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

source code of linux/mm/util.c