1 // SPDX-License-Identifier: GPL-2.0-only
3 #include <linux/slab.h>
4 #include <linux/string.h>
5 #include <linux/compiler.h>
6 #include <linux/export.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>
27 #include <linux/uaccess.h>
33 * kfree_const - conditionally free memory
34 * @x: pointer to the memory
36 * Function calls kfree only if @x is not in .rodata section.
38 void kfree_const(const void *x)
40 if (!is_kernel_rodata((unsigned long)x))
43 EXPORT_SYMBOL(kfree_const);
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
50 * Return: newly allocated copy of @s or %NULL in case of error
52 char *kstrdup(const char *s, gfp_t gfp)
61 buf = kmalloc_track_caller(len, gfp);
66 EXPORT_SYMBOL(kstrdup);
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
73 * Note: Strings allocated by kstrdup_const should be freed by kfree_const and
74 * must not be passed to krealloc().
76 * Return: source string if it is in .rodata section otherwise
77 * fallback to kstrdup.
79 const char *kstrdup_const(const char *s, gfp_t gfp)
81 if (is_kernel_rodata((unsigned long)s))
84 return kstrdup(s, gfp);
86 EXPORT_SYMBOL(kstrdup_const);
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
94 * Note: Use kmemdup_nul() instead if the size is known exactly.
96 * Return: newly allocated copy of @s or %NULL in case of error
98 char *kstrndup(const char *s, size_t max, gfp_t gfp)
106 len = strnlen(s, max);
107 buf = kmalloc_track_caller(len+1, gfp);
114 EXPORT_SYMBOL(kstrndup);
117 * kmemdup - duplicate region of memory
119 * @src: memory region to duplicate
120 * @len: memory region length
121 * @gfp: GFP mask to use
123 * Return: newly allocated copy of @src or %NULL in case of error
125 void *kmemdup(const void *src, size_t len, gfp_t gfp)
129 p = kmalloc_track_caller(len, gfp);
134 EXPORT_SYMBOL(kmemdup);
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
142 * Return: newly allocated copy of @s with NUL-termination or %NULL in
145 char *kmemdup_nul(const char *s, size_t len, gfp_t gfp)
152 buf = kmalloc_track_caller(len + 1, gfp);
159 EXPORT_SYMBOL(kmemdup_nul);
162 * memdup_user - duplicate memory region from user space
164 * @src: source address in user space
165 * @len: number of bytes to copy
167 * Return: an ERR_PTR() on failure. Result is physically
168 * contiguous, to be freed by kfree().
170 void *memdup_user(const void __user *src, size_t len)
174 p = kmalloc_track_caller(len, GFP_USER | __GFP_NOWARN);
176 return ERR_PTR(-ENOMEM);
178 if (copy_from_user(p, src, len)) {
180 return ERR_PTR(-EFAULT);
185 EXPORT_SYMBOL(memdup_user);
188 * vmemdup_user - duplicate memory region from user space
190 * @src: source address in user space
191 * @len: number of bytes to copy
193 * Return: an ERR_PTR() on failure. Result may be not
194 * physically contiguous. Use kvfree() to free.
196 void *vmemdup_user(const void __user *src, size_t len)
200 p = kvmalloc(len, GFP_USER);
202 return ERR_PTR(-ENOMEM);
204 if (copy_from_user(p, src, len)) {
206 return ERR_PTR(-EFAULT);
211 EXPORT_SYMBOL(vmemdup_user);
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.
218 * Return: newly allocated copy of @s or an ERR_PTR() in case of error
220 char *strndup_user(const char __user *s, long n)
225 length = strnlen_user(s, n);
228 return ERR_PTR(-EFAULT);
231 return ERR_PTR(-EINVAL);
233 p = memdup_user(s, length);
238 p[length - 1] = '\0';
242 EXPORT_SYMBOL(strndup_user);
245 * memdup_user_nul - duplicate memory region from user space and NUL-terminate
247 * @src: source address in user space
248 * @len: number of bytes to copy
250 * Return: an ERR_PTR() on failure.
