xref: /openbmc/linux/mm/nommu.c (revision 97da55fc)
1 /*
2  *  linux/mm/nommu.c
3  *
4  *  Replacement code for mm functions to support CPU's that don't
5  *  have any form of memory management unit (thus no virtual memory).
6  *
7  *  See Documentation/nommu-mmap.txt
8  *
9  *  Copyright (c) 2004-2008 David Howells <dhowells@redhat.com>
10  *  Copyright (c) 2000-2003 David McCullough <davidm@snapgear.com>
11  *  Copyright (c) 2000-2001 D Jeff Dionne <jeff@uClinux.org>
12  *  Copyright (c) 2002      Greg Ungerer <gerg@snapgear.com>
13  *  Copyright (c) 2007-2010 Paul Mundt <lethal@linux-sh.org>
14  */
15 
16 #include <linux/export.h>
17 #include <linux/mm.h>
18 #include <linux/mman.h>
19 #include <linux/swap.h>
20 #include <linux/file.h>
21 #include <linux/highmem.h>
22 #include <linux/pagemap.h>
23 #include <linux/slab.h>
24 #include <linux/vmalloc.h>
25 #include <linux/blkdev.h>
26 #include <linux/backing-dev.h>
27 #include <linux/mount.h>
28 #include <linux/personality.h>
29 #include <linux/security.h>
30 #include <linux/syscalls.h>
31 #include <linux/audit.h>
32 #include <linux/sched/sysctl.h>
33 
34 #include <asm/uaccess.h>
35 #include <asm/tlb.h>
36 #include <asm/tlbflush.h>
37 #include <asm/mmu_context.h>
38 #include "internal.h"
39 
40 #if 0
41 #define kenter(FMT, ...) \
42 	printk(KERN_DEBUG "==> %s("FMT")\n", __func__, ##__VA_ARGS__)
43 #define kleave(FMT, ...) \
44 	printk(KERN_DEBUG "<== %s()"FMT"\n", __func__, ##__VA_ARGS__)
45 #define kdebug(FMT, ...) \
46 	printk(KERN_DEBUG "xxx" FMT"yyy\n", ##__VA_ARGS__)
47 #else
48 #define kenter(FMT, ...) \
49 	no_printk(KERN_DEBUG "==> %s("FMT")\n", __func__, ##__VA_ARGS__)
50 #define kleave(FMT, ...) \
51 	no_printk(KERN_DEBUG "<== %s()"FMT"\n", __func__, ##__VA_ARGS__)
52 #define kdebug(FMT, ...) \
53 	no_printk(KERN_DEBUG FMT"\n", ##__VA_ARGS__)
54 #endif
55 
56 void *high_memory;
57 struct page *mem_map;
58 unsigned long max_mapnr;
59 unsigned long num_physpages;
60 unsigned long highest_memmap_pfn;
61 struct percpu_counter vm_committed_as;
62 int sysctl_overcommit_memory = OVERCOMMIT_GUESS; /* heuristic overcommit */
63 int sysctl_overcommit_ratio = 50; /* default is 50% */
64 int sysctl_max_map_count = DEFAULT_MAX_MAP_COUNT;
65 int sysctl_nr_trim_pages = CONFIG_NOMMU_INITIAL_TRIM_EXCESS;
66 int heap_stack_gap = 0;
67 
68 atomic_long_t mmap_pages_allocated;
69 
70 /*
71  * The global memory commitment made in the system can be a metric
72  * that can be used to drive ballooning decisions when Linux is hosted
73  * as a guest. On Hyper-V, the host implements a policy engine for dynamically
74  * balancing memory across competing virtual machines that are hosted.
75  * Several metrics drive this policy engine including the guest reported
76  * memory commitment.
77  */
78 unsigned long vm_memory_committed(void)
79 {
80 	return percpu_counter_read_positive(&vm_committed_as);
81 }
82 
83 EXPORT_SYMBOL_GPL(vm_memory_committed);
84 
85 EXPORT_SYMBOL(mem_map);
86 EXPORT_SYMBOL(num_physpages);
87 
88 /* list of mapped, potentially shareable regions */
89 static struct kmem_cache *vm_region_jar;
90 struct rb_root nommu_region_tree = RB_ROOT;
91 DECLARE_RWSEM(nommu_region_sem);
92 
93 const struct vm_operations_struct generic_file_vm_ops = {
94 };
95 
96 /*
97  * Return the total memory allocated for this pointer, not
98  * just what the caller asked for.
99  *
100  * Doesn't have to be accurate, i.e. may have races.
101  */
102 unsigned int kobjsize(const void *objp)
103 {
104 	struct page *page;
105 
106 	/*
107 	 * If the object we have should not have ksize performed on it,
108 	 * return size of 0
109 	 */
110 	if (!objp || !virt_addr_valid(objp))
111 		return 0;
112 
113 	page = virt_to_head_page(objp);
114 
115 	/*
116 	 * If the allocator sets PageSlab, we know the pointer came from
117 	 * kmalloc().
118 	 */
119 	if (PageSlab(page))
120 		return ksize(objp);
121 
122 	/*
123 	 * If it's not a compound page, see if we have a matching VMA
124 	 * region. This test is intentionally done in reverse order,
125 	 * so if there's no VMA, we still fall through and hand back
126 	 * PAGE_SIZE for 0-order pages.
127 	 */
128 	if (!PageCompound(page)) {
129 		struct vm_area_struct *vma;
130 
131 		vma = find_vma(current->mm, (unsigned long)objp);
132 		if (vma)
133 			return vma->vm_end - vma->vm_start;
134 	}
135 
136 	/*
137 	 * The ksize() function is only guaranteed to work for pointers
138 	 * returned by kmalloc(). So handle arbitrary pointers here.
139 	 */
140 	return PAGE_SIZE << compound_order(page);
141 }
142 
143 long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
144 		      unsigned long start, unsigned long nr_pages,
145 		      unsigned int foll_flags, struct page **pages,
146 		      struct vm_area_struct **vmas, int *nonblocking)
147 {
148 	struct vm_area_struct *vma;
149 	unsigned long vm_flags;
150 	int i;
151 
152 	/* calculate required read or write permissions.
153 	 * If FOLL_FORCE is set, we only require the "MAY" flags.
154 	 */
155 	vm_flags  = (foll_flags & FOLL_WRITE) ?
156 			(VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
157 	vm_flags &= (foll_flags & FOLL_FORCE) ?
158 			(VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
159 
160 	for (i = 0; i < nr_pages; i++) {
161 		vma = find_vma(mm, start);
162 		if (!vma)
163 			goto finish_or_fault;
164 
165 		/* protect what we can, including chardevs */
166 		if ((vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
167 		    !(vm_flags & vma->vm_flags))
168 			goto finish_or_fault;
169 
170 		if (pages) {
171 			pages[i] = virt_to_page(start);
172 			if (pages[i])
173 				page_cache_get(pages[i]);
174 		}
175 		if (vmas)
176 			vmas[i] = vma;
177 		start = (start + PAGE_SIZE) & PAGE_MASK;
178 	}
179 
180 	return i;
181 
182 finish_or_fault:
183 	return i ? : -EFAULT;
184 }
185 
186 /*
187  * get a list of pages in an address range belonging to the specified process
188  * and indicate the VMA that covers each page
189  * - this is potentially dodgy as we may end incrementing the page count of a
190  *   slab page or a secondary page from a compound page
191  * - don't permit access to VMAs that don't support it, such as I/O mappings
192  */
193 long get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
194 		    unsigned long start, unsigned long nr_pages,
195 		    int write, int force, struct page **pages,
196 		    struct vm_area_struct **vmas)
197 {
198 	int flags = 0;
199 
200 	if (write)
201 		flags |= FOLL_WRITE;
202 	if (force)
203 		flags |= FOLL_FORCE;
204 
205 	return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas,
206 				NULL);
207 }
208 EXPORT_SYMBOL(get_user_pages);
209 
210 /**
211  * follow_pfn - look up PFN at a user virtual address
212  * @vma: memory mapping
213  * @address: user virtual address
214  * @pfn: location to store found PFN
215  *
216  * Only IO mappings and raw PFN mappings are allowed.
217  *
218  * Returns zero and the pfn at @pfn on success, -ve otherwise.
219  */
220 int follow_pfn(struct vm_area_struct *vma, unsigned long address,
221 	unsigned long *pfn)
222 {
223 	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
224 		return -EINVAL;
225 
226 	*pfn = address >> PAGE_SHIFT;
227 	return 0;
228 }
229 EXPORT_SYMBOL(follow_pfn);
230 
231 DEFINE_RWLOCK(vmlist_lock);
232 struct vm_struct *vmlist;
233 
234 void vfree(const void *addr)
235 {
236 	kfree(addr);
237 }
238 EXPORT_SYMBOL(vfree);
239 
240 void *__vmalloc(unsigned long size, gfp_t gfp_mask, pgprot_t prot)
241 {
242 	/*
243 	 *  You can't specify __GFP_HIGHMEM with kmalloc() since kmalloc()
244 	 * returns only a logical address.
