mm: cleanup: remove #ifdef CONFIG_MIGRATION
[linux-2.6.git] / mm / mprotect.c
1 /*
2  *  mm/mprotect.c
3  *
4  *  (C) Copyright 1994 Linus Torvalds
5  *  (C) Copyright 2002 Christoph Hellwig
6  *
7  *  Address space accounting code       <alan@lxorguk.ukuu.org.uk>
8  *  (C) Copyright 2002 Red Hat Inc, All Rights Reserved
9  */
10
11 #include <linux/mm.h>
12 #include <linux/hugetlb.h>
13 #include <linux/slab.h>
14 #include <linux/shm.h>
15 #include <linux/mman.h>
16 #include <linux/fs.h>
17 #include <linux/highmem.h>
18 #include <linux/security.h>
19 #include <linux/mempolicy.h>
20 #include <linux/personality.h>
21 #include <linux/syscalls.h>
22 #include <linux/swap.h>
23 #include <linux/swapops.h>
24 #include <linux/mmu_notifier.h>
25 #include <linux/migrate.h>
26 #include <asm/uaccess.h>
27 #include <asm/pgtable.h>
28 #include <asm/cacheflush.h>
29 #include <asm/tlbflush.h>
30
31 #ifndef pgprot_modify
32 static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
33 {
34         return newprot;
35 }
36 #endif
37
38 static void change_pte_range(struct mm_struct *mm, pmd_t *pmd,
39                 unsigned long addr, unsigned long end, pgprot_t newprot,
40                 int dirty_accountable)
41 {
42         pte_t *pte, oldpte;
43         spinlock_t *ptl;
44
45         pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
46         arch_enter_lazy_mmu_mode();
47         do {
48                 oldpte = *pte;
49                 if (pte_present(oldpte)) {
50                         pte_t ptent;
51
52                         ptent = ptep_modify_prot_start(mm, addr, pte);
53                         ptent = pte_modify(ptent, newprot);
54
55                         /*
56                          * Avoid taking write faults for pages we know to be
57                          * dirty.
58                          */
59                         if (dirty_accountable && pte_dirty(ptent))
60                                 ptent = pte_mkwrite(ptent);
61
62                         ptep_modify_prot_commit(mm, addr, pte, ptent);
63                 } else if (PAGE_MIGRATION && !pte_file(oldpte)) {
64                         swp_entry_t entry = pte_to_swp_entry(oldpte);
65
66                         if (is_write_migration_entry(entry)) {
67                                 /*
68                                  * A protection check is difficult so
69                                  * just be safe and disable write
70                                  */
71                                 make_migration_entry_read(&entry);
72                                 set_pte_at(mm, addr, pte,
73                                         swp_entry_to_pte(entry));
74                         }
75                 }
76         } while (pte++, addr += PAGE_SIZE, addr != end);
77         arch_leave_lazy_mmu_mode();
78         pte_unmap_unlock(pte - 1, ptl);
79 }
80
81 static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud,
82                 unsigned long addr, unsigned long end, pgprot_t newprot,
83                 int dirty_accountable)
84 {
85         pmd_t *pmd;
86         unsigned long next;
87
88         pmd = pmd_offset(pud, addr);
89         do {
90                 next = pmd_addr_end(addr, end);
91                 if (pmd_none_or_clear_bad(pmd))
92                         continue;
93                 change_pte_range(mm, pmd, addr, next, newprot, dirty_accountable);
94         } while (pmd++, addr = next, addr != end);
95 }
96
97 static inline void change_pud_range(struct mm_struct *mm, pgd_t *pgd,
98                 unsigned long addr, unsigned long end, pgprot_t newprot,
99                 int dirty_accountable)
100 {
101         pud_t *pud;
102         unsigned long next;
103
104         pud = pud_offset(pgd, addr);
105         do {
106                 next = pud_addr_end(addr, end);
107                 if (pud_none_or_clear_bad(pud))
108                         continue;
109                 change_pmd_range(mm, pud, addr, next, newprot, dirty_accountable);
110         } while (pud++, addr = next, addr != end);
111 }
112
113 static void change_protection(struct vm_area_struct *vma,
114                 unsigned long addr, unsigned long end, pgprot_t newprot,
115                 int dirty_accountable)
116 {
117         struct mm_struct *mm = vma->vm_mm;
118         pgd_t *pgd;
119         unsigned long next;
120         unsigned long start = addr;
121
122         BUG_ON(addr >= end);
123         pgd = pgd_offset(mm, addr);
124         flush_cache_range(vma, addr, end);
125         do {
126                 next = pgd_addr_end(addr, end);
127                 if (pgd_none_or_clear_bad(pgd))
128                         continue;
129                 change_pud_range(mm, pgd, addr, next, newprot, dirty_accountable);
130         } while (pgd++, addr = next, addr != end);
131         flush_tlb_range(vma, start, end);
132 }
133
134 int
135 mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
136         unsigned long start, unsigned long end, unsigned long newflags)
137 {
138         struct mm_struct *mm = vma->vm_mm;
139         unsigned long oldflags = vma->vm_flags;
140         long nrpages = (end - start) >> PAGE_SHIFT;
141         unsigned long charged = 0;
142         pgoff_t pgoff;
143         int error;
144         int dirty_accountable = 0;
145
146         if (newflags == oldflags) {
147                 *pprev = vma;
148                 return 0;
149         }
150
151         /*
152          * If we make a private mapping writable we increase our commit;
153          * but (without finer accounting) cannot reduce our commit if we
154          * make it unwritable again.
