xref: /openbmc/linux/mm/mmap.c (revision 22246614)
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/backing-dev.h>
11 #include <linux/mm.h>
12 #include <linux/shm.h>
13 #include <linux/mman.h>
14 #include <linux/pagemap.h>
15 #include <linux/swap.h>
16 #include <linux/syscalls.h>
17 #include <linux/capability.h>
18 #include <linux/init.h>
19 #include <linux/file.h>
20 #include <linux/fs.h>
21 #include <linux/personality.h>
22 #include <linux/security.h>
23 #include <linux/hugetlb.h>
24 #include <linux/profile.h>
25 #include <linux/module.h>
26 #include <linux/mount.h>
27 #include <linux/mempolicy.h>
28 #include <linux/rmap.h>
29 
30 #include <asm/uaccess.h>
31 #include <asm/cacheflush.h>
32 #include <asm/tlb.h>
33 #include <asm/mmu_context.h>
34 
35 #ifndef arch_mmap_check
36 #define arch_mmap_check(addr, len, flags)	(0)
37 #endif
38 
39 #ifndef arch_rebalance_pgtables
40 #define arch_rebalance_pgtables(addr, len)		(addr)
41 #endif
42 
43 static void unmap_region(struct mm_struct *mm,
44 		struct vm_area_struct *vma, struct vm_area_struct *prev,
45 		unsigned long start, unsigned long end);
46 
47 /*
48  * WARNING: the debugging will use recursive algorithms so never enable this
49  * unless you know what you are doing.
50  */
51 #undef DEBUG_MM_RB
52 
53 /* description of effects of mapping type and prot in current implementation.
54  * this is due to the limited x86 page protection hardware.  The expected
55  * behavior is in parens:
56  *
57  * map_type	prot
58  *		PROT_NONE	PROT_READ	PROT_WRITE	PROT_EXEC
59  * MAP_SHARED	r: (no) no	r: (yes) yes	r: (no) yes	r: (no) yes
60  *		w: (no) no	w: (no) no	w: (yes) yes	w: (no) no
61  *		x: (no) no	x: (no) yes	x: (no) yes	x: (yes) yes
62  *
63  * MAP_PRIVATE	r: (no) no	r: (yes) yes	r: (no) yes	r: (no) yes
64  *		w: (no) no	w: (no) no	w: (copy) copy	w: (no) no
65  *		x: (no) no	x: (no) yes	x: (no) yes	x: (yes) yes
66  *
67  */
68 pgprot_t protection_map[16] = {
69 	__P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
70 	__S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
71 };
72 
73 pgprot_t vm_get_page_prot(unsigned long vm_flags)
74 {
75 	return protection_map[vm_flags &
76 				(VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)];
77 }
78 EXPORT_SYMBOL(vm_get_page_prot);
79 
80 int sysctl_overcommit_memory = OVERCOMMIT_GUESS;  /* heuristic overcommit */
81 int sysctl_overcommit_ratio = 50;	/* default is 50% */
82 int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
83 atomic_t vm_committed_space = ATOMIC_INIT(0);
84 
85 /*
86  * Check that a process has enough memory to allocate a new virtual
87  * mapping. 0 means there is enough memory for the allocation to
88  * succeed and -ENOMEM implies there is not.
89  *
90  * We currently support three overcommit policies, which are set via the
91  * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-accounting
92  *
93  * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
94  * Additional code 2002 Jul 20 by Robert Love.
95  *
96  * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
97  *
98  * Note this is a helper function intended to be used by LSMs which
99  * wish to use this logic.
100  */
101 int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
102 {
103 	unsigned long free, allowed;
104 
105 	vm_acct_memory(pages);
106 
107 	/*
108 	 * Sometimes we want to use more memory than we have
109 	 */
110 	if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
111 		return 0;
112 
113 	if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
114 		unsigned long n;
115 
116 		free = global_page_state(NR_FILE_PAGES);
117 		free += nr_swap_pages;
118 
119 		/*
120 		 * Any slabs which are created with the
121 		 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
122 		 * which are reclaimable, under pressure.  The dentry
123 		 * cache and most inode caches should fall into this
124 		 */
125 		free += global_page_state(NR_SLAB_RECLAIMABLE);
126 
127 		/*
128 		 * Leave the last 3% for root
129 		 */
130 		if (!cap_sys_admin)
131 			free -= free / 32;
132 
133 		if (free > pages)
134 			return 0;
135 
136 		/*
137 		 * nr_free_pages() is very expensive on large systems,
138 		 * only call if we're about to fail.
139 		 */
140 		n = nr_free_pages();
141 
142 		/*
143 		 * Leave reserved pages. The pages are not for anonymous pages.
144 		 */
145 		if (n <= totalreserve_pages)
146 			goto error;
147 		else
148 			n -= totalreserve_pages;
149 
150 		/*
151 		 * Leave the last 3% for root
152 		 */
153 		if (!cap_sys_admin)
154 			n -= n / 32;
155 		free += n;
156 
157 		if (free > pages)
158 			return 0;
159 
160 		goto error;
161 	}
162 
163 	allowed = (totalram_pages - hugetlb_total_pages())
164 	       	* sysctl_overcommit_ratio / 100;
165 	/*
166 	 * Leave the last 3% for root
167 	 */
168 	if (!cap_sys_admin)
169 		allowed -= allowed / 32;
170 	allowed += total_swap_pages;
171 
172 	/* Don't let a single process grow too big:
173 	   leave 3% of the size of this process for other processes */
174 	allowed -= mm->total_vm / 32;
175 
176 	/*
177 	 * cast `allowed' as a signed long because vm_committed_space
178 	 * sometimes has a negative value
179 	 */
180 	if (atomic_read(&vm_committed_space) < (long)allowed)
181 		return 0;
182 error:
183 	vm_unacct_memory(pages);
184 
185 	return -ENOMEM;
186 }
187 
188 /*
189  * Requires inode->i_mapping->i_mmap_lock
190  */
191 static void __remove_shared_vm_struct(struct vm_area_struct *vma,
192 		struct file *file, struct address_space *mapping)
193 {
194 	if (vma->vm_flags & VM_DENYWRITE)
195 		atomic_inc(&file->f_path.dentry->d_inode->i_writecount);
196 	if (vma->vm_flags & VM_SHARED)
197 		mapping->i_mmap_writable--;
198 
199 	flush_dcache_mmap_lock(mapping);
200 	if (unlikely(vma->vm_flags & VM_NONLINEAR))
201 		list_del_init(&vma->shared.vm_set.list);
202 	else
203 		vma_prio_tree_remove(vma, &mapping->i_mmap);
204 	flush_dcache_mmap_unlock(mapping);
205 }
206 
207 /*
208  * Unlink a file-based vm structure from its prio_tree, to hide
209  * vma from rmap and vmtruncate before freeing its page tables.
210  */
211 void unlink_file_vma(struct vm_area_struct *vma)
212 {
213 	struct file *file = vma->vm_file;
214 
215 	if (file) {
216 		struct address_space *mapping = file->f_mapping;
217 		spin_lock(&mapping->i_mmap_lock);
218 		__remove_shared_vm_struct(vma, file, mapping);
219 		spin_unlock(&mapping->i_mmap_lock);
220 	}
221 }
222 
223 /*
224  * Close a vm structure and free it, returning the next.
225  */
226 static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
227 {
228 	struct vm_area_struct *next = vma->vm_next;
229 
230 	might_sleep();
231 	if (vma->vm_ops && vma->vm_ops->close)
232 		vma->vm_ops->close(vma);
233 	if (vma->vm_file) {
234 		fput(vma->vm_file);
235 		if (vma->vm_flags & VM_EXECUTABLE)
236 			removed_exe_file_vma(vma->vm_mm);
237 	}
238 	mpol_put(vma_policy(vma));
239 	kmem_cache_free(vm_area_cachep, vma);
240 	return next;
241 }
242 
243 asmlinkage unsigned long sys_brk(unsigned long brk)
244 {
245 	unsigned long rlim, retval;
246 	unsigned long newbrk, oldbrk;
247 	struct mm_struct *mm = current->mm;
248 
249 	down_write(&mm->mmap_sem);
250 
251 	if (brk < mm->start_brk)
252 		goto out;
253 
254 	/*
255 	 * Check against rlimit here. If this check is done later after the test
256 	 * of oldbrk with newbrk then it can escape the test and let the data
257 	 * segment grow beyond its set limit the in case where the limit is
258 	 * not page aligned -Ram Gupta
259 	 */
260 	rlim = current->signal->rlim[RLIMIT_DATA].rlim_cur;
261 	if (rlim < RLIM_INFINITY && (brk - mm->start_brk) +
262 			(mm->end_data - mm->start_data) > rlim)
263 		goto out;
264 
265 	newbrk = PAGE_ALIGN(brk);
266 	oldbrk = PAGE_ALIGN(mm->brk);
267 	if (oldbrk == newbrk)
268 		goto set_brk;
269 
270 	/* Always allow shrinking brk. */
271 	if (brk <= mm->brk) {
272 		if (!do_munmap(mm, newbrk, oldbrk-newbrk))
273 			goto set_brk;
274 		goto out;
275 	}
276 
277 	/* Check against existing mmap mappings. */
278 	if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE))
279 		goto out;
280 
281 	/* Ok, looks good - let it rip. */
282 	if (do_brk(oldbrk, newbrk-oldbrk) != oldbrk)
283 		goto out;
284 set_brk:
285 	mm->brk = brk;
286 out:
287 	retval = mm->brk;
288 	up_write(&mm->mmap_sem);
289 	return retval;
290 }
291 
292 #ifdef DEBUG_MM_RB
293 static int browse_rb(struct rb_root *root)
294 {
295 	int i = 0, j;
296 	struct rb_node *nd, *pn = NULL;
297 	unsigned long prev = 0, pend = 0;
298 
299 	for (nd = rb_first(root); nd; nd = rb_next(nd)) {
300 		struct vm_area_struct *vma;
301 		vma = rb_entry(nd, struct vm_area_struct, vm_rb);
302 		if (vma->vm_start < prev)
303 			printk("vm_start %lx prev %lx\n", vma->vm_start, prev), i = -1;
304 		if (vma->vm_start < pend)
305 			printk("vm_start %lx pend %lx\n", vma->vm_start, pend);
306 		if (vma->vm_start > vma->vm_end)
