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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 | } |
528 |
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