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) 2004-2008 David Howells <dhowells@redhat.com> 10 * Copyright (c) 2000-2003 David McCullough <davidm@snapgear.com> 11 * Copyright (c) 2000-2001 D Jeff Dionne <jeff@uClinux.org> 12 * Copyright (c) 2002 Greg Ungerer <gerg@snapgear.com> 13 * Copyright (c) 2007-2010 Paul Mundt <lethal@linux-sh.org> 14 */ 15 16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 17 18 #include <linux/export.h> 19 #include <linux/mm.h> 20 #include <linux/vmacache.h> 21 #include <linux/mman.h> 22 #include <linux/swap.h> 23 #include <linux/file.h> 24 #include <linux/highmem.h> 25 #include <linux/pagemap.h> 26 #include <linux/slab.h> 27 #include <linux/vmalloc.h> 28 #include <linux/blkdev.h> 29 #include <linux/backing-dev.h> 30 #include <linux/compiler.h> 31 #include <linux/mount.h> 32 #include <linux/personality.h> 33 #include <linux/security.h> 34 #include <linux/syscalls.h> 35 #include <linux/audit.h> 36 #include <linux/sched/sysctl.h> 37 #include <linux/printk.h> 38 39 #include <asm/uaccess.h> 40 #include <asm/tlb.h> 41 #include <asm/tlbflush.h> 42 #include <asm/mmu_context.h> 43 #include "internal.h" 44 45 #if 0 46 #define kenter(FMT, ...) \ 47 printk(KERN_DEBUG "==> %s("FMT")\n", __func__, ##__VA_ARGS__) 48 #define kleave(FMT, ...) \ 49 printk(KERN_DEBUG "<== %s()"FMT"\n", __func__, ##__VA_ARGS__) 50 #define kdebug(FMT, ...) \ 51 printk(KERN_DEBUG "xxx" FMT"yyy\n", ##__VA_ARGS__) 52 #else 53 #define kenter(FMT, ...) \ 54 no_printk(KERN_DEBUG "==> %s("FMT")\n", __func__, ##__VA_ARGS__) 55 #define kleave(FMT, ...) \ 56 no_printk(KERN_DEBUG "<== %s()"FMT"\n", __func__, ##__VA_ARGS__) 57 #define kdebug(FMT, ...) \ 58 no_printk(KERN_DEBUG FMT"\n", ##__VA_ARGS__) 59 #endif 60 61 void *high_memory; 62 struct page *mem_map; 63 unsigned long max_mapnr; 64 unsigned long highest_memmap_pfn; 65 struct percpu_counter vm_committed_as; 66 int sysctl_overcommit_memory = OVERCOMMIT_GUESS; /* heuristic overcommit */ 67 int sysctl_overcommit_ratio = 50; /* default is 50% */ 68 unsigned long sysctl_overcommit_kbytes __read_mostly; 69 int sysctl_max_map_count = DEFAULT_MAX_MAP_COUNT; 70 int sysctl_nr_trim_pages = CONFIG_NOMMU_INITIAL_TRIM_EXCESS; 71 unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */ 72 unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */ 73 int heap_stack_gap = 0; 74 75 atomic_long_t mmap_pages_allocated; 76 77 /* 78 * The global memory commitment made in the system can be a metric 79 * that can be used to drive ballooning decisions when Linux is hosted 80 * as a guest. On Hyper-V, the host implements a policy engine for dynamically 81 * balancing memory across competing virtual machines that are hosted. 82 * Several metrics drive this policy engine including the guest reported 83 * memory commitment. 84 */ 85 unsigned long vm_memory_committed(void) 86 { 87 return percpu_counter_read_positive(&vm_committed_as); 88 } 89 90 EXPORT_SYMBOL_GPL(vm_memory_committed); 91 92 EXPORT_SYMBOL(mem_map); 93 94 /* list of mapped, potentially shareable regions */ 95 static struct kmem_cache *vm_region_jar; 96 struct rb_root nommu_region_tree = RB_ROOT; 97 DECLARE_RWSEM(nommu_region_sem); 98 99 const struct vm_operations_struct generic_file_vm_ops = { 100 }; 101 102 /* 103 * Return the total memory allocated for this pointer, not 104 * just what the caller asked for. 105 * 106 * Doesn't have to be accurate, i.e. may have races. 107 */ 108 unsigned int kobjsize(const void *objp) 109 { 110 struct page *page; 111 112 /* 113 * If the object we have should not have ksize performed on it, 114 * return size of 0 115 */ 116 if (!objp || !virt_addr_valid(objp)) 117 return 0; 118 119 page = virt_to_head_page(objp); 120 121 /* 122 * If the allocator sets PageSlab, we know the pointer came from 123 * kmalloc(). 124 */ 125 if (PageSlab(page)) 126 return ksize(objp); 127 128 /* 129 * If it's not a compound page, see if we have a matching VMA 130 * region. This test is intentionally done in reverse order, 131 * so if there's no VMA, we still fall through and hand back 132 * PAGE_SIZE for 0-order pages. 133 */ 134 if (!PageCompound(page)) { 135 struct vm_area_struct *vma; 136 137 vma = find_vma(current->mm, (unsigned long)objp); 138 if (vma) 139 return vma->vm_end - vma->vm_start; 140 } 141 142 /* 143 * The ksize() function is only guaranteed to work for pointers 144 * returned by kmalloc(). So handle arbitrary pointers here. 145 */ 146 return PAGE_SIZE << compound_order(page); 147 } 148 149 long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, 150 unsigned long start, unsigned long nr_pages, 151 unsigned int foll_flags, struct page **pages, 152 struct vm_area_struct **vmas, int *nonblocking) 153 { 154 struct vm_area_struct *vma; 155 unsigned long vm_flags; 156 int i; 157 158 /* calculate required read or write permissions. 159 * If FOLL_FORCE is set, we only require the "MAY" flags. 160 */ 161 vm_flags = (foll_flags & FOLL_WRITE) ? 162 (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD); 163 vm_flags &= (foll_flags & FOLL_FORCE) ? 164 (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE); 165 166 for (i = 0; i < nr_pages; i++) { 167 vma = find_vma(mm, start); 168 if (!vma) 169 goto finish_or_fault; 170 171 /* protect what we can, including chardevs */ 172 if ((vma->vm_flags & (VM_IO | VM_PFNMAP)) || 173 !(vm_flags & vma->vm_flags)) 174 goto finish_or_fault; 175 176 if (pages) { 177 pages[i] = virt_to_page(start); 178 if (pages[i]) 179 page_cache_get(pages[i]); 180 } 181 if (vmas) 182 vmas[i] = vma; 183 start = (start + PAGE_SIZE) & PAGE_MASK; 184 } 185 186 return i; 187 188 finish_or_fault: 189 return i ? : -EFAULT; 190 } 191 192 /* 193 * get a list of pages in an address range belonging to the specified process 194 * and indicate the VMA that covers each page 195 * - this is potentially dodgy as we may end incrementing the page count of a 196 * slab page or a secondary page from a compound page 197 * - don't permit access to VMAs that don't support it, such as I/O mappings 198 */ 199 long get_user_pages(struct task_struct *tsk, struct mm_struct *mm, 200 unsigned long start, unsigned long nr_pages, 201 int write, int force, struct page **pages, 202 struct vm_area_struct **vmas) 203 { 204 int flags = 0; 205 206 if (write) 207 flags |= FOLL_WRITE; 208 if (force) 209 flags |= FOLL_FORCE; 210 211 return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas, 212 NULL); 213 } 214 EXPORT_SYMBOL(get_user_pages); 215 216 /** 217 * follow_pfn - look up PFN at a user virtual address 218 * @vma: memory mapping 219 * @address: user virtual address 220 * @pfn: location to store found PFN 221 * 222 * Only IO mappings and raw PFN mappings are allowed. 223 * 224 * Returns zero and the pfn at @pfn on success, -ve otherwise. 225 */ 226 int follow_pfn(struct vm_area_struct *vma, unsigned long address, 227 unsigned long *pfn) 228 { 229 if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) 230 return -EINVAL; 231 232 *pfn = address >> PAGE_SHIFT; 233 return 0; 234 } 235 EXPORT_SYMBOL(follow_pfn); 236 237 LIST_HEAD(vmap_area_list); 238 239 void vfree(const void *addr) 240 { 241 kfree(addr); 242 } 243 EXPORT_SYMBOL(vfree); 244 245 void *__vmalloc(unsigned long size, gfp_t gfp_mask, pgprot_t prot) 246 { 247 /* 248 * You can't specify __GFP_HIGHMEM with kmalloc() since kmalloc() 249 * returns only a logical address. 