307 			printk("vm_end %lx < vm_start %lx\n", vma->vm_end, vma->vm_start);
308 		i++;
309 		pn = nd;
310 		prev = vma->vm_start;
311 		pend = vma->vm_end;
312 	}
313 	j = 0;
314 	for (nd = pn; nd; nd = rb_prev(nd)) {
315 		j++;
316 	}
317 	if (i != j)
318 		printk("backwards %d, forwards %d\n", j, i), i = 0;
319 	return i;
320 }
321 
322 void validate_mm(struct mm_struct *mm)
323 {
324 	int bug = 0;
325 	int i = 0;
326 	struct vm_area_struct *tmp = mm->mmap;
327 	while (tmp) {
328 		tmp = tmp->vm_next;
329 		i++;
330 	}
331 	if (i != mm->map_count)
332 		printk("map_count %d vm_next %d\n", mm->map_count, i), bug = 1;
333 	i = browse_rb(&mm->mm_rb);
334 	if (i != mm->map_count)
335 		printk("map_count %d rb %d\n", mm->map_count, i), bug = 1;
336 	BUG_ON(bug);
337 }
338 #else
339 #define validate_mm(mm) do { } while (0)
340 #endif
341 
342 static struct vm_area_struct *
343 find_vma_prepare(struct mm_struct *mm, unsigned long addr,
344 		struct vm_area_struct **pprev, struct rb_node ***rb_link,
345 		struct rb_node ** rb_parent)
346 {
347 	struct vm_area_struct * vma;
348 	struct rb_node ** __rb_link, * __rb_parent, * rb_prev;
349 
350 	__rb_link = &mm->mm_rb.rb_node;
351 	rb_prev = __rb_parent = NULL;
352 	vma = NULL;
353 
354 	while (*__rb_link) {
355 		struct vm_area_struct *vma_tmp;
356 
357 		__rb_parent = *__rb_link;
358 		vma_tmp = rb_entry(__rb_parent, struct vm_area_struct, vm_rb);
359 
360 		if (vma_tmp->vm_end > addr) {
361 			vma = vma_tmp;
362 			if (vma_tmp->vm_start <= addr)
363 				return vma;
364 			__rb_link = &__rb_parent->rb_left;
365 		} else {
366 			rb_prev = __rb_parent;
367 			__rb_link = &__rb_parent->rb_right;
368 		}
369 	}
370 
371 	*pprev = NULL;
372 	if (rb_prev)
373 		*pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
374 	*rb_link = __rb_link;
375 	*rb_parent = __rb_parent;
376 	return vma;
377 }
378 
379 static inline void
380 __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
381 		struct vm_area_struct *prev, struct rb_node *rb_parent)
382 {
383 	if (prev) {
384 		vma->vm_next = prev->vm_next;
385 		prev->vm_next = vma;
386 	} else {
387 		mm->mmap = vma;
388 		if (rb_parent)
389 			vma->vm_next = rb_entry(rb_parent,
390 					struct vm_area_struct, vm_rb);
391 		else
392 			vma->vm_next = NULL;
393 	}
394 }
395 
396 void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
397 		struct rb_node **rb_link, struct rb_node *rb_parent)
398 {
399 	rb_link_node(&vma->vm_rb, rb_parent, rb_link);
400 	rb_insert_color(&vma->vm_rb, &mm->mm_rb);
401 }
402 
403 static inline void __vma_link_file(struct vm_area_struct *vma)
404 {
405 	struct file * file;
406 
407 	file = vma->vm_file;
408 	if (file) {
409 		struct address_space *mapping = file->f_mapping;
410 
411 		if (vma->vm_flags & VM_DENYWRITE)
412 			atomic_dec(&file->f_path.dentry->d_inode->i_writecount);
413 		if (vma->vm_flags & VM_SHARED)
414 			mapping->i_mmap_writable++;
415 
416 		flush_dcache_mmap_lock(mapping);
417 		if (unlikely(vma->vm_flags & VM_NONLINEAR))
418 			vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
419 		else
420 			vma_prio_tree_insert(vma, &mapping->i_mmap);
421 		flush_dcache_mmap_unlock(mapping);
422 	}
423 }
424 
425 static void
426 __vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
427 	struct vm_area_struct *prev, struct rb_node **rb_link,
428 	struct rb_node *rb_parent)
429 {
430 	__vma_link_list(mm, vma, prev, rb_parent);
431 	__vma_link_rb(mm, vma, rb_link, rb_parent);
432 	__anon_vma_link(vma);
433 }
434 
435 static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
436 			struct vm_area_struct *prev, struct rb_node **rb_link,
437 			struct rb_node *rb_parent)
438 {
439 	struct address_space *mapping = NULL;
440 
441 	if (vma->vm_file)
442 		mapping = vma->vm_file->f_mapping;
443 
444 	if (mapping) {
445 		spin_lock(&mapping->i_mmap_lock);
446 		vma->vm_truncate_count = mapping->truncate_count;
447 	}
448 	anon_vma_lock(vma);
449 
450 	__vma_link(mm, vma, prev, rb_link, rb_parent);
451 	__vma_link_file(vma);
452 
453 	anon_vma_unlock(vma);
454 	if (mapping)
455 		spin_unlock(&mapping->i_mmap_lock);
456 
457 	mm->map_count++;
458 	validate_mm(mm);
459 }
460 
461 /*
462  * Helper for vma_adjust in the split_vma insert case:
463  * insert vm structure into list and rbtree and anon_vma,
464  * but it has already been inserted into prio_tree earlier.
465  */
466 static void
467 __insert_vm_struct(struct mm_struct * mm, struct vm_area_struct * vma)
468 {
469 	struct vm_area_struct * __vma, * prev;
470 	struct rb_node ** rb_link, * rb_parent;
471 
472 	__vma = find_vma_prepare(mm, vma->vm_start,&prev, &rb_link, &rb_parent);
473 	BUG_ON(__vma && __vma->vm_start < vma->vm_end);
474 	__vma_link(mm, vma, prev, rb_link, rb_parent);
475 	mm->map_count++;
476 }
477 
478 static inline void
479 __vma_unlink(struct mm_struct *mm, struct vm_area_struct *vma,
480 		struct vm_area_struct *prev)
481 {
482 	prev->vm_next = vma->vm_next;
483 	rb_erase(&vma->vm_rb, &mm->mm_rb);
484 	if (mm->mmap_cache == vma)
485 		mm->mmap_cache = prev;
486 }
487 
488 /*
489  * We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that
490  * is already present in an i_mmap tree without adjusting the tree.
491  * The following helper function should be used when such adjustments
492  * are necessary.  The "insert" vma (if any) is to be inserted
493  * before we drop the necessary locks.
494  */
495 void vma_adjust(struct vm_area_struct *vma, unsigned long start,
496 	unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert)
497 {
498 	struct mm_struct *mm = vma->vm_mm;
499 	struct vm_area_struct *next = vma->vm_next;
500 	struct vm_area_struct *importer = NULL;
501 	struct address_space *mapping = NULL;
502 	struct prio_tree_root *root = NULL;
503 	struct file *file = vma->vm_file;
504 	struct anon_vma *anon_vma = NULL;
505 	long adjust_next = 0;
506 	int remove_next = 0;
507 
508 	if (next && !insert) {
509 		if (end >= next->vm_end) {
510 			/*
511 			 * vma expands, overlapping all the next, and
512 			 * perhaps the one after too (mprotect case 6).
513 			 */
514 again:			remove_next = 1 + (end > next->vm_end);
515 			end = next->vm_end;
516 			anon_vma = next->anon_vma;
517 			importer = vma;
518 		} else if (end > next->vm_start) {
519 			/*
520 			 * vma expands, overlapping part of the next:
521 			 * mprotect case 5 shifting the boundary up.
522 			 */
523 			adjust_next = (end - next->vm_start) >> PAGE_SHIFT;
524 			anon_vma = next->anon_vma;
525 			importer = vma;
526 		} else if (end < vma->vm_end) {
527 			/*
528 			 * vma shrinks, and !insert tells it's not
529 			 * split_vma inserting another: so it must be
530 			 * mprotect case 4 shifting the boundary down.
531 			 */
532 			adjust_next = - ((vma->vm_end - end) >> PAGE_SHIFT);
533 			anon_vma = next->anon_vma;
534 			importer = next;
535 		}
536 	}
537 
538 	if (file) {
539 		mapping = file->f_mapping;
540 		if (!(vma->vm_flags & VM_NONLINEAR))
541 			root = &mapping->i_mmap;
542 		spin_lock(&mapping->i_mmap_lock);
543 		if (importer &&
544 		    vma->vm_truncate_count != next->vm_truncate_count) {
545 			/*
546 			 * unmap_mapping_range might be in progress:
547 			 * ensure that the expanding vma is rescanned.
548 			 */
549 			importer->vm_truncate_count = 0;
550 		}
551 		if (insert) {
552 			insert->vm_truncate_count = vma->vm_truncate_count;
553 			/*
554 			 * Put into prio_tree now, so instantiated pages
555 			 * are visible to arm/parisc __flush_dcache_page
556 			 * throughout; but we cannot insert into address
557 			 * space until vma start or end is updated.
558 			 */
559 			__vma_link_file(insert);
560 		}
561 	}
562 
563 	/*
564 	 * When changing only vma->vm_end, we don't really need
565 	 * anon_vma lock: but is that case worth optimizing out?
566 	 */
567 	if (vma->anon_vma)
568 		anon_vma = vma->anon_vma;
569 	if (anon_vma) {
570 		spin_lock(&anon_vma->lock);
571 		/*
572 		 * Easily overlooked: when mprotect shifts the boundary,
573 		 * make sure the expanding vma has anon_vma set if the
574 		 * shrinking vma had, to cover any anon pages imported.
575 		 */
576 		if (importer && !importer->anon_vma) {
577 			importer->anon_vma = anon_vma;
578 			__anon_vma_link(importer);
579 		}
580 	}
581 
582 	if (root) {
583 		flush_dcache_mmap_lock(mapping);
584 		vma_prio_tree_remove(vma, root);
585 		if (adjust_next)
586 			vma_prio_tree_remove(next, root);
587 	}
588 
589 	vma->vm_start = start;
590 	vma->vm_end = end;
591 	vma->vm_pgoff = pgoff;
592 	if (adjust_next) {
593 		next->vm_start += adjust_next << PAGE_SHIFT;
594 		next->vm_pgoff += adjust_next;
595 	}
596 
597 	if (root) {
598 		if (adjust_next)
599 			vma_prio_tree_insert(next, root);
600 		vma_prio_tree_insert(vma, root);
601 		flush_dcache_mmap_unlock(mapping);
602 	}
603 
604 	if (remove_next) {
605 		/*
606 		 * vma_merge has merged next into vma, and needs
607 		 * us to remove next before dropping the locks.
