mm/nommu.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  linux/mm/nommu.c
   4  *
   5  *  Replacement code for mm functions to support CPU's that don't
   6  *  have any form of memory management unit (thus no virtual memory).
   7  *
   8  *  See Documentation/admin-guide/mm/nommu-mmap.rst
   9  *
  10  *  Copyright (c) 2004-2008 David Howells <dhowells@redhat.com>
  11  *  Copyright (c) 2000-2003 David McCullough <davidm@snapgear.com>
  12  *  Copyright (c) 2000-2001 D Jeff Dionne <jeff@uClinux.org>
  13  *  Copyright (c) 2002      Greg Ungerer <gerg@snapgear.com>
  14  *  Copyright (c) 2007-2010 Paul Mundt <lethal@linux-sh.org>
  15  */
  16
  17 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  18
  19 #include <linux/export.h>
  20 #include <linux/mm.h>
  21 #include <linux/sched/mm.h>
  22 #include <linux/vmacache.h>
  23 #include <linux/mman.h>
  24 #include <linux/swap.h>
  25 #include <linux/file.h>
  26 #include <linux/highmem.h>
  27 #include <linux/pagemap.h>
  28 #include <linux/slab.h>
  29 #include <linux/vmalloc.h>
  30 #include <linux/backing-dev.h>
  31 #include <linux/compiler.h>
  32 #include <linux/mount.h>
  33 #include <linux/personality.h>
  34 #include <linux/security.h>
  35 #include <linux/syscalls.h>
  36 #include <linux/audit.h>
  37 #include <linux/printk.h>
  38
  39 #include <linux/uaccess.h>
  40 #include <asm/tlb.h>
  41 #include <asm/tlbflush.h>
  42 #include <asm/mmu_context.h>
  43 #include "internal.h"
  44
  45 void *high_memory;
  46 EXPORT_SYMBOL(high_memory);
  47 struct page *mem_map;
  48 unsigned long max_mapnr;
  49 EXPORT_SYMBOL(max_mapnr);
  50 unsigned long highest_memmap_pfn;
  51 int sysctl_nr_trim_pages = CONFIG_NOMMU_INITIAL_TRIM_EXCESS;
  52 int heap_stack_gap = 0;
  53
  54 atomic_long_t mmap_pages_allocated;
  55
  56 EXPORT_SYMBOL(mem_map);
  57
  58 /* list of mapped, potentially shareable regions */
  59 static struct kmem_cache *vm_region_jar;
  60 struct rb_root nommu_region_tree = RB_ROOT;
  61 DECLARE_RWSEM(nommu_region_sem);
  62
  63 const struct vm_operations_struct generic_file_vm_ops = {
  64 };
  65
  66 /*
  67  * Return the total memory allocated for this pointer, not
  68  * just what the caller asked for.
  69  *
  70  * Doesn't have to be accurate, i.e. may have races.
  71  */
  72 unsigned int kobjsize(const void *objp)
  73 {
  74         struct page *page;
  75
  76         /*
  77          * If the object we have should not have ksize performed on it,
  78          * return size of 0
  79          */
  80         if (!objp || !virt_addr_valid(objp))
  81                 return 0;
  82
  83         page = virt_to_head_page(objp);
  84
  85         /*
  86          * If the allocator sets PageSlab, we know the pointer came from
  87          * kmalloc().
  88          */
  89         if (PageSlab(page))
  90                 return ksize(objp);
  91
  92         /*
  93          * If it's not a compound page, see if we have a matching VMA
  94          * region. This test is intentionally done in reverse order,
  95          * so if there's no VMA, we still fall through and hand back
  96          * PAGE_SIZE for 0-order pages.
  97          */
  98         if (!PageCompound(page)) {
  99                 struct vm_area_struct *vma;
 100
 101                 vma = find_vma(current->mm, (unsigned long)objp);
 102                 if (vma)
 103                         return vma->vm_end - vma->vm_start;
 104         }
 105
 106         /*
 107          * The ksize() function is only guaranteed to work for pointers
 108          * returned by kmalloc(). So handle arbitrary pointers here.
 109          */
 110         return page_size(page);
 111 }
 112
 113 /**
 114  * follow_pfn - look up PFN at a user virtual address
 115  * @vma: memory mapping
 116  * @address: user virtual address
 117  * @pfn: location to store found PFN
 118  *
 119  * Only IO mappings and raw PFN mappings are allowed.
 120  *
 121  * Returns zero and the pfn at @pfn on success, -ve otherwise.
 122  */
 123 int follow_pfn(struct vm_area_struct *vma, unsigned long address,
 124         unsigned long *pfn)
 125 {
 126         if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
 127                 return -EINVAL;
 128
 129         *pfn = address >> PAGE_SHIFT;
 130         return 0;
 131 }
 132 EXPORT_SYMBOL(follow_pfn);
 133
 134 LIST_HEAD(vmap_area_list);
 135
 136 void vfree(const void *addr)
 137 {
 138         kfree(addr);
 139 }
 140 EXPORT_SYMBOL(vfree);
 141
 142 void *__vmalloc(unsigned long size, gfp_t gfp_mask)
 143 {
 144         /*
 145          *  You can't specify __GFP_HIGHMEM with kmalloc() since kmalloc()
 146          * returns only a logical address.
 147          */
 148         return kmalloc(size, (gfp_mask | __GFP_COMP) & ~__GFP_HIGHMEM);
 149 }
 150 EXPORT_SYMBOL(__vmalloc);
 151
 152 void *__vmalloc_node_range(unsigned long size, unsigned long align,
 153                 unsigned long start, unsigned long end, gfp_t gfp_mask,
 154                 pgprot_t prot, unsigned long vm_flags, int node,
 155                 const void *caller)
 156 {
 157         return __vmalloc(size, gfp_mask);
 158 }
 159
 160 void *__vmalloc_node(unsigned long size, unsigned long align, gfp_t gfp_mask,
 161                 int node, const void *caller)
 162 {
 163         return __vmalloc(size, gfp_mask);
 164 }
 165
 166 static void *__vmalloc_user_flags(unsigned long size, gfp_t flags)
 167 {
 168         void *ret;
 169
 170         ret = __vmalloc(size, flags);
 171         if (ret) {
 172                 struct vm_area_struct *vma;
 173
 174                 mmap_write_lock(current->mm);
 175                 vma = find_vma(current->mm, (unsigned long)ret);
 176                 if (vma)
 177                         vma->vm_flags |= VM_USERMAP;
 178                 mmap_write_unlock(current->mm);
 179         }
 180
 181         return ret;
 182 }
 183
 184 void *vmalloc_user(unsigned long size)
 185 {
 186         return __vmalloc_user_flags(size, GFP_KERNEL | __GFP_ZERO);
 187 }
 188 EXPORT_SYMBOL(vmalloc_user);
 189
 190 struct page *vmalloc_to_page(const void *addr)
 191 {
 192         return virt_to_page(addr);
 193 }
 194 EXPORT_SYMBOL(vmalloc_to_page);
 195
 196 unsigned long vmalloc_to_pfn(const void *addr)
 197 {
 198         return page_to_pfn(virt_to_page(addr));
 199 }
 200 EXPORT_SYMBOL(vmalloc_to_pfn);
 201
 202 long vread(char *buf, char *addr, unsigned long count)
 203 {
 204         /* Don't allow overflow */
 205         if ((unsigned long) buf + count < count)
 206                 count = -(unsigned long) buf;
 207
 208         memcpy(buf, addr, count);
 209         return count;
 210 }
 211
 212 /*
 213  *      vmalloc  -  allocate virtually contiguous memory
 214  *
 215  *      @size:          allocation size
 216  *
 217  *      Allocate enough pages to cover @size from the page level
 218  *      allocator and map them into contiguous 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);
 226 }
 227 EXPORT_SYMBOL(vmalloc);
 228
 229 void *vmalloc_huge(unsigned long size, gfp_t gfp_mask) __weak __alias(__vmalloc);
 230
 231 /*
 232  *      vzalloc - allocate virtually contiguous memory with zero fill
 233  *
 234  *      @size:          allocation size
 235  *
 236  *      Allocate enough pages to cover @size from the page level
 237  *      allocator and map them into contiguous kernel virtual space.
