filemap_xip.c revision 870f481793b585323fbda3e87c54efc116f46351 
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 = ZERO_PAGE(0);
72			} else {
73				desc->error = PTR_ERR(page);
74				goto out;
75			}
76		}
77
78		/* If users can be writing to this page using arbitrary
79		 * virtual addresses, take care about potential aliasing
80		 * before reading the page on the kernel side.
81		 */
82		if (mapping_writably_mapped(mapping))
83			flush_dcache_page(page);
84
85		/*
86		 * Ok, we have the page, so now we can copy it to user space...
87		 *
88		 * The actor routine returns how many bytes were actually used..
89		 * NOTE! This may not be the same as how much of a user buffer
90		 * we filled up (we may be padding etc), so we can only update
91		 * "pos" here (the actor routine has to update the user buffer
92		 * pointers and the remaining count).
93		 */
94		ret = actor(desc, page, offset, nr);
95		offset += ret;
96		index += offset >> PAGE_CACHE_SHIFT;
97		offset &= ~PAGE_CACHE_MASK;
98
99		if (ret == nr && desc->count)
100			continue;
101		goto out;
102
103no_xip_page:
104		/* Did not get the page. Report it */
105		desc->error = -EIO;
106		goto out;
107	}
108
109out:
110	*ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
111	if (filp)
112		file_accessed(filp);
113}
114
115ssize_t
116xip_file_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
117{
118	read_descriptor_t desc;
119
120	if (!access_ok(VERIFY_WRITE, buf, len))
121		return -EFAULT;
122
123	desc.written = 0;
124	desc.arg.buf = buf;
125	desc.count = len;
126	desc.error = 0;
127
128	do_xip_mapping_read(filp->f_mapping, &filp->f_ra, filp,
129			    ppos, &desc, file_read_actor);
130
131	if (desc.written)
132		return desc.written;
133	else
134		return desc.error;
135}
136EXPORT_SYMBOL_GPL(xip_file_read);
137
138ssize_t
139xip_file_sendfile(struct file *in_file, loff_t *ppos,
140	     size_t count, read_actor_t actor, void *target)
141{
142	read_descriptor_t desc;
143
144	if (!count)
145		return 0;
146
147	desc.written = 0;
148	desc.count = count;
149	desc.arg.data = target;
150	desc.error = 0;
151
152	do_xip_mapping_read(in_file->f_mapping, &in_file->f_ra, in_file,
153			    ppos, &desc, actor);
154	if (desc.written)
155		return desc.written;
156	return desc.error;
157}
158EXPORT_SYMBOL_GPL(xip_file_sendfile);
159
160/*
161 * __xip_unmap is invoked from xip_unmap and
162 * xip_write
163 *
164 * This function walks all vmas of the address_space and unmaps the
165 * ZERO_PAGE when found at pgoff. Should it go in rmap.c?
166 */
167static void
168__xip_unmap (struct address_space * mapping,
169		     unsigned long pgoff)
170{
171	struct vm_area_struct *vma;
172	struct mm_struct *mm;
173	struct prio_tree_iter iter;
174	unsigned long address;
175	pte_t *pte;
176	pte_t pteval;
177	spinlock_t *ptl;
178	struct page *page;
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		page = ZERO_PAGE(address);
187		pte = page_check_address(page, mm, address, &ptl);
188		if (pte) {
189			/* Nuke the page table entry. */
190			flush_cache_page(vma, address, pte_pfn(*pte));
191			pteval = ptep_clear_flush(vma, address, pte);
192			page_remove_rmap(page);
193			dec_mm_counter(mm, file_rss);
194			BUG_ON(pte_dirty(pteval));
195			pte_unmap_unlock(pte, ptl);
196			page_cache_release(page);
197		}
198	}
199	spin_unlock(&mapping->i_mmap_lock);
200}
201
202/*
203 * xip_nopage() is invoked via the vma operations vector for a
204 * mapped memory region to read in file data during a page fault.
