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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/mman.h>
16#include <linux/hugetlb.h>
17#include <linux/vmalloc.h>
18#include <linux/userfaultfd_k.h>
19#include <linux/elf.h>
20#include <linux/elf-randomize.h>
21#include <linux/personality.h>
22#include <linux/random.h>
23#include <linux/processor.h>
24#include <linux/sizes.h>
25#include <linux/compat.h>
26
27#include <linux/uaccess.h>
28
29#include "internal.h"
30#include "swap.h"
31
32/**
33 * kfree_const - conditionally free memory
34 * @x: pointer to the memory
35 *
36 * Function calls kfree only if @x is not in .rodata section.
37 */
38void kfree_const(const void *x)
39{
40 if (!is_kernel_rodata((unsigned long)x))
41 kfree(x);
42}
43EXPORT_SYMBOL(kfree_const);
44
45/**
46 * kstrdup - allocate space for and copy an existing string
47 * @s: the string to duplicate
48 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
49 *
50 * Return: newly allocated copy of @s or %NULL in case of error
51 */
52char *kstrdup(const char *s, gfp_t gfp)
53{
54 size_t len;
55 char *buf;
56
57 if (!s)
58 return NULL;
59
60 len = strlen(s) + 1;
61 buf = kmalloc_track_caller(len, gfp);
62 if (buf)
63 memcpy(buf, s, len);
64 return buf;
65}
66EXPORT_SYMBOL(kstrdup);
67
68/**
69 * kstrdup_const - conditionally duplicate an existing const string
70 * @s: the string to duplicate
71 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
72 *
73 * Note: Strings allocated by kstrdup_const should be freed by kfree_const and
74 * must not be passed to krealloc().
75 *
76 * Return: source string if it is in .rodata section otherwise
77 * fallback to kstrdup.
78 */
79const char *kstrdup_const(const char *s, gfp_t gfp)
80{
81 if (is_kernel_rodata((unsigned long)s))
82 return s;
83
84 return kstrdup(s, gfp);
85}
86EXPORT_SYMBOL(kstrdup_const);
87
88/**
89 * kstrndup - allocate space for and copy an existing string
90 * @s: the string to duplicate
91 * @max: read at most @max chars from @s
92 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
93 *
94 * Note: Use kmemdup_nul() instead if the size is known exactly.
95 *
96 * Return: newly allocated copy of @s or %NULL in case of error
97 */
98char *kstrndup(const char *s, size_t max, gfp_t gfp)
99{
100 size_t len;
101 char *buf;
102
103 if (!s)
104 return NULL;
105
106 len = strnlen(s, max);
107 buf = kmalloc_track_caller(len+1, gfp);
108 if (buf) {
109 memcpy(buf, s, len);
110 buf[len] = '\0';
111 }
112 return buf;
113}
114EXPORT_SYMBOL(kstrndup);
115
116/**
117 * kmemdup - duplicate region of memory
118 *
119 * @src: memory region to duplicate
120 * @len: memory region length
121 * @gfp: GFP mask to use
122 *
123 * Return: newly allocated copy of @src or %NULL in case of error
124 */
125void *kmemdup(const void *src, size_t len, gfp_t gfp)
126{
127 void *p;
128
129 p = kmalloc_track_caller(len, gfp);
130 if (p)
131 memcpy(p, src, len);
132 return p;
133}
134EXPORT_SYMBOL(kmemdup);
135
136/**
137 * kmemdup_nul - Create a NUL-terminated string from unterminated data
138 * @s: The data to stringify
139 * @len: The size of the data
140 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
141 *
142 * Return: newly allocated copy of @s with NUL-termination or %NULL in
143 * case of error
144 */
145char *kmemdup_nul(const char *s, size_t len, gfp_t gfp)
146{
147 char *buf;
148
149 if (!s)
150 return NULL;
151
152 buf = kmalloc_track_caller(len + 1, gfp);
153 if (buf) {
154 memcpy(buf, s, len);
155 buf[len] = '\0';
156 }
157 return buf;
158}
159EXPORT_SYMBOL(kmemdup_nul);
160
161/**
162 * memdup_user - duplicate memory region from user space
163 *
164 * @src: source address in user space
165 * @len: number of bytes to copy
166 *
167 * Return: an ERR_PTR() on failure. Result is physically
168 * contiguous, to be freed by kfree().
169 */
170void *memdup_user(const void __user *src, size_t len)
171{
172 void *p;
173
174 p = kmalloc_track_caller(len, GFP_USER | __GFP_NOWARN);
175 if (!p)
176 return ERR_PTR(-ENOMEM);
177
178 if (copy_from_user(p, src, len)) {
179 kfree(p);
180 return ERR_PTR(-EFAULT);
181 }
182
183 return p;
184}
185EXPORT_SYMBOL(memdup_user);
186
187/**
188 * vmemdup_user - duplicate memory region from user space
189 *
190 * @src: source address in user space
191 * @len: number of bytes to copy
192 *
193 * Return: an ERR_PTR() on failure. Result may be not
194 * physically contiguous. Use kvfree() to free.
195 */
196void *vmemdup_user(const void __user *src, size_t len)
197{
198 void *p;
199
200 p = kvmalloc(len, GFP_USER);
201 if (!p)
202 return ERR_PTR(-ENOMEM);
203
204 if (copy_from_user(p, src, len)) {
205 kvfree(p);
206 return ERR_PTR(-EFAULT);
207 }
208
209 return p;
210}
211EXPORT_SYMBOL(vmemdup_user);
212
213/**
214 * strndup_user - duplicate an existing string from user space
215 * @s: The string to duplicate
216 * @n: Maximum number of bytes to copy, including the trailing NUL.
217 *
218 * Return: newly allocated copy of @s or an ERR_PTR() in case of error
219 */
220char *strndup_user(const char __user *s, long n)
221{
222 char *p;
223 long length;
224
225 length = strnlen_user(s, n);
226
227 if (!length)
228 return ERR_PTR(-EFAULT);
229
230 if (length > n)
231 return ERR_PTR(-EINVAL);
232
233 p = memdup_user(s, length);
234
235 if (IS_ERR(p))
236 return p;
237
238 p[length - 1] = '\0';
239
240 return p;
241}
242EXPORT_SYMBOL(strndup_user);
243
244/**
245 * memdup_user_nul - duplicate memory region from user space and NUL-terminate
246 *
247 * @src: source address in user space
248 * @len: number of bytes to copy
249 *
250 * Return: an ERR_PTR() on failure.
251 */
252void *memdup_user_nul(const void __user *src, size_t len)
253{
254 char *p;
255
256 /*
257 * Always use GFP_KERNEL, since copy_from_user() can sleep and
258 * cause pagefault, which makes it pointless to use GFP_NOFS
259 * or GFP_ATOMIC.
260 */
261 p = kmalloc_track_caller(len + 1, GFP_KERNEL);
262 if (!p)
263 return ERR_PTR(-ENOMEM);
264
265 if (copy_from_user(p, src, len)) {
266 kfree(p);
267 return ERR_PTR(-EFAULT);
268 }
269 p[len] = '\0';
270
271 return p;
272}
273EXPORT_SYMBOL(memdup_user_nul);
274
275/* Check if the vma is being used as a stack by this task */
276int vma_is_stack_for_current(struct vm_area_struct *vma)
277{
278 struct task_struct * __maybe_unused t = current;
279
280 return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
281}
282
283/*
284 * Change backing file, only valid to use during initial VMA setup.
285 */
286void vma_set_file(struct vm_area_struct *vma, struct file *file)
287{
288 /* Changing an anonymous vma with this is illegal */
289 get_file(file);
290 swap(vma->vm_file, file);
291 fput(file);
292}
293EXPORT_SYMBOL(vma_set_file);
294
295#ifndef STACK_RND_MASK
296#define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12)) /* 8MB of VA */
297#endif
298
299unsigned long randomize_stack_top(unsigned long stack_top)
300{
301 unsigned long random_variable = 0;
302
303 if (current->flags & PF_RANDOMIZE) {
304 random_variable = get_random_long();
305 random_variable &= STACK_RND_MASK;
306 random_variable <<= PAGE_SHIFT;
307 }
308#ifdef CONFIG_STACK_GROWSUP
309 return PAGE_ALIGN(stack_top) + random_variable;
310#else
311 return PAGE_ALIGN(stack_top) - random_variable;
312#endif
313}
314
315/**
316 * randomize_page - Generate a random, page aligned address
317 * @start: The smallest acceptable address the caller will take.
318 * @range: The size of the area, starting at @start, within which the
319 * random address must fall.
320 *
321 * If @start + @range would overflow, @range is capped.
322 *
323 * NOTE: Historical use of randomize_range, which this replaces, presumed that
324 * @start was already page aligned. We now align it regardless.
325 *
326 * Return: A page aligned address within [start, start + range). On error,
327 * @start is returned.
