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;
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 struct prio_tree_iter iter;
171 unsigned long address;
172 pte_t *pte;
173 pte_t pteval;
174 spinlock_t *ptl;
175 struct page *page;
176 unsigned count;
177 int locked = 0;
178
179 count = read_seqcount_begin(&xip_sparse_seq);
180
181 page = __xip_sparse_page;
182 if (!page)
183 return;
184
185 retry:
186 mutex_lock(&mapping->i_mmap_mutex);
187 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
188 mm = vma->vm_mm;
189 address = vma->vm_start +
190 ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
191 BUG_ON(address < vma->vm_start || address >= vma->vm_end);
192 pte = page_check_address(page, mm, address, &ptl, 1);
193 if (pte) {
194 /* Nuke the page table entry. */
195 flush_cache_page(vma, address, pte_pfn(*pte));
196 pteval = ptep_clear_flush_notify(vma, address, pte);
197 page_remove_rmap(page);
198 dec_mm_counter(mm, MM_FILEPAGES);
199 BUG_ON(pte_dirty(pteval));
200 pte_unmap_unlock(pte, ptl);
201 page_cache_release(page);
202 }
203 }
204 mutex_unlock(&mapping->i_mmap_mutex);
205
206 if (locked) {
207 mutex_unlock(&xip_sparse_mutex);
208 } else if (read_seqcount_retry(&xip_sparse_seq, count)) {
209 mutex_lock(&xip_sparse_mutex);
210 locked = 1;
211 goto retry;
212 }
213 }
214
215 /*
216 * xip_fault() is invoked via the vma operations vector for a
217 * mapped memory region to read in file data during a page fault.
218 *
219 * This function is derived from filemap_fault, but used for execute in place
220 */
xip_file_fault(struct vm_area_struct * vma,struct vm_fault * vmf)221 static int xip_file_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
222 {
223 struct file *file = vma->vm_file;
224 struct address_space *mapping = file->f_mapping;
225 struct inode *inode = mapping->host;
226 pgoff_t size;
227 void *xip_mem;
228 unsigned long xip_pfn;
229 struct page *page;
230 int error;
231
232 /* XXX: are VM_FAULT_ codes OK? */
233 again:
234 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
235 if (vmf->pgoff >= size)
236 return VM_FAULT_SIGBUS;
237
238 error = mapping->a_ops->get_xip_mem(mapping, vmf->pgoff, 0,
239 &xip_mem, &xip_pfn);
240 if (likely(!error))
241 goto found;
242 if (error != -ENODATA)
243 return VM_FAULT_OOM;
244
245 /* sparse block */
246 if ((vma->vm_flags & (VM_WRITE | VM_MAYWRITE)) &&
247 (vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) &&
248 (!(mapping->host->i_sb->s_flags & MS_RDONLY))) {
249 int err;
250
251 /* maybe shared writable, allocate new block */
252 mutex_lock(&xip_sparse_mutex);
253 error = mapping->a_ops->get_xip_mem(mapping, vmf->pgoff, 1,
254 &xip_mem, &xip_pfn);
255 mutex_unlock(&xip_sparse_mutex);
256 if (error)
257 return VM_FAULT_SIGBUS;
258 /* unmap sparse mappings at pgoff from all other vmas */
259 __xip_unmap(mapping, vmf->pgoff);
260
261 found:
262 err = vm_insert_mixed(vma, (unsigned long)vmf->virtual_address,
263 xip_pfn);
264 if (err == -ENOMEM)
265 return VM_FAULT_OOM;
266 /*
267 * err == -EBUSY is fine, we've raced against another thread
268 * that faulted-in the same page
269 */
270 if (err != -EBUSY)
271 BUG_ON(err);
272 return VM_FAULT_NOPAGE;
273 } else {
274 int err, ret = VM_FAULT_OOM;
275
276 mutex_lock(&xip_sparse_mutex);
277 write_seqcount_begin(&xip_sparse_seq);
278 error = mapping->a_ops->get_xip_mem(mapping, vmf->pgoff, 0,
279 &xip_mem, &xip_pfn);
280 if (unlikely(!error)) {
281 write_seqcount_end(&xip_sparse_seq);
282 mutex_unlock(&xip_sparse_mutex);
283 goto again;
284 }
285 if (error != -ENODATA)
286 goto out;
287 /* not shared and writable, use xip_sparse_page() */
288 page = xip_sparse_page();
289 if (!page)
290 goto out;
291 err = vm_insert_page(vma, (unsigned long)vmf->virtual_address,
292 page);
293 if (err == -ENOMEM)
294 goto out;
295
296 ret = VM_FAULT_NOPAGE;
297 out:
298 write_seqcount_end(&xip_sparse_seq);
299 mutex_unlock(&xip_sparse_mutex);
300
301 return ret;
302 }
303 }
304
305 static const struct vm_operations_struct xip_file_vm_ops = {
306 .fault = xip_file_fault,
307 };
308
xip_file_mmap(struct file * file,struct vm_area_struct * vma)309 int xip_file_mmap(struct file * file, struct vm_area_struct * vma)
310 {
311 BUG_ON(!file->f_mapping->a_ops->get_xip_mem);
312
313 file_accessed(file);
314 vma->vm_ops = &xip_file_vm_ops;
