xref: /openbmc/linux/mm/mmap.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
1 /*
2  * mm/mmap.c
3  *
4  * Written by obz.
5  *
6  * Address space accounting code	<alan@redhat.com>
7  */
8 
9 #include <linux/slab.h>
10 #include <linux/mm.h>
11 #include <linux/shm.h>
12 #include <linux/mman.h>
13 #include <linux/pagemap.h>
14 #include <linux/swap.h>
15 #include <linux/syscalls.h>
16 #include <linux/capability.h>
17 #include <linux/init.h>
18 #include <linux/file.h>
19 #include <linux/fs.h>
20 #include <linux/personality.h>
21 #include <linux/security.h>
22 #include <linux/hugetlb.h>
23 #include <linux/profile.h>
24 #include <linux/module.h>
25 #include <linux/mount.h>
26 #include <linux/mempolicy.h>
27 #include <linux/rmap.h>
28 
29 #include <asm/uaccess.h>
30 #include <asm/cacheflush.h>
31 #include <asm/tlb.h>
32 #include <asm/mmu_context.h>
33 
34 #ifndef arch_mmap_check
35 #define arch_mmap_check(addr, len, flags)	(0)
36 #endif
37 
38 static void unmap_region(struct mm_struct *mm,
39 		struct vm_area_struct *vma, struct vm_area_struct *prev,
40 		unsigned long start, unsigned long end);
41 
42 /*
43  * WARNING: the debugging will use recursive algorithms so never enable this
44  * unless you know what you are doing.
45  */
46 #undef DEBUG_MM_RB
47 
48 /* description of effects of mapping type and prot in current implementation.
49  * this is due to the limited x86 page protection hardware.  The expected
50  * behavior is in parens:
51  *
52  * map_type	prot
53  *		PROT_NONE	PROT_READ	PROT_WRITE	PROT_EXEC
54  * MAP_SHARED	r: (no) no	r: (yes) yes	r: (no) yes	r: (no) yes
55  *		w: (no) no	w: (no) no	w: (yes) yes	w: (no) no
56  *		x: (no) no	x: (no) yes	x: (no) yes	x: (yes) yes
57  *
58  * MAP_PRIVATE	r: (no) no	r: (yes) yes	r: (no) yes	r: (no) yes
59  *		w: (no) no	w: (no) no	w: (copy) copy	w: (no) no
60  *		x: (no) no	x: (no) yes	x: (no) yes	x: (yes) yes
61  *
62  */
63 pgprot_t protection_map[16] = {
64 	__P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
65 	__S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
66 };
67 
68 pgprot_t vm_get_page_prot(unsigned long vm_flags)
69 {
70 	return protection_map[vm_flags &
71 				(VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)];
72 }
73 EXPORT_SYMBOL(vm_get_page_prot);
74 
75 int sysctl_overcommit_memory = OVERCOMMIT_GUESS;  /* heuristic overcommit */
76 int sysctl_overcommit_ratio = 50;	/* default is 50% */
77 int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
78 atomic_t vm_committed_space = ATOMIC_INIT(0);
79 
80 /*
81  * Check that a process has enough memory to allocate a new virtual
82  * mapping. 0 means there is enough memory for the allocation to
83  * succeed and -ENOMEM implies there is not.
84  *
85  * We currently support three overcommit policies, which are set via the
86  * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-accounting
87  *
88  * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
89  * Additional code 2002 Jul 20 by Robert Love.
90  *
91  * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
92  *
93  * Note this is a helper function intended to be used by LSMs which
94  * wish to use this logic.
95  */
96 int __vm_enough_memory(long pages, int cap_sys_admin)
97 {
98 	unsigned long free, allowed;
99 
100 	vm_acct_memory(pages);
101 
102 	/*
103 	 * Sometimes we want to use more memory than we have
104 	 */
105 	if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
106 		return 0;
107 
108 	if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
109 		unsigned long n;
110 
111 		free = global_page_state(NR_FILE_PAGES);
112 		free += nr_swap_pages;
113 
114 		/*
115 		 * Any slabs which are created with the
116 		 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
117 		 * which are reclaimable, under pressure.  The dentry
118 		 * cache and most inode caches should fall into this
119 		 */
120 		free += global_page_state(NR_SLAB_RECLAIMABLE);
121 
122 		/*
123 		 * Leave the last 3% for root
124 		 */
125 		if (!cap_sys_admin)
126 			free -= free / 32;
127 
128 		if (free > pages)
129 			return 0;
130 
131 		/*
132 		 * nr_free_pages() is very expensive on large systems,
133 		 * only call if we're about to fail.
134 		 */
135 		n = nr_free_pages();
136 
137 		/*
138 		 * Leave reserved pages. The pages are not for anonymous pages.
139 		 */
140 		if (n <= totalreserve_pages)
141 			goto error;
142 		else
143 			n -= totalreserve_pages;
144 
145 		/*
146 		 * Leave the last 3% for root
147 		 */
148 		if (!cap_sys_admin)
149 			n -= n / 32;
150 		free += n;
151 
152 		if (free > pages)
153 			return 0;
154 
155 		goto error;
156 	}
157 
158 	allowed = (totalram_pages - hugetlb_total_pages())
159 	       	* sysctl_overcommit_ratio / 100;
160 	/*
161 	 * Leave the last 3% for root
162 	 */
163 	if (!cap_sys_admin)
164 		allowed -= allowed / 32;
165 	allowed += total_swap_pages;
166 
167 	/* Don't let a single process grow too big:
168 	   leave 3% of the size of this process for other processes */
169 	allowed -= current->mm->total_vm / 32;
170 
171 	/*
172 	 * cast `allowed' as a signed long because vm_committed_space
173 	 * sometimes has a negative value
174 	 */
175 	if (atomic_read(&vm_committed_space) < (long)allowed)
176 		return 0;
177 error:
178 	vm_unacct_memory(pages);
179 
180 	return -ENOMEM;
181 }
182 
183 EXPORT_SYMBOL(__vm_enough_memory);
184 
185 /*
186  * Requires inode->i_mapping->i_mmap_lock
187  */
188 static void __remove_shared_vm_struct(struct vm_area_struct *vma,
189 		struct file *file, struct address_space *mapping)
190 {
191 	if (vma->vm_flags & VM_DENYWRITE)
192 		atomic_inc(&file->f_path.dentry->d_inode->i_writecount);
193 	if (vma->vm_flags & VM_SHARED)
194 		mapping->i_mmap_writable--;
195 
196 	flush_dcache_mmap_lock(mapping);
197 	if (unlikely(vma->vm_flags & VM_NONLINEAR))
198 		list_del_init(&vma->shared.vm_set.list);
199 	else
200 		vma_prio_tree_remove(vma, &mapping->i_mmap);
201 	flush_dcache_mmap_unlock(mapping);
202 }
203 
204 /*
205  * Unlink a file-based vm structure from its prio_tree, to hide
206  * vma from rmap and vmtruncate before freeing its page tables.
207  */
208 void unlink_file_vma(struct vm_area_struct *vma)
209 {
210 	struct file *file = vma->vm_file;
211 
212 	if (file) {
213 		struct address_space *mapping = file->f_mapping;
214 		spin_lock(&mapping->i_mmap_lock);
215 		__remove_shared_vm_struct(vma, file, mapping);
216 		spin_unlock(&mapping->i_mmap_lock);
217 	}
218 }
219 
220 /*
221  * Close a vm structure and free it, returning the next.
