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1 | /* | |
2 | * linux/mm/filemap_xip.c | |
3 | * | |
4 | * Copyright (C) 2005 IBM Corporation | |
5 | * Author: Carsten Otte <cotte@de.ibm.com> | |
6 | * | |
7 | * derived from linux/mm/filemap.c - Copyright (C) Linus Torvalds | |
8 | * | |
9 | */ | |
10 | ||
11 | #include <linux/fs.h> | |
12 | #include <linux/pagemap.h> | |
13 | #include <linux/module.h> | |
14 | #include <linux/uio.h> | |
15 | #include <linux/rmap.h> | |
16 | #include <asm/tlbflush.h> | |
17 | #include "filemap.h" | |
18 | ||
19 | /* | |
20 | * We do use our own empty page to avoid interference with other users | |
21 | * of ZERO_PAGE(), such as /dev/zero | |
22 | */ | |
23 | static struct page *__xip_sparse_page; | |
24 | ||
25 | static struct page *xip_sparse_page(void) | |
26 | { | |
27 | if (!__xip_sparse_page) { | |
28 | unsigned long zeroes = get_zeroed_page(GFP_HIGHUSER); | |
29 | if (zeroes) { | |
30 | static DEFINE_SPINLOCK(xip_alloc_lock); | |
31 | spin_lock(&xip_alloc_lock); | |
32 | if (!__xip_sparse_page) | |
33 | __xip_sparse_page = virt_to_page(zeroes); | |
34 | else | |
35 | free_page(zeroes); | |
36 | spin_unlock(&xip_alloc_lock); | |
37 | } | |
38 | } | |
39 | return __xip_sparse_page; | |
40 | } | |
41 | ||
42 | /* | |
43 | * This is a file read routine for execute in place files, and uses | |
44 | * the mapping->a_ops->get_xip_page() function for the actual low-level | |
45 | * stuff. | |
46 | * | |
47 | * Note the struct file* is not used at all. It may be NULL. | |
48 | */ | |
49 | static void | |
50 | do_xip_mapping_read(struct address_space *mapping, | |
51 | struct file_ra_state *_ra, | |
52 | struct file *filp, | |
53 | loff_t *ppos, | |
54 | read_descriptor_t *desc, | |
55 | read_actor_t actor) | |
56 | { | |
57 | struct inode *inode = mapping->host; | |
58 | unsigned long index, end_index, offset; | |
59 | loff_t isize; | |
60 | ||
61 | BUG_ON(!mapping->a_ops->get_xip_page); | |
62 | ||
63 | index = *ppos >> PAGE_CACHE_SHIFT; | |
64 | offset = *ppos & ~PAGE_CACHE_MASK; | |
65 | ||
66 | isize = i_size_read(inode); | |
67 | if (!isize) | |
68 | goto out; | |
69 | ||
70 | end_index = (isize - 1) >> PAGE_CACHE_SHIFT; | |
71 | for (;;) { | |
72 | struct page *page; | |
73 | unsigned long nr, ret; | |
74 | ||
75 | /* nr is the maximum number of bytes to copy from this page */ | |
76 | nr = PAGE_CACHE_SIZE; | |
77 | if (index >= end_index) { | |
78 | if (index > end_index) | |
79 | goto out; | |
80 | nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1; | |
81 | if (nr <= offset) { | |
82 | goto out; | |
83 | } | |
84 | } | |
85 | nr = nr - offset; | |
86 | ||
87 | page = mapping->a_ops->get_xip_page(mapping, | |
88 | index*(PAGE_SIZE/512), 0); | |
89 | if (!page) | |
90 | goto no_xip_page; | |
91 | if (unlikely(IS_ERR(page))) { | |
92 | if (PTR_ERR(page) == -ENODATA) { | |
93 | /* sparse */ | |
94 | page = ZERO_PAGE(0); | |
95 | } else { | |
96 | desc->error = PTR_ERR(page); | |
97 | goto out; | |
98 | } | |
99 | } | |
100 | ||
101 | /* If users can be writing to this page using arbitrary | |
102 | * virtual addresses, take care about potential aliasing | |
103 | * before reading the page on the kernel side. | |
104 | */ | |
105 | if (mapping_writably_mapped(mapping)) | |
106 | flush_dcache_page(page); | |
107 | ||
108 | /* | |
109 | * Ok, we have the page, so now we can copy it to user space... | |
110 | * | |
111 | * The actor routine returns how many bytes were actually used.. | |
112 | * NOTE! This may not be the same as how much of a user buffer | |
113 | * we filled up (we may be padding etc), so we can only update | |
114 | * "pos" here (the actor routine has to update the user buffer | |
