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1 | /* | |
2 | * mm/mremap.c | |
3 | * | |
4 | * (C) Copyright 1996 Linus Torvalds | |
5 | * | |
6 | * Address space accounting code <alan@lxorguk.ukuu.org.uk> | |
7 | * (C) Copyright 2002 Red Hat Inc, All Rights Reserved | |
8 | */ | |
9 | ||
10 | #include <linux/mm.h> | |
11 | #include <linux/hugetlb.h> | |
12 | #include <linux/shm.h> | |
13 | #include <linux/ksm.h> | |
14 | #include <linux/mman.h> | |
15 | #include <linux/swap.h> | |
16 | #include <linux/capability.h> | |
17 | #include <linux/fs.h> | |
18 | #include <linux/highmem.h> | |
19 | #include <linux/security.h> | |
20 | #include <linux/syscalls.h> | |
21 | #include <linux/mmu_notifier.h> | |
22 | ||
23 | #include <asm/uaccess.h> | |
24 | #include <asm/cacheflush.h> | |
25 | #include <asm/tlbflush.h> | |
26 | ||
27 | #include "internal.h" | |
28 | ||
29 | static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr) | |
30 | { | |
31 | pgd_t *pgd; | |
32 | pud_t *pud; | |
33 | pmd_t *pmd; | |
34 | ||
35 | pgd = pgd_offset(mm, addr); | |
36 | if (pgd_none_or_clear_bad(pgd)) | |
37 | return NULL; | |
38 | ||
39 | pud = pud_offset(pgd, addr); | |
40 | if (pud_none_or_clear_bad(pud)) | |
41 | return NULL; | |
42 | ||
43 | pmd = pmd_offset(pud, addr); | |
44 | split_huge_page_pmd(mm, pmd); | |
45 | if (pmd_none_or_clear_bad(pmd)) | |
46 | return NULL; | |
47 | ||
48 | return pmd; | |
49 | } | |
50 | ||
51 | static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma, | |
52 | unsigned long addr) | |
53 | { | |
54 | pgd_t *pgd; | |
55 | pud_t *pud; | |
56 | pmd_t *pmd; | |
57 | ||
58 | pgd = pgd_offset(mm, addr); | |
59 | pud = pud_alloc(mm, pgd, addr); | |
60 | if (!pud) | |
61 | return NULL; | |
62 | ||
63 | pmd = pmd_alloc(mm, pud, addr); | |
64 | if (!pmd) | |
65 | return NULL; | |
66 | ||
67 | VM_BUG_ON(pmd_trans_huge(*pmd)); | |
68 | if (pmd_none(*pmd) && __pte_alloc(mm, vma, pmd, addr)) | |
69 | return NULL; | |
70 | ||
71 | return pmd; | |
72 | } | |
73 | ||
74 | static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, | |
75 | unsigned long old_addr, unsigned long old_end, | |
76 | struct vm_area_struct *new_vma, pmd_t *new_pmd, | |
77 | unsigned long new_addr) | |
78 | { | |
79 | struct address_space *mapping = NULL; | |
80 | struct mm_struct *mm = vma->vm_mm; | |
81 | pte_t *old_pte, *new_pte, pte; | |
82 | spinlock_t *old_ptl, *new_ptl; | |
83 | unsigned long old_start; | |
84 | ||
85 | old_start = old_addr; | |
86 | mmu_notifier_invalidate_range_start(vma->vm_mm, | |
87 | old_start, old_end); | |
88 | if (vma->vm_file) { | |
89 | /* | |
90 | * Subtle point from Rajesh Venkatasubramanian: before | |
91 | * moving file-based ptes, we must lock truncate_pagecache | |
92 | * out, since it might clean the dst vma before the src vma, | |
93 | * and we propagate stale pages into the dst afterward. | |
94 | */ | |
95 | mapping = vma->vm_file->f_mapping; | |
96 | mutex_lock(&mapping->i_mmap_mutex); | |
97 | } | |
98 | ||
99 | /* | |
100 | * We don't have to worry about the ordering of src and dst | |
101 | * pte locks because exclusive mmap_sem prevents deadlock. | |
102 | */ | |
103 | old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl); | |
104 | new_pte = pte_offset_map(new_pmd, new_addr); | |
105 | new_ptl = pte_lockptr(mm, new_pmd); | |
106 | if (new_ptl != old_ptl) | |
107 | spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); | |
108 | arch_enter_lazy_mmu_mode(); | |
109 | ||
110 | for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE, | |
