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/mman.h>
  23#include <linux/swap.h>
  24#include <linux/file.h>
  25#include <linux/highmem.h>
  26#include <linux/pagemap.h>
  27#include <linux/slab.h>
  28#include <linux/vmalloc.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/printk.h>
  37
  38#include <linux/uaccess.h>
  39#include <linux/uio.h>
  40#include <asm/tlb.h>
  41#include <asm/tlbflush.h>
  42#include <asm/mmu_context.h>
  43#include "internal.h"
  44
  45void *high_memory;
  46EXPORT_SYMBOL(high_memory);
  47struct page *mem_map;
  48unsigned long max_mapnr;
  49EXPORT_SYMBOL(max_mapnr);
  50unsigned long highest_memmap_pfn;
  51int sysctl_nr_trim_pages = CONFIG_NOMMU_INITIAL_TRIM_EXCESS;
  52int heap_stack_gap = 0;
  53
  54atomic_long_t mmap_pages_allocated;
  55
  56EXPORT_SYMBOL(mem_map);
  57
  58/* list of mapped, potentially shareable regions */
  59static struct kmem_cache *vm_region_jar;
  60struct rb_root nommu_region_tree = RB_ROOT;
  61DECLARE_RWSEM(nommu_region_sem);
  62
  63const 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 */
  72unsigned 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 */
 123int 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}
 132EXPORT_SYMBOL(follow_pfn);
 133
 134LIST_HEAD(vmap_area_list);
 135
 136void vfree(const void *addr)
 137{
 138	kfree(addr);
 139}
 140EXPORT_SYMBOL(vfree);
 141
 142void *__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}
 150EXPORT_SYMBOL(__vmalloc);
 151
 152void *__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
 160void *__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
 166static 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			vm_flags_set(vma, VM_USERMAP);
 178		mmap_write_unlock(current->mm);
 179	}
 180
 181	return ret;
 182}
 183
 184void *vmalloc_user(unsigned long size)
 185{
 186	return __vmalloc_user_flags(size, GFP_KERNEL | __GFP_ZERO);
 187}
 188EXPORT_SYMBOL(vmalloc_user);
 189
 190struct page *vmalloc_to_page(const void *addr)
 191{
 192	return virt_to_page(addr);
 193}
 194EXPORT_SYMBOL(vmalloc_to_page);
 195
 196unsigned long vmalloc_to_pfn(const void *addr)
 197{
 198	return page_to_pfn(virt_to_page(addr));
 199}
 200EXPORT_SYMBOL(vmalloc_to_pfn);
 201
 202long vread_iter(struct iov_iter *iter, const char *addr, size_t count)
 203{
 204	/* Don't allow overflow */
 205	if ((unsigned long) addr + count < count)
 206		count = -(unsigned long) addr;
 207
 208	return copy_to_iter(addr, count, iter);
 