155          */
156         if (newflags & VM_WRITE) {
157                 if (!(oldflags & (VM_ACCOUNT|VM_WRITE|
158                                                 VM_SHARED|VM_NORESERVE))) {
159                         charged = nrpages;
160                         if (security_vm_enough_memory(charged))
161                                 return -ENOMEM;
162                         newflags |= VM_ACCOUNT;
163                 }
164         }
165
166         /*
167          * First try to merge with previous and/or next vma.
168          */
169         pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
170         *pprev = vma_merge(mm, *pprev, start, end, newflags,
171                         vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));
172         if (*pprev) {
173                 vma = *pprev;
174                 goto success;
175         }
176
177         *pprev = vma;
178
179         if (start != vma->vm_start) {
180                 error = split_vma(mm, vma, start, 1);
181                 if (error)
182                         goto fail;
183         }
184
185         if (end != vma->vm_end) {
186                 error = split_vma(mm, vma, end, 0);
187                 if (error)
188                         goto fail;
189         }
190
191 success:
192         /*
193          * vm_flags and vm_page_prot are protected by the mmap_sem
194          * held in write mode.
195          */
196         vma->vm_flags = newflags;
197         vma->vm_page_prot = pgprot_modify(vma->vm_page_prot,
198                                           vm_get_page_prot(newflags));
199
200         if (vma_wants_writenotify(vma)) {
201                 vma->vm_page_prot = vm_get_page_prot(newflags & ~VM_SHARED);
202                 dirty_accountable = 1;
203         }
204
205         mmu_notifier_invalidate_range_start(mm, start, end);
206         if (is_vm_hugetlb_page(vma))
207                 hugetlb_change_protection(vma, start, end, vma->vm_page_prot);
208         else
209                 change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable);
210         mmu_notifier_invalidate_range_end(mm, start, end);
211         vm_stat_account(mm, oldflags, vma->vm_file, -nrpages);
212         vm_stat_account(mm, newflags, vma->vm_file, nrpages);
213         return 0;
214
215 fail:
216         vm_unacct_memory(charged);
217         return error;
218 }
219
220 asmlinkage long
221 sys_mprotect(unsigned long start, size_t len, unsigned long prot)
222 {
223         unsigned long vm_flags, nstart, end, tmp, reqprot;
224         struct vm_area_struct *vma, *prev;
225         int error = -EINVAL;
226         const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP);
227         prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);
228         if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */
229                 return -EINVAL;
230
231         if (start & ~PAGE_MASK)
232                 return -EINVAL;
233         if (!len)
234                 return 0;
235         len = PAGE_ALIGN(len);
236         end = start + len;
237         if (end <= start)
238                 return -ENOMEM;
239         if (!arch_validate_prot(prot))
240                 return -EINVAL;
241
242         reqprot = prot;
243         /*
244          * Does the application expect PROT_READ to imply PROT_EXEC:
245          */
246         if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
247                 prot |= PROT_EXEC;
248
249         vm_flags = calc_vm_prot_bits(prot);
250
251         down_write(&current->mm->mmap_sem);
252
253         vma = find_vma_prev(current->mm, start, &prev);
254         error = -ENOMEM;
255         if (!vma)
256                 goto out;
257         if (unlikely(grows & PROT_GROWSDOWN)) {
258                 if (vma->vm_start >= end)
259                         goto out;
260                 start = vma->vm_start;
261                 error = -EINVAL;
262                 if (!(vma->vm_flags & VM_GROWSDOWN))
263                         goto out;
264         }
265         else {
266                 if (vma->vm_start > start)
267                         goto out;
268                 if (unlikely(grows & PROT_GROWSUP)) {
269                         end = vma->vm_end;
270                         error = -EINVAL;
271                         if (!(vma->vm_flags & VM_GROWSUP))
272                                 goto out;
273                 }
274         }
275         if (start > vma->vm_start)
276                 prev = vma;
277
278         for (nstart = start ; ; ) {
279                 unsigned long newflags;
280
281                 /* Here we know that  vma->vm_start <= nstart < vma->vm_end. */
282
283                 newflags = vm_flags | (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC));
284
285                 /* newflags >> 4 shift VM_MAY% in place of VM_% */
286                 if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) {
287                         error = -EACCES;
288                         goto out;
289                 }
290
291                 error = security_file_mprotect(vma, reqprot, prot);
292                 if (error)
293                         goto out;
294
295                 tmp = vma->vm_end;
296                 if (tmp > end)
297                         tmp = end;
298                 error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
299                 if (error)
300                         goto out;
301                 nstart = tmp;
302
303                 if (nstart < prev->vm_end)
304                         nstart = prev->vm_end;
305                 if (nstart >= end)
306                         goto out;
307
308                 vma = prev->vm_next;
309                 if (!vma || vma->vm_start != nstart) {
310                         error = -ENOMEM;
311                         goto out;
312                 }
313         }
314 out:
315         up_write(&current->mm->mmap_sem);
316         return error;
317 }