mm/nommu.c

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