 238  *      The memory allocated is set to zero.
 239  *
 240  *      For tight control over page level allocator and protection flags
 241  *      use __vmalloc() instead.
 242  */
 243 void *vzalloc(unsigned long size)
 244 {
 245         return __vmalloc(size, GFP_KERNEL | __GFP_ZERO);
 246 }
 247 EXPORT_SYMBOL(vzalloc);
 248
 249 /**
 250  * vmalloc_node - allocate memory on a specific node
 251  * @size:       allocation size
 252  * @node:       numa node
 253  *
 254  * Allocate enough pages to cover @size from the page level
 255  * allocator and map them into contiguous kernel virtual space.
 256  *
 257  * For tight control over page level allocator and protection flags
 258  * use __vmalloc() instead.
 259  */
 260 void *vmalloc_node(unsigned long size, int node)
 261 {
 262         return vmalloc(size);
 263 }
 264 EXPORT_SYMBOL(vmalloc_node);
 265
 266 /**
 267  * vzalloc_node - allocate memory on a specific node with zero fill
 268  * @size:       allocation size
 269  * @node:       numa node
 270  *
 271  * Allocate enough pages to cover @size from the page level
 272  * allocator and map them into contiguous kernel virtual space.
 273  * The memory allocated is set to zero.
 274  *
 275  * For tight control over page level allocator and protection flags
 276  * use __vmalloc() instead.
 277  */
 278 void *vzalloc_node(unsigned long size, int node)
 279 {
 280         return vzalloc(size);
 281 }
 282 EXPORT_SYMBOL(vzalloc_node);
 283
 284 /**
 285  * vmalloc_32  -  allocate virtually contiguous memory (32bit addressable)
 286  *      @size:          allocation size
 287  *
 288  *      Allocate enough 32bit PA addressable pages to cover @size from the
 289  *      page level allocator and map them into contiguous kernel virtual space.
 290  */
 291 void *vmalloc_32(unsigned long size)
 292 {
 293         return __vmalloc(size, GFP_KERNEL);
 294 }
 295 EXPORT_SYMBOL(vmalloc_32);
 296
 297 /**
 298  * vmalloc_32_user - allocate zeroed virtually contiguous 32bit memory
 299  *      @size:          allocation size
 300  *
 301  * The resulting memory area is 32bit addressable and zeroed so it can be
 302  * mapped to userspace without leaking data.
 303  *
 304  * VM_USERMAP is set on the corresponding VMA so that subsequent calls to
 305  * remap_vmalloc_range() are permissible.
 306  */
 307 void *vmalloc_32_user(unsigned long size)
 308 {
 309         /*
 310          * We'll have to sort out the ZONE_DMA bits for 64-bit,
 311          * but for now this can simply use vmalloc_user() directly.
 312          */
 313         return vmalloc_user(size);
 314 }
 315 EXPORT_SYMBOL(vmalloc_32_user);
 316
 317 void *vmap(struct page **pages, unsigned int count, unsigned long flags, pgprot_t prot)
 318 {
 319         BUG();
 320         return NULL;
 321 }
 322 EXPORT_SYMBOL(vmap);
 323
 324 void vunmap(const void *addr)
 325 {
 326         BUG();
 327 }
 328 EXPORT_SYMBOL(vunmap);
 329
 330 void *vm_map_ram(struct page **pages, unsigned int count, int node)
 331 {
 332         BUG();
 333         return NULL;
 334 }
 335 EXPORT_SYMBOL(vm_map_ram);
 336
 337 void vm_unmap_ram(const void *mem, unsigned int count)
 338 {
 339         BUG();
 340 }
 341 EXPORT_SYMBOL(vm_unmap_ram);
 342
 343 void vm_unmap_aliases(void)
 344 {
 345 }
 346 EXPORT_SYMBOL_GPL(vm_unmap_aliases);
 347
 348 void free_vm_area(struct vm_struct *area)
 349 {
 350         BUG();
 351 }
 352 EXPORT_SYMBOL_GPL(free_vm_area);
 353
 354 int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
 355                    struct page *page)
 356 {
 357         return -EINVAL;
 358 }
 359 EXPORT_SYMBOL(vm_insert_page);
 360
 361 int vm_map_pages(struct vm_area_struct *vma, struct page **pages,
 362                         unsigned long num)
 363 {
 364         return -EINVAL;
 365 }
 366 EXPORT_SYMBOL(vm_map_pages);
 367
 368 int vm_map_pages_zero(struct vm_area_struct *vma, struct page **pages,
 369                                 unsigned long num)
 370 {
 371         return -EINVAL;
 372 }
 373 EXPORT_SYMBOL(vm_map_pages_zero);
 374
 375 /*
 376  *  sys_brk() for the most part doesn't need the global kernel
 377  *  lock, except when an application is doing something nasty
 378  *  like trying to un-brk an area that has already been mapped
 379  *  to a regular file.  in this case, the unmapping will need
 380  *  to invoke file system routines that need the global lock.
 381  */
 382 SYSCALL_DEFINE1(brk, unsigned long, brk)
 383 {
 384         struct mm_struct *mm = current->mm;
 385
 386         if (brk < mm->start_brk || brk > mm->context.end_brk)
 387                 return mm->brk;
 388
 389         if (mm->brk == brk)
 390                 return mm->brk;
 391
 392         /*
 393          * Always allow shrinking brk
 394          */
 395         if (brk <= mm->brk) {
 396                 mm->brk = brk;
 397                 return brk;
 398         }
 399
 400         /*
 401          * Ok, looks good - let it rip.
