filemap_xip.c revision 082ff0a9991dcea958785115fbba6dddd0dc280a 
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 * This is a file read routine for execute in place files, and uses
21 * the mapping->a_ops->get_xip_page() function for the actual low-level
22 * stuff.
23 *
24 * Note the struct file* is not used at all.  It may be NULL.
25 */
26static void
27do_xip_mapping_read(struct address_space *mapping,
28		    struct file_ra_state *_ra,
29		    struct file *filp,
30		    loff_t *ppos,
31		    read_descriptor_t *desc,
32		    read_actor_t actor)
33{
34	struct inode *inode = mapping->host;
35	unsigned long index, end_index, offset;
36	loff_t isize;
37
38	BUG_ON(!mapping->a_ops->get_xip_page);
39
40	index = *ppos >> PAGE_CACHE_SHIFT;
41	offset = *ppos & ~PAGE_CACHE_MASK;
42
43	isize = i_size_read(inode);
44	if (!isize)
45		goto out;
46
47	end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
48	for (;;) {
49		struct page *page;
50		unsigned long nr, ret;
51
52		/* nr is the maximum number of bytes to copy from this page */
53		nr = PAGE_CACHE_SIZE;
54		if (index >= end_index) {
55			if (index > end_index)
56				goto out;
57			nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
58			if (nr <= offset) {
59				goto out;
60			}
61		}
62		nr = nr - offset;
63
64		page = mapping->a_ops->get_xip_page(mapping,
65			index*(PAGE_SIZE/512), 0);
66		if (!page)
67			goto no_xip_page;
68		if (unlikely(IS_ERR(page))) {
69			if (PTR_ERR(page) == -ENODATA) {
70				/* sparse */
71				page = virt_to_page(empty_zero_page);
72			} else {
73				desc->error = PTR_ERR(page);
74				goto out;
75			}
76		} else
77			BUG_ON(!PageUptodate(page));
78
79		/* If users can be writing to this page using arbitrary
80		 * virtual addresses, take care about potential aliasing
81		 * before reading the page on the kernel side.
82		 */
83		if (mapping_writably_mapped(mapping))
84			flush_dcache_page(page);
85
86		/*
87		 * Ok, we have the page, and it's up-to-date, so
88		 * now we can copy it to user space...
89		 *
90		 * The actor routine returns how many bytes were actually used..
91		 * NOTE! This may not be the same as how much of a user buffer
92		 * we filled up (we may be padding etc), so we can only update
93		 * "pos" here (the actor routine has to update the user buffer
94		 * pointers and the remaining count).
95		 */
96		ret = actor(desc, page, offset, nr);
97		offset += ret;
98		index += offset >> PAGE_CACHE_SHIFT;
99		offset &= ~PAGE_CACHE_MASK;
100
101		if (ret == nr && desc->count)
102			continue;
103		goto out;
104
105no_xip_page:
106		/* Did not get the page. Report it */
107		desc->error = -EIO;
108		goto out;
109	}
110
111out:
112	*ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
113	if (filp)
114		file_accessed(filp);
115}
116
117ssize_t
118xip_file_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
119{
120	read_descriptor_t desc;
121
122	if (!access_ok(VERIFY_WRITE, buf, len))
123		return -EFAULT;
124
125	desc.written = 0;
126	desc.arg.buf = buf;
127	desc.count = len;
128	desc.error = 0;
129
130	do_xip_mapping_read(filp->f_mapping, &filp->f_ra, filp,
131			    ppos, &desc, file_read_actor);
132
133	if (desc.written)
134		return desc.written;
135	else
136		return desc.error;
137}
138EXPORT_SYMBOL_GPL(xip_file_read);
139
140ssize_t
141xip_file_sendfile(struct file *in_file, loff_t *ppos,
142	     size_t count, read_actor_t actor, void *target)
143{
144	read_descriptor_t desc;
145
146	if (!count)
147		return 0;
148
149	desc.written = 0;
150	desc.count = count;
151	desc.arg.data = target;
152	desc.error = 0;
153
154	do_xip_mapping_read(in_file->f_mapping, &in_file->f_ra, in_file,
155			    ppos, &desc, actor);
156	if (desc.written)
157		return desc.written;
158	return desc.error;
159}
160EXPORT_SYMBOL_GPL(xip_file_sendfile);
161
162/*
163 * __xip_unmap is invoked from xip_unmap and
164 * xip_write
165 *
166 * This function walks all vmas of the address_space and unmaps the
167 * empty_zero_page when found at pgoff. Should it go in rmap.c?
