util.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2#include <linux/mm.h>
   3#include <linux/slab.h>
   4#include <linux/string.h>
   5#include <linux/compiler.h>
   6#include <linux/export.h>
   7#include <linux/err.h>
   8#include <linux/sched.h>
   9#include <linux/sched/mm.h>
  10#include <linux/sched/signal.h>
  11#include <linux/sched/task_stack.h>
  12#include <linux/security.h>
  13#include <linux/swap.h>
  14#include <linux/swapops.h>
  15#include <linux/sysctl.h>
  16#include <linux/mman.h>
  17#include <linux/hugetlb.h>
  18#include <linux/vmalloc.h>
  19#include <linux/userfaultfd_k.h>
  20#include <linux/elf.h>
  21#include <linux/elf-randomize.h>
  22#include <linux/personality.h>
  23#include <linux/random.h>
  24#include <linux/processor.h>
  25#include <linux/sizes.h>
  26#include <linux/compat.h>
  27#include <linux/fsnotify.h>
  28#include <linux/page_idle.h>
  29
  30#include <linux/uaccess.h>
  31
  32#include <kunit/visibility.h>
  33
  34#include "internal.h"
  35#include "swap.h"
  36
  37/**
  38 * kfree_const - conditionally free memory
  39 * @x: pointer to the memory
  40 *
  41 * Function calls kfree only if @x is not in .rodata section.
  42 */
  43void kfree_const(const void *x)
  44{
  45	if (!is_kernel_rodata((unsigned long)x))
  46		kfree(x);
  47}
  48EXPORT_SYMBOL(kfree_const);
  49
  50/**
  51 * __kmemdup_nul - Create a NUL-terminated string from @s, which might be unterminated.
  52 * @s: The data to copy
  53 * @len: The size of the data, not including the NUL terminator
  54 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  55 *
  56 * Return: newly allocated copy of @s with NUL-termination or %NULL in
  57 * case of error
  58 */
  59static __always_inline char *__kmemdup_nul(const char *s, size_t len, gfp_t gfp)
  60{
  61	char *buf;
  62
  63	/* '+1' for the NUL terminator */
  64	buf = kmalloc_track_caller(len + 1, gfp);
  65	if (!buf)
  66		return NULL;
  67
  68	memcpy(buf, s, len);
  69	/* Ensure the buf is always NUL-terminated, regardless of @s. */
  70	buf[len] = '\0';
  71	return buf;
  72}
  73
  74/**
  75 * kstrdup - allocate space for and copy an existing string
  76 * @s: the string to duplicate
  77 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  78 *
  79 * Return: newly allocated copy of @s or %NULL in case of error
  80 */
  81noinline
  82char *kstrdup(const char *s, gfp_t gfp)
  83{
  84	return s ? __kmemdup_nul(s, strlen(s), gfp) : NULL;
  85}
  86EXPORT_SYMBOL(kstrdup);
  87
  88/**
  89 * kstrdup_const - conditionally duplicate an existing const string
  90 * @s: the string to duplicate
  91 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  92 *
  93 * Note: Strings allocated by kstrdup_const should be freed by kfree_const and
  94 * must not be passed to krealloc().
  95 *
  96 * Return: source string if it is in .rodata section otherwise
  97 * fallback to kstrdup.
  98 */
  99const char *kstrdup_const(const char *s, gfp_t gfp)
 100{
 101	if (is_kernel_rodata((unsigned long)s))
 102		return s;
 103
 104	return kstrdup(s, gfp);
 105}
 106EXPORT_SYMBOL(kstrdup_const);
 107
 108/**
 109 * kstrndup - allocate space for and copy an existing string
 110 * @s: the string to duplicate
 111 * @max: read at most @max chars from @s
 112 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
 113 *
 114 * Note: Use kmemdup_nul() instead if the size is known exactly.
 115 *
 116 * Return: newly allocated copy of @s or %NULL in case of error
 117 */
 118char *kstrndup(const char *s, size_t max, gfp_t gfp)
 119{
 120	return s ? __kmemdup_nul(s, strnlen(s, max), gfp) : NULL;
 121}
 122EXPORT_SYMBOL(kstrndup);
 123
 124/**
 125 * kmemdup - duplicate region of memory
 126 *
 127 * @src: memory region to duplicate
 128 * @len: memory region length
 129 * @gfp: GFP mask to use
 130 *
 131 * Return: newly allocated copy of @src or %NULL in case of error,
 132 * result is physically contiguous. Use kfree() to free.
 133 */
 134void *kmemdup_noprof(const void *src, size_t len, gfp_t gfp)
 135{
 136	void *p;
 137
 138	p = kmalloc_node_track_caller_noprof(len, gfp, NUMA_NO_NODE, _RET_IP_);
 139	if (p)
 140		memcpy(p, src, len);
 141	return p;
 142}
 143EXPORT_SYMBOL(kmemdup_noprof);
 144
 145/**
 146 * kmemdup_array - duplicate a given array.
 147 *
 148 * @src: array to duplicate.
 149 * @count: number of elements to duplicate from array.
 150 * @element_size: size of each element of array.
 151 * @gfp: GFP mask to use.
 152 *
 153 * Return: duplicated array of @src or %NULL in case of error,
 154 * result is physically contiguous. Use kfree() to free.
 155 */
 156void *kmemdup_array(const void *src, size_t count, size_t element_size, gfp_t gfp)
 157{
 158	return kmemdup(src, size_mul(element_size, count), gfp);
 159}
 160EXPORT_SYMBOL(kmemdup_array);
 161
 162/**
 163 * kvmemdup - duplicate region of memory
 164 *
 165 * @src: memory region to duplicate
 166 * @len: memory region length
 167 * @gfp: GFP mask to use
 168 *
 169 * Return: newly allocated copy of @src or %NULL in case of error,
 170 * result may be not physically contiguous. Use kvfree() to free.
 171 */
 172void *kvmemdup(const void *src, size_t len, gfp_t gfp)
 173{
 174	void *p;
 175
 176	p = kvmalloc(len, gfp);
 177	if (p)
 178		memcpy(p, src, len);
 179	return p;
 180}
 181EXPORT_SYMBOL(kvmemdup);
 182
 183/**
 184 * kmemdup_nul - Create a NUL-terminated string from unterminated data
 185 * @s: The data to stringify
 186 * @len: The size of the data
 187 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
 188 *
 189 * Return: newly allocated copy of @s with NUL-termination or %NULL in
 190 * case of error
 191 */
 192char *kmemdup_nul(const char *s, size_t len, gfp_t gfp)
 193{
 194	return s ? __kmemdup_nul(s, len, gfp) : NULL;
 195}
 196EXPORT_SYMBOL(kmemdup_nul);
 197
 198static kmem_buckets *user_buckets __ro_after_init;
 199
 200static int __init init_user_buckets(void)
 201{
 202	user_buckets = kmem_buckets_create("memdup_user", 0, 0, INT_MAX, NULL);
 203
 204	return 0;
 205}
 206subsys_initcall(init_user_buckets);
 207
 208/**
 209 * memdup_user - duplicate memory region from user space
 210 *
 211 * @src: source address in user space
 212 * @len: number of bytes to copy
 213 *
 214 * Return: an ERR_PTR() on failure.  Result is physically
 215 * contiguous, to be freed by kfree().