315 vma->vm_flags |= VM_CAN_NONLINEAR | VM_MIXEDMAP;
316 return 0;
317 }
318 EXPORT_SYMBOL_GPL(xip_file_mmap);
319
320 static ssize_t
__xip_file_write(struct file * filp,const char __user * buf,size_t count,loff_t pos,loff_t * ppos)321 __xip_file_write(struct file *filp, const char __user *buf,
322 size_t count, loff_t pos, loff_t *ppos)
323 {
324 struct address_space * mapping = filp->f_mapping;
325 const struct address_space_operations *a_ops = mapping->a_ops;
326 struct inode *inode = mapping->host;
327 long status = 0;
328 size_t bytes;
329 ssize_t written = 0;
330
331 BUG_ON(!mapping->a_ops->get_xip_mem);
332
333 do {
334 unsigned long index;
335 unsigned long offset;
336 size_t copied;
337 void *xip_mem;
338 unsigned long xip_pfn;
339
340 offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
341 index = pos >> PAGE_CACHE_SHIFT;
342 bytes = PAGE_CACHE_SIZE - offset;
343 if (bytes > count)
344 bytes = count;
345
346 status = a_ops->get_xip_mem(mapping, index, 0,
347 &xip_mem, &xip_pfn);
348 if (status == -ENODATA) {
349 /* we allocate a new page unmap it */
350 mutex_lock(&xip_sparse_mutex);
351 status = a_ops->get_xip_mem(mapping, index, 1,
352 &xip_mem, &xip_pfn);
353 mutex_unlock(&xip_sparse_mutex);
354 if (!status)
355 /* unmap page at pgoff from all other vmas */
356 __xip_unmap(mapping, index);
357 }
358
359 if (status)
360 break;
361
362 copied = bytes -
363 __copy_from_user_nocache(xip_mem + offset, buf, bytes);
364
365 if (likely(copied > 0)) {
366 status = copied;
367
368 if (status >= 0) {
369 written += status;
370 count -= status;
371 pos += status;
372 buf += status;
373 }
374 }
375 if (unlikely(copied != bytes))
376 if (status >= 0)
377 status = -EFAULT;
378 if (status < 0)
379 break;
380 } while (count);
381 *ppos = pos;
382 /*
383 * No need to use i_size_read() here, the i_size
384 * cannot change under us because we hold i_mutex.
385 */
386 if (pos > inode->i_size) {
387 i_size_write(inode, pos);
388 mark_inode_dirty(inode);
389 }
390
391 return written ? written : status;
392 }
393
394 ssize_t
xip_file_write(struct file * filp,const char __user * buf,size_t len,loff_t * ppos)395 xip_file_write(struct file *filp, const char __user *buf, size_t len,
396 loff_t *ppos)
397 {
398 struct address_space *mapping = filp->f_mapping;
399 struct inode *inode = mapping->host;
400 size_t count;
401 loff_t pos;
402 ssize_t ret;
403
404 mutex_lock(&inode->i_mutex);
405
406 if (!access_ok(VERIFY_READ, buf, len)) {
407 ret=-EFAULT;
408 goto out_up;
409 }
410
411 pos = *ppos;
412 count = len;
413
414 vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
415
416 /* We can write back this queue in page reclaim */
417 current->backing_dev_info = mapping->backing_dev_info;
418
419 ret = generic_write_checks(filp, &pos, &count, S_ISBLK(inode->i_mode));
420 if (ret)
421 goto out_backing;
422 if (count == 0)
423 goto out_backing;
424
425 ret = file_remove_suid(filp);
426 if (ret)
427 goto out_backing;
428
429 file_update_time(filp);
430
431 ret = __xip_file_write (filp, buf, count, pos, ppos);
432
433 out_backing:
434 current->backing_dev_info = NULL;
435 out_up:
436 mutex_unlock(&inode->i_mutex);
437 return ret;
438 }
439 EXPORT_SYMBOL_GPL(xip_file_write);
440
441 /*
442 * truncate a page used for execute in place
443 * functionality is analog to block_truncate_page but does use get_xip_mem
444 * to get the page instead of page cache
445 */
446 int
xip_truncate_page(struct address_space * mapping,loff_t from)447 xip_truncate_page(struct address_space *mapping, loff_t from)
448 {
449 pgoff_t index = from >> PAGE_CACHE_SHIFT;
450 unsigned offset = from & (PAGE_CACHE_SIZE-1);
451 unsigned blocksize;
452 unsigned length;
453 void *xip_mem;
454 unsigned long xip_pfn;
455 int err;
456
457 BUG_ON(!mapping->a_ops->get_xip_mem);
458
459 blocksize = 1 << mapping->host->i_blkbits;
460 length = offset & (blocksize - 1);
461
462 /* Block boundary? Nothing to do */
463 if (!length)
464 return 0;
465
466 length = blocksize - length;
467
468 err = mapping->a_ops->get_xip_mem(mapping, index, 0,
469 &xip_mem, &xip_pfn);
470 if (unlikely(err)) {
471 if (err == -ENODATA)
472 /* Hole? No need to truncate */
473 return 0;
474 else
475 return err;
476 }
477 memset(xip_mem + offset, 0, length);
478 return 0;
479 }
480 EXPORT_SYMBOL_GPL(xip_truncate_page);
481