328 */
329unsigned long randomize_page(unsigned long start, unsigned long range)
330{
331 if (!PAGE_ALIGNED(start)) {
332 range -= PAGE_ALIGN(start) - start;
333 start = PAGE_ALIGN(start);
334 }
335
336 if (start > ULONG_MAX - range)
337 range = ULONG_MAX - start;
338
339 range >>= PAGE_SHIFT;
340
341 if (range == 0)
342 return start;
343
344 return start + (get_random_long() % range << PAGE_SHIFT);
345}
346
347#ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
348unsigned long __weak arch_randomize_brk(struct mm_struct *mm)
349{
350 /* Is the current task 32bit ? */
351 if (!IS_ENABLED(CONFIG_64BIT) || is_compat_task())
352 return randomize_page(mm->brk, SZ_32M);
353
354 return randomize_page(mm->brk, SZ_1G);
355}
356
357unsigned long arch_mmap_rnd(void)
358{
359 unsigned long rnd;
360
361#ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
362 if (is_compat_task())
363 rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
364 else
365#endif /* CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS */
366 rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
367
368 return rnd << PAGE_SHIFT;
369}
370
371static int mmap_is_legacy(struct rlimit *rlim_stack)
372{
373 if (current->personality & ADDR_COMPAT_LAYOUT)
374 return 1;
375
376 if (rlim_stack->rlim_cur == RLIM_INFINITY)
377 return 1;
378
379 return sysctl_legacy_va_layout;
380}
381
382/*
383 * Leave enough space between the mmap area and the stack to honour ulimit in
384 * the face of randomisation.
385 */
386#define MIN_GAP (SZ_128M)
387#define MAX_GAP (STACK_TOP / 6 * 5)
388
389static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack)
390{
391 unsigned long gap = rlim_stack->rlim_cur;
392 unsigned long pad = stack_guard_gap;
393
394 /* Account for stack randomization if necessary */
395 if (current->flags & PF_RANDOMIZE)
396 pad += (STACK_RND_MASK << PAGE_SHIFT);
397
398 /* Values close to RLIM_INFINITY can overflow. */
399 if (gap + pad > gap)
400 gap += pad;
401
402 if (gap < MIN_GAP)
403 gap = MIN_GAP;
404 else if (gap > MAX_GAP)
405 gap = MAX_GAP;
406
407 return PAGE_ALIGN(STACK_TOP - gap - rnd);
408}
409
410void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
411{
412 unsigned long random_factor = 0UL;
413
414 if (current->flags & PF_RANDOMIZE)
415 random_factor = arch_mmap_rnd();
416
417 if (mmap_is_legacy(rlim_stack)) {
418 mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
419 mm->get_unmapped_area = arch_get_unmapped_area;
420 } else {
421 mm->mmap_base = mmap_base(random_factor, rlim_stack);
422 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
423 }
424}
425#elif defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
426void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
427{
428 mm->mmap_base = TASK_UNMAPPED_BASE;
429 mm->get_unmapped_area = arch_get_unmapped_area;
430}
431#endif
432
433/**
434 * __account_locked_vm - account locked pages to an mm's locked_vm
435 * @mm: mm to account against
436 * @pages: number of pages to account
437 * @inc: %true if @pages should be considered positive, %false if not
438 * @task: task used to check RLIMIT_MEMLOCK
439 * @bypass_rlim: %true if checking RLIMIT_MEMLOCK should be skipped
440 *
441 * Assumes @task and @mm are valid (i.e. at least one reference on each), and
442 * that mmap_lock is held as writer.
443 *
444 * Return:
445 * * 0 on success
446 * * -ENOMEM if RLIMIT_MEMLOCK would be exceeded.
447 */
448int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc,
449 struct task_struct *task, bool bypass_rlim)
450{
451 unsigned long locked_vm, limit;
452 int ret = 0;
453
454 mmap_assert_write_locked(mm);
455
456 locked_vm = mm->locked_vm;
457 if (inc) {
458 if (!bypass_rlim) {
459 limit = task_rlimit(task, RLIMIT_MEMLOCK) >> PAGE_SHIFT;
460 if (locked_vm + pages > limit)
461 ret = -ENOMEM;
462 }
463 if (!ret)
464 mm->locked_vm = locked_vm + pages;
465 } else {
466 WARN_ON_ONCE(pages > locked_vm);
467 mm->locked_vm = locked_vm - pages;
468 }
469
470 pr_debug("%s: [%d] caller %ps %c%lu %lu/%lu%s\n", __func__, task->pid,
471 (void *)_RET_IP_, (inc) ? '+' : '-', pages << PAGE_SHIFT,
472 locked_vm << PAGE_SHIFT, task_rlimit(task, RLIMIT_MEMLOCK),
473 ret ? " - exceeded" : "");
474
475 return ret;
476}
477EXPORT_SYMBOL_GPL(__account_locked_vm);
478
479/**
480 * account_locked_vm - account locked pages to an mm's locked_vm
481 * @mm: mm to account against, may be NULL
482 * @pages: number of pages to account
483 * @inc: %true if @pages should be considered positive, %false if not
484 *
485 * Assumes a non-NULL @mm is valid (i.e. at least one reference on it).
486 *
487 * Return:
488 * * 0 on success, or if mm is NULL
489 * * -ENOMEM if RLIMIT_MEMLOCK would be exceeded.
490 */
491int account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc)
492{
493 int ret;
494
495 if (pages == 0 || !mm)
496 return 0;
497
498 mmap_write_lock(mm);
499 ret = __account_locked_vm(mm, pages, inc, current,
500 capable(CAP_IPC_LOCK));
501 mmap_write_unlock(mm);
502
503 return ret;
504}
505EXPORT_SYMBOL_GPL(account_locked_vm);
506
507unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
508 unsigned long len, unsigned long prot,
509 unsigned long flag, unsigned long pgoff)
510{
511 unsigned long ret;
512 struct mm_struct *mm = current->mm;
513 unsigned long populate;
514 LIST_HEAD(uf);
515
516 ret = security_mmap_file(file, prot, flag);
517 if (!ret) {
518 if (mmap_write_lock_killable(mm))
519 return -EINTR;
520 ret = do_mmap(file, addr, len, prot, flag, pgoff, &populate,
521 &uf);
522 mmap_write_unlock(mm);
523 userfaultfd_unmap_complete(mm, &uf);
524 if (populate)
525 mm_populate(ret, populate);
526 }
527 return ret;
528}
529
530unsigned long vm_mmap(struct file *file, unsigned long addr,
531 unsigned long len, unsigned long prot,
532 unsigned long flag, unsigned long offset)
533{
534 if (unlikely(offset + PAGE_ALIGN(len) < offset))
535 return -EINVAL;
536 if (unlikely(offset_in_page(offset)))
537 return -EINVAL;
538
539 return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
540}
541EXPORT_SYMBOL(vm_mmap);
542
543/**
544 * kvmalloc_node - attempt to allocate physically contiguous memory, but upon
545 * failure, fall back to non-contiguous (vmalloc) allocation.
546 * @size: size of the request.
547 * @flags: gfp mask for the allocation - must be compatible (superset) with GFP_KERNEL.
548 * @node: numa node to allocate from
549 *
550 * Uses kmalloc to get the memory but if the allocation fails then falls back
551 * to the vmalloc allocator. Use kvfree for freeing the memory.
552 *
553 * GFP_NOWAIT and GFP_ATOMIC are not supported, neither is the __GFP_NORETRY modifier.
554 * __GFP_RETRY_MAYFAIL is supported, and it should be used only if kmalloc is
555 * preferable to the vmalloc fallback, due to visible performance drawbacks.
556 *
557 * Return: pointer to the allocated memory of %NULL in case of failure
558 */
559void *kvmalloc_node(size_t size, gfp_t flags, int node)
560{
561 gfp_t kmalloc_flags = flags;
562 void *ret;
563
564 /*
565 * We want to attempt a large physically contiguous block first because
566 * it is less likely to fragment multiple larger blocks and therefore
567 * contribute to a long term fragmentation less than vmalloc fallback.
568 * However make sure that larger requests are not too disruptive - no
569 * OOM killer and no allocation failure warnings as we have a fallback.
570 */
571 if (size > PAGE_SIZE) {
572 kmalloc_flags |= __GFP_NOWARN;
573
574 if (!(kmalloc_flags & __GFP_RETRY_MAYFAIL))
575 kmalloc_flags |= __GFP_NORETRY;
576
577 /* nofail semantic is implemented by the vmalloc fallback */
578 kmalloc_flags &= ~__GFP_NOFAIL;
579 }
580
581 ret = kmalloc_node(size, kmalloc_flags, node);
582
583 /*
584 * It doesn't really make sense to fallback to vmalloc for sub page
585 * requests
586 */
587 if (ret || size <= PAGE_SIZE)
588 return ret;
589
590 /* non-sleeping allocations are not supported by vmalloc */
591 if (!gfpflags_allow_blocking(flags))
592 return NULL;
593
594 /* Don't even allow crazy sizes */
595 if (unlikely(size > INT_MAX)) {
596 WARN_ON_ONCE(!(flags & __GFP_NOWARN));
597 return NULL;
598 }
599
600 /*
601 * kvmalloc() can always use VM_ALLOW_HUGE_VMAP,
602 * since the callers already cannot assume anything
603 * about the resulting pointer, and cannot play
604 * protection games.