245 	 */
246 	return kmalloc(size, (gfp_mask | __GFP_COMP) & ~__GFP_HIGHMEM);
247 }
248 EXPORT_SYMBOL(__vmalloc);
249 
250 void *vmalloc_user(unsigned long size)
251 {
252 	void *ret;
253 
254 	ret = __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
255 			PAGE_KERNEL);
256 	if (ret) {
257 		struct vm_area_struct *vma;
258 
259 		down_write(&current->mm->mmap_sem);
260 		vma = find_vma(current->mm, (unsigned long)ret);
261 		if (vma)
262 			vma->vm_flags |= VM_USERMAP;
263 		up_write(&current->mm->mmap_sem);
264 	}
265 
266 	return ret;
267 }
268 EXPORT_SYMBOL(vmalloc_user);
269 
270 struct page *vmalloc_to_page(const void *addr)
271 {
272 	return virt_to_page(addr);
273 }
274 EXPORT_SYMBOL(vmalloc_to_page);
275 
276 unsigned long vmalloc_to_pfn(const void *addr)
277 {
278 	return page_to_pfn(virt_to_page(addr));
279 }
280 EXPORT_SYMBOL(vmalloc_to_pfn);
281 
282 long vread(char *buf, char *addr, unsigned long count)
283 {
284 	memcpy(buf, addr, count);
285 	return count;
286 }
287 
288 long vwrite(char *buf, char *addr, unsigned long count)
289 {
290 	/* Don't allow overflow */
291 	if ((unsigned long) addr + count < count)
292 		count = -(unsigned long) addr;
293 
294 	memcpy(addr, buf, count);
295 	return(count);
296 }
297 
298 /*
299  *	vmalloc  -  allocate virtually continguos memory
300  *
301  *	@size:		allocation size
302  *
303  *	Allocate enough pages to cover @size from the page level
304  *	allocator and map them into continguos kernel virtual space.
305  *
306  *	For tight control over page level allocator and protection flags
307  *	use __vmalloc() instead.
308  */
309 void *vmalloc(unsigned long size)
310 {
311        return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL);
312 }
313 EXPORT_SYMBOL(vmalloc);
314 
315 /*
316  *	vzalloc - allocate virtually continguos memory with zero fill
317  *
318  *	@size:		allocation size
319  *
320  *	Allocate enough pages to cover @size from the page level
321  *	allocator and map them into continguos kernel virtual space.
322  *	The memory allocated is set to zero.
323  *
324  *	For tight control over page level allocator and protection flags
325  *	use __vmalloc() instead.
326  */
327 void *vzalloc(unsigned long size)
328 {
329 	return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
330 			PAGE_KERNEL);
331 }
332 EXPORT_SYMBOL(vzalloc);
333 
334 /**
335  * vmalloc_node - allocate memory on a specific node
336  * @size:	allocation size
337  * @node:	numa node
338  *
339  * Allocate enough pages to cover @size from the page level
340  * allocator and map them into contiguous kernel virtual space.
341  *
342  * For tight control over page level allocator and protection flags
343  * use __vmalloc() instead.
344  */
345 void *vmalloc_node(unsigned long size, int node)
346 {
347 	return vmalloc(size);
348 }
349 EXPORT_SYMBOL(vmalloc_node);
350 
351 /**
352  * vzalloc_node - allocate memory on a specific node with zero fill
353  * @size:	allocation size
354  * @node:	numa node
355  *
356  * Allocate enough pages to cover @size from the page level
357  * allocator and map them into contiguous kernel virtual space.
358  * The memory allocated is set to zero.
359  *
360  * For tight control over page level allocator and protection flags
361  * use __vmalloc() instead.
362  */
363 void *vzalloc_node(unsigned long size, int node)
364 {
365 	return vzalloc(size);
366 }
367 EXPORT_SYMBOL(vzalloc_node);
368 
369 #ifndef PAGE_KERNEL_EXEC
370 # define PAGE_KERNEL_EXEC PAGE_KERNEL
371 #endif
372 
373 /**
374  *	vmalloc_exec  -  allocate virtually contiguous, executable memory
375  *	@size:		allocation size
376  *
377  *	Kernel-internal function to allocate enough pages to cover @size
378  *	the page level allocator and map them into contiguous and
379  *	executable kernel virtual space.
380  *
381  *	For tight control over page level allocator and protection flags
382  *	use __vmalloc() instead.
383  */
384 
385 void *vmalloc_exec(unsigned long size)
386 {
387 	return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL_EXEC);
388 }
389 
390 /**
391  * vmalloc_32  -  allocate virtually contiguous memory (32bit addressable)
392  *	@size:		allocation size
393  *
394  *	Allocate enough 32bit PA addressable pages to cover @size from the
395  *	page level allocator and map them into continguos kernel virtual space.
396  */
397 void *vmalloc_32(unsigned long size)
398 {
399 	return __vmalloc(size, GFP_KERNEL, PAGE_KERNEL);
400 }
401 EXPORT_SYMBOL(vmalloc_32);
402 
403 /**
404  * vmalloc_32_user - allocate zeroed virtually contiguous 32bit memory
405  *	@size:		allocation size
406  *
407  * The resulting memory area is 32bit addressable and zeroed so it can be
408  * mapped to userspace without leaking data.
409  *
410  * VM_USERMAP is set on the corresponding VMA so that subsequent calls to
411  * remap_vmalloc_range() are permissible.
412  */
413 void *vmalloc_32_user(unsigned long size)
414 {
415 	/*
416 	 * We'll have to sort out the ZONE_DMA bits for 64-bit,
417 	 * but for now this can simply use vmalloc_user() directly.
418 	 */
419 	return vmalloc_user(size);
420 }
421 EXPORT_SYMBOL(vmalloc_32_user);
422 
423 void *vmap(struct page **pages, unsigned int count, unsigned long flags, pgprot_t prot)
424 {
425 	BUG();
426 	return NULL;
427 }
428 EXPORT_SYMBOL(vmap);
429 
430 void vunmap(const void *addr)
431 {
432 	BUG();
433 }
434 EXPORT_SYMBOL(vunmap);
435 
436 void *vm_map_ram(struct page **pages, unsigned int count, int node, pgprot_t prot)
437 {
438 	BUG();
439 	return NULL;
440 }
441 EXPORT_SYMBOL(vm_map_ram);
442 
443 void vm_unmap_ram(const void *mem, unsigned int count)
444 {
445 	BUG();
446 }
447 EXPORT_SYMBOL(vm_unmap_ram);
448 
449 void vm_unmap_aliases(void)
450 {
451 }
452 EXPORT_SYMBOL_GPL(vm_unmap_aliases);
453 
454 /*
455  * Implement a stub for vmalloc_sync_all() if the architecture chose not to
456  * have one.
457  */
458 void  __attribute__((weak)) vmalloc_sync_all(void)
459 {
460 }
461 
462 /**
463  *	alloc_vm_area - allocate a range of kernel address space
464  *	@size:		size of the area
465  *
466  *	Returns:	NULL on failure, vm_struct on success
467  *
468  *	This function reserves a range of kernel address space, and
469  *	allocates pagetables to map that range.  No actual mappings
470  *	are created.  If the kernel address space is not shared
471  *	between processes, it syncs the pagetable across all
472  *	processes.
473  */
474 struct vm_struct *alloc_vm_area(size_t size, pte_t **ptes)
475 {
476 	BUG();
477 	return NULL;
478 }
479 EXPORT_SYMBOL_GPL(alloc_vm_area);
480 
481 void free_vm_area(struct vm_struct *area)
482 {
483 	BUG();
484 }
485 EXPORT_SYMBOL_GPL(free_vm_area);
486 
487 int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
488 		   struct page *page)
489 {
490 	return -EINVAL;
491 }
492 EXPORT_SYMBOL(vm_insert_page);
493 
494 /*
495  *  sys_brk() for the most part doesn't need the global kernel
496  *  lock, except when an application is doing something nasty
497  *  like trying to un-brk an area that has already been mapped
498  *  to a regular file.  in this case, the unmapping will need
499  *  to invoke file system routines that need the global lock.
500  */
501 SYSCALL_DEFINE1(brk, unsigned long, brk)
502 {
503 	struct mm_struct *mm = current->mm;
504 
505 	if (brk < mm->start_brk || brk > mm->context.end_brk)
506 		return mm->brk;
507 
508 	if (mm->brk == brk)
509 		return mm->brk;
510 
511 	/*
512 	 * Always allow shrinking brk
513 	 */
514 	if (brk <= mm->brk) {
515 		mm->brk = brk;
516 		return brk;
517 	}
518 
519 	/*
520 	 * Ok, looks good - let it rip.