 402          */
 403         flush_icache_user_range(mm->brk, brk);
 404         return mm->brk = brk;
 405 }
 406
 407 /*
 408  * initialise the percpu counter for VM and region record slabs
 409  */
 410 void __init mmap_init(void)
 411 {
 412         int ret;
 413
 414         ret = percpu_counter_init(&vm_committed_as, 0, GFP_KERNEL);
 415         VM_BUG_ON(ret);
 416         vm_region_jar = KMEM_CACHE(vm_region, SLAB_PANIC|SLAB_ACCOUNT);
 417 }
 418
 419 /*
 420  * validate the region tree
 421  * - the caller must hold the region lock
 422  */
 423 #ifdef CONFIG_DEBUG_NOMMU_REGIONS
 424 static noinline void validate_nommu_regions(void)
 425 {
 426         struct vm_region *region, *last;
 427         struct rb_node *p, *lastp;
 428
 429         lastp = rb_first(&nommu_region_tree);
 430         if (!lastp)
 431                 return;
 432
 433         last = rb_entry(lastp, struct vm_region, vm_rb);
 434         BUG_ON(last->vm_end <= last->vm_start);
 435         BUG_ON(last->vm_top < last->vm_end);
 436
 437         while ((p = rb_next(lastp))) {
 438                 region = rb_entry(p, struct vm_region, vm_rb);
 439                 last = rb_entry(lastp, struct vm_region, vm_rb);
 440
 441                 BUG_ON(region->vm_end <= region->vm_start);
 442                 BUG_ON(region->vm_top < region->vm_end);
 443                 BUG_ON(region->vm_start < last->vm_top);
 444
 445                 lastp = p;
 446         }
 447 }
 448 #else
 449 static void validate_nommu_regions(void)
 450 {
 451 }
 452 #endif
 453
 454 /*
 455  * add a region into the global tree
 456  */
 457 static void add_nommu_region(struct vm_region *region)
 458 {
 459         struct vm_region *pregion;
 460         struct rb_node **p, *parent;
 461
 462         validate_nommu_regions();
 463
 464         parent = NULL;
 465         p = &nommu_region_tree.rb_node;
 466         while (*p) {
 467                 parent = *p;
 468                 pregion = rb_entry(parent, struct vm_region, vm_rb);
 469                 if (region->vm_start < pregion->vm_start)
 470                         p = &(*p)->rb_left;
 471                 else if (region->vm_start > pregion->vm_start)
 472                         p = &(*p)->rb_right;
 473                 else if (pregion == region)
 474                         return;
 475                 else
 476                         BUG();
 477         }
 478
 479         rb_link_node(&region->vm_rb, parent, p);
 480         rb_insert_color(&region->vm_rb, &nommu_region_tree);
 481
 482         validate_nommu_regions();
 483 }
 484
 485 /*
 486  * delete a region from the global tree
 487  */
 488 static void delete_nommu_region(struct vm_region *region)
 489 {
 490         BUG_ON(!nommu_region_tree.rb_node);
 491
 492         validate_nommu_regions();
 493         rb_erase(&region->vm_rb, &nommu_region_tree);
 494         validate_nommu_regions();
 495 }
 496
 497 /*
 498  * free a contiguous series of pages
 499  */
 500 static void free_page_series(unsigned long from, unsigned long to)
 501 {
 502         for (; from < to; from += PAGE_SIZE) {
 503                 struct page *page = virt_to_page(from);
 504
 505                 atomic_long_dec(&mmap_pages_allocated);
 506                 put_page(page);
 507         }
 508 }
 509
 510 /*
 511  * release a reference to a region
 512  * - the caller must hold the region semaphore for writing, which this releases
 513  * - the region may not have been added to the tree yet, in which case vm_top
 514  *   will equal vm_start
 515  */
 516 static void __put_nommu_region(struct vm_region *region)
 517         __releases(nommu_region_sem)
 518 {
 519         BUG_ON(!nommu_region_tree.rb_node);
 520
 521         if (--region->vm_usage == 0) {
 522                 if (region->vm_top > region->vm_start)
 523                         delete_nommu_region(region);
 524                 up_write(&nommu_region_sem);
 525
 526                 if (region->vm_file)
 527                         fput(region->vm_file);
 528
 529                 /* IO memory and memory shared directly out of the pagecache
 530                  * from ramfs/tmpfs mustn't be released here */
 531                 if (region->vm_flags & VM_MAPPED_COPY)
 532                         free_page_series(region->vm_start, region->vm_top);
 533                 kmem_cache_free(vm_region_jar, region);
 534         } else {
 535                 up_write(&nommu_region_sem);
 536         }
 537 }
 538
 539 /*
 540  * release a reference to a region
 541  */
 542 static void put_nommu_region(struct vm_region *region)
 543 {
 544         down_write(&nommu_region_sem);
 545         __put_nommu_region(region);
 546 }
 547
 548 /*
 549  * add a VMA into a process's mm_struct in the appropriate place in the list
 550  * and tree and add to the address space's page tree also if not an anonymous
 551  * page
 552  * - should be called with mm->mmap_lock held writelocked
 553  */
 554 static void add_vma_to_mm(struct mm_struct *mm, struct vm_area_struct *vma)
 555 {
 556         struct vm_area_struct *pvma, *prev;
 557         struct address_space *mapping;
 558         struct rb_node **p, *parent, *rb_prev;
 559
 560         BUG_ON(!vma->vm_region);
 561
 562         mm->map_count++;
 563         vma->vm_mm = mm;
 564
 565         /* add the VMA to the mapping */
 566         if (vma->vm_file) {
 567                 mapping = vma->vm_file->f_mapping;
 568
 569                 i_mmap_lock_write(mapping);
 570                 flush_dcache_mmap_lock(mapping);
 571                 vma_interval_tree_insert(vma, &mapping->i_mmap);
 572                 flush_dcache_mmap_unlock(mapping);
 573                 i_mmap_unlock_write(mapping);
 574         }
 575
 576         /* add the VMA to the tree */
 577         parent = rb_prev = NULL;
 578         p = &mm->mm_rb.rb_node;
 579         while (*p) {
 580                 parent = *p;
 581                 pvma = rb_entry(parent, struct vm_area_struct, vm_rb);
 582
 583                 /* sort by: start addr, end addr, VMA struct addr in that order
 584                  * (the latter is necessary as we may get identical VMAs) */
 585                 if (vma->vm_start < pvma->vm_start)
 586                         p = &(*p)->rb_left;
 587                 else if (vma->vm_start > pvma->vm_start) {
 588                         rb_prev = parent;
 589                         p = &(*p)->rb_right;
 590                 } else if (vma->vm_end < pvma->vm_end)
 591                         p = &(*p)->rb_left;
 592                 else if (vma->vm_end > pvma->vm_end) {
 593                         rb_prev = parent;
 594                         p = &(*p)->rb_right;
 595                 } else if (vma < pvma)
 596                         p = &(*p)->rb_left;
 597                 else if (vma > pvma) {
 598                         rb_prev = parent;
 599                         p = &(*p)->rb_right;
 600                 } else
 601                         BUG();
 602         }
 603
 604         rb_link_node(&vma->vm_rb, parent, p);
 605         rb_insert_color(&vma->vm_rb, &mm->mm_rb);
 606
 607         /* add VMA to the VMA list also */
 608         prev = NULL;
 609         if (rb_prev)
 610                 prev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
 611
 612         __vma_link_list(mm, vma, prev);
 613 }
 614
 615 /*
 616  * delete a VMA from its owning mm_struct and address space
 617  */
 618 static void delete_vma_from_mm(struct vm_area_struct *vma)
 619 {
 620         int i;
 621         struct address_space *mapping;
 622         struct mm_struct *mm = vma->vm_mm;
 623         struct task_struct *curr = current;
 624
 625         mm->map_count--;
 626         for (i = 0; i < VMACACHE_SIZE; i++) {
 627                 /* if the vma is cached, invalidate the entire cache */
 628                 if (curr->vmacache.vmas[i] == vma) {
 629                         vmacache_invalidate(mm);
 630                         break;
 631                 }
 632         }
 633
 634         /* remove the VMA from the mapping */
 635         if (vma->vm_file) {
 636                 mapping = vma->vm_file->f_mapping;
 637
 638                 i_mmap_lock_write(mapping);
 639                 flush_dcache_mmap_lock(mapping);
 640                 vma_interval_tree_remove(vma, &mapping->i_mmap);
 641                 flush_dcache_mmap_unlock(mapping);
 642                 i_mmap_unlock_write(mapping);
 643         }
 644
 645         /* remove from the MM's tree and list */
 646         rb_erase(&vma->vm_rb, &mm->mm_rb);
 647
 648         __vma_unlink_list(mm, vma);
 649 }
 650
 651 /*
 652  * destroy a VMA record
 653  */
 654 static void delete_vma(struct mm_struct *mm, struct vm_area_struct *vma)
 655 {
 656         if (vma->vm_ops && vma->vm_ops->close)
 657                 vma->vm_ops->close(vma);
 658         if (vma->vm_file)
 659                 fput(vma->vm_file);
 660         put_nommu_region(vma->vm_region);
 661         vm_area_free(vma);
 662 }
 663
 664 /*
 665  * look up the first VMA in which addr resides, NULL if none
 666  * - should be called with mm->mmap_lock at least held readlocked
 667  */