250 */ 251 return kmalloc(size, (gfp_mask | __GFP_COMP) & ~__GFP_HIGHMEM); 252 } 253 EXPORT_SYMBOL(__vmalloc); 254 255 void *vmalloc_user(unsigned long size) 256 { 257 void *ret; 258 259 ret = __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO, 260 PAGE_KERNEL); 261 if (ret) { 262 struct vm_area_struct *vma; 263 264 down_write(¤t->mm->mmap_sem); 265 vma = find_vma(current->mm, (unsigned long)ret); 266 if (vma) 267 vma->vm_flags |= VM_USERMAP; 268 up_write(¤t->mm->mmap_sem); 269 } 270 271 return ret; 272 } 273 EXPORT_SYMBOL(vmalloc_user); 274 275 struct page *vmalloc_to_page(const void *addr) 276 { 277 return virt_to_page(addr); 278 } 279 EXPORT_SYMBOL(vmalloc_to_page); 280 281 unsigned long vmalloc_to_pfn(const void *addr) 282 { 283 return page_to_pfn(virt_to_page(addr)); 284 } 285 EXPORT_SYMBOL(vmalloc_to_pfn); 286 287 long vread(char *buf, char *addr, unsigned long count) 288 { 289 /* Don't allow overflow */ 290 if ((unsigned long) buf + count < count) 291 count = -(unsigned long) buf; 292 293 memcpy(buf, addr, count); 294 return count; 295 } 296 297 long vwrite(char *buf, char *addr, unsigned long count) 298 { 299 /* Don't allow overflow */ 300 if ((unsigned long) addr + count < count) 301 count = -(unsigned long) addr; 302 303 memcpy(addr, buf, count); 304 return count; 305 } 306 307 /* 308 * vmalloc - allocate virtually continguos memory 309 * 310 * @size: allocation size 311 * 312 * Allocate enough pages to cover @size from the page level 313 * allocator and map them into continguos kernel virtual space. 314 * 315 * For tight control over page level allocator and protection flags 316 * use __vmalloc() instead. 317 */ 318 void *vmalloc(unsigned long size) 319 { 320 return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL); 321 } 322 EXPORT_SYMBOL(vmalloc); 323 324 /* 325 * vzalloc - allocate virtually continguos memory with zero fill 326 * 327 * @size: allocation size 328 * 329 * Allocate enough pages to cover @size from the page level 330 * allocator and map them into continguos kernel virtual space. 331 * The memory allocated is set to zero. 332 * 333 * For tight control over page level allocator and protection flags 334 * use __vmalloc() instead. 335 */ 336 void *vzalloc(unsigned long size) 337 { 338 return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO, 339 PAGE_KERNEL); 340 } 341 EXPORT_SYMBOL(vzalloc); 342 343 /** 344 * vmalloc_node - allocate memory on a specific node 345 * @size: allocation size 346 * @node: numa node 347 * 348 * Allocate enough pages to cover @size from the page level 349 * allocator and map them into contiguous kernel virtual space. 350 * 351 * For tight control over page level allocator and protection flags 352 * use __vmalloc() instead. 353 */ 354 void *vmalloc_node(unsigned long size, int node) 355 { 356 return vmalloc(size); 357 } 358 EXPORT_SYMBOL(vmalloc_node); 359 360 /** 361 * vzalloc_node - allocate memory on a specific node with zero fill 362 * @size: allocation size 363 * @node: numa node 364 * 365 * Allocate enough pages to cover @size from the page level 366 * allocator and map them into contiguous kernel virtual space. 367 * The memory allocated is set to zero. 368 * 369 * For tight control over page level allocator and protection flags 370 * use __vmalloc() instead. 371 */ 372 void *vzalloc_node(unsigned long size, int node) 373 { 374 return vzalloc(size); 375 } 376 EXPORT_SYMBOL(vzalloc_node); 377 378 #ifndef PAGE_KERNEL_EXEC 379 # define PAGE_KERNEL_EXEC PAGE_KERNEL 380 #endif 381 382 /** 383 * vmalloc_exec - allocate virtually contiguous, executable memory 384 * @size: allocation size 385 * 386 * Kernel-internal function to allocate enough pages to cover @size 387 * the page level allocator and map them into contiguous and 388 * executable kernel virtual space. 389 * 390 * For tight control over page level allocator and protection flags 391 * use __vmalloc() instead. 392 */ 393 394 void *vmalloc_exec(unsigned long size) 395 { 396 return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL_EXEC); 397 } 398 399 /** 400 * vmalloc_32 - allocate virtually contiguous memory (32bit addressable) 401 * @size: allocation size 402 * 403 * Allocate enough 32bit PA addressable pages to cover @size from the 404 * page level allocator and map them into continguos kernel virtual space. 405 */ 406 void *vmalloc_32(unsigned long size) 407 { 408 return __vmalloc(size, GFP_KERNEL, PAGE_KERNEL); 409 } 410 EXPORT_SYMBOL(vmalloc_32); 411 412 /** 413 * vmalloc_32_user - allocate zeroed virtually contiguous 32bit memory 414 * @size: allocation size 415 * 416 * The resulting memory area is 32bit addressable and zeroed so it can be 417 * mapped to userspace without leaking data. 418 * 419 * VM_USERMAP is set on the corresponding VMA so that subsequent calls to 420 * remap_vmalloc_range() are permissible. 421 */ 422 void *vmalloc_32_user(unsigned long size) 423 { 424 /* 425 * We'll have to sort out the ZONE_DMA bits for 64-bit, 426 * but for now this can simply use vmalloc_user() directly. 427 */ 428 return vmalloc_user(size); 429 } 430 EXPORT_SYMBOL(vmalloc_32_user); 431 432 void *vmap(struct page **pages, unsigned int count, unsigned long flags, pgprot_t prot) 433 { 434 BUG(); 435 return NULL; 436 } 437 EXPORT_SYMBOL(vmap); 438 439 void vunmap(const void *addr) 440 { 441 BUG(); 442 } 443 EXPORT_SYMBOL(vunmap); 444 445 void *vm_map_ram(struct page **pages, unsigned int count, int node, pgprot_t prot) 446 { 447 BUG(); 448 return NULL; 449 } 450 EXPORT_SYMBOL(vm_map_ram); 451 452 void vm_unmap_ram(const void *mem, unsigned int count) 453 { 454 BUG(); 455 } 456 EXPORT_SYMBOL(vm_unmap_ram); 457 458 void vm_unmap_aliases(void) 459 { 460 } 461 EXPORT_SYMBOL_GPL(vm_unmap_aliases); 462 463 /* 464 * Implement a stub for vmalloc_sync_all() if the architecture chose not to 465 * have one. 466 */ 467 void __weak vmalloc_sync_all(void) 468 { 469 } 470 471 /** 472 * alloc_vm_area - allocate a range of kernel address space 473 * @size: size of the area 474 * 475 * Returns: NULL on failure, vm_struct on success 476 * 477 * This function reserves a range of kernel address space, and 478 * allocates pagetables to map that range. No actual mappings 479 * are created. If the kernel address space is not shared 480 * between processes, it syncs the pagetable across all 481 * processes. 482 */ 483 struct vm_struct *alloc_vm_area(size_t size, pte_t **ptes) 484 { 485 BUG(); 486 return NULL; 487 } 488 EXPORT_SYMBOL_GPL(alloc_vm_area); 489 490 void free_vm_area(struct vm_struct *area) 491 { 492 BUG(); 493 } 494 EXPORT_SYMBOL_GPL(free_vm_area); 495 496 int vm_insert_page(struct vm_area_struct *vma, unsigned long addr, 497 struct page *page) 498 { 499 return -EINVAL; 500 } 501 EXPORT_SYMBOL(vm_insert_page); 502 503 /* 504 * sys_brk() for the most part doesn't need the global kernel 505 * lock, except when an application is doing something nasty 506 * like trying to un-brk an area that has already been mapped 507 * to a regular file. in this case, the unmapping will need 508 * to invoke file system routines that need the global lock. 509 */ 510 SYSCALL_DEFINE1(brk, unsigned long, brk) 511 { 512 struct mm_struct *mm = current->mm; 513 514 if (brk < mm->start_brk || brk > mm->context.end_brk) 515 return mm->brk; 516 517 if (mm->brk == brk) 518 return mm->brk; 519 520 /* 521 * Always allow shrinking brk 522 */ 523 if (brk <= mm->brk) { 524 mm->brk = brk; 525 return brk; 526 } 527 528 /* 529 * Ok, looks good - let it rip. 530 */ 531 flush_icache_range(mm->brk, brk); 532 return mm->brk = brk; 533 } 534 535 /* 536 * initialise the VMA and region record slabs 537 */ 538 void __init mmap_init(void) 539 { 540 int ret; 541 542 ret = percpu_counter_init(&vm_committed_as, 0, GFP_KERNEL); 543 VM_BUG_ON(ret); 544 vm_region_jar = KMEM_CACHE(vm_region, SLAB_PANIC); 545 } 546 547 /* 548 * validate the region