252 void *memdup_user_nul(const void __user *src, size_t len)
257 * Always use GFP_KERNEL, since copy_from_user() can sleep and
258 * cause pagefault, which makes it pointless to use GFP_NOFS
261 p = kmalloc_track_caller(len + 1, GFP_KERNEL);
263 return ERR_PTR(-ENOMEM);
265 if (copy_from_user(p, src, len)) {
267 return ERR_PTR(-EFAULT);
273 EXPORT_SYMBOL(memdup_user_nul);
275 void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
276 struct vm_area_struct *prev)
278 struct vm_area_struct *next;
282 next = prev->vm_next;
293 void __vma_unlink_list(struct mm_struct *mm, struct vm_area_struct *vma)
295 struct vm_area_struct *prev, *next;
300 prev->vm_next = next;
304 next->vm_prev = prev;
307 /* Check if the vma is being used as a stack by this task */
308 int vma_is_stack_for_current(struct vm_area_struct *vma)
310 struct task_struct * __maybe_unused t = current;
312 return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
316 * Change backing file, only valid to use during initial VMA setup.
318 void vma_set_file(struct vm_area_struct *vma, struct file *file)
320 /* Changing an anonymous vma with this is illegal */
322 swap(vma->vm_file, file);
325 EXPORT_SYMBOL(vma_set_file);
327 #ifndef STACK_RND_MASK
328 #define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12)) /* 8MB of VA */
331 unsigned long randomize_stack_top(unsigned long stack_top)
333 unsigned long random_variable = 0;
335 if (current->flags & PF_RANDOMIZE) {
336 random_variable = get_random_long();
337 random_variable &= STACK_RND_MASK;
338 random_variable <<= PAGE_SHIFT;
340 #ifdef CONFIG_STACK_GROWSUP
341 return PAGE_ALIGN(stack_top) + random_variable;
343 return PAGE_ALIGN(stack_top) - random_variable;
348 * randomize_page - Generate a random, page aligned address
349 * @start: The smallest acceptable address the caller will take.
350 * @range: The size of the area, starting at @start, within which the
351 * random address must fall.
353 * If @start + @range would overflow, @range is capped.
355 * NOTE: Historical use of randomize_range, which this replaces, presumed that
356 * @start was already page aligned. We now align it regardless.
358 * Return: A page aligned address within [start, start + range). On error,
359 * @start is returned.
361 unsigned long randomize_page(unsigned long start, unsigned long range)
363 if (!PAGE_ALIGNED(start)) {
364 range -= PAGE_ALIGN(start) - start;
365 start = PAGE_ALIGN(start);
368 if (start > ULONG_MAX - range)
369 range = ULONG_MAX - start;
371 range >>= PAGE_SHIFT;
376 return start + (get_random_long() % range << PAGE_SHIFT);
379 #ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
380 unsigned long __weak arch_randomize_brk(struct mm_struct *mm)
382 /* Is the current task 32bit ? */
383 if (!IS_ENABLED(CONFIG_64BIT) || is_compat_task())
384 return randomize_page(mm->brk, SZ_32M);
386 return randomize_page(mm->brk, SZ_1G);
389 unsigned long arch_mmap_rnd(void)
393 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
394 if (is_compat_task())
395 rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
397 #endif /* CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS */
398 rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
400 return rnd << PAGE_SHIFT;
403 static int mmap_is_legacy(struct rlimit *rlim_stack)
405 if (current->personality & ADDR_COMPAT_LAYOUT)
408 if (rlim_stack->rlim_cur == RLIM_INFINITY)
411 return sysctl_legacy_va_layout;
415 * Leave enough space between the mmap area and the stack to honour ulimit in
416 * the face of randomisation.