 668 struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
 669 {
 670         struct vm_area_struct *vma;
 671
 672         /* check the cache first */
 673         vma = vmacache_find(mm, addr);
 674         if (likely(vma))
 675                 return vma;
 676
 677         /* trawl the list (there may be multiple mappings in which addr
 678          * resides) */
 679         for (vma = mm->mmap; vma; vma = vma->vm_next) {
 680                 if (vma->vm_start > addr)
 681                         return NULL;
 682                 if (vma->vm_end > addr) {
 683                         vmacache_update(addr, vma);
 684                         return vma;
 685                 }
 686         }
 687
 688         return NULL;
 689 }
 690 EXPORT_SYMBOL(find_vma);
 691
 692 /*
 693  * find a VMA
 694  * - we don't extend stack VMAs under NOMMU conditions
 695  */
 696 struct vm_area_struct *find_extend_vma(struct mm_struct *mm, unsigned long addr)
 697 {
 698         return find_vma(mm, addr);
 699 }
 700
 701 /*
 702  * expand a stack to a given address
 703  * - not supported under NOMMU conditions
 704  */
 705 int expand_stack(struct vm_area_struct *vma, unsigned long address)
 706 {
 707         return -ENOMEM;
 708 }
 709
 710 /*
 711  * look up the first VMA exactly that exactly matches addr
 712  * - should be called with mm->mmap_lock at least held readlocked
 713  */
 714 static struct vm_area_struct *find_vma_exact(struct mm_struct *mm,
 715                                              unsigned long addr,
 716                                              unsigned long len)
 717 {
 718         struct vm_area_struct *vma;
 719         unsigned long end = addr + len;
 720
 721         /* check the cache first */
 722         vma = vmacache_find_exact(mm, addr, end);
 723         if (vma)
 724                 return vma;
 725
 726         /* trawl the list (there may be multiple mappings in which addr
 727          * resides) */
 728         for (vma = mm->mmap; vma; vma = vma->vm_next) {
 729                 if (vma->vm_start < addr)
 730                         continue;
 731                 if (vma->vm_start > addr)
 732                         return NULL;
 733                 if (vma->vm_end == end) {
 734                         vmacache_update(addr, vma);
 735                         return vma;
 736                 }
 737         }
 738
 739         return NULL;
 740 }
 741
 742 /*
 743  * determine whether a mapping should be permitted and, if so, what sort of
 744  * mapping we're capable of supporting
 745  */
 746 static int validate_mmap_request(struct file *file,
 747                                  unsigned long addr,
 748                                  unsigned long len,
 749                                  unsigned long prot,
 750                                  unsigned long flags,
 751                                  unsigned long pgoff,
 752                                  unsigned long *_capabilities)
 753 {
 754         unsigned long capabilities, rlen;
 755         int ret;
 756
 757         /* do the simple checks first */
 758         if (flags & MAP_FIXED)
 759                 return -EINVAL;
 760
 761         if ((flags & MAP_TYPE) != MAP_PRIVATE &&
 762             (flags & MAP_TYPE) != MAP_SHARED)
 763                 return -EINVAL;
 764
 765         if (!len)
 766                 return -EINVAL;
 767
 768         /* Careful about overflows.. */
 769         rlen = PAGE_ALIGN(len);
 770         if (!rlen || rlen > TASK_SIZE)
 771                 return -ENOMEM;
 772
 773         /* offset overflow? */
 774         if ((pgoff + (rlen >> PAGE_SHIFT)) < pgoff)
 775                 return -EOVERFLOW;
 776
 777         if (file) {
 778                 /* files must support mmap */
 779                 if (!file->f_op->mmap)
 780                         return -ENODEV;
 781
 782                 /* work out if what we've got could possibly be shared
 783                  * - we support chardevs that provide their own "memory"
 784                  * - we support files/blockdevs that are memory backed
 785                  */
 786                 if (file->f_op->mmap_capabilities) {
 787                         capabilities = file->f_op->mmap_capabilities(file);
 788                 } else {
 789                         /* no explicit capabilities set, so assume some
 790                          * defaults */
 791                         switch (file_inode(file)->i_mode & S_IFMT) {
 792                         case S_IFREG:
 793                         case S_IFBLK:
 794                                 capabilities = NOMMU_MAP_COPY;
 795                                 break;
 796
 797                         case S_IFCHR:
 798                                 capabilities =
 799                                         NOMMU_MAP_DIRECT |
 800                                         NOMMU_MAP_READ |
 801                                         NOMMU_MAP_WRITE;
 802                                 break;
 803
 804                         default:
 805                                 return -EINVAL;
 806                         }
 807                 }
 808
 809                 /* eliminate any capabilities that we can't support on this
 810                  * device */
 811                 if (!file->f_op->get_unmapped_area)
 812                         capabilities &= ~NOMMU_MAP_DIRECT;
 813                 if (!(file->f_mode & FMODE_CAN_READ))
 814                         capabilities &= ~NOMMU_MAP_COPY;
 815
 816                 /* The file shall have been opened with read permission. */
 817                 if (!(file->f_mode & FMODE_READ))
 818                         return -EACCES;
 819
 820                 if (flags & MAP_SHARED) {
 821                         /* do checks for writing, appending and locking */
 822                         if ((prot & PROT_WRITE) &&
 823                             !(file->f_mode & FMODE_WRITE))
 824                                 return -EACCES;
 825
 826                         if (IS_APPEND(file_inode(file)) &&
 827                             (file->f_mode & FMODE_WRITE))
 828                                 return -EACCES;
 829
 830                         if (!(capabilities & NOMMU_MAP_DIRECT))
 831                                 return -ENODEV;
 832
 833                         /* we mustn't privatise shared mappings */
 834                         capabilities &= ~NOMMU_MAP_COPY;
 835                 } else {
 836                         /* we're going to read the file into private memory we
 837                          * allocate */
 838                         if (!(capabilities & NOMMU_MAP_COPY))
 839                                 return -ENODEV;
 840
 841                         /* we don't permit a private writable mapping to be
 842                          * shared with the backing device */
 843                         if (prot & PROT_WRITE)
 844                                 capabilities &= ~NOMMU_MAP_DIRECT;
 845                 }
 846
 847                 if (capabilities & NOMMU_MAP_DIRECT) {
 848                         if (((prot & PROT_READ)  && !(capabilities & NOMMU_MAP_READ))  ||
 849                             ((prot & PROT_WRITE) && !(capabilities & NOMMU_MAP_WRITE)) ||
 850                             ((prot & PROT_EXEC)  && !(capabilities & NOMMU_MAP_EXEC))
 851                             ) {
 852                                 capabilities &= ~NOMMU_MAP_DIRECT;
 853                                 if (flags & MAP_SHARED) {
 854                                         pr_warn("MAP_SHARED not completely supported on !MMU\n");
 855                                         return -EINVAL;
 856                                 }
 857                         }
 858                 }
 859
 860                 /* handle executable mappings and implied executable
 861                  * mappings */
 862                 if (path_noexec(&file->f_path)) {
 863                         if (prot & PROT_EXEC)
 864                                 return -EPERM;
 865                 } else if ((prot & PROT_READ) && !(prot & PROT_EXEC)) {
 866                         /* handle implication of PROT_EXEC by PROT_READ */
 867                         if (current->personality & READ_IMPLIES_EXEC) {
 868                                 if (capabilities & NOMMU_MAP_EXEC)
 869                                         prot |= PROT_EXEC;
 870                         }
 871                 } else if ((prot & PROT_READ) &&
 872                          (prot & PROT_EXEC) &&
 873                          !(capabilities & NOMMU_MAP_EXEC)
 874                          ) {
 875                         /* backing file is not executable, try to copy */
 876                         capabilities &= ~NOMMU_MAP_DIRECT;
 877                 }
 878         } else {
 879                 /* anonymous mappings are always memory backed and can be
 880                  * privately mapped
 881                  */
 882                 capabilities = NOMMU_MAP_COPY;
 883
 884                 /* handle PROT_EXEC implication by PROT_READ */
 885                 if ((prot & PROT_READ) &&