 209}
 210
 211/*
 212 *	vmalloc  -  allocate virtually contiguous memory
 213 *
 214 *	@size:		allocation size
 215 *
 216 *	Allocate enough pages to cover @size from the page level
 217 *	allocator and map them into contiguous kernel virtual space.
 218 *
 219 *	For tight control over page level allocator and protection flags
 220 *	use __vmalloc() instead.
 221 */
 222void *vmalloc(unsigned long size)
 223{
 224	return __vmalloc(size, GFP_KERNEL);
 225}
 226EXPORT_SYMBOL(vmalloc);
 227
 228void *vmalloc_huge(unsigned long size, gfp_t gfp_mask) __weak __alias(__vmalloc);
 229
 230/*
 231 *	vzalloc - allocate virtually contiguous memory with zero fill
 232 *
 233 *	@size:		allocation size
 234 *
 235 *	Allocate enough pages to cover @size from the page level
 236 *	allocator and map them into contiguous kernel virtual space.
 237 *	The memory allocated is set to zero.
 238 *
 239 *	For tight control over page level allocator and protection flags
 240 *	use __vmalloc() instead.
 241 */
 242void *vzalloc(unsigned long size)
 243{
 244	return __vmalloc(size, GFP_KERNEL | __GFP_ZERO);
 245}
 246EXPORT_SYMBOL(vzalloc);
 247
 248/**
 249 * vmalloc_node - allocate memory on a specific node
 250 * @size:	allocation size
 251 * @node:	numa node
 252 *
 253 * Allocate enough pages to cover @size from the page level
 254 * allocator and map them into contiguous kernel virtual space.
 255 *
 256 * For tight control over page level allocator and protection flags
 257 * use __vmalloc() instead.
 258 */
 259void *vmalloc_node(unsigned long size, int node)
 260{
 261	return vmalloc(size);
 262}
 263EXPORT_SYMBOL(vmalloc_node);
 264
 265/**
 266 * vzalloc_node - allocate memory on a specific node with zero fill
 267 * @size:	allocation size
 268 * @node:	numa node
 269 *
 270 * Allocate enough pages to cover @size from the page level
 271 * allocator and map them into contiguous kernel virtual space.
 272 * The memory allocated is set to zero.
 273 *
 274 * For tight control over page level allocator and protection flags
 275 * use __vmalloc() instead.
 276 */
 277void *vzalloc_node(unsigned long size, int node)
 278{
 279	return vzalloc(size);
 280}
 281EXPORT_SYMBOL(vzalloc_node);
 282
 283/**
 284 * vmalloc_32  -  allocate virtually contiguous memory (32bit addressable)
 285 *	@size:		allocation size
 286 *
 287 *	Allocate enough 32bit PA addressable pages to cover @size from the
 288 *	page level allocator and map them into contiguous kernel virtual space.
 289 */
 290void *vmalloc_32(unsigned long size)
 291{
 292	return __vmalloc(size, GFP_KERNEL);
 293}
 294EXPORT_SYMBOL(vmalloc_32);
 295
 296/**
 297 * vmalloc_32_user - allocate zeroed virtually contiguous 32bit memory
 298 *	@size:		allocation size
 299 *
 300 * The resulting memory area is 32bit addressable and zeroed so it can be
 301 * mapped to userspace without leaking data.
 302 *
 303 * VM_USERMAP is set on the corresponding VMA so that subsequent calls to
 304 * remap_vmalloc_range() are permissible.
 305 */
 306void *vmalloc_32_user(unsigned long size)
 307{
 308	/*
 309	 * We'll have to sort out the ZONE_DMA bits for 64-bit,
 310	 * but for now this can simply use vmalloc_user() directly.
 311	 */
 312	return vmalloc_user(size);
 313}
 314EXPORT_SYMBOL(vmalloc_32_user);
 315
 316void *vmap(struct page **pages, unsigned int count, unsigned long flags, pgprot_t prot)
 317{
 318	BUG();
 319	return NULL;
 320}
 321EXPORT_SYMBOL(vmap);
 322
 323void vunmap(const void *addr)
 324{
 325	BUG();
 326}
 327EXPORT_SYMBOL(vunmap);
 328
 329void *vm_map_ram(struct page **pages, unsigned int count, int node)
 330{
 331	BUG();
 332	return NULL;
 333}
 334EXPORT_SYMBOL(vm_map_ram);
 335
 336void vm_unmap_ram(const void *mem, unsigned int count)
 337{
 338	BUG();
 339}
 340EXPORT_SYMBOL(vm_unmap_ram);
 341
 342void vm_unmap_aliases(void)
 343{
 344}
 345EXPORT_SYMBOL_GPL(vm_unmap_aliases);
 346
 347void free_vm_area(struct vm_struct *area)
 348{
 349	BUG();
 350}
 351EXPORT_SYMBOL_GPL(free_vm_area);
 352
 353int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
 354		   struct page *page)
 355{
 356	return -EINVAL;
 357}
 358EXPORT_SYMBOL(vm_insert_page);
 359
 360int vm_map_pages(struct vm_area_struct *vma, struct page **pages,
 361			unsigned long num)
 362{
 363	return -EINVAL;
 364}
 365EXPORT_SYMBOL(vm_map_pages);
 366
 367int vm_map_pages_zero(struct vm_area_struct *vma, struct page **pages,
 368				unsigned long num)
 369{
 370	return -EINVAL;
 371}
 372EXPORT_SYMBOL(vm_map_pages_zero);
 373
 374/*
 375 *  sys_brk() for the most part doesn't need the global kernel
 376 *  lock, except when an application is doing something nasty
 377 *  like trying to un-brk an area that has already been mapped
 378 *  to a regular file.  in this case, the unmapping will need
 379 *  to invoke file system routines that need the global lock.
 380 */
 381SYSCALL_DEFINE1(brk, unsigned long, brk)
 382{
 383	struct mm_struct *mm = current->mm;
 384
 385	if (brk < mm->start_brk || brk > mm->context.end_brk)
 386		return mm->brk;
 387
 388	if (mm->brk == brk)
 389		return mm->brk;
 390
 391	/*
 392	 * Always allow shrinking brk
 393	 */
 394	if (brk <= mm->brk) {
 395		mm->brk = brk;
 396		return brk;
 397	}
 398
 399	/*
 400	 * Ok, looks good - let it rip.
 401	 */
 402	flush_icache_user_range(mm->brk, brk);
 403	return mm->brk = brk;
 404}
 405
 406/*
 407 * initialise the percpu counter for VM and region record slabs
 408 */
 409void __init mmap_init(void)
 410{
 411	int ret;
 412
 413	ret = percpu_counter_init(&vm_committed_as, 0, GFP_KERNEL);
 414	VM_BUG_ON(ret);
 415	vm_region_jar = KMEM_CACHE(vm_region, SLAB_PANIC|SLAB_ACCOUNT);
 416}
 417
 418/*
 419 * validate the region tree
 420 * - the caller must hold the region lock
 421 */
 422#ifdef CONFIG_DEBUG_NOMMU_REGIONS
 423static noinline void validate_nommu_regions(void)
 424{
 425	struct vm_region *region, *last;
 426	struct rb_node *p, *lastp;
 427
 428	lastp = rb_first(&nommu_region_tree);
 429	if (!lastp)
 430		return;
 431
 432	last = rb_entry(lastp, struct vm_region, vm_rb);
 433	BUG_ON(last->vm_end <= last->vm_start);
 434	BUG_ON(last->vm_top < last->vm_end);
 435
 436	while ((p = rb_next(lastp))) {
 437		region = rb_entry(p, struct vm_region, vm_rb);
 438		last = rb_entry(lastp, struct vm_region, vm_rb);
 439
 440		BUG_ON(region->vm_end <= region->vm_start);
 441		BUG_ON(region->vm_top < region->vm_end);
 442		BUG_ON(region->vm_start < last->vm_top);
 443
 444		lastp = p;
 445	}
 446}
 447#else
 448static void validate_nommu_regions(void)
 449{
 450}
 451#endif
 452
 453/*
 454 * add a region into the global tree
 455 */
 456static void add_nommu_region(struct vm_region *region)
 457{
 458	struct vm_region *pregion;
 459	struct rb_node **p, *parent;
 460
 461	validate_nommu_regions();
 462
 463	parent = NULL;
 464	p = &nommu_region_tree.rb_node;
 465	while (*p) {
 466		parent = *p;
 467		pregion = rb_entry(parent, struct vm_region, vm_rb);
 468		if (region->vm_start < pregion->vm_start)
 469			p = &(*p)->rb_left;
 470		else if (region->vm_start > pregion->vm_start)
 471			p = &(*p)->rb_right;
 472		else if (pregion == region)
 473			return;
 474		else
 475			BUG();
 476	}
 477
 478	rb_link_node(&region->vm_rb, parent, p);
 479	rb_insert_color(&region->vm_rb, &nommu_region_tree);
 480
 481	validate_nommu_regions();
 482}
 483
 484/*
 485 * delete a region from the global tree
 486 */
 487static void delete_nommu_region(struct vm_region *region)
 488{
 489	BUG_ON(!nommu_region_tree.rb_node);
 490
 491	validate_nommu_regions();
 492	rb_erase(&region->vm_rb, &nommu_region_tree);
 493	validate_nommu_regions();
 494}
 495
 496/*
 497 * free a contiguous series of pages
 498 */
 499static void free_page_series(unsigned long from, unsigned long to)
 500{
 501	for (; from < to; from += PAGE_SIZE) {
 502		struct page *page = virt_to_page((void *)from);
 503
 504		atomic_long_dec(&mmap_pages_allocated);
 505		put_page(page);
 506	}
 507}
 508
 509/*
 510 * release a reference to a region
 511 * - the caller must hold the region semaphore for writing, which this releases
 512 * - the region may not have been added to the tree yet, in which case vm_top
 513 *   will equal vm_start
 514 */
 515static void __put_nommu_region(struct vm_region *region)
 516	__releases(nommu_region_sem)
 517{
 518	BUG_ON(!nommu_region_tree.rb_node);
 519
 520	if (--region->vm_usage == 0) {
 521		if (region->vm_top > region->vm_start)
 522			delete_nommu_region(region);
 523		up_write(&nommu_region_sem);
 524
 525		if (region->vm_file)
 526			fput(region->vm_file);
 527
 528		/* IO memory and memory shared directly out of the pagecache
 529		 * from ramfs/tmpfs mustn't be released here */
 530		if (region->vm_flags & VM_MAPPED_COPY)
 531			free_page_series(region->vm_start, region->vm_top);
 532		kmem_cache_free(vm_region_jar, region);
 533	} else {
 534		up_write(&nommu_region_sem);
 535	}
 536}
 537
 538/*
 539 * release a reference to a region
 540 */
 541static void put_nommu_region(struct vm_region *region)
 542{
 543	down_write(&nommu_region_sem);
 544	__put_nommu_region(region);
 545}
 546
 
 
 
 
 
 
 
 
 
 
 
 
 