608 		 */
609 		__vma_unlink(mm, next, vma);
610 		if (file)
611 			__remove_shared_vm_struct(next, file, mapping);
612 		if (next->anon_vma)
613 			__anon_vma_merge(vma, next);
614 	} else if (insert) {
615 		/*
616 		 * split_vma has split insert from vma, and needs
617 		 * us to insert it before dropping the locks
618 		 * (it may either follow vma or precede it).
619 		 */
620 		__insert_vm_struct(mm, insert);
621 	}
622 
623 	if (anon_vma)
624 		spin_unlock(&anon_vma->lock);
625 	if (mapping)
626 		spin_unlock(&mapping->i_mmap_lock);
627 
628 	if (remove_next) {
629 		if (file) {
630 			fput(file);
631 			if (next->vm_flags & VM_EXECUTABLE)
632 				removed_exe_file_vma(mm);
633 		}
634 		mm->map_count--;
635 		mpol_put(vma_policy(next));
636 		kmem_cache_free(vm_area_cachep, next);
637 		/*
638 		 * In mprotect's case 6 (see comments on vma_merge),
639 		 * we must remove another next too. It would clutter
640 		 * up the code too much to do both in one go.
641 		 */
642 		if (remove_next == 2) {
643 			next = vma->vm_next;
644 			goto again;
645 		}
646 	}
647 
648 	validate_mm(mm);
649 }
650 
651 /*
652  * If the vma has a ->close operation then the driver probably needs to release
653  * per-vma resources, so we don't attempt to merge those.
654  */
655 #define VM_SPECIAL (VM_IO | VM_DONTEXPAND | VM_RESERVED | VM_PFNMAP)
656 
657 static inline int is_mergeable_vma(struct vm_area_struct *vma,
658 			struct file *file, unsigned long vm_flags)
659 {
660 	if (vma->vm_flags != vm_flags)
661 		return 0;
662 	if (vma->vm_file != file)
663 		return 0;
664 	if (vma->vm_ops && vma->vm_ops->close)
665 		return 0;
666 	return 1;
667 }
668 
669 static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1,
670 					struct anon_vma *anon_vma2)
671 {
672 	return !anon_vma1 || !anon_vma2 || (anon_vma1 == anon_vma2);
673 }
674 
675 /*
676  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
677  * in front of (at a lower virtual address and file offset than) the vma.
678  *
679  * We cannot merge two vmas if they have differently assigned (non-NULL)
680  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
681  *
682  * We don't check here for the merged mmap wrapping around the end of pagecache
683  * indices (16TB on ia32) because do_mmap_pgoff() does not permit mmap's which
684  * wrap, nor mmaps which cover the final page at index -1UL.
685  */
686 static int
687 can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags,
688 	struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff)
689 {
690 	if (is_mergeable_vma(vma, file, vm_flags) &&
691 	    is_mergeable_anon_vma(anon_vma, vma->anon_vma)) {
692 		if (vma->vm_pgoff == vm_pgoff)
693 			return 1;
694 	}
695 	return 0;
696 }
697 
698 /*
699  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
700  * beyond (at a higher virtual address and file offset than) the vma.
701  *
702  * We cannot merge two vmas if they have differently assigned (non-NULL)
703  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
704  */
705 static int
706 can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
707 	struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff)
708 {
709 	if (is_mergeable_vma(vma, file, vm_flags) &&
710 	    is_mergeable_anon_vma(anon_vma, vma->anon_vma)) {
711 		pgoff_t vm_pglen;
712 		vm_pglen = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
713 		if (vma->vm_pgoff + vm_pglen == vm_pgoff)
714 			return 1;
715 	}
716 	return 0;
717 }
718 
719 /*
720  * Given a mapping request (addr,end,vm_flags,file,pgoff), figure out
721  * whether that can be merged with its predecessor or its successor.
722  * Or both (it neatly fills a hole).
723  *
724  * In most cases - when called for mmap, brk or mremap - [addr,end) is
725  * certain not to be mapped by the time vma_merge is called; but when
726  * called for mprotect, it is certain to be already mapped (either at
727  * an offset within prev, or at the start of next), and the flags of
728  * this area are about to be changed to vm_flags - and the no-change
729  * case has already been eliminated.
730  *
731  * The following mprotect cases have to be considered, where AAAA is
732  * the area passed down from mprotect_fixup, never extending beyond one
733  * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
734  *
735  *     AAAA             AAAA                AAAA          AAAA
736  *    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPNNNNXXXX
737  *    cannot merge    might become    might become    might become
738  *                    PPNNNNNNNNNN    PPPPPPPPPPNN    PPPPPPPPPPPP 6 or
739  *    mmap, brk or    case 4 below    case 5 below    PPPPPPPPXXXX 7 or
740  *    mremap move:                                    PPPPNNNNNNNN 8
741  *        AAAA
742  *    PPPP    NNNN    PPPPPPPPPPPP    PPPPPPPPNNNN    PPPPNNNNNNNN
743  *    might become    case 1 below    case 2 below    case 3 below
744  *
745  * Odd one out? Case 8, because it extends NNNN but needs flags of XXXX:
746  * mprotect_fixup updates vm_flags & vm_page_prot on successful return.
747  */
748 struct vm_area_struct *vma_merge(struct mm_struct *mm,
749 			struct vm_area_struct *prev, unsigned long addr,
750 			unsigned long end, unsigned long vm_flags,
751 		     	struct anon_vma *anon_vma, struct file *file,
752 			pgoff_t pgoff, struct mempolicy *policy)
753 {
754 	pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
755 	struct vm_area_struct *area, *next;
756 
757 	/*
758 	 * We later require that vma->vm_flags == vm_flags,
759 	 * so this tests vma->vm_flags & VM_SPECIAL, too.
760 	 */
761 	if (vm_flags & VM_SPECIAL)
762 		return NULL;
763 
764 	if (prev)
765 		next = prev->vm_next;
766 	else
767 		next = mm->mmap;
768 	area = next;
769 	if (next && next->vm_end == end)		/* cases 6, 7, 8 */
770 		next = next->vm_next;
771 
772 	/*
773 	 * Can it merge with the predecessor?
774 	 */
775 	if (prev && prev->vm_end == addr &&
776   			mpol_equal(vma_policy(prev), policy) &&
777 			can_vma_merge_after(prev, vm_flags,
778 						anon_vma, file, pgoff)) {
779 		/*
780 		 * OK, it can.  Can we now merge in the successor as well?
781 		 */
782 		if (next && end == next->vm_start &&
783 				mpol_equal(policy, vma_policy(next)) &&
784 				can_vma_merge_before(next, vm_flags,
785 					anon_vma, file, pgoff+pglen) &&
786 				is_mergeable_anon_vma(prev->anon_vma,
787 						      next->anon_vma)) {
788 							/* cases 1, 6 */
789 			vma_adjust(prev, prev->vm_start,
790 				next->vm_end, prev->vm_pgoff, NULL);
791 		} else					/* cases 2, 5, 7 */
792 			vma_adjust(prev, prev->vm_start,
793 				end, prev->vm_pgoff, NULL);
794 		return prev;
795 	}
796 
797 	/*
798 	 * Can this new request be merged in front of next?
799 	 */
800 	if (next && end == next->vm_start &&
801  			mpol_equal(policy, vma_policy(next)) &&
802 			can_vma_merge_before(next, vm_flags,
803 					anon_vma, file, pgoff+pglen)) {
804 		if (prev && addr < prev->vm_end)	/* case 4 */
805 			vma_adjust(prev, prev->vm_start,
806 				addr, prev->vm_pgoff, NULL);
807 		else					/* cases 3, 8 */
808 			vma_adjust(area, addr, next->vm_end,
809 				next->vm_pgoff - pglen, NULL);
810 		return area;
811 	}
812 
813 	return NULL;
814 }
815 
816 /*
817  * find_mergeable_anon_vma is used by anon_vma_prepare, to check
818  * neighbouring vmas for a suitable anon_vma, before it goes off
819  * to allocate a new anon_vma.  It checks because a repetitive
820  * sequence of mprotects and faults may otherwise lead to distinct
821  * anon_vmas being allocated, preventing vma merge in subsequent
822  * mprotect.
823  */
824 struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
825 {
826 	struct vm_area_struct *near;
827 	unsigned long vm_flags;
828 
829 	near = vma->vm_next;
830 	if (!near)
831 		goto try_prev;
832 
833 	/*
834 	 * Since only mprotect tries to remerge vmas, match flags
835 	 * which might be mprotected into each other later on.
836 	 * Neither mlock nor madvise tries to remerge at present,
837 	 * so leave their flags as obstructing a merge.
838 	 */
839 	vm_flags = vma->vm_flags & ~(VM_READ|VM_WRITE|VM_EXEC);
840 	vm_flags |= near->vm_flags & (VM_READ|VM_WRITE|VM_EXEC);
841 
842 	if (near->anon_vma && vma->vm_end == near->vm_start &&
843  			mpol_equal(vma_policy(vma), vma_policy(near)) &&
844 			can_vma_merge_before(near, vm_flags,
845 				NULL, vma->vm_file, vma->vm_pgoff +
846 				((vma->vm_end - vma->vm_start) >> PAGE_SHIFT)))
847 		return near->anon_vma;
848 try_prev:
849 	/*
850 	 * It is potentially slow to have to call find_vma_prev here.
851 	 * But it's only on the first write fault on the vma, not
852 	 * every time, and we could devise a way to avoid it later
853 	 * (e.g. stash info in next's anon_vma_node when assigning
854 	 * an anon_vma, or when trying vma_merge).  Another time.
855 	 */
856 	BUG_ON(find_vma_prev(vma->vm_mm, vma->vm_start, &near) != vma);
857 	if (!near)
858 		goto none;
859 
860 	vm_flags = vma->vm_flags & ~(VM_READ|VM_WRITE|VM_EXEC);
861 	vm_flags |= near->vm_flags & (VM_READ|VM_WRITE|VM_EXEC);
862 
863 	if (near->anon_vma && near->vm_end == vma->vm_start &&
864   			mpol_equal(vma_policy(near), vma_policy(vma)) &&
865 			can_vma_merge_after(near, vm_flags,
866 				NULL, vma->vm_file, vma->vm_pgoff))
867 		return near->anon_vma;
868 none:
869 	/*
870 	 * There's no absolute need to look only at touching neighbours:
871 	 * we could search further afield for "compatible" anon_vmas.
