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 <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  */
  26 static void
  27 do_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
 105 no_xip_page:
 106                 /* Did not get the page. Report it */
 107                 desc->error = -EIO;
 108                 goto out;
 109         }
 110
 111 out:
 112         *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
 113         if (filp)
 114                 file_accessed(filp);
 115 }
 116
 117 ssize_t
 118 xip_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 }
 138 EXPORT_SYMBOL_GPL(xip_file_read);
 139
 140 ssize_t
 141 xip_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 }
 160 EXPORT_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  */
 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
 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  */
 210 static struct page *
 211 xip_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
 259 static struct vm_operations_struct xip_file_vm_ops = {
 260         .nopage         = xip_file_nopage,
 261 };
 262
 263 int 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 }
 271 EXPORT_SYMBOL_GPL(xip_file_mmap);
 272
 273 static 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
 355 ssize_t
 356 xip_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 }
 400 EXPORT_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  */
 407 int
 408 xip_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 }
 447 EXPORT_SYMBOL_GPL(xip_truncate_page);