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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);
144 set_pte_at(mm, new_addr, dst, pte);
145 } else
146 error = -ENOMEM;
147 pte_unmap_nested(src);
148 }
149 if (dst)
150 pte_unmap(dst);
151 }
152 spin_unlock(&mm->page_table_lock);
153 if (mapping)
154 spin_unlock(&mapping->i_mmap_lock);
155 return error;
156}
157
158static unsigned long move_page_tables(struct vm_area_struct *vma,
159 unsigned long old_addr, struct vm_area_struct *new_vma,
160 unsigned long new_addr, unsigned long len)
161{
162 unsigned long offset;
163
164 flush_cache_range(vma, old_addr, old_addr + len);
165
166 /*
167 * This is not the clever way to do this, but we're taking the
168 * easy way out on the assumption that most remappings will be
169 * only a few pages.. This also makes error recovery easier.
170 */
171 for (offset = 0; offset < len; offset += PAGE_SIZE) {
172 if (move_one_page(vma, old_addr + offset,
173 new_vma, new_addr + offset) < 0)
174 break;
175 cond_resched();
176 }
177 return offset;
178}
179
180static unsigned long move_vma(struct vm_area_struct *vma,
181 unsigned long old_addr, unsigned long old_len,
182 unsigned long new_len, unsigned long new_addr)
183{
184 struct mm_struct *mm = vma->vm_mm;
185 struct vm_area_struct *new_vma;
186 unsigned long vm_flags = vma->vm_flags;
187 unsigned long new_pgoff;
188 unsigned long moved_len;
189 unsigned long excess = 0;
190 int split = 0;
191
192 /*
193 * We'd prefer to avoid failure later on in do_munmap:
194 * which may split one vma into three before unmapping.
195 */
196 if (mm->map_count >= sysctl_max_map_count - 3)
197 return -ENOMEM;
198
199 new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
200 new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
201 if (!new_vma)
202 return -ENOMEM;
203
204 moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
205 if (moved_len < old_len) {
206 /*
207 * On error, move entries back from new area to old,
208 * which will succeed since page tables still there,
209 * and then proceed to unmap new area instead of old.
210 */
211 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
212 vma = new_vma;
213 old_len = new_len;
214 old_addr = new_addr;
215 new_addr = -ENOMEM;
216 }
217
218 /* Conceal VM_ACCOUNT so old reservation is not undone */
219 if (vm_flags & VM_ACCOUNT) {
220 vma->vm_flags &= ~VM_ACCOUNT;
221 excess = vma->vm_end - vma->vm_start - old_len;
222 if (old_addr > vma->vm_start &&
223 old_addr + old_len < vma->vm_end)
224 split = 1;
225 }
226
227 if (do_munmap(mm, old_addr, old_len) < 0) {
228 /* OOM: unable to split vma, just get accounts right */
229 vm_unacct_memory(excess >> PAGE_SHIFT);
230 excess = 0;
231 }
232
233 /* Restore VM_ACCOUNT if one or two pieces of vma left */
234 if (excess) {
235 vma->vm_flags |= VM_ACCOUNT;
236 if (split)
237 vma->vm_next->vm_flags |= VM_ACCOUNT;
238 }
239
240 mm->total_vm += new_len >> PAGE_SHIFT;
241 __vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
242 if (vm_flags & VM_LOCKED) {
243 mm->locked_vm += new_len >> PAGE_SHIFT;
244 if (new_len > old_len)
245 make_pages_present(new_addr + old_len,
246 new_addr + new_len);
247 }
248
249 return new_addr;
250}
251
252/*
253 * Expand (or shrink) an existing mapping, potentially moving it at the
254 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
255 *
256 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
257 * This option implies MREMAP_MAYMOVE.
258 */
259unsigned long do_mremap(unsigned long addr,
260 unsigned long old_len, unsigned long new_len,
261 unsigned long flags, unsigned long new_addr)
262{
263 struct vm_area_struct *vma;
264 unsigned long ret = -EINVAL;
265 unsigned long charged = 0;
266
267 if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
268 goto out;
269
270 if (addr & ~PAGE_MASK)
271 goto out;
272
273 old_len = PAGE_ALIGN(old_len);
274 new_len = PAGE_ALIGN(new_len);
275
276 /*
277 * We allow a zero old-len as a special case
278 * for DOS-emu "duplicate shm area" thing. But
279 * a zero new-len is nonsensical.