tree 549 * - the caller must hold the region lock 550 */ 551 #ifdef CONFIG_DEBUG_NOMMU_REGIONS 552 static noinline void validate_nommu_regions(void) 553 { 554 struct vm_region *region, *last; 555 struct rb_node *p, *lastp; 556 557 lastp = rb_first(&nommu_region_tree); 558 if (!lastp) 559 return; 560 561 last = rb_entry(lastp, struct vm_region, vm_rb); 562 BUG_ON(unlikely(last->vm_end <= last->vm_start)); 563 BUG_ON(unlikely(last->vm_top < last->vm_end)); 564 565 while ((p = rb_next(lastp))) { 566 region = rb_entry(p, struct vm_region, vm_rb); 567 last = rb_entry(lastp, struct vm_region, vm_rb); 568 569 BUG_ON(unlikely(region->vm_end <= region->vm_start)); 570 BUG_ON(unlikely(region->vm_top < region->vm_end)); 571 BUG_ON(unlikely(region->vm_start < last->vm_top)); 572 573 lastp = p; 574 } 575 } 576 #else 577 static void validate_nommu_regions(void) 578 { 579 } 580 #endif 581 582 /* 583 * add a region into the global tree 584 */ 585 static void add_nommu_region(struct vm_region *region) 586 { 587 struct vm_region *pregion; 588 struct rb_node **p, *parent; 589 590 validate_nommu_regions(); 591 592 parent = NULL; 593 p = &nommu_region_tree.rb_node; 594 while (*p) { 595 parent = *p; 596 pregion = rb_entry(parent, struct vm_region, vm_rb); 597 if (region->vm_start < pregion->vm_start) 598 p = &(*p)->rb_left; 599 else if (region->vm_start > pregion->vm_start) 600 p = &(*p)->rb_right; 601 else if (pregion == region) 602 return; 603 else 604 BUG(); 605 } 606 607 rb_link_node(®ion->vm_rb, parent, p); 608 rb_insert_color(®ion->vm_rb, &nommu_region_tree); 609 610 validate_nommu_regions(); 611 } 612 613 /* 614 * delete a region from the global tree 615 */ 616 static void delete_nommu_region(struct vm_region *region) 617 { 618 BUG_ON(!nommu_region_tree.rb_node); 619 620 validate_nommu_regions(); 621 rb_erase(®ion->vm_rb, &nommu_region_tree); 622 validate_nommu_regions(); 623 } 624 625 /* 626 * free a contiguous series of pages 627 */ 628 static void free_page_series(unsigned long from, unsigned long to) 629 { 630 for (; from < to; from += PAGE_SIZE) { 631 struct page *page = virt_to_page(from); 632 633 kdebug("- free %lx", from); 634 atomic_long_dec(&mmap_pages_allocated); 635 if (page_count(page) != 1) 636 kdebug("free page %p: refcount not one: %d", 637 page, page_count(page)); 638 put_page(page); 639 } 640 } 641 642 /* 643 * release a reference to a region 644 * - the caller must hold the region semaphore for writing, which this releases 645 * - the region may not have been added to the tree yet, in which case vm_top 646 * will equal vm_start 647 */ 648 static void __put_nommu_region(struct vm_region *region) 649 __releases(nommu_region_sem) 650 { 651 kenter("%p{%d}", region, region->vm_usage); 652 653 BUG_ON(!nommu_region_tree.rb_node); 654 655 if (--region->vm_usage == 0) { 656 if (region->vm_top > region->vm_start) 657 delete_nommu_region(region); 658 up_write(&nommu_region_sem); 659 660 if (region->vm_file) 661 fput(region->vm_file); 662 663 /* IO memory and memory shared directly out of the pagecache 664 * from ramfs/tmpfs mustn't be released here */ 665 if (region->vm_flags & VM_MAPPED_COPY) { 666 kdebug("free series"); 667 free_page_series(region->vm_start, region->vm_top); 668 } 669 kmem_cache_free(vm_region_jar, region); 670 } else { 671 up_write(&nommu_region_sem); 672 } 673 } 674 675 /* 676 * release a reference to a region 677 */ 678 static void put_nommu_region(struct vm_region *region) 679 { 680 down_write(&nommu_region_sem); 681 __put_nommu_region(region); 682 } 683 684 /* 685 * update protection on a vma 686 */ 687 static void protect_vma(struct vm_area_struct *vma, unsigned long flags) 688 { 689 #ifdef CONFIG_MPU 690 struct mm_struct *mm = vma->vm_mm; 691 long start = vma->vm_start & PAGE_MASK; 692 while (start < vma->vm_end) { 693 protect_page(mm, start, flags); 694 start += PAGE_SIZE; 695 } 696 update_protections(mm); 697 #endif 698 } 699 700 /* 701 * add a VMA into a process's mm_struct in the appropriate place in the list 702 * and tree and add to the address space's page tree also if not an anonymous 703 * page 704 * - should be called with mm->mmap_sem held writelocked 705 */ 706 static void add_vma_to_mm(struct mm_struct *mm, struct vm_area_struct *vma) 707 { 708 struct vm_area_struct *pvma, *prev; 709 struct address_space *mapping; 710 struct rb_node **p, *parent, *rb_prev; 711 712 kenter(",%p", vma); 713 714 BUG_ON(!vma->vm_region); 715 716 mm->map_count++; 717 vma->vm_mm = mm; 718 719 protect_vma(vma, vma->vm_flags); 720 721 /* add the VMA to the mapping */ 722 if (vma->vm_file) { 723 mapping = vma->vm_file->f_mapping; 724 725 mutex_lock(&mapping->i_mmap_mutex); 726 flush_dcache_mmap_lock(mapping); 727 vma_interval_tree_insert(vma, &mapping->i_mmap); 728 flush_dcache_mmap_unlock(mapping); 729 mutex_unlock(&mapping->i_mmap_mutex); 730 } 731 732 /* add the VMA to the tree */ 733 parent = rb_prev = NULL; 734 p = &mm->mm_rb.rb_node; 735 while (*p) { 736 parent = *p; 737 pvma = rb_entry(parent, struct vm_area_struct, vm_rb); 738 739 /* sort by: start addr, end addr, VMA struct addr in that order 740 * (the latter is necessary as we may get identical VMAs) */ 741 if (vma->vm_start < pvma->vm_start) 742 p = &(*p)->rb_left; 743 else if (vma->vm_start > pvma->vm_start) { 744 rb_prev = parent; 745 p = &(*p)->rb_right; 746 } else if (vma->vm_end < pvma->vm_end) 747 p = &(*p)->rb_left; 748 else if (vma->vm_end > pvma->vm_end) { 749 rb_prev = parent; 750 p = &(*p)->rb_right; 751 } else if (vma < pvma) 752 p = &(*p)->rb_left; 753 else if (vma > pvma) { 754 rb_prev = parent; 755 p = &(*p)->rb_right; 756 } else 757 BUG(); 758 } 759 760 rb_link_node(&vma->vm_rb, parent, p); 761 rb_insert_color(&vma->vm_rb, &mm->mm_rb); 762 763 /* add VMA to the VMA list also */ 764 prev = NULL; 765 if (rb_prev) 766 prev = rb_entry(rb_prev, struct vm_area_struct, vm_rb); 767 768 __vma_link_list(mm, vma, prev, parent); 769 } 770 771 /* 772 * delete a VMA from its owning mm_struct and address space 773 */ 774 static void delete_vma_from_mm(struct vm_area_struct *vma) 775 { 776 int i; 777 struct address_space *mapping; 778 struct mm_struct *mm = vma->vm_mm; 779 struct task_struct *curr = current; 780 781 kenter("%p", vma); 782 783 protect_vma(vma, 0); 784 785 mm->map_count--; 786 for (i = 0; i < VMACACHE_SIZE; i++) { 787 /* if the vma is cached, invalidate the entire cache */ 788 if (curr->vmacache[i] == vma) { 789 vmacache_invalidate(mm); 790 break; 791 } 792 } 793 794 /* remove the VMA from the mapping */ 795 if (vma->vm_file) { 796 mapping = vma->vm_file->f_mapping; 797 798 mutex_lock(&mapping->i_mmap_mutex); 799 flush_dcache_mmap_lock(mapping); 800 vma_interval_tree_remove(vma, &mapping->i_mmap); 801 flush_dcache_mmap_unlock(mapping); 802 mutex_unlock(&mapping->i_mmap_mutex); 803 } 804 805 /* remove from the MM's tree and list */ 806 rb_erase(&vma->vm_rb, &mm->mm_rb); 807 808 if (vma->vm_prev) 809 vma->vm_prev->vm_next = vma->vm_next; 810 else 811 mm->mmap = vma->vm_next; 812 813 if (vma->vm_next) 814 vma->vm_next->vm_prev = vma->vm_prev; 815 } 816 817 /* 818 * destroy a VMA record 819 */ 820 static void delete_vma(struct mm_struct *mm, struct vm_area_struct *vma) 821 { 822 kenter("%p", vma); 823 if (vma->vm_ops && vma->vm_ops->close) 824 vma->vm_ops->close(vma); 825 if (vma->vm_file) 826 fput(vma->vm_file); 827 put_nommu_region(vma->vm_region); 828 kmem_cache_free(vm_area_cachep, vma); 829 } 830 831 /* 832 * look up the first VMA in which addr resides, NULL if none 833 * - should be called with mm->mmap_sem at least held readlocked 834 */ 835 struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr) 