111 | new_pte++, new_addr += PAGE_SIZE) { | |
112 | if (pte_none(*old_pte)) | |
113 | continue; | |
114 | pte = ptep_clear_flush(vma, old_addr, old_pte); | |
115 | pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr); | |
116 | set_pte_at(mm, new_addr, new_pte, pte); | |
117 | } | |
118 | ||
119 | arch_leave_lazy_mmu_mode(); | |
120 | if (new_ptl != old_ptl) | |
121 | spin_unlock(new_ptl); | |
122 | pte_unmap(new_pte - 1); | |
123 | pte_unmap_unlock(old_pte - 1, old_ptl); | |
124 | if (mapping) | |
125 | mutex_unlock(&mapping->i_mmap_mutex); | |
126 | mmu_notifier_invalidate_range_end(vma->vm_mm, old_start, old_end); | |
127 | } | |
128 | ||
129 | #define LATENCY_LIMIT (64 * PAGE_SIZE) | |
130 | ||
131 | unsigned long move_page_tables(struct vm_area_struct *vma, | |
132 | unsigned long old_addr, struct vm_area_struct *new_vma, | |
133 | unsigned long new_addr, unsigned long len) | |
134 | { | |
135 | unsigned long extent, next, old_end; | |
136 | pmd_t *old_pmd, *new_pmd; | |
137 | ||
138 | old_end = old_addr + len; | |
139 | flush_cache_range(vma, old_addr, old_end); | |
140 | ||
141 | for (; old_addr < old_end; old_addr += extent, new_addr += extent) { | |
142 | cond_resched(); | |
143 | next = (old_addr + PMD_SIZE) & PMD_MASK; | |
144 | if (next - 1 > old_end) | |
145 | next = old_end; | |
146 | extent = next - old_addr; | |
147 | old_pmd = get_old_pmd(vma->vm_mm, old_addr); | |
148 | if (!old_pmd) | |
149 | continue; | |
150 | new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr); | |
151 | if (!new_pmd) | |
152 | break; | |
153 | next = (new_addr + PMD_SIZE) & PMD_MASK; | |
154 | if (extent > next - new_addr) | |
155 | extent = next - new_addr; | |
156 | if (extent > LATENCY_LIMIT) | |
157 | extent = LATENCY_LIMIT; | |
158 | move_ptes(vma, old_pmd, old_addr, old_addr + extent, | |
159 | new_vma, new_pmd, new_addr); | |
160 | } | |
161 | ||
162 | return len + old_addr - old_end; /* how much done */ | |
163 | } | |
164 | ||
165 | static unsigned long move_vma(struct vm_area_struct *vma, | |
166 | unsigned long old_addr, unsigned long old_len, | |
167 | unsigned long new_len, unsigned long new_addr) | |
168 | { | |
169 | struct mm_struct *mm = vma->vm_mm; | |
170 | struct vm_area_struct *new_vma; | |
171 | unsigned long vm_flags = vma->vm_flags; | |
172 | unsigned long new_pgoff; | |
173 | unsigned long moved_len; | |
174 | unsigned long excess = 0; | |
175 | unsigned long hiwater_vm; | |
176 | int split = 0; | |
177 | int err; | |
178 | ||
179 | /* | |
180 | * We'd prefer to avoid failure later on in do_munmap: | |
181 | * which may split one vma into three before unmapping. | |
182 | */ | |
183 | if (mm->map_count >= sysctl_max_map_count - 3) | |
184 | return -ENOMEM; | |
185 | ||
186 | /* | |
187 | * Advise KSM to break any KSM pages in the area to be moved: | |
188 | * it would be confusing if they were to turn up at the new | |
189 | * location, where they happen to coincide with different KSM | |
190 | * pages recently unmapped. But leave vma->vm_flags as it was, | |
191 | * so KSM can come around to merge on vma and new_vma afterwards. | |
192 | */ | |
193 | err = ksm_madvise(vma, old_addr, old_addr + old_len, | |
194 | MADV_UNMERGEABLE, &vm_flags); | |
195 | if (err) | |
196 | return err; | |
197 | ||
198 | new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT); | |
199 | new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff); | |
200 | if (!new_vma) | |
201 | return -ENOMEM; | |
202 | ||
203 | moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len); | |