 547static void setup_vma_to_mm(struct vm_area_struct *vma, struct mm_struct *mm)
 548{
 549	vma->vm_mm = mm;
 550
 551	/* add the VMA to the mapping */
 552	if (vma->vm_file) {
 553		struct address_space *mapping = vma->vm_file->f_mapping;
 554
 555		i_mmap_lock_write(mapping);
 556		flush_dcache_mmap_lock(mapping);
 557		vma_interval_tree_insert(vma, &mapping->i_mmap);
 558		flush_dcache_mmap_unlock(mapping);
 559		i_mmap_unlock_write(mapping);
 560	}
 561}
 562
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 563static void cleanup_vma_from_mm(struct vm_area_struct *vma)
 564{
 565	vma->vm_mm->map_count--;
 566	/* remove the VMA from the mapping */
 567	if (vma->vm_file) {
 568		struct address_space *mapping;
 569		mapping = vma->vm_file->f_mapping;
 570
 571		i_mmap_lock_write(mapping);
 572		flush_dcache_mmap_lock(mapping);
 573		vma_interval_tree_remove(vma, &mapping->i_mmap);
 574		flush_dcache_mmap_unlock(mapping);
 575		i_mmap_unlock_write(mapping);
 576	}
 577}
 578
 579/*
 580 * delete a VMA from its owning mm_struct and address space
 581 */
 582static int delete_vma_from_mm(struct vm_area_struct *vma)
 583{
 584	VMA_ITERATOR(vmi, vma->vm_mm, vma->vm_start);
 585
 586	vma_iter_config(&vmi, vma->vm_start, vma->vm_end);
 587	if (vma_iter_prealloc(&vmi, vma)) {
 588		pr_warn("Allocation of vma tree for process %d failed\n",
 589		       current->pid);
 590		return -ENOMEM;
 591	}
 592	cleanup_vma_from_mm(vma);
 593
 594	/* remove from the MM's tree and list */
 595	vma_iter_clear(&vmi);
 596	return 0;
 597}
 
 598/*
 599 * destroy a VMA record
 600 */
 601static void delete_vma(struct mm_struct *mm, struct vm_area_struct *vma)
 602{
 603	if (vma->vm_ops && vma->vm_ops->close)
 604		vma->vm_ops->close(vma);
 605	if (vma->vm_file)
 606		fput(vma->vm_file);
 607	put_nommu_region(vma->vm_region);
 608	vm_area_free(vma);
 609}
 610
 611struct vm_area_struct *find_vma_intersection(struct mm_struct *mm,
 612					     unsigned long start_addr,
 613					     unsigned long end_addr)
 614{
 615	unsigned long index = start_addr;
 616
 617	mmap_assert_locked(mm);
 618	return mt_find(&mm->mm_mt, &index, end_addr - 1);
 619}
 620EXPORT_SYMBOL(find_vma_intersection);
 621
 622/*
 623 * look up the first VMA in which addr resides, NULL if none
 624 * - should be called with mm->mmap_lock at least held readlocked
 625 */
 626struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
 627{
 628	VMA_ITERATOR(vmi, mm, addr);
 629
 630	return vma_iter_load(&vmi);
 631}
 632EXPORT_SYMBOL(find_vma);
 633
 634/*
 635 * At least xtensa ends up having protection faults even with no
 636 * MMU.. No stack expansion, at least.
 637 */
 638struct vm_area_struct *lock_mm_and_find_vma(struct mm_struct *mm,
 639			unsigned long addr, struct pt_regs *regs)
 640{
 641	struct vm_area_struct *vma;
 642
 643	mmap_read_lock(mm);
 644	vma = vma_lookup(mm, addr);
 645	if (!vma)
 646		mmap_read_unlock(mm);
 647	return vma;
 648}
 649
 650/*
 651 * expand a stack to a given address
 652 * - not supported under NOMMU conditions
 653 */
 654int expand_stack_locked(struct vm_area_struct *vma, unsigned long addr)
 655{
 656	return -ENOMEM;
 657}
 658
 659struct vm_area_struct *expand_stack(struct mm_struct *mm, unsigned long addr)
 660{
 661	mmap_read_unlock(mm);
 662	return NULL;
 663}
 664
 665/*
 666 * look up the first VMA exactly that exactly matches addr
 667 * - should be called with mm->mmap_lock at least held readlocked
 668 */
 669static struct vm_area_struct *find_vma_exact(struct mm_struct *mm,
 670					     unsigned long addr,
 671					     unsigned long len)
 672{
 673	struct vm_area_struct *vma;
 674	unsigned long end = addr + len;
 675	VMA_ITERATOR(vmi, mm, addr);
 676
 677	vma = vma_iter_load(&vmi);
 678	if (!vma)
 679		return NULL;
 680	if (vma->vm_start != addr)
 681		return NULL;
 682	if (vma->vm_end != end)
 683		return NULL;
 684
 685	return vma;
 686}
 687
 688/*
 689 * determine whether a mapping should be permitted and, if so, what sort of
 690 * mapping we're capable of supporting
 691 */
 692static int validate_mmap_request(struct file *file,
 693				 unsigned long addr,
 694				 unsigned long len,
 695				 unsigned long prot,
 696				 unsigned long flags,
 697				 unsigned long pgoff,
 698				 unsigned long *_capabilities)
 699{
 700	unsigned long capabilities, rlen;
 701	int ret;
 702
 703	/* do the simple checks first */
 704	if (flags & MAP_FIXED)
 705		return -EINVAL;
 706
 707	if ((flags & MAP_TYPE) != MAP_PRIVATE &&
 708	    (flags & MAP_TYPE) != MAP_SHARED)
 709		return -EINVAL;
 710
 711	if (!len)
 712		return -EINVAL;
 713
 714	/* Careful about overflows.. */
 715	rlen = PAGE_ALIGN(len);
 716	if (!rlen || rlen > TASK_SIZE)
 717		return -ENOMEM;
 718
 719	/* offset overflow? */
 720	if ((pgoff + (rlen >> PAGE_SHIFT)) < pgoff)
 721		return -EOVERFLOW;
 722
 723	if (file) {
 724		/* files must support mmap */
 725		if (!file->f_op->mmap)
 726			return -ENODEV;
 727
 728		/* work out if what we've got could possibly be shared
 729		 * - we support chardevs that provide their own "memory"
 730		 * - we support files/blockdevs that are memory backed
 731		 */
 732		if (file->f_op->mmap_capabilities) {
 733			capabilities = file->f_op->mmap_capabilities(file);
 734		} else {
 735			/* no explicit capabilities set, so assume some
 736			 * defaults */
 737			switch (file_inode(file)->i_mode & S_IFMT) {
 738			case S_IFREG:
 739			case S_IFBLK:
 740				capabilities = NOMMU_MAP_COPY;
 741				break;
 742
 743			case S_IFCHR:
 744				capabilities =
 745					NOMMU_MAP_DIRECT |
 746					NOMMU_MAP_READ |
 747					NOMMU_MAP_WRITE;
 748				break;
 749
 750			default:
 751				return -EINVAL;
 752			}
 753		}
 754
 755		/* eliminate any capabilities that we can't support on this
 756		 * device */
 757		if (!file->f_op->get_unmapped_area)
 758			capabilities &= ~NOMMU_MAP_DIRECT;
 759		if (!(file->f_mode & FMODE_CAN_READ))
 760			capabilities &= ~NOMMU_MAP_COPY;
 761
 762		/* The file shall have been opened with read permission. */
 763		if (!(file->f_mode & FMODE_READ))
 764			return -EACCES;
 765
 766		if (flags & MAP_SHARED) {
 767			/* do checks for writing, appending and locking */
 768			if ((prot & PROT_WRITE) &&
 769			    !(file->f_mode & FMODE_WRITE))
 770				return -EACCES;
 771
 772			if (IS_APPEND(file_inode(file)) &&
 773			    (file->f_mode & FMODE_WRITE))
 774				return -EACCES;
 775
 776			if (!(capabilities & NOMMU_MAP_DIRECT))
 777				return -ENODEV;
 778
 779			/* we mustn't privatise shared mappings */
 780			capabilities &= ~NOMMU_MAP_COPY;
 781		} else {
 782			/* we're going to read the file into private memory we
 783			 * allocate */
 784			if (!(capabilities & NOMMU_MAP_COPY))
 785				return -ENODEV;
 786
 787			/* we don't permit a private writable mapping to be
 788			 * shared with the backing device */
 789			if (prot & PROT_WRITE)
 790				capabilities &= ~NOMMU_MAP_DIRECT;
 791		}
 792
 793		if (capabilities & NOMMU_MAP_DIRECT) {
 794			if (((prot & PROT_READ)  && !(capabilities & NOMMU_MAP_READ))  ||
 795			    ((prot & PROT_WRITE) && !(capabilities & NOMMU_MAP_WRITE)) ||
 796			    ((prot & PROT_EXEC)  && !(capabilities & NOMMU_MAP_EXEC))
 797			    ) {
 798				capabilities &= ~NOMMU_MAP_DIRECT;
 799				if (flags & MAP_SHARED) {
 800					pr_warn("MAP_SHARED not completely supported on !MMU\n");
 801					return -EINVAL;
 802				}
 803			}
 804		}
 805
 806		/* handle executable mappings and implied executable
 807		 * mappings */
 808		if (path_noexec(&file->f_path)) {
 809			if (prot & PROT_EXEC)
 810				return -EPERM;
 811		} else if ((prot & PROT_READ) && !(prot & PROT_EXEC)) {
 812			/* handle implication of PROT_EXEC by PROT_READ */
 813			if (current->personality & READ_IMPLIES_EXEC) {
 814				if (capabilities & NOMMU_MAP_EXEC)
 815					prot |= PROT_EXEC;
 816			}
 817		} else if ((prot & PROT_READ) &&
 818			 (prot & PROT_EXEC) &&
 819			 !(capabilities & NOMMU_MAP_EXEC)
 820			 ) {
 821			/* backing file is not executable, try to copy */
 822			capabilities &= ~NOMMU_MAP_DIRECT;
 823		}
 824	} else {
 825		/* anonymous mappings are always memory backed and can be
 826		 * privately mapped
 827		 */
 828		capabilities = NOMMU_MAP_COPY;
 829
 830		/* handle PROT_EXEC implication by PROT_READ */
 831		if ((prot & PROT_READ) &&
 832		    (current->personality & READ_IMPLIES_EXEC))
 833			prot |= PROT_EXEC;
 834	}
 835
 836	/* allow the security API to have its say */
 837	ret = security_mmap_addr(addr);
 838	if (ret < 0)
 839		return ret;
 840
 841	/* looks okay */
 842	*_capabilities = capabilities;
 843	return 0;
 844}
 845
 846/*
 847 * we've determined that we can make the mapping, now translate what we
 848 * now know into VMA flags
 849 */
 850static unsigned long determine_vm_flags(struct file *file,
 851					unsigned long prot,
 852					unsigned long flags,
 853					unsigned long capabilities)
 854{
 855	unsigned long vm_flags;
 856
 857	vm_flags = calc_vm_prot_bits(prot, 0) | calc_vm_flag_bits(flags);
 