836 { 837 struct vm_area_struct *vma; 838 839 /* check the cache first */ 840 vma = vmacache_find(mm, addr); 841 if (likely(vma)) 842 return vma; 843 844 /* trawl the list (there may be multiple mappings in which addr 845 * resides) */ 846 for (vma = mm->mmap; vma; vma = vma->vm_next) { 847 if (vma->vm_start > addr) 848 return NULL; 849 if (vma->vm_end > addr) { 850 vmacache_update(addr, vma); 851 return vma; 852 } 853 } 854 855 return NULL; 856 } 857 EXPORT_SYMBOL(find_vma); 858 859 /* 860 * find a VMA 861 * - we don't extend stack VMAs under NOMMU conditions 862 */ 863 struct vm_area_struct *find_extend_vma(struct mm_struct *mm, unsigned long addr) 864 { 865 return find_vma(mm, addr); 866 } 867 868 /* 869 * expand a stack to a given address 870 * - not supported under NOMMU conditions 871 */ 872 int expand_stack(struct vm_area_struct *vma, unsigned long address) 873 { 874 return -ENOMEM; 875 } 876 877 /* 878 * look up the first VMA exactly that exactly matches addr 879 * - should be called with mm->mmap_sem at least held readlocked 880 */ 881 static struct vm_area_struct *find_vma_exact(struct mm_struct *mm, 882 unsigned long addr, 883 unsigned long len) 884 { 885 struct vm_area_struct *vma; 886 unsigned long end = addr + len; 887 888 /* check the cache first */ 889 vma = vmacache_find_exact(mm, addr, end); 890 if (vma) 891 return vma; 892 893 /* trawl the list (there may be multiple mappings in which addr 894 * resides) */ 895 for (vma = mm->mmap; vma; vma = vma->vm_next) { 896 if (vma->vm_start < addr) 897 continue; 898 if (vma->vm_start > addr) 899 return NULL; 900 if (vma->vm_end == end) { 901 vmacache_update(addr, vma); 902 return vma; 903 } 904 } 905 906 return NULL; 907 } 908 909 /* 910 * determine whether a mapping should be permitted and, if so, what sort of 911 * mapping we're capable of supporting 912 */ 913 static int validate_mmap_request(struct file *file, 914 unsigned long addr, 915 unsigned long len, 916 unsigned long prot, 917 unsigned long flags, 918 unsigned long pgoff, 919 unsigned long *_capabilities) 920 { 921 unsigned long capabilities, rlen; 922 int ret; 923 924 /* do the simple checks first */ 925 if (flags & MAP_FIXED) { 926 printk(KERN_DEBUG 927 "%d: Can't do fixed-address/overlay mmap of RAM\n", 928 current->pid); 929 return -EINVAL; 930 } 931 932 if ((flags & MAP_TYPE) != MAP_PRIVATE && 933 (flags & MAP_TYPE) != MAP_SHARED) 934 return -EINVAL; 935 936 if (!len) 937 return -EINVAL; 938 939 /* Careful about overflows.. */ 940 rlen = PAGE_ALIGN(len); 941 if (!rlen || rlen > TASK_SIZE) 942 return -ENOMEM; 943 944 /* offset overflow? */ 945 if ((pgoff + (rlen >> PAGE_SHIFT)) < pgoff) 946 return -EOVERFLOW; 947 948 if (file) { 949 /* validate file mapping requests */ 950 struct address_space *mapping; 951 952 /* files must support mmap */ 953 if (!file->f_op->mmap) 954 return -ENODEV; 955 956 /* work out if what we've got could possibly be shared 957 * - we support chardevs that provide their own "memory" 958 * - we support files/blockdevs that are memory backed 959 */ 960 mapping = file->f_mapping; 961 if (!mapping) 962 mapping = file_inode(file)->i_mapping; 963 964 capabilities = 0; 965 if (mapping && mapping->backing_dev_info) 966 capabilities = mapping->backing_dev_info->capabilities; 967 968 if (!capabilities) { 969 /* no explicit capabilities set, so assume some 970 * defaults */ 971 switch (file_inode(file)->i_mode & S_IFMT) { 972 case S_IFREG: 973 case S_IFBLK: 974 capabilities = BDI_CAP_MAP_COPY; 975 break; 976 977 case S_IFCHR: 978 capabilities = 979 BDI_CAP_MAP_DIRECT | 980 BDI_CAP_READ_MAP | 981 BDI_CAP_WRITE_MAP; 982 break; 983 984 default: 985 return -EINVAL; 986 } 987 } 988 989 /* eliminate any capabilities that we can't support on this 990 * device */ 991 if (!file->f_op->get_unmapped_area) 992 capabilities &= ~BDI_CAP_MAP_DIRECT; 993 if (!file->f_op->read) 994 capabilities &= ~BDI_CAP_MAP_COPY; 995 996 /* The file shall have been opened with read permission. */ 997 if (!(file->f_mode & FMODE_READ)) 998 return -EACCES; 999 1000 if (flags & MAP_SHARED) { 1001 /* do checks for writing, appending and locking */ 1002 if ((prot & PROT_WRITE) && 1003 !(file->f_mode & FMODE_WRITE)) 1004 return -EACCES; 1005 1006 if (IS_APPEND(file_inode(file)) && 1007 (file->f_mode & FMODE_WRITE)) 1008 return -EACCES; 1009 1010 if (locks_verify_locked(file)) 1011 return -EAGAIN; 1012 1013 if (!(capabilities & BDI_CAP_MAP_DIRECT)) 1014 return -ENODEV; 1015 1016 /* we mustn't privatise shared mappings */ 1017 capabilities &= ~BDI_CAP_MAP_COPY; 1018 } else { 1019 /* we're going to read the file into private memory we 1020 * allocate */ 1021 if (!(capabilities & BDI_CAP_MAP_COPY)) 1022 return -ENODEV; 1023 1024 /* we don't permit a private writable mapping to be 1025 * shared with the backing device */ 1026 if (prot & PROT_WRITE) 1027 capabilities &= ~BDI_CAP_MAP_DIRECT; 1028 } 1029 1030 if (capabilities & BDI_CAP_MAP_DIRECT) { 1031 if (((prot & PROT_READ) && !(capabilities & BDI_CAP_READ_MAP)) || 1032 ((prot & PROT_WRITE) && !(capabilities & BDI_CAP_WRITE_MAP)) || 1033 ((prot & PROT_EXEC) && !(capabilities & BDI_CAP_EXEC_MAP)) 1034 ) { 1035 capabilities &= ~BDI_CAP_MAP_DIRECT; 1036 if (flags & MAP_SHARED) { 1037 printk(KERN_WARNING 1038 "MAP_SHARED not completely supported on !MMU\n"); 1039 return -EINVAL; 1040 } 1041 } 1042 } 1043 1044 /* handle executable mappings and implied executable 1045 * mappings */ 1046 if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) { 1047 if (prot & PROT_EXEC) 1048 return -EPERM; 1049 } else if ((prot & PROT_READ) && !(prot & PROT_EXEC)) { 1050 /* handle implication of PROT_EXEC by PROT_READ */ 1051 if (current->personality & READ_IMPLIES_EXEC) { 1052 if (capabilities & BDI_CAP_EXEC_MAP) 1053 prot |= PROT_EXEC; 1054 } 1055 } else if ((prot & PROT_READ) && 1056 (prot & PROT_EXEC) && 1057 !(capabilities & BDI_CAP_EXEC_MAP) 1058 ) { 1059 /* backing file is not executable, try to copy */ 1060 capabilities &= ~BDI_CAP_MAP_DIRECT; 1061 } 1062 } else { 1063 /* anonymous mappings are always memory backed and can be 1064 * privately mapped 1065 */ 1066 capabilities = BDI_CAP_MAP_COPY; 1067 1068 /* handle PROT_EXEC implication by PROT_READ */ 1069 if ((prot & PROT_READ) && 1070 (current->personality & READ_IMPLIES_EXEC)) 1071 prot |= PROT_EXEC; 1072 } 1073 1074 /* allow the security API to have its say */ 1075 ret = security_mmap_addr(addr); 1076 if (ret < 0) 1077 return ret; 1078 1079 /* looks okay */ 1080 *_capabilities = capabilities; 1081 return 0; 1082 } 1083 1084 /* 1085 * we've determined that we can make the mapping, now translate what we 1086 * now know into VMA flags 1087 */ 1088 static unsigned long determine_vm_flags(struct file *file, 1089 unsigned long prot, 1090 unsigned long flags, 1091 unsigned long capabilities) 1092 { 1093 unsigned long vm_flags; 1094 1095 vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags); 1096 /* vm_flags |= mm->def_flags; */ 1097 1098 if (!(capabilities & BDI_CAP_MAP_DIRECT)) { 1099 /* attempt to share read-only copies of mapped file chunks */ 1100 vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC; 1101 if (file && !