 216 */
 217void *memdup_user(const void __user *src, size_t len)
 218{
 219	void *p;
 220
 221	p = kmem_buckets_alloc_track_caller(user_buckets, len, GFP_USER | __GFP_NOWARN);
 222	if (!p)
 223		return ERR_PTR(-ENOMEM);
 224
 225	if (copy_from_user(p, src, len)) {
 226		kfree(p);
 227		return ERR_PTR(-EFAULT);
 228	}
 229
 230	return p;
 231}
 232EXPORT_SYMBOL(memdup_user);
 233
 234/**
 235 * vmemdup_user - duplicate memory region from user space
 236 *
 237 * @src: source address in user space
 238 * @len: number of bytes to copy
 239 *
 240 * Return: an ERR_PTR() on failure.  Result may be not
 241 * physically contiguous.  Use kvfree() to free.
 242 */
 243void *vmemdup_user(const void __user *src, size_t len)
 244{
 245	void *p;
 246
 247	p = kmem_buckets_valloc(user_buckets, len, GFP_USER);
 248	if (!p)
 249		return ERR_PTR(-ENOMEM);
 250
 251	if (copy_from_user(p, src, len)) {
 252		kvfree(p);
 253		return ERR_PTR(-EFAULT);
 254	}
 255
 256	return p;
 257}
 258EXPORT_SYMBOL(vmemdup_user);
 259
 260/**
 261 * strndup_user - duplicate an existing string from user space
 262 * @s: The string to duplicate
 263 * @n: Maximum number of bytes to copy, including the trailing NUL.
 264 *
 265 * Return: newly allocated copy of @s or an ERR_PTR() in case of error
 266 */
 267char *strndup_user(const char __user *s, long n)
 268{
 269	char *p;
 270	long length;
 271
 272	length = strnlen_user(s, n);
 273
 274	if (!length)
 275		return ERR_PTR(-EFAULT);
 276
 277	if (length > n)
 278		return ERR_PTR(-EINVAL);
 279
 280	p = memdup_user(s, length);
 281
 282	if (IS_ERR(p))
 283		return p;
 284
 285	p[length - 1] = '\0';
 286
 287	return p;
 288}
 289EXPORT_SYMBOL(strndup_user);
 290
 291/**
 292 * memdup_user_nul - duplicate memory region from user space and NUL-terminate
 293 *
 294 * @src: source address in user space
 295 * @len: number of bytes to copy
 296 *
 297 * Return: an ERR_PTR() on failure.
 298 */
 299void *memdup_user_nul(const void __user *src, size_t len)
 300{
 301	char *p;
 302
 303	p = kmem_buckets_alloc_track_caller(user_buckets, len + 1, GFP_USER | __GFP_NOWARN);
 304	if (!p)
 305		return ERR_PTR(-ENOMEM);
 306
 307	if (copy_from_user(p, src, len)) {
 308		kfree(p);
 309		return ERR_PTR(-EFAULT);
 310	}
 311	p[len] = '\0';
 312
 313	return p;
 314}
 315EXPORT_SYMBOL(memdup_user_nul);
 316
 317/* Check if the vma is being used as a stack by this task */
 318int vma_is_stack_for_current(const struct vm_area_struct *vma)
 319{
 320	struct task_struct * __maybe_unused t = current;
 321
 322	return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
 323}
 324
 325/*
 326 * Change backing file, only valid to use during initial VMA setup.
 327 */
 328void vma_set_file(struct vm_area_struct *vma, struct file *file)
 329{
 330	/* Changing an anonymous vma with this is illegal */
 331	get_file(file);
 332	swap(vma->vm_file, file);
 333	fput(file);
 334}
 335EXPORT_SYMBOL(vma_set_file);
 336
 337#ifndef STACK_RND_MASK
 338#define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12))     /* 8MB of VA */
 339#endif
 340
 341unsigned long randomize_stack_top(unsigned long stack_top)
 342{
 343	unsigned long random_variable = 0;
 344
 345	if (current->flags & PF_RANDOMIZE) {
 346		random_variable = get_random_long();
 347		random_variable &= STACK_RND_MASK;
 348		random_variable <<= PAGE_SHIFT;
 349	}
 350#ifdef CONFIG_STACK_GROWSUP
 351	return PAGE_ALIGN(stack_top) + random_variable;
 352#else
 353	return PAGE_ALIGN(stack_top) - random_variable;
 354#endif
 355}
 356
 357/**
 358 * randomize_page - Generate a random, page aligned address
 359 * @start:	The smallest acceptable address the caller will take.
 360 * @range:	The size of the area, starting at @start, within which the
 361 *		random address must fall.
 362 *
 363 * If @start + @range would overflow, @range is capped.
 364 *
 365 * NOTE: Historical use of randomize_range, which this replaces, presumed that
 366 * @start was already page aligned.  We now align it regardless.
 367 *
 368 * Return: A page aligned address within [start, start + range).  On error,
 369 * @start is returned.
 370 */
 371unsigned long randomize_page(unsigned long start, unsigned long range)
 372{
 373	if (!PAGE_ALIGNED(start)) {
 374		range -= PAGE_ALIGN(start) - start;
 375		start = PAGE_ALIGN(start);
 376	}
 377
 378	if (start > ULONG_MAX - range)
 379		range = ULONG_MAX - start;
 380
 381	range >>= PAGE_SHIFT;
 382
 383	if (range == 0)
 384		return start;
 385
 386	return start + (get_random_long() % range << PAGE_SHIFT);
 387}
 388
 389#ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
 390unsigned long __weak arch_randomize_brk(struct mm_struct *mm)
 391{
 392	/* Is the current task 32bit ? */
 393	if (!IS_ENABLED(CONFIG_64BIT) || is_compat_task())
 394		return randomize_page(mm->brk, SZ_32M);
 395
 396	return randomize_page(mm->brk, SZ_1G);
 397}
 398
 399unsigned long arch_mmap_rnd(void)
 400{
 401	unsigned long rnd;
 402
 403#ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
 404	if (is_compat_task())
 405		rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
 406	else
 407#endif /* CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS */
 408		rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
 409
 410	return rnd << PAGE_SHIFT;
 411}
 412
 413static int mmap_is_legacy(const struct rlimit *rlim_stack)
 414{
 415	if (current->personality & ADDR_COMPAT_LAYOUT)
 416		return 1;
 417
 418	/* On parisc the stack always grows up - so a unlimited stack should
 419	 * not be an indicator to use the legacy memory layout. */
 420	if (rlim_stack->rlim_cur == RLIM_INFINITY &&
 421		!IS_ENABLED(CONFIG_STACK_GROWSUP))
 422		return 1;
 423
 424	return sysctl_legacy_va_layout;
 425}
 426
 427/*
 428 * Leave enough space between the mmap area and the stack to honour ulimit in
 429 * the face of randomisation.