605 */
606 return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END,
607 flags, PAGE_KERNEL, VM_ALLOW_HUGE_VMAP,
608 node, __builtin_return_address(0));
609}
610EXPORT_SYMBOL(kvmalloc_node);
611
612/**
613 * kvfree() - Free memory.
614 * @addr: Pointer to allocated memory.
615 *
616 * kvfree frees memory allocated by any of vmalloc(), kmalloc() or kvmalloc().
617 * It is slightly more efficient to use kfree() or vfree() if you are certain
618 * that you know which one to use.
619 *
620 * Context: Either preemptible task context or not-NMI interrupt.
621 */
622void kvfree(const void *addr)
623{
624 if (is_vmalloc_addr(addr))
625 vfree(addr);
626 else
627 kfree(addr);
628}
629EXPORT_SYMBOL(kvfree);
630
631/**
632 * kvfree_sensitive - Free a data object containing sensitive information.
633 * @addr: address of the data object to be freed.
634 * @len: length of the data object.
635 *
636 * Use the special memzero_explicit() function to clear the content of a
637 * kvmalloc'ed object containing sensitive data to make sure that the
638 * compiler won't optimize out the data clearing.
639 */
640void kvfree_sensitive(const void *addr, size_t len)
641{
642 if (likely(!ZERO_OR_NULL_PTR(addr))) {
643 memzero_explicit((void *)addr, len);
644 kvfree(addr);
645 }
646}
647EXPORT_SYMBOL(kvfree_sensitive);
648
649void *kvrealloc(const void *p, size_t oldsize, size_t newsize, gfp_t flags)
650{
651 void *newp;
652
653 if (oldsize >= newsize)
654 return (void *)p;
655 newp = kvmalloc(newsize, flags);
656 if (!newp)
657 return NULL;
658 memcpy(newp, p, oldsize);
659 kvfree(p);
660 return newp;
661}
662EXPORT_SYMBOL(kvrealloc);
663
664/**
665 * __vmalloc_array - allocate memory for a virtually contiguous array.
666 * @n: number of elements.
667 * @size: element size.
668 * @flags: the type of memory to allocate (see kmalloc).
669 */
670void *__vmalloc_array(size_t n, size_t size, gfp_t flags)
671{
672 size_t bytes;
673
674 if (unlikely(check_mul_overflow(n, size, &bytes)))
675 return NULL;
676 return __vmalloc(bytes, flags);
677}
678EXPORT_SYMBOL(__vmalloc_array);
679
680/**
681 * vmalloc_array - allocate memory for a virtually contiguous array.
682 * @n: number of elements.
683 * @size: element size.
684 */
685void *vmalloc_array(size_t n, size_t size)
686{
687 return __vmalloc_array(n, size, GFP_KERNEL);
688}
689EXPORT_SYMBOL(vmalloc_array);
690
691/**
692 * __vcalloc - allocate and zero memory for a virtually contiguous array.
693 * @n: number of elements.
694 * @size: element size.
695 * @flags: the type of memory to allocate (see kmalloc).
696 */
697void *__vcalloc(size_t n, size_t size, gfp_t flags)
698{
699 return __vmalloc_array(n, size, flags | __GFP_ZERO);
700}
701EXPORT_SYMBOL(__vcalloc);
702
703/**
704 * vcalloc - allocate and zero memory for a virtually contiguous array.
705 * @n: number of elements.
706 * @size: element size.
707 */
708void *vcalloc(size_t n, size_t size)
709{
710 return __vmalloc_array(n, size, GFP_KERNEL | __GFP_ZERO);
711}
712EXPORT_SYMBOL(vcalloc);
713
714/* Neutral page->mapping pointer to address_space or anon_vma or other */
715void *page_rmapping(struct page *page)
716{
717 return folio_raw_mapping(page_folio(page));
718}
719
720struct anon_vma *folio_anon_vma(struct folio *folio)
721{
722 unsigned long mapping = (unsigned long)folio->mapping;
723
724 if ((mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
725 return NULL;
726 return (void *)(mapping - PAGE_MAPPING_ANON);
727}
728
729/**
730 * folio_mapping - Find the mapping where this folio is stored.
731 * @folio: The folio.
732 *
733 * For folios which are in the page cache, return the mapping that this
734 * page belongs to. Folios in the swap cache return the swap mapping
735 * this page is stored in (which is different from the mapping for the
736 * swap file or swap device where the data is stored).
737 *
738 * You can call this for folios which aren't in the swap cache or page
739 * cache and it will return NULL.
740 */
741struct address_space *folio_mapping(struct folio *folio)
742{
743 struct address_space *mapping;
744
745 /* This happens if someone calls flush_dcache_page on slab page */
746 if (unlikely(folio_test_slab(folio)))
747 return NULL;
748
749 if (unlikely(folio_test_swapcache(folio)))
750 return swap_address_space(folio_swap_entry(folio));
751
752 mapping = folio->mapping;
753 if ((unsigned long)mapping & PAGE_MAPPING_FLAGS)
754 return NULL;
755
756 return mapping;
757}
758EXPORT_SYMBOL(folio_mapping);
759
760/**
761 * folio_copy - Copy the contents of one folio to another.
762 * @dst: Folio to copy to.
763 * @src: Folio to copy from.
764 *
765 * The bytes in the folio represented by @src are copied to @dst.
766 * Assumes the caller has validated that @dst is at least as large as @src.
767 * Can be called in atomic context for order-0 folios, but if the folio is
768 * larger, it may sleep.
769 */
770void folio_copy(struct folio *dst, struct folio *src)
771{
772 long i = 0;
773 long nr = folio_nr_pages(src);
774
775 for (;;) {
776 copy_highpage(folio_page(dst, i), folio_page(src, i));
777 if (++i == nr)
778 break;
779 cond_resched();
780 }
781}
782
783int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS;
784int sysctl_overcommit_ratio __read_mostly = 50;
785unsigned long sysctl_overcommit_kbytes __read_mostly;
786int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
787unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */
788unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */
789
790int overcommit_ratio_handler(struct ctl_table *table, int write, void *buffer,
791 size_t *lenp, loff_t *ppos)
792{
793 int ret;
794
795 ret = proc_dointvec(table, write, buffer, lenp, ppos);
796 if (ret == 0 && write)
797 sysctl_overcommit_kbytes = 0;
798 return ret;
799}
800
801static void sync_overcommit_as(struct work_struct *dummy)
802{
803 percpu_counter_sync(&vm_committed_as);
804}
805
806int overcommit_policy_handler(struct ctl_table *table, int write, void *buffer,
807 size_t *lenp, loff_t *ppos)
808{
809 struct ctl_table t;
810 int new_policy = -1;
811 int ret;
812
813 /*
814 * The deviation of sync_overcommit_as could be big with loose policy
815 * like OVERCOMMIT_ALWAYS/OVERCOMMIT_GUESS. When changing policy to
816 * strict OVERCOMMIT_NEVER, we need to reduce the deviation to comply
817 * with the strict "NEVER", and to avoid possible race condition (even
818 * though user usually won't too frequently do the switching to policy
819 * OVERCOMMIT_NEVER), the switch is done in the following order:
820 * 1. changing the batch
821 * 2. sync percpu count on each CPU
822 * 3. switch the policy
823 */
824 if (write) {
825 t = *table;
826 t.data = &new_policy;
827 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
828 if (ret || new_policy == -1)
829 return ret;
830
831 mm_compute_batch(new_policy);
832 if (new_policy == OVERCOMMIT_NEVER)
833 schedule_on_each_cpu(sync_overcommit_as);
834 sysctl_overcommit_memory = new_policy;
835 } else {
836 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
837 }
838
839 return ret;
840}
841
842int overcommit_kbytes_handler(struct ctl_table *table, int write, void *buffer,
843 size_t *lenp, loff_t *ppos)
844{
845 int ret;
846
847 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
848 if (ret == 0 && write)
849 sysctl_overcommit_ratio = 0;
850 return ret;
851}
852
853/*
854 * Committed memory limit enforced when OVERCOMMIT_NEVER policy is used
855 */
856unsigned long vm_commit_limit(void)
857{
858 unsigned long allowed;
859
860 if (sysctl_overcommit_kbytes)
861 allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10);
862 else
863 allowed = ((totalram_pages() - hugetlb_total_pages())
864 * sysctl_overcommit_ratio / 100);
865 allowed += total_swap_pages;
866
867 return allowed;
868}
869
870/*
871 * Make sure vm_committed_as in one cacheline and not cacheline shared with
872 * other variables. It can be updated by several CPUs frequently.
