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/export.h>
14 #include <linux/uio.h>
15 #include <linux/rmap.h>
16 #include <linux/mmu_notifier.h>
17 #include <linux/sched.h>
18 #include <linux/seqlock.h>
19 #include <linux/mutex.h>
20 #include <linux/gfp.h>
21 #include <asm/tlbflush.h>
22 #include <asm/io.h>
23
24 /*
25 * We do use our own empty page to avoid interference with other users
26 * of ZERO_PAGE(), such as /dev/zero
27 */
28 static DEFINE_MUTEX(xip_sparse_mutex);
29 static seqcount_t xip_sparse_seq = SEQCNT_ZERO(xip_sparse_seq);
30 static struct page *__xip_sparse_page;
31
32 /* called under xip_sparse_mutex */
xip_sparse_page(void)33 static struct page *xip_sparse_page(void)
34 {
35 if (!__xip_sparse_page) {
36 struct page *page = alloc_page(GFP_HIGHUSER | __GFP_ZERO);
37
38 if (page)
39 __xip_sparse_page = page;
40 }
41 return __xip_sparse_page;
42 }
43
44 /*
45 * This is a file read routine for execute in place files, and uses
46 * the mapping->a_ops->get_xip_mem() function for the actual low-level
47 * stuff.
48 *
49 * Note the struct file* is not used at all. It may be NULL.
50 */
51 static ssize_t
do_xip_mapping_read(struct address_space * mapping,struct file_ra_state * _ra,struct file * filp,char __user * buf,size_t len,loff_t * ppos)52 do_xip_mapping_read(struct address_space *mapping,
53 struct file_ra_state *_ra,
54 struct file *filp,
55 char __user *buf,
56 size_t len,
57 loff_t *ppos)
58 {
59 struct inode *inode = mapping->host;
60 pgoff_t index, end_index;
61 unsigned long offset;
62 loff_t isize, pos;
63 size_t copied = 0, error = 0;
64
65 BUG_ON(!mapping->a_ops->get_xip_mem);
66
67 pos = *ppos;
68 index = pos >> PAGE_CACHE_SHIFT;
69 offset = pos & ~PAGE_CACHE_MASK;
70
71 isize = i_size_read(inode);
72 if (!isize)
73 goto out;
74
75 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
76 do {
77 unsigned long nr, left;
78 void *xip_mem;
79 unsigned long xip_pfn;
80 int zero = 0;
81
82 /* nr is the maximum number of bytes to copy from this page */
83 nr = PAGE_CACHE_SIZE;
84 if (index >= end_index) {
85 if (index > end_index)
86 goto out;
87 nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
88 if (nr <= offset) {
89 goto out;
90 }
91 }
92 nr = nr - offset;
93 if (nr > len - copied)
94 nr = len - copied;
95
96 error = mapping->a_ops->get_xip_mem(mapping, index, 0,
97 &xip_mem, &xip_pfn);
98 if (unlikely(error)) {
99 if (error == -ENODATA) {
100 /* sparse */
101 zero = 1;
102 } else
103 goto out;
104 }
105
106 /* If users can be writing to this page using arbitrary
107 * virtual addresses, take care about potential aliasing
108 * before reading the page on the kernel side.
109 */
110 if (mapping_writably_mapped(mapping))
111 /* address based flush */ ;
112
113 /*
114 * Ok, we have the mem, so now we can copy it to user space...
115 *
116 * The actor routine returns how many bytes were actually used..
117 * NOTE! This may not be the same as how much of a user buffer
118 * we filled up (we may be padding etc), so we can only update
119 * "pos" here (the actor routine has to update the user buffer
120 * pointers and the remaining count).
