knfsd: nfsd: factor out code from show_expflags
[linux-2.6/mini2440.git] / mm / mprotect.c
blob3b8f3c0c63f3b948cda9edca535d7aaa65b4a38b
1 /*
2 * mm/mprotect.c
4 * (C) Copyright 1994 Linus Torvalds
5 * (C) Copyright 2002 Christoph Hellwig
7 * Address space accounting code <alan@redhat.com>
8 * (C) Copyright 2002 Red Hat Inc, All Rights Reserved
9 */
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 <asm/uaccess.h>
25 #include <asm/pgtable.h>
26 #include <asm/cacheflush.h>
27 #include <asm/tlbflush.h>
29 static void change_pte_range(struct mm_struct *mm, pmd_t *pmd,
30 unsigned long addr, unsigned long end, pgprot_t newprot,
31 int dirty_accountable)
33 pte_t *pte, oldpte;
34 spinlock_t *ptl;
36 pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
37 arch_enter_lazy_mmu_mode();
38 do {
39 oldpte = *pte;
40 if (pte_present(oldpte)) {
41 pte_t ptent;
43 /* Avoid an SMP race with hardware updated dirty/clean
44 * bits by wiping the pte and then setting the new pte
45 * into place.
47 ptent = ptep_get_and_clear(mm, addr, pte);
48 ptent = pte_modify(ptent, newprot);
50 * Avoid taking write faults for pages we know to be
51 * dirty.
53 if (dirty_accountable && pte_dirty(ptent))
54 ptent = pte_mkwrite(ptent);
55 set_pte_at(mm, addr, pte, ptent);
56 lazy_mmu_prot_update(ptent);
57 #ifdef CONFIG_MIGRATION
58 } else if (!pte_file(oldpte)) {
59 swp_entry_t entry = pte_to_swp_entry(oldpte);
61 if (is_write_migration_entry(entry)) {
63 * A protection check is difficult so
64 * just be safe and disable write
66 make_migration_entry_read(&entry);
67 set_pte_at(mm, addr, pte,
68 swp_entry_to_pte(entry));
70 #endif
73 } while (pte++, addr += PAGE_SIZE, addr != end);
74 arch_leave_lazy_mmu_mode();
75 pte_unmap_unlock(pte - 1, ptl);
78 static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud,
79 unsigned long addr, unsigned long end, pgprot_t newprot,
80 int dirty_accountable)
82 pmd_t *pmd;
83 unsigned long next;
85 pmd = pmd_offset(pud, addr);
86 do {
87 next = pmd_addr_end(addr, end);
88 if (pmd_none_or_clear_bad(pmd))
89 continue;
90 change_pte_range(mm, pmd, addr, next, newprot, dirty_accountable);
91 } while (pmd++, addr = next, addr != end);
94 static inline void change_pud_range(struct mm_struct *mm, pgd_t *pgd,
95 unsigned long addr, unsigned long end, pgprot_t newprot,
96 int dirty_accountable)
98 pud_t *pud;
99 unsigned long next;
101 pud = pud_offset(pgd, addr);
102 do {
103 next = pud_addr_end(addr, end);
104 if (pud_none_or_clear_bad(pud))
105 continue;
106 change_pmd_range(mm, pud, addr, next, newprot, dirty_accountable);
107 } while (pud++, addr = next, addr != end);
110 static void change_protection(struct vm_area_struct *vma,
111 unsigned long addr, unsigned long end, pgprot_t newprot,
112 int dirty_accountable)
114 struct mm_struct *mm = vma->vm_mm;
115 pgd_t *pgd;
116 unsigned long next;
117 unsigned long start = addr;
119 BUG_ON(addr >= end);
120 pgd = pgd_offset(mm, addr);
121 flush_cache_range(vma, addr, end);
122 do {
123 next = pgd_addr_end(addr, end);
124 if (pgd_none_or_clear_bad(pgd))
125 continue;
126 change_pud_range(mm, pgd, addr, next, newprot, dirty_accountable);
127 } while (pgd++, addr = next, addr != end);
128 flush_tlb_range(vma, start, end);
131 static int
132 mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
133 unsigned long start, unsigned long end, unsigned long newflags)
135 struct mm_struct *mm = vma->vm_mm;
136 unsigned long oldflags = vma->vm_flags;
137 long nrpages = (end - start) >> PAGE_SHIFT;
138 unsigned long charged = 0;
139 pgoff_t pgoff;
140 int error;
141 int dirty_accountable = 0;
143 if (newflags == oldflags) {
144 *pprev = vma;
145 return 0;
149 * If we make a private mapping writable we increase our commit;
150 * but (without finer accounting) cannot reduce our commit if we
151 * make it unwritable again.