 886                     (current->personality & READ_IMPLIES_EXEC))
 887                         prot |= PROT_EXEC;
 888         }
 889
 890         /* allow the security API to have its say */
 891         ret = security_mmap_addr(addr);
 892         if (ret < 0)
 893                 return ret;
 894
 895         /* looks okay */
 896         *_capabilities = capabilities;
 897         return 0;
 898 }
 899
 900 /*
 901  * we've determined that we can make the mapping, now translate what we
 902  * now know into VMA flags
 903  */
 904 static unsigned long determine_vm_flags(struct file *file,
 905                                         unsigned long prot,
 906                                         unsigned long flags,
 907                                         unsigned long capabilities)
 908 {
 909         unsigned long vm_flags;
 910
 911         vm_flags = calc_vm_prot_bits(prot, 0) | calc_vm_flag_bits(flags);
 912         /* vm_flags |= mm->def_flags; */
 913
 914         if (!(capabilities & NOMMU_MAP_DIRECT)) {
 915                 /* attempt to share read-only copies of mapped file chunks */
 916                 vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
 917                 if (file && !(prot & PROT_WRITE))
 918                         vm_flags |= VM_MAYSHARE;
 919         } else {
 920                 /* overlay a shareable mapping on the backing device or inode
 921                  * if possible - used for chardevs, ramfs/tmpfs/shmfs and
 922                  * romfs/cramfs */
 923                 vm_flags |= VM_MAYSHARE | (capabilities & NOMMU_VMFLAGS);
 924                 if (flags & MAP_SHARED)
 925                         vm_flags |= VM_SHARED;
 926         }
 927
 928         /* refuse to let anyone share private mappings with this process if
 929          * it's being traced - otherwise breakpoints set in it may interfere
 930          * with another untraced process
 931          */
 932         if ((flags & MAP_PRIVATE) && current->ptrace)
 933                 vm_flags &= ~VM_MAYSHARE;
 934
 935         return vm_flags;
 936 }
 937
 938 /*
 939  * set up a shared mapping on a file (the driver or filesystem provides and
 940  * pins the storage)
 941  */
 942 static int do_mmap_shared_file(struct vm_area_struct *vma)
 943 {
 944         int ret;
 945
 946         ret = call_mmap(vma->vm_file, vma);
 947         if (ret == 0) {
 948                 vma->vm_region->vm_top = vma->vm_region->vm_end;
 949                 return 0;
 950         }
 951         if (ret != -ENOSYS)
 952                 return ret;
 953
 954         /* getting -ENOSYS indicates that direct mmap isn't possible (as
 955          * opposed to tried but failed) so we can only give a suitable error as
 956          * it's not possible to make a private copy if MAP_SHARED was given */
 957         return -ENODEV;
 958 }
 959
 960 /*
 961  * set up a private mapping or an anonymous shared mapping
 962  */
 963 static int do_mmap_private(struct vm_area_struct *vma,
 964                            struct vm_region *region,
 965                            unsigned long len,
 966                            unsigned long capabilities)
 967 {
 968         unsigned long total, point;
 969         void *base;
 970         int ret, order;
 971
 972         /* invoke the file's mapping function so that it can keep track of
 973          * shared mappings on devices or memory
 974          * - VM_MAYSHARE will be set if it may attempt to share
 975          */
 976         if (capabilities & NOMMU_MAP_DIRECT) {
 977                 ret = call_mmap(vma->vm_file, vma);
 978                 if (ret == 0) {
 979                         /* shouldn't return success if we're not sharing */
 980                         BUG_ON(!(vma->vm_flags & VM_MAYSHARE));
 981                         vma->vm_region->vm_top = vma->vm_region->vm_end;
 982                         return 0;
 983                 }
 984                 if (ret != -ENOSYS)
 985                         return ret;
 986
 987                 /* getting an ENOSYS error indicates that direct mmap isn't
 988                  * possible (as opposed to tried but failed) so we'll try to
 989                  * make a private copy of the data and map that instead */
 990         }
 991
 992
 993         /* allocate some memory to hold the mapping
 994          * - note that this may not return a page-aligned address if the object
 995          *   we're allocating is smaller than a page
 996          */
 997         order = get_order(len);
 998         total = 1 << order;
 999         point = len >> PAGE_SHIFT;
1000
1001         /* we don't want to allocate a power-of-2 sized page set */
1002         if (sysctl_nr_trim_pages && total - point >= sysctl_nr_trim_pages)
1003                 total = point;
1004
1005         base = alloc_pages_exact(total << PAGE_SHIFT, GFP_KERNEL);
1006         if (!base)
1007                 goto enomem;
1008
1009         atomic_long_add(total, &mmap_pages_allocated);
1010
1011         region->vm_flags = vma->vm_flags |= VM_MAPPED_COPY;
1012         region->vm_start = (unsigned long) base;
1013         region->vm_end   = region->vm_start + len;
1014         region->vm_top   = region->vm_start + (total << PAGE_SHIFT);
1015
1016         vma->vm_start = region->vm_start;
1017         vma->vm_end   = region->vm_start + len;
1018
1019         if (vma->vm_file) {
1020                 /* read the contents of a file into the copy */
1021                 loff_t fpos;
1022
1023                 fpos = vma->vm_pgoff;
1024                 fpos <<= PAGE_SHIFT;
1025
1026                 ret = kernel_read(vma->vm_file, base, len, &fpos);
1027                 if (ret < 0)
1028                         goto error_free;
1029
1030                 /* clear the last little bit */
1031                 if (ret < len)
1032                         memset(base + ret, 0, len - ret);
1033
1034         } else {
1035                 vma_set_anonymous(vma);
1036         }
1037
1038         return 0;
1039
1040 error_free:
1041         free_page_series(region->vm_start, region->vm_top);
1042         region->vm_start = vma->vm_start = 0;
1043         region->vm_end   = vma->vm_end = 0;
1044         region->vm_top   = 0;
1045         return ret;
1046
1047 enomem:
1048         pr_err("Allocation of length %lu from process %d (%s) failed\n",
1049                len, current->pid, current->comm);
1050         show_free_areas(0, NULL);
1051         return -ENOMEM;
1052 }
1053
1054 /*
1055  * handle mapping creation for uClinux
1056  */
1057 unsigned long do_mmap(struct file *file,
1058                         unsigned long addr,
1059                         unsigned long len,
1060                         unsigned long prot,
1061                         unsigned long flags,
1062                         unsigned long pgoff,
1063                         unsigned long *populate,
1064                         struct list_head *uf)
1065 {
1066         struct vm_area_struct *vma;
1067         struct vm_region *region;
1068         struct rb_node *rb;
1069         vm_flags_t vm_flags;
1070         unsigned long capabilities, result;
1071         int ret;
1072
1073         *populate = 0;
1074
1075         /* decide whether we should attempt the mapping, and if so what sort of
1076          * mapping */
1077         ret = validate_mmap_request(file, addr, len, prot, flags, pgoff,
1078                                     &capabilities);
1079         if (ret < 0)
1080                 return ret;
1081
1082         /* we ignore the address hint */
1083         addr = 0;
1084         len = PAGE_ALIGN(len);
1085
1086         /* we've determined that we can make the mapping, now translate what we
1087          * now know into VMA flags */
1088         vm_flags = determine_vm_flags(file, prot, flags, capabilities);
1089
1090         /* we're going to need to record the mapping */
1091         region = kmem_cache_zalloc(vm_region_jar, GFP_KERNEL);
1092         if (!region)
1093                 goto error_getting_region;
1094
1095         vma = vm_area_alloc(current->mm);
1096         if (!vma)
1097                 goto error_getting_vma;
1098
1099         region->vm_usage = 1;
1100         region->vm_flags = vm_flags;
1101         region->vm_pgoff = pgoff;
1102
1103         vma->vm_flags = vm_flags;
1104         vma->vm_pgoff = pgoff;
1105
1106         if (file) {
1107                 region->vm_file = get_file(file);
1108                 vma->vm_file = get_file(file);
1109         }
1110
1111         down_write(&nommu_region_sem);
1112
1113         /* if we want to share, we need to check for regions created by other
1114          * mmap() calls that overlap with our proposed mapping
1115          * - we can only share with a superset match on most regular files
1116          * - shared mappings on character devices and memory backed files are
1117          *   permitted to overlap inexactly as far as we are concerned for in
1118          *   these cases, sharing is handled in the driver or filesystem rather
1119          *   than here
1120          */
1121         if (vm_flags & VM_MAYSHARE) {