521 	 */
522 	flush_icache_range(mm->brk, brk);
523 	return mm->brk = brk;
524 }
525 
526 /*
527  * initialise the VMA and region record slabs
528  */
529 void __init mmap_init(void)
530 {
531 	int ret;
532 
533 	ret = percpu_counter_init(&vm_committed_as, 0);
534 	VM_BUG_ON(ret);
535 	vm_region_jar = KMEM_CACHE(vm_region, SLAB_PANIC);
536 }
537 
538 /*
539  * validate the region tree
540  * - the caller must hold the region lock
541  */
542 #ifdef CONFIG_DEBUG_NOMMU_REGIONS
543 static noinline void validate_nommu_regions(void)
544 {
545 	struct vm_region *region, *last;
546 	struct rb_node *p, *lastp;
547 
548 	lastp = rb_first(&nommu_region_tree);
549 	if (!lastp)
550 		return;
551 
552 	last = rb_entry(lastp, struct vm_region, vm_rb);
553 	BUG_ON(unlikely(last->vm_end <= last->vm_start));
554 	BUG_ON(unlikely(last->vm_top < last->vm_end));
555 
556 	while ((p = rb_next(lastp))) {
557 		region = rb_entry(p, struct vm_region, vm_rb);
558 		last = rb_entry(lastp, struct vm_region, vm_rb);
559 
560 		BUG_ON(unlikely(region->vm_end <= region->vm_start));
561 		BUG_ON(unlikely(region->vm_top < region->vm_end));
562 		BUG_ON(unlikely(region->vm_start < last->vm_top));
563 
564 		lastp = p;
565 	}
566 }
567 #else
568 static void validate_nommu_regions(void)
569 {
570 }
571 #endif
572 
573 /*
574  * add a region into the global tree
575  */
576 static void add_nommu_region(struct vm_region *region)
577 {
578 	struct vm_region *pregion;
579 	struct rb_node **p, *parent;
580 
581 	validate_nommu_regions();
582 
583 	parent = NULL;
584 	p = &nommu_region_tree.rb_node;
585 	while (*p) {
586 		parent = *p;
587 		pregion = rb_entry(parent, struct vm_region, vm_rb);
588 		if (region->vm_start < pregion->vm_start)
589 			p = &(*p)->rb_left;
590 		else if (region->vm_start > pregion->vm_start)
591 			p = &(*p)->rb_right;
592 		else if (pregion == region)
593 			return;
594 		else
595 			BUG();
596 	}
597 
598 	rb_link_node(&region->vm_rb, parent, p);
599 	rb_insert_color(&region->vm_rb, &nommu_region_tree);
600 
601 	validate_nommu_regions();
602 }
603 
604 /*
605  * delete a region from the global tree
606  */
607 static void delete_nommu_region(struct vm_region *region)
608 {
609 	BUG_ON(!nommu_region_tree.rb_node);
610 
611 	validate_nommu_regions();
612 	rb_erase(&region->vm_rb, &nommu_region_tree);
613 	validate_nommu_regions();
614 }
615 
616 /*
617  * free a contiguous series of pages
618  */
619 static void free_page_series(unsigned long from, unsigned long to)
620 {
621 	for (; from < to; from += PAGE_SIZE) {
622 		struct page *page = virt_to_page(from);
623 
624 		kdebug("- free %lx", from);
625 		atomic_long_dec(&mmap_pages_allocated);
626 		if (page_count(page) != 1)
627 			kdebug("free page %p: refcount not one: %d",
628 			       page, page_count(page));
629 		put_page(page);
630 	}
631 }
632 
633 /*
634  * release a reference to a region
635  * - the caller must hold the region semaphore for writing, which this releases
636  * - the region may not have been added to the tree yet, in which case vm_top
637  *   will equal vm_start
638  */
639 static void __put_nommu_region(struct vm_region *region)
640 	__releases(nommu_region_sem)
641 {
642 	kenter("%p{%d}", region, region->vm_usage);
643 
644 	BUG_ON(!nommu_region_tree.rb_node);
645 
646 	if (--region->vm_usage == 0) {
647 		if (region->vm_top > region->vm_start)
648 			delete_nommu_region(region);
649 		up_write(&nommu_region_sem);
650 
651 		if (region->vm_file)
652 			fput(region->vm_file);
653 
654 		/* IO memory and memory shared directly out of the pagecache
655 		 * from ramfs/tmpfs mustn't be released here */
656 		if (region->vm_flags & VM_MAPPED_COPY) {
657 			kdebug("free series");
658 			free_page_series(region->vm_start, region->vm_top);
659 		}
660 		kmem_cache_free(vm_region_jar, region);
661 	} else {
662 		up_write(&nommu_region_sem);
663 	}
664 }
665 
666 /*
667  * release a reference to a region
668  */
669 static void put_nommu_region(struct vm_region *region)
670 {
671 	down_write(&nommu_region_sem);
672 	__put_nommu_region(region);
673 }
674 
675 /*
676  * update protection on a vma
677  */
678 static void protect_vma(struct vm_area_struct *vma, unsigned long flags)
679 {
680 #ifdef CONFIG_MPU
681 	struct mm_struct *mm = vma->vm_mm;
682 	long start = vma->vm_start & PAGE_MASK;
683 	while (start < vma->vm_end) {
684 		protect_page(mm, start, flags);
685 		start += PAGE_SIZE;
686 	}
687 	update_protections(mm);
688 #endif
689 }
690 
691 /*
692  * add a VMA into a process's mm_struct in the appropriate place in the list
693  * and tree and add to the address space's page tree also if not an anonymous
694  * page
695  * - should be called with mm->mmap_sem held writelocked
696  */
697 static void add_vma_to_mm(struct mm_struct *mm, struct vm_area_struct *vma)
698 {
699 	struct vm_area_struct *pvma, *prev;
700 	struct address_space *mapping;
701 	struct rb_node **p, *parent, *rb_prev;
702 
703 	kenter(",%p", vma);
704 
705 	BUG_ON(!vma->vm_region);
706 
707 	mm->map_count++;
708 	vma->vm_mm = mm;
709 
710 	protect_vma(vma, vma->vm_flags);
711 
712 	/* add the VMA to the mapping */
713 	if (vma->vm_file) {
714 		mapping = vma->vm_file->f_mapping;
715 
716 		mutex_lock(&mapping->i_mmap_mutex);
717 		flush_dcache_mmap_lock(mapping);
718 		vma_interval_tree_insert(vma, &mapping->i_mmap);
719 		flush_dcache_mmap_unlock(mapping);
720 		mutex_unlock(&mapping->i_mmap_mutex);
721 	}
722 
723 	/* add the VMA to the tree */
724 	parent = rb_prev = NULL;
725 	p = &mm->mm_rb.rb_node;
726 	while (*p) {
727 		parent = *p;
728 		pvma = rb_entry(parent, struct vm_area_struct, vm_rb);
729 
730 		/* sort by: start addr, end addr, VMA struct addr in that order
731 		 * (the latter is necessary as we may get identical VMAs) */
732 		if (vma->vm_start < pvma->vm_start)
733 			p = &(*p)->rb_left;
734 		else if (vma->vm_start > pvma->vm_start) {
735 			rb_prev = parent;
736 			p = &(*p)->rb_right;
737 		} else if (vma->vm_end < pvma->vm_end)
738 			p = &(*p)->rb_left;
739 		else if (vma->vm_end > pvma->vm_end) {
740 			rb_prev = parent;
741 			p = &(*p)->rb_right;
742 		} else if (vma < pvma)
743 			p = &(*p)->rb_left;
744 		else if (vma > pvma) {
745 			rb_prev = parent;
746 			p = &(*p)->rb_right;
747 		} else
748 			BUG();
749 	}
750 
751 	rb_link_node(&vma->vm_rb, parent, p);
752 	rb_insert_color(&vma->vm_rb, &mm->mm_rb);
753 
754 	/* add VMA to the VMA list also */
755 	prev = NULL;
756 	if (rb_prev)
757 		prev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
758 
759 	__vma_link_list(mm, vma, prev, parent);
760 }
761 
762 /*
763  * delete a VMA from its owning mm_struct and address space
764  */
765 static void delete_vma_from_mm(struct vm_area_struct *vma)
766 {
767 	struct address_space *mapping;
768 	struct mm_struct *mm = vma->vm_mm;
769 
770 	kenter("%p", vma);
771 
772 	protect_vma(vma, 0);
773 
774 	mm->map_count--;
775 	if (mm->mmap_cache == vma)
776 		mm->mmap_cache = NULL;
777 
778 	/* remove the VMA from the mapping */
779 	if (vma->vm_file) {
780 		mapping = vma->vm_file->f_mapping;
781 
782 		mutex_lock(&mapping->i_mmap_mutex);
783 		flush_dcache_mmap_lock(mapping);
784 		vma_interval_tree_remove(vma, &mapping->i_mmap);
785 		flush_dcache_mmap_unlock(mapping);
786 		mutex_unlock(&mapping->i_mmap_mutex);
787 	}
788 
789 	/* remove from the MM's tree and list */
790 	rb_erase(&vma->vm_rb, &mm->mm_rb);
791 
792 	if (vma->vm_prev)
793 		vma->vm_prev->vm_next = vma->vm_next;