872 	 * But it would probably just be a waste of time searching,
873 	 * or lead to too many vmas hanging off the same anon_vma.
874 	 * We're trying to allow mprotect remerging later on,
875 	 * not trying to minimize memory used for anon_vmas.
876 	 */
877 	return NULL;
878 }
879 
880 #ifdef CONFIG_PROC_FS
881 void vm_stat_account(struct mm_struct *mm, unsigned long flags,
882 						struct file *file, long pages)
883 {
884 	const unsigned long stack_flags
885 		= VM_STACK_FLAGS & (VM_GROWSUP|VM_GROWSDOWN);
886 
887 	if (file) {
888 		mm->shared_vm += pages;
889 		if ((flags & (VM_EXEC|VM_WRITE)) == VM_EXEC)
890 			mm->exec_vm += pages;
891 	} else if (flags & stack_flags)
892 		mm->stack_vm += pages;
893 	if (flags & (VM_RESERVED|VM_IO))
894 		mm->reserved_vm += pages;
895 }
896 #endif /* CONFIG_PROC_FS */
897 
898 /*
899  * The caller must hold down_write(current->mm->mmap_sem).
900  */
901 
902 unsigned long do_mmap_pgoff(struct file * file, unsigned long addr,
903 			unsigned long len, unsigned long prot,
904 			unsigned long flags, unsigned long pgoff)
905 {
906 	struct mm_struct * mm = current->mm;
907 	struct inode *inode;
908 	unsigned int vm_flags;
909 	int error;
910 	int accountable = 1;
911 	unsigned long reqprot = prot;
912 
913 	/*
914 	 * Does the application expect PROT_READ to imply PROT_EXEC?
915 	 *
916 	 * (the exception is when the underlying filesystem is noexec
917 	 *  mounted, in which case we dont add PROT_EXEC.)
918 	 */
919 	if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
920 		if (!(file && (file->f_path.mnt->mnt_flags & MNT_NOEXEC)))
921 			prot |= PROT_EXEC;
922 
923 	if (!len)
924 		return -EINVAL;
925 
926 	if (!(flags & MAP_FIXED))
927 		addr = round_hint_to_min(addr);
928 
929 	error = arch_mmap_check(addr, len, flags);
930 	if (error)
931 		return error;
932 
933 	/* Careful about overflows.. */
934 	len = PAGE_ALIGN(len);
935 	if (!len || len > TASK_SIZE)
936 		return -ENOMEM;
937 
938 	/* offset overflow? */
939 	if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
940                return -EOVERFLOW;
941 
942 	/* Too many mappings? */
943 	if (mm->map_count > sysctl_max_map_count)
944 		return -ENOMEM;
945 
946 	/* Obtain the address to map to. we verify (or select) it and ensure
947 	 * that it represents a valid section of the address space.
948 	 */
949 	addr = get_unmapped_area(file, addr, len, pgoff, flags);
950 	if (addr & ~PAGE_MASK)
951 		return addr;
952 
953 	/* Do simple checking here so the lower-level routines won't have
954 	 * to. we assume access permissions have been handled by the open
955 	 * of the memory object, so we don't do any here.
956 	 */
957 	vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags) |
958 			mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
959 
960 	if (flags & MAP_LOCKED) {
961 		if (!can_do_mlock())
962 			return -EPERM;
963 		vm_flags |= VM_LOCKED;
964 	}
965 	/* mlock MCL_FUTURE? */
966 	if (vm_flags & VM_LOCKED) {
967 		unsigned long locked, lock_limit;
968 		locked = len >> PAGE_SHIFT;
969 		locked += mm->locked_vm;
970 		lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
971 		lock_limit >>= PAGE_SHIFT;
972 		if (locked > lock_limit && !capable(CAP_IPC_LOCK))
973 			return -EAGAIN;
974 	}
975 
976 	inode = file ? file->f_path.dentry->d_inode : NULL;
977 
978 	if (file) {
979 		switch (flags & MAP_TYPE) {
980 		case MAP_SHARED:
981 			if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE))
982 				return -EACCES;
983 
984 			/*
985 			 * Make sure we don't allow writing to an append-only
986 			 * file..
987 			 */
988 			if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE))
989 				return -EACCES;
990 
991 			/*
992 			 * Make sure there are no mandatory locks on the file.
993 			 */
994 			if (locks_verify_locked(inode))
995 				return -EAGAIN;
996 
997 			vm_flags |= VM_SHARED | VM_MAYSHARE;
998 			if (!(file->f_mode & FMODE_WRITE))
999 				vm_flags &= ~(VM_MAYWRITE | VM_SHARED);
1000 
1001 			/* fall through */
1002 		case MAP_PRIVATE:
1003 			if (!(file->f_mode & FMODE_READ))
1004 				return -EACCES;
1005 			if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) {
1006 				if (vm_flags & VM_EXEC)
1007 					return -EPERM;
1008 				vm_flags &= ~VM_MAYEXEC;
1009 			}
1010 			if (is_file_hugepages(file))
1011 				accountable = 0;
1012 
1013 			if (!file->f_op || !file->f_op->mmap)
1014 				return -ENODEV;
1015 			break;
1016 
1017 		default:
1018 			return -EINVAL;
1019 		}
1020 	} else {
1021 		switch (flags & MAP_TYPE) {
1022 		case MAP_SHARED:
1023 			vm_flags |= VM_SHARED | VM_MAYSHARE;
1024 			break;
1025 		case MAP_PRIVATE:
1026 			/*
1027 			 * Set pgoff according to addr for anon_vma.
1028 			 */
1029 			pgoff = addr >> PAGE_SHIFT;
1030 			break;
1031 		default:
1032 			return -EINVAL;
1033 		}
1034 	}
1035 
1036 	error = security_file_mmap(file, reqprot, prot, flags, addr, 0);
1037 	if (error)
1038 		return error;
1039 
1040 	return mmap_region(file, addr, len, flags, vm_flags, pgoff,
1041 			   accountable);
1042 }
1043 EXPORT_SYMBOL(do_mmap_pgoff);
1044 
1045 /*
1046  * Some shared mappigns will want the pages marked read-only
1047  * to track write events. If so, we'll downgrade vm_page_prot
1048  * to the private version (using protection_map[] without the
1049  * VM_SHARED bit).
1050  */
1051 int vma_wants_writenotify(struct vm_area_struct *vma)
1052 {
1053 	unsigned int vm_flags = vma->vm_flags;
1054 
1055 	/* If it was private or non-writable, the write bit is already clear */
1056 	if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED)))
1057 		return 0;
1058 
1059 	/* The backer wishes to know when pages are first written to? */
1060 	if (vma->vm_ops && vma->vm_ops->page_mkwrite)
1061 		return 1;
1062 
1063 	/* The open routine did something to the protections already? */
1064 	if (pgprot_val(vma->vm_page_prot) !=
1065 	    pgprot_val(vm_get_page_prot(vm_flags)))
1066 		return 0;
1067 
1068 	/* Specialty mapping? */
1069 	if (vm_flags & (VM_PFNMAP|VM_INSERTPAGE))
1070 		return 0;
1071 
1072 	/* Can the mapping track the dirty pages? */
1073 	return vma->vm_file && vma->vm_file->f_mapping &&
1074 		mapping_cap_account_dirty(vma->vm_file->f_mapping);
1075 }
1076 
1077 unsigned long mmap_region(struct file *file, unsigned long addr,
1078 			  unsigned long len, unsigned long flags,
1079 			  unsigned int vm_flags, unsigned long pgoff,
1080 			  int accountable)
1081 {
1082 	struct mm_struct *mm = current->mm;
1083 	struct vm_area_struct *vma, *prev;
1084 	int correct_wcount = 0;
1085 	int error;
1086 	struct rb_node **rb_link, *rb_parent;
1087 	unsigned long charged = 0;
1088 	struct inode *inode =  file ? file->f_path.dentry->d_inode : NULL;
1089 
1090 	/* Clear old maps */
1091 	error = -ENOMEM;
1092 munmap_back:
1093 	vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
1094 	if (vma && vma->vm_start < addr + len) {
1095 		if (do_munmap(mm, addr, len))
1096 			return -ENOMEM;
1097 		goto munmap_back;
1098 	}
1099 
1100 	/* Check against address space limit. */
1101 	if (!may_expand_vm(mm, len >> PAGE_SHIFT))
1102 		return -ENOMEM;
1103 
1104 	if (accountable && (!(flags & MAP_NORESERVE) ||
1105 			    sysctl_overcommit_memory == OVERCOMMIT_NEVER)) {
1106 		if (vm_flags & VM_SHARED) {
1107 			/* Check memory availability in shmem_file_setup? */
1108 			vm_flags |= VM_ACCOUNT;
1109 		} else if (vm_flags & VM_WRITE) {
1110 			/*
1111 			 * Private writable mapping: check memory availability
1112 			 */
1113 			charged = len >> PAGE_SHIFT;
1114 			if (security_vm_enough_memory(charged))
1115 				return -ENOMEM;
1116 			vm_flags |= VM_ACCOUNT;
1117 		}
1118 	}
1119 
1120 	/*
1121 	 * Can we just expand an old private anonymous mapping?
1122 	 * The VM_SHARED test is necessary because shmem_zero_setup
1123 	 * will create the file object for a shared anonymous map below.
1124 	 */
1125 	if (!file && !(vm_flags & VM_SHARED) &&
1126 	    vma_merge(mm, prev, addr, addr + len, vm_flags,
1127 					NULL, NULL, pgoff, NULL))
1128 		goto out;
1129 
1130 	/*
1131 	 * Determine the object being mapped and call the appropriate
1132 	 * specific mapper. the address has already been validated, but
1133 	 * not unmapped, but the maps are removed from the list.