873 */
874struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
875
876/*
877 * The global memory commitment made in the system can be a metric
878 * that can be used to drive ballooning decisions when Linux is hosted
879 * as a guest. On Hyper-V, the host implements a policy engine for dynamically
880 * balancing memory across competing virtual machines that are hosted.
881 * Several metrics drive this policy engine including the guest reported
882 * memory commitment.
883 *
884 * The time cost of this is very low for small platforms, and for big
885 * platform like a 2S/36C/72T Skylake server, in worst case where
886 * vm_committed_as's spinlock is under severe contention, the time cost
887 * could be about 30~40 microseconds.
888 */
889unsigned long vm_memory_committed(void)
890{
891 return percpu_counter_sum_positive(&vm_committed_as);
892}
893EXPORT_SYMBOL_GPL(vm_memory_committed);
894
895/*
896 * Check that a process has enough memory to allocate a new virtual
897 * mapping. 0 means there is enough memory for the allocation to
898 * succeed and -ENOMEM implies there is not.
899 *
900 * We currently support three overcommit policies, which are set via the
901 * vm.overcommit_memory sysctl. See Documentation/mm/overcommit-accounting.rst
902 *
903 * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
904 * Additional code 2002 Jul 20 by Robert Love.
905 *
906 * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
907 *
908 * Note this is a helper function intended to be used by LSMs which
909 * wish to use this logic.
910 */
911int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
912{
913 long allowed;
914
915 vm_acct_memory(pages);
916
917 /*
918 * Sometimes we want to use more memory than we have
919 */
920 if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
921 return 0;
922
923 if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
924 if (pages > totalram_pages() + total_swap_pages)
925 goto error;
926 return 0;
927 }
928
929 allowed = vm_commit_limit();
930 /*
931 * Reserve some for root
932 */
933 if (!cap_sys_admin)
934 allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
935
936 /*
937 * Don't let a single process grow so big a user can't recover
938 */
939 if (mm) {
940 long reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10);
941
942 allowed -= min_t(long, mm->total_vm / 32, reserve);
943 }
944
945 if (percpu_counter_read_positive(&vm_committed_as) < allowed)
946 return 0;
947error:
948 pr_warn_ratelimited("%s: pid: %d, comm: %s, no enough memory for the allocation\n",
949 __func__, current->pid, current->comm);
950 vm_unacct_memory(pages);
951
952 return -ENOMEM;
953}
954
955/**
956 * get_cmdline() - copy the cmdline value to a buffer.
957 * @task: the task whose cmdline value to copy.
958 * @buffer: the buffer to copy to.
959 * @buflen: the length of the buffer. Larger cmdline values are truncated
960 * to this length.
961 *
962 * Return: the size of the cmdline field copied. Note that the copy does
963 * not guarantee an ending NULL byte.
964 */
965int get_cmdline(struct task_struct *task, char *buffer, int buflen)
966{
967 int res = 0;
968 unsigned int len;
969 struct mm_struct *mm = get_task_mm(task);
970 unsigned long arg_start, arg_end, env_start, env_end;
971 if (!mm)
972 goto out;
973 if (!mm->arg_end)
974 goto out_mm; /* Shh! No looking before we're done */
975
976 spin_lock(&mm->arg_lock);
977 arg_start = mm->arg_start;
978 arg_end = mm->arg_end;
979 env_start = mm->env_start;
980 env_end = mm->env_end;
981 spin_unlock(&mm->arg_lock);
982
983 len = arg_end - arg_start;
984
985 if (len > buflen)
986 len = buflen;
987
988 res = access_process_vm(task, arg_start, buffer, len, FOLL_FORCE);
989
990 /*
991 * If the nul at the end of args has been overwritten, then
992 * assume application is using setproctitle(3).
993 */
994 if (res > 0 && buffer[res-1] != '\0' && len < buflen) {
995 len = strnlen(buffer, res);
996 if (len < res) {
997 res = len;
998 } else {
999 len = env_end - env_start;
1000 if (len > buflen - res)
1001 len = buflen - res;
1002 res += access_process_vm(task, env_start,
1003 buffer+res, len,
1004 FOLL_FORCE);
1005 res = strnlen(buffer, res);
1006 }
1007 }
1008out_mm:
1009 mmput(mm);
1010out:
1011 return res;
1012}
1013
1014int __weak memcmp_pages(struct page *page1, struct page *page2)
1015{
1016 char *addr1, *addr2;
1017 int ret;
1018
1019 addr1 = kmap_atomic(page1);
1020 addr2 = kmap_atomic(page2);
1021 ret = memcmp(addr1, addr2, PAGE_SIZE);
1022 kunmap_atomic(addr2);
1023 kunmap_atomic(addr1);
1024 return ret;
1025}
1026
1027#ifdef CONFIG_PRINTK
1028/**
1029 * mem_dump_obj - Print available provenance information
1030 * @object: object for which to find provenance information.
1031 *
1032 * This function uses pr_cont(), so that the caller is expected to have
1033 * printed out whatever preamble is appropriate. The provenance information
1034 * depends on the type of object and on how much debugging is enabled.
1035 * For example, for a slab-cache object, the slab name is printed, and,
1036 * if available, the return address and stack trace from the allocation
1037 * and last free path of that object.
1038 */
1039void mem_dump_obj(void *object)
1040{
1041 const char *type;
1042
1043 if (kmem_valid_obj(object)) {
1044 kmem_dump_obj(object);
1045 return;
1046 }
1047
1048 if (vmalloc_dump_obj(object))
1049 return;
1050
1051 if (virt_addr_valid(object))
1052 type = "non-slab/vmalloc memory";
1053 else if (object == NULL)
1054 type = "NULL pointer";
1055 else if (object == ZERO_SIZE_PTR)
1056 type = "zero-size pointer";
1057 else
1058 type = "non-paged memory";
1059
1060 pr_cont(" %s\n", type);
1061}
1062EXPORT_SYMBOL_GPL(mem_dump_obj);
1063#endif
1064
1065/*
1066 * A driver might set a page logically offline -- PageOffline() -- and
1067 * turn the page inaccessible in the hypervisor; after that, access to page
1068 * content can be fatal.
1069 *
1070 * Some special PFN walkers -- i.e., /proc/kcore -- read content of random
1071 * pages after checking PageOffline(); however, these PFN walkers can race
1072 * with drivers that set PageOffline().
1073 *
1074 * page_offline_freeze()/page_offline_thaw() allows for a subsystem to
1075 * synchronize with such drivers, achieving that a page cannot be set
1076 * PageOffline() while frozen.
1077 *
1078 * page_offline_begin()/page_offline_end() is used by drivers that care about
1079 * such races when setting a page PageOffline().
1080 */
1081static DECLARE_RWSEM(page_offline_rwsem);
1082
1083void page_offline_freeze(void)
1084{
1085 down_read(&page_offline_rwsem);
1086}
1087
1088void page_offline_thaw(void)
1089{
1090 up_read(&page_offline_rwsem);
1091}
1092
1093void page_offline_begin(void)
1094{
1095 down_write(&page_offline_rwsem);
1096}
1097EXPORT_SYMBOL(page_offline_begin);
1098
1099void page_offline_end(void)
1100{
1101 up_write(&page_offline_rwsem);
1102}
1103EXPORT_SYMBOL(page_offline_end);
1104
1105#ifndef ARCH_IMPLEMENTS_FLUSH_DCACHE_FOLIO
1106void flush_dcache_folio(struct folio *folio)
1107{
1108 long i, nr = folio_nr_pages(folio);
1109
1110 for (i = 0; i < nr; i++)
1111 flush_dcache_page(folio_page(folio, i));
1112}
1113EXPORT_SYMBOL(flush_dcache_folio);
1114#endif
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/mman.h>
16#include <linux/hugetlb.h>
17#include <linux/vmalloc.h>
18#include <linux/userfaultfd_k.h>
19#include <linux/elf.h>
20#include <linux/elf-randomize.h>
21#include <linux/personality.h>
22#include <linux/random.h>
23#include <linux/processor.h>
24#include <linux/sizes.h>
25#include <linux/compat.h>
26
27#include <linux/uaccess.h>
28
29#include "internal.h"
30#include "swap.h"
31
32/**
33 * kfree_const - conditionally free memory
34 * @x: pointer to the memory
35 *
36 * Function calls kfree only if @x is not in .rodata section.
