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   1 /*
   2  *  linux/mm/nommu.c
   3  *
   4  *  Replacement code for mm functions to support CPU's that don't
   5  *  have any form of memory management unit (thus no virtual memory).
   6  *
   7  *  See Documentation/nommu-mmap.txt
   8  *
   9  *  Copyright (c) 2004-2005 David Howells <dhowells@redhat.com>
  10  *  Copyright (c) 2000-2003 David McCullough <davidm@snapgear.com>
  11  *  Copyright (c) 2000-2001 D Jeff Dionne <jeff@uClinux.org>
  12  *  Copyright (c) 2002      Greg Ungerer <gerg@snapgear.com>
  13  *  Copyright (c) 2007      Paul Mundt <lethal@linux-sh.org>
  14  */
  15
  16 #include <linux/module.h>
  17 #include <linux/mm.h>
  18 #include <linux/mman.h>
  19 #include <linux/swap.h>
  20 #include <linux/file.h>
  21 #include <linux/highmem.h>
  22 #include <linux/pagemap.h>
  23 #include <linux/slab.h>
  24 #include <linux/vmalloc.h>
  25 #include <linux/ptrace.h>
  26 #include <linux/blkdev.h>
  27 #include <linux/backing-dev.h>
  28 #include <linux/mount.h>
  29 #include <linux/personality.h>
  30 #include <linux/security.h>
  31 #include <linux/syscalls.h>
  32
  33 #include <asm/uaccess.h>
  34 #include <asm/tlb.h>
  35 #include <asm/tlbflush.h>
  36
  37 void *high_memory;
  38 struct page *mem_map;
  39 unsigned long max_mapnr;
  40 unsigned long num_physpages;
  41 unsigned long askedalloc, realalloc;
  42 atomic_t vm_committed_space = ATOMIC_INIT(0);
  43 int sysctl_overcommit_memory = OVERCOMMIT_GUESS; /* heuristic overcommit */
  44 int sysctl_overcommit_ratio = 50; /* default is 50% */
  45 int sysctl_max_map_count = DEFAULT_MAX_MAP_COUNT;
  46 int heap_stack_gap = 0;
  47
  48 EXPORT_SYMBOL(mem_map);
  49 EXPORT_SYMBOL(num_physpages);
  50
  51 /* list of shareable VMAs */
  52 struct rb_root nommu_vma_tree = RB_ROOT;
  53 DECLARE_RWSEM(nommu_vma_sem);
  54
  55 struct vm_operations_struct generic_file_vm_ops = {
  56 };
  57
  58 /*
  59  * Handle all mappings that got truncated by a "truncate()"
  60  * system call.
  61  *
  62  * NOTE! We have to be ready to update the memory sharing
  63  * between the file and the memory map for a potential last
  64  * incomplete page.  Ugly, but necessary.
  65  */
  66 int vmtruncate(struct inode *inode, loff_t offset)
  67 {
  68         struct address_space *mapping = inode->i_mapping;
  69         unsigned long limit;
  70
  71         if (inode->i_size < offset)
  72                 goto do_expand;
  73         i_size_write(inode, offset);
  74
  75         truncate_inode_pages(mapping, offset);
  76         goto out_truncate;
  77
  78 do_expand:
  79         limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
  80         if (limit != RLIM_INFINITY && offset > limit)
  81                 goto out_sig;
  82         if (offset > inode->i_sb->s_maxbytes)
  83                 goto out;
  84         i_size_write(inode, offset);
  85
  86 out_truncate:
  87         if (inode->i_op && inode->i_op->truncate)
  88                 inode->i_op->truncate(inode);
  89         return 0;
  90 out_sig:
  91         send_sig(SIGXFSZ, current, 0);
  92 out:
  93         return -EFBIG;
  94 }
  95
  96 EXPORT_SYMBOL(vmtruncate);
  97
  98 /*
  99  * Return the total memory allocated for this pointer, not
 100  * just what the caller asked for.
 101  *
 102  * Doesn't have to be accurate, i.e. may have races.
 103  */
 104 unsigned int kobjsize(const void *objp)
 105 {
 106         struct page *page;
 107
 108         if (!objp || !((page = virt_to_page(objp))))
 109                 return 0;
 110
 111         if (PageSlab(page))
 112                 return ksize(objp);
 113
 114         BUG_ON(page->index < 0);
 115         BUG_ON(page->index >= MAX_ORDER);
 116
 117         return (PAGE_SIZE << page->index);
 118 }
 119
 120 /*
 121  * get a list of pages in an address range belonging to the specified process
 122  * and indicate the VMA that covers each page
 123  * - this is potentially dodgy as we may end incrementing the page count of a
 124  *   slab page or a secondary page from a compound page
 125  * - don't permit access to VMAs that don't support it, such as I/O mappings
 126  */
 127 int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 128         unsigned long start, int len, int write, int force,
 129         struct page **pages, struct vm_area_struct **vmas)
 130 {
 131         struct vm_area_struct *vma;
 132         unsigned long vm_flags;
 133         int i;
 134
 135         /* calculate required read or write permissions.
 136          * - if 'force' is set, we only require the "MAY" flags.
 137          */
 138         vm_flags  = write ? (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
 139         vm_flags &= force ? (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
 140
 141         for (i = 0; i < len; i++) {
 142                 vma = find_vma(mm, start);
 143                 if (!vma)
 144                         goto finish_or_fault;
 145
 146                 /* protect what we can, including chardevs */
 147                 if (vma->vm_flags & (VM_IO | VM_PFNMAP) ||
 148                     !(vm_flags & vma->vm_flags))
 149                         goto finish_or_fault;
 150
 151                 if (pages) {
 152                         pages[i] = virt_to_page(start);
 153                         if (pages[i])
 154                                 page_cache_get(pages[i]);
 155                 }
 156                 if (vmas)
 157                         vmas[i] = vma;
 158                 start += PAGE_SIZE;
 159         }
 160
 161         return i;
 162
 163 finish_or_fault:
 164         return i ? : -EFAULT;
 165 }
 166 EXPORT_SYMBOL(get_user_pages);
 167
 168 DEFINE_RWLOCK(vmlist_lock);
 169 struct vm_struct *vmlist;
 170
 171 void vfree(const void *addr)
 172 {
 173         kfree(addr);
 174 }
 175 EXPORT_SYMBOL(vfree);
 176
 177 void *__vmalloc(unsigned long size, gfp_t gfp_mask, pgprot_t prot)
 178 {
 179         /*
 180          *  You can't specify __GFP_HIGHMEM with kmalloc() since kmalloc()
 181          * returns only a logical address.
