  	askedalloc -= old_len;
  	askedalloc += new_len;

  	return vma->vm_start;
  }

  EXPORT_SYMBOL(do_mremap);

  
  asmlinkage unsigned long sys_mremap(unsigned long addr,
  	unsigned long old_len, unsigned long new_len,
  	unsigned long flags, unsigned long new_addr)
  {
  	unsigned long ret;
  
  	down_write(&current->mm->mmap_sem);
  	ret = do_mremap(addr, old_len, new_len, flags, new_addr);
  	up_write(&current->mm->mmap_sem);
  	return ret;

  }

  struct page *follow_page(struct vm_area_struct *vma, unsigned long address,

  			unsigned int foll_flags)

  {
  	return NULL;
  }

  int remap_pfn_range(struct vm_area_struct *vma, unsigned long from,
  		unsigned long to, unsigned long size, pgprot_t prot)
  {

  	vma->vm_start = vma->vm_pgoff << PAGE_SHIFT;
  	return 0;

  }

  EXPORT_SYMBOL(remap_pfn_range);

  int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
  			unsigned long pgoff)
  {
  	unsigned int size = vma->vm_end - vma->vm_start;
  
  	if (!(vma->vm_flags & VM_USERMAP))
  		return -EINVAL;
  
  	vma->vm_start = (unsigned long)(addr + (pgoff << PAGE_SHIFT));
  	vma->vm_end = vma->vm_start + size;
  
  	return 0;
  }
  EXPORT_SYMBOL(remap_vmalloc_range);

  void swap_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
  {
  }
  
  unsigned long arch_get_unmapped_area(struct file *file, unsigned long addr,
  	unsigned long len, unsigned long pgoff, unsigned long flags)
  {
  	return -ENOMEM;
  }

  void arch_unmap_area(struct mm_struct *mm, unsigned long addr)

  {
  }

  void unmap_mapping_range(struct address_space *mapping,
  			 loff_t const holebegin, loff_t const holelen,
  			 int even_cows)
  {
  }

  EXPORT_SYMBOL(unmap_mapping_range);

  
  /*

   * ask for an unmapped area at which to create a mapping on a file
   */
  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);
  
  	get_area = current->mm->get_unmapped_area;
  	if (file && file->f_op && file->f_op->get_unmapped_area)
  		get_area = file->f_op->get_unmapped_area;
  
  	if (!get_area)
  		return -ENOSYS;
  
  	return get_area(file, addr, len, pgoff, flags);
  }

  EXPORT_SYMBOL(get_unmapped_area);
  
  /*

   * Check that a process has enough memory to allocate a new virtual
   * mapping. 0 means there is enough memory for the allocation to
   * succeed and -ENOMEM implies there is not.
   *
   * We currently support three overcommit policies, which are set via the
   * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-accounting
   *
   * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
   * Additional code 2002 Jul 20 by Robert Love.
   *
   * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
   *
   * Note this is a helper function intended to be used by LSMs which
   * wish to use this logic.
   */

  int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)

  {
  	unsigned long free, allowed;
  
  	vm_acct_memory(pages);
  
  	/*
  	 * Sometimes we want to use more memory than we have
  	 */
  	if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
  		return 0;
  
  	if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
  		unsigned long n;

  		free = global_page_state(NR_FILE_PAGES);

  		free += nr_swap_pages;
  
  		/*
  		 * Any slabs which are created with the
  		 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
  		 * which are reclaimable, under pressure.  The dentry
  		 * cache and most inode caches should fall into this
  		 */

  		free += global_page_state(NR_SLAB_RECLAIMABLE);

  
  		/*
  		 * Leave the last 3% for root
  		 */
  		if (!cap_sys_admin)
  			free -= free / 32;
  
  		if (free > pages)
  			return 0;
  
  		/*
  		 * nr_free_pages() is very expensive on large systems,
  		 * only call if we're about to fail.
  		 */
  		n = nr_free_pages();

  
  		/*
  		 * Leave reserved pages. The pages are not for anonymous pages.
  		 */
  		if (n <= totalreserve_pages)
  			goto error;
  		else
  			n -= totalreserve_pages;
  
  		/*
  		 * Leave the last 3% for root
  		 */

  		if (!cap_sys_admin)
  			n -= n / 32;
  		free += n;
  
  		if (free > pages)
  			return 0;

  
  		goto error;

  	}
  
  	allowed = totalram_pages * sysctl_overcommit_ratio / 100;
  	/*
  	 * Leave the last 3% for root
  	 */
  	if (!cap_sys_admin)
  		allowed -= allowed / 32;
  	allowed += total_swap_pages;
  
  	/* Don't let a single process grow too big:
  	   leave 3% of the size of this process for other processes */
  	allowed -= current->mm->total_vm / 32;

  	/*
  	 * cast `allowed' as a signed long because vm_committed_space
  	 * sometimes has a negative value
  	 */
  	if (atomic_read(&vm_committed_space) < (long)allowed)

  		return 0;

  error:

  	vm_unacct_memory(pages);
  
  	return -ENOMEM;
  }
  
  int in_gate_area_no_task(unsigned long addr)
  {
  	return 0;
  }

  int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)

  {
  	BUG();

  	return 0;

  }

  EXPORT_SYMBOL(filemap_fault);

  
  /*
   * Access another process' address space.
   * - source/target buffer must be kernel space
   */
  int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
  {

  	struct vm_area_struct *vma;
  	struct mm_struct *mm;
  
  	if (addr + len < addr)
  		return 0;
  
  	mm = get_task_mm(tsk);
  	if (!mm)
  		return 0;
  
  	down_read(&mm->mmap_sem);
  
  	/* the access must start within one of the target process's mappings */

  	vma = find_vma(mm, addr);
  	if (vma) {

  		/* don't overrun this mapping */
  		if (addr + len >= vma->vm_end)
  			len = vma->vm_end - addr;
  
  		/* only read or write mappings where it is permitted */

  		if (write && vma->vm_flags & VM_MAYWRITE)

  			len -= copy_to_user((void *) addr, buf, len);

  		else if (!write && vma->vm_flags & VM_MAYREAD)

  			len -= copy_from_user(buf, (void *) addr, len);
  		else
  			len = 0;
  	} else {
  		len = 0;
  	}
  
  	up_read(&mm->mmap_sem);
  	mmput(mm);
  	return len;
  }