222  */
223 static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
224 {
225 	struct vm_area_struct *next = vma->vm_next;
226 
227 	might_sleep();
228 	if (vma->vm_ops && vma->vm_ops->close)
229 		vma->vm_ops->close(vma);
230 	if (vma->vm_file)
231 		fput(vma->vm_file);
232 	mpol_free(vma_policy(vma));
233 	kmem_cache_free(vm_area_cachep, vma);
234 	return next;
235 }
236 
237 asmlinkage unsigned long sys_brk(unsigned long brk)
238 {
239 	unsigned long rlim, retval;
240 	unsigned long newbrk, oldbrk;
241 	struct mm_struct *mm = current->mm;
242 
243 	down_write(&mm->mmap_sem);
244 
245 	if (brk < mm->end_code)
246 		goto out;
247 
248 	/*
249 	 * Check against rlimit here. If this check is done later after the test
250 	 * of oldbrk with newbrk then it can escape the test and let the data
251 	 * segment grow beyond its set limit the in case where the limit is
252 	 * not page aligned -Ram Gupta
253 	 */
254 	rlim = current->signal->rlim[RLIMIT_DATA].rlim_cur;
255 	if (rlim < RLIM_INFINITY && brk - mm->start_data > rlim)
256 		goto out;
257 
258 	newbrk = PAGE_ALIGN(brk);
259 	oldbrk = PAGE_ALIGN(mm->brk);
260 	if (oldbrk == newbrk)
261 		goto set_brk;
262 
263 	/* Always allow shrinking brk. */
264 	if (brk <= mm->brk) {
265 		if (!do_munmap(mm, newbrk, oldbrk-newbrk))
266 			goto set_brk;
267 		goto out;
268 	}
269 
270 	/* Check against existing mmap mappings. */
271 	if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE))
272 		goto out;
273 
274 	/* Ok, looks good - let it rip. */
275 	if (do_brk(oldbrk, newbrk-oldbrk) != oldbrk)
276 		goto out;
277 set_brk:
278 	mm->brk = brk;
279 out:
280 	retval = mm->brk;
281 	up_write(&mm->mmap_sem);
282 	return retval;
283 }
284 
285 #ifdef DEBUG_MM_RB
286 static int browse_rb(struct rb_root *root)
287 {
288 	int i = 0, j;
289 	struct rb_node *nd, *pn = NULL;
290 	unsigned long prev = 0, pend = 0;
291 
292 	for (nd = rb_first(root); nd; nd = rb_next(nd)) {
293 		struct vm_area_struct *vma;
294 		vma = rb_entry(nd, struct vm_area_struct, vm_rb);
295 		if (vma->vm_start < prev)
296 			printk("vm_start %lx prev %lx\n", vma->vm_start, prev), i = -1;
297 		if (vma->vm_start < pend)
298 			printk("vm_start %lx pend %lx\n", vma->vm_start, pend);
299 		if (vma->vm_start > vma->vm_end)
300 			printk("vm_end %lx < vm_start %lx\n", vma->vm_end, vma->vm_start);
301 		i++;
302 		pn = nd;
303 		prev = vma->vm_start;
304 		pend = vma->vm_end;
305 	}
306 	j = 0;
307 	for (nd = pn; nd; nd = rb_prev(nd)) {
308 		j++;
309 	}
310 	if (i != j)
311 		printk("backwards %d, forwards %d\n", j, i), i = 0;
312 	return i;
313 }
314 
315 void validate_mm(struct mm_struct *mm)
316 {
317 	int bug = 0;
318 	int i = 0;
319 	struct vm_area_struct *tmp = mm->mmap;
320 	while (tmp) {
321 		tmp = tmp->vm_next;
322 		i++;
323 	}
324 	if (i != mm->map_count)
325 		printk("map_count %d vm_next %d\n", mm->map_count, i), bug = 1;
326 	i = browse_rb(&mm->mm_rb);
327 	if (i != mm->map_count)
328 		printk("map_count %d rb %d\n", mm->map_count, i), bug = 1;
329 	BUG_ON(bug);
330 }
331 #else
332 #define validate_mm(mm) do { } while (0)
333 #endif
334 
335 static struct vm_area_struct *
336 find_vma_prepare(struct mm_struct *mm, unsigned long addr,
337 		struct vm_area_struct **pprev, struct rb_node ***rb_link,
338 		struct rb_node ** rb_parent)
339 {
340 	struct vm_area_struct * vma;
341 	struct rb_node ** __rb_link, * __rb_parent, * rb_prev;
342 
343 	__rb_link = &mm->mm_rb.rb_node;
344 	rb_prev = __rb_parent = NULL;
345 	vma = NULL;
346 
347 	while (*__rb_link) {
348 		struct vm_area_struct *vma_tmp;
349 
350 		__rb_parent = *__rb_link;
351 		vma_tmp = rb_entry(__rb_parent, struct vm_area_struct, vm_rb);
352 
353 		if (vma_tmp->vm_end > addr) {
354 			vma = vma_tmp;
355 			if (vma_tmp->vm_start <= addr)
356 				return vma;
357 			__rb_link = &__rb_parent->rb_left;
358 		} else {
359 			rb_prev = __rb_parent;
360 			__rb_link = &__rb_parent->rb_right;
361 		}
362 	}
363 
364 	*pprev = NULL;
365 	if (rb_prev)
366 		*pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
367 	*rb_link = __rb_link;
368 	*rb_parent = __rb_parent;
369 	return vma;
370 }
371 
372 static inline void
373 __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
374 		struct vm_area_struct *prev, struct rb_node *rb_parent)
375 {
376 	if (prev) {
377 		vma->vm_next = prev->vm_next;
378 		prev->vm_next = vma;
379 	} else {
380 		mm->mmap = vma;
381 		if (rb_parent)
382 			vma->vm_next = rb_entry(rb_parent,
383 					struct vm_area_struct, vm_rb);
384 		else
385 			vma->vm_next = NULL;
386 	}
387 }
388 
389 void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
390 		struct rb_node **rb_link, struct rb_node *rb_parent)
391 {
392 	rb_link_node(&vma->vm_rb, rb_parent, rb_link);
393 	rb_insert_color(&vma->vm_rb, &mm->mm_rb);
394 }
395 
396 static inline void __vma_link_file(struct vm_area_struct *vma)
397 {
398 	struct file * file;
399 
400 	file = vma->vm_file;
401 	if (file) {
402 		struct address_space *mapping = file->f_mapping;
403 
404 		if (vma->vm_flags & VM_DENYWRITE)
405 			atomic_dec(&file->f_path.dentry->d_inode->i_writecount);
406 		if (vma->vm_flags & VM_SHARED)
407 			mapping->i_mmap_writable++;
408 
409 		flush_dcache_mmap_lock(mapping);
410 		if (unlikely(vma->vm_flags & VM_NONLINEAR))
411 			vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
412 		else
413 			vma_prio_tree_insert(vma, &mapping->i_mmap);
414 		flush_dcache_mmap_unlock(mapping);
415 	}
416 }
417 
418 static void
419 __vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
420 	struct vm_area_struct *prev, struct rb_node **rb_link,
421 	struct rb_node *rb_parent)
422 {
423 	__vma_link_list(mm, vma, prev, rb_parent);
424 	__vma_link_rb(mm, vma, rb_link, rb_parent);
425 	__anon_vma_link(vma);
426 }
427 
428 static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
429 			struct vm_area_struct *prev, struct rb_node **rb_link,
430 			struct rb_node *rb_parent)
431 {
432 	struct address_space *mapping = NULL;
433 
434 	if (vma->vm_file)
435 		mapping = vma->vm_file->f_mapping;
436 
437 	if (mapping) {
438 		spin_lock(&mapping->i_mmap_lock);
439 		vma->vm_truncate_count = mapping->truncate_count;
440 	}
441 	anon_vma_lock(vma);
442 
443 	__vma_link(mm, vma, prev, rb_link, rb_parent);
444 	__vma_link_file(vma);
445 
446 	anon_vma_unlock(vma);
447 	if (mapping)
448 		spin_unlock(&mapping->i_mmap_lock);
449 
450 	mm->map_count++;
451 	validate_mm(mm);
452 }
453 
454 /*
455  * Helper for vma_adjust in the split_vma insert case:
456  * insert vm structure into list and rbtree and anon_vma,
457  * but it has already been inserted into prio_tree earlier.
458  */
459 static void
460 __insert_vm_struct(struct mm_struct * mm, struct vm_area_struct * vma)
461 {
462 	struct vm_area_struct * __vma, * prev;
463 	struct rb_node ** rb_link, * rb_parent;
464 
465 	__vma = find_vma_prepare(mm, vma->vm_start,&prev, &rb_link, &rb_parent);
466 	BUG_ON(__vma && __vma->vm_start < vma->vm_end);
467 	__vma_link(mm, vma, prev, rb_link, rb_parent);
468 	mm->map_count++;
469 }
470 
471 static inline void
472 __vma_unlink(struct mm_struct *mm, struct vm_area_struct *vma,
473 		struct vm_area_struct *prev)
474 {
475 	prev->vm_next = vma->vm_next;
476 	rb_erase(&vma->vm_rb, &mm->mm_rb);
477 	if (mm->mmap_cache == vma)
478 		mm->mmap_cache = prev;
479 }
480 
481 /*
482  * We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that
483  * is already present in an i_mmap tree without adjusting the tree.
484  * The following helper function should be used when such adjustments
485  * are necessary.  The "insert" vma (if any) is to be inserted
486  * before we drop the necessary locks.
487  */
488 void vma_adjust(struct vm_area_struct *vma, unsigned long start,
489 	unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert)
490 {
491 	struct mm_struct *mm = vma->vm_mm;
492 	struct vm_area_struct *next = vma->vm_next;
493 	struct vm_area_struct *importer = NULL;
494 	struct address_space *mapping = NULL;
495 	struct prio_tree_root *root = NULL;
496 	struct file *file = vma->vm_file;
497 	struct anon_vma *anon_vma = NULL;
498 	long adjust_next = 0;
499 	int remove_next = 0;
500 
501 	if (next && !insert) {
502 		if (end >= next->vm_end) {
503 			/*
504 			 * vma expands, overlapping all the next, and
505 			 * perhaps the one after too (mprotect case 6).
506 			 */
507 again:			remove_next = 1 + (end > next->vm_end);
508 			end = next->vm_end;
509 			anon_vma = next->anon_vma;
510 			importer = vma;
511 		} else if (end > next->vm_start) {
512 			/*
513 			 * vma expands, overlapping part of the next:
514 			 * mprotect case 5 shifting the boundary up.
515 			 */
516 			adjust_next = (end - next->vm_start) >> PAGE_SHIFT;
517 			anon_vma = next->anon_vma;
518 			importer = vma;
519 		} else if (end < vma->vm_end) {
520 			/*
521 			 * vma shrinks, and !insert tells it's not
522 			 * split_vma inserting another: so it must be
523 			 * mprotect case 4 shifting the boundary down.
524 			 */
525 			adjust_next = - ((vma->vm_end - end) >> PAGE_SHIFT);
526 			anon_vma = next->anon_vma;
527 			importer = next;
528 		}
529 	}
530 
531 	if (file) {
532 		mapping = file->f_mapping;
533 		if (!(vma->vm_flags & VM_NONLINEAR))
534 			root = &mapping->i_mmap;
535 		spin_lock(&mapping->i_mmap_lock);
536 		if (importer &&
537 		    vma->vm_truncate_count != next->vm_truncate_count) {
538 			/*
539 			 * unmap_mapping_range might be in progress:
540 			 * ensure that the expanding vma is rescanned.
541 			 */
542 			importer->vm_truncate_count = 0;
543 		}
544 		if (insert) {
545 			insert->vm_truncate_count = vma->vm_truncate_count;
546 			/*
547 			 * Put into prio_tree now, so instantiated pages
548 			 * are visible to arm/parisc __flush_dcache_page
549 			 * throughout; but we cannot insert into address
550 			 * space until vma start or end is updated.
551 			 */
552 			__vma_link_file(insert);
553 		}
554 	}
555 
556 	/*
557 	 * When changing only vma->vm_end, we don't really need
558 	 * anon_vma lock: but is that case worth optimizing out?
559 	 */
560 	if (vma->anon_vma)
561 		anon_vma = vma->anon_vma;
562 	if (anon_vma) {
563 		spin_lock(&anon_vma->lock);
564 		/*
565 		 * Easily overlooked: when mprotect shifts the boundary,
566 		 * make sure the expanding vma has anon_vma set if the
567 		 * shrinking vma had, to cover any anon pages imported.