 182          */
 183         return kmalloc(size, (gfp_mask | __GFP_COMP) & ~__GFP_HIGHMEM);
 184 }
 185 EXPORT_SYMBOL(__vmalloc);
 186
 187 void *vmalloc_user(unsigned long size)
 188 {
 189         void *ret;
 190
 191         ret = __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
 192                         PAGE_KERNEL);
 193         if (ret) {
 194                 struct vm_area_struct *vma;
 195
 196                 down_write(&current->mm->mmap_sem);
 197                 vma = find_vma(current->mm, (unsigned long)ret);
 198                 if (vma)
 199                         vma->vm_flags |= VM_USERMAP;
 200                 up_write(&current->mm->mmap_sem);
 201         }
 202
 203         return ret;
 204 }
 205 EXPORT_SYMBOL(vmalloc_user);
 206
 207 struct page *vmalloc_to_page(const void *addr)
 208 {
 209         return virt_to_page(addr);
 210 }
 211 EXPORT_SYMBOL(vmalloc_to_page);
 212
 213 unsigned long vmalloc_to_pfn(const void *addr)
 214 {
 215         return page_to_pfn(virt_to_page(addr));
 216 }
 217 EXPORT_SYMBOL(vmalloc_to_pfn);
 218
 219 long vread(char *buf, char *addr, unsigned long count)
 220 {
 221         memcpy(buf, addr, count);
 222         return count;
 223 }
 224
 225 long vwrite(char *buf, char *addr, unsigned long count)
 226 {
 227         /* Don't allow overflow */
 228         if ((unsigned long) addr + count < count)
 229                 count = -(unsigned long) addr;
 230
 231         memcpy(addr, buf, count);
 232         return(count);
 233 }
 234
 235 /*
 236  *      vmalloc  -  allocate virtually continguos memory
 237  *
 238  *      @size:          allocation size
 239  *
 240  *      Allocate enough pages to cover @size from the page level
 241  *      allocator and map them into continguos kernel virtual space.
 242  *
 243  *      For tight control over page level allocator and protection flags
 244  *      use __vmalloc() instead.
 245  */
 246 void *vmalloc(unsigned long size)
 247 {
 248        return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL);
 249 }
 250 EXPORT_SYMBOL(vmalloc);
 251
 252 void *vmalloc_node(unsigned long size, int node)
 253 {
 254         return vmalloc(size);
 255 }
 256 EXPORT_SYMBOL(vmalloc_node);
 257
 258 /**
 259  * vmalloc_32  -  allocate virtually contiguous memory (32bit addressable)
 260  *      @size:          allocation size
 261  *
 262  *      Allocate enough 32bit PA addressable pages to cover @size from the
 263  *      page level allocator and map them into continguos kernel virtual space.
 264  */
 265 void *vmalloc_32(unsigned long size)
 266 {
 267         return __vmalloc(size, GFP_KERNEL, PAGE_KERNEL);
 268 }
 269 EXPORT_SYMBOL(vmalloc_32);
 270
 271 /**
 272  * vmalloc_32_user - allocate zeroed virtually contiguous 32bit memory
 273  *      @size:          allocation size
 274  *
 275  * The resulting memory area is 32bit addressable and zeroed so it can be
 276  * mapped to userspace without leaking data.
 277  *
 278  * VM_USERMAP is set on the corresponding VMA so that subsequent calls to
 279  * remap_vmalloc_range() are permissible.
 280  */
 281 void *vmalloc_32_user(unsigned long size)
 282 {
 283         /*
 284          * We'll have to sort out the ZONE_DMA bits for 64-bit,
 285          * but for now this can simply use vmalloc_user() directly.
 286          */
 287         return vmalloc_user(size);
 288 }
 289 EXPORT_SYMBOL(vmalloc_32_user);
 290
 291 void *vmap(struct page **pages, unsigned int count, unsigned long flags, pgprot_t prot)
 292 {
 293         BUG();
 294         return NULL;
 295 }
 296 EXPORT_SYMBOL(vmap);
 297
 298 void vunmap(const void *addr)
 299 {
 300         BUG();
 301 }
 302 EXPORT_SYMBOL(vunmap);
 303
 304 /*
 305  * Implement a stub for vmalloc_sync_all() if the architecture chose not to
 306  * have one.
 307  */
 308 void  __attribute__((weak)) vmalloc_sync_all(void)
 309 {
 310 }
 311
 312 int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
 313                    struct page *page)
 314 {
 315         return -EINVAL;
 316 }
 317 EXPORT_SYMBOL(vm_insert_page);
 318
 319 /*
 320  *  sys_brk() for the most part doesn't need the global kernel
 321  *  lock, except when an application is doing something nasty
 322  *  like trying to un-brk an area that has already been mapped
 323  *  to a regular file.  in this case, the unmapping will need
 324  *  to invoke file system routines that need the global lock.
 325  */
 326 asmlinkage unsigned long sys_brk(unsigned long brk)
 327 {
 328         struct mm_struct *mm = current->mm;
 329
 330         if (brk < mm->start_brk || brk > mm->context.end_brk)
 331                 return mm->brk;
 332
 333         if (mm->brk == brk)
 334                 return mm->brk;
 335
 336         /*
 337          * Always allow shrinking brk
 338          */
 339         if (brk <= mm->brk) {
 340                 mm->brk = brk;
 341                 return brk;
 342         }
 343
 344         /*
 345          * Ok, looks good - let it rip.