1134 	 */
1135 	vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
1136 	if (!vma) {
1137 		error = -ENOMEM;
1138 		goto unacct_error;
1139 	}
1140 
1141 	vma->vm_mm = mm;
1142 	vma->vm_start = addr;
1143 	vma->vm_end = addr + len;
1144 	vma->vm_flags = vm_flags;
1145 	vma->vm_page_prot = vm_get_page_prot(vm_flags);
1146 	vma->vm_pgoff = pgoff;
1147 
1148 	if (file) {
1149 		error = -EINVAL;
1150 		if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1151 			goto free_vma;
1152 		if (vm_flags & VM_DENYWRITE) {
1153 			error = deny_write_access(file);
1154 			if (error)
1155 				goto free_vma;
1156 			correct_wcount = 1;
1157 		}
1158 		vma->vm_file = file;
1159 		get_file(file);
1160 		error = file->f_op->mmap(file, vma);
1161 		if (error)
1162 			goto unmap_and_free_vma;
1163 		if (vm_flags & VM_EXECUTABLE)
1164 			added_exe_file_vma(mm);
1165 	} else if (vm_flags & VM_SHARED) {
1166 		error = shmem_zero_setup(vma);
1167 		if (error)
1168 			goto free_vma;
1169 	}
1170 
1171 	/* We set VM_ACCOUNT in a shared mapping's vm_flags, to inform
1172 	 * shmem_zero_setup (perhaps called through /dev/zero's ->mmap)
1173 	 * that memory reservation must be checked; but that reservation
1174 	 * belongs to shared memory object, not to vma: so now clear it.
1175 	 */
1176 	if ((vm_flags & (VM_SHARED|VM_ACCOUNT)) == (VM_SHARED|VM_ACCOUNT))
1177 		vma->vm_flags &= ~VM_ACCOUNT;
1178 
1179 	/* Can addr have changed??
1180 	 *
1181 	 * Answer: Yes, several device drivers can do it in their
1182 	 *         f_op->mmap method. -DaveM
1183 	 */
1184 	addr = vma->vm_start;
1185 	pgoff = vma->vm_pgoff;
1186 	vm_flags = vma->vm_flags;
1187 
1188 	if (vma_wants_writenotify(vma))
1189 		vma->vm_page_prot = vm_get_page_prot(vm_flags & ~VM_SHARED);
1190 
1191 	if (file && vma_merge(mm, prev, addr, vma->vm_end,
1192 			vma->vm_flags, NULL, file, pgoff, vma_policy(vma))) {
1193 		mpol_put(vma_policy(vma));
1194 		kmem_cache_free(vm_area_cachep, vma);
1195 		fput(file);
1196 		if (vm_flags & VM_EXECUTABLE)
1197 			removed_exe_file_vma(mm);
1198 	} else {
1199 		vma_link(mm, vma, prev, rb_link, rb_parent);
1200 		file = vma->vm_file;
1201 	}
1202 
1203 	/* Once vma denies write, undo our temporary denial count */
1204 	if (correct_wcount)
1205 		atomic_inc(&inode->i_writecount);
1206 out:
1207 	mm->total_vm += len >> PAGE_SHIFT;
1208 	vm_stat_account(mm, vm_flags, file, len >> PAGE_SHIFT);
1209 	if (vm_flags & VM_LOCKED) {
1210 		mm->locked_vm += len >> PAGE_SHIFT;
1211 		make_pages_present(addr, addr + len);
1212 	}
1213 	if ((flags & MAP_POPULATE) && !(flags & MAP_NONBLOCK))
1214 		make_pages_present(addr, addr + len);
1215 	return addr;
1216 
1217 unmap_and_free_vma:
1218 	if (correct_wcount)
1219 		atomic_inc(&inode->i_writecount);
1220 	vma->vm_file = NULL;
1221 	fput(file);
1222 
1223 	/* Undo any partial mapping done by a device driver. */
1224 	unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
1225 	charged = 0;
1226 free_vma:
1227 	kmem_cache_free(vm_area_cachep, vma);
1228 unacct_error:
1229 	if (charged)
1230 		vm_unacct_memory(charged);
1231 	return error;
1232 }
1233 
1234 /* Get an address range which is currently unmapped.
1235  * For shmat() with addr=0.
1236  *
1237  * Ugly calling convention alert:
1238  * Return value with the low bits set means error value,
1239  * ie
1240  *	if (ret & ~PAGE_MASK)
1241  *		error = ret;
1242  *
1243  * This function "knows" that -ENOMEM has the bits set.
1244  */
1245 #ifndef HAVE_ARCH_UNMAPPED_AREA
1246 unsigned long
1247 arch_get_unmapped_area(struct file *filp, unsigned long addr,
1248 		unsigned long len, unsigned long pgoff, unsigned long flags)
1249 {
1250 	struct mm_struct *mm = current->mm;
1251 	struct vm_area_struct *vma;
1252 	unsigned long start_addr;
1253 
1254 	if (len > TASK_SIZE)
1255 		return -ENOMEM;
1256 
1257 	if (flags & MAP_FIXED)
1258 		return addr;
1259 
1260 	if (addr) {
1261 		addr = PAGE_ALIGN(addr);
1262 		vma = find_vma(mm, addr);
1263 		if (TASK_SIZE - len >= addr &&
1264 		    (!vma || addr + len <= vma->vm_start))
1265 			return addr;
1266 	}
1267 	if (len > mm->cached_hole_size) {
1268 	        start_addr = addr = mm->free_area_cache;
1269 	} else {
1270 	        start_addr = addr = TASK_UNMAPPED_BASE;
1271 	        mm->cached_hole_size = 0;
1272 	}
1273 
1274 full_search:
1275 	for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
1276 		/* At this point:  (!vma || addr < vma->vm_end). */
1277 		if (TASK_SIZE - len < addr) {
1278 			/*
1279 			 * Start a new search - just in case we missed
1280 			 * some holes.
1281 			 */
1282 			if (start_addr != TASK_UNMAPPED_BASE) {
1283 				addr = TASK_UNMAPPED_BASE;
1284 			        start_addr = addr;
1285 				mm->cached_hole_size = 0;
1286 				goto full_search;
1287 			}
1288 			return -ENOMEM;
1289 		}
1290 		if (!vma || addr + len <= vma->vm_start) {
1291 			/*
1292 			 * Remember the place where we stopped the search:
1293 			 */
1294 			mm->free_area_cache = addr + len;
1295 			return addr;
1296 		}
1297 		if (addr + mm->cached_hole_size < vma->vm_start)
1298 		        mm->cached_hole_size = vma->vm_start - addr;
1299 		addr = vma->vm_end;
1300 	}
1301 }
1302 #endif
1303 
1304 void arch_unmap_area(struct mm_struct *mm, unsigned long addr)
1305 {
1306 	/*
1307 	 * Is this a new hole at the lowest possible address?
1308 	 */
1309 	if (addr >= TASK_UNMAPPED_BASE && addr < mm->free_area_cache) {
1310 		mm->free_area_cache = addr;
1311 		mm->cached_hole_size = ~0UL;
1312 	}
1313 }
1314 
1315 /*
1316  * This mmap-allocator allocates new areas top-down from below the
1317  * stack's low limit (the base):
1318  */
1319 #ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
1320 unsigned long
1321 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
1322 			  const unsigned long len, const unsigned long pgoff,
1323 			  const unsigned long flags)
1324 {
1325 	struct vm_area_struct *vma;
1326 	struct mm_struct *mm = current->mm;
1327 	unsigned long addr = addr0;
1328 
1329 	/* requested length too big for entire address space */
1330 	if (len > TASK_SIZE)
1331 		return -ENOMEM;
1332 
1333 	if (flags & MAP_FIXED)
1334 		return addr;
1335 
1336 	/* requesting a specific address */
1337 	if (addr) {
1338 		addr = PAGE_ALIGN(addr);
1339 		vma = find_vma(mm, addr);
1340 		if (TASK_SIZE - len >= addr &&
1341 				(!vma || addr + len <= vma->vm_start))
1342 			return addr;
1343 	}
1344 
1345 	/* check if free_area_cache is useful for us */
1346 	if (len <= mm->cached_hole_size) {
1347  	        mm->cached_hole_size = 0;
1348  		mm->free_area_cache = mm->mmap_base;
1349  	}
1350 
1351 	/* either no address requested or can't fit in requested address hole */
1352 	addr = mm->free_area_cache;
1353 
1354 	/* make sure it can fit in the remaining address space */
1355 	if (addr > len) {
1356 		vma = find_vma(mm, addr-len);
1357 		if (!vma || addr <= vma->vm_start)
1358 			/* remember the address as a hint for next time */
1359 			return (mm->free_area_cache = addr-len);
1360 	}
1361 
1362 	if (mm->mmap_base < len)
1363 		goto bottomup;
1364 
1365 	addr = mm->mmap_base-len;
1366 
1367 	do {
1368 		/*
1369 		 * Lookup failure means no vma is above this address,
1370 		 * else if new region fits below vma->vm_start,
1371 		 * return with success:
1372 		 */
1373 		vma = find_vma(mm, addr);
1374 		if (!vma || addr+len <= vma->vm_start)
1375 			/* remember the address as a hint for next time */
1376 			return (mm->free_area_cache = addr);
1377 
1378  		/* remember the largest hole we saw so far */
1379  		if (addr + mm->cached_hole_size < vma->vm_start)
1380  		        mm->cached_hole_size = vma->vm_start - addr;
1381 
1382 		/* try just below the current vma->vm_start */
1383 		addr = vma->vm_start-len;
1384 	} while (len < vma->vm_start);
1385 
1386 bottomup:
1387 	/*
1388 	 * A failed mmap() very likely causes application failure,
1389 	 * so fall back to the bottom-up function here. This scenario
1390 	 * can happen with large stack limits and large mmap()
1391 	 * allocations.
1392 	 */
1393 	mm->cached_hole_size = ~0UL;
1394   	mm->free_area_cache = TASK_UNMAPPED_BASE;
1395 	addr = arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
1396 	/*
1397 	 * Restore the topdown base:
1398 	 */
1399 	mm->free_area_cache = mm->mmap_base;
1400 	mm->cached_hole_size = ~0UL;
1401 
1402 	return addr;
1403 }
1404 #endif
1405 
1406 void arch_unmap_area_topdown(struct mm_struct *mm, unsigned long addr)
1407 {
1408 	/*
1409 	 * Is this a new hole at the highest possible address?