 858
 859	if (!file) {
 860		/*
 861		 * MAP_ANONYMOUS. MAP_SHARED is mapped to MAP_PRIVATE, because
 862		 * there is no fork().
 863		 */
 864		vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
 865	} else if (flags & MAP_PRIVATE) {
 866		/* MAP_PRIVATE file mapping */
 867		if (capabilities & NOMMU_MAP_DIRECT)
 868			vm_flags |= (capabilities & NOMMU_VMFLAGS);
 869		else
 870			vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
 871
 872		if (!(prot & PROT_WRITE) && !current->ptrace)
 873			/*
 874			 * R/O private file mapping which cannot be used to
 875			 * modify memory, especially also not via active ptrace
 876			 * (e.g., set breakpoints) or later by upgrading
 877			 * permissions (no mprotect()). We can try overlaying
 878			 * the file mapping, which will work e.g., on chardevs,
 879			 * ramfs/tmpfs/shmfs and romfs/cramf.
 880			 */
 881			vm_flags |= VM_MAYOVERLAY;
 882	} else {
 883		/* MAP_SHARED file mapping: NOMMU_MAP_DIRECT is set. */
 884		vm_flags |= VM_SHARED | VM_MAYSHARE |
 885			    (capabilities & NOMMU_VMFLAGS);
 
 
 
 886	}
 887
 
 
 
 
 
 
 
 888	return vm_flags;
 889}
 890
 891/*
 892 * set up a shared mapping on a file (the driver or filesystem provides and
 893 * pins the storage)
 894 */
 895static int do_mmap_shared_file(struct vm_area_struct *vma)
 896{
 897	int ret;
 898
 899	ret = call_mmap(vma->vm_file, vma);
 900	if (ret == 0) {
 901		vma->vm_region->vm_top = vma->vm_region->vm_end;
 902		return 0;
 903	}
 904	if (ret != -ENOSYS)
 905		return ret;
 906
 907	/* getting -ENOSYS indicates that direct mmap isn't possible (as
 908	 * opposed to tried but failed) so we can only give a suitable error as
 909	 * it's not possible to make a private copy if MAP_SHARED was given */
 910	return -ENODEV;
 911}
 912
 913/*
 914 * set up a private mapping or an anonymous shared mapping
 915 */
 916static int do_mmap_private(struct vm_area_struct *vma,
 917			   struct vm_region *region,
 918			   unsigned long len,
 919			   unsigned long capabilities)
 920{
 921	unsigned long total, point;
 922	void *base;
 923	int ret, order;
 924
 925	/*
 926	 * Invoke the file's mapping function so that it can keep track of
 927	 * shared mappings on devices or memory. VM_MAYOVERLAY will be set if
 928	 * it may attempt to share, which will make is_nommu_shared_mapping()
 929	 * happy.
 930	 */
 931	if (capabilities & NOMMU_MAP_DIRECT) {
 932		ret = call_mmap(vma->vm_file, vma);
 933		/* shouldn't return success if we're not sharing */
 934		if (WARN_ON_ONCE(!is_nommu_shared_mapping(vma->vm_flags)))
 935			ret = -ENOSYS;
 936		if (ret == 0) {
 