 346          */
 347         return mm->brk = brk;
 348 }
 349
 350 #ifdef DEBUG
 351 static void show_process_blocks(void)
 352 {
 353         struct vm_list_struct *vml;
 354
 355         printk("Process blocks %d:", current->pid);
 356
 357         for (vml = &current->mm->context.vmlist; vml; vml = vml->next) {
 358                 printk(" %p: %p", vml, vml->vma);
 359                 if (vml->vma)
 360                         printk(" (%d @%lx #%d)",
 361                                kobjsize((void *) vml->vma->vm_start),
 362                                vml->vma->vm_start,
 363                                atomic_read(&vml->vma->vm_usage));
 364                 printk(vml->next ? " ->" : ".\n");
 365         }
 366 }
 367 #endif /* DEBUG */
 368
 369 /*
 370  * add a VMA into a process's mm_struct in the appropriate place in the list
 371  * - should be called with mm->mmap_sem held writelocked
 372  */
 373 static void add_vma_to_mm(struct mm_struct *mm, struct vm_list_struct *vml)
 374 {
 375         struct vm_list_struct **ppv;
 376
 377         for (ppv = &current->mm->context.vmlist; *ppv; ppv = &(*ppv)->next)
 378                 if ((*ppv)->vma->vm_start > vml->vma->vm_start)
 379                         break;
 380
 381         vml->next = *ppv;
 382         *ppv = vml;
 383 }
 384
 385 /*
 386  * look up the first VMA in which addr resides, NULL if none
 387  * - should be called with mm->mmap_sem at least held readlocked
 388  */
 389 struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
 390 {
 391         struct vm_list_struct *loop, *vml;
 392
 393         /* search the vm_start ordered list */
 394         vml = NULL;
 395         for (loop = mm->context.vmlist; loop; loop = loop->next) {
 396                 if (loop->vma->vm_start > addr)
 397                         break;
 398                 vml = loop;
 399         }
 400
 401         if (vml && vml->vma->vm_end > addr)
 402                 return vml->vma;
 403
 404         return NULL;
 405 }
 406 EXPORT_SYMBOL(find_vma);
 407
 408 /*
 409  * find a VMA
 410  * - we don't extend stack VMAs under NOMMU conditions
 411  */
 412 struct vm_area_struct *find_extend_vma(struct mm_struct *mm, unsigned long addr)
 413 {
 414         return find_vma(mm, addr);
 415 }
 416
 417 int expand_stack(struct vm_area_struct *vma, unsigned long address)
 418 {
 419         return -ENOMEM;
 420 }
 421
 422 /*
 423  * look up the first VMA exactly that exactly matches addr
 424  * - should be called with mm->mmap_sem at least held readlocked
 425  */
 426 static inline struct vm_area_struct *find_vma_exact(struct mm_struct *mm,
 427                                                     unsigned long addr)
 428 {
 429         struct vm_list_struct *vml;
 430
 431         /* search the vm_start ordered list */
 432         for (vml = mm->context.vmlist; vml; vml = vml->next) {
 433                 if (vml->vma->vm_start == addr)
 434                         return vml->vma;
 435                 if (vml->vma->vm_start > addr)
 436                         break;
 437         }
 438
 439         return NULL;
 440 }
 441
 442 /*
 443  * find a VMA in the global tree
 444  */
 445 static inline struct vm_area_struct *find_nommu_vma(unsigned long start)
 446 {
 447         struct vm_area_struct *vma;
 448         struct rb_node *n = nommu_vma_tree.rb_node;
 449
 450         while (n) {
 451                 vma = rb_entry(n, struct vm_area_struct, vm_rb);
 452
 453                 if (start < vma->vm_start)
 454                         n = n->rb_left;
 455                 else if (start > vma->vm_start)
 456                         n = n->rb_right;
 457                 else
 458                         return vma;
 459         }
 460
 461         return NULL;
 462 }
 463
 464 /*
 465  * add a VMA in the global tree
 466  */
 467 static void add_nommu_vma(struct vm_area_struct *vma)
 468 {
 469         struct vm_area_struct *pvma;
 470         struct address_space *mapping;
 471         struct rb_node **p = &nommu_vma_tree.rb_node;
 472         struct rb_node *parent = NULL;
 473
 474         /* add the VMA to the mapping */
 475         if (vma->vm_file) {
 476                 mapping = vma->vm_file->f_mapping;
 477
 478                 flush_dcache_mmap_lock(mapping);
 479                 vma_prio_tree_insert(vma, &mapping->i_mmap);
 480                 flush_dcache_mmap_unlock(mapping);
 481         }
 482
 483         /* add the VMA to the master list */
 484         while (*p) {
 485                 parent = *p;
 486                 pvma = rb_entry(parent, struct vm_area_struct, vm_rb);
 487
 488                 if (vma->vm_start < pvma->vm_start) {
 489                         p = &(*p)->rb_left;
 490                 }
 491                 else if (vma->vm_start > pvma->vm_start) {
 492                         p = &(*p)->rb_right;
 493                 }
 494                 else {
 495                         /* mappings are at the same address - this can only
 496                          * happen for shared-mem chardevs and shared file
 497                          * mappings backed by ramfs/tmpfs */
 498                         BUG_ON(!(pvma->vm_flags & VM_SHARED));
 499
 500                         if (vma < pvma)
 501                                 p = &(*p)->rb_left;
 502                         else if (vma > pvma)
 503                                 p = &(*p)->rb_right;
 504                         else
 505                                 BUG();
 506                 }
 507         }
 508
 509         rb_link_node(&vma->vm_rb, parent, p);
 510         rb_insert_color(&vma->vm_rb, &nommu_vma_tree);
 511 }
 512
 513 /*
 514  * delete a VMA from the global list
 515  */
 516 static void delete_nommu_vma(struct vm_area_struct *vma)
 517 {
 518         struct address_space *mapping;
 519
 520         /* remove the VMA from the mapping */
 521         if (vma->vm_file) {
 522                 mapping = vma->vm_file->f_mapping;
 523
 524                 flush_dcache_mmap_lock(mapping);
 525                 vma_prio_tree_remove(vma, &mapping->i_mmap);
 526                 flush_dcache_mmap_unlock(mapping);
 527         }
 528
 529         /* remove from the master list */
 530         rb_erase(&vma->vm_rb, &nommu_vma_tree);
 531 }
 532
 533 /*
 534  * determine whether a mapping should be permitted and, if so, what sort of
 535  * mapping we're capable of supporting
 536  */
 537 static int validate_mmap_request(struct file *file,
 538                                  unsigned long addr,
 539                                  unsigned long len,
 540                                  unsigned long prot,
 541                                  unsigned long flags,
 542                                  unsigned long pgoff,
 543                                  unsigned long *_capabilities)
 544 {