794 	else
795 		mm->mmap = vma->vm_next;
796 
797 	if (vma->vm_next)
798 		vma->vm_next->vm_prev = vma->vm_prev;
799 }
800 
801 /*
802  * destroy a VMA record
803  */
804 static void delete_vma(struct mm_struct *mm, struct vm_area_struct *vma)
805 {
806 	kenter("%p", vma);
807 	if (vma->vm_ops && vma->vm_ops->close)
808 		vma->vm_ops->close(vma);
809 	if (vma->vm_file)
810 		fput(vma->vm_file);
811 	put_nommu_region(vma->vm_region);
812 	kmem_cache_free(vm_area_cachep, vma);
813 }
814 
815 /*
816  * look up the first VMA in which addr resides, NULL if none
817  * - should be called with mm->mmap_sem at least held readlocked
818  */
819 struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
820 {
821 	struct vm_area_struct *vma;
822 
823 	/* check the cache first */
824 	vma = mm->mmap_cache;
825 	if (vma && vma->vm_start <= addr && vma->vm_end > addr)
826 		return vma;
827 
828 	/* trawl the list (there may be multiple mappings in which addr
829 	 * resides) */
830 	for (vma = mm->mmap; vma; vma = vma->vm_next) {
831 		if (vma->vm_start > addr)
832 			return NULL;
833 		if (vma->vm_end > addr) {
834 			mm->mmap_cache = vma;
835 			return vma;
836 		}
837 	}
838 
839 	return NULL;
840 }
841 EXPORT_SYMBOL(find_vma);
842 
843 /*
844  * find a VMA
845  * - we don't extend stack VMAs under NOMMU conditions
846  */
847 struct vm_area_struct *find_extend_vma(struct mm_struct *mm, unsigned long addr)
848 {
849 	return find_vma(mm, addr);
850 }
851 
852 /*
853  * expand a stack to a given address
854  * - not supported under NOMMU conditions
855  */
856 int expand_stack(struct vm_area_struct *vma, unsigned long address)
857 {
858 	return -ENOMEM;
859 }
860 
861 /*
862  * look up the first VMA exactly that exactly matches addr
863  * - should be called with mm->mmap_sem at least held readlocked
864  */
865 static struct vm_area_struct *find_vma_exact(struct mm_struct *mm,
866 					     unsigned long addr,
867 					     unsigned long len)
868 {
869 	struct vm_area_struct *vma;
870 	unsigned long end = addr + len;
871 
872 	/* check the cache first */
873 	vma = mm->mmap_cache;
874 	if (vma && vma->vm_start == addr && vma->vm_end == end)
875 		return vma;
876 
877 	/* trawl the list (there may be multiple mappings in which addr
878 	 * resides) */
879 	for (vma = mm->mmap; vma; vma = vma->vm_next) {
880 		if (vma->vm_start < addr)
881 			continue;
882 		if (vma->vm_start > addr)
883 			return NULL;
884 		if (vma->vm_end == end) {
885 			mm->mmap_cache = vma;
886 			return vma;
887 		}
888 	}
889 
890 	return NULL;
891 }
892 
893 /*
894  * determine whether a mapping should be permitted and, if so, what sort of
895  * mapping we're capable of supporting
896  */
897 static int validate_mmap_request(struct file *file,
898 				 unsigned long addr,
899 				 unsigned long len,
900 				 unsigned long prot,
901 				 unsigned long flags,
902 				 unsigned long pgoff,
903 				 unsigned long *_capabilities)
904 {
905 	unsigned long capabilities, rlen;
906 	int ret;
907 
908 	/* do the simple checks first */
909 	if (flags & MAP_FIXED) {
910 		printk(KERN_DEBUG
911 		       "%d: Can't do fixed-address/overlay mmap of RAM\n",
912 		       current->pid);
913 		return -EINVAL;
914 	}
915 
916 	if ((flags & MAP_TYPE) != MAP_PRIVATE &&
917 	    (flags & MAP_TYPE) != MAP_SHARED)
918 		return -EINVAL;
919 
920 	if (!len)
921 		return -EINVAL;
922 
923 	/* Careful about overflows.. */
924 	rlen = PAGE_ALIGN(len);
925 	if (!rlen || rlen > TASK_SIZE)
926 		return -ENOMEM;
927 
928 	/* offset overflow? */
929 	if ((pgoff + (rlen >> PAGE_SHIFT)) < pgoff)
930 		return -EOVERFLOW;
931 
932 	if (file) {
933 		/* validate file mapping requests */
934 		struct address_space *mapping;
935 
936 		/* files must support mmap */
937 		if (!file->f_op || !file->f_op->mmap)
938 			return -ENODEV;
939 
940 		/* work out if what we've got could possibly be shared
941 		 * - we support chardevs that provide their own "memory"
942 		 * - we support files/blockdevs that are memory backed
943 		 */
944 		mapping = file->f_mapping;
945 		if (!mapping)
946 			mapping = file_inode(file)->i_mapping;
947 
948 		capabilities = 0;
949 		if (mapping && mapping->backing_dev_info)
950 			capabilities = mapping->backing_dev_info->capabilities;
951 
952 		if (!capabilities) {
953 			/* no explicit capabilities set, so assume some
954 			 * defaults */
955 			switch (file_inode(file)->i_mode & S_IFMT) {
956 			case S_IFREG:
957 			case S_IFBLK:
958 				capabilities = BDI_CAP_MAP_COPY;
959 				break;
960 
961 			case S_IFCHR:
962 				capabilities =
963 					BDI_CAP_MAP_DIRECT |
964 					BDI_CAP_READ_MAP |
965 					BDI_CAP_WRITE_MAP;
966 				break;
967 
968 			default:
969 				return -EINVAL;
970 			}
971 		}
972 
973 		/* eliminate any capabilities that we can't support on this
974 		 * device */
975 		if (!file->f_op->get_unmapped_area)
976 			capabilities &= ~BDI_CAP_MAP_DIRECT;
977 		if (!file->f_op->read)
978 			capabilities &= ~BDI_CAP_MAP_COPY;
979 
980 		/* The file shall have been opened with read permission. */
981 		if (!(file->f_mode & FMODE_READ))
982 			return -EACCES;
983 
984 		if (flags & MAP_SHARED) {
985 			/* do checks for writing, appending and locking */
986 			if ((prot & PROT_WRITE) &&
987 			    !(file->f_mode & FMODE_WRITE))
988 				return -EACCES;
989 
990 			if (IS_APPEND(file_inode(file)) &&
991 			    (file->f_mode & FMODE_WRITE))
992 				return -EACCES;
993 
994 			if (locks_verify_locked(file_inode(file)))
995 				return -EAGAIN;
996 
997 			if (!(capabilities & BDI_CAP_MAP_DIRECT))
998 				return -ENODEV;
999 
1000 			/* we mustn't privatise shared mappings */
1001 			capabilities &= ~BDI_CAP_MAP_COPY;
1002 		}
1003 		else {
1004 			/* we're going to read the file into private memory we
1005 			 * allocate */
1006 			if (!(capabilities & BDI_CAP_MAP_COPY))
1007 				return -ENODEV;
1008 
1009 			/* we don't permit a private writable mapping to be
1010 			 * shared with the backing device */
1011 			if (prot & PROT_WRITE)
1012 				capabilities &= ~BDI_CAP_MAP_DIRECT;
1013 		}
1014 
1015 		if (capabilities & BDI_CAP_MAP_DIRECT) {
1016 			if (((prot & PROT_READ)  && !(capabilities & BDI_CAP_READ_MAP))  ||
1017 			    ((prot & PROT_WRITE) && !(capabilities & BDI_CAP_WRITE_MAP)) ||
1018 			    ((prot & PROT_EXEC)  && !(capabilities & BDI_CAP_EXEC_MAP))
1019 			    ) {
1020 				capabilities &= ~BDI_CAP_MAP_DIRECT;
1021 				if (flags & MAP_SHARED) {
1022 					printk(KERN_WARNING
1023 					       "MAP_SHARED not completely supported on !MMU\n");
1024 					return -EINVAL;
1025 				}
1026 			}
1027 		}
1028 
1029 		/* handle executable mappings and implied executable
1030 		 * mappings */
1031 		if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) {
1032 			if (prot & PROT_EXEC)
1033 				return -EPERM;
1034 		}
1035 		else if ((prot & PROT_READ) && !(prot & PROT_EXEC)) {
1036 			/* handle implication of PROT_EXEC by PROT_READ */
1037 			if (current->personality & READ_IMPLIES_EXEC) {
1038 				if (capabilities & BDI_CAP_EXEC_MAP)
1039 					prot |= PROT_EXEC;
1040 			}
1041 		}
1042 		else if ((prot & PROT_READ) &&
1043 			 (prot & PROT_EXEC) &&
1044 			 !(capabilities & BDI_CAP_EXEC_MAP)
1045 			 ) {
1046 			/* backing file is not executable, try to copy */
1047 			capabilities &= ~BDI_CAP_MAP_DIRECT;
1048 		}
1049 	}
1050 	else {
1051 		/* anonymous mappings are always memory backed and can be
1052 		 * privately mapped
1053 		 */