418 #define MIN_GAP (SZ_128M)
419 #define MAX_GAP (STACK_TOP / 6 * 5)
421 static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack)
423 unsigned long gap = rlim_stack->rlim_cur;
424 unsigned long pad = stack_guard_gap;
426 /* Account for stack randomization if necessary */
427 if (current->flags & PF_RANDOMIZE)
428 pad += (STACK_RND_MASK << PAGE_SHIFT);
430 /* Values close to RLIM_INFINITY can overflow. */
436 else if (gap > MAX_GAP)
439 return PAGE_ALIGN(STACK_TOP - gap - rnd);
442 void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
444 unsigned long random_factor = 0UL;
446 if (current->flags & PF_RANDOMIZE)
447 random_factor = arch_mmap_rnd();
449 if (mmap_is_legacy(rlim_stack)) {
450 mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
451 mm->get_unmapped_area = arch_get_unmapped_area;
453 mm->mmap_base = mmap_base(random_factor, rlim_stack);
454 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
457 #elif defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
458 void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
460 mm->mmap_base = TASK_UNMAPPED_BASE;
461 mm->get_unmapped_area = arch_get_unmapped_area;
466 * __account_locked_vm - account locked pages to an mm's locked_vm
467 * @mm: mm to account against
468 * @pages: number of pages to account
469 * @inc: %true if @pages should be considered positive, %false if not
470 * @task: task used to check RLIMIT_MEMLOCK
471 * @bypass_rlim: %true if checking RLIMIT_MEMLOCK should be skipped
473 * Assumes @task and @mm are valid (i.e. at least one reference on each), and
474 * that mmap_lock is held as writer.
478 * * -ENOMEM if RLIMIT_MEMLOCK would be exceeded.
480 int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc,
481 struct task_struct *task, bool bypass_rlim)
483 unsigned long locked_vm, limit;
486 mmap_assert_write_locked(mm);
488 locked_vm = mm->locked_vm;
491 limit = task_rlimit(task, RLIMIT_MEMLOCK) >> PAGE_SHIFT;
492 if (locked_vm + pages > limit)
496 mm->locked_vm = locked_vm + pages;
498 WARN_ON_ONCE(pages > locked_vm);
499 mm->locked_vm = locked_vm - pages;
502 pr_debug("%s: [%d] caller %ps %c%lu %lu/%lu%s\n", __func__, task->pid,
503 (void *)_RET_IP_, (inc) ? '+' : '-', pages << PAGE_SHIFT,
504 locked_vm << PAGE_SHIFT, task_rlimit(task, RLIMIT_MEMLOCK),
505 ret ? " - exceeded" : "");
509 EXPORT_SYMBOL_GPL(__account_locked_vm);
512 * account_locked_vm - account locked pages to an mm's locked_vm
513 * @mm: mm to account against, may be NULL
514 * @pages: number of pages to account
515 * @inc: %true if @pages should be considered positive, %false if not
517 * Assumes a non-NULL @mm is valid (i.e. at least one reference on it).
520 * * 0 on success, or if mm is NULL
521 * * -ENOMEM if RLIMIT_MEMLOCK would be exceeded.
523 int account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc)
527 if (pages == 0 || !mm)
531 ret = __account_locked_vm(mm, pages, inc, current,
532 capable(CAP_IPC_LOCK));
533 mmap_write_unlock(mm);
537 EXPORT_SYMBOL_GPL(account_locked_vm);
539 unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
540 unsigned long len, unsigned long prot,
541 unsigned long flag, unsigned long pgoff)
544 struct mm_struct *mm = current->mm;
545 unsigned long populate;
548 ret = security_mmap_file(file, prot, flag);
550 if (mmap_write_lock_killable(mm))
552 ret = do_mmap(file, addr, len, prot, flag, pgoff, &populate,
554 mmap_write_unlock(mm);
555 userfaultfd_unmap_complete(mm, &uf);
557 mm_populate(ret, populate);
562 unsigned long vm_mmap(struct file *file, unsigned long addr,
563 unsigned long len, unsigned long prot,
564 unsigned long flag, unsigned long offset)
566 if (unlikely(offset + PAGE_ALIGN(len) < offset))
568 if (unlikely(offset_in_page(offset)))
571 return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
573 EXPORT_SYMBOL(vm_mmap);
576 * kvmalloc_node - attempt to allocate physically contiguous memory, but upon
577 * failure, fall back to non-contiguous (vmalloc) allocation.
578 * @size: size of the request.
579 * @flags: gfp mask for the allocation - must be compatible (superset) with GFP_KERNEL.
580 * @node: numa node to allocate from
582 * Uses kmalloc to get the memory but if the allocation fails then falls back
583 * to the vmalloc allocator. Use kvfree for freeing the memory.
585 * GFP_NOWAIT and GFP_ATOMIC are not supported, neither is the __GFP_NORETRY modifier.
586 * __GFP_RETRY_MAYFAIL is supported, and it should be used only if kmalloc is
587 * preferable to the vmalloc fallback, due to visible performance drawbacks.