 545         unsigned long capabilities;
 546         unsigned long reqprot = prot;
 547         int ret;
 548
 549         /* do the simple checks first */
 550         if (flags & MAP_FIXED || addr) {
 551                 printk(KERN_DEBUG
 552                        "%d: Can't do fixed-address/overlay mmap of RAM\n",
 553                        current->pid);
 554                 return -EINVAL;
 555         }
 556
 557         if ((flags & MAP_TYPE) != MAP_PRIVATE &&
 558             (flags & MAP_TYPE) != MAP_SHARED)
 559                 return -EINVAL;
 560
 561         if (!len)
 562                 return -EINVAL;
 563
 564         /* Careful about overflows.. */
 565         len = PAGE_ALIGN(len);
 566         if (!len || len > TASK_SIZE)
 567                 return -ENOMEM;
 568
 569         /* offset overflow? */
 570         if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
 571                 return -EOVERFLOW;
 572
 573         if (file) {
 574                 /* validate file mapping requests */
 575                 struct address_space *mapping;
 576
 577                 /* files must support mmap */
 578                 if (!file->f_op || !file->f_op->mmap)
 579                         return -ENODEV;
 580
 581                 /* work out if what we've got could possibly be shared
 582                  * - we support chardevs that provide their own "memory"
 583                  * - we support files/blockdevs that are memory backed
 584                  */
 585                 mapping = file->f_mapping;
 586                 if (!mapping)
 587                         mapping = file->f_path.dentry->d_inode->i_mapping;
 588
 589                 capabilities = 0;
 590                 if (mapping && mapping->backing_dev_info)
 591                         capabilities = mapping->backing_dev_info->capabilities;
 592
 593                 if (!capabilities) {
 594                         /* no explicit capabilities set, so assume some
 595                          * defaults */
 596                         switch (file->f_path.dentry->d_inode->i_mode & S_IFMT) {
 597                         case S_IFREG:
 598                         case S_IFBLK:
 599                                 capabilities = BDI_CAP_MAP_COPY;
 600                                 break;
 601
 602                         case S_IFCHR:
 603                                 capabilities =
 604                                         BDI_CAP_MAP_DIRECT |
 605                                         BDI_CAP_READ_MAP |
 606                                         BDI_CAP_WRITE_MAP;
 607                                 break;
 608
 609                         default:
 610                                 return -EINVAL;
 611                         }
 612                 }
 613
 614                 /* eliminate any capabilities that we can't support on this
 615                  * device */
 616                 if (!file->f_op->get_unmapped_area)
 617                         capabilities &= ~BDI_CAP_MAP_DIRECT;
 618                 if (!file->f_op->read)
 619                         capabilities &= ~BDI_CAP_MAP_COPY;
 620
 621                 if (flags & MAP_SHARED) {
 622                         /* do checks for writing, appending and locking */
 623                         if ((prot & PROT_WRITE) &&
 624                             !(file->f_mode & FMODE_WRITE))
 625                                 return -EACCES;
 626
 627                         if (IS_APPEND(file->f_path.dentry->d_inode) &&
 628                             (file->f_mode & FMODE_WRITE))
 629                                 return -EACCES;
 630
 631                         if (locks_verify_locked(file->f_path.dentry->d_inode))
 632                                 return -EAGAIN;
 633
 634                         if (!(capabilities & BDI_CAP_MAP_DIRECT))
 635                                 return -ENODEV;
 636
 637                         if (((prot & PROT_READ)  && !(capabilities & BDI_CAP_READ_MAP))  ||
 638                             ((prot & PROT_WRITE) && !(capabilities & BDI_CAP_WRITE_MAP)) ||
 639                             ((prot & PROT_EXEC)  && !(capabilities & BDI_CAP_EXEC_MAP))
 640                             ) {
 641                                 printk("MAP_SHARED not completely supported on !MMU\n");
 642                                 return -EINVAL;
 643                         }
 644
 645                         /* we mustn't privatise shared mappings */
 646                         capabilities &= ~BDI_CAP_MAP_COPY;
 647                 }
 648                 else {
 649                         /* we're going to read the file into private memory we
 650                          * allocate */
 651                         if (!(capabilities & BDI_CAP_MAP_COPY))
 652                                 return -ENODEV;
 653
 654                         /* we don't permit a private writable mapping to be
 655                          * shared with the backing device */
 656                         if (prot & PROT_WRITE)
 657                                 capabilities &= ~BDI_CAP_MAP_DIRECT;
 658                 }
 659
 660                 /* handle executable mappings and implied executable
 661                  * mappings */
 662                 if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) {
 663                         if (prot & PROT_EXEC)
 664                                 return -EPERM;
 665                 }
 666                 else if ((prot & PROT_READ) && !(prot & PROT_EXEC)) {
 667                         /* handle implication of PROT_EXEC by PROT_READ */
 668                         if (current->personality & READ_IMPLIES_EXEC) {
 669                                 if (capabilities & BDI_CAP_EXEC_MAP)
 670                                         prot |= PROT_EXEC;
 671                         }
 672                 }
 673                 else if ((prot & PROT_READ) &&
 674                          (prot & PROT_EXEC) &&
 675                          !(capabilities & BDI_CAP_EXEC_MAP)
 676                          ) {
 677                         /* backing file is not executable, try to copy */
 678                         capabilities &= ~BDI_CAP_MAP_DIRECT;
 679                 }
 680         }
 681         else {
 682                 /* anonymous mappings are always memory backed and can be
 683                  * privately mapped
 684                  */
 685                 capabilities = BDI_CAP_MAP_COPY;
 686
 687                 /* handle PROT_EXEC implication by PROT_READ */
 688                 if ((prot & PROT_READ) &&
 689                     (current->personality & READ_IMPLIES_EXEC))
 690                         prot |= PROT_EXEC;
 691         }
 692
 693         /* allow the security API to have its say */
 694         ret = security_file_mmap(file, reqprot, prot, flags, addr, 0);