1054 		capabilities = BDI_CAP_MAP_COPY;
1055 
1056 		/* handle PROT_EXEC implication by PROT_READ */
1057 		if ((prot & PROT_READ) &&
1058 		    (current->personality & READ_IMPLIES_EXEC))
1059 			prot |= PROT_EXEC;
1060 	}
1061 
1062 	/* allow the security API to have its say */
1063 	ret = security_mmap_addr(addr);
1064 	if (ret < 0)
1065 		return ret;
1066 
1067 	/* looks okay */
1068 	*_capabilities = capabilities;
1069 	return 0;
1070 }
1071 
1072 /*
1073  * we've determined that we can make the mapping, now translate what we
1074  * now know into VMA flags
1075  */
1076 static unsigned long determine_vm_flags(struct file *file,
1077 					unsigned long prot,
1078 					unsigned long flags,
1079 					unsigned long capabilities)
1080 {
1081 	unsigned long vm_flags;
1082 
1083 	vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags);
1084 	/* vm_flags |= mm->def_flags; */
1085 
1086 	if (!(capabilities & BDI_CAP_MAP_DIRECT)) {
1087 		/* attempt to share read-only copies of mapped file chunks */
1088 		vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
1089 		if (file && !(prot & PROT_WRITE))
1090 			vm_flags |= VM_MAYSHARE;
1091 	} else {
1092 		/* overlay a shareable mapping on the backing device or inode
1093 		 * if possible - used for chardevs, ramfs/tmpfs/shmfs and
1094 		 * romfs/cramfs */
1095 		vm_flags |= VM_MAYSHARE | (capabilities & BDI_CAP_VMFLAGS);
1096 		if (flags & MAP_SHARED)
1097 			vm_flags |= VM_SHARED;
1098 	}
1099 
1100 	/* refuse to let anyone share private mappings with this process if
1101 	 * it's being traced - otherwise breakpoints set in it may interfere
1102 	 * with another untraced process
1103 	 */
1104 	if ((flags & MAP_PRIVATE) && current->ptrace)
1105 		vm_flags &= ~VM_MAYSHARE;
1106 
1107 	return vm_flags;
1108 }
1109 
1110 /*
1111  * set up a shared mapping on a file (the driver or filesystem provides and
1112  * pins the storage)
1113  */
1114 static int do_mmap_shared_file(struct vm_area_struct *vma)
1115 {
1116 	int ret;
1117 
1118 	ret = vma->vm_file->f_op->mmap(vma->vm_file, vma);
1119 	if (ret == 0) {
1120 		vma->vm_region->vm_top = vma->vm_region->vm_end;
1121 		return 0;
1122 	}
1123 	if (ret != -ENOSYS)
1124 		return ret;
1125 
1126 	/* getting -ENOSYS indicates that direct mmap isn't possible (as
1127 	 * opposed to tried but failed) so we can only give a suitable error as
1128 	 * it's not possible to make a private copy if MAP_SHARED was given */
1129 	return -ENODEV;
1130 }
1131 
1132 /*
1133  * set up a private mapping or an anonymous shared mapping
1134  */
1135 static int do_mmap_private(struct vm_area_struct *vma,
1136 			   struct vm_region *region,
1137 			   unsigned long len,
1138 			   unsigned long capabilities)
1139 {
1140 	struct page *pages;
1141 	unsigned long total, point, n;
1142 	void *base;
1143 	int ret, order;
1144 
1145 	/* invoke the file's mapping function so that it can keep track of
1146 	 * shared mappings on devices or memory
1147 	 * - VM_MAYSHARE will be set if it may attempt to share
1148 	 */
1149 	if (capabilities & BDI_CAP_MAP_DIRECT) {
1150 		ret = vma->vm_file->f_op->mmap(vma->vm_file, vma);
1151 		if (ret == 0) {
1152 			/* shouldn't return success if we're not sharing */
1153 			BUG_ON(!(vma->vm_flags & VM_MAYSHARE));
1154 			vma->vm_region->vm_top = vma->vm_region->vm_end;
1155 			return 0;
1156 		}
1157 		if (ret != -ENOSYS)
1158 			return ret;
1159 
1160 		/* getting an ENOSYS error indicates that direct mmap isn't
1161 		 * possible (as opposed to tried but failed) so we'll try to
1162 		 * make a private copy of the data and map that instead */
1163 	}
1164 
1165 
1166 	/* allocate some memory to hold the mapping
1167 	 * - note that this may not return a page-aligned address if the object
1168 	 *   we're allocating is smaller than a page
1169 	 */
1170 	order = get_order(len);
1171 	kdebug("alloc order %d for %lx", order, len);
1172 
1173 	pages = alloc_pages(GFP_KERNEL, order);
1174 	if (!pages)
1175 		goto enomem;
1176 
1177 	total = 1 << order;
1178 	atomic_long_add(total, &mmap_pages_allocated);
1179 
1180 	point = len >> PAGE_SHIFT;
1181 
1182 	/* we allocated a power-of-2 sized page set, so we may want to trim off
1183 	 * the excess */
1184 	if (sysctl_nr_trim_pages && total - point >= sysctl_nr_trim_pages) {
1185 		while (total > point) {
1186 			order = ilog2(total - point);
1187 			n = 1 << order;
1188 			kdebug("shave %lu/%lu @%lu", n, total - point, total);
1189 			atomic_long_sub(n, &mmap_pages_allocated);
1190 			total -= n;
1191 			set_page_refcounted(pages + total);
1192 			__free_pages(pages + total, order);
1193 		}
1194 	}
1195 
1196 	for (point = 1; point < total; point++)
1197 		set_page_refcounted(&pages[point]);
1198 
1199 	base = page_address(pages);
1200 	region->vm_flags = vma->vm_flags |= VM_MAPPED_COPY;
1201 	region->vm_start = (unsigned long) base;
1202 	region->vm_end   = region->vm_start + len;
1203 	region->vm_top   = region->vm_start + (total << PAGE_SHIFT);
1204 
1205 	vma->vm_start = region->vm_start;
1206 	vma->vm_end   = region->vm_start + len;
1207 
1208 	if (vma->vm_file) {
1209 		/* read the contents of a file into the copy */
1210 		mm_segment_t old_fs;
1211 		loff_t fpos;
1212 
1213 		fpos = vma->vm_pgoff;
1214 		fpos <<= PAGE_SHIFT;
1215 
1216 		old_fs = get_fs();
1217 		set_fs(KERNEL_DS);
1218 		ret = vma->vm_file->f_op->read(vma->vm_file, base, len, &fpos);
1219 		set_fs(old_fs);
1220 
1221 		if (ret < 0)
1222 			goto error_free;
1223 
1224 		/* clear the last little bit */
1225 		if (ret < len)
1226 			memset(base + ret, 0, len - ret);
1227 
1228 	}
1229 
1230 	return 0;
1231 
1232 error_free:
1233 	free_page_series(region->vm_start, region->vm_top);
1234 	region->vm_start = vma->vm_start = 0;
1235 	region->vm_end   = vma->vm_end = 0;
1236 	region->vm_top   = 0;
1237 	return ret;
1238 
1239 enomem:
1240 	printk("Allocation of length %lu from process %d (%s) failed\n",
1241 	       len, current->pid, current->comm);
1242 	show_free_areas(0);
1243 	return -ENOMEM;
1244 }
1245 
1246 /*
1247  * handle mapping creation for uClinux
1248  */
1249 unsigned long do_mmap_pgoff(struct file *file,
1250 			    unsigned long addr,
1251 			    unsigned long len,
1252 			    unsigned long prot,
1253 			    unsigned long flags,
1254 			    unsigned long pgoff,
1255 			    unsigned long *populate)
1256 {
1257 	struct vm_area_struct *vma;
1258 	struct vm_region *region;
1259 	struct rb_node *rb;
1260 	unsigned long capabilities, vm_flags, result;
1261 	int ret;
1262 
1263 	kenter(",%lx,%lx,%lx,%lx,%lx", addr, len, prot, flags, pgoff);
1264 
1265 	*populate = 0;
1266 
1267 	/* decide whether we should attempt the mapping, and if so what sort of
1268 	 * mapping */
1269 	ret = validate_mmap_request(file, addr, len, prot, flags, pgoff,
1270 				    &capabilities);
1271 	if (ret < 0) {
1272 		kleave(" = %d [val]", ret);
1273 		return ret;
1274 	}
1275 
1276 	/* we ignore the address hint */
1277 	addr = 0;
1278 	len = PAGE_ALIGN(len);
1279 
1280 	/* we've determined that we can make the mapping, now translate what we
1281 	 * now know into VMA flags */
1282 	vm_flags = determine_vm_flags(file, prot, flags, capabilities);
1283 
1284 	/* we're going to need to record the mapping */
1285 	region = kmem_cache_zalloc(vm_region_jar, GFP_KERNEL);
1286 	if (!region)
1287 		goto error_getting_region;
1288 
1289 	vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
1290 	if (!vma)
1291 		goto error_getting_vma;
1292 