 430 */
 431#define MIN_GAP		(SZ_128M)
 432#define MAX_GAP		(STACK_TOP / 6 * 5)
 433
 434static unsigned long mmap_base(const unsigned long rnd, const struct rlimit *rlim_stack)
 435{
 436#ifdef CONFIG_STACK_GROWSUP
 437	/*
 438	 * For an upwards growing stack the calculation is much simpler.
 439	 * Memory for the maximum stack size is reserved at the top of the
 440	 * task. mmap_base starts directly below the stack and grows
 441	 * downwards.
 442	 */
 443	return PAGE_ALIGN_DOWN(mmap_upper_limit(rlim_stack) - rnd);
 444#else
 445	unsigned long gap = rlim_stack->rlim_cur;
 446	unsigned long pad = stack_guard_gap;
 447
 448	/* Account for stack randomization if necessary */
 449	if (current->flags & PF_RANDOMIZE)
 450		pad += (STACK_RND_MASK << PAGE_SHIFT);
 451
 452	/* Values close to RLIM_INFINITY can overflow. */
 453	if (gap + pad > gap)
 454		gap += pad;
 455
 456	if (gap < MIN_GAP && MIN_GAP < MAX_GAP)
 457		gap = MIN_GAP;
 458	else if (gap > MAX_GAP)
 459		gap = MAX_GAP;
 460
 461	return PAGE_ALIGN(STACK_TOP - gap - rnd);
 462#endif
 463}
 464
 465void arch_pick_mmap_layout(struct mm_struct *mm, const struct rlimit *rlim_stack)
 466{
 467	unsigned long random_factor = 0UL;
 468
 469	if (current->flags & PF_RANDOMIZE)
 470		random_factor = arch_mmap_rnd();
 471
 472	if (mmap_is_legacy(rlim_stack)) {
 473		mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
 474		mm_flags_clear(MMF_TOPDOWN, mm);
 475	} else {
 476		mm->mmap_base = mmap_base(random_factor, rlim_stack);
 477		mm_flags_set(MMF_TOPDOWN, mm);
 478	}
 479}
 480#elif defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
 481void arch_pick_mmap_layout(struct mm_struct *mm, const struct rlimit *rlim_stack)
 482{
 483	mm->mmap_base = TASK_UNMAPPED_BASE;
 484	mm_flags_clear(MMF_TOPDOWN, mm);
 485}
 486#endif
 487#ifdef CONFIG_MMU
 488EXPORT_SYMBOL_IF_KUNIT(arch_pick_mmap_layout);
 489#endif
 490
 491/**
 492 * __account_locked_vm - account locked pages to an mm's locked_vm
 493 * @mm:          mm to account against
 494 * @pages:       number of pages to account
 495 * @inc:         %true if @pages should be considered positive, %false if not
 496 * @task:        task used to check RLIMIT_MEMLOCK
 497 * @bypass_rlim: %true if checking RLIMIT_MEMLOCK should be skipped
 498 *
 499 * Assumes @task and @mm are valid (i.e. at least one reference on each), and
 500 * that mmap_lock is held as writer.
 501 *
 502 * Return:
 503 * * 0       on success
 504 * * -ENOMEM if RLIMIT_MEMLOCK would be exceeded.
 505 */
 506int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc,
 507			const struct task_struct *task, bool bypass_rlim)
 508{
 509	unsigned long locked_vm, limit;
 510	int ret = 0;
 511
 512	mmap_assert_write_locked(mm);
 513
 514	locked_vm = mm->locked_vm;
 515	if (inc) {
 516		if (!bypass_rlim) {
 517			limit = task_rlimit(task, RLIMIT_MEMLOCK) >> PAGE_SHIFT;
 518			if (locked_vm + pages > limit)
 519				ret = -ENOMEM;
 520		}
 521		if (!ret)
 522			mm->locked_vm = locked_vm + pages;
 523	} else {
 524		WARN_ON_ONCE(pages > locked_vm);
 525		mm->locked_vm = locked_vm - pages;
 526	}
 527
 528	pr_debug("%s: [%d] caller %ps %c%lu %lu/%lu%s\n", __func__, task->pid,
 529		 (void *)_RET_IP_, (inc) ? '+' : '-', pages << PAGE_SHIFT,
 530		 locked_vm << PAGE_SHIFT, task_rlimit(task, RLIMIT_MEMLOCK),
 531		 ret ? " - exceeded" : "");
 532
 533	return ret;
 534}
 535EXPORT_SYMBOL_GPL(__account_locked_vm);
 536
 537/**
 538 * account_locked_vm - account locked pages to an mm's locked_vm
 539 * @mm:          mm to account against, may be NULL
 540 * @pages:       number of pages to account
 541 * @inc:         %true if @pages should be considered positive, %false if not
 542 *
 543 * Assumes a non-NULL @mm is valid (i.e. at least one reference on it).
 544 *
 545 * Return:
 546 * * 0       on success, or if mm is NULL
 547 * * -ENOMEM if RLIMIT_MEMLOCK would be exceeded.
 548 */
 549int account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc)
 550{
 551	int ret;
 552
 553	if (pages == 0 || !mm)
 554		return 0;
 555
 556	mmap_write_lock(mm);
 557	ret = __account_locked_vm(mm, pages, inc, current,
 558				  capable(CAP_IPC_LOCK));
 559	mmap_write_unlock(mm);
 560
 561	return ret;
 562}
 563EXPORT_SYMBOL_GPL(account_locked_vm);
 564
 565unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
 566	unsigned long len, unsigned long prot,
 567	unsigned long flag, unsigned long pgoff)
 568{
 569	loff_t off = (loff_t)pgoff << PAGE_SHIFT;
 570	unsigned long ret;
 571	struct mm_struct *mm = current->mm;
 572	unsigned long populate;
 573	LIST_HEAD(uf);
 574
 575	ret = security_mmap_file(file, prot, flag);
 576	if (!ret)
 577		ret = fsnotify_mmap_perm(file, prot, off, len);
 578	if (!ret) {
 579		if (mmap_write_lock_killable(mm))
 580			return -EINTR;
 581		ret = do_mmap(file, addr, len, prot, flag, 0, pgoff, &populate,
 582			      &uf);
 583		mmap_write_unlock(mm);
 584		userfaultfd_unmap_complete(mm, &uf);
 585		if (populate)
 586			mm_populate(ret, populate);
 587	}
 588	return ret;
 589}
 590
 591/*
 592 * Perform a userland memory mapping into the current process address space. See
 593 * the comment for do_mmap() for more details on this operation in general.