 695         if (ret < 0)
 696                 return ret;
 697
 698         /* looks okay */
 699         *_capabilities = capabilities;
 700         return 0;
 701 }
 702
 703 /*
 704  * we've determined that we can make the mapping, now translate what we
 705  * now know into VMA flags
 706  */
 707 static unsigned long determine_vm_flags(struct file *file,
 708                                         unsigned long prot,
 709                                         unsigned long flags,
 710                                         unsigned long capabilities)
 711 {
 712         unsigned long vm_flags;
 713
 714         vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags);
 715         vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
 716         /* vm_flags |= mm->def_flags; */
 717
 718         if (!(capabilities & BDI_CAP_MAP_DIRECT)) {
 719                 /* attempt to share read-only copies of mapped file chunks */
 720                 if (file && !(prot & PROT_WRITE))
 721                         vm_flags |= VM_MAYSHARE;
 722         }
 723         else {
 724                 /* overlay a shareable mapping on the backing device or inode
 725                  * if possible - used for chardevs, ramfs/tmpfs/shmfs and
 726                  * romfs/cramfs */
 727                 if (flags & MAP_SHARED)
 728                         vm_flags |= VM_MAYSHARE | VM_SHARED;
 729                 else if ((((vm_flags & capabilities) ^ vm_flags) & BDI_CAP_VMFLAGS) == 0)
 730                         vm_flags |= VM_MAYSHARE;
 731         }
 732
 733         /* refuse to let anyone share private mappings with this process if
 734          * it's being traced - otherwise breakpoints set in it may interfere
 735          * with another untraced process
 736          */
 737         if ((flags & MAP_PRIVATE) && (current->ptrace & PT_PTRACED))
 738                 vm_flags &= ~VM_MAYSHARE;
 739
 740         return vm_flags;
 741 }
 742
 743 /*
 744  * set up a shared mapping on a file
 745  */
 746 static int do_mmap_shared_file(struct vm_area_struct *vma, unsigned long len)
 747 {
 748         int ret;
 749
 750         ret = vma->vm_file->f_op->mmap(vma->vm_file, vma);
 751         if (ret != -ENOSYS)
 752                 return ret;
 753
 754         /* getting an ENOSYS error indicates that direct mmap isn't
 755          * possible (as opposed to tried but failed) so we'll fall
 756          * through to making a private copy of the data and mapping
 757          * that if we can */
 758         return -ENODEV;
 759 }
 760
 761 /*
 762  * set up a private mapping or an anonymous shared mapping
 763  */
 764 static int do_mmap_private(struct vm_area_struct *vma, unsigned long len)
 765 {
 766         void *base;
 767         int ret;
 768
 769         /* invoke the file's mapping function so that it can keep track of
 770          * shared mappings on devices or memory
 771          * - VM_MAYSHARE will be set if it may attempt to share
 772          */
 773         if (vma->vm_file) {
 774                 ret = vma->vm_file->f_op->mmap(vma->vm_file, vma);
 775                 if (ret != -ENOSYS) {
 776                         /* shouldn't return success if we're not sharing */
 777                         BUG_ON(ret == 0 && !(vma->vm_flags & VM_MAYSHARE));
 778                         return ret; /* success or a real error */
 779                 }
 780
 781                 /* getting an ENOSYS error indicates that direct mmap isn't
 782                  * possible (as opposed to tried but failed) so we'll try to
 783                  * make a private copy of the data and map that instead */
 784         }
 785
 786         /* allocate some memory to hold the mapping
 787          * - note that this may not return a page-aligned address if the object
 788          *   we're allocating is smaller than a page
 789          */
 790         base = kmalloc(len, GFP_KERNEL|__GFP_COMP);
 791         if (!base)
 792                 goto enomem;
 793
 794         vma->vm_start = (unsigned long) base;
 795         vma->vm_end = vma->vm_start + len;
 796         vma->vm_flags |= VM_MAPPED_COPY;
 797
 798 #ifdef WARN_ON_SLACK
 799         if (len + WARN_ON_SLACK <= kobjsize(result))
 800                 printk("Allocation of %lu bytes from process %d has %lu bytes of slack\n",
 801                        len, current->pid, kobjsize(result) - len);
 802 #endif
 803
 804         if (vma->vm_file) {
 805                 /* read the contents of a file into the copy */
 806                 mm_segment_t old_fs;
 807                 loff_t fpos;
 808
 809                 fpos = vma->vm_pgoff;
 810                 fpos <<= PAGE_SHIFT;
 811
 812                 old_fs = get_fs();
 813                 set_fs(KERNEL_DS);
 814                 ret = vma->vm_file->f_op->read(vma->vm_file, base, len, &fpos);
 815                 set_fs(old_fs);
 816
 817                 if (ret < 0)
 818                         goto error_free;
 819
 820                 /* clear the last little bit */
 821                 if (ret < len)
 822                         memset(base + ret, 0, len - ret);
 823
 824         } else {
 825                 /* if it's an anonymous mapping, then just clear it */
 826                 memset(base, 0, len);
 827         }
 828
 829         return 0;
 830
 831 error_free:
 832         kfree(base);
 833         vma->vm_start = 0;
 834         return ret;
 835
 836 enomem:
 837         printk("Allocation of length %lu from process %d failed\n",
 838                len, current->pid);
 839         show_free_areas();
 840         return -ENOMEM;
 841 }
 842
 843 /*
 844  * handle mapping creation for uClinux
 845  */
 846 unsigned long do_mmap_pgoff(struct file *file,
 847                             unsigned long addr,
 848                             unsigned long len,
 849                             unsigned long prot,
 850                             unsigned long flags,
 851                             unsigned long pgoff)
 852 {
 853         struct vm_list_struct *vml = NULL;
 854         struct vm_area_struct *vma = NULL;
 855         struct rb_node *rb;
 856         unsigned long capabilities, vm_flags;
 857         void *result;
 858         int ret;
 859
 860         if (!(flags & MAP_FIXED))
 861                 addr = round_hint_to_min(addr);
 862
 863         /* decide whether we should attempt the mapping, and if so what sort of
 864          * mapping */
 865         ret = validate_mmap_request(file, addr, len, prot, flags, pgoff,
 866                                     &capabilities);
 867         if (ret < 0)
 868                 return ret;
 869
 870         /* we've determined that we can make the mapping, now translate what we
 871          * now know into VMA flags */
 872         vm_flags = determine_vm_flags(file, prot, flags, capabilities);
 873
