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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * mm/mremap.c
3 *
4 * (C) Copyright 1996 Linus Torvalds
5 *
6 * Address space accounting code <alan@redhat.com>
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/slab.h>
13#include <linux/shm.h>
14#include <linux/mman.h>
15#include <linux/swap.h>
16#include <linux/fs.h>
17#include <linux/highmem.h>
18#include <linux/security.h>
19#include <linux/syscalls.h>
20
21#include <asm/uaccess.h>
22#include <asm/cacheflush.h>
23#include <asm/tlbflush.h>
24
25static pte_t *get_one_pte_map_nested(struct mm_struct *mm, unsigned long addr)
26{
27 pgd_t *pgd;
28 pud_t *pud;
29 pmd_t *pmd;
30 pte_t *pte = NULL;
31
32 pgd = pgd_offset(mm, addr);
33 if (pgd_none_or_clear_bad(pgd))
34 goto end;
35
36 pud = pud_offset(pgd, addr);
37 if (pud_none_or_clear_bad(pud))
38 goto end;
39
40 pmd = pmd_offset(pud, addr);
41 if (pmd_none_or_clear_bad(pmd))
42 goto end;
43
44 pte = pte_offset_map_nested(pmd, addr);
45 if (pte_none(*pte)) {
46 pte_unmap_nested(pte);
47 pte = NULL;
48 }
49end:
50 return pte;
51}
52
53static pte_t *get_one_pte_map(struct mm_struct *mm, unsigned long addr)
54{
55 pgd_t *pgd;
56 pud_t *pud;
57 pmd_t *pmd;
58
59 pgd = pgd_offset(mm, addr);
60 if (pgd_none_or_clear_bad(pgd))
61 return NULL;
62
63 pud = pud_offset(pgd, addr);
64 if (pud_none_or_clear_bad(pud))
65 return NULL;
66
67 pmd = pmd_offset(pud, addr);
68 if (pmd_none_or_clear_bad(pmd))
69 return NULL;
70
71 return pte_offset_map(pmd, addr);
72}
73
74static inline pte_t *alloc_one_pte_map(struct mm_struct *mm, unsigned long addr)
75{
76 pgd_t *pgd;
77 pud_t *pud;
78 pmd_t *pmd;
79 pte_t *pte = NULL;
80
81 pgd = pgd_offset(mm, addr);
82
83 pud = pud_alloc(mm, pgd, addr);
84 if (!pud)
85 return NULL;
86 pmd = pmd_alloc(mm, pud, addr);
87 if (pmd)
88 pte = pte_alloc_map(mm, pmd, addr);
89 return pte;
90}
91
92static int
93move_one_page(struct vm_area_struct *vma, unsigned long old_addr,
94 struct vm_area_struct *new_vma, unsigned long new_addr)
95{
96 struct address_space *mapping = NULL;
97 struct mm_struct *mm = vma->vm_mm;
98 int error = 0;
99 pte_t *src, *dst;
100
101 if (vma->vm_file) {
102 /*
103 * Subtle point from Rajesh Venkatasubramanian: before
104 * moving file-based ptes, we must lock vmtruncate out,
105 * since it might clean the dst vma before the src vma,
106 * and we propagate stale pages into the dst afterward.
107 */
108 mapping = vma->vm_file->f_mapping;
109 spin_lock(&mapping->i_mmap_lock);
110 if (new_vma->vm_truncate_count &&
111 new_vma->vm_truncate_count != vma->vm_truncate_count)
112 new_vma->vm_truncate_count = 0;
113 }
114 spin_lock(&mm->page_table_lock);
115
116 src = get_one_pte_map_nested(mm, old_addr);
117 if (src) {
118 /*
119 * Look to see whether alloc_one_pte_map needs to perform a
120 * memory allocation. If it does then we need to drop the
121 * atomic kmap
122 */
123 dst = get_one_pte_map(mm, new_addr);
124 if (unlikely(!dst)) {
125 pte_unmap_nested(src);
126 if (mapping)
127 spin_unlock(&mapping->i_mmap_lock);
128 dst = alloc_one_pte_map(mm, new_addr);
129 if (mapping && !spin_trylock(&mapping->i_mmap_lock)) {
130 spin_unlock(&mm->page_table_lock);
131 spin_lock(&mapping->i_mmap_lock);
132 spin_lock(&mm->page_table_lock);
133 }
134 src = get_one_pte_map_nested(mm, old_addr);
135 }
136 /*
137 * Since alloc_one_pte_map can drop and re-acquire
138 * page_table_lock, we should re-check the src entry...