568 		 */
569 		if (importer && !importer->anon_vma) {
570 			importer->anon_vma = anon_vma;
571 			__anon_vma_link(importer);
572 		}
573 	}
574 
575 	if (root) {
576 		flush_dcache_mmap_lock(mapping);
577 		vma_prio_tree_remove(vma, root);
578 		if (adjust_next)
579 			vma_prio_tree_remove(next, root);
580 	}
581 
582 	vma->vm_start = start;
583 	vma->vm_end = end;
584 	vma->vm_pgoff = pgoff;
585 	if (adjust_next) {
586 		next->vm_start += adjust_next << PAGE_SHIFT;
587 		next->vm_pgoff += adjust_next;
588 	}
589 
590 	if (root) {
591 		if (adjust_next)
592 			vma_prio_tree_insert(next, root);
593 		vma_prio_tree_insert(vma, root);
594 		flush_dcache_mmap_unlock(mapping);
595 	}
596 
597 	if (remove_next) {
598 		/*
599 		 * vma_merge has merged next into vma, and needs
600 		 * us to remove next before dropping the locks.
601 		 */
602 		__vma_unlink(mm, next, vma);
603 		if (file)
604 			__remove_shared_vm_struct(next, file, mapping);
605 		if (next->anon_vma)
606 			__anon_vma_merge(vma, next);
607 	} else if (insert) {
608 		/*
609 		 * split_vma has split insert from vma, and needs
610 		 * us to insert it before dropping the locks
611 		 * (it may either follow vma or precede it).
612 		 */
613 		__insert_vm_struct(mm, insert);
614 	}
615 
616 	if (anon_vma)
617 		spin_unlock(&anon_vma->lock);
618 	if (mapping)
619 		spin_unlock(&mapping->i_mmap_lock);
620 
621 	if (remove_next) {
622 		if (file)
623 			fput(file);
624 		mm->map_count--;
625 		mpol_free(vma_policy(next));
626 		kmem_cache_free(vm_area_cachep, next);
627 		/*
628 		 * In mprotect's case 6 (see comments on vma_merge),
629 		 * we must remove another next too. It would clutter
630 		 * up the code too much to do both in one go.
631 		 */
632 		if (remove_next == 2) {
633 			next = vma->vm_next;
634 			goto again;
635 		}
636 	}
637 
638 	validate_mm(mm);
639 }
640 
641 /*
642  * If the vma has a ->close operation then the driver probably needs to release
643  * per-vma resources, so we don't attempt to merge those.
644  */
645 #define VM_SPECIAL (VM_IO | VM_DONTEXPAND | VM_RESERVED | VM_PFNMAP)
646 
647 static inline int is_mergeable_vma(struct vm_area_struct *vma,
648 			struct file *file, unsigned long vm_flags)
649 {
650 	if (vma->vm_flags != vm_flags)
651 		return 0;
652 	if (vma->vm_file != file)
653 		return 0;
654 	if (vma->vm_ops && vma->vm_ops->close)
655 		return 0;
656 	return 1;
657 }
658 
659 static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1,
660 					struct anon_vma *anon_vma2)
661 {
662 	return !anon_vma1 || !anon_vma2 || (anon_vma1 == anon_vma2);
663 }
664 
665 /*
666  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
667  * in front of (at a lower virtual address and file offset than) the vma.
668  *
669  * We cannot merge two vmas if they have differently assigned (non-NULL)
670  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
671  *
672  * We don't check here for the merged mmap wrapping around the end of pagecache
673  * indices (16TB on ia32) because do_mmap_pgoff() does not permit mmap's which
674  * wrap, nor mmaps which cover the final page at index -1UL.
675  */
676 static int
677 can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags,
678 	struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff)
679 {
680 	if (is_mergeable_vma(vma, file, vm_flags) &&
681 	    is_mergeable_anon_vma(anon_vma, vma->anon_vma)) {
682 		if (vma->vm_pgoff == vm_pgoff)
683 			return 1;
684 	}
685 	return 0;
686 }
687 
688 /*
689  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
690  * beyond (at a higher virtual address and file offset than) the vma.
691  *
692  * We cannot merge two vmas if they have differently assigned (non-NULL)
693  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
694  */
695 static int
696 can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
697 	struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff)
698 {
699 	if (is_mergeable_vma(vma, file, vm_flags) &&
700 	    is_mergeable_anon_vma(anon_vma, vma->anon_vma)) {
701 		pgoff_t vm_pglen;
702 		vm_pglen = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
703 		if (vma->vm_pgoff + vm_pglen == vm_pgoff)
704 			return 1;
705 	}
706 	return 0;
707 }
708 
709 /*
710  * Given a mapping request (addr,end,vm_flags,file,pgoff), figure out
711  * whether that can be merged with its predecessor or its successor.
712  * Or both (it neatly fills a hole).
713  *
714  * In most cases - when called for mmap, brk or mremap - [addr,end) is
715  * certain not to be mapped by the time vma_merge is called; but when
716  * called for mprotect, it is certain to be already mapped (either at
717  * an offset within prev, or at the start of next), and the flags of
718  * this area are about to be changed to vm_flags - and the no-change
719  * case has already been eliminated.
720  *
721  * The following mprotect cases have to be considered, where AAAA is
722  * the area passed down from mprotect_fixup, never extending beyond one
723  * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
724  *
725  *     AAAA             AAAA                AAAA          AAAA
726  *    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPNNNNXXXX
727  *    cannot merge    might become    might become    might become
728  *                    PPNNNNNNNNNN    PPPPPPPPPPNN    PPPPPPPPPPPP 6 or
729  *    mmap, brk or    case 4 below    case 5 below    PPPPPPPPXXXX 7 or
730  *    mremap move:                                    PPPPNNNNNNNN 8
731  *        AAAA
732  *    PPPP    NNNN    PPPPPPPPPPPP    PPPPPPPPNNNN    PPPPNNNNNNNN
733  *    might become    case 1 below    case 2 below    case 3 below
734  *
735  * Odd one out? Case 8, because it extends NNNN but needs flags of XXXX:
736  * mprotect_fixup updates vm_flags & vm_page_prot on successful return.
737  */
738 struct vm_area_struct *vma_merge(struct mm_struct *mm,
739 			struct vm_area_struct *prev, unsigned long addr,
740 			unsigned long end, unsigned long vm_flags,
741 		     	struct anon_vma *anon_vma, struct file *file,
742 			pgoff_t pgoff, struct mempolicy *policy)
743 {
744 	pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
745 	struct vm_area_struct *area, *next;
746 
747 	/*
748 	 * We later require that vma->vm_flags == vm_flags,
749 	 * so this tests vma->vm_flags & VM_SPECIAL, too.
750 	 */
751 	if (vm_flags & VM_SPECIAL)
752 		return NULL;
753 
754 	if (prev)
755 		next = prev->vm_next;
756 	else
757 		next = mm->mmap;
758 	area = next;
759 	if (next && next->vm_end == end)		/* cases 6, 7, 8 */
760 		next = next->vm_next;
761 
762 	/*
763 	 * Can it merge with the predecessor?
764 	 */
765 	if (prev && prev->vm_end == addr &&
766   			mpol_equal(vma_policy(prev), policy) &&
767 			can_vma_merge_after(prev, vm_flags,
768 						anon_vma, file, pgoff)) {
769 		/*
770 		 * OK, it can.  Can we now merge in the successor as well?
771 		 */
772 		if (next && end == next->vm_start &&
773 				mpol_equal(policy, vma_policy(next)) &&
774 				can_vma_merge_before(next, vm_flags,
775 					anon_vma, file, pgoff+pglen) &&
776 				is_mergeable_anon_vma(prev->anon_vma,
777 						      next->anon_vma)) {
778 							/* cases 1, 6 */
779 			vma_adjust(prev, prev->vm_start,
780 				next->vm_end, prev->vm_pgoff, NULL);
781 		} else					/* cases 2, 5, 7 */
782 			vma_adjust(prev, prev->vm_start,
783 				end, prev->vm_pgoff, NULL);
784 		return prev;
785 	}
786 
787 	/*
788 	 * Can this new request be merged in front of next?
789 	 */
790 	if (next && end == next->vm_start &&
791  			mpol_equal(policy, vma_policy(next)) &&
792 			can_vma_merge_before(next, vm_flags,
793 					anon_vma, file, pgoff+pglen)) {
794 		if (prev && addr < prev->vm_end)	/* case 4 */
795 			vma_adjust(prev, prev->vm_start,
796 				addr, prev->vm_pgoff, NULL);
797 		else					/* cases 3, 8 */
798 			vma_adjust(area, addr, next->vm_end,
799 				next->vm_pgoff - pglen, NULL);
800 		return area;
801 	}
802 
803 	return NULL;
804 }
805 
806 /*
807  * find_mergeable_anon_vma is used by anon_vma_prepare, to check
808  * neighbouring vmas for a suitable anon_vma, before it goes off
809  * to allocate a new anon_vma.  It checks because a repetitive
810  * sequence of mprotects and faults may otherwise lead to distinct
811  * anon_vmas being allocated, preventing vma merge in subsequent
812  * mprotect.
813  */
814 struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
815 {
816 	struct vm_area_struct *near;
817 	unsigned long vm_flags;
818 
819 	near = vma->vm_next;
820 	if (!near)
821 		goto try_prev;
822 
823 	/*
824 	 * Since only mprotect tries to remerge vmas, match flags
825 	 * which might be mprotected into each other later on.
826 	 * Neither mlock nor madvise tries to remerge at present,
827 	 * so leave their flags as obstructing a merge.
828 	 */
829 	vm_flags = vma->vm_flags & ~(VM_READ|VM_WRITE|VM_EXEC);
830 	vm_flags |= near->vm_flags & (VM_READ|VM_WRITE|VM_EXEC);
831 
832 	if (near->anon_vma && vma->vm_end == near->vm_start &&
833  			mpol_equal(vma_policy(vma), vma_policy(near)) &&
834 			can_vma_merge_before(near, vm_flags,
835 				NULL, vma->vm_file, vma->vm_pgoff +
836 				((vma->vm_end - vma->vm_start) >> PAGE_SHIFT)))
837 		return near->anon_vma;
838 try_prev:
839 	/*
840 	 * It is potentially slow to have to call find_vma_prev here.