205 *
206 * This function is derived from filemap_nopage, but used for execute in place
207 */
208static struct page *
209xip_file_nopage(struct vm_area_struct * area,
210		   unsigned long address,
211		   int *type)
212{
213	struct file *file = area->vm_file;
214	struct address_space *mapping = file->f_mapping;
215	struct inode *inode = mapping->host;
216	struct page *page;
217	unsigned long size, pgoff, endoff;
218
219	pgoff = ((address - area->vm_start) >> PAGE_CACHE_SHIFT)
220		+ area->vm_pgoff;
221	endoff = ((area->vm_end - area->vm_start) >> PAGE_CACHE_SHIFT)
222		+ area->vm_pgoff;
223
224	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
225	if (pgoff >= size) {
226		return NULL;
227	}
228
229	page = mapping->a_ops->get_xip_page(mapping, pgoff*(PAGE_SIZE/512), 0);
230	if (!IS_ERR(page)) {
231		goto out;
232	}
233	if (PTR_ERR(page) != -ENODATA)
234		return NULL;
235
236	/* sparse block */
237	if ((area->vm_flags & (VM_WRITE | VM_MAYWRITE)) &&
238	    (area->vm_flags & (VM_SHARED| VM_MAYSHARE)) &&
239	    (!(mapping->host->i_sb->s_flags & MS_RDONLY))) {
240		/* maybe shared writable, allocate new block */
241		page = mapping->a_ops->get_xip_page (mapping,
242			pgoff*(PAGE_SIZE/512), 1);
243		if (IS_ERR(page))
244			return NULL;
245		/* unmap page at pgoff from all other vmas */
246		__xip_unmap(mapping, pgoff);
247	} else {
248		/* not shared and writable, use ZERO_PAGE() */
249		page = ZERO_PAGE(address);
250	}
251
252out:
253	page_cache_get(page);
254	return page;
255}
256
257static struct vm_operations_struct xip_file_vm_ops = {
258	.nopage         = xip_file_nopage,
259};
260
261int xip_file_mmap(struct file * file, struct vm_area_struct * vma)
262{
263	BUG_ON(!file->f_mapping->a_ops->get_xip_page);
264
265	file_accessed(file);
266	vma->vm_ops = &xip_file_vm_ops;
267	return 0;
268}
269EXPORT_SYMBOL_GPL(xip_file_mmap);
270
271static ssize_t
272__xip_file_write(struct file *filp, const char __user *buf,
273		  size_t count, loff_t pos, loff_t *ppos)
274{
275	struct address_space * mapping = filp->f_mapping;
276	struct address_space_operations *a_ops = mapping->a_ops;
277	struct inode 	*inode = mapping->host;
278	long		status = 0;
279	struct page	*page;
280	size_t		bytes;
281	ssize_t		written = 0;
282
283	BUG_ON(!mapping->a_ops->get_xip_page);
284
285	do {
286		unsigned long index;
287		unsigned long offset;
288		size_t copied;
289
290		offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
291		index = pos >> PAGE_CACHE_SHIFT;
292		bytes = PAGE_CACHE_SIZE - offset;
293		if (bytes > count)
294			bytes = count;
295
296		/*
297		 * Bring in the user page that we will copy from _first_.
298		 * Otherwise there's a nasty deadlock on copying from the
299		 * same page as we're writing to, without it being marked
300		 * up-to-date.