 874         /* we're going to need to record the mapping if it works */
 875         vml = kzalloc(sizeof(struct vm_list_struct), GFP_KERNEL);
 876         if (!vml)
 877                 goto error_getting_vml;
 878
 879         down_write(&nommu_vma_sem);
 880
 881         /* if we want to share, we need to check for VMAs created by other
 882          * mmap() calls that overlap with our proposed mapping
 883          * - we can only share with an exact match on most regular files
 884          * - shared mappings on character devices and memory backed files are
 885          *   permitted to overlap inexactly as far as we are concerned for in
 886          *   these cases, sharing is handled in the driver or filesystem rather
 887          *   than here
 888          */
 889         if (vm_flags & VM_MAYSHARE) {
 890                 unsigned long pglen = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
 891                 unsigned long vmpglen;
 892
 893                 /* suppress VMA sharing for shared regions */
 894                 if (vm_flags & VM_SHARED &&
 895                     capabilities & BDI_CAP_MAP_DIRECT)
 896                         goto dont_share_VMAs;
 897
 898                 for (rb = rb_first(&nommu_vma_tree); rb; rb = rb_next(rb)) {
 899                         vma = rb_entry(rb, struct vm_area_struct, vm_rb);
 900
 901                         if (!(vma->vm_flags & VM_MAYSHARE))
 902                                 continue;
 903
 904                         /* search for overlapping mappings on the same file */
 905                         if (vma->vm_file->f_path.dentry->d_inode != file->f_path.dentry->d_inode)
 906                                 continue;
 907
 908                         if (vma->vm_pgoff >= pgoff + pglen)
 909                                 continue;
 910
 911                         vmpglen = vma->vm_end - vma->vm_start + PAGE_SIZE - 1;
 912                         vmpglen >>= PAGE_SHIFT;
 913                         if (pgoff >= vma->vm_pgoff + vmpglen)
 914                                 continue;
 915
 916                         /* handle inexactly overlapping matches between mappings */
 917                         if (vma->vm_pgoff != pgoff || vmpglen != pglen) {
 918                                 if (!(capabilities & BDI_CAP_MAP_DIRECT))
 919                                         goto sharing_violation;
 920                                 continue;
 921                         }
 922
 923                         /* we've found a VMA we can share */
 924                         atomic_inc(&vma->vm_usage);
 925
 926                         vml->vma = vma;
 927                         result = (void *) vma->vm_start;
 928                         goto shared;
 929                 }
 930
 931         dont_share_VMAs:
 932                 vma = NULL;
 933
 934                 /* obtain the address at which to make a shared mapping
 935                  * - this is the hook for quasi-memory character devices to
 936                  *   tell us the location of a shared mapping
 937                  */
 938                 if (file && file->f_op->get_unmapped_area) {
 939                         addr = file->f_op->get_unmapped_area(file, addr, len,
 940                                                              pgoff, flags);
 941                         if (IS_ERR((void *) addr)) {
 942                                 ret = addr;
 943                                 if (ret != (unsigned long) -ENOSYS)
 944                                         goto error;
 945
 946                                 /* the driver refused to tell us where to site
 947                                  * the mapping so we'll have to attempt to copy
 948                                  * it */
 949                                 ret = (unsigned long) -ENODEV;
 950                                 if (!(capabilities & BDI_CAP_MAP_COPY))
 951                                         goto error;
 952
 953                                 capabilities &= ~BDI_CAP_MAP_DIRECT;
 954                         }
 955                 }
 956         }
 957
 958         /* we're going to need a VMA struct as well */
 959         vma = kzalloc(sizeof(struct vm_area_struct), GFP_KERNEL);
 960         if (!vma)
 961                 goto error_getting_vma;
 962
 963         INIT_LIST_HEAD(&vma->anon_vma_node);
 964         atomic_set(&vma->vm_usage, 1);
 965         if (file)
 966                 get_file(file);
 967         vma->vm_file    = file;
 968         vma->vm_flags   = vm_flags;
 969         vma->vm_start   = addr;
 970         vma->vm_end     = addr + len;
 971         vma->vm_pgoff   = pgoff;
 972
 973         vml->vma = vma;
 974
 975         /* set up the mapping */
 976         if (file && vma->vm_flags & VM_SHARED)
 977                 ret = do_mmap_shared_file(vma, len);
 978         else
 979                 ret = do_mmap_private(vma, len);
 980         if (ret < 0)
 981                 goto error;
 982
 983         /* okay... we have a mapping; now we have to register it */
 984         result = (void *) vma->vm_start;
 985
 986         if (vma->vm_flags & VM_MAPPED_COPY) {
 987                 realalloc += kobjsize(result);
 988                 askedalloc += len;
 989         }
 990
 991         realalloc += kobjsize(vma);
 992         askedalloc += sizeof(*vma);
 993
 994         current->mm->total_vm += len >> PAGE_SHIFT;
 995
 996         add_nommu_vma(vma);
 997
 998  shared:
 999         realalloc += kobjsize(vml);
1000         askedalloc += sizeof(*vml);
1001
1002         add_vma_to_mm(current->mm, vml);
1003
1004         up_write(&nommu_vma_sem);
1005
1006         if (prot & PROT_EXEC)
1007                 flush_icache_range((unsigned long) result,
1008                                    (unsigned long) result + len);
1009
1010 #ifdef DEBUG
1011         printk("do_mmap:\n");
1012         show_process_blocks();
1013 #endif
1014
1015         return (unsigned long) result;
1016
1017  error:
1018         up_write(&nommu_vma_sem);
1019         kfree(vml);
1020         if (vma) {
1021                 if (vma->vm_file)
1022                         fput(vma->vm_file);
1023                 kfree(vma);
1024         }
1025         return ret;
1026
1027  sharing_violation:
1028         up_write(&nommu_vma_sem);
1029         printk("Attempt to share mismatched mappings\n");
1030         kfree(vml);
1031         return -EINVAL;
1032
1033  error_getting_vma:
1034         up_write(&nommu_vma_sem);
1035         kfree(vml);
1036         printk("Allocation of vma for %lu byte allocation from process %d failed\n",
1037                len, current->pid);
1038         show_free_areas();
1039         return -ENOMEM;
1040
1041  error_getting_vml:
1042         printk("Allocation of vml for %lu byte allocation from process %d failed\n",