841 	 * But it's only on the first write fault on the vma, not
842 	 * every time, and we could devise a way to avoid it later
843 	 * (e.g. stash info in next's anon_vma_node when assigning
844 	 * an anon_vma, or when trying vma_merge).  Another time.
845 	 */
846 	BUG_ON(find_vma_prev(vma->vm_mm, vma->vm_start, &near) != vma);
847 	if (!near)
848 		goto none;
849 
850 	vm_flags = vma->vm_flags & ~(VM_READ|VM_WRITE|VM_EXEC);
851 	vm_flags |= near->vm_flags & (VM_READ|VM_WRITE|VM_EXEC);
852 
853 	if (near->anon_vma && near->vm_end == vma->vm_start &&
854   			mpol_equal(vma_policy(near), vma_policy(vma)) &&
855 			can_vma_merge_after(near, vm_flags,
856 				NULL, vma->vm_file, vma->vm_pgoff))
857 		return near->anon_vma;
858 none:
859 	/*
860 	 * There's no absolute need to look only at touching neighbours:
861 	 * we could search further afield for "compatible" anon_vmas.
862 	 * But it would probably just be a waste of time searching,
863 	 * or lead to too many vmas hanging off the same anon_vma.
864 	 * We're trying to allow mprotect remerging later on,
865 	 * not trying to minimize memory used for anon_vmas.
866 	 */
867 	return NULL;
868 }
869 
870 #ifdef CONFIG_PROC_FS
871 void vm_stat_account(struct mm_struct *mm, unsigned long flags,
872 						struct file *file, long pages)
873 {
874 	const unsigned long stack_flags
875 		= VM_STACK_FLAGS & (VM_GROWSUP|VM_GROWSDOWN);
876 
877 	if (file) {
878 		mm->shared_vm += pages;
879 		if ((flags & (VM_EXEC|VM_WRITE)) == VM_EXEC)
880 			mm->exec_vm += pages;
881 	} else if (flags & stack_flags)
882 		mm->stack_vm += pages;
883 	if (flags & (VM_RESERVED|VM_IO))
884 		mm->reserved_vm += pages;
885 }
886 #endif /* CONFIG_PROC_FS */
887 
888 /*
889  * The caller must hold down_write(current->mm->mmap_sem).
890  */
891 
892 unsigned long do_mmap_pgoff(struct file * file, unsigned long addr,
893 			unsigned long len, unsigned long prot,
894 			unsigned long flags, unsigned long pgoff)
895 {
896 	struct mm_struct * mm = current->mm;
897 	struct vm_area_struct * vma, * prev;
898 	struct inode *inode;
899 	unsigned int vm_flags;
900 	int correct_wcount = 0;
901 	int error;
902 	struct rb_node ** rb_link, * rb_parent;
903 	int accountable = 1;
904 	unsigned long charged = 0, reqprot = prot;
905 
906 	/*
907 	 * Does the application expect PROT_READ to imply PROT_EXEC?
908 	 *
909 	 * (the exception is when the underlying filesystem is noexec
910 	 *  mounted, in which case we dont add PROT_EXEC.)
911 	 */
912 	if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
913 		if (!(file && (file->f_path.mnt->mnt_flags & MNT_NOEXEC)))
914 			prot |= PROT_EXEC;
915 
916 	if (!len)
917 		return -EINVAL;
918 
919 	error = arch_mmap_check(addr, len, flags);
920 	if (error)
921 		return error;
922 
923 	/* Careful about overflows.. */
924 	len = PAGE_ALIGN(len);
925 	if (!len || len > TASK_SIZE)
926 		return -ENOMEM;
927 
928 	/* offset overflow? */
929 	if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
930                return -EOVERFLOW;
931 
932 	/* Too many mappings? */
933 	if (mm->map_count > sysctl_max_map_count)
934 		return -ENOMEM;
935 
936 	/* Obtain the address to map to. we verify (or select) it and ensure
937 	 * that it represents a valid section of the address space.
938 	 */
939 	addr = get_unmapped_area(file, addr, len, pgoff, flags);
940 	if (addr & ~PAGE_MASK)
941 		return addr;
942 
943 	/* Do simple checking here so the lower-level routines won't have
944 	 * to. we assume access permissions have been handled by the open
945 	 * of the memory object, so we don't do any here.
946 	 */
947 	vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags) |
948 			mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
949 
950 	if (flags & MAP_LOCKED) {
951 		if (!can_do_mlock())
952 			return -EPERM;
953 		vm_flags |= VM_LOCKED;
954 	}
955 	/* mlock MCL_FUTURE? */
956 	if (vm_flags & VM_LOCKED) {
957 		unsigned long locked, lock_limit;
958 		locked = len >> PAGE_SHIFT;
959 		locked += mm->locked_vm;
960 		lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
961 		lock_limit >>= PAGE_SHIFT;
962 		if (locked > lock_limit && !capable(CAP_IPC_LOCK))
963 			return -EAGAIN;
964 	}
965 
966 	inode = file ? file->f_path.dentry->d_inode : NULL;
967 
968 	if (file) {
969 		switch (flags & MAP_TYPE) {
970 		case MAP_SHARED:
971 			if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE))
972 				return -EACCES;
973 
974 			/*
975 			 * Make sure we don't allow writing to an append-only
976 			 * file..
977 			 */
978 			if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE))
979 				return -EACCES;
980 
981 			/*
982 			 * Make sure there are no mandatory locks on the file.
983 			 */
984 			if (locks_verify_locked(inode))
985 				return -EAGAIN;
986 
987 			vm_flags |= VM_SHARED | VM_MAYSHARE;
988 			if (!(file->f_mode & FMODE_WRITE))
989 				vm_flags &= ~(VM_MAYWRITE | VM_SHARED);
990 
991 			/* fall through */
992 		case MAP_PRIVATE:
993 			if (!(file->f_mode & FMODE_READ))
994 				return -EACCES;
995 			if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) {
996 				if (vm_flags & VM_EXEC)
997 					return -EPERM;
998 				vm_flags &= ~VM_MAYEXEC;
999 			}
1000 			if (is_file_hugepages(file))
1001 				accountable = 0;
1002 
1003 			if (!file->f_op || !file->f_op->mmap)
1004 				return -ENODEV;
1005 			break;
1006 
1007 		default:
1008 			return -EINVAL;
1009 		}
1010 	} else {
1011 		switch (flags & MAP_TYPE) {
1012 		case MAP_SHARED:
1013 			vm_flags |= VM_SHARED | VM_MAYSHARE;
1014 			break;
1015 		case MAP_PRIVATE:
1016 			/*
1017 			 * Set pgoff according to addr for anon_vma.
1018 			 */
1019 			pgoff = addr >> PAGE_SHIFT;
1020 			break;
1021 		default:
1022 			return -EINVAL;
1023 		}
1024 	}
1025 
1026 	error = security_file_mmap(file, reqprot, prot, flags);
1027 	if (error)
1028 		return error;
1029 
1030 	/* Clear old maps */
1031 	error = -ENOMEM;
1032 munmap_back:
1033 	vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
1034 	if (vma && vma->vm_start < addr + len) {
1035 		if (do_munmap(mm, addr, len))
1036 			return -ENOMEM;
1037 		goto munmap_back;
1038 	}
1039 
1040 	/* Check against address space limit. */
1041 	if (!may_expand_vm(mm, len >> PAGE_SHIFT))
1042 		return -ENOMEM;
1043 
1044 	if (accountable && (!(flags & MAP_NORESERVE) ||
1045 			    sysctl_overcommit_memory == OVERCOMMIT_NEVER)) {
1046 		if (vm_flags & VM_SHARED) {
1047 			/* Check memory availability in shmem_file_setup? */
1048 			vm_flags |= VM_ACCOUNT;
1049 		} else if (vm_flags & VM_WRITE) {
1050 			/*
1051 			 * Private writable mapping: check memory availability
1052 			 */
1053 			charged = len >> PAGE_SHIFT;
1054 			if (security_vm_enough_memory(charged))
1055 				return -ENOMEM;
1056 			vm_flags |= VM_ACCOUNT;
1057 		}
1058 	}
1059 
1060 	/*
1061 	 * Can we just expand an old private anonymous mapping?
1062 	 * The VM_SHARED test is necessary because shmem_zero_setup
1063 	 * will create the file object for a shared anonymous map below.
1064 	 */
1065 	if (!file && !(vm_flags & VM_SHARED) &&
1066 	    vma_merge(mm, prev, addr, addr + len, vm_flags,
1067 					NULL, NULL, pgoff, NULL))
1068 		goto out;
1069 
1070 	/*
1071 	 * Determine the object being mapped and call the appropriate
1072 	 * specific mapper. the address has already been validated, but
1073 	 * not unmapped, but the maps are removed from the list.
1074 	 */
1075 	vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
1076 	if (!vma) {
1077 		error = -ENOMEM;
1078 		goto unacct_error;
1079 	}
1080 
1081 	vma->vm_mm = mm;
1082 	vma->vm_start = addr;
1083 	vma->vm_end = addr + len;
1084 	vma->vm_flags = vm_flags;
1085 	vma->vm_page_prot = protection_map[vm_flags &
1086 				(VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)];
1087 	vma->vm_pgoff = pgoff;
1088 
1089 	if (file) {
1090 		error = -EINVAL;
1091 		if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1092 			goto free_vma;
1093 		if (vm_flags & VM_DENYWRITE) {
1094 			error = deny_write_access(file);
1095 			if (error)
1096 				goto free_vma;
1097 			correct_wcount = 1;
1098 		}
1099 		vma->vm_file = file;
1100 		get_file(file);
1101 		error = file->f_op->mmap(file, vma);
1102 		if (error)
1103 			goto unmap_and_free_vma;
1104 	} else if (vm_flags & VM_SHARED) {
1105 		error = shmem_zero_setup(vma);
1106 		if (error)
1107 			goto free_vma;
1108 	}
1109 
1110 	/* We set VM_ACCOUNT in a shared mapping's vm_flags, to inform
1111 	 * shmem_zero_setup (perhaps called through /dev/zero's ->mmap)
1112 	 * that memory reservation must be checked; but that reservation
1113 	 * belongs to shared memory object, not to vma: so now clear it.
