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/module.h>
  14 #include <linux/uio.h>
  15 #include <linux/rmap.h>
  16 #include <linux/sched.h>
  17 #include <asm/tlbflush.h>
  18 #include "filemap.h"
  19
  20 /*
  21  * We do use our own empty page to avoid interference with other users
  22  * of ZERO_PAGE(), such as /dev/zero
  23  */
  24 static struct page *__xip_sparse_page;
  25
  26 static struct page *xip_sparse_page(void)
  27 {
  28         if (!__xip_sparse_page) {
  29                 unsigned long zeroes = get_zeroed_page(GFP_HIGHUSER);
  30                 if (zeroes) {
  31                         static DEFINE_SPINLOCK(xip_alloc_lock);
  32                         spin_lock(&xip_alloc_lock);
  33                         if (!__xip_sparse_page)
  34                                 __xip_sparse_page = virt_to_page(zeroes);
  35                         else
  36                                 free_page(zeroes);
  37                         spin_unlock(&xip_alloc_lock);
  38                 }
  39         }
  40         return __xip_sparse_page;
  41 }
  42
  43 /*
  44  * This is a file read routine for execute in place files, and uses
  45  * the mapping->a_ops->get_xip_page() function for the actual low-level
  46  * stuff.
  47  *
  48  * Note the struct file* is not used at all.  It may be NULL.
  49  */
  50 static void
  51 do_xip_mapping_read(struct address_space *mapping,
  52                     struct file_ra_state *_ra,
  53                     struct file *filp,
  54                     loff_t *ppos,
  55                     read_descriptor_t *desc,
  56                     read_actor_t actor)
  57 {
  58         struct inode *inode = mapping->host;
  59         unsigned long index, end_index, offset;
  60         loff_t isize;
  61
  62         BUG_ON(!mapping->a_ops->get_xip_page);
  63
  64         index = *ppos >> PAGE_CACHE_SHIFT;
  65         offset = *ppos & ~PAGE_CACHE_MASK;
  66
  67         isize = i_size_read(inode);
  68         if (!isize)
  69                 goto out;
  70
  71         end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
  72         for (;;) {
  73                 struct page *page;
  74                 unsigned long nr, ret;
  75
  76                 /* nr is the maximum number of bytes to copy from this page */
  77                 nr = PAGE_CACHE_SIZE;
  78                 if (index >= end_index) {
  79                         if (index > end_index)
  80                                 goto out;
  81                         nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
  82                         if (nr <= offset) {
  83                                 goto out;
  84                         }
  85                 }
  86                 nr = nr - offset;
  87
  88                 page = mapping->a_ops->get_xip_page(mapping,
  89                         index*(PAGE_SIZE/512), 0);
  90                 if (!page)
  91                         goto no_xip_page;
  92                 if (unlikely(IS_ERR(page))) {
  93                         if (PTR_ERR(page) == -ENODATA) {
  94                                 /* sparse */
  95                                 page = ZERO_PAGE(0);
  96                         } else {
  97                                 desc->error = PTR_ERR(page);
  98                                 goto out;
  99                         }
 100                 }
 101
 102                 /* If users can be writing to this page using arbitrary
 103                  * virtual addresses, take care about potential aliasing
 104                  * before reading the page on the kernel side.
 105                  */
 106                 if (mapping_writably_mapped(mapping))
 107                         flush_dcache_page(page);
 108
 109                 /*
 110                  * Ok, we have the page, so now we can copy it to user space...
 111                  *
 112                  * The actor routine returns how many bytes were actually used..
 113                  * NOTE! This may not be the same as how much of a user buffer
 114                  * we filled up (we may be padding etc), so we can only update
 115                  * "pos" here (the actor routine has to update the user buffer
 116                  * pointers and the remaining count).