 594 *
 595 * This differs from do_mmap() in that:
 596 *
 597 * a. An offset parameter is provided rather than pgoff, which is both checked
 598 *    for overflow and page alignment.
 599 * b. mmap locking is performed on the caller's behalf.
 600 * c. Userfaultfd unmap events and memory population are handled.
 601 *
 602 * This means that this function performs essentially the same work as if
 603 * userland were invoking mmap (2).
 604 *
 605 * Returns either an error, or the address at which the requested mapping has
 606 * been performed.
 607 */
 608unsigned long vm_mmap(struct file *file, unsigned long addr,
 609	unsigned long len, unsigned long prot,
 610	unsigned long flag, unsigned long offset)
 611{
 612	if (unlikely(offset + PAGE_ALIGN(len) < offset))
 613		return -EINVAL;
 614	if (unlikely(offset_in_page(offset)))
 615		return -EINVAL;
 616
 617	return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
 618}
 619EXPORT_SYMBOL(vm_mmap);
 620
 621/**
 622 * __vmalloc_array - allocate memory for a virtually contiguous array.
 623 * @n: number of elements.
 624 * @size: element size.
 625 * @flags: the type of memory to allocate (see kmalloc).
 626 */
 627void *__vmalloc_array_noprof(size_t n, size_t size, gfp_t flags)
 628{
 629	size_t bytes;
 630
 631	if (unlikely(check_mul_overflow(n, size, &bytes)))
 632		return NULL;
 633	return __vmalloc_noprof(bytes, flags);
 634}
 635EXPORT_SYMBOL(__vmalloc_array_noprof);
 636
 637/**
 638 * vmalloc_array - allocate memory for a virtually contiguous array.
 639 * @n: number of elements.
 640 * @size: element size.
 641 */
 642void *vmalloc_array_noprof(size_t n, size_t size)
 643{
 644	return __vmalloc_array_noprof(n, size, GFP_KERNEL);
 645}
 646EXPORT_SYMBOL(vmalloc_array_noprof);
 647
 648/**
 649 * __vcalloc - allocate and zero memory for a virtually contiguous array.
 650 * @n: number of elements.
 651 * @size: element size.
 652 * @flags: the type of memory to allocate (see kmalloc).
 653 */
 654void *__vcalloc_noprof(size_t n, size_t size, gfp_t flags)
 655{
 656	return __vmalloc_array_noprof(n, size, flags | __GFP_ZERO);
 657}
 658EXPORT_SYMBOL(__vcalloc_noprof);
 659
 660/**
 661 * vcalloc - allocate and zero memory for a virtually contiguous array.
 662 * @n: number of elements.
 663 * @size: element size.
 664 */
 665void *vcalloc_noprof(size_t n, size_t size)
 666{
 667	return __vmalloc_array_noprof(n, size, GFP_KERNEL | __GFP_ZERO);
 668}
 669EXPORT_SYMBOL(vcalloc_noprof);
 670
 671struct anon_vma *folio_anon_vma(const struct folio *folio)
 672{
 673	unsigned long mapping = (unsigned long)folio->mapping;
 674
 675	if ((mapping & FOLIO_MAPPING_FLAGS) != FOLIO_MAPPING_ANON)
 676		return NULL;
 677	return (void *)(mapping - FOLIO_MAPPING_ANON);
 678}
 679
 680/**
 681 * folio_mapping - Find the mapping where this folio is stored.
 682 * @folio: The folio.
 683 *
 684 * For folios which are in the page cache, return the mapping that this
 685 * page belongs to.  Folios in the swap cache return the swap mapping
 686 * this page is stored in (which is different from the mapping for the
 687 * swap file or swap device where the data is stored).
 688 *
 689 * You can call this for folios which aren't in the swap cache or page
 690 * cache and it will return NULL.
 691 */
 692struct address_space *folio_mapping(const struct folio *folio)
 693{
 694	struct address_space *mapping;
 695
 696	/* This happens if someone calls flush_dcache_page on slab page */
 697	if (unlikely(folio_test_slab(folio)))
 698		return NULL;
 699
 700	if (unlikely(folio_test_swapcache(folio)))
 701		return swap_address_space(folio->swap);
 702
 703	mapping = folio->mapping;
 704	if ((unsigned long)mapping & FOLIO_MAPPING_FLAGS)
 705		return NULL;
 706
 707	return mapping;
 708}
 709EXPORT_SYMBOL(folio_mapping);
 710
 711/**
 712 * folio_copy - Copy the contents of one folio to another.
 713 * @dst: Folio to copy to.
 714 * @src: Folio to copy from.
 715 *
 716 * The bytes in the folio represented by @src are copied to @dst.
 717 * Assumes the caller has validated that @dst is at least as large as @src.
 718 * Can be called in atomic context for order-0 folios, but if the folio is
 719 * larger, it may sleep.
