[PATCH] RLIMIT_AS checking fix
[linux-2.6.git] / mm / mremap.c
1 /*
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
25 static 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         }
49 end:
50         return pte;
51 }
52
53 static 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
74 static 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
92 static int
93 move_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
158 static 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
180 static 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  */
259 unsigned 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         if (!may_expand_vm(current->mm, (new_len - old_len) >> PAGE_SHIFT)) {
351                 ret = -ENOMEM;
352                 goto out;
353         }
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         }
409 out:
410         if (ret & ~PAGE_MASK)
411                 vm_unacct_memory(charged);
412 out_nc:
413         return ret;
414 }
415
416 asmlinkage 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 }