589 * Return: pointer to the allocated memory of %NULL in case of failure
591 void *kvmalloc_node(size_t size, gfp_t flags, int node)
593 gfp_t kmalloc_flags = flags;
597 * We want to attempt a large physically contiguous block first because
598 * it is less likely to fragment multiple larger blocks and therefore
599 * contribute to a long term fragmentation less than vmalloc fallback.
600 * However make sure that larger requests are not too disruptive - no
601 * OOM killer and no allocation failure warnings as we have a fallback.
603 if (size > PAGE_SIZE) {
604 kmalloc_flags |= __GFP_NOWARN;
606 if (!(kmalloc_flags & __GFP_RETRY_MAYFAIL))
607 kmalloc_flags |= __GFP_NORETRY;
609 /* nofail semantic is implemented by the vmalloc fallback */
610 kmalloc_flags &= ~__GFP_NOFAIL;
613 ret = kmalloc_node(size, kmalloc_flags, node);
616 * It doesn't really make sense to fallback to vmalloc for sub page
619 if (ret || size <= PAGE_SIZE)
622 /* non-sleeping allocations are not supported by vmalloc */
623 if (!gfpflags_allow_blocking(flags))
626 /* Don't even allow crazy sizes */
627 if (unlikely(size > INT_MAX)) {
628 WARN_ON_ONCE(!(flags & __GFP_NOWARN));
633 * kvmalloc() can always use VM_ALLOW_HUGE_VMAP,
634 * since the callers already cannot assume anything
635 * about the resulting pointer, and cannot play
638 return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END,
639 flags, PAGE_KERNEL, VM_ALLOW_HUGE_VMAP,
640 node, __builtin_return_address(0));
642 EXPORT_SYMBOL(kvmalloc_node);
645 * kvfree() - Free memory.
646 * @addr: Pointer to allocated memory.
648 * kvfree frees memory allocated by any of vmalloc(), kmalloc() or kvmalloc().
649 * It is slightly more efficient to use kfree() or vfree() if you are certain
650 * that you know which one to use.
652 * Context: Either preemptible task context or not-NMI interrupt.
654 void kvfree(const void *addr)
656 if (is_vmalloc_addr(addr))
661 EXPORT_SYMBOL(kvfree);
664 * kvfree_sensitive - Free a data object containing sensitive information.
665 * @addr: address of the data object to be freed.
666 * @len: length of the data object.
668 * Use the special memzero_explicit() function to clear the content of a
669 * kvmalloc'ed object containing sensitive data to make sure that the
670 * compiler won't optimize out the data clearing.
672 void kvfree_sensitive(const void *addr, size_t len)
674 if (likely(!ZERO_OR_NULL_PTR(addr))) {
675 memzero_explicit((void *)addr, len);
679 EXPORT_SYMBOL(kvfree_sensitive);
681 void *kvrealloc(const void *p, size_t oldsize, size_t newsize, gfp_t flags)
685 if (oldsize >= newsize)
687 newp = kvmalloc(newsize, flags);
690 memcpy(newp, p, oldsize);
694 EXPORT_SYMBOL(kvrealloc);
697 * __vmalloc_array - allocate memory for a virtually contiguous array.
698 * @n: number of elements.
699 * @size: element size.
700 * @flags: the type of memory to allocate (see kmalloc).
702 void *__vmalloc_array(size_t n, size_t size, gfp_t flags)
706 if (unlikely(check_mul_overflow(n, size, &bytes)))
708 return __vmalloc(bytes, flags);
710 EXPORT_SYMBOL(__vmalloc_array);
713 * vmalloc_array - allocate memory for a virtually contiguous array.
714 * @n: number of elements.
715 * @size: element size.
717 void *vmalloc_array(size_t n, size_t size)
719 return __vmalloc_array(n, size, GFP_KERNEL);
721 EXPORT_SYMBOL(vmalloc_array);
724 * __vcalloc - allocate and zero memory for a virtually contiguous array.
725 * @n: number of elements.
726 * @size: element size.
727 * @flags: the type of memory to allocate (see kmalloc).
729 void *__vcalloc(size_t n, size_t size, gfp_t flags)
731 return __vmalloc_array(n, size, flags | __GFP_ZERO);
733 EXPORT_SYMBOL(__vcalloc);
736 * vcalloc - allocate and zero memory for a virtually contiguous array.