 720 */
 721void folio_copy(struct folio *dst, struct folio *src)
 722{
 723	long i = 0;
 724	long nr = folio_nr_pages(src);
 725
 726	for (;;) {
 727		copy_highpage(folio_page(dst, i), folio_page(src, i));
 728		if (++i == nr)
 729			break;
 730		cond_resched();
 731	}
 732}
 733EXPORT_SYMBOL(folio_copy);
 734
 735int folio_mc_copy(struct folio *dst, struct folio *src)
 736{
 737	long nr = folio_nr_pages(src);
 738	long i = 0;
 739
 740	for (;;) {
 741		if (copy_mc_highpage(folio_page(dst, i), folio_page(src, i)))
 742			return -EHWPOISON;
 743		if (++i == nr)
 744			break;
 745		cond_resched();
 746	}
 747
 748	return 0;
 749}
 750EXPORT_SYMBOL(folio_mc_copy);
 751
 752int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS;
 753static int sysctl_overcommit_ratio __read_mostly = 50;
 754static unsigned long sysctl_overcommit_kbytes __read_mostly;
 755int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
 756unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */
 757unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */
 758
 759#ifdef CONFIG_SYSCTL
 760
 761static int overcommit_ratio_handler(const struct ctl_table *table, int write,
 762				void *buffer, size_t *lenp, loff_t *ppos)
 763{
 764	int ret;
 765
 766	ret = proc_dointvec(table, write, buffer, lenp, ppos);
 767	if (ret == 0 && write)
 768		sysctl_overcommit_kbytes = 0;
 769	return ret;
 770}
 771
 772static void sync_overcommit_as(struct work_struct *dummy)
 773{
 774	percpu_counter_sync(&vm_committed_as);
 775}
 776
 777static int overcommit_policy_handler(const struct ctl_table *table, int write,
 778				void *buffer, size_t *lenp, loff_t *ppos)
 779{
 780	struct ctl_table t;
 781	int new_policy = -1;
 782	int ret;
 783
 784	/*
 785	 * The deviation of sync_overcommit_as could be big with loose policy
 786	 * like OVERCOMMIT_ALWAYS/OVERCOMMIT_GUESS. When changing policy to
 787	 * strict OVERCOMMIT_NEVER, we need to reduce the deviation to comply
 788	 * with the strict "NEVER", and to avoid possible race condition (even
 789	 * though user usually won't too frequently do the switching to policy
 790	 * OVERCOMMIT_NEVER), the switch is done in the following order:
 791	 *	1. changing the batch
 792	 *	2. sync percpu count on each CPU
 793	 *	3. switch the policy
 794	 */
 795	if (write) {
 796		t = *table;
 797		t.data = &new_policy;
 798		ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
 799		if (ret || new_policy == -1)
 800			return ret;
 801
 802		mm_compute_batch(new_policy);
 803		if (new_policy == OVERCOMMIT_NEVER)
 804			schedule_on_each_cpu(sync_overcommit_as);
 805		sysctl_overcommit_memory = new_policy;
 806	} else {
 807		ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 808	}
 809
 810	return ret;
 811}
 812
 813static int overcommit_kbytes_handler(const struct ctl_table *table, int write,
 814				void *buffer, size_t *lenp, loff_t *ppos)
 815{
 816	int ret;
 817
 818	ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
 819	if (ret == 0 && write)
 820		sysctl_overcommit_ratio = 0;
 821	return ret;
 822}
 823
 824static const struct ctl_table util_sysctl_table[] = {
 825	{
 826		.procname	= "overcommit_memory",
 827		.data		= &sysctl_overcommit_memory,
 828		.maxlen		= sizeof(sysctl_overcommit_memory),
 829		.mode		= 0644,
 830		.proc_handler	= overcommit_policy_handler,
 831		.extra1		= SYSCTL_ZERO,
 832		.extra2		= SYSCTL_TWO,
 833	},
 834	{
 835		.procname	= "overcommit_ratio",
 836		.data		= &sysctl_overcommit_ratio,
 837		.maxlen		= sizeof(sysctl_overcommit_ratio),
 838		.mode		= 0644,
 839		.proc_handler	= overcommit_ratio_handler,
 840	},
 841	{
 842		.procname	= "overcommit_kbytes",
 843		.data		= &sysctl_overcommit_kbytes,
 844		.maxlen		= sizeof(sysctl_overcommit_kbytes),
 845		.mode		= 0644,
 846		.proc_handler	= overcommit_kbytes_handler,
 847	},
 848	{
 849		.procname	= "user_reserve_kbytes",
 850		.data		= &sysctl_user_reserve_kbytes,
 851		.maxlen		= sizeof(sysctl_user_reserve_kbytes),
 852		.mode		= 0644,
 853		.proc_handler	= proc_doulongvec_minmax,
 854	},
 855	{
 856		.procname	= "admin_reserve_kbytes",
 857		.data		= &sysctl_admin_reserve_kbytes,
 858		.maxlen		= sizeof(sysctl_admin_reserve_kbytes),
 859		.mode		= 0644,
 860		.proc_handler	= proc_doulongvec_minmax,
 861	},
 862};
 863
 864static int __init init_vm_util_sysctls(void)
 865{
 866	register_sysctl_init("vm", util_sysctl_table);
 867	return 0;
 868}
 869subsys_initcall(init_vm_util_sysctls);
 870#endif /* CONFIG_SYSCTL */
 871
 872/*
 873 * Committed memory limit enforced when OVERCOMMIT_NEVER policy is used
 874 */
 875unsigned long vm_commit_limit(void)
 876{
 877	unsigned long allowed;
 878
 879	if (sysctl_overcommit_kbytes)
 880		allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10);
 881	else
 882		allowed = ((totalram_pages() - hugetlb_total_pages())
 883			   * sysctl_overcommit_ratio / 100);
 884	allowed += total_swap_pages;
 885
 886	return allowed;
 887}
 888
 889/*
 890 * Make sure vm_committed_as in one cacheline and not cacheline shared with
 891 * other variables. It can be updated by several CPUs frequently.
 892 */
 893struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
 894
 895/*
 896 * The global memory commitment made in the system can be a metric
 897 * that can be used to drive ballooning decisions when Linux is hosted
 898 * as a guest. On Hyper-V, the host implements a policy engine for dynamically
 899 * balancing memory across competing virtual machines that are hosted.
 900 * Several metrics drive this policy engine including the guest reported
 901 * memory commitment.
 902 *
 903 * The time cost of this is very low for small platforms, and for big
 904 * platform like a 2S/36C/72T Skylake server, in worst case where
 905 * vm_committed_as's spinlock is under severe contention, the time cost
 906 * could be about 30~40 microseconds.
 907 */
 908unsigned long vm_memory_committed(void)
 909{
 910	return percpu_counter_sum_positive(&vm_committed_as);
 911}
 912EXPORT_SYMBOL_GPL(vm_memory_committed);
 913
 914/*
 915 * Check that a process has enough memory to allocate a new virtual
 916 * mapping. 0 means there is enough memory for the allocation to
 917 * succeed and -ENOMEM implies there is not.
 918 *
 919 * We currently support three overcommit policies, which are set via the
 920 * vm.overcommit_memory sysctl.  See Documentation/mm/overcommit-accounting.rst
 921 *
 922 * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
 923 * Additional code 2002 Jul 20 by Robert Love.
 924 *
 925 * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
 926 *
 927 * Note this is a helper function intended to be used by LSMs which
 928 * wish to use this logic.