37 */
38void kfree_const(const void *x)
39{
40 if (!is_kernel_rodata((unsigned long)x))
41 kfree(x);
42}
43EXPORT_SYMBOL(kfree_const);
44
45/**
46 * kstrdup - allocate space for and copy an existing string
47 * @s: the string to duplicate
48 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
49 *
50 * Return: newly allocated copy of @s or %NULL in case of error
51 */
52noinline
53char *kstrdup(const char *s, gfp_t gfp)
54{
55 size_t len;
56 char *buf;
57
58 if (!s)
59 return NULL;
60
61 len = strlen(s) + 1;
62 buf = kmalloc_track_caller(len, gfp);
63 if (buf)
64 memcpy(buf, s, len);
65 return buf;
66}
67EXPORT_SYMBOL(kstrdup);
68
69/**
70 * kstrdup_const - conditionally duplicate an existing const string
71 * @s: the string to duplicate
72 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
73 *
74 * Note: Strings allocated by kstrdup_const should be freed by kfree_const and
75 * must not be passed to krealloc().
76 *
77 * Return: source string if it is in .rodata section otherwise
78 * fallback to kstrdup.
79 */
80const char *kstrdup_const(const char *s, gfp_t gfp)
81{
82 if (is_kernel_rodata((unsigned long)s))
83 return s;
84
85 return kstrdup(s, gfp);
86}
87EXPORT_SYMBOL(kstrdup_const);
88
89/**
90 * kstrndup - allocate space for and copy an existing string
91 * @s: the string to duplicate
92 * @max: read at most @max chars from @s
93 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
94 *
95 * Note: Use kmemdup_nul() instead if the size is known exactly.
96 *
97 * Return: newly allocated copy of @s or %NULL in case of error
98 */
99char *kstrndup(const char *s, size_t max, gfp_t gfp)
100{
101 size_t len;
102 char *buf;
103
104 if (!s)
105 return NULL;
106
107 len = strnlen(s, max);
108 buf = kmalloc_track_caller(len+1, gfp);
109 if (buf) {
110 memcpy(buf, s, len);
111 buf[len] = '\0';
112 }
113 return buf;
114}
115EXPORT_SYMBOL(kstrndup);
116
117/**
118 * kmemdup - duplicate region of memory
119 *
120 * @src: memory region to duplicate
121 * @len: memory region length
122 * @gfp: GFP mask to use
123 *
124 * Return: newly allocated copy of @src or %NULL in case of error,
125 * result is physically contiguous. Use kfree() to free.
126 */
127void *kmemdup(const void *src, size_t len, gfp_t gfp)
128{
129 void *p;
130
131 p = kmalloc_track_caller(len, gfp);
132 if (p)
133 memcpy(p, src, len);
134 return p;
135}
136EXPORT_SYMBOL(kmemdup);
137
138/**
139 * kmemdup_array - duplicate a given array.
140 *
141 * @src: array to duplicate.
142 * @element_size: size of each element of array.
143 * @count: number of elements to duplicate from array.
144 * @gfp: GFP mask to use.
145 *
146 * Return: duplicated array of @src or %NULL in case of error,
147 * result is physically contiguous. Use kfree() to free.
148 */
149void *kmemdup_array(const void *src, size_t element_size, size_t count, gfp_t gfp)
150{
151 return kmemdup(src, size_mul(element_size, count), gfp);
152}
153EXPORT_SYMBOL(kmemdup_array);
154
155/**
156 * kvmemdup - duplicate region of memory
157 *
158 * @src: memory region to duplicate
159 * @len: memory region length
160 * @gfp: GFP mask to use
161 *
162 * Return: newly allocated copy of @src or %NULL in case of error,
163 * result may be not physically contiguous. Use kvfree() to free.
164 */
165void *kvmemdup(const void *src, size_t len, gfp_t gfp)
166{
167 void *p;
168
169 p = kvmalloc(len, gfp);
170 if (p)
171 memcpy(p, src, len);
172 return p;
173}
174EXPORT_SYMBOL(kvmemdup);
175
176/**
177 * kmemdup_nul - Create a NUL-terminated string from unterminated data
178 * @s: The data to stringify
179 * @len: The size of the data
180 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
181 *
182 * Return: newly allocated copy of @s with NUL-termination or %NULL in
183 * case of error
184 */
185char *kmemdup_nul(const char *s, size_t len, gfp_t gfp)
186{
187 char *buf;
188
189 if (!s)
190 return NULL;
191
192 buf = kmalloc_track_caller(len + 1, gfp);
193 if (buf) {
194 memcpy(buf, s, len);
195 buf[len] = '\0';
196 }
197 return buf;
198}
199EXPORT_SYMBOL(kmemdup_nul);
200
201/**
202 * memdup_user - duplicate memory region from user space
203 *
204 * @src: source address in user space
205 * @len: number of bytes to copy
206 *
207 * Return: an ERR_PTR() on failure. Result is physically
208 * contiguous, to be freed by kfree().
209 */
210void *memdup_user(const void __user *src, size_t len)
211{
212 void *p;
213
214 p = kmalloc_track_caller(len, GFP_USER | __GFP_NOWARN);
215 if (!p)
216 return ERR_PTR(-ENOMEM);
217
218 if (copy_from_user(p, src, len)) {
219 kfree(p);
220 return ERR_PTR(-EFAULT);
221 }
222
223 return p;
224}
225EXPORT_SYMBOL(memdup_user);
226
227/**
228 * vmemdup_user - duplicate memory region from user space
229 *
230 * @src: source address in user space
231 * @len: number of bytes to copy
232 *
233 * Return: an ERR_PTR() on failure. Result may be not
234 * physically contiguous. Use kvfree() to free.
235 */
236void *vmemdup_user(const void __user *src, size_t len)
237{
238 void *p;
239
240 p = kvmalloc(len, GFP_USER);
241 if (!p)
242 return ERR_PTR(-ENOMEM);
243
244 if (copy_from_user(p, src, len)) {
245 kvfree(p);
246 return ERR_PTR(-EFAULT);
247 }
248
249 return p;
250}
251EXPORT_SYMBOL(vmemdup_user);
252
253/**
254 * strndup_user - duplicate an existing string from user space
255 * @s: The string to duplicate
256 * @n: Maximum number of bytes to copy, including the trailing NUL.
257 *
258 * Return: newly allocated copy of @s or an ERR_PTR() in case of error
259 */
260char *strndup_user(const char __user *s, long n)
261{
262 char *p;
263 long length;
264
265 length = strnlen_user(s, n);
266
267 if (!length)
268 return ERR_PTR(-EFAULT);
269
270 if (length > n)
271 return ERR_PTR(-EINVAL);
272
273 p = memdup_user(s, length);
274
275 if (IS_ERR(p))
276 return p;
277
278 p[length - 1] = '\0';
279
280 return p;
281}
282EXPORT_SYMBOL(strndup_user);
283
284/**
285 * memdup_user_nul - duplicate memory region from user space and NUL-terminate
286 *
287 * @src: source address in user space
288 * @len: number of bytes to copy
289 *
290 * Return: an ERR_PTR() on failure.
291 */
292void *memdup_user_nul(const void __user *src, size_t len)
293{
294 char *p;
295
296 /*
297 * Always use GFP_KERNEL, since copy_from_user() can sleep and
298 * cause pagefault, which makes it pointless to use GFP_NOFS
299 * or GFP_ATOMIC.
300 */
301 p = kmalloc_track_caller(len + 1, GFP_KERNEL);
302 if (!p)
303 return ERR_PTR(-ENOMEM);
304
305 if (copy_from_user(p, src, len)) {
306 kfree(p);
307 return ERR_PTR(-EFAULT);
308 }
309 p[len] = '\0';
310
311 return p;
312}
313EXPORT_SYMBOL(memdup_user_nul);
314
315/* Check if the vma is being used as a stack by this task */
316int vma_is_stack_for_current(struct vm_area_struct *vma)
317{
318 struct task_struct * __maybe_unused t = current;
319
320 return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
321}
322
323/*
324 * Change backing file, only valid to use during initial VMA setup.
325 */
326void vma_set_file(struct vm_area_struct *vma, struct file *file)
327{
328 /* Changing an anonymous vma with this is illegal */
329 get_file(file);
330 swap(vma->vm_file, file);
331 fput(file);
332}
333EXPORT_SYMBOL(vma_set_file);
334
335#ifndef STACK_RND_MASK
336#define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12)) /* 8MB of VA */
337#endif
338
339unsigned long randomize_stack_top(unsigned long stack_top)
340{
341 unsigned long random_variable = 0;
342
343 if (current->flags & PF_RANDOMIZE) {
344 random_variable = get_random_long();
345 random_variable &= STACK_RND_MASK;
346 random_variable <<= PAGE_SHIFT;
347 }
348#ifdef CONFIG_STACK_GROWSUP
349 return PAGE_ALIGN(stack_top) + random_variable;
350#else
351 return PAGE_ALIGN(stack_top) - random_variable;
352#endif
353}
354
355/**
356 * randomize_page - Generate a random, page aligned address
357 * @start: The smallest acceptable address the caller will take.
358 * @range: The size of the area, starting at @start, within which the
359 * random address must fall.