 
 937			vma->vm_region->vm_top = vma->vm_region->vm_end;
 938			return 0;
 939		}
 940		if (ret != -ENOSYS)
 941			return ret;
 942
 943		/* getting an ENOSYS error indicates that direct mmap isn't
 944		 * possible (as opposed to tried but failed) so we'll try to
 945		 * make a private copy of the data and map that instead */
 946	}
 947
 948
 949	/* allocate some memory to hold the mapping
 950	 * - note that this may not return a page-aligned address if the object
 951	 *   we're allocating is smaller than a page
 952	 */
 953	order = get_order(len);
 954	total = 1 << order;
 955	point = len >> PAGE_SHIFT;
 956
 957	/* we don't want to allocate a power-of-2 sized page set */
 958	if (sysctl_nr_trim_pages && total - point >= sysctl_nr_trim_pages)
 959		total = point;
 960
 961	base = alloc_pages_exact(total << PAGE_SHIFT, GFP_KERNEL);
 962	if (!base)
 963		goto enomem;
 964
 965	atomic_long_add(total, &mmap_pages_allocated);
 966
 967	vm_flags_set(vma, VM_MAPPED_COPY);
 968	region->vm_flags = vma->vm_flags;
 969	region->vm_start = (unsigned long) base;
 970	region->vm_end   = region->vm_start + len;
 971	region->vm_top   = region->vm_start + (total << PAGE_SHIFT);
 972
 973	vma->vm_start = region->vm_start;
 974	vma->vm_end   = region->vm_start + len;
 975
 976	if (vma->vm_file) {
 977		/* read the contents of a file into the copy */
 978		loff_t fpos;
 979
 980		fpos = vma->vm_pgoff;
 981		fpos <<= PAGE_SHIFT;
 982
 983		ret = kernel_read(vma->vm_file, base, len, &fpos);
 984		if (ret < 0)
 985			goto error_free;
 986
 987		/* clear the last little bit */
 988		if (ret < len)
 989			memset(base + ret, 0, len - ret);
 990
 991	} else {
 992		vma_set_anonymous(vma);
 993	}
 994
 995	return 0;
 996
 997error_free:
 998	free_page_series(region->vm_start, region->vm_top);
 999	region->vm_start = vma->vm_start = 0;
1000	region->vm_end   = vma->vm_end = 0;
1001	region->vm_top   = 0;
1002	return ret;
1003
1004enomem:
1005	pr_err("Allocation of length %lu from process %d (%s) failed\n",
1006	       len, current->pid, current->comm);
1007	show_mem();
1008	return -ENOMEM;
1009}
1010
1011/*
1012 * handle mapping creation for uClinux
1013 */
1014unsigned long do_mmap(struct file *file,
1015			unsigned long addr,
1016			unsigned long len,
1017			unsigned long prot,
1018			unsigned long flags,
1019			vm_flags_t vm_flags,
1020			unsigned long pgoff,
1021			unsigned long *populate,
1022			struct list_head *uf)
1023{
1024	struct vm_area_struct *vma;
1025	struct vm_region *region;
1026	struct rb_node *rb;
 
1027	unsigned long capabilities, result;
1028	int ret;
1029	VMA_ITERATOR(vmi, current->mm, 0);
1030
1031	*populate = 0;
1032
1033	/* decide whether we should attempt the mapping, and if so what sort of
1034	 * mapping */
1035	ret = validate_mmap_request(file, addr, len, prot, flags, pgoff,
1036				    &capabilities);
1037	if (ret < 0)
1038		return ret;
1039
1040	/* we ignore the address hint */
1041	addr = 0;
1042	len = PAGE_ALIGN(len);
1043
1044	/* we've determined that we can make the mapping, now translate what we
1045	 * now know into VMA flags */
1046	vm_flags |= determine_vm_flags(file, prot, flags, capabilities);
1047
1048
1049	/* we're going to need to record the mapping */
1050	region = kmem_cache_zalloc(vm_region_jar, GFP_KERNEL);
1051	if (!region)
1052		goto error_getting_region;
1053
1054	vma = vm_area_alloc(current->mm);
1055	if (!vma)
1056		goto error_getting_vma;
1057
 
 
 
1058	region->vm_usage = 1;
1059	region->vm_flags = vm_flags;
1060	region->vm_pgoff = pgoff;
1061
1062	vm_flags_init(vma, vm_flags);
1063	vma->vm_pgoff = pgoff;
1064
1065	if (file) {
1066		region->vm_file = get_file(file);
1067		vma->vm_file = get_file(file);
1068	}
1069
1070	down_write(&nommu_region_sem);
1071
1072	/* if we want to share, we need to check for regions created by other
1073	 * mmap() calls that overlap with our proposed mapping
1074	 * - we can only share with a superset match on most regular files
1075	 * - shared mappings on character devices and memory backed files are
1076	 *   permitted to overlap inexactly as far as we are concerned for in
1077	 *   these cases, sharing is handled in the driver or filesystem rather
1078	 *   than here
1079	 */
1080	if (is_nommu_shared_mapping(vm_flags)) {
1081		struct vm_region *pregion;
1082		unsigned long pglen, rpglen, pgend, rpgend, start;
1083
1084		pglen = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1085		pgend = pgoff + pglen;
1086
1087		for (rb = rb_first(&nommu_region_tree); rb; rb = rb_next(rb)) {
1088			pregion = rb_entry(rb, struct vm_region, vm_rb);
1089
1090			if (!is_nommu_shared_mapping(pregion->vm_flags))
1091				continue;
1092
1093			/* search for overlapping mappings on the same file */
1094			if (file_inode(pregion->vm_file) !=
1095			    file_inode(file))
1096				continue;
1097
1098			if (pregion->vm_pgoff >= pgend)
1099				continue;
1100
1101			rpglen = pregion->vm_end - pregion->vm_start;
1102			rpglen = (rpglen + PAGE_SIZE - 1) >> PAGE_SHIFT;
1103			rpgend = pregion->vm_pgoff + rpglen;
1104			if (pgoff >= rpgend)
1105				continue;
1106
1107			/* handle inexactly overlapping matches between
1108			 * mappings */
1109			if ((pregion->vm_pgoff != pgoff || rpglen != pglen) &&
1110			    !(pgoff >= pregion->vm_pgoff && pgend <= rpgend)) {
1111				/* new mapping is not a subset of the region */
1112				if (!(capabilities & NOMMU_MAP_DIRECT))
1113					goto sharing_violation;
1114				continue;
1115			}
1116
1117			/* we've found a region we can share */
1118			pregion->vm_usage++;
1119			vma->vm_region = pregion;
1120			start = pregion->vm_start;
1121			start += (pgoff - pregion->vm_pgoff) << PAGE_SHIFT;
1122			vma->vm_start = start;
1123			vma->vm_end = start + len;
1124
1125			if (pregion->vm_flags & VM_MAPPED_COPY)
1126				vm_flags_set(vma, VM_MAPPED_COPY);
1127			else {
1128				ret = do_mmap_shared_file(vma);
1129				if (ret < 0) {
1130					vma->vm_region = NULL;
1131					vma->vm_start = 0;
1132					vma->vm_end = 0;
1133					pregion->vm_usage--;
1134					pregion = NULL;
1135					goto error_just_free;
1136				}
1137			}
1138			fput(region->vm_file);
1139			kmem_cache_free(vm_region_jar, region);
1140			region = pregion;
1141			result = start;
1142			goto share;
1143		}
1144
1145		/* obtain the address at which to make a shared mapping
1146		 * - this is the hook for quasi-memory character devices to
1147		 *   tell us the location of a shared mapping
1148		 */
1149		if (capabilities & NOMMU_MAP_DIRECT) {
1150			addr = file->f_op->get_unmapped_area(file, addr, len,
1151							     pgoff, flags);
1152			if (IS_ERR_VALUE(addr)) {
1153				ret = addr;
1154				if (ret != -ENOSYS)
1155					goto error_just_free;
1156
1157				/* the driver refused to tell us where to site
1158				 * the mapping so we'll have to attempt to copy
1159				 * it */
1160				ret = -ENODEV;
1161				if (!(capabilities & NOMMU_MAP_COPY))
1162					goto error_just_free;
1163
1164				capabilities &= ~NOMMU_MAP_DIRECT;
1165			} else {
1166				vma->vm_start = region->vm_start = addr;
1167				vma->vm_end = region->vm_end = addr + len;
1168			}
1169		}
1170	}
1171
1172	vma->vm_region = region;
1173
1174	/* set up the mapping
1175	 * - the region is filled in if NOMMU_MAP_DIRECT is still set
1176	 */
1177	if (file && vma->vm_flags & VM_SHARED)
1178		ret = do_mmap_shared_file(vma);
1179	else
1180		ret = do_mmap_private(vma, region, len, capabilities);
1181	if (ret < 0)
1182		goto error_just_free;
1183	add_nommu_region(region);
1184
1185	/* clear anonymous mappings that don't ask for uninitialized data */
1186	if (!vma->vm_file &&
1187	    (!IS_ENABLED(CONFIG_MMAP_ALLOW_UNINITIALIZED) ||
1188	     !(flags & MAP_UNINITIALIZED)))
1189		memset((void *)region->vm_start, 0,
1190		       region->vm_end - region->vm_start);
1191
1192	/* okay... we have a mapping; now we have to register it */
1193	result = vma->vm_start;
1194
1195	current->mm->total_vm += len >> PAGE_SHIFT;
1196
1197share:
1198	BUG_ON(!vma->vm_region);
1199	vma_iter_config(&vmi, vma->vm_start, vma->vm_end);
1200	if (vma_iter_prealloc(&vmi, vma))
1201		goto error_just_free;
1202
1203	setup_vma_to_mm(vma, current->mm);
1204	current->mm->map_count++;
1205	/* add the VMA to the tree */
1206	vma_iter_store(&vmi, vma);
1207
1208	/* we flush the region from the icache only when the first executable
1209	 * mapping of it is made  */
1210	if (vma->vm_flags & VM_EXEC && !region->vm_icache_flushed) {
1211		flush_icache_user_range(region->vm_start, region->vm_end);
1212		region->vm_icache_flushed = true;
1213	}
1214
1215	up_write(&nommu_region_sem);
1216
1217	return result;
1218
1219error_just_free:
1220	up_write(&nommu_region_sem);
1221error:
1222	vma_iter_free(&vmi);
1223	if (region->vm_file)
1224		fput(region->vm_file);
1225	kmem_cache_free(vm_region_jar, region);
1226	if (vma->vm_file)
1227		fput(vma->vm_file);
1228	vm_area_free(vma);
1229	return ret;
1230
1231sharing_violation:
1232	up_write(&nommu_region_sem);
1233	pr_warn("Attempt to share mismatched mappings\n");
1234	ret = -EINVAL;
1235	goto error;
1236
1237error_getting_vma:
1238	kmem_cache_free(vm_region_jar, region);
1239	pr_warn("Allocation of vma for %lu byte allocation from process %d failed\n",
1240			len, current->pid);
1241	show_mem();
1242	return -ENOMEM;
1243
1244error_getting_region:
1245	pr_warn("Allocation of vm region for %lu byte allocation from process %d failed\n",
1246			len, current->pid);
1247	show_mem();
1248	return -ENOMEM;
 