204 | if (moved_len < old_len) { | |
205 | /* | |
206 | * On error, move entries back from new area to old, | |
207 | * which will succeed since page tables still there, | |
208 | * and then proceed to unmap new area instead of old. | |
209 | */ | |
210 | move_page_tables(new_vma, new_addr, vma, old_addr, moved_len); | |
211 | vma = new_vma; | |
212 | old_len = new_len; | |
213 | old_addr = new_addr; | |
214 | new_addr = -ENOMEM; | |
215 | } | |
216 | ||
217 | /* Conceal VM_ACCOUNT so old reservation is not undone */ | |
218 | if (vm_flags & VM_ACCOUNT) { | |
219 | vma->vm_flags &= ~VM_ACCOUNT; | |
220 | excess = vma->vm_end - vma->vm_start - old_len; | |
221 | if (old_addr > vma->vm_start && | |
222 | old_addr + old_len < vma->vm_end) | |
223 | split = 1; | |
224 | } | |
225 | ||
226 | /* | |
227 | * If we failed to move page tables we still do total_vm increment | |
228 | * since do_munmap() will decrement it by old_len == new_len. | |
229 | * | |
230 | * Since total_vm is about to be raised artificially high for a | |
231 | * moment, we need to restore high watermark afterwards: if stats | |
232 | * are taken meanwhile, total_vm and hiwater_vm appear too high. | |
233 | * If this were a serious issue, we'd add a flag to do_munmap(). | |
234 | */ | |
235 | hiwater_vm = mm->hiwater_vm; | |
236 | mm->total_vm += new_len >> PAGE_SHIFT; | |
237 | vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT); | |
238 | ||
239 | if (do_munmap(mm, old_addr, old_len) < 0) { | |
240 | /* OOM: unable to split vma, just get accounts right */ | |
241 | vm_unacct_memory(excess >> PAGE_SHIFT); | |
242 | excess = 0; | |
243 | } | |
244 | mm->hiwater_vm = hiwater_vm; | |
245 | ||
246 | /* Restore VM_ACCOUNT if one or two pieces of vma left */ | |
247 | if (excess) { | |
248 | vma->vm_flags |= VM_ACCOUNT; | |
249 | if (split) | |
250 | vma->vm_next->vm_flags |= VM_ACCOUNT; | |
251 | } | |
252 | ||
253 | if (vm_flags & VM_LOCKED) { | |
254 | mm->locked_vm += new_len >> PAGE_SHIFT; | |
255 | if (new_len > old_len) | |
256 | mlock_vma_pages_range(new_vma, new_addr + old_len, | |
257 | new_addr + new_len); | |
258 | } | |
259 | ||
260 | return new_addr; | |
261 | } | |
262 | ||
263 | static struct vm_area_struct *vma_to_resize(unsigned long addr, | |
264 | unsigned long old_len, unsigned long new_len, unsigned long *p) | |
265 | { | |
266 | struct mm_struct *mm = current->mm; | |
267 | struct vm_area_struct *vma = find_vma(mm, addr); | |
268 | ||
269 | if (!vma || vma->vm_start > addr) | |
270 | goto Efault; | |
271 | ||
272 | if (is_vm_hugetlb_page(vma)) | |
273 | goto Einval; | |
274 | ||
275 | /* We can't remap across vm area boundaries */ | |
276 | if (old_len > vma->vm_end - addr) | |
277 | goto Efault; | |
278 | ||
279 | /* Need to be careful about a growing mapping */ | |
280 | if (new_len > old_len) { | |
281 | unsigned long pgoff; | |
282 | ||
283 | if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) | |
284 | goto Efault; | |
285 | pgoff = (addr - vma->vm_start) >> PAGE_SHIFT; | |
286 | pgoff += vma->vm_pgoff; | |
287 | if (pgoff + (new_len >> PAGE_SHIFT) < pgoff) | |
288 | goto Einval; | |
289 | } | |
290 | ||
291 | if (vma->vm_flags & VM_LOCKED) { | |
292 | unsigned long locked, lock_limit; | |
293 | locked = mm->locked_vm << PAGE_SHIFT; | |
294 | lock_limit = rlimit(RLIMIT_MEMLOCK); | |
295 | locked += new_len - old_len; | |
296 | if (locked > lock_limit && !capable(CAP_IPC_LOCK)) | |
297 | goto Eagain; | |
298 | } | |
299 | ||
300 | if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) | |