 117                  */
 118                 ret = actor(desc, page, offset, nr);
 119                 offset += ret;
 120                 index += offset >> PAGE_CACHE_SHIFT;
 121                 offset &= ~PAGE_CACHE_MASK;
 122
 123                 if (ret == nr && desc->count)
 124                         continue;
 125                 goto out;
 126
 127 no_xip_page:
 128                 /* Did not get the page. Report it */
 129                 desc->error = -EIO;
 130                 goto out;
 131         }
 132
 133 out:
 134         *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
 135         if (filp)
 136                 file_accessed(filp);
 137 }
 138
 139 ssize_t
 140 xip_file_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
 141 {
 142         read_descriptor_t desc;
 143
 144         if (!access_ok(VERIFY_WRITE, buf, len))
 145                 return -EFAULT;
 146
 147         desc.written = 0;
 148         desc.arg.buf = buf;
 149         desc.count = len;
 150         desc.error = 0;
 151
 152         do_xip_mapping_read(filp->f_mapping, &filp->f_ra, filp,
 153                             ppos, &desc, file_read_actor);
 154
 155         if (desc.written)
 156                 return desc.written;
 157         else
 158                 return desc.error;
 159 }
 160 EXPORT_SYMBOL_GPL(xip_file_read);
 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  * __xip_sparse_page when found at pgoff.
 168  */
 169 static 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         spinlock_t *ptl;
 180         struct page *page;
 181
 182         page = __xip_sparse_page;
 183         if (!page)
 184                 return;
 185
 186         spin_lock(&mapping->i_mmap_lock);
 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);
 193                 if (pte) {
 194                         /* Nuke the page table entry. */
 195                         flush_cache_page(vma, address, pte_pfn(*pte));
 196                         pteval = ptep_clear_flush(vma, address, pte);
 197                         page_remove_rmap(page, vma);
 198                         dec_mm_counter(mm, file_rss);
 199                         BUG_ON(pte_dirty(pteval));
 200                         pte_unmap_unlock(pte, ptl);
 201                         page_cache_release(page);
 202                 }
 203         }
 204         spin_unlock(&mapping->i_mmap_lock);
 205 }
 206
 207 /*
 208  * xip_nopage() is invoked via the vma operations vector for a
 209  * mapped memory region to read in file data during a page fault.
 210  *
 211  * This function is derived from filemap_nopage, but used for execute in place
 212  */
 213 static struct page *
 214 xip_file_nopage(struct vm_area_struct * area,
 215                    unsigned long address,
 216                    int *type)
 217 {
 218         struct file *file = area->vm_file;
 219         struct address_space *mapping = file->f_mapping;
 220         struct inode *inode = mapping->host;
 221         struct page *page;
 222         unsigned long size, pgoff, endoff;
 223
 224         pgoff = ((address - area->vm_start) >> PAGE_CACHE_SHIFT)
 225                 + area->vm_pgoff;
 226         endoff = ((area->vm_end - area->vm_start) >> PAGE_CACHE_SHIFT)
 227                 + area->vm_pgoff;
 228
 229         size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 230         if (pgoff >= size)
 231                 return NOPAGE_SIGBUS;
 232
 233         page = mapping->a_ops->get_xip_page(mapping, pgoff*(PAGE_SIZE/512), 0);
 234         if (!IS_ERR(page))
 235                 goto out;
 236         if (PTR_ERR(page) != -ENODATA)
 237                 return NOPAGE_SIGBUS;
 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 NOPAGE_SIGBUS;
 248                 /* unmap page at pgoff from all other vmas */
 249                 __xip_unmap(mapping, pgoff);
 250         } else {
 251                 /* not shared and writable, use xip_sparse_page() */
 252                 page = xip_sparse_page();
 253                 if (!page)
 254                         return NOPAGE_OOM;
 255         }
 256
 257 out:
 258         page_cache_get(page);
 259         return page;
 260 }
 261
 262 static struct vm_operations_struct xip_file_vm_ops = {
 263         .nopage         = xip_file_nopage,
 264 };
 265
 266 int xip_file_mmap(struct file * file, struct vm_area_struct * vma)
 267 {
 268         BUG_ON(!file->f_mapping->a_ops->get_xip_page);
 269
 270         file_accessed(file);
 271         vma->vm_ops = &xip_file_vm_ops;
 272         return 0;
 273 }
 274 EXPORT_SYMBOL_GPL(xip_file_mmap);
 275
 276 static ssize_t
 277 __xip_file_write(struct file *filp, const char __user *buf,
 278                   size_t count, loff_t pos, loff_t *ppos)
 279 {
 280         struct address_space * mapping = filp->f_mapping;
 281         const struct address_space_operations *a_ops = mapping->a_ops;
 282         struct inode    *inode = mapping->host;
 283         long            status = 0;
 284         struct page     *page;
 285         size_t          bytes;
 286         ssize_t         written = 0;
 287
 288         BUG_ON(!mapping->a_ops->get_xip_page);
 289
 290         do {
 291                 unsigned long index;
 292                 unsigned long offset;
 293                 size_t copied;
 294
 295                 offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
 296                 index = pos >> PAGE_CACHE_SHIFT;
 297                 bytes = PAGE_CACHE_SIZE - offset;
 298                 if (bytes > count)
 299                         bytes = count;
 300
 301                 /*
 302                  * Bring in the user page that we will copy from _first_.