115 | * pointers and the remaining count). | |
116 | */ | |
117 | ret = actor(desc, page, offset, nr); | |
118 | offset += ret; | |
119 | index += offset >> PAGE_CACHE_SHIFT; | |
120 | offset &= ~PAGE_CACHE_MASK; | |
121 | ||
122 | if (ret == nr && desc->count) | |
123 | continue; | |
124 | goto out; | |
125 | ||
126 | no_xip_page: | |
127 | /* Did not get the page. Report it */ | |
128 | desc->error = -EIO; | |
129 | goto out; | |
130 | } | |
131 | ||
132 | out: | |
133 | *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset; | |
134 | if (filp) | |
135 | file_accessed(filp); | |
136 | } | |
137 | ||
138 | ssize_t | |
139 | xip_file_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos) | |
140 | { | |
141 | read_descriptor_t desc; | |
142 | ||
143 | if (!access_ok(VERIFY_WRITE, buf, len)) | |
144 | return -EFAULT; | |
145 | ||
146 | desc.written = 0; | |
147 | desc.arg.buf = buf; | |
148 | desc.count = len; | |
149 | desc.error = 0; | |
150 | ||
151 | do_xip_mapping_read(filp->f_mapping, &filp->f_ra, filp, | |
152 | ppos, &desc, file_read_actor); | |
153 | ||
154 | if (desc.written) | |
155 | return desc.written; | |
156 | else | |
157 | return desc.error; | |
158 | } | |
159 | EXPORT_SYMBOL_GPL(xip_file_read); | |
160 | ||
161 | ssize_t | |
162 | xip_file_sendfile(struct file *in_file, loff_t *ppos, | |
163 | size_t count, read_actor_t actor, void *target) | |
164 | { | |
165 | read_descriptor_t desc; | |
166 | ||
167 | if (!count) | |
168 | return 0; | |
169 | ||
170 | desc.written = 0; | |
171 | desc.count = count; | |
172 | desc.arg.data = target; | |
173 | desc.error = 0; | |
174 | ||
175 | do_xip_mapping_read(in_file->f_mapping, &in_file->f_ra, in_file, | |
176 | ppos, &desc, actor); | |
177 | if (desc.written) | |
178 | return desc.written; | |
179 | return desc.error; | |
180 | } | |
181 | EXPORT_SYMBOL_GPL(xip_file_sendfile); | |
182 | ||
183 | /* | |
184 | * __xip_unmap is invoked from xip_unmap and | |
185 | * xip_write | |
186 | * | |
187 | * This function walks all vmas of the address_space and unmaps the | |
188 | * __xip_sparse_page when found at pgoff. | |
189 | */ | |
190 | static void | |
191 | __xip_unmap (struct address_space * mapping, | |
192 | unsigned long pgoff) | |
193 | { | |
194 | struct vm_area_struct *vma; | |
195 | struct mm_struct *mm; | |
196 | struct prio_tree_iter iter; | |
197 | unsigned long address; | |
198 | pte_t *pte; | |
199 | pte_t pteval; | |
200 | spinlock_t *ptl; | |
201 | struct page *page; | |
202 | ||
203 | page = __xip_sparse_page; | |
204 | if (!page) | |
205 | return; | |
206 | ||
207 | spin_lock(&mapping->i_mmap_lock); | |
208 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { | |
209 | mm = vma->vm_mm; | |
210 | address = vma->vm_start + | |
211 | ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); | |
212 | BUG_ON(address < vma->vm_start || address >= vma->vm_end); | |
213 | pte = page_check_address(page, mm, address, &ptl); | |
214 | if (pte) { | |
215 | /* Nuke the page table entry. */ | |
216 | flush_cache_page(vma, address, pte_pfn(*pte)); | |
217 | pteval = ptep_clear_flush(vma, address, pte); | |
218 | page_remove_rmap(page, vma); | |
219 | dec_mm_counter(mm, file_rss); | |
220 | BUG_ON(pte_dirty(pteval)); | |
221 | pte_unmap_unlock(pte, ptl); | |
222 | page_cache_release(page); | |
223 | } | |
224 | } | |
225 | spin_unlock(&mapping->i_mmap_lock); | |
226 | } | |
227 | ||
228 | /* | |
229 | * xip_nopage() is invoked via the vma operations vector for a | |
230 | * mapped memory region to read in file data during a page fault. | |
231 | * | |
232 | * This function is derived from filemap_nopage, but used for execute in place | |
233 | */ | |
234 | static struct page * | |
235 | xip_file_nopage(struct vm_area_struct * area, | |