360 *
361 * If @start + @range would overflow, @range is capped.
362 *
363 * NOTE: Historical use of randomize_range, which this replaces, presumed that
364 * @start was already page aligned. We now align it regardless.
365 *
366 * Return: A page aligned address within [start, start + range). On error,
367 * @start is returned.
368 */
369unsigned long randomize_page(unsigned long start, unsigned long range)
370{
371 if (!PAGE_ALIGNED(start)) {
372 range -= PAGE_ALIGN(start) - start;
373 start = PAGE_ALIGN(start);
374 }
375
376 if (start > ULONG_MAX - range)
377 range = ULONG_MAX - start;
378
379 range >>= PAGE_SHIFT;
380
381 if (range == 0)
382 return start;
383
384 return start + (get_random_long() % range << PAGE_SHIFT);
385}
386
387#ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
388unsigned long __weak arch_randomize_brk(struct mm_struct *mm)
389{
390 /* Is the current task 32bit ? */
391 if (!IS_ENABLED(CONFIG_64BIT) || is_compat_task())
392 return randomize_page(mm->brk, SZ_32M);
393
394 return randomize_page(mm->brk, SZ_1G);
395}
396
397unsigned long arch_mmap_rnd(void)
398{
399 unsigned long rnd;
400
401#ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
402 if (is_compat_task())
403 rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
404 else
405#endif /* CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS */
406 rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
407
408 return rnd << PAGE_SHIFT;
409}
410
411static int mmap_is_legacy(struct rlimit *rlim_stack)
412{
413 if (current->personality & ADDR_COMPAT_LAYOUT)
414 return 1;
415
416 /* On parisc the stack always grows up - so a unlimited stack should
417 * not be an indicator to use the legacy memory layout. */
418 if (rlim_stack->rlim_cur == RLIM_INFINITY &&
419 !IS_ENABLED(CONFIG_STACK_GROWSUP))
420 return 1;
421
422 return sysctl_legacy_va_layout;
423}
424
425/*
426 * Leave enough space between the mmap area and the stack to honour ulimit in
427 * the face of randomisation.
428 */
429#define MIN_GAP (SZ_128M)
430#define MAX_GAP (STACK_TOP / 6 * 5)
431
432static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack)
433{
434#ifdef CONFIG_STACK_GROWSUP
435 /*
436 * For an upwards growing stack the calculation is much simpler.
437 * Memory for the maximum stack size is reserved at the top of the
438 * task. mmap_base starts directly below the stack and grows
439 * downwards.
440 */
441 return PAGE_ALIGN_DOWN(mmap_upper_limit(rlim_stack) - rnd);
442#else
443 unsigned long gap = rlim_stack->rlim_cur;
444 unsigned long pad = stack_guard_gap;
445
446 /* Account for stack randomization if necessary */
447 if (current->flags & PF_RANDOMIZE)
448 pad += (STACK_RND_MASK << PAGE_SHIFT);
449
450 /* Values close to RLIM_INFINITY can overflow. */
451 if (gap + pad > gap)
452 gap += pad;
453
454 if (gap < MIN_GAP)
455 gap = MIN_GAP;
456 else if (gap > MAX_GAP)
457 gap = MAX_GAP;
458
459 return PAGE_ALIGN(STACK_TOP - gap - rnd);
460#endif
461}
462
463void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
464{
465 unsigned long random_factor = 0UL;
466
467 if (current->flags & PF_RANDOMIZE)
468 random_factor = arch_mmap_rnd();
469
470 if (mmap_is_legacy(rlim_stack)) {
471 mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
472 mm->get_unmapped_area = arch_get_unmapped_area;
473 } else {
474 mm->mmap_base = mmap_base(random_factor, rlim_stack);
475 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
476 }
477}
478#elif defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
479void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
480{
481 mm->mmap_base = TASK_UNMAPPED_BASE;
482 mm->get_unmapped_area = arch_get_unmapped_area;
483}
484#endif
485
486/**
487 * __account_locked_vm - account locked pages to an mm's locked_vm
488 * @mm: mm to account against
489 * @pages: number of pages to account
490 * @inc: %true if @pages should be considered positive, %false if not
491 * @task: task used to check RLIMIT_MEMLOCK
492 * @bypass_rlim: %true if checking RLIMIT_MEMLOCK should be skipped
493 *
494 * Assumes @task and @mm are valid (i.e. at least one reference on each), and
495 * that mmap_lock is held as writer.
496 *
497 * Return:
498 * * 0 on success
499 * * -ENOMEM if RLIMIT_MEMLOCK would be exceeded.
500 */
501int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc,
502 struct task_struct *task, bool bypass_rlim)
503{
504 unsigned long locked_vm, limit;
505 int ret = 0;
506
507 mmap_assert_write_locked(mm);
508
509 locked_vm = mm->locked_vm;
510 if (inc) {
511 if (!bypass_rlim) {
512 limit = task_rlimit(task, RLIMIT_MEMLOCK) >> PAGE_SHIFT;
513 if (locked_vm + pages > limit)
514 ret = -ENOMEM;
515 }
516 if (!ret)
517 mm->locked_vm = locked_vm + pages;
518 } else {
519 WARN_ON_ONCE(pages > locked_vm);
520 mm->locked_vm = locked_vm - pages;
521 }
522
523 pr_debug("%s: [%d] caller %ps %c%lu %lu/%lu%s\n", __func__, task->pid,
524 (void *)_RET_IP_, (inc) ? '+' : '-', pages << PAGE_SHIFT,
525 locked_vm << PAGE_SHIFT, task_rlimit(task, RLIMIT_MEMLOCK),
526 ret ? " - exceeded" : "");
527
528 return ret;
529}
530EXPORT_SYMBOL_GPL(__account_locked_vm);
531
532/**
533 * account_locked_vm - account locked pages to an mm's locked_vm
534 * @mm: mm to account against, may be NULL
535 * @pages: number of pages to account
536 * @inc: %true if @pages should be considered positive, %false if not
537 *
538 * Assumes a non-NULL @mm is valid (i.e. at least one reference on it).
539 *
540 * Return:
541 * * 0 on success, or if mm is NULL
542 * * -ENOMEM if RLIMIT_MEMLOCK would be exceeded.
543 */
544int account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc)
545{
546 int ret;
547
548 if (pages == 0 || !mm)
549 return 0;
550
551 mmap_write_lock(mm);
552 ret = __account_locked_vm(mm, pages, inc, current,
553 capable(CAP_IPC_LOCK));
554 mmap_write_unlock(mm);
555
556 return ret;
557}
558EXPORT_SYMBOL_GPL(account_locked_vm);
559
560unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
561 unsigned long len, unsigned long prot,
562 unsigned long flag, unsigned long pgoff)
563{
564 unsigned long ret;
565 struct mm_struct *mm = current->mm;
566 unsigned long populate;
567 LIST_HEAD(uf);
568
569 ret = security_mmap_file(file, prot, flag);
570 if (!ret) {
571 if (mmap_write_lock_killable(mm))
572 return -EINTR;
573 ret = do_mmap(file, addr, len, prot, flag, 0, pgoff, &populate,
574 &uf);
575 mmap_write_unlock(mm);
576 userfaultfd_unmap_complete(mm, &uf);
577 if (populate)
578 mm_populate(ret, populate);
579 }
580 return ret;
581}
582
583unsigned long vm_mmap(struct file *file, unsigned long addr,
584 unsigned long len, unsigned long prot,
585 unsigned long flag, unsigned long offset)
586{
587 if (unlikely(offset + PAGE_ALIGN(len) < offset))
588 return -EINVAL;
589 if (unlikely(offset_in_page(offset)))
590 return -EINVAL;
591
592 return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
593}
594EXPORT_SYMBOL(vm_mmap);
595
596/**
597 * kvmalloc_node - attempt to allocate physically contiguous memory, but upon
598 * failure, fall back to non-contiguous (vmalloc) allocation.
599 * @size: size of the request.
600 * @flags: gfp mask for the allocation - must be compatible (superset) with GFP_KERNEL.
601 * @node: numa node to allocate from
602 *
603 * Uses kmalloc to get the memory but if the allocation fails then falls back
604 * to the vmalloc allocator. Use kvfree for freeing the memory.
605 *
606 * GFP_NOWAIT and GFP_ATOMIC are not supported, neither is the __GFP_NORETRY modifier.
607 * __GFP_RETRY_MAYFAIL is supported, and it should be used only if kmalloc is
608 * preferable to the vmalloc fallback, due to visible performance drawbacks.
609 *
610 * Return: pointer to the allocated memory of %NULL in case of failure
611 */
612void *kvmalloc_node(size_t size, gfp_t flags, int node)
613{
614 gfp_t kmalloc_flags = flags;
615 void *ret;
616
617 /*
618 * We want to attempt a large physically contiguous block first because
619 * it is less likely to fragment multiple larger blocks and therefore
620 * contribute to a long term fragmentation less than vmalloc fallback.