1293 	region->vm_usage = 1;
1294 	region->vm_flags = vm_flags;
1295 	region->vm_pgoff = pgoff;
1296 
1297 	INIT_LIST_HEAD(&vma->anon_vma_chain);
1298 	vma->vm_flags = vm_flags;
1299 	vma->vm_pgoff = pgoff;
1300 
1301 	if (file) {
1302 		region->vm_file = get_file(file);
1303 		vma->vm_file = get_file(file);
1304 	}
1305 
1306 	down_write(&nommu_region_sem);
1307 
1308 	/* if we want to share, we need to check for regions created by other
1309 	 * mmap() calls that overlap with our proposed mapping
1310 	 * - we can only share with a superset match on most regular files
1311 	 * - shared mappings on character devices and memory backed files are
1312 	 *   permitted to overlap inexactly as far as we are concerned for in
1313 	 *   these cases, sharing is handled in the driver or filesystem rather
1314 	 *   than here
1315 	 */
1316 	if (vm_flags & VM_MAYSHARE) {
1317 		struct vm_region *pregion;
1318 		unsigned long pglen, rpglen, pgend, rpgend, start;
1319 
1320 		pglen = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1321 		pgend = pgoff + pglen;
1322 
1323 		for (rb = rb_first(&nommu_region_tree); rb; rb = rb_next(rb)) {
1324 			pregion = rb_entry(rb, struct vm_region, vm_rb);
1325 
1326 			if (!(pregion->vm_flags & VM_MAYSHARE))
1327 				continue;
1328 
1329 			/* search for overlapping mappings on the same file */
1330 			if (file_inode(pregion->vm_file) !=
1331 			    file_inode(file))
1332 				continue;
1333 
1334 			if (pregion->vm_pgoff >= pgend)
1335 				continue;
1336 
1337 			rpglen = pregion->vm_end - pregion->vm_start;
1338 			rpglen = (rpglen + PAGE_SIZE - 1) >> PAGE_SHIFT;
1339 			rpgend = pregion->vm_pgoff + rpglen;
1340 			if (pgoff >= rpgend)
1341 				continue;
1342 
1343 			/* handle inexactly overlapping matches between
1344 			 * mappings */
1345 			if ((pregion->vm_pgoff != pgoff || rpglen != pglen) &&
1346 			    !(pgoff >= pregion->vm_pgoff && pgend <= rpgend)) {
1347 				/* new mapping is not a subset of the region */
1348 				if (!(capabilities & BDI_CAP_MAP_DIRECT))
1349 					goto sharing_violation;
1350 				continue;
1351 			}
1352 
1353 			/* we've found a region we can share */
1354 			pregion->vm_usage++;
1355 			vma->vm_region = pregion;
1356 			start = pregion->vm_start;
1357 			start += (pgoff - pregion->vm_pgoff) << PAGE_SHIFT;
1358 			vma->vm_start = start;
1359 			vma->vm_end = start + len;
1360 
1361 			if (pregion->vm_flags & VM_MAPPED_COPY) {
1362 				kdebug("share copy");
1363 				vma->vm_flags |= VM_MAPPED_COPY;
1364 			} else {
1365 				kdebug("share mmap");
1366 				ret = do_mmap_shared_file(vma);
1367 				if (ret < 0) {
1368 					vma->vm_region = NULL;
1369 					vma->vm_start = 0;
1370 					vma->vm_end = 0;
1371 					pregion->vm_usage--;
1372 					pregion = NULL;
1373 					goto error_just_free;
1374 				}
1375 			}
1376 			fput(region->vm_file);
1377 			kmem_cache_free(vm_region_jar, region);
1378 			region = pregion;
1379 			result = start;
1380 			goto share;
1381 		}
1382 
1383 		/* obtain the address at which to make a shared mapping
1384 		 * - this is the hook for quasi-memory character devices to
1385 		 *   tell us the location of a shared mapping
1386 		 */
1387 		if (capabilities & BDI_CAP_MAP_DIRECT) {
1388 			addr = file->f_op->get_unmapped_area(file, addr, len,
1389 							     pgoff, flags);
1390 			if (IS_ERR_VALUE(addr)) {
1391 				ret = addr;
1392 				if (ret != -ENOSYS)
1393 					goto error_just_free;
1394 
1395 				/* the driver refused to tell us where to site
1396 				 * the mapping so we'll have to attempt to copy
1397 				 * it */
1398 				ret = -ENODEV;
1399 				if (!(capabilities & BDI_CAP_MAP_COPY))
1400 					goto error_just_free;
1401 
1402 				capabilities &= ~BDI_CAP_MAP_DIRECT;
1403 			} else {
1404 				vma->vm_start = region->vm_start = addr;
1405 				vma->vm_end = region->vm_end = addr + len;
1406 			}
1407 		}
1408 	}
1409 
1410 	vma->vm_region = region;
1411 
1412 	/* set up the mapping
1413 	 * - the region is filled in if BDI_CAP_MAP_DIRECT is still set
1414 	 */
1415 	if (file && vma->vm_flags & VM_SHARED)
1416 		ret = do_mmap_shared_file(vma);
1417 	else
1418 		ret = do_mmap_private(vma, region, len, capabilities);
1419 	if (ret < 0)
1420 		goto error_just_free;
1421 	add_nommu_region(region);
1422 
1423 	/* clear anonymous mappings that don't ask for uninitialized data */
1424 	if (!vma->vm_file && !(flags & MAP_UNINITIALIZED))
1425 		memset((void *)region->vm_start, 0,
1426 		       region->vm_end - region->vm_start);
1427 
1428 	/* okay... we have a mapping; now we have to register it */
1429 	result = vma->vm_start;
1430 
1431 	current->mm->total_vm += len >> PAGE_SHIFT;
1432 
1433 share:
1434 	add_vma_to_mm(current->mm, vma);
1435 
1436 	/* we flush the region from the icache only when the first executable
1437 	 * mapping of it is made  */
1438 	if (vma->vm_flags & VM_EXEC && !region->vm_icache_flushed) {
1439 		flush_icache_range(region->vm_start, region->vm_end);
1440 		region->vm_icache_flushed = true;
1441 	}
1442 
1443 	up_write(&nommu_region_sem);
1444 
1445 	kleave(" = %lx", result);
1446 	return result;
1447 
1448 error_just_free:
1449 	up_write(&nommu_region_sem);
1450 error:
1451 	if (region->vm_file)
1452 		fput(region->vm_file);
1453 	kmem_cache_free(vm_region_jar, region);
1454 	if (vma->vm_file)
1455 		fput(vma->vm_file);
1456 	kmem_cache_free(vm_area_cachep, vma);
1457 	kleave(" = %d", ret);
1458 	return ret;
1459 
1460 sharing_violation:
1461 	up_write(&nommu_region_sem);
1462 	printk(KERN_WARNING "Attempt to share mismatched mappings\n");
1463 	ret = -EINVAL;
1464 	goto error;
1465 
1466 error_getting_vma:
1467 	kmem_cache_free(vm_region_jar, region);
1468 	printk(KERN_WARNING "Allocation of vma for %lu byte allocation"
1469 	       " from process %d failed\n",
1470 	       len, current->pid);
1471 	show_free_areas(0);
1472 	return -ENOMEM;
1473 
1474 error_getting_region:
1475 	printk(KERN_WARNING "Allocation of vm region for %lu byte allocation"
1476 	       " from process %d failed\n",
1477 	       len, current->pid);
1478 	show_free_areas(0);
1479 	return -ENOMEM;
1480 }
1481 
1482 SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
1483 		unsigned long, prot, unsigned long, flags,
1484 		unsigned long, fd, unsigned long, pgoff)
1485 {
1486 	struct file *file = NULL;
1487 	unsigned long retval = -EBADF;
1488 
1489 	audit_mmap_fd(fd, flags);
1490 	if (!(flags & MAP_ANONYMOUS)) {
1491 		file = fget(fd);
1492 		if (!file)
1493 			goto out;
1494 	}
1495 
1496 	flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
1497 
1498 	retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
1499 
1500 	if (file)
1501 		fput(file);
1502 out:
1503 	return retval;
1504 }
1505 
1506 #ifdef __ARCH_WANT_SYS_OLD_MMAP
1507 struct mmap_arg_struct {
1508 	unsigned long addr;
1509 	unsigned long len;
1510 	unsigned long prot;
1511 	unsigned long flags;
1512 	unsigned long fd;
1513 	unsigned long offset;
1514 };
1515 
1516 SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
1517 {
1518 	struct mmap_arg_struct a;
1519 
1520 	if (copy_from_user(&a, arg, sizeof(a)))
1521 		return -EFAULT;
1522 	if (a.offset & ~PAGE_MASK)
1523 		return -EINVAL;
1524 
1525 	return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
1526 			      a.offset >> PAGE_SHIFT);
1527 }
1528 #endif /* __ARCH_WANT_SYS_OLD_MMAP */
1529 
1530 /*
1531  * split a vma into two pieces at address 'addr', a new vma is allocated either
1532  * for the first part or the tail.