153 * FIXME? We haven't defined a VM_NORESERVE flag, so mprotecting
154 * a MAP_NORESERVE private mapping to writable will now reserve.
156 if (newflags & VM_WRITE) {
157 if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_SHARED))) {
158 charged = nrpages;
159 if (security_vm_enough_memory(charged))
160 return -ENOMEM;
161 newflags |= VM_ACCOUNT;
166 * First try to merge with previous and/or next vma.
168 pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
169 *pprev = vma_merge(mm, *pprev, start, end, newflags,
170 vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));
171 if (*pprev) {
172 vma = *pprev;
173 goto success;
176 *pprev = vma;
178 if (start != vma->vm_start) {
179 error = split_vma(mm, vma, start, 1);
180 if (error)
181 goto fail;
184 if (end != vma->vm_end) {
185 error = split_vma(mm, vma, end, 0);
186 if (error)
187 goto fail;
190 success:
192 * vm_flags and vm_page_prot are protected by the mmap_sem
193 * held in write mode.
195 vma->vm_flags = newflags;
196 vma->vm_page_prot = protection_map[newflags &
197 (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)];
198 if (vma_wants_writenotify(vma)) {
199 vma->vm_page_prot = protection_map[newflags &
200 (VM_READ|VM_WRITE|VM_EXEC)];
201 dirty_accountable = 1;
204 if (is_vm_hugetlb_page(vma))
205 hugetlb_change_protection(vma, start, end, vma->vm_page_prot);
206 else
207 change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable);
208 vm_stat_account(mm, oldflags, vma->vm_file, -nrpages);
209 vm_stat_account(mm, newflags, vma->vm_file, nrpages);
210 return 0;
212 fail:
213 vm_unacct_memory(charged);
214 return error;
217 asmlinkage long
218 sys_mprotect(unsigned long start, size_t len, unsigned long prot)
220 unsigned long vm_flags, nstart, end, tmp, reqprot;
221 struct vm_area_struct *vma, *prev;
222 int error = -EINVAL;
223 const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP);
224 prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);
225 if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */
226 return -EINVAL;
228 if (start & ~PAGE_MASK)
229 return -EINVAL;
230 if (!len)
231 return 0;
232 len = PAGE_ALIGN(len);
233 end = start + len;
234 if (end <= start)
235 return -ENOMEM;
236 if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM))
237 return -EINVAL;
239 reqprot = prot;
241 * Does the application expect PROT_READ to imply PROT_EXEC:
243 if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
244 prot |= PROT_EXEC;
246 vm_flags = calc_vm_prot_bits(prot);
248 down_write(&current->mm->mmap_sem);
250 vma = find_vma_prev(current->mm, start, &prev);
251 error = -ENOMEM;
252 if (!vma)
253 goto out;
254 if (unlikely(grows & PROT_GROWSDOWN)) {
255 if (vma->vm_start >= end)
256 goto out;
257 start = vma->vm_start;
258 error = -EINVAL;
259 if (!(vma->vm_flags & VM_GROWSDOWN))
260 goto out;
262 else {
263 if (vma->vm_start > start)
264 goto out;
265 if (unlikely(grows & PROT_GROWSUP)) {
266 end = vma->vm_end;
267 error = -EINVAL;
268 if (!(vma->vm_flags & VM_GROWSUP))
269 goto out;
272 if (start > vma->vm_start)
273 prev = vma;
275 for (nstart = start ; ; ) {
276 unsigned long newflags;
278 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
280 newflags = vm_flags | (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC));
282 /* newflags >> 4 shift VM_MAY% in place of VM_% */
283 if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) {
284 error = -EACCES;
285 goto out;
288 error = security_file_mprotect(vma, reqprot, prot);
289 if (error)
290 goto out;
292 tmp = vma->vm_end;
293 if (tmp > end)
294 tmp = end;
295 error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
296 if (error)
297 goto out;
298 nstart = tmp;
300 if (nstart < prev->vm_end)
301 nstart = prev->vm_end;
302 if (nstart >= end)
303 goto out;
305 vma = prev->vm_next;
306 if (!vma || vma->vm_start != nstart) {
307 error = -ENOMEM;
308 goto out;
311 out:
312 up_write(&current->mm->mmap_sem);
313 return error;