1122                 struct vm_region *pregion;
1123                 unsigned long pglen, rpglen, pgend, rpgend, start;
1124
1125                 pglen = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1126                 pgend = pgoff + pglen;
1127
1128                 for (rb = rb_first(&nommu_region_tree); rb; rb = rb_next(rb)) {
1129                         pregion = rb_entry(rb, struct vm_region, vm_rb);
1130
1131                         if (!(pregion->vm_flags & VM_MAYSHARE))
1132                                 continue;
1133
1134                         /* search for overlapping mappings on the same file */
1135                         if (file_inode(pregion->vm_file) !=
1136                             file_inode(file))
1137                                 continue;
1138
1139                         if (pregion->vm_pgoff >= pgend)
1140                                 continue;
1141
1142                         rpglen = pregion->vm_end - pregion->vm_start;
1143                         rpglen = (rpglen + PAGE_SIZE - 1) >> PAGE_SHIFT;
1144                         rpgend = pregion->vm_pgoff + rpglen;
1145                         if (pgoff >= rpgend)
1146                                 continue;
1147
1148                         /* handle inexactly overlapping matches between
1149                          * mappings */
1150                         if ((pregion->vm_pgoff != pgoff || rpglen != pglen) &&
1151                             !(pgoff >= pregion->vm_pgoff && pgend <= rpgend)) {
1152                                 /* new mapping is not a subset of the region */
1153                                 if (!(capabilities & NOMMU_MAP_DIRECT))
1154                                         goto sharing_violation;
1155                                 continue;
1156                         }
1157
1158                         /* we've found a region we can share */
1159                         pregion->vm_usage++;
1160                         vma->vm_region = pregion;
1161                         start = pregion->vm_start;
1162                         start += (pgoff - pregion->vm_pgoff) << PAGE_SHIFT;
1163                         vma->vm_start = start;
1164                         vma->vm_end = start + len;
1165
1166                         if (pregion->vm_flags & VM_MAPPED_COPY)
1167                                 vma->vm_flags |= VM_MAPPED_COPY;
1168                         else {
1169                                 ret = do_mmap_shared_file(vma);
1170                                 if (ret < 0) {
1171                                         vma->vm_region = NULL;
1172                                         vma->vm_start = 0;
1173                                         vma->vm_end = 0;
1174                                         pregion->vm_usage--;
1175                                         pregion = NULL;
1176                                         goto error_just_free;
1177                                 }
1178                         }
1179                         fput(region->vm_file);
1180                         kmem_cache_free(vm_region_jar, region);
1181                         region = pregion;
1182                         result = start;
1183                         goto share;
1184                 }
1185
1186                 /* obtain the address at which to make a shared mapping
1187                  * - this is the hook for quasi-memory character devices to
1188                  *   tell us the location of a shared mapping
1189                  */
1190                 if (capabilities & NOMMU_MAP_DIRECT) {
1191                         addr = file->f_op->get_unmapped_area(file, addr, len,
1192                                                              pgoff, flags);
1193                         if (IS_ERR_VALUE(addr)) {
1194                                 ret = addr;
1195                                 if (ret != -ENOSYS)
1196                                         goto error_just_free;
1197
1198                                 /* the driver refused to tell us where to site
1199                                  * the mapping so we'll have to attempt to copy
1200                                  * it */
1201                                 ret = -ENODEV;
1202                                 if (!(capabilities & NOMMU_MAP_COPY))
1203                                         goto error_just_free;
1204
1205                                 capabilities &= ~NOMMU_MAP_DIRECT;
1206                         } else {
1207                                 vma->vm_start = region->vm_start = addr;
1208                                 vma->vm_end = region->vm_end = addr + len;
1209                         }
1210                 }
1211         }
1212
1213         vma->vm_region = region;
1214
1215         /* set up the mapping
1216          * - the region is filled in if NOMMU_MAP_DIRECT is still set
1217          */
1218         if (file && vma->vm_flags & VM_SHARED)
1219                 ret = do_mmap_shared_file(vma);
1220         else
1221                 ret = do_mmap_private(vma, region, len, capabilities);
1222         if (ret < 0)
1223                 goto error_just_free;
1224         add_nommu_region(region);
1225
1226         /* clear anonymous mappings that don't ask for uninitialized data */
1227         if (!vma->vm_file &&
1228             (!IS_ENABLED(CONFIG_MMAP_ALLOW_UNINITIALIZED) ||
1229              !(flags & MAP_UNINITIALIZED)))
1230                 memset((void *)region->vm_start, 0,
1231                        region->vm_end - region->vm_start);
1232
1233         /* okay... we have a mapping; now we have to register it */
1234         result = vma->vm_start;
1235
1236         current->mm->total_vm += len >> PAGE_SHIFT;
1237
1238 share:
1239         add_vma_to_mm(current->mm, vma);
1240
1241         /* we flush the region from the icache only when the first executable
1242          * mapping of it is made  */
1243         if (vma->vm_flags & VM_EXEC && !region->vm_icache_flushed) {
1244                 flush_icache_user_range(region->vm_start, region->vm_end);
1245                 region->vm_icache_flushed = true;
1246         }
1247
1248         up_write(&nommu_region_sem);
1249
1250         return result;
1251
1252 error_just_free:
1253         up_write(&nommu_region_sem);
1254 error:
1255         if (region->vm_file)
1256                 fput(region->vm_file);
1257         kmem_cache_free(vm_region_jar, region);
1258         if (vma->vm_file)
1259                 fput(vma->vm_file);
1260         vm_area_free(vma);
1261         return ret;
1262
1263 sharing_violation:
1264         up_write(&nommu_region_sem);
1265         pr_warn("Attempt to share mismatched mappings\n");
1266         ret = -EINVAL;
1267         goto error;
1268
1269 error_getting_vma:
1270         kmem_cache_free(vm_region_jar, region);
1271         pr_warn("Allocation of vma for %lu byte allocation from process %d failed\n",
1272                         len, current->pid);
1273         show_free_areas(0, NULL);
1274         return -ENOMEM;
1275
1276 error_getting_region:
1277         pr_warn("Allocation of vm region for %lu byte allocation from process %d failed\n",
1278                         len, current->pid);
1279         show_free_areas(0, NULL);
1280         return -ENOMEM;
1281 }
1282
1283 unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
1284                               unsigned long prot, unsigned long flags,
1285                               unsigned long fd, unsigned long pgoff)
1286 {
1287         struct file *file = NULL;
1288         unsigned long retval = -EBADF;
1289
1290         audit_mmap_fd(fd, flags);
1291         if (!(flags & MAP_ANONYMOUS)) {
1292                 file = fget(fd);
1293                 if (!file)
1294                         goto out;
1295         }
1296
1297         retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
1298
1299         if (file)
1300                 fput(file);
1301 out:
1302         return retval;
1303 }
1304
1305 SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
1306                 unsigned long, prot, unsigned long, flags,
1307                 unsigned long, fd, unsigned long, pgoff)
1308 {
1309         return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
1310 }
1311
1312 #ifdef __ARCH_WANT_SYS_OLD_MMAP
1313 struct mmap_arg_struct {
1314         unsigned long addr;
1315         unsigned long len;
1316         unsigned long prot;
1317         unsigned long flags;
1318         unsigned long fd;
1319         unsigned long offset;
1320 };
1321
1322 SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
1323 {
1324         struct mmap_arg_struct a;
1325
1326         if (copy_from_user(&a, arg, sizeof(a)))
1327                 return -EFAULT;
1328         if (offset_in_page(a.offset))
1329                 return -EINVAL;
1330
1331         return ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
1332                                a.offset >> PAGE_SHIFT);
1333 }
1334 #endif /* __ARCH_WANT_SYS_OLD_MMAP */
1335
1336 /*
1337  * split a vma into two pieces at address 'addr', a new vma is allocated either
1338  * for the first part or the tail.