 929 */
 930int __vm_enough_memory(const struct mm_struct *mm, long pages, int cap_sys_admin)
 931{
 932	long allowed;
 933	unsigned long bytes_failed;
 934
 935	vm_acct_memory(pages);
 936
 937	/*
 938	 * Sometimes we want to use more memory than we have
 939	 */
 940	if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
 941		return 0;
 942
 943	if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
 944		if (pages > totalram_pages() + total_swap_pages)
 945			goto error;
 946		return 0;
 947	}
 948
 949	allowed = vm_commit_limit();
 950	/*
 951	 * Reserve some for root
 952	 */
 953	if (!cap_sys_admin)
 954		allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
 955
 956	/*
 957	 * Don't let a single process grow so big a user can't recover
 958	 */
 959	if (mm) {
 960		long reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10);
 961
 962		allowed -= min_t(long, mm->total_vm / 32, reserve);
 963	}
 964
 965	if (percpu_counter_read_positive(&vm_committed_as) < allowed)
 966		return 0;
 967error:
 968	bytes_failed = pages << PAGE_SHIFT;
 969	pr_warn_ratelimited("%s: pid: %d, comm: %s, bytes: %lu not enough memory for the allocation\n",
 970			    __func__, current->pid, current->comm, bytes_failed);
 971	vm_unacct_memory(pages);
 972
 973	return -ENOMEM;
 974}
 975
 976/**
 977 * get_cmdline() - copy the cmdline value to a buffer.
 978 * @task:     the task whose cmdline value to copy.
 979 * @buffer:   the buffer to copy to.
 980 * @buflen:   the length of the buffer. Larger cmdline values are truncated
 981 *            to this length.
 982 *
 983 * Return: the size of the cmdline field copied. Note that the copy does
 984 * not guarantee an ending NULL byte.
 985 */
 986int get_cmdline(struct task_struct *task, char *buffer, int buflen)
 987{
 988	int res = 0;
 989	unsigned int len;
 990	struct mm_struct *mm = get_task_mm(task);
 991	unsigned long arg_start, arg_end, env_start, env_end;
 992	if (!mm)
 993		goto out;
 994	if (!mm->arg_end)
 995		goto out_mm;	/* Shh! No looking before we're done */
 996
 997	spin_lock(&mm->arg_lock);
 998	arg_start = mm->arg_start;
 999	arg_end = mm->arg_end;
1000	env_start = mm->env_start;
1001	env_end = mm->env_end;
1002	spin_unlock(&mm->arg_lock);
1003
1004	len = arg_end - arg_start;
1005
1006	if (len > buflen)
1007		len = buflen;
1008
1009	res = access_process_vm(task, arg_start, buffer, len, FOLL_FORCE);
1010
1011	/*
1012	 * If the nul at the end of args has been overwritten, then
1013	 * assume application is using setproctitle(3).
1014	 */
1015	if (res > 0 && buffer[res-1] != '\0' && len < buflen) {
1016		len = strnlen(buffer, res);
1017		if (len < res) {
1018			res = len;
1019		} else {
1020			len = env_end - env_start;
1021			if (len > buflen - res)
1022				len = buflen - res;
1023			res += access_process_vm(task, env_start,
1024						 buffer+res, len,
1025						 FOLL_FORCE);
1026			res = strnlen(buffer, res);
1027		}
1028	}
1029out_mm:
1030	mmput(mm);
1031out:
1032	return res;
1033}
1034
1035int __weak memcmp_pages(struct page *page1, struct page *page2)
1036{
1037	char *addr1, *addr2;
1038	int ret;
1039
1040	addr1 = kmap_local_page(page1);
1041	addr2 = kmap_local_page(page2);
1042	ret = memcmp(addr1, addr2, PAGE_SIZE);
1043	kunmap_local(addr2);
1044	kunmap_local(addr1);
1045	return ret;
1046}
1047
1048#ifdef CONFIG_PRINTK
1049/**
1050 * mem_dump_obj - Print available provenance information
1051 * @object: object for which to find provenance information.
1052 *
1053 * This function uses pr_cont(), so that the caller is expected to have
1054 * printed out whatever preamble is appropriate.  The provenance information
1055 * depends on the type of object and on how much debugging is enabled.
1056 * For example, for a slab-cache object, the slab name is printed, and,
1057 * if available, the return address and stack trace from the allocation
1058 * and last free path of that object.
1059 */
1060void mem_dump_obj(void *object)
1061{
1062	const char *type;
1063
1064	if (kmem_dump_obj(object))
1065		return;
1066
1067	if (vmalloc_dump_obj(object))
1068		return;
1069
1070	if (is_vmalloc_addr(object))
1071		type = "vmalloc memory";
1072	else if (virt_addr_valid(object))
1073		type = "non-slab/vmalloc memory";
1074	else if (object == NULL)
1075		type = "NULL pointer";
1076	else if (object == ZERO_SIZE_PTR)
1077		type = "zero-size pointer";
1078	else
1079		type = "non-paged memory";
1080
1081	pr_cont(" %s\n", type);
1082}
1083EXPORT_SYMBOL_GPL(mem_dump_obj);
1084#endif
1085
1086/*
1087 * A driver might set a page logically offline -- PageOffline() -- and
1088 * turn the page inaccessible in the hypervisor; after that, access to page
1089 * content can be fatal.
1090 *
1091 * Some special PFN walkers -- i.e., /proc/kcore -- read content of random
1092 * pages after checking PageOffline(); however, these PFN walkers can race
1093 * with drivers that set PageOffline().
1094 *
1095 * page_offline_freeze()/page_offline_thaw() allows for a subsystem to
1096 * synchronize with such drivers, achieving that a page cannot be set
1097 * PageOffline() while frozen.
1098 *
1099 * page_offline_begin()/page_offline_end() is used by drivers that care about
1100 * such races when setting a page PageOffline().
1101 */
1102static DECLARE_RWSEM(page_offline_rwsem);
1103
1104void page_offline_freeze(void)
1105{
1106	down_read(&page_offline_rwsem);
1107}
1108
1109void page_offline_thaw(void)
1110{
1111	up_read(&page_offline_rwsem);
1112}
1113
1114void page_offline_begin(void)
1115{
1116	down_write(&page_offline_rwsem);
1117}
1118EXPORT_SYMBOL(page_offline_begin);
1119
1120void page_offline_end(void)
1121{
1122	up_write(&page_offline_rwsem);
1123}
1124EXPORT_SYMBOL(page_offline_end);
1125
1126#ifndef flush_dcache_folio
1127void flush_dcache_folio(struct folio *folio)
1128{
1129	long i, nr = folio_nr_pages(folio);
1130
1131	for (i = 0; i < nr; i++)
1132		flush_dcache_page(folio_page(folio, i));
1133}
1134EXPORT_SYMBOL(flush_dcache_folio);
1135#endif
1136
1137/**
1138 * __compat_vma_mmap() - See description for compat_vma_mmap()
1139 * for details. This is the same operation, only with a specific file operations
1140 * struct which may or may not be the same as vma->vm_file->f_op.