121 */
122 if (!zero)
123 left = __copy_to_user(buf+copied, xip_mem+offset, nr);
124 else
125 left = __clear_user(buf + copied, nr);
126
127 if (left) {
128 error = -EFAULT;
129 goto out;
130 }
131
132 copied += (nr - left);
133 offset += (nr - left);
134 index += offset >> PAGE_CACHE_SHIFT;
135 offset &= ~PAGE_CACHE_MASK;
136 } while (copied < len);
137
138 out:
139 *ppos = pos + copied;
140 if (filp)
141 file_accessed(filp);
142
143 return (copied ? copied : error);
144 }
145
146 ssize_t
xip_file_read(struct file * filp,char __user * buf,size_t len,loff_t * ppos)147 xip_file_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
148 {
149 if (!access_ok(VERIFY_WRITE, buf, len))
150 return -EFAULT;
151
152 return do_xip_mapping_read(filp->f_mapping, &filp->f_ra, filp,
153 buf, len, ppos);
154 }
155 EXPORT_SYMBOL_GPL(xip_file_read);
156
157 /*
158 * __xip_unmap is invoked from xip_unmap and
159 * xip_write
160 *
161 * This function walks all vmas of the address_space and unmaps the
162 * __xip_sparse_page when found at pgoff.
163 */
164 static void
__xip_unmap(struct address_space * mapping,unsigned long pgoff)165 __xip_unmap (struct address_space * mapping,
166 unsigned long pgoff)
167 {
168 struct vm_area_struct *vma;
169 struct mm_struct *mm;
170 unsigned long address;
171 pte_t *pte;
172 pte_t pteval;
173 spinlock_t *ptl;
174 struct page *page;
175 unsigned count;
176 int locked = 0;
177
178 count = read_seqcount_begin(&xip_sparse_seq);
179
180 page = __xip_sparse_page;
181 if (!page)
182 return;
183
184 retry:
185 mutex_lock(&mapping->i_mmap_mutex);
186 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
187 mm = vma->vm_mm;
188 address = vma->vm_start +
189 ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
190 BUG_ON(address < vma->vm_start || address >= vma->vm_end);
191 pte = page_check_address(page, mm, address, &ptl, 1);
192 if (pte) {
193 /* Nuke the page table entry. */
194 flush_cache_page(vma, address, pte_pfn(*pte));
195 pteval = ptep_clear_flush(vma, address, pte);
196 page_remove_rmap(page);
197 dec_mm_counter(mm, MM_FILEPAGES);
198 BUG_ON(pte_dirty(pteval));
199 pte_unmap_unlock(pte, ptl);
200 /* must invalidate_page _before_ freeing the page */
201 mmu_notifier_invalidate_page(mm, address);
202 page_cache_release(page);
203 }
204 }
205 mutex_unlock(&mapping->i_mmap_mutex);
206
207 if (locked) {
208 mutex_unlock(&xip_sparse_mutex);
209 } else if (read_seqcount_retry(&xip_sparse_seq, count)) {
210 mutex_lock(&xip_sparse_mutex);
211 locked = 1;
212 goto retry;
213 }
214 }
215
216 /*
217 * xip_fault() is invoked via the vma operations vector for a
218 * mapped memory region to read in file data during a page fault.