 
 
 
 
 
 
 
1249}
1250
1251unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
1252			      unsigned long prot, unsigned long flags,
1253			      unsigned long fd, unsigned long pgoff)
1254{
1255	struct file *file = NULL;
1256	unsigned long retval = -EBADF;
1257
1258	audit_mmap_fd(fd, flags);
1259	if (!(flags & MAP_ANONYMOUS)) {
1260		file = fget(fd);
1261		if (!file)
1262			goto out;
1263	}
1264
1265	retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
1266
1267	if (file)
1268		fput(file);
1269out:
1270	return retval;
1271}
1272
1273SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
1274		unsigned long, prot, unsigned long, flags,
1275		unsigned long, fd, unsigned long, pgoff)
1276{
1277	return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
1278}
1279
1280#ifdef __ARCH_WANT_SYS_OLD_MMAP
1281struct mmap_arg_struct {
1282	unsigned long addr;
1283	unsigned long len;
1284	unsigned long prot;
1285	unsigned long flags;
1286	unsigned long fd;
1287	unsigned long offset;
1288};
1289
1290SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
1291{
1292	struct mmap_arg_struct a;
1293
1294	if (copy_from_user(&a, arg, sizeof(a)))
1295		return -EFAULT;
1296	if (offset_in_page(a.offset))
1297		return -EINVAL;
1298
1299	return ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
1300			       a.offset >> PAGE_SHIFT);
1301}
1302#endif /* __ARCH_WANT_SYS_OLD_MMAP */
1303
1304/*
1305 * split a vma into two pieces at address 'addr', a new vma is allocated either
1306 * for the first part or the tail.
1307 */
1308static int split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma,
1309		     unsigned long addr, int new_below)
1310{
1311	struct vm_area_struct *new;
1312	struct vm_region *region;
1313	unsigned long npages;
1314	struct mm_struct *mm;
1315
1316	/* we're only permitted to split anonymous regions (these should have
1317	 * only a single usage on the region) */
1318	if (vma->vm_file)
1319		return -ENOMEM;
1320
1321	mm = vma->vm_mm;
1322	if (mm->map_count >= sysctl_max_map_count)
1323		return -ENOMEM;
1324
1325	region = kmem_cache_alloc(vm_region_jar, GFP_KERNEL);
1326	if (!region)
1327		return -ENOMEM;
1328
1329	new = vm_area_dup(vma);
1330	if (!new)
1331		goto err_vma_dup;
1332
 
 
 
 
 
 
1333	/* most fields are the same, copy all, and then fixup */
1334	*region = *vma->vm_region;
1335	new->vm_region = region;
1336
1337	npages = (addr - vma->vm_start) >> PAGE_SHIFT;
1338
1339	if (new_below) {
1340		region->vm_top = region->vm_end = new->vm_end = addr;
1341	} else {
1342		region->vm_start = new->vm_start = addr;
1343		region->vm_pgoff = new->vm_pgoff += npages;
1344	}
1345
1346	vma_iter_config(vmi, new->vm_start, new->vm_end);
1347	if (vma_iter_prealloc(vmi, vma)) {
1348		pr_warn("Allocation of vma tree for process %d failed\n",
1349			current->pid);
1350		goto err_vmi_preallocate;
1351	}
1352
1353	if (new->vm_ops && new->vm_ops->open)
1354		new->vm_ops->open(new);
1355
1356	down_write(&nommu_region_sem);
1357	delete_nommu_region(vma->vm_region);
1358	if (new_below) {
1359		vma->vm_region->vm_start = vma->vm_start = addr;
1360		vma->vm_region->vm_pgoff = vma->vm_pgoff += npages;
1361	} else {
1362		vma->vm_region->vm_end = vma->vm_end = addr;
1363		vma->vm_region->vm_top = addr;
1364	}
1365	add_nommu_region(vma->vm_region);
1366	add_nommu_region(new->vm_region);
1367	up_write(&nommu_region_sem);
1368
1369	setup_vma_to_mm(vma, mm);
1370	setup_vma_to_mm(new, mm);
1371	vma_iter_store(vmi, new);
 
 
1372	mm->map_count++;
1373	return 0;
1374
1375err_vmi_preallocate:
1376	vm_area_free(new);
1377err_vma_dup:
1378	kmem_cache_free(vm_region_jar, region);
1379	return -ENOMEM;
1380}
1381
1382/*
1383 * shrink a VMA by removing the specified chunk from either the beginning or
1384 * the end
1385 */
1386static int vmi_shrink_vma(struct vma_iterator *vmi,
1387		      struct vm_area_struct *vma,
1388		      unsigned long from, unsigned long to)
1389{
1390	struct vm_region *region;
1391
1392	/* adjust the VMA's pointers, which may reposition it in the MM's tree
1393	 * and list */
1394	if (from > vma->vm_start) {
1395		if (vma_iter_clear_gfp(vmi, from, vma->vm_end, GFP_KERNEL))
1396			return -ENOMEM;
1397		vma->vm_end = from;
1398	} else {
1399		if (vma_iter_clear_gfp(vmi, vma->vm_start, to, GFP_KERNEL))
1400			return -ENOMEM;
1401		vma->vm_start = to;
1402	}
 
