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1 | /* |
2 | * linux/mm/fremap.c |
3 | * |
4 | * Explicit pagetable population and nonlinear (random) mappings support. |
5 | * |
6 | * started by Ingo Molnar, Copyright (C) 2002, 2003 |
7 | */ |
8 | #include <linux/export.h> |
9 | #include <linux/backing-dev.h> |
10 | #include <linux/mm.h> |
11 | #include <linux/swap.h> |
12 | #include <linux/file.h> |
13 | #include <linux/mman.h> |
14 | #include <linux/pagemap.h> |
15 | #include <linux/swapops.h> |
16 | #include <linux/rmap.h> |
17 | #include <linux/syscalls.h> |
18 | #include <linux/mmu_notifier.h> |
19 | |
20 | #include <asm/mmu_context.h> |
21 | #include <asm/cacheflush.h> |
22 | #include <asm/tlbflush.h> |
23 | |
24 | #include "internal.h" |
25 | |
26 | static void zap_pte(struct mm_struct *mm, struct vm_area_struct *vma, |
27 | unsigned long addr, pte_t *ptep) |
28 | { |
29 | pte_t pte = *ptep; |
30 | |
31 | if (pte_present(pte)) { |
32 | struct page *page; |
33 | |
34 | flush_cache_page(vma, addr, pte_pfn(pte)); |
35 | pte = ptep_clear_flush(vma, addr, ptep); |
36 | page = vm_normal_page(vma, addr, pte); |
37 | if (page) { |
38 | if (pte_dirty(pte)) |
39 | set_page_dirty(page); |
40 | page_remove_rmap(page); |
41 | page_cache_release(page); |
42 | update_hiwater_rss(mm); |
43 | dec_mm_counter(mm, MM_FILEPAGES); |
44 | } |
45 | } else { |
46 | if (!pte_file(pte)) |
47 | free_swap_and_cache(pte_to_swp_entry(pte)); |
48 | pte_clear_not_present_full(mm, addr, ptep, 0); |
49 | } |
50 | } |
51 | |
52 | /* |
53 | * Install a file pte to a given virtual memory address, release any |
54 | * previously existing mapping. |
55 | */ |
56 | static int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma, |
57 | unsigned long addr, unsigned long pgoff, pgprot_t prot) |
58 | { |
59 | int err = -ENOMEM; |
60 | pte_t *pte, ptfile; |
61 | spinlock_t *ptl; |
62 | |
63 | pte = get_locked_pte(mm, addr, &ptl); |
64 | if (!pte) |
65 | goto out; |
66 | |
67 | ptfile = pgoff_to_pte(pgoff); |
68 | |
69 | if (!pte_none(*pte)) { |
70 | if (pte_present(*pte) && pte_soft_dirty(*pte)) |
71 | pte_file_mksoft_dirty(ptfile); |
72 | zap_pte(mm, vma, addr, pte); |
73 | } |
74 | |
75 | set_pte_at(mm, addr, pte, ptfile); |
76 | /* |
77 | * We don't need to run update_mmu_cache() here because the "file pte" |
78 | * being installed by install_file_pte() is not a real pte - it's a |
79 | * non-present entry (like a swap entry), noting what file offset should |
80 | * be mapped there when there's a fault (in a non-linear vma where |
81 | * that's not obvious). |
82 | */ |
83 | pte_unmap_unlock(pte, ptl); |
84 | err = 0; |
85 | out: |
86 | return err; |
87 | } |
88 | |
89 | int generic_file_remap_pages(struct vm_area_struct *vma, unsigned long addr, |
90 | unsigned long size, pgoff_t pgoff) |
91 | { |
92 | struct mm_struct *mm = vma->vm_mm; |
93 | int err; |
94 | |
95 | do { |
96 | err = install_file_pte(mm, vma, addr, pgoff, vma->vm_page_prot); |
97 | if (err) |
98 | return err; |
99 | |
100 | size -= PAGE_SIZE; |
101 | addr += PAGE_SIZE; |
102 | pgoff++; |
103 | } while (size); |
104 | |
105 | return 0; |
106 | } |
107 | EXPORT_SYMBOL(generic_file_remap_pages); |
108 | |
109 | /** |
110 | * sys_remap_file_pages - remap arbitrary pages of an existing VM_SHARED vma |
111 | * @start: start of the remapped virtual memory range |
112 | * @size: size of the remapped virtual memory range |
113 | * @prot: new protection bits of the range (see NOTE) |
114 | * @pgoff: to-be-mapped page of the backing store file |
115 | * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO. |
116 | * |
117 | * sys_remap_file_pages remaps arbitrary pages of an existing VM_SHARED vma |
118 | * (shared backing store file). |
119 | * |
120 | * This syscall works purely via pagetables, so it's the most efficient |
121 | * way to map the same (large) file into a given virtual window. Unlike |
122 | * mmap()/mremap() it does not create any new vmas. The new mappings are |
123 | * also safe across swapout. |
124 | * |
125 | * NOTE: the @prot parameter right now is ignored (but must be zero), |
126 | * and the vma's default protection is used. Arbitrary protections |
127 | * might be implemented in the future. |
128 | */ |
129 | SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size, |