(prot & PROT_WRITE)) 1102 vm_flags |= VM_MAYSHARE; 1103 } else { 1104 /* overlay a shareable mapping on the backing device or inode 1105 * if possible - used for chardevs, ramfs/tmpfs/shmfs and 1106 * romfs/cramfs */ 1107 vm_flags |= VM_MAYSHARE | (capabilities & BDI_CAP_VMFLAGS); 1108 if (flags & MAP_SHARED) 1109 vm_flags |= VM_SHARED; 1110 } 1111 1112 /* refuse to let anyone share private mappings with this process if 1113 * it's being traced - otherwise breakpoints set in it may interfere 1114 * with another untraced process 1115 */ 1116 if ((flags & MAP_PRIVATE) && current->ptrace) 1117 vm_flags &= ~VM_MAYSHARE; 1118 1119 return vm_flags; 1120 } 1121 1122 /* 1123 * set up a shared mapping on a file (the driver or filesystem provides and 1124 * pins the storage) 1125 */ 1126 static int do_mmap_shared_file(struct vm_area_struct *vma) 1127 { 1128 int ret; 1129 1130 ret = vma->vm_file->f_op->mmap(vma->vm_file, vma); 1131 if (ret == 0) { 1132 vma->vm_region->vm_top = vma->vm_region->vm_end; 1133 return 0; 1134 } 1135 if (ret != -ENOSYS) 1136 return ret; 1137 1138 /* getting -ENOSYS indicates that direct mmap isn't possible (as 1139 * opposed to tried but failed) so we can only give a suitable error as 1140 * it's not possible to make a private copy if MAP_SHARED was given */ 1141 return -ENODEV; 1142 } 1143 1144 /* 1145 * set up a private mapping or an anonymous shared mapping 1146 */ 1147 static int do_mmap_private(struct vm_area_struct *vma, 1148 struct vm_region *region, 1149 unsigned long len, 1150 unsigned long capabilities) 1151 { 1152 struct page *pages; 1153 unsigned long total, point, n; 1154 void *base; 1155 int ret, order; 1156 1157 /* invoke the file's mapping function so that it can keep track of 1158 * shared mappings on devices or memory 1159 * - VM_MAYSHARE will be set if it may attempt to share 1160 */ 1161 if (capabilities & BDI_CAP_MAP_DIRECT) { 1162 ret = vma->vm_file->f_op->mmap(vma->vm_file, vma); 1163 if (ret == 0) { 1164 /* shouldn't return success if we're not sharing */ 1165 BUG_ON(!(vma->vm_flags & VM_MAYSHARE)); 1166 vma->vm_region->vm_top = vma->vm_region->vm_end; 1167 return 0; 1168 } 1169 if (ret != -ENOSYS) 1170 return ret; 1171 1172 /* getting an ENOSYS error indicates that direct mmap isn't 1173 * possible (as opposed to tried but failed) so we'll try to 1174 * make a private copy of the data and map that instead */ 1175 } 1176 1177 1178 /* allocate some memory to hold the mapping 1179 * - note that this may not return a page-aligned address if the object 1180 * we're allocating is smaller than a page 1181 */ 1182 order = get_order(len); 1183 kdebug("alloc order %d for %lx", order, len); 1184 1185 pages = alloc_pages(GFP_KERNEL, order); 1186 if (!pages) 1187 goto enomem; 1188 1189 total = 1 << order; 1190 atomic_long_add(total, &mmap_pages_allocated); 1191 1192 point = len >> PAGE_SHIFT; 1193 1194 /* we allocated a power-of-2 sized page set, so we may want to trim off 1195 * the excess */ 1196 if (sysctl_nr_trim_pages && total - point >= sysctl_nr_trim_pages) { 1197 while (total > point) { 1198 order = ilog2(total - point); 1199 n = 1 << order; 1200 kdebug("shave %lu/%lu @%lu", n, total - point, total); 1201 atomic_long_sub(n, &mmap_pages_allocated); 1202 total -= n; 1203 set_page_refcounted(pages + total); 1204 __free_pages(pages + total, order); 1205 } 1206 } 1207 1208 for (point = 1; point < total; point++) 1209 set_page_refcounted(&pages[point]); 1210 1211 base = page_address(pages); 1212 region->vm_flags = vma->vm_flags |= VM_MAPPED_COPY; 1213 region->vm_start = (unsigned long) base; 1214 region->vm_end = region->vm_start + len; 1215 region->vm_top = region->vm_start + (total << PAGE_SHIFT); 1216 1217 vma->vm_start = region->vm_start; 1218 vma->vm_end = region->vm_start + len; 1219 1220 if (vma->vm_file) { 1221 /* read the contents of a file into the copy */ 1222 mm_segment_t old_fs; 1223 loff_t fpos; 1224 1225 fpos = vma->vm_pgoff; 1226 fpos <<= PAGE_SHIFT; 1227 1228 old_fs = get_fs(); 1229 set_fs(KERNEL_DS); 1230 ret = vma->vm_file->f_op->read(vma->vm_file, base, len, &fpos); 1231 set_fs(old_fs); 1232 1233 if (ret < 0) 1234 goto error_free; 1235 1236 /* clear the last little bit */ 1237 if (ret < len) 1238 memset(base + ret, 0, len - ret); 1239 1240 } 1241 1242 return 0; 1243 1244 error_free: 1245 free_page_series(region->vm_start, region->vm_top); 1246 region->vm_start = vma->vm_start = 0; 1247 region->vm_end = vma->vm_end = 0; 1248 region->vm_top = 0; 1249 return ret; 1250 1251 enomem: 1252 pr_err("Allocation of length %lu from process %d (%s) failed\n", 1253 len, current->pid, current->comm); 1254 show_free_areas(0); 1255 return -ENOMEM; 1256 } 1257 1258 /* 1259 * handle mapping creation for uClinux 1260 */ 1261 unsigned long do_mmap_pgoff(struct file *file, 1262 unsigned long addr, 1263 unsigned long len, 1264 unsigned long prot, 1265 unsigned long flags, 1266 unsigned long pgoff, 1267 unsigned long *populate) 1268 { 1269 struct vm_area_struct *vma; 1270 struct vm_region *region; 1271 struct rb_node *rb; 1272 unsigned long capabilities, vm_flags, result; 1273 int ret; 1274 1275 kenter(",%lx,%lx,%lx,%lx,%lx", addr, len, prot, flags, pgoff); 1276 1277 *populate = 0; 1278 1279 /* decide whether we should attempt the mapping, and if so what sort of 1280 * mapping */ 1281 ret = validate_mmap_request(file, addr, len, prot, flags, pgoff, 1282 &capabilities); 1283 if (ret < 0) { 1284 kleave(" = %d [val]", ret); 1285 return ret; 1286 } 1287 1288 /* we ignore the address hint */ 1289 addr = 0; 1290 len = PAGE_ALIGN(len); 1291 1292 /* we've determined that we can make the mapping, now translate what we 1293 * now know into VMA flags */ 1294 vm_flags = determine_vm_flags(file, prot, flags, capabilities); 1295 1296 /* we're going to need to record the mapping */ 1297 region = kmem_cache_zalloc(vm_region_jar, GFP_KERNEL); 1298 if (!region) 1299 goto error_getting_region; 1300 1301 vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL); 1302 if (!vma) 1303 goto error_getting_vma; 1304 1305 region->vm_usage = 1; 1306 region->vm_flags = vm_flags; 1307 region->vm_pgoff = pgoff; 1308 1309 INIT_LIST_HEAD(&vma->anon_vma_chain); 1310 vma->vm_flags = vm_flags; 1311 vma->vm_pgoff = pgoff; 1312 1313 if (file) { 1314 region->vm_file = get_file(file); 1315 vma->vm_file = get_file(file); 1316 } 1317 1318 down_write(&nommu_region_sem); 1319 1320 /* if we want to share, we need to check for regions created by other 1321 * mmap() calls that overlap with our proposed mapping 1322 * - we can only share with a superset match on most regular files 1323 * - shared mappings on character devices and memory backed files are 1324 * permitted to overlap inexactly as far as we are concerned for in 1325 * these cases, sharing is handled in the driver or filesystem rather 1326 * than here 1327 */ 1328 if (vm_flags & VM_MAYSHARE) { 1329 struct vm_region *pregion; 1330 unsigned long pglen, rpglen, pgend, rpgend, start; 1331 1332 pglen = (len + PAGE_SIZE - 1) >> PAGE_SHIFT; 1333 pgend = pgoff + pglen; 1334 1335 for (rb = rb_first(&nommu_region_tree); rb; rb = rb_next(rb)) { 1336 pregion = rb_entry(rb, struct vm_region, vm_rb); 1337 1338 if (!(pregion->vm_flags & VM_MAYSHARE)) 1339 continue; 1340 1341 /* search for overlapping mappings on the same file */ 1342 if (file_inode(pregion->vm_file) != 1343 file_inode(file)) 1344 continue; 1345 1346 if (pregion->vm_pgoff >= pgend) 1347 continue; 1348 1349 rpglen = pregion->vm_end - pregion->vm_start; 1350 rpglen = (rpglen + PAGE_SIZE - 1) >> PAGE_SHIFT; 1351 rpgend = pregion->vm_pgoff + rpglen; 1352 if (pgoff >= rpgend) 1353 continue; 1354 1355 /* handle inexactly overlapping matches between 1356 * mappings */ 1357 if ((pregion->vm_pgoff != pgoff || rpglen != pglen) && 1358 !(pgoff >= pregion->vm_pgoff && pgend <= rpgend)) { 1359 /* new mapping is not a subset of the region */ 1360 if (!