236 | unsigned long address, | |
237 | int *type) | |
238 | { | |
239 | struct file *file = area->vm_file; | |
240 | struct address_space *mapping = file->f_mapping; | |
241 | struct inode *inode = mapping->host; | |
242 | struct page *page; | |
243 | unsigned long size, pgoff, endoff; | |
244 | ||
245 | pgoff = ((address - area->vm_start) >> PAGE_CACHE_SHIFT) | |
246 | + area->vm_pgoff; | |
247 | endoff = ((area->vm_end - area->vm_start) >> PAGE_CACHE_SHIFT) | |
248 | + area->vm_pgoff; | |
249 | ||
250 | size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; | |
251 | if (pgoff >= size) | |
252 | return NOPAGE_SIGBUS; | |
253 | ||
254 | page = mapping->a_ops->get_xip_page(mapping, pgoff*(PAGE_SIZE/512), 0); | |
255 | if (!IS_ERR(page)) | |
256 | goto out; | |
257 | if (PTR_ERR(page) != -ENODATA) | |
258 | return NOPAGE_SIGBUS; | |
259 | ||
260 | /* sparse block */ | |
261 | if ((area->vm_flags & (VM_WRITE | VM_MAYWRITE)) && | |
262 | (area->vm_flags & (VM_SHARED| VM_MAYSHARE)) && | |
263 | (!(mapping->host->i_sb->s_flags & MS_RDONLY))) { | |
264 | /* maybe shared writable, allocate new block */ | |
265 | page = mapping->a_ops->get_xip_page (mapping, | |
266 | pgoff*(PAGE_SIZE/512), 1); | |
267 | if (IS_ERR(page)) | |
268 | return NOPAGE_SIGBUS; | |
269 | /* unmap page at pgoff from all other vmas */ | |
270 | __xip_unmap(mapping, pgoff); | |
271 | } else { | |
272 | /* not shared and writable, use xip_sparse_page() */ | |
273 | page = xip_sparse_page(); | |
274 | if (!page) | |
275 | return NOPAGE_OOM; | |
276 | } | |
277 | ||
278 | out: | |
279 | page_cache_get(page); | |
280 | return page; | |
281 | } | |
282 | ||
283 | static struct vm_operations_struct xip_file_vm_ops = { | |
284 | .nopage = xip_file_nopage, | |
285 | }; | |
286 | ||
287 | int xip_file_mmap(struct file * file, struct vm_area_struct * vma) | |
288 | { | |
289 | BUG_ON(!file->f_mapping->a_ops->get_xip_page); | |
290 | ||
291 | file_accessed(file); | |
292 | vma->vm_ops = &xip_file_vm_ops; | |
293 | return 0; | |
294 | } | |
295 | EXPORT_SYMBOL_GPL(xip_file_mmap); | |
296 | ||
297 | static ssize_t | |
298 | __xip_file_write(struct file *filp, const char __user *buf, | |
299 | size_t count, loff_t pos, loff_t *ppos) | |
300 | { | |
301 | struct address_space * mapping = filp->f_mapping; | |
302 | const struct address_space_operations *a_ops = mapping->a_ops; | |
303 | struct inode *inode = mapping->host; | |
304 | long status = 0; | |
305 | struct page *page; | |
306 | size_t bytes; | |
307 | ssize_t written = 0; | |
308 | ||
309 | BUG_ON(!mapping->a_ops->get_xip_page); | |
310 | ||
311 | do { | |
312 | unsigned long index; | |
313 | unsigned long offset; | |
314 | size_t copied; | |
315 | ||
316 | offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */ | |
317 | index = pos >> PAGE_CACHE_SHIFT; | |
318 | bytes = PAGE_CACHE_SIZE - offset; | |
319 | if (bytes > count) | |
320 | bytes = count; | |
321 | ||
322 | /* | |
323 | * Bring in the user page that we will copy from _first_. | |
324 | * Otherwise there's a nasty deadlock on copying from the | |
325 | * same page as we're writing to, without it being marked | |
326 | * up-to-date. | |
327 | */ | |
328 | fault_in_pages_readable(buf, bytes); | |
329 | ||
330 | page = a_ops->get_xip_page(mapping, | |
331 | index*(PAGE_SIZE/512), 0); | |
332 | if (IS_ERR(page) && (PTR_ERR(page) == -ENODATA)) { | |
333 | /* we allocate a new page unmap it */ | |
334 | page = a_ops->get_xip_page(mapping, | |
335 | index*(PAGE_SIZE/512), 1); | |
336 | if (!IS_ERR(page)) | |
337 | /* unmap page at pgoff from all other vmas */ | |
338 | __xip_unmap(mapping, index); | |
339 | } | |
340 | ||
341 | if (IS_ERR(page)) { | |
342 | status = PTR_ERR(page); | |