219 *
220 * This function is derived from filemap_fault, but used for execute in place
221 */
xip_file_fault(struct vm_area_struct * vma,struct vm_fault * vmf)222 static int xip_file_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
223 {
224 struct file *file = vma->vm_file;
225 struct address_space *mapping = file->f_mapping;
226 struct inode *inode = mapping->host;
227 pgoff_t size;
228 void *xip_mem;
229 unsigned long xip_pfn;
230 struct page *page;
231 int error;
232
233 /* XXX: are VM_FAULT_ codes OK? */
234 again:
235 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
236 if (vmf->pgoff >= size)
237 return VM_FAULT_SIGBUS;
238
239 error = mapping->a_ops->get_xip_mem(mapping, vmf->pgoff, 0,
240 &xip_mem, &xip_pfn);
241 if (likely(!error))
242 goto found;
243 if (error != -ENODATA)
244 return VM_FAULT_OOM;
245
246 /* sparse block */
247 if ((vma->vm_flags & (VM_WRITE | VM_MAYWRITE)) &&
248 (vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) &&
249 (!(mapping->host->i_sb->s_flags & MS_RDONLY))) {
250 int err;
251
252 /* maybe shared writable, allocate new block */
253 mutex_lock(&xip_sparse_mutex);
254 error = mapping->a_ops->get_xip_mem(mapping, vmf->pgoff, 1,
255 &xip_mem, &xip_pfn);
256 mutex_unlock(&xip_sparse_mutex);
257 if (error)
258 return VM_FAULT_SIGBUS;
259 /* unmap sparse mappings at pgoff from all other vmas */
260 __xip_unmap(mapping, vmf->pgoff);
261
262 found:
263 err = vm_insert_mixed(vma, (unsigned long)vmf->virtual_address,
264 xip_pfn);
265 if (err == -ENOMEM)
266 return VM_FAULT_OOM;
267 /*
268 * err == -EBUSY is fine, we've raced against another thread
269 * that faulted-in the same page
270 */
271 if (err != -EBUSY)
272 BUG_ON(err);
273 return VM_FAULT_NOPAGE;
274 } else {
275 int err, ret = VM_FAULT_OOM;
276
277 mutex_lock(&xip_sparse_mutex);
278 write_seqcount_begin(&xip_sparse_seq);
279 error = mapping->a_ops->get_xip_mem(mapping, vmf->pgoff, 0,
280 &xip_mem, &xip_pfn);
281 if (unlikely(!error)) {
282 write_seqcount_end(&xip_sparse_seq);
283 mutex_unlock(&xip_sparse_mutex);
284 goto again;
285 }
286 if (error != -ENODATA)
287 goto out;
288 /* not shared and writable, use xip_sparse_page() */
289 page = xip_sparse_page();
290 if (!page)
291 goto out;
292 err = vm_insert_page(vma, (unsigned long)vmf->virtual_address,
293 page);
294 if (err == -ENOMEM)
295 goto out;
296
297 ret = VM_FAULT_NOPAGE;
298 out:
299 write_seqcount_end(&xip_sparse_seq);
300 mutex_unlock(&xip_sparse_mutex);
301
302 return ret;
303 }
304 }
305
306 static const struct vm_operations_struct xip_file_vm_ops = {
307 .fault = xip_file_fault,
308 .page_mkwrite = filemap_page_mkwrite,
309 .remap_pages = generic_file_remap_pages,
310 };
311
xip_file_mmap(struct file * file,struct vm_area_struct * vma)312 int xip_file_mmap(struct file * file, struct vm_area_struct * vma)
313 {
314 BUG_ON(!file->f_mapping->a_ops->get_xip_mem);
315
316 file_accessed(file);
317 vma->vm_ops = &xip_file_vm_ops;
318 vma->vm_flags |= VM_MIXEDMAP;
319 return 0;
320 }
321 EXPORT_SYMBOL_GPL(xip_file_mmap);
322
323 static ssize_t
__xip_file_write(struct file * filp,const char __user * buf,size_t count,loff_t pos,loff_t * ppos)324 __xip_file_write(struct file *filp, const char __user *buf,
325 size_t count, loff_t pos, loff_t *ppos)
326 {
327 struct address_space * mapping = filp->f_mapping;
328 const struct address_space_operations *a_ops = mapping->a_ops;
329 struct inode *inode = mapping->host;
330 long status = 0;
331 size_t bytes;
332 ssize_t written = 0;
333
334 BUG_ON(!mapping->a_ops->get_xip_mem);
335
336 do {
337 unsigned long index;
338 unsigned long offset;
339 size_t copied;
340 void *xip_mem;
341 unsigned long xip_pfn;
342
343 offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
344 index = pos >> PAGE_CACHE_SHIFT;
345 bytes = PAGE_CACHE_SIZE - offset;
346 if (bytes > count)
347 bytes = count;
348
349 status = a_ops->get_xip_mem(mapping, index, 0,
350 &xip_mem, &xip_pfn);
351 if (status == -ENODATA) {
352 /* we allocate a new page unmap it */
353 mutex_lock(&xip_sparse_mutex);
354 status = a_ops->get_xip_mem(mapping, index, 1,
355 &xip_mem, &xip_pfn);
356 mutex_unlock(&xip_sparse_mutex);
357 if (!status)
358 /* unmap page at pgoff from all other vmas */
359 __xip_unmap(mapping, index);
360 }
361
362 if (status)
363 break;
364
365 copied = bytes -
366 __copy_from_user_nocache(xip_mem + offset, buf, bytes);
367
368 if (likely(copied > 0)) {
369 status = copied;
370
371 if (status >= 0) {
372 written += status;
373 count -= status;
374 pos += status;
375 buf += status;
376 }
377 }
378 if (unlikely(copied != bytes))
379 if (status >= 0)
380 status = -EFAULT;
381 if (status < 0)
382 break;
383 } while (count);
384 *ppos = pos;
385 /*
386 * No need to use i_size_read() here, the i_size
387 * cannot change under us because we hold i_mutex.