1403
1404	/* cut the backing region down to size */
1405	region = vma->vm_region;
1406	BUG_ON(region->vm_usage != 1);
1407
1408	down_write(&nommu_region_sem);
1409	delete_nommu_region(region);
1410	if (from > region->vm_start) {
1411		to = region->vm_top;
1412		region->vm_top = region->vm_end = from;
1413	} else {
1414		region->vm_start = to;
1415	}
1416	add_nommu_region(region);
1417	up_write(&nommu_region_sem);
1418
1419	free_page_series(from, to);
1420	return 0;
1421}
1422
1423/*
1424 * release a mapping
1425 * - under NOMMU conditions the chunk to be unmapped must be backed by a single
1426 *   VMA, though it need not cover the whole VMA
1427 */
1428int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, struct list_head *uf)
1429{
1430	VMA_ITERATOR(vmi, mm, start);
1431	struct vm_area_struct *vma;
1432	unsigned long end;
1433	int ret = 0;
1434
1435	len = PAGE_ALIGN(len);
1436	if (len == 0)
1437		return -EINVAL;
1438
1439	end = start + len;
1440
1441	/* find the first potentially overlapping VMA */
1442	vma = vma_find(&vmi, end);
1443	if (!vma) {
1444		static int limit;
1445		if (limit < 5) {
1446			pr_warn("munmap of memory not mmapped by process %d (%s): 0x%lx-0x%lx\n",
1447					current->pid, current->comm,
1448					start, start + len - 1);
1449			limit++;
1450		}
1451		return -EINVAL;
1452	}
1453
1454	/* we're allowed to split an anonymous VMA but not a file-backed one */
1455	if (vma->vm_file) {
1456		do {
1457			if (start > vma->vm_start)
1458				return -EINVAL;
1459			if (end == vma->vm_end)
1460				goto erase_whole_vma;
1461			vma = vma_find(&vmi, end);
1462		} while (vma);
1463		return -EINVAL;
1464	} else {
1465		/* the chunk must be a subset of the VMA found */
1466		if (start == vma->vm_start && end == vma->vm_end)
1467			goto erase_whole_vma;
1468		if (start < vma->vm_start || end > vma->vm_end)
1469			return -EINVAL;
1470		if (offset_in_page(start))
1471			return -EINVAL;
1472		if (end != vma->vm_end && offset_in_page(end))
1473			return -EINVAL;
1474		if (start != vma->vm_start && end != vma->vm_end) {
1475			ret = split_vma(&vmi, vma, start, 1);
1476			if (ret < 0)
1477				return ret;
1478		}
1479		return vmi_shrink_vma(&vmi, vma, start, end);
1480	}
1481
1482erase_whole_vma:
1483	if (delete_vma_from_mm(vma))
1484		ret = -ENOMEM;
1485	else
1486		delete_vma(mm, vma);
1487	return ret;
1488}
1489
1490int vm_munmap(unsigned long addr, size_t len)
1491{
1492	struct mm_struct *mm = current->mm;
1493	int ret;
1494
1495	mmap_write_lock(mm);
1496	ret = do_munmap(mm, addr, len, NULL);
1497	mmap_write_unlock(mm);
1498	return ret;
1499}
1500EXPORT_SYMBOL(vm_munmap);
1501
1502SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
1503{
1504	return vm_munmap(addr, len);
1505}
1506
1507/*
1508 * release all the mappings made in a process's VM space
1509 */
1510void exit_mmap(struct mm_struct *mm)
1511{
1512	VMA_ITERATOR(vmi, mm, 0);
1513	struct vm_area_struct *vma;
1514
1515	if (!mm)
1516		return;
1517
1518	mm->total_vm = 0;
1519
1520	/*
1521	 * Lock the mm to avoid assert complaining even though this is the only
1522	 * user of the mm
1523	 */
1524	mmap_write_lock(mm);
1525	for_each_vma(vmi, vma) {
1526		cleanup_vma_from_mm(vma);
1527		delete_vma(mm, vma);
1528		cond_resched();
1529	}
1530	__mt_destroy(&mm->mm_mt);
1531	mmap_write_unlock(mm);
1532}
1533
 
 
 
 
 