301 | goto Enomem; | |
302 | ||
303 | if (vma->vm_flags & VM_ACCOUNT) { | |
304 | unsigned long charged = (new_len - old_len) >> PAGE_SHIFT; | |
305 | if (security_vm_enough_memory(charged)) | |
306 | goto Efault; | |
307 | *p = charged; | |
308 | } | |
309 | ||
310 | return vma; | |
311 | ||
312 | Efault: /* very odd choice for most of the cases, but... */ | |
313 | return ERR_PTR(-EFAULT); | |
314 | Einval: | |
315 | return ERR_PTR(-EINVAL); | |
316 | Enomem: | |
317 | return ERR_PTR(-ENOMEM); | |
318 | Eagain: | |
319 | return ERR_PTR(-EAGAIN); | |
320 | } | |
321 | ||
322 | static unsigned long mremap_to(unsigned long addr, | |
323 | unsigned long old_len, unsigned long new_addr, | |
324 | unsigned long new_len) | |
325 | { | |
326 | struct mm_struct *mm = current->mm; | |
327 | struct vm_area_struct *vma; | |
328 | unsigned long ret = -EINVAL; | |
329 | unsigned long charged = 0; | |
330 | unsigned long map_flags; | |
331 | ||
332 | if (new_addr & ~PAGE_MASK) | |
333 | goto out; | |
334 | ||
335 | if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len) | |
336 | goto out; | |
337 | ||
338 | /* Check if the location we're moving into overlaps the | |
339 | * old location at all, and fail if it does. | |
340 | */ | |
341 | if ((new_addr <= addr) && (new_addr+new_len) > addr) | |
342 | goto out; | |
343 | ||
344 | if ((addr <= new_addr) && (addr+old_len) > new_addr) | |
345 | goto out; | |
346 | ||
347 | ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1); | |
348 | if (ret) | |
349 | goto out; | |
350 | ||
351 | ret = do_munmap(mm, new_addr, new_len); | |
352 | if (ret) | |
353 | goto out; | |
354 | ||
355 | if (old_len >= new_len) { | |
356 | ret = do_munmap(mm, addr+new_len, old_len - new_len); | |
357 | if (ret && old_len != new_len) | |
358 | goto out; | |
359 | old_len = new_len; | |
360 | } | |
361 | ||
362 | vma = vma_to_resize(addr, old_len, new_len, &charged); | |
363 | if (IS_ERR(vma)) { | |
364 | ret = PTR_ERR(vma); | |
365 | goto out; | |
366 | } | |
367 | ||
368 | map_flags = MAP_FIXED; | |
369 | if (vma->vm_flags & VM_MAYSHARE) | |
370 | map_flags |= MAP_SHARED; | |
371 | ||
372 | ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff + | |
373 | ((addr - vma->vm_start) >> PAGE_SHIFT), | |
374 | map_flags); | |
375 | if (ret & ~PAGE_MASK) | |
376 | goto out1; | |
377 | ||
378 | ret = move_vma(vma, addr, old_len, new_len, new_addr); | |
379 | if (!(ret & ~PAGE_MASK)) | |
380 | goto out; | |
381 | out1: | |
382 | vm_unacct_memory(charged); | |
383 | ||
384 | out: | |
385 | return ret; | |
386 | } | |
387 | ||
388 | static int vma_expandable(struct vm_area_struct *vma, unsigned long delta) | |
389 | { | |
390 | unsigned long end = vma->vm_end + delta; | |
391 | if (end < vma->vm_end) /* overflow */ | |
392 | return 0; | |
393 | if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */ | |
394 | return 0; | |
395 | if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start, | |
396 | 0, MAP_FIXED) & ~PAGE_MASK) | |
397 | return 0; | |
398 | return 1; | |
399 | } | |
400 | ||
401 | /* | |
402 | * Expand (or shrink) an existing mapping, potentially moving it at the | |
403 | * same time (controlled by the MREMAP_MAYMOVE flag and available VM space) | |
404 | * | |
405 | * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise | |
406 | * This option implies MREMAP_MAYMOVE. | |
407 | */ | |
408 | unsigned long do_mremap(unsigned long addr, | |
409 | unsigned long old_len, unsigned long new_len, | |
410 | unsigned long flags, unsigned long new_addr) | |
411 | { | |