168 */
169static void
170__xip_unmap (struct address_space * mapping,
171		     unsigned long pgoff)
172{
173	struct vm_area_struct *vma;
174	struct mm_struct *mm;
175	struct prio_tree_iter iter;
176	unsigned long address;
177	pte_t *pte;
178	pte_t pteval;
179
180	spin_lock(&mapping->i_mmap_lock);
181	vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
182		mm = vma->vm_mm;
183		address = vma->vm_start +
184			((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
185		BUG_ON(address < vma->vm_start || address >= vma->vm_end);
186		/*
187		 * We need the page_table_lock to protect us from page faults,
188		 * munmap, fork, etc...
189		 */
190		pte = page_check_address(virt_to_page(empty_zero_page), mm,
191					 address);
192		if (!IS_ERR(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			BUG_ON(pte_dirty(pteval));
197			pte_unmap(pte);
198			spin_unlock(&mm->page_table_lock);
199		}
200	}
201	spin_unlock(&mapping->i_mmap_lock);
202}
203
204/*
205 * xip_nopage() is invoked via the vma operations vector for a
206 * mapped memory region to read in file data during a page fault.
207 *
208 * This function is derived from filemap_nopage, but used for execute in place
209 */
210static struct page *
211xip_file_nopage(struct vm_area_struct * area,
212		   unsigned long address,
213		   int *type)
214{
215	struct file *file = area->vm_file;
216	struct address_space *mapping = file->f_mapping;
217	struct inode *inode = mapping->host;
218	struct page *page;
219	unsigned long size, pgoff, endoff;
220
221	pgoff = ((address - area->vm_start) >> PAGE_CACHE_SHIFT)
222		+ area->vm_pgoff;
223	endoff = ((area->vm_end - area->vm_start) >> PAGE_CACHE_SHIFT)
224		+ area->vm_pgoff;
225
226	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
227	if (pgoff >= size) {
228		return NULL;
229	}
230
231	page = mapping->a_ops->get_xip_page(mapping, pgoff*(PAGE_SIZE/512), 0);
232	if (!IS_ERR(page)) {
233		BUG_ON(!PageUptodate(page));
234		return page;
235	}
236	if (PTR_ERR(page) != -ENODATA)
237		return NULL;
238
239	/* sparse block */
240	if ((area->vm_flags & (VM_WRITE | VM_MAYWRITE)) &&
241	    (area->vm_flags & (VM_SHARED| VM_MAYSHARE)) &&
242	    (!(mapping->host->i_sb->s_flags & MS_RDONLY))) {
243		/* maybe shared writable, allocate new block */
244		page = mapping->a_ops->get_xip_page (mapping,
245			pgoff*(PAGE_SIZE/512), 1);
246		if (IS_ERR(page))
247			return NULL;
248		BUG_ON(!PageUptodate(page));
249		/* unmap page at pgoff from all other vmas */
250		__xip_unmap(mapping, pgoff);
251	} else {
252		/* not shared and writable, use empty_zero_page */
253		page = virt_to_page(empty_zero_page);
254	}
255
256	return page;
257}
258
259static struct vm_operations_struct xip_file_vm_ops = {
260	.nopage         = xip_file_nopage,
261};
262
263int xip_file_mmap(struct file * file, struct vm_area_struct * vma)
264{
265	BUG_ON(!file->f_mapping->a_ops->get_xip_page);
266
267	file_accessed(file);
268	vma->vm_ops = &xip_file_vm_ops;
269	return 0;
270}
271EXPORT_SYMBOL_GPL(xip_file_mmap);
272
273static ssize_t
274__xip_file_write(struct file *filp, const char __user *buf,
275		  size_t count, loff_t pos, loff_t *ppos)
276{
277	struct address_space * mapping = filp->f_mapping;
278	struct address_space_operations *a_ops = mapping->a_ops;
279	struct inode 	*inode = mapping->host;
280	long		status = 0;
281	struct page	*page;
282	size_t		bytes;
283	ssize_t		written = 0;
284
285	BUG_ON(!mapping->a_ops->get_xip_page);
286
287	do {
288		unsigned long index;
289		unsigned long offset;
290		size_t copied;
291
292		offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
293		index = pos >> PAGE_CACHE_SHIFT;
294		bytes = PAGE_CACHE_SIZE - offset;
295		if (bytes > count)
296			bytes = count;
297
298		/*
299		 * Bring in the user page that we will copy from _first_.