737 * @n: number of elements.
738 * @size: element size.
740 void *vcalloc(size_t n, size_t size)
742 return __vmalloc_array(n, size, GFP_KERNEL | __GFP_ZERO);
744 EXPORT_SYMBOL(vcalloc);
746 /* Neutral page->mapping pointer to address_space or anon_vma or other */
747 void *page_rmapping(struct page *page)
749 return folio_raw_mapping(page_folio(page));
753 * folio_mapped - Is this folio mapped into userspace?
756 * Return: True if any page in this folio is referenced by user page tables.
758 bool folio_mapped(struct folio *folio)
762 if (!folio_test_large(folio))
763 return atomic_read(&folio->_mapcount) >= 0;
764 if (atomic_read(folio_mapcount_ptr(folio)) >= 0)
766 if (folio_test_hugetlb(folio))
769 nr = folio_nr_pages(folio);
770 for (i = 0; i < nr; i++) {
771 if (atomic_read(&folio_page(folio, i)->_mapcount) >= 0)
776 EXPORT_SYMBOL(folio_mapped);
778 struct anon_vma *folio_anon_vma(struct folio *folio)
780 unsigned long mapping = (unsigned long)folio->mapping;
782 if ((mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
784 return (void *)(mapping - PAGE_MAPPING_ANON);
788 * folio_mapping - Find the mapping where this folio is stored.
791 * For folios which are in the page cache, return the mapping that this
792 * page belongs to. Folios in the swap cache return the swap mapping
793 * this page is stored in (which is different from the mapping for the
794 * swap file or swap device where the data is stored).
796 * You can call this for folios which aren't in the swap cache or page
797 * cache and it will return NULL.
799 struct address_space *folio_mapping(struct folio *folio)
801 struct address_space *mapping;
803 /* This happens if someone calls flush_dcache_page on slab page */
804 if (unlikely(folio_test_slab(folio)))
807 if (unlikely(folio_test_swapcache(folio)))
808 return swap_address_space(folio_swap_entry(folio));
810 mapping = folio->mapping;
811 if ((unsigned long)mapping & PAGE_MAPPING_FLAGS)
816 EXPORT_SYMBOL(folio_mapping);
818 /* Slow path of page_mapcount() for compound pages */
819 int __page_mapcount(struct page *page)
823 ret = atomic_read(&page->_mapcount) + 1;
825 * For file THP page->_mapcount contains total number of mapping
826 * of the page: no need to look into compound_mapcount.
828 if (!PageAnon(page) && !PageHuge(page))
830 page = compound_head(page);
831 ret += atomic_read(compound_mapcount_ptr(page)) + 1;
832 if (PageDoubleMap(page))
836 EXPORT_SYMBOL_GPL(__page_mapcount);
839 * folio_mapcount() - Calculate the number of mappings of this folio.
842 * A large folio tracks both how many times the entire folio is mapped,
843 * and how many times each individual page in the folio is mapped.
844 * This function calculates the total number of times the folio is
847 * Return: The number of times this folio is mapped.
849 int folio_mapcount(struct folio *folio)
851 int i, compound, nr, ret;
853 if (likely(!folio_test_large(folio)))
854 return atomic_read(&folio->_mapcount) + 1;
856 compound = folio_entire_mapcount(folio);
857 nr = folio_nr_pages(folio);
858 if (folio_test_hugetlb(folio))
861 for (i = 0; i < nr; i++)
862 ret += atomic_read(&folio_page(folio, i)->_mapcount) + 1;
863 /* File pages has compound_mapcount included in _mapcount */
864 if (!folio_test_anon(folio))
865 return ret - compound * nr;
866 if (folio_test_double_map(folio))
872 * folio_copy - Copy the contents of one folio to another.
873 * @dst: Folio to copy to.
874 * @src: Folio to copy from.
876 * The bytes in the folio represented by @src are copied to @dst.
877 * Assumes the caller has validated that @dst is at least as large as @src.
878 * Can be called in atomic context for order-0 folios, but if the folio is
879 * larger, it may sleep.