(capabilities & BDI_CAP_MAP_DIRECT)) 1361 goto sharing_violation; 1362 continue; 1363 } 1364 1365 /* we've found a region we can share */ 1366 pregion->vm_usage++; 1367 vma->vm_region = pregion; 1368 start = pregion->vm_start; 1369 start += (pgoff - pregion->vm_pgoff) << PAGE_SHIFT; 1370 vma->vm_start = start; 1371 vma->vm_end = start + len; 1372 1373 if (pregion->vm_flags & VM_MAPPED_COPY) { 1374 kdebug("share copy"); 1375 vma->vm_flags |= VM_MAPPED_COPY; 1376 } else { 1377 kdebug("share mmap"); 1378 ret = do_mmap_shared_file(vma); 1379 if (ret < 0) { 1380 vma->vm_region = NULL; 1381 vma->vm_start = 0; 1382 vma->vm_end = 0; 1383 pregion->vm_usage--; 1384 pregion = NULL; 1385 goto error_just_free; 1386 } 1387 } 1388 fput(region->vm_file); 1389 kmem_cache_free(vm_region_jar, region); 1390 region = pregion; 1391 result = start; 1392 goto share; 1393 } 1394 1395 /* obtain the address at which to make a shared mapping 1396 * - this is the hook for quasi-memory character devices to 1397 * tell us the location of a shared mapping 1398 */ 1399 if (capabilities & BDI_CAP_MAP_DIRECT) { 1400 addr = file->f_op->get_unmapped_area(file, addr, len, 1401 pgoff, flags); 1402 if (IS_ERR_VALUE(addr)) { 1403 ret = addr; 1404 if (ret != -ENOSYS) 1405 goto error_just_free; 1406 1407 /* the driver refused to tell us where to site 1408 * the mapping so we'll have to attempt to copy 1409 * it */ 1410 ret = -ENODEV; 1411 if (!(capabilities & BDI_CAP_MAP_COPY)) 1412 goto error_just_free; 1413 1414 capabilities &= ~BDI_CAP_MAP_DIRECT; 1415 } else { 1416 vma->vm_start = region->vm_start = addr; 1417 vma->vm_end = region->vm_end = addr + len; 1418 } 1419 } 1420 } 1421 1422 vma->vm_region = region; 1423 1424 /* set up the mapping 1425 * - the region is filled in if BDI_CAP_MAP_DIRECT is still set 1426 */ 1427 if (file && vma->vm_flags & VM_SHARED) 1428 ret = do_mmap_shared_file(vma); 1429 else 1430 ret = do_mmap_private(vma, region, len, capabilities); 1431 if (ret < 0) 1432 goto error_just_free; 1433 add_nommu_region(region); 1434 1435 /* clear anonymous mappings that don't ask for uninitialized data */ 1436 if (!vma->vm_file && !(flags & MAP_UNINITIALIZED)) 1437 memset((void *)region->vm_start, 0, 1438 region->vm_end - region->vm_start); 1439 1440 /* okay... we have a mapping; now we have to register it */ 1441 result = vma->vm_start; 1442 1443 current->mm->total_vm += len >> PAGE_SHIFT; 1444 1445 share: 1446 add_vma_to_mm(current->mm, vma); 1447 1448 /* we flush the region from the icache only when the first executable 1449 * mapping of it is made */ 1450 if (vma->vm_flags & VM_EXEC && !region->vm_icache_flushed) { 1451 flush_icache_range(region->vm_start, region->vm_end); 1452 region->vm_icache_flushed = true; 1453 } 1454 1455 up_write(&nommu_region_sem); 1456 1457 kleave(" = %lx", result); 1458 return result; 1459 1460 error_just_free: 1461 up_write(&nommu_region_sem); 1462 error: 1463 if (region->vm_file) 1464 fput(region->vm_file); 1465 kmem_cache_free(vm_region_jar, region); 1466 if (vma->vm_file) 1467 fput(vma->vm_file); 1468 kmem_cache_free(vm_area_cachep, vma); 1469 kleave(" = %d", ret); 1470 return ret; 1471 1472 sharing_violation: 1473 up_write(&nommu_region_sem); 1474 printk(KERN_WARNING "Attempt to share mismatched mappings\n"); 1475 ret = -EINVAL; 1476 goto error; 1477 1478 error_getting_vma: 1479 kmem_cache_free(vm_region_jar, region); 1480 printk(KERN_WARNING "Allocation of vma for %lu byte allocation" 1481 " from process %d failed\n", 1482 len, current->pid); 1483 show_free_areas(0); 1484 return -ENOMEM; 1485 1486 error_getting_region: 1487 printk(KERN_WARNING "Allocation of vm region for %lu byte allocation" 1488 " from process %d failed\n", 1489 len, current->pid); 1490 show_free_areas(0); 1491 return -ENOMEM; 1492 } 1493 1494 SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len, 1495 unsigned long, prot, unsigned long, flags, 1496 unsigned long, fd, unsigned long, pgoff) 1497 { 1498 struct file *file = NULL; 1499 unsigned long retval = -EBADF; 1500 1501 audit_mmap_fd(fd, flags); 1502 if (!(flags & MAP_ANONYMOUS)) { 1503 file = fget(fd); 1504 if (!file) 1505 goto out; 1506 } 1507 1508 flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE); 1509 1510 retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff); 1511 1512 if (file) 1513 fput(file); 1514 out: 1515 return retval; 1516 } 1517 1518 #ifdef __ARCH_WANT_SYS_OLD_MMAP 1519 struct mmap_arg_struct { 1520 unsigned long addr; 1521 unsigned long len; 1522 unsigned long prot; 1523 unsigned long flags; 1524 unsigned long fd; 1525 unsigned long offset; 1526 }; 1527 1528 SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg) 1529 { 1530 struct mmap_arg_struct a; 1531 1532 if (copy_from_user(&a, arg, sizeof(a))) 1533 return -EFAULT; 1534 if (a.offset & ~PAGE_MASK) 1535 return -EINVAL; 1536 1537 return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd, 1538 a.offset >> PAGE_SHIFT); 1539 } 1540 #endif /* __ARCH_WANT_SYS_OLD_MMAP */ 1541 1542 /* 1543 * split a vma into two pieces at address 'addr', a new vma is allocated either 1544 * for the first part or the tail. 1545 */ 1546 int split_vma(struct mm_struct *mm, struct vm_area_struct *vma, 1547 unsigned long addr, int new_below) 1548 { 1549 struct vm_area_struct *new; 1550 struct vm_region *region; 1551 unsigned long npages; 1552 1553 kenter(""); 1554 1555 /* we're only permitted to split anonymous regions (these should have 1556 * only a single usage on the region) */ 1557 if (vma->vm_file) 1558 return -ENOMEM; 1559 1560 if (mm->map_count >= sysctl_max_map_count) 1561 return -ENOMEM; 1562 1563 region = kmem_cache_alloc(vm_region_jar, GFP_KERNEL); 1564 if (!region) 1565 return -ENOMEM; 1566 1567 new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 1568 if (!new) { 1569 kmem_cache_free(vm_region_jar, region); 1570 return -ENOMEM; 1571 } 1572 1573 /* most fields are the same, copy all, and then fixup */ 1574 *new = *vma; 1575 *region = *vma->vm_region; 1576 new->vm_region = region; 1577 1578 npages = (addr - vma->vm_start) >> PAGE_SHIFT; 1579 1580 if (new_below) { 1581 region->vm_top = region->vm_end = new->vm_end = addr; 1582 } else { 1583 region->vm_start = new->vm_start = addr; 1584 region->vm_pgoff = new->vm_pgoff += npages; 1585 } 1586 1587 if (new->vm_ops && new->vm_ops->open) 1588 new->vm_ops->open(new); 1589 1590 delete_vma_from_mm(vma); 1591 down_write(&nommu_region_sem); 1592 delete_nommu_region(vma->vm_region); 1593 if (new_below) { 1594 vma->vm_region->vm_start = vma->vm_start = addr; 1595 vma->vm_region->vm_pgoff = vma->vm_pgoff += npages; 1596 } else { 1597 vma->vm_region->vm_end = vma->vm_end = addr; 1598 vma->vm_region->vm_top = addr; 1599 } 1600 add_nommu_region(vma->vm_region); 1601 add_nommu_region(new->vm_region); 1602 up_write(&nommu_region_sem); 1603 add_vma_to_mm(mm, vma); 1604 add_vma_to_mm(mm, new); 1605 return 0; 1606 } 1607 1608 /* 1609 * shrink a VMA by removing the specified chunk from either the beginning or 1610 * the end 1611 */ 1612 static int shrink_vma(struct mm_struct *mm, 1613 struct vm_area_struct *vma, 1614 unsigned long from, unsigned long to) 1615 { 1616 struct vm_region *region; 1617 1618 kenter(""); 1619 1620 /* adjust the VMA's pointers, which may reposition it in the MM's tree 1621 * and list */ 1622 delete_vma_from_mm(vma); 1623 if (from > vma->vm_start) 1624 vma->vm_end = from; 1625 else 1626 vma->vm_start = to; 1627 add_vma_to_mm(mm, vma); 1628 1629 /* cut the backing region down to size */ 1630 region = vma->vm_region; 1631 BUG_ON(region->vm_usage != 1); 1632 1633 down_write(&nommu_region_sem); 1634 delete_nommu_region(region); 1635 if (from > region->vm_start) { 1636 to = region->vm_top; 1637 region->vm_top = region->vm_end = from; 1638 } else { 1639 region->vm_start = to; 