1410 	 */
1411 	if (addr > mm->free_area_cache)
1412 		mm->free_area_cache = addr;
1413 
1414 	/* dont allow allocations above current base */
1415 	if (mm->free_area_cache > mm->mmap_base)
1416 		mm->free_area_cache = mm->mmap_base;
1417 }
1418 
1419 unsigned long
1420 get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
1421 		unsigned long pgoff, unsigned long flags)
1422 {
1423 	unsigned long (*get_area)(struct file *, unsigned long,
1424 				  unsigned long, unsigned long, unsigned long);
1425 
1426 	get_area = current->mm->get_unmapped_area;
1427 	if (file && file->f_op && file->f_op->get_unmapped_area)
1428 		get_area = file->f_op->get_unmapped_area;
1429 	addr = get_area(file, addr, len, pgoff, flags);
1430 	if (IS_ERR_VALUE(addr))
1431 		return addr;
1432 
1433 	if (addr > TASK_SIZE - len)
1434 		return -ENOMEM;
1435 	if (addr & ~PAGE_MASK)
1436 		return -EINVAL;
1437 
1438 	return arch_rebalance_pgtables(addr, len);
1439 }
1440 
1441 EXPORT_SYMBOL(get_unmapped_area);
1442 
1443 /* Look up the first VMA which satisfies  addr < vm_end,  NULL if none. */
1444 struct vm_area_struct * find_vma(struct mm_struct * mm, unsigned long addr)
1445 {
1446 	struct vm_area_struct *vma = NULL;
1447 
1448 	if (mm) {
1449 		/* Check the cache first. */
1450 		/* (Cache hit rate is typically around 35%.) */
1451 		vma = mm->mmap_cache;
1452 		if (!(vma && vma->vm_end > addr && vma->vm_start <= addr)) {
1453 			struct rb_node * rb_node;
1454 
1455 			rb_node = mm->mm_rb.rb_node;
1456 			vma = NULL;
1457 
1458 			while (rb_node) {
1459 				struct vm_area_struct * vma_tmp;
1460 
1461 				vma_tmp = rb_entry(rb_node,
1462 						struct vm_area_struct, vm_rb);
1463 
1464 				if (vma_tmp->vm_end > addr) {
1465 					vma = vma_tmp;
1466 					if (vma_tmp->vm_start <= addr)
1467 						break;
1468 					rb_node = rb_node->rb_left;
1469 				} else
1470 					rb_node = rb_node->rb_right;
1471 			}
1472 			if (vma)
1473 				mm->mmap_cache = vma;
1474 		}
1475 	}
1476 	return vma;
1477 }
1478 
1479 EXPORT_SYMBOL(find_vma);
1480 
1481 /* Same as find_vma, but also return a pointer to the previous VMA in *pprev. */
1482 struct vm_area_struct *
1483 find_vma_prev(struct mm_struct *mm, unsigned long addr,
1484 			struct vm_area_struct **pprev)
1485 {
1486 	struct vm_area_struct *vma = NULL, *prev = NULL;
1487 	struct rb_node * rb_node;
1488 	if (!mm)
1489 		goto out;
1490 
1491 	/* Guard against addr being lower than the first VMA */
1492 	vma = mm->mmap;
1493 
1494 	/* Go through the RB tree quickly. */
1495 	rb_node = mm->mm_rb.rb_node;
1496 
1497 	while (rb_node) {
1498 		struct vm_area_struct *vma_tmp;
1499 		vma_tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb);
1500 
1501 		if (addr < vma_tmp->vm_end) {
1502 			rb_node = rb_node->rb_left;
1503 		} else {
1504 			prev = vma_tmp;
1505 			if (!prev->vm_next || (addr < prev->vm_next->vm_end))
1506 				break;
1507 			rb_node = rb_node->rb_right;
1508 		}
1509 	}
1510 
1511 out:
1512 	*pprev = prev;
1513 	return prev ? prev->vm_next : vma;
1514 }
1515 
1516 /*
1517  * Verify that the stack growth is acceptable and
1518  * update accounting. This is shared with both the
1519  * grow-up and grow-down cases.
1520  */
1521 static int acct_stack_growth(struct vm_area_struct * vma, unsigned long size, unsigned long grow)
1522 {
1523 	struct mm_struct *mm = vma->vm_mm;
1524 	struct rlimit *rlim = current->signal->rlim;
1525 	unsigned long new_start;
1526 
1527 	/* address space limit tests */
1528 	if (!may_expand_vm(mm, grow))
1529 		return -ENOMEM;
1530 
1531 	/* Stack limit test */
1532 	if (size > rlim[RLIMIT_STACK].rlim_cur)
1533 		return -ENOMEM;
1534 
1535 	/* mlock limit tests */
1536 	if (vma->vm_flags & VM_LOCKED) {
1537 		unsigned long locked;
1538 		unsigned long limit;
1539 		locked = mm->locked_vm + grow;
1540 		limit = rlim[RLIMIT_MEMLOCK].rlim_cur >> PAGE_SHIFT;
1541 		if (locked > limit && !capable(CAP_IPC_LOCK))
1542 			return -ENOMEM;
1543 	}
1544 
1545 	/* Check to ensure the stack will not grow into a hugetlb-only region */
1546 	new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start :
1547 			vma->vm_end - size;
1548 	if (is_hugepage_only_range(vma->vm_mm, new_start, size))
1549 		return -EFAULT;
1550 
1551 	/*
1552 	 * Overcommit..  This must be the final test, as it will
1553 	 * update security statistics.
1554 	 */
1555 	if (security_vm_enough_memory(grow))
1556 		return -ENOMEM;
1557 
1558 	/* Ok, everything looks good - let it rip */
1559 	mm->total_vm += grow;
1560 	if (vma->vm_flags & VM_LOCKED)
1561 		mm->locked_vm += grow;
1562 	vm_stat_account(mm, vma->vm_flags, vma->vm_file, grow);
1563 	return 0;
1564 }
1565 
1566 #if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
1567 /*
1568  * PA-RISC uses this for its stack; IA64 for its Register Backing Store.
1569  * vma is the last one with address > vma->vm_end.  Have to extend vma.
1570  */
1571 #ifndef CONFIG_IA64
1572 static inline
1573 #endif
1574 int expand_upwards(struct vm_area_struct *vma, unsigned long address)
1575 {
1576 	int error;
1577 
1578 	if (!(vma->vm_flags & VM_GROWSUP))
1579 		return -EFAULT;
1580 
1581 	/*
1582 	 * We must make sure the anon_vma is allocated
1583 	 * so that the anon_vma locking is not a noop.
1584 	 */
1585 	if (unlikely(anon_vma_prepare(vma)))
1586 		return -ENOMEM;
1587 	anon_vma_lock(vma);
1588 
1589 	/*
1590 	 * vma->vm_start/vm_end cannot change under us because the caller
1591 	 * is required to hold the mmap_sem in read mode.  We need the
1592 	 * anon_vma lock to serialize against concurrent expand_stacks.
1593 	 * Also guard against wrapping around to address 0.
1594 	 */
1595 	if (address < PAGE_ALIGN(address+4))
1596 		address = PAGE_ALIGN(address+4);
1597 	else {
1598 		anon_vma_unlock(vma);
1599 		return -ENOMEM;
1600 	}
1601 	error = 0;
1602 
1603 	/* Somebody else might have raced and expanded it already */
1604 	if (address > vma->vm_end) {
1605 		unsigned long size, grow;
1606 
1607 		size = address - vma->vm_start;
1608 		grow = (address - vma->vm_end) >> PAGE_SHIFT;
1609 
1610 		error = acct_stack_growth(vma, size, grow);
1611 		if (!error)
1612 			vma->vm_end = address;
1613 	}
1614 	anon_vma_unlock(vma);
1615 	return error;
1616 }
1617 #endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
1618 
1619 /*
1620  * vma is the first one with address < vma->vm_start.  Have to extend vma.
1621  */
1622 static inline int expand_downwards(struct vm_area_struct *vma,
1623 				   unsigned long address)
1624 {
1625 	int error;
1626 
1627 	/*
1628 	 * We must make sure the anon_vma is allocated
1629 	 * so that the anon_vma locking is not a noop.
1630 	 */
1631 	if (unlikely(anon_vma_prepare(vma)))
1632 		return -ENOMEM;
1633 
1634 	address &= PAGE_MASK;
1635 	error = security_file_mmap(NULL, 0, 0, 0, address, 1);
1636 	if (error)
1637 		return error;
1638 
1639 	anon_vma_lock(vma);
1640 
1641 	/*
1642 	 * vma->vm_start/vm_end cannot change under us because the caller
1643 	 * is required to hold the mmap_sem in read mode.  We need the
1644 	 * anon_vma lock to serialize against concurrent expand_stacks.
1645 	 */
1646 
1647 	/* Somebody else might have raced and expanded it already */
1648 	if (address < vma->vm_start) {
1649 		unsigned long size, grow;
1650 
1651 		size = vma->vm_end - address;
1652 		grow = (vma->vm_start - address) >> PAGE_SHIFT;
1653 
1654 		error = acct_stack_growth(vma, size, grow);
1655 		if (!error) {
1656 			vma->vm_start = address;
1657 			vma->vm_pgoff -= grow;
1658 		}
1659 	}
1660 	anon_vma_unlock(vma);
1661 	return error;
1662 }
1663 
1664 int expand_stack_downwards(struct vm_area_struct *vma, unsigned long address)
1665 {
1666 	return expand_downwards(vma, address);
1667 }
1668 
1669 #ifdef CONFIG_STACK_GROWSUP
1670 int expand_stack(struct vm_area_struct *vma, unsigned long address)
1671 {
1672 	return expand_upwards(vma, address);
1673 }
1674 
1675 struct vm_area_struct *
1676 find_extend_vma(struct mm_struct *mm, unsigned long addr)
1677 {
1678 	struct vm_area_struct *vma, *prev;
1679 
1680 	addr &= PAGE_MASK;
1681 	vma = find_vma_prev(mm, addr, &prev);
1682 	if (vma && (vma->vm_start <= addr))
1683 		return vma;
1684 	if (!prev || expand_stack(prev, addr))
1685 		return NULL;
1686 	if (prev->vm_flags & VM_LOCKED)
1687 		make_pages_present(addr, prev->vm_end);
1688 	return prev;
1689 }
1690 #else
1691 int expand_stack(struct vm_area_struct *vma, unsigned long address)
1692 {
1693 	return expand_downwards(vma, address);
1694 }
1695 
1696 struct vm_area_struct *
1697 find_extend_vma(struct mm_struct * mm, unsigned long addr)
1698 {
1699 	struct vm_area_struct * vma;
1700 	unsigned long start;
1701 
1702 	addr &= PAGE_MASK;
1703 	vma = find_vma(mm,addr);
1704 	if (!vma)
1705 		return NULL;
1706 	if (vma->vm_start <= addr)
1707 		return vma;
1708 	if (!(vma->vm_flags & VM_GROWSDOWN))
1709 		return NULL;
1710 	start = vma->vm_start;
1711 	if (expand_stack(vma, addr))
1712 		return NULL;
1713 	if (vma->vm_flags & VM_LOCKED)
1714 		make_pages_present(addr, start);
1715 	return vma;
1716 }
1717 #endif
1718 
1719 /*
1720  * Ok - we have the memory areas we should free on the vma list,
1721  * so release them, and do the vma updates.