1141 * @f_op: The file operations whose .mmap_prepare() hook is specified.
1142 * @file: The file which backs or will back the mapping.
1143 * @vma: The VMA to apply the .mmap_prepare() hook to.
1144 * Returns: 0 on success or error.
1145 */
1146int __compat_vma_mmap(const struct file_operations *f_op,
1147		struct file *file, struct vm_area_struct *vma)
1148{
1149	struct vm_area_desc desc = {
1150		.mm = vma->vm_mm,
1151		.file = file,
1152		.start = vma->vm_start,
1153		.end = vma->vm_end,
1154
1155		.pgoff = vma->vm_pgoff,
1156		.vm_file = vma->vm_file,
1157		.vm_flags = vma->vm_flags,
1158		.page_prot = vma->vm_page_prot,
1159
1160		.action.type = MMAP_NOTHING, /* Default */
1161	};
1162	int err;
1163
1164	err = f_op->mmap_prepare(&desc);
1165	if (err)
1166		return err;
1167
1168	mmap_action_prepare(&desc.action, &desc);
1169	set_vma_from_desc(vma, &desc);
1170	return mmap_action_complete(&desc.action, vma);
1171}
1172EXPORT_SYMBOL(__compat_vma_mmap);
1173
1174/**
1175 * compat_vma_mmap() - Apply the file's .mmap_prepare() hook to an
1176 * existing VMA and execute any requested actions.
1177 * @file: The file which possesss an f_op->mmap_prepare() hook.
1178 * @vma: The VMA to apply the .mmap_prepare() hook to.
1179 *
1180 * Ordinarily, .mmap_prepare() is invoked directly upon mmap(). However, certain
1181 * stacked filesystems invoke a nested mmap hook of an underlying file.
1182 *
1183 * Until all filesystems are converted to use .mmap_prepare(), we must be
1184 * conservative and continue to invoke these stacked filesystems using the
1185 * deprecated .mmap() hook.
1186 *
1187 * However we have a problem if the underlying file system possesses an
1188 * .mmap_prepare() hook, as we are in a different context when we invoke the
1189 * .mmap() hook, already having a VMA to deal with.
1190 *
1191 * compat_vma_mmap() is a compatibility function that takes VMA state,
1192 * establishes a struct vm_area_desc descriptor, passes to the underlying
1193 * .mmap_prepare() hook and applies any changes performed by it.
1194 *
1195 * Once the conversion of filesystems is complete this function will no longer
1196 * be required and will be removed.
1197 *
1198 * Returns: 0 on success or error.
1199 */
1200int compat_vma_mmap(struct file *file, struct vm_area_struct *vma)
1201{
1202	return __compat_vma_mmap(file->f_op, file, vma);
1203}
1204EXPORT_SYMBOL(compat_vma_mmap);
1205
1206static void set_ps_flags(struct page_snapshot *ps, const struct folio *folio,
1207			 const struct page *page)
1208{
1209	/*
1210	 * Only the first page of a high-order buddy page has PageBuddy() set.
1211	 * So we have to check manually whether this page is part of a high-
1212	 * order buddy page.
1213	 */
1214	if (PageBuddy(page))
1215		ps->flags |= PAGE_SNAPSHOT_PG_BUDDY;
1216	else if (page_count(page) == 0 && is_free_buddy_page(page))
1217		ps->flags |= PAGE_SNAPSHOT_PG_BUDDY;
1218
1219	if (folio_test_idle(folio))
1220		ps->flags |= PAGE_SNAPSHOT_PG_IDLE;
1221}
1222
1223/**
1224 * snapshot_page() - Create a snapshot of a struct page
1225 * @ps: Pointer to a struct page_snapshot to store the page snapshot
1226 * @page: The page to snapshot
1227 *
1228 * Create a snapshot of the page and store both its struct page and struct
1229 * folio representations in @ps.
1230 *
1231 * A snapshot is marked as "faithful" if the compound state of @page was
1232 * stable and allowed safe reconstruction of the folio representation. In
1233 * rare cases where this is not possible (e.g. due to folio splitting),
1234 * snapshot_page() falls back to treating @page as a single page and the
1235 * snapshot is marked as "unfaithful". The snapshot_page_is_faithful()
1236 * helper can be used to check for this condition.
1237 */
1238void snapshot_page(struct page_snapshot *ps, const struct page *page)
1239{
1240	unsigned long head, nr_pages = 1;
1241	struct folio *foliop;
1242	int loops = 5;
1243
1244	ps->pfn = page_to_pfn(page);
1245	ps->flags = PAGE_SNAPSHOT_FAITHFUL;
1246
1247again:
1248	memset(&ps->folio_snapshot, 0, sizeof(struct folio));
1249	memcpy(&ps->page_snapshot, page, sizeof(*page));
1250	head = ps->page_snapshot.compound_head;
1251	if ((head & 1) == 0) {
1252		ps->idx = 0;
1253		foliop = (struct folio *)&ps->page_snapshot;
1254		if (!folio_test_large(foliop)) {
1255			set_ps_flags(ps, page_folio(page), page);
1256			memcpy(&ps->folio_snapshot, foliop,
1257			       sizeof(struct page));
1258			return;
1259		}
1260		foliop = (struct folio *)page;
1261	} else {
1262		foliop = (struct folio *)(head - 1);
1263		ps->idx = folio_page_idx(foliop, page);
1264	}
1265
1266	if (ps->idx < MAX_FOLIO_NR_PAGES) {
1267		memcpy(&ps->folio_snapshot, foliop, 2 * sizeof(struct page));
1268		nr_pages = folio_nr_pages(&ps->folio_snapshot);
1269		if (nr_pages > 1)
1270			memcpy(&ps->folio_snapshot.__page_2, &foliop->__page_2,
1271			       sizeof(struct page));
1272		set_ps_flags(ps, foliop, page);
1273	}
1274
1275	if (ps->idx > nr_pages) {
1276		if (loops-- > 0)
1277			goto again;
1278		clear_compound_head(&ps->page_snapshot);
1279		foliop = (struct folio *)&ps->page_snapshot;
1280		memcpy(&ps->folio_snapshot, foliop, sizeof(struct page));
1281		ps->flags = 0;
1282		ps->idx = 0;
1283	}
1284}
1285
1286static int mmap_action_finish(struct mmap_action *action,
1287		const struct vm_area_struct *vma, int err)
1288{
1289	/*
1290	 * If an error occurs, unmap the VMA altogether and return an error. We
1291	 * only clear the newly allocated VMA, since this function is only
1292	 * invoked if we do NOT merge, so we only clean up the VMA we created.