1043                len, current->pid);
1044         show_free_areas();
1045         return -ENOMEM;
1046 }
1047 EXPORT_SYMBOL(do_mmap_pgoff);
1048
1049 /*
1050  * handle mapping disposal for uClinux
1051  */
1052 static void put_vma(struct vm_area_struct *vma)
1053 {
1054         if (vma) {
1055                 down_write(&nommu_vma_sem);
1056
1057                 if (atomic_dec_and_test(&vma->vm_usage)) {
1058                         delete_nommu_vma(vma);
1059
1060                         if (vma->vm_ops && vma->vm_ops->close)
1061                                 vma->vm_ops->close(vma);
1062
1063                         /* IO memory and memory shared directly out of the pagecache from
1064                          * ramfs/tmpfs mustn't be released here */
1065                         if (vma->vm_flags & VM_MAPPED_COPY) {
1066                                 realalloc -= kobjsize((void *) vma->vm_start);
1067                                 askedalloc -= vma->vm_end - vma->vm_start;
1068                                 kfree((void *) vma->vm_start);
1069                         }
1070
1071                         realalloc -= kobjsize(vma);
1072                         askedalloc -= sizeof(*vma);
1073
1074                         if (vma->vm_file)
1075                                 fput(vma->vm_file);
1076                         kfree(vma);
1077                 }
1078
1079                 up_write(&nommu_vma_sem);
1080         }
1081 }
1082
1083 /*
1084  * release a mapping
1085  * - under NOMMU conditions the parameters must match exactly to the mapping to
1086  *   be removed
1087  */
1088 int do_munmap(struct mm_struct *mm, unsigned long addr, size_t len)
1089 {
1090         struct vm_list_struct *vml, **parent;
1091         unsigned long end = addr + len;
1092
1093 #ifdef DEBUG
1094         printk("do_munmap:\n");
1095 #endif
1096
1097         for (parent = &mm->context.vmlist; *parent; parent = &(*parent)->next) {
1098                 if ((*parent)->vma->vm_start > addr)
1099                         break;
1100                 if ((*parent)->vma->vm_start == addr &&
1101                     ((len == 0) || ((*parent)->vma->vm_end == end)))
1102                         goto found;
1103         }
1104
1105         printk("munmap of non-mmaped memory by process %d (%s): %p\n",
1106                current->pid, current->comm, (void *) addr);
1107         return -EINVAL;
1108
1109  found:
1110         vml = *parent;
1111
1112         put_vma(vml->vma);
1113
1114         *parent = vml->next;
1115         realalloc -= kobjsize(vml);
1116         askedalloc -= sizeof(*vml);
1117         kfree(vml);
1118
1119         update_hiwater_vm(mm);
1120         mm->total_vm -= len >> PAGE_SHIFT;
1121
1122 #ifdef DEBUG
1123         show_process_blocks();
1124 #endif
1125
1126         return 0;
1127 }
1128 EXPORT_SYMBOL(do_munmap);
1129
1130 asmlinkage long sys_munmap(unsigned long addr, size_t len)
1131 {
1132         int ret;
1133         struct mm_struct *mm = current->mm;
1134
1135         down_write(&mm->mmap_sem);
1136         ret = do_munmap(mm, addr, len);
1137         up_write(&mm->mmap_sem);
1138         return ret;
1139 }
1140
1141 /*
1142  * Release all mappings
1143  */
1144 void exit_mmap(struct mm_struct * mm)
1145 {
1146         struct vm_list_struct *tmp;
1147
1148         if (mm) {
1149 #ifdef DEBUG
1150                 printk("Exit_mmap:\n");
1151 #endif
1152
1153                 mm->total_vm = 0;
1154
1155                 while ((tmp = mm->context.vmlist)) {
1156                         mm->context.vmlist = tmp->next;
1157                         put_vma(tmp->vma);
1158
1159                         realalloc -= kobjsize(tmp);
1160                         askedalloc -= sizeof(*tmp);
1161                         kfree(tmp);
1162                 }
1163
1164 #ifdef DEBUG
1165                 show_process_blocks();
1166 #endif
1167         }
1168 }
1169
1170 unsigned long do_brk(unsigned long addr, unsigned long len)
1171 {
1172         return -ENOMEM;
1173 }
1174
1175 /*
1176  * expand (or shrink) an existing mapping, potentially moving it at the same
1177  * time (controlled by the MREMAP_MAYMOVE flag and available VM space)
1178  *
1179  * under NOMMU conditions, we only permit changing a mapping's size, and only
1180  * as long as it stays within the hole allocated by the kmalloc() call in
1181  * do_mmap_pgoff() and the block is not shareable
1182  *
1183  * MREMAP_FIXED is not supported under NOMMU conditions
1184  */
1185 unsigned long do_mremap(unsigned long addr,
1186                         unsigned long old_len, unsigned long new_len,
1187                         unsigned long flags, unsigned long new_addr)
1188 {
1189         struct vm_area_struct *vma;
1190
1191         /* insanity checks first */
1192         if (new_len == 0)
1193                 return (unsigned long) -EINVAL;
1194
1195         if (flags & MREMAP_FIXED && new_addr != addr)
1196                 return (unsigned long) -EINVAL;
1197
1198         vma = find_vma_exact(current->mm, addr);
1199         if (!vma)
1200                 return (unsigned long) -EINVAL;
1201
1202         if (vma->vm_end != vma->vm_start + old_len)
1203                 return (unsigned long) -EFAULT;
1204
1205         if (vma->vm_flags & VM_MAYSHARE)
1206                 return (unsigned long) -EPERM;
1207
1208         if (new_len > kobjsize((void *) addr))
1209                 return (unsigned long) -ENOMEM;
1210
1211         /* all checks complete - do it */
1212         vma->vm_end = vma->vm_start + new_len;
1213
1214         askedalloc -= old_len;
1215         askedalloc += new_len;
1216
1217         return vma->vm_start;
1218 }
1219 EXPORT_SYMBOL(do_mremap);
1220
1221 asmlinkage unsigned long sys_mremap(unsigned long addr,
1222         unsigned long old_len, unsigned long new_len,
1223         unsigned long flags, unsigned long new_addr)
1224 {
1225         unsigned long ret;
1226
1227         down_write(&current->mm->mmap_sem);
1228         ret = do_mremap(addr, old_len, new_len, flags, new_addr);
1229         up_write(&current->mm->mmap_sem);
1230         return ret;
1231 }
1232
1233 struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
1234                         unsigned int foll_flags)
1235 {
1236         return NULL;
1237 }
1238
1239 int remap_pfn_range(struct vm_area_struct *vma, unsigned long from,
1240                 unsigned long to, unsigned long size, pgprot_t prot)
1241 {
1242         vma->vm_start = vma->vm_pgoff << PAGE_SHIFT;
1243         return 0;
1244 }
1245 EXPORT_SYMBOL(remap_pfn_range);
1246
1247 int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
1248                         unsigned long pgoff)
1249 {
1250         unsigned int size = vma->vm_end - vma->vm_start;
1251
1252         if (!(vma->vm_flags & VM_USERMAP))
1253                 return -EINVAL;
1254
1255         vma->vm_start = (unsigned long)(addr + (pgoff << PAGE_SHIFT));