412 | struct mm_struct *mm = current->mm; | |
413 | struct vm_area_struct *vma; | |
414 | unsigned long ret = -EINVAL; | |
415 | unsigned long charged = 0; | |
416 | ||
417 | if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE)) | |
418 | goto out; | |
419 | ||
420 | if (addr & ~PAGE_MASK) | |
421 | goto out; | |
422 | ||
423 | old_len = PAGE_ALIGN(old_len); | |
424 | new_len = PAGE_ALIGN(new_len); | |
425 | ||
426 | /* | |
427 | * We allow a zero old-len as a special case | |
428 | * for DOS-emu "duplicate shm area" thing. But | |
429 | * a zero new-len is nonsensical. | |
430 | */ | |
431 | if (!new_len) | |
432 | goto out; | |
433 | ||
434 | if (flags & MREMAP_FIXED) { | |
435 | if (flags & MREMAP_MAYMOVE) | |
436 | ret = mremap_to(addr, old_len, new_addr, new_len); | |
437 | goto out; | |
438 | } | |
439 | ||
440 | /* | |
441 | * Always allow a shrinking remap: that just unmaps | |
442 | * the unnecessary pages.. | |
443 | * do_munmap does all the needed commit accounting | |
444 | */ | |
445 | if (old_len >= new_len) { | |
446 | ret = do_munmap(mm, addr+new_len, old_len - new_len); | |
447 | if (ret && old_len != new_len) | |
448 | goto out; | |
449 | ret = addr; | |
450 | goto out; | |
451 | } | |
452 | ||
453 | /* | |
454 | * Ok, we need to grow.. | |
455 | */ | |
456 | vma = vma_to_resize(addr, old_len, new_len, &charged); | |
457 | if (IS_ERR(vma)) { | |
458 | ret = PTR_ERR(vma); | |
459 | goto out; | |
460 | } | |
461 | ||
462 | /* old_len exactly to the end of the area.. | |
463 | */ | |
464 | if (old_len == vma->vm_end - addr) { | |
465 | /* can we just expand the current mapping? */ | |
466 | if (vma_expandable(vma, new_len - old_len)) { | |
467 | int pages = (new_len - old_len) >> PAGE_SHIFT; | |
468 | ||
469 | if (vma_adjust(vma, vma->vm_start, addr + new_len, | |
470 | vma->vm_pgoff, NULL)) { | |
471 | ret = -ENOMEM; | |
472 | goto out; | |
473 | } | |
474 | ||
475 | mm->total_vm += pages; | |
476 | vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages); | |
477 | if (vma->vm_flags & VM_LOCKED) { | |
478 | mm->locked_vm += pages; | |
479 | mlock_vma_pages_range(vma, addr + old_len, | |
480 | addr + new_len); | |
481 | } | |
482 | ret = addr; | |
483 | goto out; | |
484 | } | |
485 | } | |
486 | ||
487 | /* | |
488 | * We weren't able to just expand or shrink the area, | |
489 | * we need to create a new one and move it.. | |
490 | */ | |
491 | ret = -ENOMEM; | |
492 | if (flags & MREMAP_MAYMOVE) { | |
493 | unsigned long map_flags = 0; | |
494 | if (vma->vm_flags & VM_MAYSHARE) | |
495 | map_flags |= MAP_SHARED; | |
496 | ||
497 | new_addr = get_unmapped_area(vma->vm_file, 0, new_len, | |
498 | vma->vm_pgoff + | |
499 | ((addr - vma->vm_start) >> PAGE_SHIFT), | |
500 | map_flags); | |
501 | if (new_addr & ~PAGE_MASK) { | |
502 | ret = new_addr; | |
503 | goto out; | |
504 | } | |
505 | ||
506 | ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1); | |
507 | if (ret) | |
508 | goto out; | |
509 | ret = move_vma(vma, addr, old_len, new_len, new_addr); | |
510 | } | |
511 | out: | |
512 | if (ret & ~PAGE_MASK) | |
513 | vm_unacct_memory(charged); | |
514 | return ret; | |
515 | } | |
516 | ||
517 | SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, | |
518 | unsigned long, new_len, unsigned long, flags, | |
519 | unsigned long, new_addr) | |
520 | { | |
521 | unsigned long ret; | |
522 | ||
523 | down_write(¤t->mm->mmap_sem); | |
524 | ret = do_mremap(addr, old_len, new_len, flags, new_addr); | |
525 | up_write(¤t->mm->mmap_sem); | |
526 | return ret; | |
527 | } |