388 */
389 if (pos > inode->i_size) {
390 i_size_write(inode, pos);
391 mark_inode_dirty(inode);
392 }
393
394 return written ? written : status;
395 }
396
397 ssize_t
xip_file_write(struct file * filp,const char __user * buf,size_t len,loff_t * ppos)398 xip_file_write(struct file *filp, const char __user *buf, size_t len,
399 loff_t *ppos)
400 {
401 struct address_space *mapping = filp->f_mapping;
402 struct inode *inode = mapping->host;
403 size_t count;
404 loff_t pos;
405 ssize_t ret;
406
407 mutex_lock(&inode->i_mutex);
408
409 if (!access_ok(VERIFY_READ, buf, len)) {
410 ret=-EFAULT;
411 goto out_up;
412 }
413
414 pos = *ppos;
415 count = len;
416
417 /* We can write back this queue in page reclaim */
418 current->backing_dev_info = mapping->backing_dev_info;
419
420 ret = generic_write_checks(filp, &pos, &count, S_ISBLK(inode->i_mode));
421 if (ret)
422 goto out_backing;
423 if (count == 0)
424 goto out_backing;
425
426 ret = file_remove_suid(filp);
427 if (ret)
428 goto out_backing;
429
430 ret = file_update_time(filp);
431 if (ret)
432 goto out_backing;
433
434 ret = __xip_file_write (filp, buf, count, pos, ppos);
435
436 out_backing:
437 current->backing_dev_info = NULL;
438 out_up:
439 mutex_unlock(&inode->i_mutex);
440 return ret;
441 }
442 EXPORT_SYMBOL_GPL(xip_file_write);
443
444 /*
445 * truncate a page used for execute in place
446 * functionality is analog to block_truncate_page but does use get_xip_mem
447 * to get the page instead of page cache
448 */
449 int
xip_truncate_page(struct address_space * mapping,loff_t from)450 xip_truncate_page(struct address_space *mapping, loff_t from)
451 {
452 pgoff_t index = from >> PAGE_CACHE_SHIFT;
453 unsigned offset = from & (PAGE_CACHE_SIZE-1);
454 unsigned blocksize;
455 unsigned length;
456 void *xip_mem;
457 unsigned long xip_pfn;
458 int err;
459
460 BUG_ON(!mapping->a_ops->get_xip_mem);
461
462 blocksize = 1 << mapping->host->i_blkbits;
463 length = offset & (blocksize - 1);
464
465 /* Block boundary? Nothing to do */
466 if (!length)
467 return 0;
468
469 length = blocksize - length;
470
471 err = mapping->a_ops->get_xip_mem(mapping, index, 0,
472 &xip_mem, &xip_pfn);
473 if (unlikely(err)) {
474 if (err == -ENODATA)
475 /* Hole? No need to truncate */
476 return 0;
477 else
478 return err;
479 }
480 memset(xip_mem + offset, 0, length);
481 return 0;
482 }
483 EXPORT_SYMBOL_GPL(xip_truncate_page);
484