1256         vma->vm_end = vma->vm_start + size;
1257
1258         return 0;
1259 }
1260 EXPORT_SYMBOL(remap_vmalloc_range);
1261
1262 void swap_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
1263 {
1264 }
1265
1266 unsigned long arch_get_unmapped_area(struct file *file, unsigned long addr,
1267         unsigned long len, unsigned long pgoff, unsigned long flags)
1268 {
1269         return -ENOMEM;
1270 }
1271
1272 void arch_unmap_area(struct mm_struct *mm, unsigned long addr)
1273 {
1274 }
1275
1276 void unmap_mapping_range(struct address_space *mapping,
1277                          loff_t const holebegin, loff_t const holelen,
1278                          int even_cows)
1279 {
1280 }
1281 EXPORT_SYMBOL(unmap_mapping_range);
1282
1283 /*
1284  * ask for an unmapped area at which to create a mapping on a file
1285  */
1286 unsigned long get_unmapped_area(struct file *file, unsigned long addr,
1287                                 unsigned long len, unsigned long pgoff,
1288                                 unsigned long flags)
1289 {
1290         unsigned long (*get_area)(struct file *, unsigned long, unsigned long,
1291                                   unsigned long, unsigned long);
1292
1293         get_area = current->mm->get_unmapped_area;
1294         if (file && file->f_op && file->f_op->get_unmapped_area)
1295                 get_area = file->f_op->get_unmapped_area;
1296
1297         if (!get_area)
1298                 return -ENOSYS;
1299
1300         return get_area(file, addr, len, pgoff, flags);
1301 }
1302 EXPORT_SYMBOL(get_unmapped_area);
1303
1304 /*
1305  * Check that a process has enough memory to allocate a new virtual
1306  * mapping. 0 means there is enough memory for the allocation to
1307  * succeed and -ENOMEM implies there is not.
1308  *
1309  * We currently support three overcommit policies, which are set via the
1310  * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-accounting
1311  *
1312  * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
1313  * Additional code 2002 Jul 20 by Robert Love.
1314  *
1315  * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
1316  *
1317  * Note this is a helper function intended to be used by LSMs which
1318  * wish to use this logic.
1319  */
1320 int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
1321 {
1322         unsigned long free, allowed;
1323
1324         vm_acct_memory(pages);
1325
1326         /*
1327          * Sometimes we want to use more memory than we have
1328          */
1329         if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
1330                 return 0;
1331
1332         if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
1333                 unsigned long n;
1334
1335                 free = global_page_state(NR_FILE_PAGES);
1336                 free += nr_swap_pages;
1337
1338                 /*
1339                  * Any slabs which are created with the
1340                  * SLAB_RECLAIM_ACCOUNT flag claim to have contents
1341                  * which are reclaimable, under pressure.  The dentry
1342                  * cache and most inode caches should fall into this
1343                  */
1344                 free += global_page_state(NR_SLAB_RECLAIMABLE);
1345
1346                 /*
1347                  * Leave the last 3% for root
1348                  */
1349                 if (!cap_sys_admin)
1350                         free -= free / 32;
1351
1352                 if (free > pages)
1353                         return 0;
1354
1355                 /*
1356                  * nr_free_pages() is very expensive on large systems,
1357                  * only call if we're about to fail.
1358                  */
1359                 n = nr_free_pages();
1360
1361                 /*
1362                  * Leave reserved pages. The pages are not for anonymous pages.
1363                  */
1364                 if (n <= totalreserve_pages)
1365                         goto error;
1366                 else
1367                         n -= totalreserve_pages;
1368
1369                 /*
1370                  * Leave the last 3% for root
1371                  */
1372                 if (!cap_sys_admin)
1373                         n -= n / 32;
1374                 free += n;
1375
1376                 if (free > pages)
1377                         return 0;
1378
1379                 goto error;
1380         }
1381
1382         allowed = totalram_pages * sysctl_overcommit_ratio / 100;
1383         /*
1384          * Leave the last 3% for root
1385          */
1386         if (!cap_sys_admin)
1387                 allowed -= allowed / 32;
1388         allowed += total_swap_pages;
1389
1390         /* Don't let a single process grow too big:
1391            leave 3% of the size of this process for other processes */
1392         allowed -= current->mm->total_vm / 32;
1393
1394         /*
1395          * cast `allowed' as a signed long because vm_committed_space
1396          * sometimes has a negative value
1397          */
1398         if (atomic_read(&vm_committed_space) < (long)allowed)
1399                 return 0;
1400 error:
1401         vm_unacct_memory(pages);
1402
1403         return -ENOMEM;
1404 }
1405
1406 int in_gate_area_no_task(unsigned long addr)
1407 {
1408         return 0;
1409 }
1410
1411 int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1412 {
1413         BUG();
1414         return 0;
1415 }
1416 EXPORT_SYMBOL(filemap_fault);
1417
1418 /*
1419  * Access another process' address space.
1420  * - source/target buffer must be kernel space
1421  */
1422 int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
1423 {
1424         struct vm_area_struct *vma;
1425         struct mm_struct *mm;
1426
1427         if (addr + len < addr)
1428                 return 0;
1429
1430         mm = get_task_mm(tsk);
1431         if (!mm)
1432                 return 0;
1433
1434         down_read(&mm->mmap_sem);
1435
1436         /* the access must start within one of the target process's mappings */
1437         vma = find_vma(mm, addr);
1438         if (vma) {
1439                 /* don't overrun this mapping */
1440                 if (addr + len >= vma->vm_end)
1441                         len = vma->vm_end - addr;
1442
1443                 /* only read or write mappings where it is permitted */
1444                 if (write && vma->vm_flags & VM_MAYWRITE)
1445                         len -= copy_to_user((void *) addr, buf, len);
1446                 else if (!write && vma->vm_flags & VM_MAYREAD)
1447                         len -= copy_from_user(buf, (void *) addr, len);
1448                 else
1449                         len = 0;
1450         } else {
1451                 len = 0;
1452         }
1453
1454         up_read(&mm->mmap_sem);
1455         mmput(mm);
1456         return len;
1457 }