301		 */
302		fault_in_pages_readable(buf, bytes);
303
304		page = a_ops->get_xip_page(mapping,
305					   index*(PAGE_SIZE/512), 0);
306		if (IS_ERR(page) && (PTR_ERR(page) == -ENODATA)) {
307			/* we allocate a new page unmap it */
308			page = a_ops->get_xip_page(mapping,
309						   index*(PAGE_SIZE/512), 1);
310			if (!IS_ERR(page))
311				/* unmap page at pgoff from all other vmas */
312				__xip_unmap(mapping, index);
313		}
314
315		if (IS_ERR(page)) {
316			status = PTR_ERR(page);
317			break;
318		}
319
320		copied = filemap_copy_from_user(page, offset, buf, bytes);
321		flush_dcache_page(page);
322		if (likely(copied > 0)) {
323			status = copied;
324
325			if (status >= 0) {
326				written += status;
327				count -= status;
328				pos += status;
329				buf += status;
330			}
331		}
332		if (unlikely(copied != bytes))
333			if (status >= 0)
334				status = -EFAULT;
335		if (status < 0)
336			break;
337	} while (count);
338	*ppos = pos;
339	/*
340	 * No need to use i_size_read() here, the i_size
341	 * cannot change under us because we hold i_mutex.
342	 */
343	if (pos > inode->i_size) {
344		i_size_write(inode, pos);
345		mark_inode_dirty(inode);
346	}
347
348	return written ? written : status;
349}
350
351ssize_t
352xip_file_write(struct file *filp, const char __user *buf, size_t len,
353	       loff_t *ppos)
354{
355	struct address_space *mapping = filp->f_mapping;
356	struct inode *inode = mapping->host;
357	size_t count;
358	loff_t pos;
359	ssize_t ret;
360
361	mutex_lock(&inode->i_mutex);
362
363	if (!access_ok(VERIFY_READ, buf, len)) {
364		ret=-EFAULT;
365		goto out_up;
366	}
367
368	pos = *ppos;
369	count = len;
370
371	vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
372
373	/* We can write back this queue in page reclaim */
374	current->backing_dev_info = mapping->backing_dev_info;
375
376	ret = generic_write_checks(filp, &pos, &count, S_ISBLK(inode->i_mode));
377	if (ret)
378		goto out_backing;
379	if (count == 0)
380		goto out_backing;
381
382	ret = remove_suid(filp->f_dentry);
383	if (ret)
384		goto out_backing;
385
386	file_update_time(filp);
387
388	ret = __xip_file_write (filp, buf, count, pos, ppos);
389
390 out_backing:
391	current->backing_dev_info = NULL;
392 out_up:
393	mutex_unlock(&inode->i_mutex);
394	return ret;
395}
396EXPORT_SYMBOL_GPL(xip_file_write);
397
398/*
399 * truncate a page used for execute in place
400 * functionality is analog to block_truncate_page but does use get_xip_page
401 * to get the page instead of page cache
402 */
403int
404xip_truncate_page(struct address_space *mapping, loff_t from)
405{
406	pgoff_t index = from >> PAGE_CACHE_SHIFT;
407	unsigned offset = from & (PAGE_CACHE_SIZE-1);
408	unsigned blocksize;
409	unsigned length;
410	struct page *page;
411	void *kaddr;
412
413	BUG_ON(!mapping->a_ops->get_xip_page);
414
415	blocksize = 1 << mapping->host->i_blkbits;
416	length = offset & (blocksize - 1);
417
418	/* Block boundary? Nothing to do */
419	if (!length)
420		return 0;
421
422	length = blocksize - length;
423
424	page = mapping->a_ops->get_xip_page(mapping,
425					    index*(PAGE_SIZE/512), 0);
426	if (!page)
427		return -ENOMEM;
428	if (unlikely(IS_ERR(page))) {
429		if (PTR_ERR(page) == -ENODATA)
430			/* Hole? No need to truncate */
431			return 0;
432		else
433			return PTR_ERR(page);
434	}
435	kaddr = kmap_atomic(page, KM_USER0);
436	memset(kaddr + offset, 0, length);
437	kunmap_atomic(kaddr, KM_USER0);
438
439	flush_dcache_page(page);
440	return 0;
441}
442EXPORT_SYMBOL_GPL(xip_truncate_page);
443