621 * However make sure that larger requests are not too disruptive - no
622 * OOM killer and no allocation failure warnings as we have a fallback.
623 */
624 if (size > PAGE_SIZE) {
625 kmalloc_flags |= __GFP_NOWARN;
626
627 if (!(kmalloc_flags & __GFP_RETRY_MAYFAIL))
628 kmalloc_flags |= __GFP_NORETRY;
629
630 /* nofail semantic is implemented by the vmalloc fallback */
631 kmalloc_flags &= ~__GFP_NOFAIL;
632 }
633
634 ret = kmalloc_node(size, kmalloc_flags, node);
635
636 /*
637 * It doesn't really make sense to fallback to vmalloc for sub page
638 * requests
639 */
640 if (ret || size <= PAGE_SIZE)
641 return ret;
642
643 /* non-sleeping allocations are not supported by vmalloc */
644 if (!gfpflags_allow_blocking(flags))
645 return NULL;
646
647 /* Don't even allow crazy sizes */
648 if (unlikely(size > INT_MAX)) {
649 WARN_ON_ONCE(!(flags & __GFP_NOWARN));
650 return NULL;
651 }
652
653 /*
654 * kvmalloc() can always use VM_ALLOW_HUGE_VMAP,
655 * since the callers already cannot assume anything
656 * about the resulting pointer, and cannot play
657 * protection games.
658 */
659 return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END,
660 flags, PAGE_KERNEL, VM_ALLOW_HUGE_VMAP,
661 node, __builtin_return_address(0));
662}
663EXPORT_SYMBOL(kvmalloc_node);
664
665/**
666 * kvfree() - Free memory.
667 * @addr: Pointer to allocated memory.
668 *
669 * kvfree frees memory allocated by any of vmalloc(), kmalloc() or kvmalloc().
670 * It is slightly more efficient to use kfree() or vfree() if you are certain
671 * that you know which one to use.
672 *
673 * Context: Either preemptible task context or not-NMI interrupt.
674 */
675void kvfree(const void *addr)
676{
677 if (is_vmalloc_addr(addr))
678 vfree(addr);
679 else
680 kfree(addr);
681}
682EXPORT_SYMBOL(kvfree);
683
684/**
685 * kvfree_sensitive - Free a data object containing sensitive information.
686 * @addr: address of the data object to be freed.
687 * @len: length of the data object.
688 *
689 * Use the special memzero_explicit() function to clear the content of a
690 * kvmalloc'ed object containing sensitive data to make sure that the
691 * compiler won't optimize out the data clearing.
692 */
693void kvfree_sensitive(const void *addr, size_t len)
694{
695 if (likely(!ZERO_OR_NULL_PTR(addr))) {
696 memzero_explicit((void *)addr, len);
697 kvfree(addr);
698 }
699}
700EXPORT_SYMBOL(kvfree_sensitive);
701
702void *kvrealloc(const void *p, size_t oldsize, size_t newsize, gfp_t flags)
703{
704 void *newp;
705
706 if (oldsize >= newsize)
707 return (void *)p;
708 newp = kvmalloc(newsize, flags);
709 if (!newp)
710 return NULL;
711 memcpy(newp, p, oldsize);
712 kvfree(p);
713 return newp;
714}
715EXPORT_SYMBOL(kvrealloc);
716
717/**
718 * __vmalloc_array - allocate memory for a virtually contiguous array.
719 * @n: number of elements.
720 * @size: element size.
721 * @flags: the type of memory to allocate (see kmalloc).
722 */
723void *__vmalloc_array(size_t n, size_t size, gfp_t flags)
724{
725 size_t bytes;
726
727 if (unlikely(check_mul_overflow(n, size, &bytes)))
728 return NULL;
729 return __vmalloc(bytes, flags);
730}
731EXPORT_SYMBOL(__vmalloc_array);
732
733/**
734 * vmalloc_array - allocate memory for a virtually contiguous array.
735 * @n: number of elements.
736 * @size: element size.
737 */
738void *vmalloc_array(size_t n, size_t size)
739{
740 return __vmalloc_array(n, size, GFP_KERNEL);
741}
742EXPORT_SYMBOL(vmalloc_array);
743
744/**
745 * __vcalloc - allocate and zero memory for a virtually contiguous array.
746 * @n: number of elements.
747 * @size: element size.
748 * @flags: the type of memory to allocate (see kmalloc).
749 */
750void *__vcalloc(size_t n, size_t size, gfp_t flags)
751{
752 return __vmalloc_array(n, size, flags | __GFP_ZERO);
753}
754EXPORT_SYMBOL(__vcalloc);
755
756/**
757 * vcalloc - allocate and zero memory for a virtually contiguous array.
758 * @n: number of elements.
759 * @size: element size.
760 */
761void *vcalloc(size_t n, size_t size)
762{
763 return __vmalloc_array(n, size, GFP_KERNEL | __GFP_ZERO);
764}
765EXPORT_SYMBOL(vcalloc);
766
767struct anon_vma *folio_anon_vma(struct folio *folio)
768{
769 unsigned long mapping = (unsigned long)folio->mapping;
770
771 if ((mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
772 return NULL;
773 return (void *)(mapping - PAGE_MAPPING_ANON);
774}
775
776/**
777 * folio_mapping - Find the mapping where this folio is stored.
778 * @folio: The folio.
779 *
780 * For folios which are in the page cache, return the mapping that this
781 * page belongs to. Folios in the swap cache return the swap mapping
782 * this page is stored in (which is different from the mapping for the
783 * swap file or swap device where the data is stored).
784 *
785 * You can call this for folios which aren't in the swap cache or page
786 * cache and it will return NULL.
787 */
788struct address_space *folio_mapping(struct folio *folio)
789{
790 struct address_space *mapping;
791
792 /* This happens if someone calls flush_dcache_page on slab page */
793 if (unlikely(folio_test_slab(folio)))
794 return NULL;
795
796 if (unlikely(folio_test_swapcache(folio)))
797 return swap_address_space(folio->swap);
798
799 mapping = folio->mapping;
800 if ((unsigned long)mapping & PAGE_MAPPING_FLAGS)
801 return NULL;
802
803 return mapping;
804}
805EXPORT_SYMBOL(folio_mapping);
806
807/**
808 * folio_copy - Copy the contents of one folio to another.
809 * @dst: Folio to copy to.
810 * @src: Folio to copy from.
811 *
812 * The bytes in the folio represented by @src are copied to @dst.
813 * Assumes the caller has validated that @dst is at least as large as @src.
814 * Can be called in atomic context for order-0 folios, but if the folio is
815 * larger, it may sleep.
816 */
817void folio_copy(struct folio *dst, struct folio *src)
818{
819 long i = 0;
820 long nr = folio_nr_pages(src);
821
822 for (;;) {
823 copy_highpage(folio_page(dst, i), folio_page(src, i));
824 if (++i == nr)
825 break;
826 cond_resched();
827 }
828}
829EXPORT_SYMBOL(folio_copy);
830
831int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS;
832int sysctl_overcommit_ratio __read_mostly = 50;
833unsigned long sysctl_overcommit_kbytes __read_mostly;
834int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
835unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */
836unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */
837
838int overcommit_ratio_handler(struct ctl_table *table, int write, void *buffer,
839 size_t *lenp, loff_t *ppos)
840{
841 int ret;
842
843 ret = proc_dointvec(table, write, buffer, lenp, ppos);
844 if (ret == 0 && write)
845 sysctl_overcommit_kbytes = 0;
846 return ret;
847}
848
849static void sync_overcommit_as(struct work_struct *dummy)
850{
851 percpu_counter_sync(&vm_committed_as);
852}
853
854int overcommit_policy_handler(struct ctl_table *table, int write, void *buffer,
855 size_t *lenp, loff_t *ppos)
856{
857 struct ctl_table t;
858 int new_policy = -1;
859 int ret;
860
861 /*
862 * The deviation of sync_overcommit_as could be big with loose policy
863 * like OVERCOMMIT_ALWAYS/OVERCOMMIT_GUESS. When changing policy to
864 * strict OVERCOMMIT_NEVER, we need to reduce the deviation to comply
865 * with the strict "NEVER", and to avoid possible race condition (even
866 * though user usually won't too frequently do the switching to policy
867 * OVERCOMMIT_NEVER), the switch is done in the following order:
868 * 1. changing the batch
869 * 2. sync percpu count on each CPU
870 * 3. switch the policy
871 */
872 if (write) {
873 t = *table;
874 t.data = &new_policy;
875 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
876 if (ret || new_policy == -1)
877 return ret;
878
879 mm_compute_batch(new_policy);
880 if (new_policy == OVERCOMMIT_NEVER)
881 schedule_on_each_cpu(sync_overcommit_as);
882 sysctl_overcommit_memory = new_policy;
883 } else {
884 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
885 }
886
887 return ret;
888}
889
890int overcommit_kbytes_handler(struct ctl_table *table, int write, void *buffer,
891 size_t *lenp, loff_t *ppos)
892{
893 int ret;
894
895 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
896 if (ret == 0 && write)
897 sysctl_overcommit_ratio = 0;
898 return ret;
899}
900
901/*
902 * Committed memory limit enforced when OVERCOMMIT_NEVER policy is used
903 */
904unsigned long vm_commit_limit(void)
905{
906 unsigned long allowed;
907
908 if (sysctl_overcommit_kbytes)
909 allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10);
910 else
911 allowed = ((totalram_pages() - hugetlb_total_pages())
912 * sysctl_overcommit_ratio / 100);
913 allowed += total_swap_pages;
914
915 return allowed;
916}
917
918/*
919 * Make sure vm_committed_as in one cacheline and not cacheline shared with
920 * other variables. It can be updated by several CPUs frequently.
