Root/mm/filemap_xip.c

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 */
28static DEFINE_MUTEX(xip_sparse_mutex);
29static seqcount_t xip_sparse_seq = SEQCNT_ZERO;
30static struct page *__xip_sparse_page;
31
32/* called under xip_sparse_mutex */
33static 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 */
51static ssize_t
52do_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
138out:
139    *ppos = pos + copied;
140    if (filp)
141        file_accessed(filp);
142
143    return (copied ? copied : error);
144}
145
146ssize_t
147xip_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}
155EXPORT_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 */
164static void
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
185retry:
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 */
221static 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? */
233again:
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
261found:
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;
297out:
298        write_seqcount_end(&xip_sparse_seq);
299        mutex_unlock(&xip_sparse_mutex);
300
301        return ret;
302    }
303}
304
305static const struct vm_operations_struct xip_file_vm_ops = {
306    .fault = xip_file_fault,
307    .page_mkwrite = filemap_page_mkwrite,
308};
309
310int xip_file_mmap(struct file * file, struct vm_area_struct * vma)
311{
312    BUG_ON(!file->f_mapping->a_ops->get_xip_mem);
313
314    file_accessed(file);
315    vma->vm_ops = &xip_file_vm_ops;
316    vma->vm_flags |= VM_CAN_NONLINEAR | VM_MIXEDMAP;
317    return 0;
318}
319EXPORT_SYMBOL_GPL(xip_file_mmap);
320
321static ssize_t
322__xip_file_write(struct file *filp, const char __user *buf,
323          size_t count, loff_t pos, loff_t *ppos)
324{
325    struct address_space * mapping = filp->f_mapping;
326    const struct address_space_operations *a_ops = mapping->a_ops;
327    struct inode *inode = mapping->host;
328    long status = 0;
329    size_t bytes;
330    ssize_t written = 0;
331
332    BUG_ON(!mapping->a_ops->get_xip_mem);
333
334    do {
335        unsigned long index;
336        unsigned long offset;
337        size_t copied;
338        void *xip_mem;
339        unsigned long xip_pfn;
340
341        offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
342        index = pos >> PAGE_CACHE_SHIFT;
343        bytes = PAGE_CACHE_SIZE - offset;
344        if (bytes > count)
345            bytes = count;
346
347        status = a_ops->get_xip_mem(mapping, index, 0,
348                        &xip_mem, &xip_pfn);
349        if (status == -ENODATA) {
350            /* we allocate a new page unmap it */
351            mutex_lock(&xip_sparse_mutex);
352            status = a_ops->get_xip_mem(mapping, index, 1,
353                            &xip_mem, &xip_pfn);
354            mutex_unlock(&xip_sparse_mutex);
355            if (!status)
356                /* unmap page at pgoff from all other vmas */
357                __xip_unmap(mapping, index);
358        }
359
360        if (status)
361            break;
362
363        copied = bytes -
364            __copy_from_user_nocache(xip_mem + offset, buf, bytes);
365
366        if (likely(copied > 0)) {
367            status = copied;
368
369            if (status >= 0) {
370                written += status;
371                count -= status;
372                pos += status;
373                buf += status;
374            }
375        }
376        if (unlikely(copied != bytes))
377            if (status >= 0)
378                status = -EFAULT;
379        if (status < 0)
380            break;
381    } while (count);
382    *ppos = pos;
383    /*
384     * No need to use i_size_read() here, the i_size
385     * cannot change under us because we hold i_mutex.
386     */
387    if (pos > inode->i_size) {
388        i_size_write(inode, pos);
389        mark_inode_dirty(inode);
390    }
391
392    return written ? written : status;
393}
394
395ssize_t
396xip_file_write(struct file *filp, const char __user *buf, size_t len,
397           loff_t *ppos)
398{
399    struct address_space *mapping = filp->f_mapping;
400    struct inode *inode = mapping->host;
401    size_t count;
402    loff_t pos;
403    ssize_t ret;
404
405    sb_start_write(inode->i_sb);
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    sb_end_write(inode->i_sb);
441    return ret;
442}
443EXPORT_SYMBOL_GPL(xip_file_write);
444
445/*
446 * truncate a page used for execute in place
447 * functionality is analog to block_truncate_page but does use get_xip_mem
448 * to get the page instead of page cache
449 */
450int
451xip_truncate_page(struct address_space *mapping, loff_t from)
452{
453    pgoff_t index = from >> PAGE_CACHE_SHIFT;
454    unsigned offset = from & (PAGE_CACHE_SIZE-1);
455    unsigned blocksize;
456    unsigned length;
457    void *xip_mem;
458    unsigned long xip_pfn;
459    int err;
460
461    BUG_ON(!mapping->a_ops->get_xip_mem);
462
463    blocksize = 1 << mapping->host->i_blkbits;
464    length = offset & (blocksize - 1);
465
466    /* Block boundary? Nothing to do */
467    if (!length)
468        return 0;
469
470    length = blocksize - length;
471
472    err = mapping->a_ops->get_xip_mem(mapping, index, 0,
473                        &xip_mem, &xip_pfn);
474    if (unlikely(err)) {
475        if (err == -ENODATA)
476            /* Hole? No need to truncate */
477            return 0;
478        else
479            return err;
480    }
481    memset(xip_mem + offset, 0, length);
482    return 0;
483}
484EXPORT_SYMBOL_GPL(xip_truncate_page);
485

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