1339  */
1340 int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
1341               unsigned long addr, int new_below)
1342 {
1343         struct vm_area_struct *new;
1344         struct vm_region *region;
1345         unsigned long npages;
1346
1347         /* we're only permitted to split anonymous regions (these should have
1348          * only a single usage on the region) */
1349         if (vma->vm_file)
1350                 return -ENOMEM;
1351
1352         if (mm->map_count >= sysctl_max_map_count)
1353                 return -ENOMEM;
1354
1355         region = kmem_cache_alloc(vm_region_jar, GFP_KERNEL);
1356         if (!region)
1357                 return -ENOMEM;
1358
1359         new = vm_area_dup(vma);
1360         if (!new) {
1361                 kmem_cache_free(vm_region_jar, region);
1362                 return -ENOMEM;
1363         }
1364
1365         /* most fields are the same, copy all, and then fixup */
1366         *region = *vma->vm_region;
1367         new->vm_region = region;
1368
1369         npages = (addr - vma->vm_start) >> PAGE_SHIFT;
1370
1371         if (new_below) {
1372                 region->vm_top = region->vm_end = new->vm_end = addr;
1373         } else {
1374                 region->vm_start = new->vm_start = addr;
1375                 region->vm_pgoff = new->vm_pgoff += npages;
1376         }
1377
1378         if (new->vm_ops && new->vm_ops->open)
1379                 new->vm_ops->open(new);
1380
1381         delete_vma_from_mm(vma);
1382         down_write(&nommu_region_sem);
1383         delete_nommu_region(vma->vm_region);
1384         if (new_below) {
1385                 vma->vm_region->vm_start = vma->vm_start = addr;
1386                 vma->vm_region->vm_pgoff = vma->vm_pgoff += npages;
1387         } else {
1388                 vma->vm_region->vm_end = vma->vm_end = addr;
1389                 vma->vm_region->vm_top = addr;
1390         }
1391         add_nommu_region(vma->vm_region);
1392         add_nommu_region(new->vm_region);
1393         up_write(&nommu_region_sem);
1394         add_vma_to_mm(mm, vma);
1395         add_vma_to_mm(mm, new);
1396         return 0;
1397 }
1398
1399 /*
1400  * shrink a VMA by removing the specified chunk from either the beginning or
1401  * the end
1402  */
1403 static int shrink_vma(struct mm_struct *mm,
1404                       struct vm_area_struct *vma,
1405                       unsigned long from, unsigned long to)
1406 {
1407         struct vm_region *region;
1408
1409         /* adjust the VMA's pointers, which may reposition it in the MM's tree
1410          * and list */
1411         delete_vma_from_mm(vma);
1412         if (from > vma->vm_start)
1413                 vma->vm_end = from;
1414         else
1415                 vma->vm_start = to;
1416         add_vma_to_mm(mm, vma);
1417
1418         /* cut the backing region down to size */
1419         region = vma->vm_region;
1420         BUG_ON(region->vm_usage != 1);
1421
1422         down_write(&nommu_region_sem);
1423         delete_nommu_region(region);
1424         if (from > region->vm_start) {
1425                 to = region->vm_top;
1426                 region->vm_top = region->vm_end = from;
1427         } else {
1428                 region->vm_start = to;
1429         }
1430         add_nommu_region(region);
1431         up_write(&nommu_region_sem);
1432
1433         free_page_series(from, to);
1434         return 0;
1435 }
1436
1437 /*
1438  * release a mapping
1439  * - under NOMMU conditions the chunk to be unmapped must be backed by a single
1440  *   VMA, though it need not cover the whole VMA
1441  */
1442 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, struct list_head *uf)
1443 {
1444         struct vm_area_struct *vma;
1445         unsigned long end;
1446         int ret;
1447
1448         len = PAGE_ALIGN(len);
1449         if (len == 0)
1450                 return -EINVAL;
1451
1452         end = start + len;
1453
1454         /* find the first potentially overlapping VMA */
1455         vma = find_vma(mm, start);
1456         if (!vma) {
1457                 static int limit;
1458                 if (limit < 5) {
1459                         pr_warn("munmap of memory not mmapped by process %d (%s): 0x%lx-0x%lx\n",
1460                                         current->pid, current->comm,
1461                                         start, start + len - 1);
1462                         limit++;
1463                 }
1464                 return -EINVAL;
1465         }
1466
1467         /* we're allowed to split an anonymous VMA but not a file-backed one */
1468         if (vma->vm_file) {
1469                 do {
1470                         if (start > vma->vm_start)
1471                                 return -EINVAL;
1472                         if (end == vma->vm_end)
1473                                 goto erase_whole_vma;
1474                         vma = vma->vm_next;
1475                 } while (vma);
1476                 return -EINVAL;
1477         } else {
1478                 /* the chunk must be a subset of the VMA found */
1479                 if (start == vma->vm_start && end == vma->vm_end)
1480                         goto erase_whole_vma;
1481                 if (start < vma->vm_start || end > vma->vm_end)
1482                         return -EINVAL;
1483                 if (offset_in_page(start))
1484                         return -EINVAL;
1485                 if (end != vma->vm_end && offset_in_page(end))
1486                         return -EINVAL;
1487                 if (start != vma->vm_start && end != vma->vm_end) {
1488                         ret = split_vma(mm, vma, start, 1);
1489                         if (ret < 0)
1490                                 return ret;
1491                 }
1492                 return shrink_vma(mm, vma, start, end);
1493         }
1494
1495 erase_whole_vma:
1496         delete_vma_from_mm(vma);
1497         delete_vma(mm, vma);
1498         return 0;
1499 }
1500
1501 int vm_munmap(unsigned long addr, size_t len)
1502 {
1503         struct mm_struct *mm = current->mm;
1504         int ret;
1505
1506         mmap_write_lock(mm);
1507         ret = do_munmap(mm, addr, len, NULL);
1508         mmap_write_unlock(mm);
1509         return ret;
1510 }
1511 EXPORT_SYMBOL(vm_munmap);
1512
1513 SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
1514 {
1515         return vm_munmap(addr, len);
1516 }
1517
1518 /*
1519  * release all the mappings made in a process's VM space
1520  */
1521 void exit_mmap(struct mm_struct *mm)
1522 {
1523         struct vm_area_struct *vma;
1524
1525         if (!mm)
1526                 return;
1527
1528         mm->total_vm = 0;
1529
1530         while ((vma = mm->mmap)) {
1531                 mm->mmap = vma->vm_next;
1532                 delete_vma_from_mm(vma);
1533                 delete_vma(mm, vma);
1534                 cond_resched();
1535         }
1536 }
1537
1538 int vm_brk(unsigned long addr, unsigned long len)
1539 {
1540         return -ENOMEM;
1541 }
1542
1543 /*
1544  * expand (or shrink) an existing mapping, potentially moving it at the same
1545  * time (controlled by the MREMAP_MAYMOVE flag and available VM space)
1546  *
1547  * under NOMMU conditions, we only permit changing a mapping's size, and only
1548  * as long as it stays within the region allocated by do_mmap_private() and the
1549  * block is not shareable
1550  *
1551  * MREMAP_FIXED is not supported under NOMMU conditions
1552  */
1553 static unsigned long do_mremap(unsigned long addr,
1554                         unsigned long old_len, unsigned long new_len,
1555                         unsigned long flags, unsigned long new_addr)
1556 {
1557         struct vm_area_struct *vma;
1558
1559         /* insanity checks first */
1560         old_len = PAGE_ALIGN(old_len);
1561         new_len = PAGE_ALIGN(new_len);
1562         if (old_len == 0 || new_len == 0)
1563                 return (unsigned long) -EINVAL;
1564
1565         if (offset_in_page(addr))
1566                 return -EINVAL;
1567
1568         if (flags & MREMAP_FIXED && new_addr != addr)
1569                 return (unsigned long) -EINVAL;
1570
1571         vma = find_vma_exact(current->mm, addr, old_len);
1572         if (!vma)
1573                 return (unsigned long) -EINVAL;
1574
1575         if (vma->vm_end != vma->vm_start + old_len)
1576                 return (unsigned long) -EFAULT;
1577
1578         if (vma->vm_flags & VM_MAYSHARE)
1579                 return (unsigned long) -EPERM;
1580
1581         if (new_len > vma->vm_region->vm_end - vma->vm_region->vm_start)
1582                 return (unsigned long) -ENOMEM;
1583
1584         /* all checks complete - do it */
1585         vma->vm_end = vma->vm_start + new_len;
1586         return vma->vm_start;