1114 	 */
1115 	if ((vm_flags & (VM_SHARED|VM_ACCOUNT)) == (VM_SHARED|VM_ACCOUNT))
1116 		vma->vm_flags &= ~VM_ACCOUNT;
1117 
1118 	/* Can addr have changed??
1119 	 *
1120 	 * Answer: Yes, several device drivers can do it in their
1121 	 *         f_op->mmap method. -DaveM
1122 	 */
1123 	addr = vma->vm_start;
1124 	pgoff = vma->vm_pgoff;
1125 	vm_flags = vma->vm_flags;
1126 
1127 	if (vma_wants_writenotify(vma))
1128 		vma->vm_page_prot =
1129 			protection_map[vm_flags & (VM_READ|VM_WRITE|VM_EXEC)];
1130 
1131 	if (!file || !vma_merge(mm, prev, addr, vma->vm_end,
1132 			vma->vm_flags, NULL, file, pgoff, vma_policy(vma))) {
1133 		file = vma->vm_file;
1134 		vma_link(mm, vma, prev, rb_link, rb_parent);
1135 		if (correct_wcount)
1136 			atomic_inc(&inode->i_writecount);
1137 	} else {
1138 		if (file) {
1139 			if (correct_wcount)
1140 				atomic_inc(&inode->i_writecount);
1141 			fput(file);
1142 		}
1143 		mpol_free(vma_policy(vma));
1144 		kmem_cache_free(vm_area_cachep, vma);
1145 	}
1146 out:
1147 	mm->total_vm += len >> PAGE_SHIFT;
1148 	vm_stat_account(mm, vm_flags, file, len >> PAGE_SHIFT);
1149 	if (vm_flags & VM_LOCKED) {
1150 		mm->locked_vm += len >> PAGE_SHIFT;
1151 		make_pages_present(addr, addr + len);
1152 	}
1153 	if (flags & MAP_POPULATE) {
1154 		up_write(&mm->mmap_sem);
1155 		sys_remap_file_pages(addr, len, 0,
1156 					pgoff, flags & MAP_NONBLOCK);
1157 		down_write(&mm->mmap_sem);
1158 	}
1159 	return addr;
1160 
1161 unmap_and_free_vma:
1162 	if (correct_wcount)
1163 		atomic_inc(&inode->i_writecount);
1164 	vma->vm_file = NULL;
1165 	fput(file);
1166 
1167 	/* Undo any partial mapping done by a device driver. */
1168 	unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
1169 	charged = 0;
1170 free_vma:
1171 	kmem_cache_free(vm_area_cachep, vma);
1172 unacct_error:
1173 	if (charged)
1174 		vm_unacct_memory(charged);
1175 	return error;
1176 }
1177 
1178 EXPORT_SYMBOL(do_mmap_pgoff);
1179 
1180 /* Get an address range which is currently unmapped.
1181  * For shmat() with addr=0.
1182  *
1183  * Ugly calling convention alert:
1184  * Return value with the low bits set means error value,
1185  * ie
1186  *	if (ret & ~PAGE_MASK)
1187  *		error = ret;
1188  *
1189  * This function "knows" that -ENOMEM has the bits set.
1190  */
1191 #ifndef HAVE_ARCH_UNMAPPED_AREA
1192 unsigned long
1193 arch_get_unmapped_area(struct file *filp, unsigned long addr,
1194 		unsigned long len, unsigned long pgoff, unsigned long flags)
1195 {
1196 	struct mm_struct *mm = current->mm;
1197 	struct vm_area_struct *vma;
1198 	unsigned long start_addr;
1199 
1200 	if (len > TASK_SIZE)
1201 		return -ENOMEM;
1202 
1203 	if (flags & MAP_FIXED)
1204 		return addr;
1205 
1206 	if (addr) {
1207 		addr = PAGE_ALIGN(addr);
1208 		vma = find_vma(mm, addr);
1209 		if (TASK_SIZE - len >= addr &&
1210 		    (!vma || addr + len <= vma->vm_start))
1211 			return addr;
1212 	}
1213 	if (len > mm->cached_hole_size) {
1214 	        start_addr = addr = mm->free_area_cache;
1215 	} else {
1216 	        start_addr = addr = TASK_UNMAPPED_BASE;
1217 	        mm->cached_hole_size = 0;
1218 	}
1219 
1220 full_search:
1221 	for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
1222 		/* At this point:  (!vma || addr < vma->vm_end). */
1223 		if (TASK_SIZE - len < addr) {
1224 			/*
1225 			 * Start a new search - just in case we missed
1226 			 * some holes.
1227 			 */
1228 			if (start_addr != TASK_UNMAPPED_BASE) {
1229 				addr = TASK_UNMAPPED_BASE;
1230 			        start_addr = addr;
1231 				mm->cached_hole_size = 0;
1232 				goto full_search;
1233 			}
1234 			return -ENOMEM;
1235 		}
1236 		if (!vma || addr + len <= vma->vm_start) {
1237 			/*
1238 			 * Remember the place where we stopped the search:
1239 			 */
1240 			mm->free_area_cache = addr + len;
1241 			return addr;
1242 		}
1243 		if (addr + mm->cached_hole_size < vma->vm_start)
1244 		        mm->cached_hole_size = vma->vm_start - addr;
1245 		addr = vma->vm_end;
1246 	}
1247 }
1248 #endif
1249 
1250 void arch_unmap_area(struct mm_struct *mm, unsigned long addr)
1251 {
1252 	/*
1253 	 * Is this a new hole at the lowest possible address?
1254 	 */
1255 	if (addr >= TASK_UNMAPPED_BASE && addr < mm->free_area_cache) {
1256 		mm->free_area_cache = addr;
1257 		mm->cached_hole_size = ~0UL;
1258 	}
1259 }
1260 
1261 /*
1262  * This mmap-allocator allocates new areas top-down from below the
1263  * stack's low limit (the base):
1264  */
1265 #ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
1266 unsigned long
1267 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
1268 			  const unsigned long len, const unsigned long pgoff,
1269 			  const unsigned long flags)
1270 {
1271 	struct vm_area_struct *vma;
1272 	struct mm_struct *mm = current->mm;
1273 	unsigned long addr = addr0;
1274 
1275 	/* requested length too big for entire address space */
1276 	if (len > TASK_SIZE)
1277 		return -ENOMEM;
1278 
1279 	if (flags & MAP_FIXED)
1280 		return addr;
1281 
1282 	/* requesting a specific address */
1283 	if (addr) {
1284 		addr = PAGE_ALIGN(addr);
1285 		vma = find_vma(mm, addr);
1286 		if (TASK_SIZE - len >= addr &&
1287 				(!vma || addr + len <= vma->vm_start))
1288 			return addr;
1289 	}
1290 
1291 	/* check if free_area_cache is useful for us */
1292 	if (len <= mm->cached_hole_size) {
1293  	        mm->cached_hole_size = 0;
1294  		mm->free_area_cache = mm->mmap_base;
1295  	}
1296 
1297 	/* either no address requested or can't fit in requested address hole */
1298 	addr = mm->free_area_cache;
1299 
1300 	/* make sure it can fit in the remaining address space */
1301 	if (addr > len) {
1302 		vma = find_vma(mm, addr-len);
1303 		if (!vma || addr <= vma->vm_start)
1304 			/* remember the address as a hint for next time */
1305 			return (mm->free_area_cache = addr-len);
1306 	}
1307 
1308 	if (mm->mmap_base < len)
1309 		goto bottomup;
1310 
1311 	addr = mm->mmap_base-len;
1312 
1313 	do {
1314 		/*
1315 		 * Lookup failure means no vma is above this address,
1316 		 * else if new region fits below vma->vm_start,
1317 		 * return with success:
1318 		 */
1319 		vma = find_vma(mm, addr);
1320 		if (!vma || addr+len <= vma->vm_start)
1321 			/* remember the address as a hint for next time */
1322 			return (mm->free_area_cache = addr);
1323 
1324  		/* remember the largest hole we saw so far */
1325  		if (addr + mm->cached_hole_size < vma->vm_start)
1326  		        mm->cached_hole_size = vma->vm_start - addr;
1327 
1328 		/* try just below the current vma->vm_start */
1329 		addr = vma->vm_start-len;
1330 	} while (len < vma->vm_start);
1331 
1332 bottomup:
1333 	/*
1334 	 * A failed mmap() very likely causes application failure,
1335 	 * so fall back to the bottom-up function here. This scenario
1336 	 * can happen with large stack limits and large mmap()
1337 	 * allocations.
1338 	 */
1339 	mm->cached_hole_size = ~0UL;
1340   	mm->free_area_cache = TASK_UNMAPPED_BASE;
1341 	addr = arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
1342 	/*
1343 	 * Restore the topdown base:
1344 	 */
1345 	mm->free_area_cache = mm->mmap_base;
1346 	mm->cached_hole_size = ~0UL;
1347 
1348 	return addr;
1349 }
1350 #endif
1351 
1352 void arch_unmap_area_topdown(struct mm_struct *mm, unsigned long addr)
1353 {
1354 	/*
1355 	 * Is this a new hole at the highest possible address?