139 */
140 if (src) {
141 if (dst) {
142 pte_t pte;
143 pte = ptep_clear_flush(vma, old_addr, src);
Nick Piggin9a61c342005-09-03 15:54:49 -0700144 /* ZERO_PAGE can be dependant on virtual addr */
145 if (pfn_valid(pte_pfn(pte)) &&
146 pte_page(pte) == ZERO_PAGE(old_addr))
147 pte = pte_wrprotect(mk_pte(ZERO_PAGE(new_addr), new_vma->vm_page_prot));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700148 set_pte_at(mm, new_addr, dst, pte);
149 } else
150 error = -ENOMEM;
151 pte_unmap_nested(src);
152 }
153 if (dst)
154 pte_unmap(dst);
155 }
156 spin_unlock(&mm->page_table_lock);
157 if (mapping)
158 spin_unlock(&mapping->i_mmap_lock);
159 return error;
160}
161
162static unsigned long move_page_tables(struct vm_area_struct *vma,
163 unsigned long old_addr, struct vm_area_struct *new_vma,
164 unsigned long new_addr, unsigned long len)
165{
166 unsigned long offset;
167
168 flush_cache_range(vma, old_addr, old_addr + len);
169
170 /*
171 * This is not the clever way to do this, but we're taking the
172 * easy way out on the assumption that most remappings will be
173 * only a few pages.. This also makes error recovery easier.
174 */
175 for (offset = 0; offset < len; offset += PAGE_SIZE) {
176 if (move_one_page(vma, old_addr + offset,
177 new_vma, new_addr + offset) < 0)
178 break;
179 cond_resched();
180 }
181 return offset;
182}
183
184static unsigned long move_vma(struct vm_area_struct *vma,
185 unsigned long old_addr, unsigned long old_len,
186 unsigned long new_len, unsigned long new_addr)
187{
188 struct mm_struct *mm = vma->vm_mm;
189 struct vm_area_struct *new_vma;
190 unsigned long vm_flags = vma->vm_flags;
191 unsigned long new_pgoff;
192 unsigned long moved_len;
193 unsigned long excess = 0;
194 int split = 0;
195
196 /*
197 * We'd prefer to avoid failure later on in do_munmap:
198 * which may split one vma into three before unmapping.
199 */
200 if (mm->map_count >= sysctl_max_map_count - 3)
201 return -ENOMEM;
202
203 new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
204 new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
205 if (!new_vma)
206 return -ENOMEM;
207
208 moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
209 if (moved_len < old_len) {
210 /*
211 * On error, move entries back from new area to old,
212 * which will succeed since page tables still there,
213 * and then proceed to unmap new area instead of old.
214 */
215 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
216 vma = new_vma;
217 old_len = new_len;
218 old_addr = new_addr;
219 new_addr = -ENOMEM;
220 }
221
222 /* Conceal VM_ACCOUNT so old reservation is not undone */
223 if (vm_flags & VM_ACCOUNT) {
224 vma->vm_flags &= ~VM_ACCOUNT;
225 excess = vma->vm_end - vma->vm_start - old_len;
226 if (old_addr > vma->vm_start &&
227 old_addr + old_len < vma->vm_end)
228 split = 1;
229 }
230
Kirill Korotaev71799062005-05-16 21:53:18 -0700231 /*
232 * if we failed to move page tables we still do total_vm increment
233 * since do_munmap() will decrement it by old_len == new_len
234 */
235 mm->total_vm += new_len >> PAGE_SHIFT;
Hugh Dickins1c5ad842005-08-04 13:07:09 -0700236 __vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
Kirill Korotaev71799062005-05-16 21:53:18 -0700237
Linus Torvalds1da177e2005-04-16 15:20:36 -0700238 if (do_munmap(mm, old_addr, old_len) < 0) {
239 /* OOM: unable to split vma, just get accounts right */
240 vm_unacct_memory(excess >> PAGE_SHIFT);
241 excess = 0;
242 }
243
244 /* Restore VM_ACCOUNT if one or two pieces of vma left */
245 if (excess) {
246 vma->vm_flags |= VM_ACCOUNT;
247 if (split)
248 vma->vm_next->vm_flags |= VM_ACCOUNT;
249 }
250
Linus Torvalds1da177e2005-04-16 15:20:36 -0700251 if (vm_flags & VM_LOCKED) {
252 mm->locked_vm += new_len >> PAGE_SHIFT;
253 if (new_len > old_len)
254 make_pages_present(new_addr + old_len,
255 new_addr + new_len);
256 }
257
258 return new_addr;
259}
260
261/*
262 * Expand (or shrink) an existing mapping, potentially moving it at the
263 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
264 *
265 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
266 * This option implies MREMAP_MAYMOVE.
267 */
268unsigned long do_mremap(unsigned long addr,
269 unsigned long old_len, unsigned long new_len,
270 unsigned long flags, unsigned long new_addr)
271{
272 struct vm_area_struct *vma;
273 unsigned long ret = -EINVAL;
274 unsigned long charged = 0;
275
276 if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
277 goto out;
278
279 if (addr & ~PAGE_MASK)
280 goto out;
281
282 old_len = PAGE_ALIGN(old_len);
283 new_len = PAGE_ALIGN(new_len);
284
285 /*
286 * We allow a zero old-len as a special case
287 * for DOS-emu "duplicate shm area" thing. But
288 * a zero new-len is nonsensical.