300		 * Otherwise there's a nasty deadlock on copying from the
301		 * same page as we're writing to, without it being marked
302		 * up-to-date.
303		 */
304		fault_in_pages_readable(buf, bytes);
305
306		page = a_ops->get_xip_page(mapping,
307					   index*(PAGE_SIZE/512), 0);
308		if (IS_ERR(page) && (PTR_ERR(page) == -ENODATA)) {
309			/* we allocate a new page unmap it */
310			page = a_ops->get_xip_page(mapping,
311						   index*(PAGE_SIZE/512), 1);
312			if (!IS_ERR(page))
313				/* unmap page at pgoff from all other vmas */
314				__xip_unmap(mapping, index);
315		}
316
317		if (IS_ERR(page)) {
318			status = PTR_ERR(page);
319			break;
320		}
321
322		BUG_ON(!PageUptodate(page));
323
324		copied = filemap_copy_from_user(page, offset, buf, bytes);
325		flush_dcache_page(page);
326		if (likely(copied > 0)) {
327			status = copied;
328
329			if (status >= 0) {
330				written += status;
331				count -= status;
332				pos += status;
333				buf += status;
334			}
335		}
336		if (unlikely(copied != bytes))
337			if (status >= 0)
338				status = -EFAULT;
339		if (status < 0)
340			break;
341	} while (count);
342	*ppos = pos;
343	/*
344	 * No need to use i_size_read() here, the i_size
345	 * cannot change under us because we hold i_sem.
346	 */
347	if (pos > inode->i_size) {
348		i_size_write(inode, pos);
349		mark_inode_dirty(inode);
350	}
351
352	return written ? written : status;
353}
354
355ssize_t
356xip_file_write(struct file *filp, const char __user *buf, size_t len,
357	       loff_t *ppos)
358{
359	struct address_space *mapping = filp->f_mapping;
360	struct inode *inode = mapping->host;
361	size_t count;
362	loff_t pos;
363	ssize_t ret;
364
365	down(&inode->i_sem);
366
367	if (!access_ok(VERIFY_READ, buf, len)) {
368		ret=-EFAULT;
369		goto out_up;
370	}
371
372	pos = *ppos;
373	count = len;
374
375	vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
376
377	/* We can write back this queue in page reclaim */
378	current->backing_dev_info = mapping->backing_dev_info;
379
380	ret = generic_write_checks(filp, &pos, &count, S_ISBLK(inode->i_mode));
381	if (ret)
382		goto out_backing;
383	if (count == 0)
384		goto out_backing;
385
386	ret = remove_suid(filp->f_dentry);
387	if (ret)
388		goto out_backing;
389
390	inode_update_time(inode, 1);
391
392	ret = __xip_file_write (filp, buf, count, pos, ppos);
393
394 out_backing:
395	current->backing_dev_info = NULL;
396 out_up:
397	up(&inode->i_sem);
398	return ret;
399}
400EXPORT_SYMBOL_GPL(xip_file_write);
401
402/*
403 * truncate a page used for execute in place
404 * functionality is analog to block_truncate_page but does use get_xip_page
405 * to get the page instead of page cache
406 */
407int
408xip_truncate_page(struct address_space *mapping, loff_t from)
409{
410	pgoff_t index = from >> PAGE_CACHE_SHIFT;
411	unsigned offset = from & (PAGE_CACHE_SIZE-1);
412	unsigned blocksize;
413	unsigned length;
414	struct page *page;
415	void *kaddr;
416
417	BUG_ON(!mapping->a_ops->get_xip_page);
418
419	blocksize = 1 << mapping->host->i_blkbits;
420	length = offset & (blocksize - 1);
421
422	/* Block boundary? Nothing to do */
423	if (!length)
424		return 0;
425
426	length = blocksize - length;
427
428	page = mapping->a_ops->get_xip_page(mapping,
429					    index*(PAGE_SIZE/512), 0);
430	if (!page)
431		return -ENOMEM;
432	if (unlikely(IS_ERR(page))) {
433		if (PTR_ERR(page) == -ENODATA)
434			/* Hole? No need to truncate */
435			return 0;
436		else
437			return PTR_ERR(page);
438	} else
439		BUG_ON(!PageUptodate(page));
440	kaddr = kmap_atomic(page, KM_USER0);
441	memset(kaddr + offset, 0, length);
442	kunmap_atomic(kaddr, KM_USER0);
443
444	flush_dcache_page(page);
445	return 0;
446}
447EXPORT_SYMBOL_GPL(xip_truncate_page);
448