1356 	 */
1357 	if (addr > mm->free_area_cache)
1358 		mm->free_area_cache = addr;
1359 
1360 	/* dont allow allocations above current base */
1361 	if (mm->free_area_cache > mm->mmap_base)
1362 		mm->free_area_cache = mm->mmap_base;
1363 }
1364 
1365 unsigned long
1366 get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
1367 		unsigned long pgoff, unsigned long flags)
1368 {
1369 	unsigned long (*get_area)(struct file *, unsigned long,
1370 				  unsigned long, unsigned long, unsigned long);
1371 
1372 	get_area = current->mm->get_unmapped_area;
1373 	if (file && file->f_op && file->f_op->get_unmapped_area)
1374 		get_area = file->f_op->get_unmapped_area;
1375 	addr = get_area(file, addr, len, pgoff, flags);
1376 	if (IS_ERR_VALUE(addr))
1377 		return addr;
1378 
1379 	if (addr > TASK_SIZE - len)
1380 		return -ENOMEM;
1381 	if (addr & ~PAGE_MASK)
1382 		return -EINVAL;
1383 
1384 	return addr;
1385 }
1386 
1387 EXPORT_SYMBOL(get_unmapped_area);
1388 
1389 /* Look up the first VMA which satisfies  addr < vm_end,  NULL if none. */
1390 struct vm_area_struct * find_vma(struct mm_struct * mm, unsigned long addr)
1391 {
1392 	struct vm_area_struct *vma = NULL;
1393 
1394 	if (mm) {
1395 		/* Check the cache first. */
1396 		/* (Cache hit rate is typically around 35%.) */
1397 		vma = mm->mmap_cache;
1398 		if (!(vma && vma->vm_end > addr && vma->vm_start <= addr)) {
1399 			struct rb_node * rb_node;
1400 
1401 			rb_node = mm->mm_rb.rb_node;
1402 			vma = NULL;
1403 
1404 			while (rb_node) {
1405 				struct vm_area_struct * vma_tmp;
1406 
1407 				vma_tmp = rb_entry(rb_node,
1408 						struct vm_area_struct, vm_rb);
1409 
1410 				if (vma_tmp->vm_end > addr) {
1411 					vma = vma_tmp;
1412 					if (vma_tmp->vm_start <= addr)
1413 						break;
1414 					rb_node = rb_node->rb_left;
1415 				} else
1416 					rb_node = rb_node->rb_right;
1417 			}
1418 			if (vma)
1419 				mm->mmap_cache = vma;
1420 		}
1421 	}
1422 	return vma;
1423 }
1424 
1425 EXPORT_SYMBOL(find_vma);
1426 
1427 /* Same as find_vma, but also return a pointer to the previous VMA in *pprev. */
1428 struct vm_area_struct *
1429 find_vma_prev(struct mm_struct *mm, unsigned long addr,
1430 			struct vm_area_struct **pprev)
1431 {
1432 	struct vm_area_struct *vma = NULL, *prev = NULL;
1433 	struct rb_node * rb_node;
1434 	if (!mm)
1435 		goto out;
1436 
1437 	/* Guard against addr being lower than the first VMA */
1438 	vma = mm->mmap;
1439 
1440 	/* Go through the RB tree quickly. */
1441 	rb_node = mm->mm_rb.rb_node;
1442 
1443 	while (rb_node) {
1444 		struct vm_area_struct *vma_tmp;
1445 		vma_tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb);
1446 
1447 		if (addr < vma_tmp->vm_end) {
1448 			rb_node = rb_node->rb_left;
1449 		} else {
1450 			prev = vma_tmp;
1451 			if (!prev->vm_next || (addr < prev->vm_next->vm_end))
1452 				break;
1453 			rb_node = rb_node->rb_right;
1454 		}
1455 	}
1456 
1457 out:
1458 	*pprev = prev;
1459 	return prev ? prev->vm_next : vma;
1460 }
1461 
1462 /*
1463  * Verify that the stack growth is acceptable and
1464  * update accounting. This is shared with both the
1465  * grow-up and grow-down cases.
1466  */
1467 static int acct_stack_growth(struct vm_area_struct * vma, unsigned long size, unsigned long grow)
1468 {
1469 	struct mm_struct *mm = vma->vm_mm;
1470 	struct rlimit *rlim = current->signal->rlim;
1471 	unsigned long new_start;
1472 
1473 	/* address space limit tests */
1474 	if (!may_expand_vm(mm, grow))
1475 		return -ENOMEM;
1476 
1477 	/* Stack limit test */
1478 	if (size > rlim[RLIMIT_STACK].rlim_cur)
1479 		return -ENOMEM;
1480 
1481 	/* mlock limit tests */
1482 	if (vma->vm_flags & VM_LOCKED) {
1483 		unsigned long locked;
1484 		unsigned long limit;
1485 		locked = mm->locked_vm + grow;
1486 		limit = rlim[RLIMIT_MEMLOCK].rlim_cur >> PAGE_SHIFT;
1487 		if (locked > limit && !capable(CAP_IPC_LOCK))
1488 			return -ENOMEM;
1489 	}
1490 
1491 	/* Check to ensure the stack will not grow into a hugetlb-only region */
1492 	new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start :
1493 			vma->vm_end - size;
1494 	if (is_hugepage_only_range(vma->vm_mm, new_start, size))
1495 		return -EFAULT;
1496 
1497 	/*
1498 	 * Overcommit..  This must be the final test, as it will
1499 	 * update security statistics.
1500 	 */
1501 	if (security_vm_enough_memory(grow))
1502 		return -ENOMEM;
1503 
1504 	/* Ok, everything looks good - let it rip */
1505 	mm->total_vm += grow;
1506 	if (vma->vm_flags & VM_LOCKED)
1507 		mm->locked_vm += grow;
1508 	vm_stat_account(mm, vma->vm_flags, vma->vm_file, grow);
1509 	return 0;
1510 }
1511 
1512 #if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
1513 /*
1514  * PA-RISC uses this for its stack; IA64 for its Register Backing Store.
1515  * vma is the last one with address > vma->vm_end.  Have to extend vma.
1516  */
1517 #ifndef CONFIG_IA64
1518 static inline
1519 #endif
1520 int expand_upwards(struct vm_area_struct *vma, unsigned long address)
1521 {
1522 	int error;
1523 
1524 	if (!(vma->vm_flags & VM_GROWSUP))
1525 		return -EFAULT;
1526 
1527 	/*
1528 	 * We must make sure the anon_vma is allocated
1529 	 * so that the anon_vma locking is not a noop.
1530 	 */
1531 	if (unlikely(anon_vma_prepare(vma)))
1532 		return -ENOMEM;
1533 	anon_vma_lock(vma);
1534 
1535 	/*
1536 	 * vma->vm_start/vm_end cannot change under us because the caller
1537 	 * is required to hold the mmap_sem in read mode.  We need the
1538 	 * anon_vma lock to serialize against concurrent expand_stacks.
1539 	 */
1540 	address += 4 + PAGE_SIZE - 1;
1541 	address &= PAGE_MASK;
1542 	error = 0;
1543 
1544 	/* Somebody else might have raced and expanded it already */
1545 	if (address > vma->vm_end) {
1546 		unsigned long size, grow;
1547 
1548 		size = address - vma->vm_start;
1549 		grow = (address - vma->vm_end) >> PAGE_SHIFT;
1550 
1551 		error = acct_stack_growth(vma, size, grow);
1552 		if (!error)
1553 			vma->vm_end = address;
1554 	}
1555 	anon_vma_unlock(vma);
1556 	return error;
1557 }
1558 #endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
1559 
1560 #ifdef CONFIG_STACK_GROWSUP
1561 int expand_stack(struct vm_area_struct *vma, unsigned long address)
1562 {
1563 	return expand_upwards(vma, address);
1564 }
1565 
1566 struct vm_area_struct *
1567 find_extend_vma(struct mm_struct *mm, unsigned long addr)
1568 {
1569 	struct vm_area_struct *vma, *prev;
1570 
1571 	addr &= PAGE_MASK;
1572 	vma = find_vma_prev(mm, addr, &prev);
1573 	if (vma && (vma->vm_start <= addr))
1574 		return vma;
1575 	if (!prev || expand_stack(prev, addr))
1576 		return NULL;
1577 	if (prev->vm_flags & VM_LOCKED) {
1578 		make_pages_present(addr, prev->vm_end);
1579 	}
1580 	return prev;
1581 }
1582 #else
1583 /*
1584  * vma is the first one with address < vma->vm_start.  Have to extend vma.
1585  */
1586 int expand_stack(struct vm_area_struct *vma, unsigned long address)
1587 {
1588 	int error;
1589 
1590 	/*
1591 	 * We must make sure the anon_vma is allocated
1592 	 * so that the anon_vma locking is not a noop.
1593 	 */
1594 	if (unlikely(anon_vma_prepare(vma)))
1595 		return -ENOMEM;
1596 	anon_vma_lock(vma);
1597 
1598 	/*
1599 	 * vma->vm_start/vm_end cannot change under us because the caller
1600 	 * is required to hold the mmap_sem in read mode.  We need the
1601 	 * anon_vma lock to serialize against concurrent expand_stacks.
1602 	 */
1603 	address &= PAGE_MASK;
1604 	error = 0;
1605 
1606 	/* Somebody else might have raced and expanded it already */
1607 	if (address < vma->vm_start) {
1608 		unsigned long size, grow;
1609 
1610 		size = vma->vm_end - address;
1611 		grow = (vma->vm_start - address) >> PAGE_SHIFT;
1612 
1613 		error = acct_stack_growth(vma, size, grow);
1614 		if (!error) {
1615 			vma->vm_start = address;
1616 			vma->vm_pgoff -= grow;
1617 		}
1618 	}
1619 	anon_vma_unlock(vma);
1620 	return error;
1621 }
1622 
1623 struct vm_area_struct *
1624 find_extend_vma(struct mm_struct * mm, unsigned long addr)
1625 {
1626 	struct vm_area_struct * vma;
1627 	unsigned long start;
1628 
1629 	addr &= PAGE_MASK;
1630 	vma = find_vma(mm,addr);
1631 	if (!vma)
1632 		return NULL;
1633 	if (vma->vm_start <= addr)
1634 		return vma;
1635 	if (!(vma->vm_flags & VM_GROWSDOWN))
1636 		return NULL;
1637 	start = vma->vm_start;
1638 	if (expand_stack(vma, addr))
1639 		return NULL;
1640 	if (vma->vm_flags & VM_LOCKED) {
1641 		make_pages_present(addr, start);
1642 	}
1643 	return vma;
1644 }
1645 #endif
1646 
1647 /*
1648  * Ok - we have the memory areas we should free on the vma list,
1649  * so release them, and do the vma updates.