921 */
922struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
923
924/*
925 * The global memory commitment made in the system can be a metric
926 * that can be used to drive ballooning decisions when Linux is hosted
927 * as a guest. On Hyper-V, the host implements a policy engine for dynamically
928 * balancing memory across competing virtual machines that are hosted.
929 * Several metrics drive this policy engine including the guest reported
930 * memory commitment.
931 *
932 * The time cost of this is very low for small platforms, and for big
933 * platform like a 2S/36C/72T Skylake server, in worst case where
934 * vm_committed_as's spinlock is under severe contention, the time cost
935 * could be about 30~40 microseconds.
936 */
937unsigned long vm_memory_committed(void)
938{
939 return percpu_counter_sum_positive(&vm_committed_as);
940}
941EXPORT_SYMBOL_GPL(vm_memory_committed);
942
943/*
944 * Check that a process has enough memory to allocate a new virtual
945 * mapping. 0 means there is enough memory for the allocation to
946 * succeed and -ENOMEM implies there is not.
947 *
948 * We currently support three overcommit policies, which are set via the
949 * vm.overcommit_memory sysctl. See Documentation/mm/overcommit-accounting.rst
950 *
951 * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
952 * Additional code 2002 Jul 20 by Robert Love.
953 *
954 * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
955 *
956 * Note this is a helper function intended to be used by LSMs which
957 * wish to use this logic.
958 */
959int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
960{
961 long allowed;
962 unsigned long bytes_failed;
963
964 vm_acct_memory(pages);
965
966 /*
967 * Sometimes we want to use more memory than we have
968 */
969 if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
970 return 0;
971
972 if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
973 if (pages > totalram_pages() + total_swap_pages)
974 goto error;
975 return 0;
976 }
977
978 allowed = vm_commit_limit();
979 /*
980 * Reserve some for root
981 */
982 if (!cap_sys_admin)
983 allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
984
985 /*
986 * Don't let a single process grow so big a user can't recover
987 */
988 if (mm) {
989 long reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10);
990
991 allowed -= min_t(long, mm->total_vm / 32, reserve);
992 }
993
994 if (percpu_counter_read_positive(&vm_committed_as) < allowed)
995 return 0;
996error:
997 bytes_failed = pages << PAGE_SHIFT;
998 pr_warn_ratelimited("%s: pid: %d, comm: %s, bytes: %lu not enough memory for the allocation\n",
999 __func__, current->pid, current->comm, bytes_failed);
1000 vm_unacct_memory(pages);
1001
1002 return -ENOMEM;
1003}
1004
1005/**
1006 * get_cmdline() - copy the cmdline value to a buffer.
1007 * @task: the task whose cmdline value to copy.
1008 * @buffer: the buffer to copy to.
1009 * @buflen: the length of the buffer. Larger cmdline values are truncated
1010 * to this length.
1011 *
1012 * Return: the size of the cmdline field copied. Note that the copy does
1013 * not guarantee an ending NULL byte.
1014 */
1015int get_cmdline(struct task_struct *task, char *buffer, int buflen)
1016{
1017 int res = 0;
1018 unsigned int len;
1019 struct mm_struct *mm = get_task_mm(task);
1020 unsigned long arg_start, arg_end, env_start, env_end;
1021 if (!mm)
1022 goto out;
1023 if (!mm->arg_end)
1024 goto out_mm; /* Shh! No looking before we're done */
1025
1026 spin_lock(&mm->arg_lock);
1027 arg_start = mm->arg_start;
1028 arg_end = mm->arg_end;
1029 env_start = mm->env_start;
1030 env_end = mm->env_end;
1031 spin_unlock(&mm->arg_lock);
1032
1033 len = arg_end - arg_start;
1034
1035 if (len > buflen)
1036 len = buflen;
1037
1038 res = access_process_vm(task, arg_start, buffer, len, FOLL_FORCE);
1039
1040 /*
1041 * If the nul at the end of args has been overwritten, then
1042 * assume application is using setproctitle(3).
1043 */
1044 if (res > 0 && buffer[res-1] != '\0' && len < buflen) {
1045 len = strnlen(buffer, res);
1046 if (len < res) {
1047 res = len;
1048 } else {
1049 len = env_end - env_start;
1050 if (len > buflen - res)
1051 len = buflen - res;
1052 res += access_process_vm(task, env_start,
1053 buffer+res, len,
1054 FOLL_FORCE);
1055 res = strnlen(buffer, res);
1056 }
1057 }
1058out_mm:
1059 mmput(mm);
1060out:
1061 return res;
1062}
1063
1064int __weak memcmp_pages(struct page *page1, struct page *page2)
1065{
1066 char *addr1, *addr2;
1067 int ret;
1068
1069 addr1 = kmap_local_page(page1);
1070 addr2 = kmap_local_page(page2);
1071 ret = memcmp(addr1, addr2, PAGE_SIZE);
1072 kunmap_local(addr2);
1073 kunmap_local(addr1);
1074 return ret;
1075}
1076
1077#ifdef CONFIG_PRINTK
1078/**
1079 * mem_dump_obj - Print available provenance information
1080 * @object: object for which to find provenance information.
1081 *
1082 * This function uses pr_cont(), so that the caller is expected to have
1083 * printed out whatever preamble is appropriate. The provenance information
1084 * depends on the type of object and on how much debugging is enabled.
1085 * For example, for a slab-cache object, the slab name is printed, and,
1086 * if available, the return address and stack trace from the allocation
1087 * and last free path of that object.
1088 */
1089void mem_dump_obj(void *object)
1090{
1091 const char *type;
1092
1093 if (kmem_dump_obj(object))
1094 return;
1095
1096 if (vmalloc_dump_obj(object))
1097 return;
1098
1099 if (is_vmalloc_addr(object))
1100 type = "vmalloc memory";
1101 else if (virt_addr_valid(object))
1102 type = "non-slab/vmalloc memory";
1103 else if (object == NULL)
1104 type = "NULL pointer";
1105 else if (object == ZERO_SIZE_PTR)
1106 type = "zero-size pointer";
1107 else
1108 type = "non-paged memory";
1109
1110 pr_cont(" %s\n", type);
1111}
1112EXPORT_SYMBOL_GPL(mem_dump_obj);
1113#endif
1114
1115/*
1116 * A driver might set a page logically offline -- PageOffline() -- and
1117 * turn the page inaccessible in the hypervisor; after that, access to page
1118 * content can be fatal.
1119 *
1120 * Some special PFN walkers -- i.e., /proc/kcore -- read content of random
1121 * pages after checking PageOffline(); however, these PFN walkers can race
1122 * with drivers that set PageOffline().
1123 *
1124 * page_offline_freeze()/page_offline_thaw() allows for a subsystem to
1125 * synchronize with such drivers, achieving that a page cannot be set
1126 * PageOffline() while frozen.
1127 *
1128 * page_offline_begin()/page_offline_end() is used by drivers that care about
1129 * such races when setting a page PageOffline().
1130 */
1131static DECLARE_RWSEM(page_offline_rwsem);
1132
1133void page_offline_freeze(void)
1134{
1135 down_read(&page_offline_rwsem);
1136}
1137
1138void page_offline_thaw(void)
1139{
1140 up_read(&page_offline_rwsem);
1141}
1142
1143void page_offline_begin(void)
1144{
1145 down_write(&page_offline_rwsem);
1146}
1147EXPORT_SYMBOL(page_offline_begin);
1148
1149void page_offline_end(void)
1150{
1151 up_write(&page_offline_rwsem);
1152}
1153EXPORT_SYMBOL(page_offline_end);
1154
1155#ifndef flush_dcache_folio
1156void flush_dcache_folio(struct folio *folio)
1157{
1158 long i, nr = folio_nr_pages(folio);
1159
1160 for (i = 0; i < nr; i++)
1161 flush_dcache_page(folio_page(folio, i));
1162}
1163EXPORT_SYMBOL(flush_dcache_folio);
1164#endif