1722  *
1723  * Called with the mm semaphore held.
1724  */
1725 static void remove_vma_list(struct mm_struct *mm, struct vm_area_struct *vma)
1726 {
1727 	/* Update high watermark before we lower total_vm */
1728 	update_hiwater_vm(mm);
1729 	do {
1730 		long nrpages = vma_pages(vma);
1731 
1732 		mm->total_vm -= nrpages;
1733 		if (vma->vm_flags & VM_LOCKED)
1734 			mm->locked_vm -= nrpages;
1735 		vm_stat_account(mm, vma->vm_flags, vma->vm_file, -nrpages);
1736 		vma = remove_vma(vma);
1737 	} while (vma);
1738 	validate_mm(mm);
1739 }
1740 
1741 /*
1742  * Get rid of page table information in the indicated region.
1743  *
1744  * Called with the mm semaphore held.
1745  */
1746 static void unmap_region(struct mm_struct *mm,
1747 		struct vm_area_struct *vma, struct vm_area_struct *prev,
1748 		unsigned long start, unsigned long end)
1749 {
1750 	struct vm_area_struct *next = prev? prev->vm_next: mm->mmap;
1751 	struct mmu_gather *tlb;
1752 	unsigned long nr_accounted = 0;
1753 
1754 	lru_add_drain();
1755 	tlb = tlb_gather_mmu(mm, 0);
1756 	update_hiwater_rss(mm);
1757 	unmap_vmas(&tlb, vma, start, end, &nr_accounted, NULL);
1758 	vm_unacct_memory(nr_accounted);
1759 	free_pgtables(&tlb, vma, prev? prev->vm_end: FIRST_USER_ADDRESS,
1760 				 next? next->vm_start: 0);
1761 	tlb_finish_mmu(tlb, start, end);
1762 }
1763 
1764 /*
1765  * Create a list of vma's touched by the unmap, removing them from the mm's
1766  * vma list as we go..
1767  */
1768 static void
1769 detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
1770 	struct vm_area_struct *prev, unsigned long end)
1771 {
1772 	struct vm_area_struct **insertion_point;
1773 	struct vm_area_struct *tail_vma = NULL;
1774 	unsigned long addr;
1775 
1776 	insertion_point = (prev ? &prev->vm_next : &mm->mmap);
1777 	do {
1778 		rb_erase(&vma->vm_rb, &mm->mm_rb);
1779 		mm->map_count--;
1780 		tail_vma = vma;
1781 		vma = vma->vm_next;
1782 	} while (vma && vma->vm_start < end);
1783 	*insertion_point = vma;
1784 	tail_vma->vm_next = NULL;
1785 	if (mm->unmap_area == arch_unmap_area)
1786 		addr = prev ? prev->vm_end : mm->mmap_base;
1787 	else
1788 		addr = vma ?  vma->vm_start : mm->mmap_base;
1789 	mm->unmap_area(mm, addr);
1790 	mm->mmap_cache = NULL;		/* Kill the cache. */
1791 }
1792 
1793 /*
1794  * Split a vma into two pieces at address 'addr', a new vma is allocated
1795  * either for the first part or the tail.
1796  */
1797 int split_vma(struct mm_struct * mm, struct vm_area_struct * vma,
1798 	      unsigned long addr, int new_below)
1799 {
1800 	struct mempolicy *pol;
1801 	struct vm_area_struct *new;
1802 
1803 	if (is_vm_hugetlb_page(vma) && (addr & ~HPAGE_MASK))
1804 		return -EINVAL;
1805 
1806 	if (mm->map_count >= sysctl_max_map_count)
1807 		return -ENOMEM;
1808 
1809 	new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
1810 	if (!new)
1811 		return -ENOMEM;
1812 
1813 	/* most fields are the same, copy all, and then fixup */
1814 	*new = *vma;
1815 
1816 	if (new_below)
1817 		new->vm_end = addr;
1818 	else {
1819 		new->vm_start = addr;
1820 		new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
1821 	}
1822 
1823 	pol = mpol_dup(vma_policy(vma));
1824 	if (IS_ERR(pol)) {
1825 		kmem_cache_free(vm_area_cachep, new);
1826 		return PTR_ERR(pol);
1827 	}
1828 	vma_set_policy(new, pol);
1829 
1830 	if (new->vm_file) {
1831 		get_file(new->vm_file);
1832 		if (vma->vm_flags & VM_EXECUTABLE)
1833 			added_exe_file_vma(mm);
1834 	}
1835 
1836 	if (new->vm_ops && new->vm_ops->open)
1837 		new->vm_ops->open(new);
1838 
1839 	if (new_below)
1840 		vma_adjust(vma, addr, vma->vm_end, vma->vm_pgoff +
1841 			((addr - new->vm_start) >> PAGE_SHIFT), new);
1842 	else
1843 		vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new);
1844 
1845 	return 0;
1846 }
1847 
1848 /* Munmap is split into 2 main parts -- this part which finds
1849  * what needs doing, and the areas themselves, which do the
1850  * work.  This now handles partial unmappings.
1851  * Jeremy Fitzhardinge <jeremy@goop.org>
1852  */
1853 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
1854 {
1855 	unsigned long end;
1856 	struct vm_area_struct *vma, *prev, *last;
1857 
1858 	if ((start & ~PAGE_MASK) || start > TASK_SIZE || len > TASK_SIZE-start)
1859 		return -EINVAL;
1860 
1861 	if ((len = PAGE_ALIGN(len)) == 0)
1862 		return -EINVAL;
1863 
1864 	/* Find the first overlapping VMA */
1865 	vma = find_vma_prev(mm, start, &prev);
1866 	if (!vma)
1867 		return 0;
1868 	/* we have  start < vma->vm_end  */
1869 
1870 	/* if it doesn't overlap, we have nothing.. */
1871 	end = start + len;
1872 	if (vma->vm_start >= end)
1873 		return 0;
1874 
1875 	/*
1876 	 * If we need to split any vma, do it now to save pain later.
1877 	 *
1878 	 * Note: mremap's move_vma VM_ACCOUNT handling assumes a partially
1879 	 * unmapped vm_area_struct will remain in use: so lower split_vma
1880 	 * places tmp vma above, and higher split_vma places tmp vma below.
1881 	 */
1882 	if (start > vma->vm_start) {
1883 		int error = split_vma(mm, vma, start, 0);
1884 		if (error)
1885 			return error;
1886 		prev = vma;
1887 	}
1888 
1889 	/* Does it split the last one? */
1890 	last = find_vma(mm, end);
1891 	if (last && end > last->vm_start) {
1892 		int error = split_vma(mm, last, end, 1);
1893 		if (error)
1894 			return error;
1895 	}
1896 	vma = prev? prev->vm_next: mm->mmap;
1897 
1898 	/*
1899 	 * Remove the vma's, and unmap the actual pages
1900 	 */
1901 	detach_vmas_to_be_unmapped(mm, vma, prev, end);
1902 	unmap_region(mm, vma, prev, start, end);
1903 
1904 	/* Fix up all other VM information */
1905 	remove_vma_list(mm, vma);
1906 
1907 	return 0;
1908 }
1909 
1910 EXPORT_SYMBOL(do_munmap);
1911 
1912 asmlinkage long sys_munmap(unsigned long addr, size_t len)
1913 {
1914 	int ret;
1915 	struct mm_struct *mm = current->mm;
1916 
1917 	profile_munmap(addr);
1918 
1919 	down_write(&mm->mmap_sem);
1920 	ret = do_munmap(mm, addr, len);
1921 	up_write(&mm->mmap_sem);
1922 	return ret;
1923 }
1924 
1925 static inline void verify_mm_writelocked(struct mm_struct *mm)
1926 {
1927 #ifdef CONFIG_DEBUG_VM
1928 	if (unlikely(down_read_trylock(&mm->mmap_sem))) {
1929 		WARN_ON(1);
1930 		up_read(&mm->mmap_sem);
1931 	}
1932 #endif
1933 }
1934 
1935 /*
1936  *  this is really a simplified "do_mmap".  it only handles
1937  *  anonymous maps.  eventually we may be able to do some
1938  *  brk-specific accounting here.
1939  */
1940 unsigned long do_brk(unsigned long addr, unsigned long len)
1941 {
1942 	struct mm_struct * mm = current->mm;
1943 	struct vm_area_struct * vma, * prev;
1944 	unsigned long flags;
1945 	struct rb_node ** rb_link, * rb_parent;
1946 	pgoff_t pgoff = addr >> PAGE_SHIFT;
1947 	int error;
1948 
1949 	len = PAGE_ALIGN(len);
1950 	if (!len)
1951 		return addr;
1952 
1953 	if ((addr + len) > TASK_SIZE || (addr + len) < addr)
1954 		return -EINVAL;
1955 
1956 	if (is_hugepage_only_range(mm, addr, len))
1957 		return -EINVAL;
1958 
1959 	error = security_file_mmap(NULL, 0, 0, 0, addr, 1);
1960 	if (error)
1961 		return error;
1962 
1963 	flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
1964 
1965 	error = arch_mmap_check(addr, len, flags);
1966 	if (error)
1967 		return error;
1968 
1969 	/*
1970 	 * mlock MCL_FUTURE?
1971 	 */
1972 	if (mm->def_flags & VM_LOCKED) {
1973 		unsigned long locked, lock_limit;
1974 		locked = len >> PAGE_SHIFT;
1975 		locked += mm->locked_vm;
1976 		lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
1977 		lock_limit >>= PAGE_SHIFT;
1978 		if (locked > lock_limit && !capable(CAP_IPC_LOCK))
1979 			return -EAGAIN;
1980 	}
1981 
1982 	/*
1983 	 * mm->mmap_sem is required to protect against another thread
1984 	 * changing the mappings in case we sleep.