1533  */
1534 int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
1535 	      unsigned long addr, int new_below)
1536 {
1537 	struct vm_area_struct *new;
1538 	struct vm_region *region;
1539 	unsigned long npages;
1540 
1541 	kenter("");
1542 
1543 	/* we're only permitted to split anonymous regions (these should have
1544 	 * only a single usage on the region) */
1545 	if (vma->vm_file)
1546 		return -ENOMEM;
1547 
1548 	if (mm->map_count >= sysctl_max_map_count)
1549 		return -ENOMEM;
1550 
1551 	region = kmem_cache_alloc(vm_region_jar, GFP_KERNEL);
1552 	if (!region)
1553 		return -ENOMEM;
1554 
1555 	new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
1556 	if (!new) {
1557 		kmem_cache_free(vm_region_jar, region);
1558 		return -ENOMEM;
1559 	}
1560 
1561 	/* most fields are the same, copy all, and then fixup */
1562 	*new = *vma;
1563 	*region = *vma->vm_region;
1564 	new->vm_region = region;
1565 
1566 	npages = (addr - vma->vm_start) >> PAGE_SHIFT;
1567 
1568 	if (new_below) {
1569 		region->vm_top = region->vm_end = new->vm_end = addr;
1570 	} else {
1571 		region->vm_start = new->vm_start = addr;
1572 		region->vm_pgoff = new->vm_pgoff += npages;
1573 	}
1574 
1575 	if (new->vm_ops && new->vm_ops->open)
1576 		new->vm_ops->open(new);
1577 
1578 	delete_vma_from_mm(vma);
1579 	down_write(&nommu_region_sem);
1580 	delete_nommu_region(vma->vm_region);
1581 	if (new_below) {
1582 		vma->vm_region->vm_start = vma->vm_start = addr;
1583 		vma->vm_region->vm_pgoff = vma->vm_pgoff += npages;
1584 	} else {
1585 		vma->vm_region->vm_end = vma->vm_end = addr;
1586 		vma->vm_region->vm_top = addr;
1587 	}
1588 	add_nommu_region(vma->vm_region);
1589 	add_nommu_region(new->vm_region);
1590 	up_write(&nommu_region_sem);
1591 	add_vma_to_mm(mm, vma);
1592 	add_vma_to_mm(mm, new);
1593 	return 0;
1594 }
1595 
1596 /*
1597  * shrink a VMA by removing the specified chunk from either the beginning or
1598  * the end
1599  */
1600 static int shrink_vma(struct mm_struct *mm,
1601 		      struct vm_area_struct *vma,
1602 		      unsigned long from, unsigned long to)
1603 {
1604 	struct vm_region *region;
1605 
1606 	kenter("");
1607 
1608 	/* adjust the VMA's pointers, which may reposition it in the MM's tree
1609 	 * and list */
1610 	delete_vma_from_mm(vma);
1611 	if (from > vma->vm_start)
1612 		vma->vm_end = from;
1613 	else
1614 		vma->vm_start = to;
1615 	add_vma_to_mm(mm, vma);
1616 
1617 	/* cut the backing region down to size */
1618 	region = vma->vm_region;
1619 	BUG_ON(region->vm_usage != 1);
1620 
1621 	down_write(&nommu_region_sem);
1622 	delete_nommu_region(region);
1623 	if (from > region->vm_start) {
1624 		to = region->vm_top;
1625 		region->vm_top = region->vm_end = from;
1626 	} else {
1627 		region->vm_start = to;
1628 	}
1629 	add_nommu_region(region);
1630 	up_write(&nommu_region_sem);
1631 
1632 	free_page_series(from, to);
1633 	return 0;
1634 }
1635 
1636 /*
1637  * release a mapping
1638  * - under NOMMU conditions the chunk to be unmapped must be backed by a single
1639  *   VMA, though it need not cover the whole VMA
1640  */
1641 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
1642 {
1643 	struct vm_area_struct *vma;
1644 	unsigned long end;
1645 	int ret;
1646 
1647 	kenter(",%lx,%zx", start, len);
1648 
1649 	len = PAGE_ALIGN(len);
1650 	if (len == 0)
1651 		return -EINVAL;
1652 
1653 	end = start + len;
1654 
1655 	/* find the first potentially overlapping VMA */
1656 	vma = find_vma(mm, start);
1657 	if (!vma) {
1658 		static int limit = 0;
1659 		if (limit < 5) {
1660 			printk(KERN_WARNING
1661 			       "munmap of memory not mmapped by process %d"
1662 			       " (%s): 0x%lx-0x%lx\n",
1663 			       current->pid, current->comm,
1664 			       start, start + len - 1);
1665 			limit++;
1666 		}
1667 		return -EINVAL;
1668 	}
1669 
1670 	/* we're allowed to split an anonymous VMA but not a file-backed one */
1671 	if (vma->vm_file) {
1672 		do {
1673 			if (start > vma->vm_start) {
1674 				kleave(" = -EINVAL [miss]");
1675 				return -EINVAL;
1676 			}
1677 			if (end == vma->vm_end)
1678 				goto erase_whole_vma;
1679 			vma = vma->vm_next;
1680 		} while (vma);
1681 		kleave(" = -EINVAL [split file]");
1682 		return -EINVAL;
1683 	} else {
1684 		/* the chunk must be a subset of the VMA found */
1685 		if (start == vma->vm_start && end == vma->vm_end)
1686 			goto erase_whole_vma;
1687 		if (start < vma->vm_start || end > vma->vm_end) {
1688 			kleave(" = -EINVAL [superset]");
1689 			return -EINVAL;
1690 		}
1691 		if (start & ~PAGE_MASK) {
1692 			kleave(" = -EINVAL [unaligned start]");
1693 			return -EINVAL;
1694 		}
1695 		if (end != vma->vm_end && end & ~PAGE_MASK) {
1696 			kleave(" = -EINVAL [unaligned split]");
1697 			return -EINVAL;
1698 		}
1699 		if (start != vma->vm_start && end != vma->vm_end) {
1700 			ret = split_vma(mm, vma, start, 1);
1701 			if (ret < 0) {
1702 				kleave(" = %d [split]", ret);
1703 				return ret;
1704 			}
1705 		}
1706 		return shrink_vma(mm, vma, start, end);
1707 	}
1708 
1709 erase_whole_vma:
1710 	delete_vma_from_mm(vma);
1711 	delete_vma(mm, vma);
1712 	kleave(" = 0");
1713 	return 0;
1714 }
1715 EXPORT_SYMBOL(do_munmap);
1716 
1717 int vm_munmap(unsigned long addr, size_t len)
1718 {
1719 	struct mm_struct *mm = current->mm;
1720 	int ret;
1721 
1722 	down_write(&mm->mmap_sem);
1723 	ret = do_munmap(mm, addr, len);
1724 	up_write(&mm->mmap_sem);
1725 	return ret;
1726 }
1727 EXPORT_SYMBOL(vm_munmap);
1728 
1729 SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
1730 {
1731 	return vm_munmap(addr, len);
1732 }
1733 
1734 /*
1735  * release all the mappings made in a process's VM space
1736  */
1737 void exit_mmap(struct mm_struct *mm)
1738 {
1739 	struct vm_area_struct *vma;
1740 
1741 	if (!mm)
1742 		return;
1743 
1744 	kenter("");
1745 
1746 	mm->total_vm = 0;
1747 
1748 	while ((vma = mm->mmap)) {
1749 		mm->mmap = vma->vm_next;
1750 		delete_vma_from_mm(vma);
1751 		delete_vma(mm, vma);
1752 		cond_resched();
1753 	}
1754 
1755 	kleave("");
1756 }
1757 
1758 unsigned long vm_brk(unsigned long addr, unsigned long len)
1759 {
1760 	return -ENOMEM;
1761 }
1762 
1763 /*
1764  * expand (or shrink) an existing mapping, potentially moving it at the same
1765  * time (controlled by the MREMAP_MAYMOVE flag and available VM space)
1766  *
1767  * under NOMMU conditions, we only permit changing a mapping's size, and only
1768  * as long as it stays within the region allocated by do_mmap_private() and the
1769  * block is not shareable
1770  *
1771  * MREMAP_FIXED is not supported under NOMMU conditions
1772  */
1773 unsigned long do_mremap(unsigned long addr,
1774 			unsigned long old_len, unsigned long new_len,
1775 			unsigned long flags, unsigned long new_addr)
1776 {
1777 	struct vm_area_struct *vma;
1778 
1779 	/* insanity checks first */
1780 	old_len = PAGE_ALIGN(old_len);
1781 	new_len = PAGE_ALIGN(new_len);
1782 	if (old_len == 0 || new_len == 0)
1783 		return (unsigned long) -EINVAL;
1784 
1785 	if (addr & ~PAGE_MASK)
1786 		return -EINVAL;
1787 
1788 	if (flags & MREMAP_FIXED && new_addr != addr)
1789 		return (unsigned long) -EINVAL;
1790 
1791 	vma = find_vma_exact(current->mm, addr, old_len);
1792 	if (!vma)
1793 		return (unsigned long) -EINVAL;
1794 
1795 	if (vma->vm_end != vma->vm_start + old_len)
1796 		return (unsigned long) -EFAULT;
1797 
1798 	if (vma->vm_flags & VM_MAYSHARE)
1799 		return (unsigned long) -EPERM;
1800 
1801 	if (new_len > vma->vm_region->vm_end - vma->vm_region->vm_start)
1802 		return (unsigned long) -ENOMEM;
1803 
1804 	/* all checks complete - do it */
1805 	vma->vm_end = vma->vm_start + new_len;
1806 	return vma->vm_start;
1807 }
1808 EXPORT_SYMBOL(do_mremap);
1809 
1810 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
1811 		unsigned long, new_len, unsigned long, flags,
1812 		unsigned long, new_addr)
1813 {
1814 	unsigned long ret;
1815 
1816 	down_write(&current->mm->mmap_sem);
1817 	ret = do_mremap(addr, old_len, new_len, flags, new_addr);
1818 	up_write(&current->mm->mmap_sem);
1819 	return ret;
1820 }
1821 
1822 struct page *follow_page_mask(struct vm_area_struct *vma,
1823 			      unsigned long address, unsigned int flags,
1824 			      unsigned int *page_mask)
1825 {
1826 	*page_mask = 0;
1827 	return NULL;
1828 }
1829 
1830 int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
1831 		unsigned long pfn, unsigned long size, pgprot_t prot)
1832 {
1833 	if (addr != (pfn << PAGE_SHIFT))
1834 		return -EINVAL;
1835 
1836 	vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
1837 	return 0;
1838 }
1839 EXPORT_SYMBOL(remap_pfn_range);
1840 
1841 int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
1842 			unsigned long pgoff)
1843 {
1844 	unsigned int size = vma->vm_end - vma->vm_start;
1845 
1846 	if (!(vma->vm_flags & VM_USERMAP))
1847 		return -EINVAL;
1848 
1849 	vma->vm_start = (unsigned long)(addr + (pgoff << PAGE_SHIFT));
1850 	vma->vm_end = vma->vm_start + size;
1851 
1852 	return 0;
1853 }
1854 EXPORT_SYMBOL(remap_vmalloc_range);
1855 
1856 unsigned long arch_get_unmapped_area(struct file *file, unsigned long addr,
1857 	unsigned long len, unsigned long pgoff, unsigned long flags)
1858 {
1859 	return -ENOMEM;
1860 }
1861 
1862 void arch_unmap_area(struct mm_struct *mm, unsigned long addr)
1863 {
1864 }
1865 
1866 void unmap_mapping_range(struct address_space *mapping,
1867 			 loff_t const holebegin, loff_t const holelen,
1868 			 int even_cows)
1869 {
1870 }
1871 EXPORT_SYMBOL(unmap_mapping_range);
1872 
1873 /*
1874  * Check that a process has enough memory to allocate a new virtual
1875  * mapping. 0 means there is enough memory for the allocation to
1876  * succeed and -ENOMEM implies there is not.