343 | break; | |
344 | } | |
345 | ||
346 | copied = filemap_copy_from_user(page, offset, buf, bytes); | |
347 | flush_dcache_page(page); | |
348 | if (likely(copied > 0)) { | |
349 | status = copied; | |
350 | ||
351 | if (status >= 0) { | |
352 | written += status; | |
353 | count -= status; | |
354 | pos += status; | |
355 | buf += status; | |
356 | } | |
357 | } | |
358 | if (unlikely(copied != bytes)) | |
359 | if (status >= 0) | |
360 | status = -EFAULT; | |
361 | if (status < 0) | |
362 | break; | |
363 | } while (count); | |
364 | *ppos = pos; | |
365 | /* | |
366 | * No need to use i_size_read() here, the i_size | |
367 | * cannot change under us because we hold i_mutex. | |
368 | */ | |
369 | if (pos > inode->i_size) { | |
370 | i_size_write(inode, pos); | |
371 | mark_inode_dirty(inode); | |
372 | } | |
373 | ||
374 | return written ? written : status; | |
375 | } | |
376 | ||
377 | ssize_t | |
378 | xip_file_write(struct file *filp, const char __user *buf, size_t len, | |
379 | loff_t *ppos) | |
380 | { | |
381 | struct address_space *mapping = filp->f_mapping; | |
382 | struct inode *inode = mapping->host; | |
383 | size_t count; | |
384 | loff_t pos; | |
385 | ssize_t ret; | |
386 | ||
387 | mutex_lock(&inode->i_mutex); | |
388 | ||
389 | if (!access_ok(VERIFY_READ, buf, len)) { | |
390 | ret=-EFAULT; | |
391 | goto out_up; | |
392 | } | |
393 | ||
394 | pos = *ppos; | |
395 | count = len; | |
396 | ||
397 | vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE); | |
398 | ||
399 | /* We can write back this queue in page reclaim */ | |
400 | current->backing_dev_info = mapping->backing_dev_info; | |
401 | ||
402 | ret = generic_write_checks(filp, &pos, &count, S_ISBLK(inode->i_mode)); | |
403 | if (ret) | |
404 | goto out_backing; | |
405 | if (count == 0) | |
406 | goto out_backing; | |
407 | ||
408 | ret = remove_suid(filp->f_path.dentry); | |
409 | if (ret) | |
410 | goto out_backing; | |
411 | ||
412 | file_update_time(filp); | |
413 | ||
414 | ret = __xip_file_write (filp, buf, count, pos, ppos); | |
415 | ||
416 | out_backing: | |
417 | current->backing_dev_info = NULL; | |
418 | out_up: | |
419 | mutex_unlock(&inode->i_mutex); | |
420 | return ret; | |
421 | } | |
422 | EXPORT_SYMBOL_GPL(xip_file_write); | |
423 | ||
424 | /* | |
425 | * truncate a page used for execute in place | |
426 | * functionality is analog to block_truncate_page but does use get_xip_page | |
427 | * to get the page instead of page cache | |
428 | */ | |
429 | int | |
430 | xip_truncate_page(struct address_space *mapping, loff_t from) | |
431 | { | |
432 | pgoff_t index = from >> PAGE_CACHE_SHIFT; | |
433 | unsigned offset = from & (PAGE_CACHE_SIZE-1); | |
434 | unsigned blocksize; | |
435 | unsigned length; | |
436 | struct page *page; | |
437 | void *kaddr; | |
438 | ||
439 | BUG_ON(!mapping->a_ops->get_xip_page); | |
440 | ||
441 | blocksize = 1 << mapping->host->i_blkbits; | |
442 | length = offset & (blocksize - 1); | |
443 | ||
444 | /* Block boundary? Nothing to do */ | |
445 | if (!length) | |
446 | return 0; | |
447 | ||
448 | length = blocksize - length; | |
449 | ||
450 | page = mapping->a_ops->get_xip_page(mapping, | |
451 | index*(PAGE_SIZE/512), 0); | |
452 | if (!page) | |
453 | return -ENOMEM; | |
454 | if (unlikely(IS_ERR(page))) { | |
455 | if (PTR_ERR(page) == -ENODATA) | |
456 | /* Hole? No need to truncate */ | |
457 | return 0; | |
458 | else | |
459 | return PTR_ERR(page); | |
460 | } | |
461 | kaddr = kmap_atomic(page, KM_USER0); | |
462 | memset(kaddr + offset, 0, length); | |
463 | kunmap_atomic(kaddr, KM_USER0); | |
464 | ||
465 | flush_dcache_page(page); | |
466 | return 0; | |
467 | } | |
468 | EXPORT_SYMBOL_GPL(xip_truncate_page); |