289 */
290 if (!new_len)
291 goto out;
292
293 /* new_addr is only valid if MREMAP_FIXED is specified */
294 if (flags & MREMAP_FIXED) {
295 if (new_addr & ~PAGE_MASK)
296 goto out;
297 if (!(flags & MREMAP_MAYMOVE))
298 goto out;
299
300 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
301 goto out;
302
303 /* Check if the location we're moving into overlaps the
304 * old location at all, and fail if it does.
305 */
306 if ((new_addr <= addr) && (new_addr+new_len) > addr)
307 goto out;
308
309 if ((addr <= new_addr) && (addr+old_len) > new_addr)
310 goto out;
311
312 ret = do_munmap(current->mm, new_addr, new_len);
313 if (ret)
314 goto out;
315 }
316
317 /*
318 * Always allow a shrinking remap: that just unmaps
319 * the unnecessary pages..
320 * do_munmap does all the needed commit accounting
321 */
322 if (old_len >= new_len) {
323 ret = do_munmap(current->mm, addr+new_len, old_len - new_len);
324 if (ret && old_len != new_len)
325 goto out;
326 ret = addr;
327 if (!(flags & MREMAP_FIXED) || (new_addr == addr))
328 goto out;
329 old_len = new_len;
330 }
331
332 /*
333 * Ok, we need to grow.. or relocate.
334 */
335 ret = -EFAULT;
336 vma = find_vma(current->mm, addr);
337 if (!vma || vma->vm_start > addr)
338 goto out;
339 if (is_vm_hugetlb_page(vma)) {
340 ret = -EINVAL;
341 goto out;
342 }
343 /* We can't remap across vm area boundaries */
344 if (old_len > vma->vm_end - addr)
345 goto out;
346 if (vma->vm_flags & VM_DONTEXPAND) {
347 if (new_len > old_len)
348 goto out;
349 }
350 if (vma->vm_flags & VM_LOCKED) {
351 unsigned long locked, lock_limit;
352 locked = current->mm->locked_vm << PAGE_SHIFT;
353 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
354 locked += new_len - old_len;
355 ret = -EAGAIN;
356 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
357 goto out;
358 }
akpm@osdl.org119f6572005-05-01 08:58:35 -0700359 if (!may_expand_vm(current->mm, (new_len - old_len) >> PAGE_SHIFT)) {
360 ret = -ENOMEM;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700361 goto out;
akpm@osdl.org119f6572005-05-01 08:58:35 -0700362 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700363
364 if (vma->vm_flags & VM_ACCOUNT) {
365 charged = (new_len - old_len) >> PAGE_SHIFT;
366 if (security_vm_enough_memory(charged))
367 goto out_nc;
368 }
369
370 /* old_len exactly to the end of the area..
371 * And we're not relocating the area.
372 */
373 if (old_len == vma->vm_end - addr &&
374 !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
375 (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
376 unsigned long max_addr = TASK_SIZE;
377 if (vma->vm_next)
378 max_addr = vma->vm_next->vm_start;
379 /* can we just expand the current mapping? */
380 if (max_addr - addr >= new_len) {
381 int pages = (new_len - old_len) >> PAGE_SHIFT;
382
383 vma_adjust(vma, vma->vm_start,
384 addr + new_len, vma->vm_pgoff, NULL);
385
386 current->mm->total_vm += pages;
387 __vm_stat_account(vma->vm_mm, vma->vm_flags,
388 vma->vm_file, pages);
389 if (vma->vm_flags & VM_LOCKED) {
390 current->mm->locked_vm += pages;
391 make_pages_present(addr + old_len,
392 addr + new_len);
393 }
394 ret = addr;
395 goto out;
396 }
397 }
398
399 /*
400 * We weren't able to just expand or shrink the area,
401 * we need to create a new one and move it..
402 */
403 ret = -ENOMEM;
404 if (flags & MREMAP_MAYMOVE) {
405 if (!(flags & MREMAP_FIXED)) {
406 unsigned long map_flags = 0;
407 if (vma->vm_flags & VM_MAYSHARE)
408 map_flags |= MAP_SHARED;
409
410 new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
411 vma->vm_pgoff, map_flags);
412 ret = new_addr;
413 if (new_addr & ~PAGE_MASK)
414 goto out;
415 }
416 ret = move_vma(vma, addr, old_len, new_len, new_addr);
417 }
418out:
419 if (ret & ~PAGE_MASK)
420 vm_unacct_memory(charged);
421out_nc:
422 return ret;
423}
424
425asmlinkage unsigned long sys_mremap(unsigned long addr,
426 unsigned long old_len, unsigned long new_len,
427 unsigned long flags, unsigned long new_addr)
428{
429 unsigned long ret;
430
431 down_write(&current->mm->mmap_sem);
432 ret = do_mremap(addr, old_len, new_len, flags, new_addr);
433 up_write(&current->mm->mmap_sem);
434 return ret;
435}