1877  *
1878  * We currently support three overcommit policies, which are set via the
1879  * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-accounting
1880  *
1881  * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
1882  * Additional code 2002 Jul 20 by Robert Love.
1883  *
1884  * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
1885  *
1886  * Note this is a helper function intended to be used by LSMs which
1887  * wish to use this logic.
1888  */
1889 int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
1890 {
1891 	unsigned long free, allowed;
1892 
1893 	vm_acct_memory(pages);
1894 
1895 	/*
1896 	 * Sometimes we want to use more memory than we have
1897 	 */
1898 	if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
1899 		return 0;
1900 
1901 	if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
1902 		free = global_page_state(NR_FREE_PAGES);
1903 		free += global_page_state(NR_FILE_PAGES);
1904 
1905 		/*
1906 		 * shmem pages shouldn't be counted as free in this
1907 		 * case, they can't be purged, only swapped out, and
1908 		 * that won't affect the overall amount of available
1909 		 * memory in the system.
1910 		 */
1911 		free -= global_page_state(NR_SHMEM);
1912 
1913 		free += get_nr_swap_pages();
1914 
1915 		/*
1916 		 * Any slabs which are created with the
1917 		 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
1918 		 * which are reclaimable, under pressure.  The dentry
1919 		 * cache and most inode caches should fall into this
1920 		 */
1921 		free += global_page_state(NR_SLAB_RECLAIMABLE);
1922 
1923 		/*
1924 		 * Leave reserved pages. The pages are not for anonymous pages.
1925 		 */
1926 		if (free <= totalreserve_pages)
1927 			goto error;
1928 		else
1929 			free -= totalreserve_pages;
1930 
1931 		/*
1932 		 * Leave the last 3% for root
1933 		 */
1934 		if (!cap_sys_admin)
1935 			free -= free / 32;
1936 
1937 		if (free > pages)
1938 			return 0;
1939 
1940 		goto error;
1941 	}
1942 
1943 	allowed = totalram_pages * sysctl_overcommit_ratio / 100;
1944 	/*
1945 	 * Leave the last 3% for root
1946 	 */
1947 	if (!cap_sys_admin)
1948 		allowed -= allowed / 32;
1949 	allowed += total_swap_pages;
1950 
1951 	/* Don't let a single process grow too big:
1952 	   leave 3% of the size of this process for other processes */
1953 	if (mm)
1954 		allowed -= mm->total_vm / 32;
1955 
1956 	if (percpu_counter_read_positive(&vm_committed_as) < allowed)
1957 		return 0;
1958 
1959 error:
1960 	vm_unacct_memory(pages);
1961 
1962 	return -ENOMEM;
1963 }
1964 
1965 int in_gate_area_no_mm(unsigned long addr)
1966 {
1967 	return 0;
1968 }
1969 
1970 int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1971 {
1972 	BUG();
1973 	return 0;
1974 }
1975 EXPORT_SYMBOL(filemap_fault);
1976 
1977 int generic_file_remap_pages(struct vm_area_struct *vma, unsigned long addr,
1978 			     unsigned long size, pgoff_t pgoff)
1979 {
1980 	BUG();
1981 	return 0;
1982 }
1983 EXPORT_SYMBOL(generic_file_remap_pages);
1984 
1985 static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
1986 		unsigned long addr, void *buf, int len, int write)
1987 {
1988 	struct vm_area_struct *vma;
1989 
1990 	down_read(&mm->mmap_sem);
1991 
1992 	/* the access must start within one of the target process's mappings */
1993 	vma = find_vma(mm, addr);
1994 	if (vma) {
1995 		/* don't overrun this mapping */
1996 		if (addr + len >= vma->vm_end)
1997 			len = vma->vm_end - addr;
1998 
1999 		/* only read or write mappings where it is permitted */
2000 		if (write && vma->vm_flags & VM_MAYWRITE)
2001 			copy_to_user_page(vma, NULL, addr,
2002 					 (void *) addr, buf, len);
2003 		else if (!write && vma->vm_flags & VM_MAYREAD)
2004 			copy_from_user_page(vma, NULL, addr,
2005 					    buf, (void *) addr, len);
2006 		else
2007 			len = 0;
2008 	} else {
2009 		len = 0;
2010 	}
2011 
2012 	up_read(&mm->mmap_sem);
2013 
2014 	return len;
2015 }
2016 
2017 /**
2018  * @access_remote_vm - access another process' address space
2019  * @mm:		the mm_struct of the target address space
2020  * @addr:	start address to access
2021  * @buf:	source or destination buffer
2022  * @len:	number of bytes to transfer
2023  * @write:	whether the access is a write
2024  *
2025  * The caller must hold a reference on @mm.
2026  */
2027 int access_remote_vm(struct mm_struct *mm, unsigned long addr,
2028 		void *buf, int len, int write)
2029 {
2030 	return __access_remote_vm(NULL, mm, addr, buf, len, write);
2031 }
2032 
2033 /*
2034  * Access another process' address space.
2035  * - source/target buffer must be kernel space
2036  */
2037 int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
2038 {
2039 	struct mm_struct *mm;
2040 
2041 	if (addr + len < addr)
2042 		return 0;
2043 
2044 	mm = get_task_mm(tsk);
2045 	if (!mm)
2046 		return 0;
2047 
2048 	len = __access_remote_vm(tsk, mm, addr, buf, len, write);
2049 
2050 	mmput(mm);
2051 	return len;
2052 }
2053 
2054 /**
2055  * nommu_shrink_inode_mappings - Shrink the shared mappings on an inode
2056  * @inode: The inode to check
2057  * @size: The current filesize of the inode
2058  * @newsize: The proposed filesize of the inode
2059  *
2060  * Check the shared mappings on an inode on behalf of a shrinking truncate to
2061  * make sure that that any outstanding VMAs aren't broken and then shrink the
2062  * vm_regions that extend that beyond so that do_mmap_pgoff() doesn't
2063  * automatically grant mappings that are too large.
2064  */
2065 int nommu_shrink_inode_mappings(struct inode *inode, size_t size,
2066 				size_t newsize)
2067 {
2068 	struct vm_area_struct *vma;
2069 	struct vm_region *region;
2070 	pgoff_t low, high;
2071 	size_t r_size, r_top;
2072 
2073 	low = newsize >> PAGE_SHIFT;
2074 	high = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
2075 
2076 	down_write(&nommu_region_sem);
2077 	mutex_lock(&inode->i_mapping->i_mmap_mutex);
2078 
2079 	/* search for VMAs that fall within the dead zone */
2080 	vma_interval_tree_foreach(vma, &inode->i_mapping->i_mmap, low, high) {
2081 		/* found one - only interested if it's shared out of the page
2082 		 * cache */
2083 		if (vma->vm_flags & VM_SHARED) {
2084 			mutex_unlock(&inode->i_mapping->i_mmap_mutex);
2085 			up_write(&nommu_region_sem);
2086 			return -ETXTBSY; /* not quite true, but near enough */
2087 		}
2088 	}
2089 
2090 	/* reduce any regions that overlap the dead zone - if in existence,
2091 	 * these will be pointed to by VMAs that don't overlap the dead zone
2092 	 *
2093 	 * we don't check for any regions that start beyond the EOF as there
2094 	 * shouldn't be any
2095 	 */
2096 	vma_interval_tree_foreach(vma, &inode->i_mapping->i_mmap,
2097 				  0, ULONG_MAX) {
2098 		if (!(vma->vm_flags & VM_SHARED))
2099 			continue;
2100 
2101 		region = vma->vm_region;
2102 		r_size = region->vm_top - region->vm_start;
2103 		r_top = (region->vm_pgoff << PAGE_SHIFT) + r_size;
2104 
2105 		if (r_top > newsize) {
2106 			region->vm_top -= r_top - newsize;
2107 			if (region->vm_end > region->vm_top)
2108 				region->vm_end = region->vm_top;
2109 		}
2110 	}
2111 
2112 	mutex_unlock(&inode->i_mapping->i_mmap_mutex);
2113 	up_write(&nommu_region_sem);
2114 	return 0;
2115 }
2116