1985 	 */
1986 	verify_mm_writelocked(mm);
1987 
1988 	/*
1989 	 * Clear old maps.  this also does some error checking for us
1990 	 */
1991  munmap_back:
1992 	vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
1993 	if (vma && vma->vm_start < addr + len) {
1994 		if (do_munmap(mm, addr, len))
1995 			return -ENOMEM;
1996 		goto munmap_back;
1997 	}
1998 
1999 	/* Check against address space limits *after* clearing old maps... */
2000 	if (!may_expand_vm(mm, len >> PAGE_SHIFT))
2001 		return -ENOMEM;
2002 
2003 	if (mm->map_count > sysctl_max_map_count)
2004 		return -ENOMEM;
2005 
2006 	if (security_vm_enough_memory(len >> PAGE_SHIFT))
2007 		return -ENOMEM;
2008 
2009 	/* Can we just expand an old private anonymous mapping? */
2010 	if (vma_merge(mm, prev, addr, addr + len, flags,
2011 					NULL, NULL, pgoff, NULL))
2012 		goto out;
2013 
2014 	/*
2015 	 * create a vma struct for an anonymous mapping
2016 	 */
2017 	vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
2018 	if (!vma) {
2019 		vm_unacct_memory(len >> PAGE_SHIFT);
2020 		return -ENOMEM;
2021 	}
2022 
2023 	vma->vm_mm = mm;
2024 	vma->vm_start = addr;
2025 	vma->vm_end = addr + len;
2026 	vma->vm_pgoff = pgoff;
2027 	vma->vm_flags = flags;
2028 	vma->vm_page_prot = vm_get_page_prot(flags);
2029 	vma_link(mm, vma, prev, rb_link, rb_parent);
2030 out:
2031 	mm->total_vm += len >> PAGE_SHIFT;
2032 	if (flags & VM_LOCKED) {
2033 		mm->locked_vm += len >> PAGE_SHIFT;
2034 		make_pages_present(addr, addr + len);
2035 	}
2036 	return addr;
2037 }
2038 
2039 EXPORT_SYMBOL(do_brk);
2040 
2041 /* Release all mmaps. */
2042 void exit_mmap(struct mm_struct *mm)
2043 {
2044 	struct mmu_gather *tlb;
2045 	struct vm_area_struct *vma = mm->mmap;
2046 	unsigned long nr_accounted = 0;
2047 	unsigned long end;
2048 
2049 	/* mm's last user has gone, and its about to be pulled down */
2050 	arch_exit_mmap(mm);
2051 
2052 	lru_add_drain();
2053 	flush_cache_mm(mm);
2054 	tlb = tlb_gather_mmu(mm, 1);
2055 	/* Don't update_hiwater_rss(mm) here, do_exit already did */
2056 	/* Use -1 here to ensure all VMAs in the mm are unmapped */
2057 	end = unmap_vmas(&tlb, vma, 0, -1, &nr_accounted, NULL);
2058 	vm_unacct_memory(nr_accounted);
2059 	free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, 0);
2060 	tlb_finish_mmu(tlb, 0, end);
2061 
2062 	/*
2063 	 * Walk the list again, actually closing and freeing it,
2064 	 * with preemption enabled, without holding any MM locks.
2065 	 */
2066 	while (vma)
2067 		vma = remove_vma(vma);
2068 
2069 	BUG_ON(mm->nr_ptes > (FIRST_USER_ADDRESS+PMD_SIZE-1)>>PMD_SHIFT);
2070 }
2071 
2072 /* Insert vm structure into process list sorted by address
2073  * and into the inode's i_mmap tree.  If vm_file is non-NULL
2074  * then i_mmap_lock is taken here.
2075  */
2076 int insert_vm_struct(struct mm_struct * mm, struct vm_area_struct * vma)
2077 {
2078 	struct vm_area_struct * __vma, * prev;
2079 	struct rb_node ** rb_link, * rb_parent;
2080 
2081 	/*
2082 	 * The vm_pgoff of a purely anonymous vma should be irrelevant
2083 	 * until its first write fault, when page's anon_vma and index
2084 	 * are set.  But now set the vm_pgoff it will almost certainly
2085 	 * end up with (unless mremap moves it elsewhere before that
2086 	 * first wfault), so /proc/pid/maps tells a consistent story.
2087 	 *
2088 	 * By setting it to reflect the virtual start address of the
2089 	 * vma, merges and splits can happen in a seamless way, just
2090 	 * using the existing file pgoff checks and manipulations.
2091 	 * Similarly in do_mmap_pgoff and in do_brk.
2092 	 */
2093 	if (!vma->vm_file) {
2094 		BUG_ON(vma->anon_vma);
2095 		vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
2096 	}
2097 	__vma = find_vma_prepare(mm,vma->vm_start,&prev,&rb_link,&rb_parent);
2098 	if (__vma && __vma->vm_start < vma->vm_end)
2099 		return -ENOMEM;
2100 	if ((vma->vm_flags & VM_ACCOUNT) &&
2101 	     security_vm_enough_memory_mm(mm, vma_pages(vma)))
2102 		return -ENOMEM;
2103 	vma_link(mm, vma, prev, rb_link, rb_parent);
2104 	return 0;
2105 }
2106 
2107 /*
2108  * Copy the vma structure to a new location in the same mm,
2109  * prior to moving page table entries, to effect an mremap move.
2110  */
2111 struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
2112 	unsigned long addr, unsigned long len, pgoff_t pgoff)
2113 {
2114 	struct vm_area_struct *vma = *vmap;
2115 	unsigned long vma_start = vma->vm_start;
2116 	struct mm_struct *mm = vma->vm_mm;
2117 	struct vm_area_struct *new_vma, *prev;
2118 	struct rb_node **rb_link, *rb_parent;
2119 	struct mempolicy *pol;
2120 
2121 	/*
2122 	 * If anonymous vma has not yet been faulted, update new pgoff
2123 	 * to match new location, to increase its chance of merging.
2124 	 */
2125 	if (!vma->vm_file && !vma->anon_vma)
2126 		pgoff = addr >> PAGE_SHIFT;
2127 
2128 	find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
2129 	new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
2130 			vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));
2131 	if (new_vma) {
2132 		/*
2133 		 * Source vma may have been merged into new_vma
2134 		 */
2135 		if (vma_start >= new_vma->vm_start &&
2136 		    vma_start < new_vma->vm_end)
2137 			*vmap = new_vma;
2138 	} else {
2139 		new_vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
2140 		if (new_vma) {
2141 			*new_vma = *vma;
2142 			pol = mpol_dup(vma_policy(vma));
2143 			if (IS_ERR(pol)) {
2144 				kmem_cache_free(vm_area_cachep, new_vma);
2145 				return NULL;
2146 			}
2147 			vma_set_policy(new_vma, pol);
2148 			new_vma->vm_start = addr;
2149 			new_vma->vm_end = addr + len;
2150 			new_vma->vm_pgoff = pgoff;
2151 			if (new_vma->vm_file) {
2152 				get_file(new_vma->vm_file);
2153 				if (vma->vm_flags & VM_EXECUTABLE)
2154 					added_exe_file_vma(mm);
2155 			}
2156 			if (new_vma->vm_ops && new_vma->vm_ops->open)
2157 				new_vma->vm_ops->open(new_vma);
2158 			vma_link(mm, new_vma, prev, rb_link, rb_parent);
2159 		}
2160 	}
2161 	return new_vma;
2162 }
2163 
2164 /*
2165  * Return true if the calling process may expand its vm space by the passed
2166  * number of pages
2167  */
2168 int may_expand_vm(struct mm_struct *mm, unsigned long npages)
2169 {
2170 	unsigned long cur = mm->total_vm;	/* pages */
2171 	unsigned long lim;
2172 
2173 	lim = current->signal->rlim[RLIMIT_AS].rlim_cur >> PAGE_SHIFT;
2174 
2175 	if (cur + npages > lim)
2176 		return 0;
2177 	return 1;
2178 }
2179 
2180 
2181 static int special_mapping_fault(struct vm_area_struct *vma,
2182 				struct vm_fault *vmf)
2183 {
2184 	pgoff_t pgoff;
2185 	struct page **pages;
2186 
2187 	/*
2188 	 * special mappings have no vm_file, and in that case, the mm
2189 	 * uses vm_pgoff internally. So we have to subtract it from here.
2190 	 * We are allowed to do this because we are the mm; do not copy
2191 	 * this code into drivers!
2192 	 */
2193 	pgoff = vmf->pgoff - vma->vm_pgoff;
2194 
2195 	for (pages = vma->vm_private_data; pgoff && *pages; ++pages)
2196 		pgoff--;
2197 
2198 	if (*pages) {
2199 		struct page *page = *pages;
2200 		get_page(page);
2201 		vmf->page = page;
2202 		return 0;
2203 	}
2204 
2205 	return VM_FAULT_SIGBUS;
2206 }
2207 
2208 /*
2209  * Having a close hook prevents vma merging regardless of flags.
2210  */
2211 static void special_mapping_close(struct vm_area_struct *vma)
2212 {
2213 }
2214 
2215 static struct vm_operations_struct special_mapping_vmops = {
2216 	.close = special_mapping_close,
2217 	.fault = special_mapping_fault,
2218 };
2219 
2220 /*
2221  * Called with mm->mmap_sem held for writing.
2222  * Insert a new vma covering the given region, with the given flags.
2223  * Its pages are supplied by the given array of struct page *.
2224  * The array can be shorter than len >> PAGE_SHIFT if it's null-terminated.
2225  * The region past the last page supplied will always produce SIGBUS.
2226  * The array pointer and the pages it points to are assumed to stay alive
2227  * for as long as this mapping might exist.
2228  */
2229 int install_special_mapping(struct mm_struct *mm,
2230 			    unsigned long addr, unsigned long len,
2231 			    unsigned long vm_flags, struct page **pages)
2232 {
2233 	struct vm_area_struct *vma;
2234 
2235 	vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
2236 	if (unlikely(vma == NULL))
2237 		return -ENOMEM;
2238 
2239 	vma->vm_mm = mm;
2240 	vma->vm_start = addr;
2241 	vma->vm_end = addr + len;
2242 
2243 	vma->vm_flags = vm_flags | mm->def_flags | VM_DONTEXPAND;
2244 	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
2245 
2246 	vma->vm_ops = &special_mapping_vmops;
2247 	vma->vm_private_data = pages;
2248 
2249 	if (unlikely(insert_vm_struct(mm, vma))) {
2250 		kmem_cache_free(vm_area_cachep, vma);
2251 		return -ENOMEM;
2252 	}
2253 
2254 	mm->total_vm += len >> PAGE_SHIFT;
2255 
2256 	return 0;
2257 }
2258