1650  *
1651  * Called with the mm semaphore held.
1652  */
1653 static void remove_vma_list(struct mm_struct *mm, struct vm_area_struct *vma)
1654 {
1655 	/* Update high watermark before we lower total_vm */
1656 	update_hiwater_vm(mm);
1657 	do {
1658 		long nrpages = vma_pages(vma);
1659 
1660 		mm->total_vm -= nrpages;
1661 		if (vma->vm_flags & VM_LOCKED)
1662 			mm->locked_vm -= nrpages;
1663 		vm_stat_account(mm, vma->vm_flags, vma->vm_file, -nrpages);
1664 		vma = remove_vma(vma);
1665 	} while (vma);
1666 	validate_mm(mm);
1667 }
1668 
1669 /*
1670  * Get rid of page table information in the indicated region.
1671  *
1672  * Called with the mm semaphore held.
1673  */
1674 static void unmap_region(struct mm_struct *mm,
1675 		struct vm_area_struct *vma, struct vm_area_struct *prev,
1676 		unsigned long start, unsigned long end)
1677 {
1678 	struct vm_area_struct *next = prev? prev->vm_next: mm->mmap;
1679 	struct mmu_gather *tlb;
1680 	unsigned long nr_accounted = 0;
1681 
1682 	lru_add_drain();
1683 	tlb = tlb_gather_mmu(mm, 0);
1684 	update_hiwater_rss(mm);
1685 	unmap_vmas(&tlb, vma, start, end, &nr_accounted, NULL);
1686 	vm_unacct_memory(nr_accounted);
1687 	free_pgtables(&tlb, vma, prev? prev->vm_end: FIRST_USER_ADDRESS,
1688 				 next? next->vm_start: 0);
1689 	tlb_finish_mmu(tlb, start, end);
1690 }
1691 
1692 /*
1693  * Create a list of vma's touched by the unmap, removing them from the mm's
1694  * vma list as we go..
1695  */
1696 static void
1697 detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
1698 	struct vm_area_struct *prev, unsigned long end)
1699 {
1700 	struct vm_area_struct **insertion_point;
1701 	struct vm_area_struct *tail_vma = NULL;
1702 	unsigned long addr;
1703 
1704 	insertion_point = (prev ? &prev->vm_next : &mm->mmap);
1705 	do {
1706 		rb_erase(&vma->vm_rb, &mm->mm_rb);
1707 		mm->map_count--;
1708 		tail_vma = vma;
1709 		vma = vma->vm_next;
1710 	} while (vma && vma->vm_start < end);
1711 	*insertion_point = vma;
1712 	tail_vma->vm_next = NULL;
1713 	if (mm->unmap_area == arch_unmap_area)
1714 		addr = prev ? prev->vm_end : mm->mmap_base;
1715 	else
1716 		addr = vma ?  vma->vm_start : mm->mmap_base;
1717 	mm->unmap_area(mm, addr);
1718 	mm->mmap_cache = NULL;		/* Kill the cache. */
1719 }
1720 
1721 /*
1722  * Split a vma into two pieces at address 'addr', a new vma is allocated
1723  * either for the first part or the tail.
1724  */
1725 int split_vma(struct mm_struct * mm, struct vm_area_struct * vma,
1726 	      unsigned long addr, int new_below)
1727 {
1728 	struct mempolicy *pol;
1729 	struct vm_area_struct *new;
1730 
1731 	if (is_vm_hugetlb_page(vma) && (addr & ~HPAGE_MASK))
1732 		return -EINVAL;
1733 
1734 	if (mm->map_count >= sysctl_max_map_count)
1735 		return -ENOMEM;
1736 
1737 	new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
1738 	if (!new)
1739 		return -ENOMEM;
1740 
1741 	/* most fields are the same, copy all, and then fixup */
1742 	*new = *vma;
1743 
1744 	if (new_below)
1745 		new->vm_end = addr;
1746 	else {
1747 		new->vm_start = addr;
1748 		new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
1749 	}
1750 
1751 	pol = mpol_copy(vma_policy(vma));
1752 	if (IS_ERR(pol)) {
1753 		kmem_cache_free(vm_area_cachep, new);
1754 		return PTR_ERR(pol);
1755 	}
1756 	vma_set_policy(new, pol);
1757 
1758 	if (new->vm_file)
1759 		get_file(new->vm_file);
1760 
1761 	if (new->vm_ops && new->vm_ops->open)
1762 		new->vm_ops->open(new);
1763 
1764 	if (new_below)
1765 		vma_adjust(vma, addr, vma->vm_end, vma->vm_pgoff +
1766 			((addr - new->vm_start) >> PAGE_SHIFT), new);
1767 	else
1768 		vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new);
1769 
1770 	return 0;
1771 }
1772 
1773 /* Munmap is split into 2 main parts -- this part which finds
1774  * what needs doing, and the areas themselves, which do the
1775  * work.  This now handles partial unmappings.
1776  * Jeremy Fitzhardinge <jeremy@goop.org>
1777  */
1778 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
1779 {
1780 	unsigned long end;
1781 	struct vm_area_struct *vma, *prev, *last;
1782 
1783 	if ((start & ~PAGE_MASK) || start > TASK_SIZE || len > TASK_SIZE-start)
1784 		return -EINVAL;
1785 
1786 	if ((len = PAGE_ALIGN(len)) == 0)
1787 		return -EINVAL;
1788 
1789 	/* Find the first overlapping VMA */
1790 	vma = find_vma_prev(mm, start, &prev);
1791 	if (!vma)
1792 		return 0;
1793 	/* we have  start < vma->vm_end  */
1794 
1795 	/* if it doesn't overlap, we have nothing.. */
1796 	end = start + len;
1797 	if (vma->vm_start >= end)
1798 		return 0;
1799 
1800 	/*
1801 	 * If we need to split any vma, do it now to save pain later.
1802 	 *
1803 	 * Note: mremap's move_vma VM_ACCOUNT handling assumes a partially
1804 	 * unmapped vm_area_struct will remain in use: so lower split_vma
1805 	 * places tmp vma above, and higher split_vma places tmp vma below.
1806 	 */
1807 	if (start > vma->vm_start) {
1808 		int error = split_vma(mm, vma, start, 0);
1809 		if (error)
1810 			return error;
1811 		prev = vma;
1812 	}
1813 
1814 	/* Does it split the last one? */
1815 	last = find_vma(mm, end);
1816 	if (last && end > last->vm_start) {
1817 		int error = split_vma(mm, last, end, 1);
1818 		if (error)
1819 			return error;
1820 	}
1821 	vma = prev? prev->vm_next: mm->mmap;
1822 
1823 	/*
1824 	 * Remove the vma's, and unmap the actual pages
1825 	 */
1826 	detach_vmas_to_be_unmapped(mm, vma, prev, end);
1827 	unmap_region(mm, vma, prev, start, end);
1828 
1829 	/* Fix up all other VM information */
1830 	remove_vma_list(mm, vma);
1831 
1832 	return 0;
1833 }
1834 
1835 EXPORT_SYMBOL(do_munmap);
1836 
1837 asmlinkage long sys_munmap(unsigned long addr, size_t len)
1838 {
1839 	int ret;
1840 	struct mm_struct *mm = current->mm;
1841 
1842 	profile_munmap(addr);
1843 
1844 	down_write(&mm->mmap_sem);
1845 	ret = do_munmap(mm, addr, len);
1846 	up_write(&mm->mmap_sem);
1847 	return ret;
1848 }
1849 
1850 static inline void verify_mm_writelocked(struct mm_struct *mm)
1851 {
1852 #ifdef CONFIG_DEBUG_VM
1853 	if (unlikely(down_read_trylock(&mm->mmap_sem))) {
1854 		WARN_ON(1);
1855 		up_read(&mm->mmap_sem);
1856 	}
1857 #endif
1858 }
1859 
1860 /*
1861  *  this is really a simplified "do_mmap".  it only handles
1862  *  anonymous maps.  eventually we may be able to do some
1863  *  brk-specific accounting here.
1864  */
1865 unsigned long do_brk(unsigned long addr, unsigned long len)
1866 {
1867 	struct mm_struct * mm = current->mm;
1868 	struct vm_area_struct * vma, * prev;
1869 	unsigned long flags;
1870 	struct rb_node ** rb_link, * rb_parent;
1871 	pgoff_t pgoff = addr >> PAGE_SHIFT;
1872 	int error;
1873 
1874 	len = PAGE_ALIGN(len);
1875 	if (!len)
1876 		return addr;
1877 
1878 	if ((addr + len) > TASK_SIZE || (addr + len) < addr)
1879 		return -EINVAL;
1880 
1881 	if (is_hugepage_only_range(mm, addr, len))
1882 		return -EINVAL;
1883 
1884 	flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
1885 
1886 	error = arch_mmap_check(addr, len, flags);
1887 	if (error)
1888 		return error;
1889 
1890 	/*
1891 	 * mlock MCL_FUTURE?
1892 	 */
1893 	if (mm->def_flags & VM_LOCKED) {
1894 		unsigned long locked, lock_limit;
1895 		locked = len >> PAGE_SHIFT;
1896 		locked += mm->locked_vm;
1897 		lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
1898 		lock_limit >>= PAGE_SHIFT;
1899 		if (locked > lock_limit && !capable(CAP_IPC_LOCK))
1900 			return -EAGAIN;
1901 	}
1902 
1903 	/*
1904 	 * mm->mmap_sem is required to protect against another thread
1905 	 * changing the mappings in case we sleep.