130 | unsigned long, prot, unsigned long, pgoff, unsigned long, flags) |
131 | { |
132 | struct mm_struct *mm = current->mm; |
133 | struct address_space *mapping; |
134 | struct vm_area_struct *vma; |
135 | int err = -EINVAL; |
136 | int has_write_lock = 0; |
137 | vm_flags_t vm_flags = 0; |
138 | |
139 | if (prot) |
140 | return err; |
141 | /* |
142 | * Sanitize the syscall parameters: |
143 | */ |
144 | start = start & PAGE_MASK; |
145 | size = size & PAGE_MASK; |
146 | |
147 | /* Does the address range wrap, or is the span zero-sized? */ |
148 | if (start + size <= start) |
149 | return err; |
150 | |
151 | /* Does pgoff wrap? */ |
152 | if (pgoff + (size >> PAGE_SHIFT) < pgoff) |
153 | return err; |
154 | |
155 | /* Can we represent this offset inside this architecture's pte's? */ |
156 | #if PTE_FILE_MAX_BITS < BITS_PER_LONG |
157 | if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS)) |
158 | return err; |
159 | #endif |
160 | |
161 | /* We need down_write() to change vma->vm_flags. */ |
162 | down_read(&mm->mmap_sem); |
163 | retry: |
164 | vma = find_vma(mm, start); |
165 | |
166 | /* |
167 | * Make sure the vma is shared, that it supports prefaulting, |
168 | * and that the remapped range is valid and fully within |
169 | * the single existing vma. |
170 | */ |
171 | if (!vma || !(vma->vm_flags & VM_SHARED)) |
172 | goto out; |
173 | |
174 | if (!vma->vm_ops || !vma->vm_ops->remap_pages) |
175 | goto out; |
176 | |
177 | if (start < vma->vm_start || start + size > vma->vm_end) |
178 | goto out; |
179 | |
180 | /* Must set VM_NONLINEAR before any pages are populated. */ |
181 | if (!(vma->vm_flags & VM_NONLINEAR)) { |
182 | /* |
183 | * vm_private_data is used as a swapout cursor |
184 | * in a VM_NONLINEAR vma. |
185 | */ |
186 | if (vma->vm_private_data) |
187 | goto out; |
188 | |
189 | /* Don't need a nonlinear mapping, exit success */ |
190 | if (pgoff == linear_page_index(vma, start)) { |
191 | err = 0; |
192 | goto out; |
193 | } |
194 | |
195 | if (!has_write_lock) { |
196 | get_write_lock: |
197 | up_read(&mm->mmap_sem); |
198 | down_write(&mm->mmap_sem); |
199 | has_write_lock = 1; |
200 | goto retry; |
201 | } |
202 | mapping = vma->vm_file->f_mapping; |
203 | /* |
204 | * page_mkclean doesn't work on nonlinear vmas, so if |
205 | * dirty pages need to be accounted, emulate with linear |
206 | * vmas. |
207 | */ |
208 | if (mapping_cap_account_dirty(mapping)) { |
209 | unsigned long addr; |
210 | struct file *file = get_file(vma->vm_file); |
211 | |
212 | addr = mmap_region(file, start, size, |
213 | vma->vm_flags, pgoff); |
214 | fput(file); |
215 | if (IS_ERR_VALUE(addr)) { |
216 | err = addr; |
217 | } else { |
218 | BUG_ON(addr != start); |
219 | err = 0; |
220 | } |
221 | goto out; |
222 | } |
223 | mutex_lock(&mapping->i_mmap_mutex); |
224 | flush_dcache_mmap_lock(mapping); |
225 | vma->vm_flags |= VM_NONLINEAR; |
226 | vma_interval_tree_remove(vma, &mapping->i_mmap); |
227 | vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear); |
228 | flush_dcache_mmap_unlock(mapping); |
229 | mutex_unlock(&mapping->i_mmap_mutex); |
230 | } |
231 | |
232 | if (vma->vm_flags & VM_LOCKED) { |
233 | /* |
234 | * drop PG_Mlocked flag for over-mapped range |
235 | */ |
236 | if (!has_write_lock) |
237 | goto get_write_lock; |
238 | vm_flags = vma->vm_flags; |
239 | munlock_vma_pages_range(vma, start, start + size); |
240 | vma->vm_flags = vm_flags; |
241 | } |
242 | |
243 | mmu_notifier_invalidate_range_start(mm, start, start + size); |
244 | err = vma->vm_ops->remap_pages(vma, start, size, pgoff); |
245 | mmu_notifier_invalidate_range_end(mm, start, start + size); |
246 | |
247 | /* |
248 | * We can't clear VM_NONLINEAR because we'd have to do |
249 | * it after ->populate completes, and that would prevent |
250 | * downgrading the lock. (Locks can't be upgraded). |
251 | */ |
252 | |
253 | out: |
254 | if (vma) |
255 | vm_flags = vma->vm_flags; |
256 | if (likely(!has_write_lock)) |
257 | up_read(&mm->mmap_sem); |
258 | else |
259 | up_write(&mm->mmap_sem); |
260 | if (!err && ((vm_flags & VM_LOCKED) || !(flags & MAP_NONBLOCK))) |
261 | mm_populate(start, size); |
262 | |
263 | return err; |
264 | } |
265 |
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