1534/*
1535 * expand (or shrink) an existing mapping, potentially moving it at the same
1536 * time (controlled by the MREMAP_MAYMOVE flag and available VM space)
1537 *
1538 * under NOMMU conditions, we only permit changing a mapping's size, and only
1539 * as long as it stays within the region allocated by do_mmap_private() and the
1540 * block is not shareable
1541 *
1542 * MREMAP_FIXED is not supported under NOMMU conditions
1543 */
1544static unsigned long do_mremap(unsigned long addr,
1545			unsigned long old_len, unsigned long new_len,
1546			unsigned long flags, unsigned long new_addr)
1547{
1548	struct vm_area_struct *vma;
1549
1550	/* insanity checks first */
1551	old_len = PAGE_ALIGN(old_len);
1552	new_len = PAGE_ALIGN(new_len);
1553	if (old_len == 0 || new_len == 0)
1554		return (unsigned long) -EINVAL;
1555
1556	if (offset_in_page(addr))
1557		return -EINVAL;
1558
1559	if (flags & MREMAP_FIXED && new_addr != addr)
1560		return (unsigned long) -EINVAL;
1561
1562	vma = find_vma_exact(current->mm, addr, old_len);
1563	if (!vma)
1564		return (unsigned long) -EINVAL;
1565
1566	if (vma->vm_end != vma->vm_start + old_len)
1567		return (unsigned long) -EFAULT;
1568
1569	if (is_nommu_shared_mapping(vma->vm_flags))
1570		return (unsigned long) -EPERM;
1571
1572	if (new_len > vma->vm_region->vm_end - vma->vm_region->vm_start)
1573		return (unsigned long) -ENOMEM;
1574
1575	/* all checks complete - do it */
1576	vma->vm_end = vma->vm_start + new_len;
1577	return vma->vm_start;
1578}
1579
1580SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
1581		unsigned long, new_len, unsigned long, flags,
1582		unsigned long, new_addr)
1583{
1584	unsigned long ret;
1585
1586	mmap_write_lock(current->mm);
1587	ret = do_mremap(addr, old_len, new_len, flags, new_addr);
1588	mmap_write_unlock(current->mm);
1589	return ret;
1590}
1591
1592struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
1593			 unsigned int foll_flags)
1594{
1595	return NULL;
1596}
1597
1598int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
1599		unsigned long pfn, unsigned long size, pgprot_t prot)
1600{
1601	if (addr != (pfn << PAGE_SHIFT))
1602		return -EINVAL;
1603
1604	vm_flags_set(vma, VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP);
1605	return 0;
1606}
1607EXPORT_SYMBOL(remap_pfn_range);
1608
1609int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len)
1610{
1611	unsigned long pfn = start >> PAGE_SHIFT;
1612	unsigned long vm_len = vma->vm_end - vma->vm_start;
1613
1614	pfn += vma->vm_pgoff;
1615	return io_remap_pfn_range(vma, vma->vm_start, pfn, vm_len, vma->vm_page_prot);
1616}
1617EXPORT_SYMBOL(vm_iomap_memory);
1618
1619int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
1620			unsigned long pgoff)
1621{
1622	unsigned int size = vma->vm_end - vma->vm_start;
1623
1624	if (!(vma->vm_flags & VM_USERMAP))
1625		return -EINVAL;
1626
1627	vma->vm_start = (unsigned long)(addr + (pgoff << PAGE_SHIFT));
1628	vma->vm_end = vma->vm_start + size;
1629
1630	return 0;
1631}
1632EXPORT_SYMBOL(remap_vmalloc_range);
1633
1634vm_fault_t filemap_fault(struct vm_fault *vmf)
1635{
1636	BUG();
1637	return 0;
1638}
1639EXPORT_SYMBOL(filemap_fault);
1640
1641vm_fault_t filemap_map_pages(struct vm_fault *vmf,
1642		pgoff_t start_pgoff, pgoff_t end_pgoff)
1643{
1644	BUG();
1645	return 0;
1646}
1647EXPORT_SYMBOL(filemap_map_pages);
1648
1649static int __access_remote_vm(struct mm_struct *mm, unsigned long addr,
1650			      void *buf, int len, unsigned int gup_flags)
1651{
1652	struct vm_area_struct *vma;
1653	int write = gup_flags & FOLL_WRITE;
1654
1655	if (mmap_read_lock_killable(mm))
1656		return 0;
1657
1658	/* the access must start within one of the target process's mappings */
1659	vma = find_vma(mm, addr);
1660	if (vma) {
1661		/* don't overrun this mapping */
1662		if (addr + len >= vma->vm_end)
1663			len = vma->vm_end - addr;
1664
1665		/* only read or write mappings where it is permitted */
1666		if (write && vma->vm_flags & VM_MAYWRITE)
1667			copy_to_user_page(vma, NULL, addr,
1668					 (void *) addr, buf, len);
1669		else if (!write && vma->vm_flags & VM_MAYREAD)
1670			copy_from_user_page(vma, NULL, addr,
1671					    buf, (void *) addr, len);
1672		else
1673			len = 0;
1674	} else {
1675		len = 0;
1676	}
1677
1678	mmap_read_unlock(mm);
1679
1680	return len;
1681}
1682
1683/**
1684 * access_remote_vm - access another process' address space
1685 * @mm:		the mm_struct of the target address space
1686 * @addr:	start address to access
1687 * @buf:	source or destination buffer
1688 * @len:	number of bytes to transfer
1689 * @gup_flags:	flags modifying lookup behaviour
1690 *
1691 * The caller must hold a reference on @mm.
1692 */
1693int access_remote_vm(struct mm_struct *mm, unsigned long addr,
1694		void *buf, int len, unsigned int gup_flags)
1695{
1696	return __access_remote_vm(mm, addr, buf, len, gup_flags);
1697}
1698
1699/*
1700 * Access another process' address space.
1701 * - source/target buffer must be kernel space
1702 */
1703int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len,
1704		unsigned int gup_flags)
1705{
1706	struct mm_struct *mm;
1707
1708	if (addr + len < addr)
1709		return 0;
1710
1711	mm = get_task_mm(tsk);
1712	if (!mm)
1713		return 0;
1714
1715	len = __access_remote_vm(mm, addr, buf, len, gup_flags);
1716
1717	mmput(mm);
1718	return len;
1719}
1720EXPORT_SYMBOL_GPL(access_process_vm);
1721
1722/**
1723 * nommu_shrink_inode_mappings - Shrink the shared mappings on an inode
1724 * @inode: The inode to check
1725 * @size: The current filesize of the inode
1726 * @newsize: The proposed filesize of the inode
1727 *
1728 * Check the shared mappings on an inode on behalf of a shrinking truncate to
1729 * make sure that any outstanding VMAs aren't broken and then shrink the
1730 * vm_regions that extend beyond so that do_mmap() doesn't
1731 * automatically grant mappings that are too large.
1732 */
1733int nommu_shrink_inode_mappings(struct inode *inode, size_t size,
1734				size_t newsize)
1735{
1736	struct vm_area_struct *vma;
1737	struct vm_region *region;
1738	pgoff_t low, high;
1739	size_t r_size, r_top;
1740
1741	low = newsize >> PAGE_SHIFT;
1742	high = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1743
1744	down_write(&nommu_region_sem);
1745	i_mmap_lock_read(inode->i_mapping);
1746
1747	/* search for VMAs that fall within the dead zone */
1748	vma_interval_tree_foreach(vma, &inode->i_mapping->i_mmap, low, high) {
1749		/* found one - only interested if it's shared out of the page
1750		 * cache */
1751		if (vma->vm_flags & VM_SHARED) {
1752			i_mmap_unlock_read(inode->i_mapping);
1753			up_write(&nommu_region_sem);
1754			return -ETXTBSY; /* not quite true, but near enough */
1755		}
1756	}
1757
1758	/* reduce any regions that overlap the dead zone - if in existence,
1759	 * these will be pointed to by VMAs that don't overlap the dead zone
1760	 *
1761	 * we don't check for any regions that start beyond the EOF as there
1762	 * shouldn't be any
1763	 */
1764	vma_interval_tree_foreach(vma, &inode->i_mapping->i_mmap, 0, ULONG_MAX) {
1765		if (!(vma->vm_flags & VM_SHARED))
1766			continue;
1767
1768		region = vma->vm_region;
1769		r_size = region->vm_top - region->vm_start;
1770		r_top = (region->vm_pgoff << PAGE_SHIFT) + r_size;
1771
1772		if (r_top > newsize) {
1773			region->vm_top -= r_top - newsize;
1774			if (region->vm_end > region->vm_top)
1775				region->vm_end = region->vm_top;
1776		}
1777	}
1778
1779	i_mmap_unlock_read(inode->i_mapping);
1780	up_write(&nommu_region_sem);
1781	return 0;
1782}
1783
1784/*
1785 * Initialise sysctl_user_reserve_kbytes.
1786 *
1787 * This is intended to prevent a user from starting a single memory hogging
1788 * process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER
1789 * mode.
1790 *
1791 * The default value is min(3% of free memory, 128MB)
1792 * 128MB is enough to recover with sshd/login, bash, and top/kill.
1793 */
1794static int __meminit init_user_reserve(void)
1795{
1796	unsigned long free_kbytes;
1797
1798	free_kbytes = K(global_zone_page_state(NR_FREE_PAGES));
1799
1800	sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17);
1801	return 0;
1802}
1803subsys_initcall(init_user_reserve);
1804
1805/*
1806 * Initialise sysctl_admin_reserve_kbytes.
1807 *
1808 * The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin
1809 * to log in and kill a memory hogging process.
1810 *
1811 * Systems with more than 256MB will reserve 8MB, enough to recover
1812 * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
1813 * only reserve 3% of free pages by default.
1814 */
1815static int __meminit init_admin_reserve(void)
1816{
1817	unsigned long free_kbytes;
1818
1819	free_kbytes = K(global_zone_page_state(NR_FREE_PAGES));
1820
1821	sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
1822	return 0;
1823}
1824subsys_initcall(init_admin_reserve);