1906 	 */
1907 	verify_mm_writelocked(mm);
1908 
1909 	/*
1910 	 * Clear old maps.  this also does some error checking for us
1911 	 */
1912  munmap_back:
1913 	vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
1914 	if (vma && vma->vm_start < addr + len) {
1915 		if (do_munmap(mm, addr, len))
1916 			return -ENOMEM;
1917 		goto munmap_back;
1918 	}
1919 
1920 	/* Check against address space limits *after* clearing old maps... */
1921 	if (!may_expand_vm(mm, len >> PAGE_SHIFT))
1922 		return -ENOMEM;
1923 
1924 	if (mm->map_count > sysctl_max_map_count)
1925 		return -ENOMEM;
1926 
1927 	if (security_vm_enough_memory(len >> PAGE_SHIFT))
1928 		return -ENOMEM;
1929 
1930 	/* Can we just expand an old private anonymous mapping? */
1931 	if (vma_merge(mm, prev, addr, addr + len, flags,
1932 					NULL, NULL, pgoff, NULL))
1933 		goto out;
1934 
1935 	/*
1936 	 * create a vma struct for an anonymous mapping
1937 	 */
1938 	vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
1939 	if (!vma) {
1940 		vm_unacct_memory(len >> PAGE_SHIFT);
1941 		return -ENOMEM;
1942 	}
1943 
1944 	vma->vm_mm = mm;
1945 	vma->vm_start = addr;
1946 	vma->vm_end = addr + len;
1947 	vma->vm_pgoff = pgoff;
1948 	vma->vm_flags = flags;
1949 	vma->vm_page_prot = protection_map[flags &
1950 				(VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)];
1951 	vma_link(mm, vma, prev, rb_link, rb_parent);
1952 out:
1953 	mm->total_vm += len >> PAGE_SHIFT;
1954 	if (flags & VM_LOCKED) {
1955 		mm->locked_vm += len >> PAGE_SHIFT;
1956 		make_pages_present(addr, addr + len);
1957 	}
1958 	return addr;
1959 }
1960 
1961 EXPORT_SYMBOL(do_brk);
1962 
1963 /* Release all mmaps. */
1964 void exit_mmap(struct mm_struct *mm)
1965 {
1966 	struct mmu_gather *tlb;
1967 	struct vm_area_struct *vma = mm->mmap;
1968 	unsigned long nr_accounted = 0;
1969 	unsigned long end;
1970 
1971 	/* mm's last user has gone, and its about to be pulled down */
1972 	arch_exit_mmap(mm);
1973 
1974 	lru_add_drain();
1975 	flush_cache_mm(mm);
1976 	tlb = tlb_gather_mmu(mm, 1);
1977 	/* Don't update_hiwater_rss(mm) here, do_exit already did */
1978 	/* Use -1 here to ensure all VMAs in the mm are unmapped */
1979 	end = unmap_vmas(&tlb, vma, 0, -1, &nr_accounted, NULL);
1980 	vm_unacct_memory(nr_accounted);
1981 	free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, 0);
1982 	tlb_finish_mmu(tlb, 0, end);
1983 
1984 	/*
1985 	 * Walk the list again, actually closing and freeing it,
1986 	 * with preemption enabled, without holding any MM locks.
1987 	 */
1988 	while (vma)
1989 		vma = remove_vma(vma);
1990 
1991 	BUG_ON(mm->nr_ptes > (FIRST_USER_ADDRESS+PMD_SIZE-1)>>PMD_SHIFT);
1992 }
1993 
1994 /* Insert vm structure into process list sorted by address
1995  * and into the inode's i_mmap tree.  If vm_file is non-NULL
1996  * then i_mmap_lock is taken here.
1997  */
1998 int insert_vm_struct(struct mm_struct * mm, struct vm_area_struct * vma)
1999 {
2000 	struct vm_area_struct * __vma, * prev;
2001 	struct rb_node ** rb_link, * rb_parent;
2002 
2003 	/*
2004 	 * The vm_pgoff of a purely anonymous vma should be irrelevant
2005 	 * until its first write fault, when page's anon_vma and index
2006 	 * are set.  But now set the vm_pgoff it will almost certainly
2007 	 * end up with (unless mremap moves it elsewhere before that
2008 	 * first wfault), so /proc/pid/maps tells a consistent story.
2009 	 *
2010 	 * By setting it to reflect the virtual start address of the
2011 	 * vma, merges and splits can happen in a seamless way, just
2012 	 * using the existing file pgoff checks and manipulations.
2013 	 * Similarly in do_mmap_pgoff and in do_brk.
2014 	 */
2015 	if (!vma->vm_file) {
2016 		BUG_ON(vma->anon_vma);
2017 		vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
2018 	}
2019 	__vma = find_vma_prepare(mm,vma->vm_start,&prev,&rb_link,&rb_parent);
2020 	if (__vma && __vma->vm_start < vma->vm_end)
2021 		return -ENOMEM;
2022 	if ((vma->vm_flags & VM_ACCOUNT) &&
2023 	     security_vm_enough_memory(vma_pages(vma)))
2024 		return -ENOMEM;
2025 	vma_link(mm, vma, prev, rb_link, rb_parent);
2026 	return 0;
2027 }
2028 
2029 /*
2030  * Copy the vma structure to a new location in the same mm,
2031  * prior to moving page table entries, to effect an mremap move.
2032  */
2033 struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
2034 	unsigned long addr, unsigned long len, pgoff_t pgoff)
2035 {
2036 	struct vm_area_struct *vma = *vmap;
2037 	unsigned long vma_start = vma->vm_start;
2038 	struct mm_struct *mm = vma->vm_mm;
2039 	struct vm_area_struct *new_vma, *prev;
2040 	struct rb_node **rb_link, *rb_parent;
2041 	struct mempolicy *pol;
2042 
2043 	/*
2044 	 * If anonymous vma has not yet been faulted, update new pgoff
2045 	 * to match new location, to increase its chance of merging.
2046 	 */
2047 	if (!vma->vm_file && !vma->anon_vma)
2048 		pgoff = addr >> PAGE_SHIFT;
2049 
2050 	find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
2051 	new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
2052 			vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));
2053 	if (new_vma) {
2054 		/*
2055 		 * Source vma may have been merged into new_vma
2056 		 */
2057 		if (vma_start >= new_vma->vm_start &&
2058 		    vma_start < new_vma->vm_end)
2059 			*vmap = new_vma;
2060 	} else {
2061 		new_vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
2062 		if (new_vma) {
2063 			*new_vma = *vma;
2064 			pol = mpol_copy(vma_policy(vma));
2065 			if (IS_ERR(pol)) {
2066 				kmem_cache_free(vm_area_cachep, new_vma);
2067 				return NULL;
2068 			}
2069 			vma_set_policy(new_vma, pol);
2070 			new_vma->vm_start = addr;
2071 			new_vma->vm_end = addr + len;
2072 			new_vma->vm_pgoff = pgoff;
2073 			if (new_vma->vm_file)
2074 				get_file(new_vma->vm_file);
2075 			if (new_vma->vm_ops && new_vma->vm_ops->open)
2076 				new_vma->vm_ops->open(new_vma);
2077 			vma_link(mm, new_vma, prev, rb_link, rb_parent);
2078 		}
2079 	}
2080 	return new_vma;
2081 }
2082 
2083 /*
2084  * Return true if the calling process may expand its vm space by the passed
2085  * number of pages
2086  */
2087 int may_expand_vm(struct mm_struct *mm, unsigned long npages)
2088 {
2089 	unsigned long cur = mm->total_vm;	/* pages */
2090 	unsigned long lim;
2091 
2092 	lim = current->signal->rlim[RLIMIT_AS].rlim_cur >> PAGE_SHIFT;
2093 
2094 	if (cur + npages > lim)
2095 		return 0;
2096 	return 1;
2097 }
2098 
2099 
2100 static struct page *special_mapping_nopage(struct vm_area_struct *vma,
2101 					   unsigned long address, int *type)
2102 {
2103 	struct page **pages;
2104 
2105 	BUG_ON(address < vma->vm_start || address >= vma->vm_end);
2106 
2107 	address -= vma->vm_start;
2108 	for (pages = vma->vm_private_data; address > 0 && *pages; ++pages)
2109 		address -= PAGE_SIZE;
2110 
2111 	if (*pages) {
2112 		struct page *page = *pages;
2113 		get_page(page);
2114 		return page;
2115 	}
2116 
2117 	return NOPAGE_SIGBUS;
2118 }
2119 
2120 /*
2121  * Having a close hook prevents vma merging regardless of flags.
2122  */
2123 static void special_mapping_close(struct vm_area_struct *vma)
2124 {
2125 }
2126 
2127 static struct vm_operations_struct special_mapping_vmops = {
2128 	.close = special_mapping_close,
2129 	.nopage	= special_mapping_nopage,
2130 };
2131 
2132 /*
2133  * Called with mm->mmap_sem held for writing.
2134  * Insert a new vma covering the given region, with the given flags.
2135  * Its pages are supplied by the given array of struct page *.
2136  * The array can be shorter than len >> PAGE_SHIFT if it's null-terminated.
2137  * The region past the last page supplied will always produce SIGBUS.
2138  * The array pointer and the pages it points to are assumed to stay alive
2139  * for as long as this mapping might exist.
2140  */
2141 int install_special_mapping(struct mm_struct *mm,
2142 			    unsigned long addr, unsigned long len,
2143 			    unsigned long vm_flags, struct page **pages)
2144 {
2145 	struct vm_area_struct *vma;
2146 
2147 	vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
2148 	if (unlikely(vma == NULL))
2149 		return -ENOMEM;
2150 
2151 	vma->vm_mm = mm;
2152 	vma->vm_start = addr;
2153 	vma->vm_end = addr + len;
2154 
2155 	vma->vm_flags = vm_flags | mm->def_flags;
2156 	vma->vm_page_prot = protection_map[vma->vm_flags & 7];
2157 
2158 	vma->vm_ops = &special_mapping_vmops;
2159 	vma->vm_private_data = pages;
2160 
2161 	if (unlikely(insert_vm_struct(mm, vma))) {
2162 		kmem_cache_free(vm_area_cachep, vma);
2163 		return -ENOMEM;
2164 	}
2165 
2166 	mm->total_vm += len >> PAGE_SHIFT;
2167 
2168 	return 0;
2169 }
2170