1587 }
1588
1589 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
1590                 unsigned long, new_len, unsigned long, flags,
1591                 unsigned long, new_addr)
1592 {
1593         unsigned long ret;
1594
1595         mmap_write_lock(current->mm);
1596         ret = do_mremap(addr, old_len, new_len, flags, new_addr);
1597         mmap_write_unlock(current->mm);
1598         return ret;
1599 }
1600
1601 struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
1602                          unsigned int foll_flags)
1603 {
1604         return NULL;
1605 }
1606
1607 int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
1608                 unsigned long pfn, unsigned long size, pgprot_t prot)
1609 {
1610         if (addr != (pfn << PAGE_SHIFT))
1611                 return -EINVAL;
1612
1613         vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
1614         return 0;
1615 }
1616 EXPORT_SYMBOL(remap_pfn_range);
1617
1618 int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len)
1619 {
1620         unsigned long pfn = start >> PAGE_SHIFT;
1621         unsigned long vm_len = vma->vm_end - vma->vm_start;
1622
1623         pfn += vma->vm_pgoff;
1624         return io_remap_pfn_range(vma, vma->vm_start, pfn, vm_len, vma->vm_page_prot);
1625 }
1626 EXPORT_SYMBOL(vm_iomap_memory);
1627
1628 int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
1629                         unsigned long pgoff)
1630 {
1631         unsigned int size = vma->vm_end - vma->vm_start;
1632
1633         if (!(vma->vm_flags & VM_USERMAP))
1634                 return -EINVAL;
1635
1636         vma->vm_start = (unsigned long)(addr + (pgoff << PAGE_SHIFT));
1637         vma->vm_end = vma->vm_start + size;
1638
1639         return 0;
1640 }
1641 EXPORT_SYMBOL(remap_vmalloc_range);
1642
1643 vm_fault_t filemap_fault(struct vm_fault *vmf)
1644 {
1645         BUG();
1646         return 0;
1647 }
1648 EXPORT_SYMBOL(filemap_fault);
1649
1650 vm_fault_t filemap_map_pages(struct vm_fault *vmf,
1651                 pgoff_t start_pgoff, pgoff_t end_pgoff)
1652 {
1653         BUG();
1654         return 0;
1655 }
1656 EXPORT_SYMBOL(filemap_map_pages);
1657
1658 int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf,
1659                        int len, unsigned int gup_flags)
1660 {
1661         struct vm_area_struct *vma;
1662         int write = gup_flags & FOLL_WRITE;
1663
1664         if (mmap_read_lock_killable(mm))
1665                 return 0;
1666
1667         /* the access must start within one of the target process's mappings */
1668         vma = find_vma(mm, addr);
1669         if (vma) {
1670                 /* don't overrun this mapping */
1671                 if (addr + len >= vma->vm_end)
1672                         len = vma->vm_end - addr;
1673
1674                 /* only read or write mappings where it is permitted */
1675                 if (write && vma->vm_flags & VM_MAYWRITE)
1676                         copy_to_user_page(vma, NULL, addr,
1677                                          (void *) addr, buf, len);
1678                 else if (!write && vma->vm_flags & VM_MAYREAD)
1679                         copy_from_user_page(vma, NULL, addr,
1680                                             buf, (void *) addr, len);
1681                 else
1682                         len = 0;
1683         } else {
1684                 len = 0;
1685         }
1686
1687         mmap_read_unlock(mm);
1688
1689         return len;
1690 }
1691
1692 /**
1693  * access_remote_vm - access another process' address space
1694  * @mm:         the mm_struct of the target address space
1695  * @addr:       start address to access
1696  * @buf:        source or destination buffer
1697  * @len:        number of bytes to transfer
1698  * @gup_flags:  flags modifying lookup behaviour
1699  *
1700  * The caller must hold a reference on @mm.
1701  */
1702 int access_remote_vm(struct mm_struct *mm, unsigned long addr,
1703                 void *buf, int len, unsigned int gup_flags)
1704 {
1705         return __access_remote_vm(mm, addr, buf, len, gup_flags);
1706 }
1707
1708 /*
1709  * Access another process' address space.
1710  * - source/target buffer must be kernel space
1711  */
1712 int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len,
1713                 unsigned int gup_flags)
1714 {
1715         struct mm_struct *mm;
1716
1717         if (addr + len < addr)
1718                 return 0;
1719
1720         mm = get_task_mm(tsk);
1721         if (!mm)
1722                 return 0;
1723
1724         len = __access_remote_vm(mm, addr, buf, len, gup_flags);
1725
1726         mmput(mm);
1727         return len;
1728 }
1729 EXPORT_SYMBOL_GPL(access_process_vm);
1730
1731 /**
1732  * nommu_shrink_inode_mappings - Shrink the shared mappings on an inode
1733  * @inode: The inode to check
1734  * @size: The current filesize of the inode
1735  * @newsize: The proposed filesize of the inode
1736  *
1737  * Check the shared mappings on an inode on behalf of a shrinking truncate to
1738  * make sure that any outstanding VMAs aren't broken and then shrink the
1739  * vm_regions that extend beyond so that do_mmap() doesn't
1740  * automatically grant mappings that are too large.
1741  */
1742 int nommu_shrink_inode_mappings(struct inode *inode, size_t size,
1743                                 size_t newsize)
1744 {
1745         struct vm_area_struct *vma;
1746         struct vm_region *region;
1747         pgoff_t low, high;
1748         size_t r_size, r_top;
1749
1750         low = newsize >> PAGE_SHIFT;
1751         high = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1752
1753         down_write(&nommu_region_sem);
1754         i_mmap_lock_read(inode->i_mapping);
1755
1756         /* search for VMAs that fall within the dead zone */
1757         vma_interval_tree_foreach(vma, &inode->i_mapping->i_mmap, low, high) {
1758                 /* found one - only interested if it's shared out of the page
1759                  * cache */
1760                 if (vma->vm_flags & VM_SHARED) {
1761                         i_mmap_unlock_read(inode->i_mapping);
1762                         up_write(&nommu_region_sem);
1763                         return -ETXTBSY; /* not quite true, but near enough */
1764                 }
1765         }
1766
1767         /* reduce any regions that overlap the dead zone - if in existence,
1768          * these will be pointed to by VMAs that don't overlap the dead zone
1769          *
1770          * we don't check for any regions that start beyond the EOF as there
1771          * shouldn't be any
1772          */
1773         vma_interval_tree_foreach(vma, &inode->i_mapping->i_mmap, 0, ULONG_MAX) {
1774                 if (!(vma->vm_flags & VM_SHARED))
1775                         continue;
1776
1777                 region = vma->vm_region;
1778                 r_size = region->vm_top - region->vm_start;
1779                 r_top = (region->vm_pgoff << PAGE_SHIFT) + r_size;
1780
1781                 if (r_top > newsize) {
1782                         region->vm_top -= r_top - newsize;
1783                         if (region->vm_end > region->vm_top)
1784                                 region->vm_end = region->vm_top;
1785                 }
1786         }
1787
1788         i_mmap_unlock_read(inode->i_mapping);
1789         up_write(&nommu_region_sem);
1790         return 0;
1791 }
1792
1793 /*
1794  * Initialise sysctl_user_reserve_kbytes.
1795  *
1796  * This is intended to prevent a user from starting a single memory hogging
1797  * process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER
1798  * mode.
1799  *
1800  * The default value is min(3% of free memory, 128MB)
1801  * 128MB is enough to recover with sshd/login, bash, and top/kill.
1802  */
1803 static int __meminit init_user_reserve(void)
1804 {
1805         unsigned long free_kbytes;
1806
1807         free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
1808
1809         sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17);
1810         return 0;
1811 }
1812 subsys_initcall(init_user_reserve);
1813
1814 /*
1815  * Initialise sysctl_admin_reserve_kbytes.
1816  *
1817  * The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin
1818  * to log in and kill a memory hogging process.
1819  *
1820  * Systems with more than 256MB will reserve 8MB, enough to recover
1821  * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
1822  * only reserve 3% of free pages by default.
1823  */
1824 static int __meminit init_admin_reserve(void)
1825 {
1826         unsigned long free_kbytes;
1827
1828         free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
1829
1830         sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
1831         return 0;
1832 }
1833 subsys_initcall(init_admin_reserve);