280 */
281 if (!new_len)
282 goto out;
283
284 /* new_addr is only valid if MREMAP_FIXED is specified */
285 if (flags & MREMAP_FIXED) {
286 if (new_addr & ~PAGE_MASK)
287 goto out;
288 if (!(flags & MREMAP_MAYMOVE))
289 goto out;
290
291 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
292 goto out;
293
294 /* Check if the location we're moving into overlaps the
295 * old location at all, and fail if it does.
296 */
297 if ((new_addr <= addr) && (new_addr+new_len) > addr)
298 goto out;
299
300 if ((addr <= new_addr) && (addr+old_len) > new_addr)
301 goto out;
302
303 ret = do_munmap(current->mm, new_addr, new_len);
304 if (ret)
305 goto out;
306 }
307
308 /*
309 * Always allow a shrinking remap: that just unmaps
310 * the unnecessary pages..
311 * do_munmap does all the needed commit accounting
312 */
313 if (old_len >= new_len) {
314 ret = do_munmap(current->mm, addr+new_len, old_len - new_len);
315 if (ret && old_len != new_len)
316 goto out;
317 ret = addr;
318 if (!(flags & MREMAP_FIXED) || (new_addr == addr))
319 goto out;
320 old_len = new_len;
321 }
322
323 /*
324 * Ok, we need to grow.. or relocate.
325 */
326 ret = -EFAULT;
327 vma = find_vma(current->mm, addr);
328 if (!vma || vma->vm_start > addr)
329 goto out;
330 if (is_vm_hugetlb_page(vma)) {
331 ret = -EINVAL;
332 goto out;
333 }
334 /* We can't remap across vm area boundaries */
335 if (old_len > vma->vm_end - addr)
336 goto out;
337 if (vma->vm_flags & VM_DONTEXPAND) {
338 if (new_len > old_len)
339 goto out;
340 }
341 if (vma->vm_flags & VM_LOCKED) {
342 unsigned long locked, lock_limit;
343 locked = current->mm->locked_vm << PAGE_SHIFT;
344 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
345 locked += new_len - old_len;
346 ret = -EAGAIN;
347 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
348 goto out;
349 }
350 ret = -ENOMEM;
351 if ((current->mm->total_vm << PAGE_SHIFT) + (new_len - old_len)
352 > current->signal->rlim[RLIMIT_AS].rlim_cur)
353 goto out;
354
355 if (vma->vm_flags & VM_ACCOUNT) {
356 charged = (new_len - old_len) >> PAGE_SHIFT;
357 if (security_vm_enough_memory(charged))
358 goto out_nc;
359 }
360
361 /* old_len exactly to the end of the area..
362 * And we're not relocating the area.
363 */
364 if (old_len == vma->vm_end - addr &&
365 !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
366 (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
367 unsigned long max_addr = TASK_SIZE;
368 if (vma->vm_next)
369 max_addr = vma->vm_next->vm_start;
370 /* can we just expand the current mapping? */
371 if (max_addr - addr >= new_len) {
372 int pages = (new_len - old_len) >> PAGE_SHIFT;
373
374 vma_adjust(vma, vma->vm_start,
375 addr + new_len, vma->vm_pgoff, NULL);
376
377 current->mm->total_vm += pages;
378 __vm_stat_account(vma->vm_mm, vma->vm_flags,
379 vma->vm_file, pages);
380 if (vma->vm_flags & VM_LOCKED) {
381 current->mm->locked_vm += pages;
382 make_pages_present(addr + old_len,
383 addr + new_len);
384 }
385 ret = addr;
386 goto out;
387 }
388 }
389
390 /*
391 * We weren't able to just expand or shrink the area,
392 * we need to create a new one and move it..
393 */
394 ret = -ENOMEM;
395 if (flags & MREMAP_MAYMOVE) {
396 if (!(flags & MREMAP_FIXED)) {
397 unsigned long map_flags = 0;
398 if (vma->vm_flags & VM_MAYSHARE)
399 map_flags |= MAP_SHARED;
400
401 new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
402 vma->vm_pgoff, map_flags);
403 ret = new_addr;
404 if (new_addr & ~PAGE_MASK)
405 goto out;
406 }
407 ret = move_vma(vma, addr, old_len, new_len, new_addr);
408 }
409out:
410 if (ret & ~PAGE_MASK)
411 vm_unacct_memory(charged);
412out_nc:
413 return ret;
414}
415
416asmlinkage unsigned long sys_mremap(unsigned long addr,
417 unsigned long old_len, unsigned long new_len,
418 unsigned long flags, unsigned long new_addr)
419{
420 unsigned long ret;
421
422 down_write(&current->mm->mmap_sem);
423 ret = do_mremap(addr, old_len, new_len, flags, new_addr);
424 up_write(&current->mm->mmap_sem);
425 return ret;
426}