1640 } 1641 add_nommu_region(region); 1642 up_write(&nommu_region_sem); 1643 1644 free_page_series(from, to); 1645 return 0; 1646 } 1647 1648 /* 1649 * release a mapping 1650 * - under NOMMU conditions the chunk to be unmapped must be backed by a single 1651 * VMA, though it need not cover the whole VMA 1652 */ 1653 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len) 1654 { 1655 struct vm_area_struct *vma; 1656 unsigned long end; 1657 int ret; 1658 1659 kenter(",%lx,%zx", start, len); 1660 1661 len = PAGE_ALIGN(len); 1662 if (len == 0) 1663 return -EINVAL; 1664 1665 end = start + len; 1666 1667 /* find the first potentially overlapping VMA */ 1668 vma = find_vma(mm, start); 1669 if (!vma) { 1670 static int limit; 1671 if (limit < 5) { 1672 printk(KERN_WARNING 1673 "munmap of memory not mmapped by process %d" 1674 " (%s): 0x%lx-0x%lx\n", 1675 current->pid, current->comm, 1676 start, start + len - 1); 1677 limit++; 1678 } 1679 return -EINVAL; 1680 } 1681 1682 /* we're allowed to split an anonymous VMA but not a file-backed one */ 1683 if (vma->vm_file) { 1684 do { 1685 if (start > vma->vm_start) { 1686 kleave(" = -EINVAL [miss]"); 1687 return -EINVAL; 1688 } 1689 if (end == vma->vm_end) 1690 goto erase_whole_vma; 1691 vma = vma->vm_next; 1692 } while (vma); 1693 kleave(" = -EINVAL [split file]"); 1694 return -EINVAL; 1695 } else { 1696 /* the chunk must be a subset of the VMA found */ 1697 if (start == vma->vm_start && end == vma->vm_end) 1698 goto erase_whole_vma; 1699 if (start < vma->vm_start || end > vma->vm_end) { 1700 kleave(" = -EINVAL [superset]"); 1701 return -EINVAL; 1702 } 1703 if (start & ~PAGE_MASK) { 1704 kleave(" = -EINVAL [unaligned start]"); 1705 return -EINVAL; 1706 } 1707 if (end != vma->vm_end && end & ~PAGE_MASK) { 1708 kleave(" = -EINVAL [unaligned split]"); 1709 return -EINVAL; 1710 } 1711 if (start != vma->vm_start && end != vma->vm_end) { 1712 ret = split_vma(mm, vma, start, 1); 1713 if (ret < 0) { 1714 kleave(" = %d [split]", ret); 1715 return ret; 1716 } 1717 } 1718 return shrink_vma(mm, vma, start, end); 1719 } 1720 1721 erase_whole_vma: 1722 delete_vma_from_mm(vma); 1723 delete_vma(mm, vma); 1724 kleave(" = 0"); 1725 return 0; 1726 } 1727 EXPORT_SYMBOL(do_munmap); 1728 1729 int vm_munmap(unsigned long addr, size_t len) 1730 { 1731 struct mm_struct *mm = current->mm; 1732 int ret; 1733 1734 down_write(&mm->mmap_sem); 1735 ret = do_munmap(mm, addr, len); 1736 up_write(&mm->mmap_sem); 1737 return ret; 1738 } 1739 EXPORT_SYMBOL(vm_munmap); 1740 1741 SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len) 1742 { 1743 return vm_munmap(addr, len); 1744 } 1745 1746 /* 1747 * release all the mappings made in a process's VM space 1748 */ 1749 void exit_mmap(struct mm_struct *mm) 1750 { 1751 struct vm_area_struct *vma; 1752 1753 if (!mm) 1754 return; 1755 1756 kenter(""); 1757 1758 mm->total_vm = 0; 1759 1760 while ((vma = mm->mmap)) { 1761 mm->mmap = vma->vm_next; 1762 delete_vma_from_mm(vma); 1763 delete_vma(mm, vma); 1764 cond_resched(); 1765 } 1766 1767 kleave(""); 1768 } 1769 1770 unsigned long vm_brk(unsigned long addr, unsigned long len) 1771 { 1772 return -ENOMEM; 1773 } 1774 1775 /* 1776 * expand (or shrink) an existing mapping, potentially moving it at the same 1777 * time (controlled by the MREMAP_MAYMOVE flag and available VM space) 1778 * 1779 * under NOMMU conditions, we only permit changing a mapping's size, and only 1780 * as long as it stays within the region allocated by do_mmap_private() and the 1781 * block is not shareable 1782 * 1783 * MREMAP_FIXED is not supported under NOMMU conditions 1784 */ 1785 static unsigned long do_mremap(unsigned long addr, 1786 unsigned long old_len, unsigned long new_len, 1787 unsigned long flags, unsigned long new_addr) 1788 { 1789 struct vm_area_struct *vma; 1790 1791 /* insanity checks first */ 1792 old_len = PAGE_ALIGN(old_len); 1793 new_len = PAGE_ALIGN(new_len); 1794 if (old_len == 0 || new_len == 0) 1795 return (unsigned long) -EINVAL; 1796 1797 if (addr & ~PAGE_MASK) 1798 return -EINVAL; 1799 1800 if (flags & MREMAP_FIXED && new_addr != addr) 1801 return (unsigned long) -EINVAL; 1802 1803 vma = find_vma_exact(current->mm, addr, old_len); 1804 if (!vma) 1805 return (unsigned long) -EINVAL; 1806 1807 if (vma->vm_end != vma->vm_start + old_len) 1808 return (unsigned long) -EFAULT; 1809 1810 if (vma->vm_flags & VM_MAYSHARE) 1811 return (unsigned long) -EPERM; 1812 1813 if (new_len > vma->vm_region->vm_end - vma->vm_region->vm_start) 1814 return (unsigned long) -ENOMEM; 1815 1816 /* all checks complete - do it */ 1817 vma->vm_end = vma->vm_start + new_len; 1818 return vma->vm_start; 1819 } 1820 1821 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, 1822 unsigned long, new_len, unsigned long, flags, 1823 unsigned long, new_addr) 1824 { 1825 unsigned long ret; 1826 1827 down_write(¤t->mm->mmap_sem); 1828 ret = do_mremap(addr, old_len, new_len, flags, new_addr); 1829 up_write(¤t->mm->mmap_sem); 1830 return ret; 1831 } 1832 1833 struct page *follow_page_mask(struct vm_area_struct *vma, 1834 unsigned long address, unsigned int flags, 1835 unsigned int *page_mask) 1836 { 1837 *page_mask = 0; 1838 return NULL; 1839 } 1840 1841 int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr, 1842 unsigned long pfn, unsigned long size, pgprot_t prot) 1843 { 1844 if (addr != (pfn << PAGE_SHIFT)) 1845 return -EINVAL; 1846 1847 vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP; 1848 return 0; 1849 } 1850 EXPORT_SYMBOL(remap_pfn_range); 1851 1852 int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len) 1853 { 1854 unsigned long pfn = start >> PAGE_SHIFT; 1855 unsigned long vm_len = vma->vm_end - vma->vm_start; 1856 1857 pfn += vma->vm_pgoff; 1858 return io_remap_pfn_range(vma, vma->vm_start, pfn, vm_len, vma->vm_page_prot); 1859 } 1860 EXPORT_SYMBOL(vm_iomap_memory); 1861 1862 int remap_vmalloc_range(struct vm_area_struct *vma, void *addr, 1863 unsigned long pgoff) 1864 { 1865 unsigned int size = vma->vm_end - vma->vm_start; 1866 1867 if (!(vma->vm_flags & VM_USERMAP)) 1868 return -EINVAL; 1869 1870 vma->vm_start = (unsigned long)(addr + (pgoff << PAGE_SHIFT)); 1871 vma->vm_end = vma->vm_start + size; 1872 1873 return 0; 1874 } 1875 EXPORT_SYMBOL(remap_vmalloc_range); 1876 1877 unsigned long arch_get_unmapped_area(struct file *file, unsigned long addr, 1878 unsigned long len, unsigned long pgoff, unsigned long flags) 1879 { 1880 return -ENOMEM; 1881 } 1882 1883 void unmap_mapping_range(struct address_space *mapping, 1884 loff_t const holebegin, loff_t const holelen, 1885 int even_cows) 1886 { 1887 } 1888 EXPORT_SYMBOL(unmap_mapping_range); 1889 1890 /* 1891 * Check that a process has enough memory to allocate a new virtual 1892 * mapping. 0 means there is enough memory for the allocation to 1893 * succeed and -ENOMEM implies there is not. 1894 * 1895 * We currently support three overcommit policies, which are set via the 1896 * vm.overcommit_memory sysctl. See Documentation/vm/overcommit-accounting 1897 * 1898 * Strict overcommit modes added 2002 Feb 26 by Alan Cox. 1899 * Additional code 2002 Jul 20 by Robert Love. 1900 * 1901 * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise. 1902 * 1903 * Note this is a helper function intended to be used by LSMs which 1904 * wish to use this logic. 