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