1293	 */
1294	if (err) {
1295		const size_t len = vma_pages(vma) << PAGE_SHIFT;
1296
1297		do_munmap(current->mm, vma->vm_start, len, NULL);
1298
1299		if (action->error_hook) {
1300			/* We may want to filter the error. */
1301			err = action->error_hook(err);
1302
1303			/* The caller should not clear the error. */
1304			VM_WARN_ON_ONCE(!err);
1305		}
1306		return err;
1307	}
1308
1309	if (action->success_hook)
1310		return action->success_hook(vma);
1311
1312	return 0;
1313}
1314
1315#ifdef CONFIG_MMU
1316/**
1317 * mmap_action_prepare - Perform preparatory setup for an VMA descriptor
1318 * action which need to be performed.
1319 * @desc: The VMA descriptor to prepare for @action.
1320 * @action: The action to perform.
1321 */
1322void mmap_action_prepare(struct mmap_action *action,
1323			 struct vm_area_desc *desc)
1324{
1325	switch (action->type) {
1326	case MMAP_NOTHING:
1327		break;
1328	case MMAP_REMAP_PFN:
1329		remap_pfn_range_prepare(desc, action->remap.start_pfn);
1330		break;
1331	case MMAP_IO_REMAP_PFN:
1332		io_remap_pfn_range_prepare(desc, action->remap.start_pfn,
1333					   action->remap.size);
1334		break;
1335	}
1336}
1337EXPORT_SYMBOL(mmap_action_prepare);
1338
1339/**
1340 * mmap_action_complete - Execute VMA descriptor action.
1341 * @action: The action to perform.
1342 * @vma: The VMA to perform the action upon.
1343 *
1344 * Similar to mmap_action_prepare().
1345 *
1346 * Return: 0 on success, or error, at which point the VMA will be unmapped.
1347 */
1348int mmap_action_complete(struct mmap_action *action,
1349			 struct vm_area_struct *vma)
1350{
1351	int err = 0;
1352
1353	switch (action->type) {
1354	case MMAP_NOTHING:
1355		break;
1356	case MMAP_REMAP_PFN:
1357		err = remap_pfn_range_complete(vma, action->remap.start,
1358				action->remap.start_pfn, action->remap.size,
1359				action->remap.pgprot);
1360		break;
1361	case MMAP_IO_REMAP_PFN:
1362		err = io_remap_pfn_range_complete(vma, action->remap.start,
1363				action->remap.start_pfn, action->remap.size,
1364				action->remap.pgprot);
1365		break;
1366	}
1367
1368	return mmap_action_finish(action, vma, err);
1369}
1370EXPORT_SYMBOL(mmap_action_complete);
1371#else
1372void mmap_action_prepare(struct mmap_action *action,
1373			struct vm_area_desc *desc)
1374{
1375	switch (action->type) {
1376	case MMAP_NOTHING:
1377		break;
1378	case MMAP_REMAP_PFN:
1379	case MMAP_IO_REMAP_PFN:
1380		WARN_ON_ONCE(1); /* nommu cannot handle these. */
1381		break;
1382	}
1383}
1384EXPORT_SYMBOL(mmap_action_prepare);
1385
1386int mmap_action_complete(struct mmap_action *action,
1387			struct vm_area_struct *vma)
1388{
1389	int err = 0;
1390
1391	switch (action->type) {
1392	case MMAP_NOTHING:
1393		break;
1394	case MMAP_REMAP_PFN:
1395	case MMAP_IO_REMAP_PFN:
1396		WARN_ON_ONCE(1); /* nommu cannot handle this. */
1397
1398		err = -EINVAL;
1399		break;
1400	}
1401
1402	return mmap_action_finish(action, vma, err);
1403}
1404EXPORT_SYMBOL(mmap_action_complete);
1405#endif
1406
1407#ifdef CONFIG_MMU
1408/**
1409 * folio_pte_batch - detect a PTE batch for a large folio
1410 * @folio: The large folio to detect a PTE batch for.
1411 * @ptep: Page table pointer for the first entry.
1412 * @pte: Page table entry for the first page.
1413 * @max_nr: The maximum number of table entries to consider.
1414 *
1415 * This is a simplified variant of folio_pte_batch_flags().
1416 *
1417 * Detect a PTE batch: consecutive (present) PTEs that map consecutive
1418 * pages of the same large folio in a single VMA and a single page table.
1419 *
1420 * All PTEs inside a PTE batch have the same PTE bits set, excluding the PFN,
1421 * the accessed bit, writable bit, dirt-bit and soft-dirty bit.
1422 *
1423 * ptep must map any page of the folio. max_nr must be at least one and
1424 * must be limited by the caller so scanning cannot exceed a single VMA and
1425 * a single page table.
1426 *
1427 * Return: the number of table entries in the batch.
1428 */
1429unsigned int folio_pte_batch(struct folio *folio, pte_t *ptep, pte_t pte,
1430		unsigned int max_nr)
1431{
1432	return folio_pte_batch_flags(folio, NULL, ptep, &pte, max_nr, 0);
1433}
1434#endif /* CONFIG_MMU */
1435
1436#if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
1437/**
1438 * page_range_contiguous - test whether the page range is contiguous
1439 * @page: the start of the page range.
1440 * @nr_pages: the number of pages in the range.
1441 *
1442 * Test whether the page range is contiguous, such that they can be iterated
1443 * naively, corresponding to iterating a contiguous PFN range.
1444 *
1445 * This function should primarily only be used for debug checks, or when
1446 * working with page ranges that are not naturally contiguous (e.g., pages
1447 * within a folio are).
1448 *
1449 * Returns true if contiguous, otherwise false.
1450 */
1451bool page_range_contiguous(const struct page *page, unsigned long nr_pages)
1452{
1453	const unsigned long start_pfn = page_to_pfn(page);
1454	const unsigned long end_pfn = start_pfn + nr_pages;
1455	unsigned long pfn;
1456
1457	/*
1458	 * The memmap is allocated per memory section, so no need to check
1459	 * within the first section. However, we need to check each other
1460	 * spanned memory section once, making sure the first page in a
1461	 * section could similarly be reached by just iterating pages.
1462	 */
1463	for (pfn = ALIGN(start_pfn, PAGES_PER_SECTION);
1464	     pfn < end_pfn; pfn += PAGES_PER_SECTION)
1465		if (unlikely(page + (pfn - start_pfn) != pfn_to_page(pfn)))
1466			return false;
1467	return true;
1468}
1469EXPORT_SYMBOL(page_range_contiguous);
1470#endif