1905 */ 1906 int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin) 1907 { 1908 unsigned long free, allowed, reserve; 1909 1910 vm_acct_memory(pages); 1911 1912 /* 1913 * Sometimes we want to use more memory than we have 1914 */ 1915 if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS) 1916 return 0; 1917 1918 if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) { 1919 free = global_page_state(NR_FREE_PAGES); 1920 free += global_page_state(NR_FILE_PAGES); 1921 1922 /* 1923 * shmem pages shouldn't be counted as free in this 1924 * case, they can't be purged, only swapped out, and 1925 * that won't affect the overall amount of available 1926 * memory in the system. 1927 */ 1928 free -= global_page_state(NR_SHMEM); 1929 1930 free += get_nr_swap_pages(); 1931 1932 /* 1933 * Any slabs which are created with the 1934 * SLAB_RECLAIM_ACCOUNT flag claim to have contents 1935 * which are reclaimable, under pressure. The dentry 1936 * cache and most inode caches should fall into this 1937 */ 1938 free += global_page_state(NR_SLAB_RECLAIMABLE); 1939 1940 /* 1941 * Leave reserved pages. The pages are not for anonymous pages. 1942 */ 1943 if (free <= totalreserve_pages) 1944 goto error; 1945 else 1946 free -= totalreserve_pages; 1947 1948 /* 1949 * Reserve some for root 1950 */ 1951 if (!cap_sys_admin) 1952 free -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10); 1953 1954 if (free > pages) 1955 return 0; 1956 1957 goto error; 1958 } 1959 1960 allowed = vm_commit_limit(); 1961 /* 1962 * Reserve some 3% for root 1963 */ 1964 if (!cap_sys_admin) 1965 allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10); 1966 1967 /* 1968 * Don't let a single process grow so big a user can't recover 1969 */ 1970 if (mm) { 1971 reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10); 1972 allowed -= min(mm->total_vm / 32, reserve); 1973 } 1974 1975 if (percpu_counter_read_positive(&vm_committed_as) < allowed) 1976 return 0; 1977 1978 error: 1979 vm_unacct_memory(pages); 1980 1981 return -ENOMEM; 1982 } 1983 1984 int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf) 1985 { 1986 BUG(); 1987 return 0; 1988 } 1989 EXPORT_SYMBOL(filemap_fault); 1990 1991 void filemap_map_pages(struct vm_area_struct *vma, struct vm_fault *vmf) 1992 { 1993 BUG(); 1994 } 1995 EXPORT_SYMBOL(filemap_map_pages); 1996 1997 int generic_file_remap_pages(struct vm_area_struct *vma, unsigned long addr, 1998 unsigned long size, pgoff_t pgoff) 1999 { 2000 BUG(); 2001 return 0; 2002 } 2003 EXPORT_SYMBOL(generic_file_remap_pages); 2004 2005 static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm, 2006 unsigned long addr, void *buf, int len, int write) 2007 { 2008 struct vm_area_struct *vma; 2009 2010 down_read(&mm->mmap_sem); 2011 2012 /* the access must start within one of the target process's mappings */ 2013 vma = find_vma(mm, addr); 2014 if (vma) { 2015 /* don't overrun this mapping */ 2016 if (addr + len >= vma->vm_end) 2017 len = vma->vm_end - addr; 2018 2019 /* only read or write mappings where it is permitted */ 2020 if (write && vma->vm_flags & VM_MAYWRITE) 2021 copy_to_user_page(vma, NULL, addr, 2022 (void *) addr, buf, len); 2023 else if (!write && vma->vm_flags & VM_MAYREAD) 2024 copy_from_user_page(vma, NULL, addr, 2025 buf, (void *) addr, len); 2026 else 2027 len = 0; 2028 } else { 2029 len = 0; 2030 } 2031 2032 up_read(&mm->mmap_sem); 2033 2034 return len; 2035 } 2036 2037 /** 2038 * @access_remote_vm - access another process' address space 2039 * @mm: the mm_struct of the target address space 2040 * @addr: start address to access 2041 * @buf: source or destination buffer 2042 * @len: number of bytes to transfer 2043 * @write: whether the access is a write 2044 * 2045 * The caller must hold a reference on @mm. 2046 */ 2047 int access_remote_vm(struct mm_struct *mm, unsigned long addr, 2048 void *buf, int len, int write) 2049 { 2050 return __access_remote_vm(NULL, mm, addr, buf, len, write); 2051 } 2052 2053 /* 2054 * Access another process' address space. 2055 * - source/target buffer must be kernel space 2056 */ 2057 int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write) 2058 { 2059 struct mm_struct *mm; 2060 2061 if (addr + len < addr) 2062 return 0; 2063 2064 mm = get_task_mm(tsk); 2065 if (!mm) 2066 return 0; 2067 2068 len = __access_remote_vm(tsk, mm, addr, buf, len, write); 2069 2070 mmput(mm); 2071 return len; 2072 } 2073 2074 /** 2075 * nommu_shrink_inode_mappings - Shrink the shared mappings on an inode 2076 * @inode: The inode to check 2077 * @size: The current filesize of the inode 2078 * @newsize: The proposed filesize of the inode 2079 * 2080 * Check the shared mappings on an inode on behalf of a shrinking truncate to 2081 * make sure that that any outstanding VMAs aren't broken and then shrink the 2082 * vm_regions that extend that beyond so that do_mmap_pgoff() doesn't 2083 * automatically grant mappings that are too large. 2084 */ 2085 int nommu_shrink_inode_mappings(struct inode *inode, size_t size, 2086 size_t newsize) 2087 { 2088 struct vm_area_struct *vma; 2089 struct vm_region *region; 2090 pgoff_t low, high; 2091 size_t r_size, r_top; 2092 2093 low = newsize >> PAGE_SHIFT; 2094 high = (size + PAGE_SIZE - 1) >> PAGE_SHIFT; 2095 2096 down_write(&nommu_region_sem); 2097 mutex_lock(&inode->i_mapping->i_mmap_mutex); 2098 2099 /* search for VMAs that fall within the dead zone */ 2100 vma_interval_tree_foreach(vma, &inode->i_mapping->i_mmap, low, high) { 2101 /* found one - only interested if it's shared out of the page 2102 * cache */ 2103 if (vma->vm_flags & VM_SHARED) { 2104 mutex_unlock(&inode->i_mapping->i_mmap_mutex); 2105 up_write(&nommu_region_sem); 2106 return -ETXTBSY; /* not quite true, but near enough */ 2107 } 2108 } 2109 2110 /* reduce any regions that overlap the dead zone - if in existence, 2111 * these will be pointed to by VMAs that don't overlap the dead zone 2112 * 2113 * we don't check for any regions that start beyond the EOF as there 2114 * shouldn't be any 2115 */ 2116 vma_interval_tree_foreach(vma, &inode->i_mapping->i_mmap, 2117 0, ULONG_MAX) { 2118 if (!(vma->vm_flags & VM_SHARED)) 2119 continue; 2120 2121 region = vma->vm_region; 2122 r_size = region->vm_top - region->vm_start; 2123 r_top = (region->vm_pgoff << PAGE_SHIFT) + r_size; 2124 2125 if (r_top > newsize) { 2126 region->vm_top -= r_top - newsize; 2127 if (region->vm_end > region->vm_top) 2128 region->vm_end = region->vm_top; 2129 } 2130 } 2131 2132 mutex_unlock(&inode->i_mapping->i_mmap_mutex); 2133 up_write(&nommu_region_sem); 2134 return 0; 2135 } 2136 2137 /* 2138 * Initialise sysctl_user_reserve_kbytes. 2139 * 2140 * This is intended to prevent a user from starting a single memory hogging 2141 * process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER 2142 * mode. 2143 * 2144 * The default value is min(3% of free memory, 128MB) 2145 * 128MB is enough to recover with sshd/login, bash, and top/kill. 2146 */ 2147 static int __meminit init_user_reserve(void) 2148 { 2149 unsigned long free_kbytes; 2150 2151 free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10); 2152 2153 sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17); 2154 return 0; 2155 } 2156 module_init(init_user_reserve) 2157 2158 /* 2159 * Initialise sysctl_admin_reserve_kbytes. 2160 * 2161 * The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin 2162 * to log in and kill a memory hogging process. 2163 * 2164 * Systems with more than 256MB will reserve 8MB, enough to recover 2165 * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will 2166 * only reserve 3% of free pages by default. 2167 */ 2168 static int __meminit init_admin_reserve(void) 2169 { 2170 unsigned long free_kbytes; 2171 2172 free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10); 2173 2174 sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13); 2175 return 0; 2176 } 2177 module_init(init_admin_reserve) 2178