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