 303                  * Otherwise there's a nasty deadlock on copying from the
 304                  * same page as we're writing to, without it being marked
 305                  * up-to-date.
 306                  */
 307                 fault_in_pages_readable(buf, bytes);
 308
 309                 page = a_ops->get_xip_page(mapping,
 310                                            index*(PAGE_SIZE/512), 0);
 311                 if (IS_ERR(page) && (PTR_ERR(page) == -ENODATA)) {
 312                         /* we allocate a new page unmap it */
 313                         page = a_ops->get_xip_page(mapping,
 314                                                    index*(PAGE_SIZE/512), 1);
 315                         if (!IS_ERR(page))
 316                                 /* unmap page at pgoff from all other vmas */
 317                                 __xip_unmap(mapping, index);
 318                 }
 319
 320                 if (IS_ERR(page)) {
 321                         status = PTR_ERR(page);
 322                         break;
 323                 }
 324
 325                 copied = filemap_copy_from_user(page, offset, buf, bytes);
 326                 flush_dcache_page(page);
 327                 if (likely(copied > 0)) {
 328                         status = copied;
 329
 330                         if (status >= 0) {
 331                                 written += status;
 332                                 count -= status;
 333                                 pos += status;
 334                                 buf += status;
 335                         }
 336                 }
 337                 if (unlikely(copied != bytes))
 338                         if (status >= 0)
 339                                 status = -EFAULT;
 340                 if (status < 0)
 341                         break;
 342         } while (count);
 343         *ppos = pos;
 344         /*
 345          * No need to use i_size_read() here, the i_size
 346          * cannot change under us because we hold i_mutex.
 347          */
 348         if (pos > inode->i_size) {
 349                 i_size_write(inode, pos);
 350                 mark_inode_dirty(inode);
 351         }
 352
 353         return written ? written : status;
 354 }
 355
 356 ssize_t
 357 xip_file_write(struct file *filp, const char __user *buf, size_t len,
 358                loff_t *ppos)
 359 {
 360         struct address_space *mapping = filp->f_mapping;
 361         struct inode *inode = mapping->host;
 362         size_t count;
 363         loff_t pos;
 364         ssize_t ret;
 365
 366         mutex_lock(&inode->i_mutex);
 367
 368         if (!access_ok(VERIFY_READ, buf, len)) {
 369                 ret=-EFAULT;
 370                 goto out_up;
 371         }
 372
 373         pos = *ppos;
 374         count = len;
 375
 376         vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
 377
 378         /* We can write back this queue in page reclaim */
 379         current->backing_dev_info = mapping->backing_dev_info;
 380
 381         ret = generic_write_checks(filp, &pos, &count, S_ISBLK(inode->i_mode));
 382         if (ret)
 383                 goto out_backing;
 384         if (count == 0)
 385                 goto out_backing;
 386
 387         ret = remove_suid(filp->f_path.dentry);
 388         if (ret)
 389                 goto out_backing;
 390
 391         file_update_time(filp);
 392
 393         ret = __xip_file_write (filp, buf, count, pos, ppos);
 394
 395  out_backing:
 396         current->backing_dev_info = NULL;
 397  out_up:
 398         mutex_unlock(&inode->i_mutex);
 399         return ret;
 400 }
 401 EXPORT_SYMBOL_GPL(xip_file_write);
 402
 403 /*
 404  * truncate a page used for execute in place
 405  * functionality is analog to block_truncate_page but does use get_xip_page
 406  * to get the page instead of page cache
 407  */
 408 int
 409 xip_truncate_page(struct address_space *mapping, loff_t from)
 410 {
 411         pgoff_t index = from >> PAGE_CACHE_SHIFT;
 412         unsigned offset = from & (PAGE_CACHE_SIZE-1);
 413         unsigned blocksize;
 414         unsigned length;
 415         struct page *page;
 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         }
 439         zero_user_page(page, offset, length, KM_USER0);
 440         return 0;
 441 }
 442 EXPORT_SYMBOL_GPL(xip_truncate_page);