881 void folio_copy(struct folio *dst, struct folio *src)
884 long nr = folio_nr_pages(src);
887 copy_highpage(folio_page(dst, i), folio_page(src, i));
894 int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS;
895 int sysctl_overcommit_ratio __read_mostly = 50;
896 unsigned long sysctl_overcommit_kbytes __read_mostly;
897 int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
898 unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */
899 unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */
901 int overcommit_ratio_handler(struct ctl_table *table, int write, void *buffer,
902 size_t *lenp, loff_t *ppos)
906 ret = proc_dointvec(table, write, buffer, lenp, ppos);
907 if (ret == 0 && write)
908 sysctl_overcommit_kbytes = 0;
912 static void sync_overcommit_as(struct work_struct *dummy)
914 percpu_counter_sync(&vm_committed_as);
917 int overcommit_policy_handler(struct ctl_table *table, int write, void *buffer,
918 size_t *lenp, loff_t *ppos)
925 * The deviation of sync_overcommit_as could be big with loose policy
926 * like OVERCOMMIT_ALWAYS/OVERCOMMIT_GUESS. When changing policy to
927 * strict OVERCOMMIT_NEVER, we need to reduce the deviation to comply
928 * with the strict "NEVER", and to avoid possible race condition (even
929 * though user usually won't too frequently do the switching to policy
930 * OVERCOMMIT_NEVER), the switch is done in the following order:
931 * 1. changing the batch
932 * 2. sync percpu count on each CPU
933 * 3. switch the policy
937 t.data = &new_policy;
938 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
939 if (ret || new_policy == -1)
942 mm_compute_batch(new_policy);
943 if (new_policy == OVERCOMMIT_NEVER)
944 schedule_on_each_cpu(sync_overcommit_as);
945 sysctl_overcommit_memory = new_policy;
947 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
953 int overcommit_kbytes_handler(struct ctl_table *table, int write, void *buffer,
954 size_t *lenp, loff_t *ppos)
958 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
959 if (ret == 0 && write)
960 sysctl_overcommit_ratio = 0;
965 * Committed memory limit enforced when OVERCOMMIT_NEVER policy is used
967 unsigned long vm_commit_limit(void)
969 unsigned long allowed;
971 if (sysctl_overcommit_kbytes)
972 allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10);
974 allowed = ((totalram_pages() - hugetlb_total_pages())
975 * sysctl_overcommit_ratio / 100);
976 allowed += total_swap_pages;
982 * Make sure vm_committed_as in one cacheline and not cacheline shared with
983 * other variables. It can be updated by several CPUs frequently.
985 struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
988 * The global memory commitment made in the system can be a metric
989 * that can be used to drive ballooning decisions when Linux is hosted
990 * as a guest. On Hyper-V, the host implements a policy engine for dynamically
991 * balancing memory across competing virtual machines that are hosted.
992 * Several metrics drive this policy engine including the guest reported
995 * The time cost of this is very low for small platforms, and for big
996 * platform like a 2S/36C/72T Skylake server, in worst case where
997 * vm_committed_as's spinlock is under severe contention, the time cost
998 * could be about 30~40 microseconds.
1000 unsigned long vm_memory_committed(void)
1002 return percpu_counter_sum_positive(&vm_committed_as);
1004 EXPORT_SYMBOL_GPL(vm_memory_committed);
1007 * Check that a process has enough memory to allocate a new virtual
1008 * mapping. 0 means there is enough memory for the allocation to
1009 * succeed and -ENOMEM implies there is not.
1011 * We currently support three overcommit policies, which are set via the
1012 * vm.overcommit_memory sysctl. See Documentation/mm/overcommit-accounting.rst
1014 * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
1015 * Additional code 2002 Jul 20 by Robert Love.
1017 * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
1019 * Note this is a helper function intended to be used by LSMs which
1020 * wish to use this logic.
1022 int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
1026 vm_acct_memory(pages);
1029 * Sometimes we want to use more memory than we have
1031 if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
1034 if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
1035 if (pages > totalram_pages() + total_swap_pages)
1040 allowed = vm_commit_limit();
1042 * Reserve some for root
1045 allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
1048 * Don't let a single process grow so big a user can't recover
1051 long reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10);
1053 allowed -= min_t(long, mm->total_vm / 32, reserve);
1056 if (percpu_counter_read_positive(&vm_committed_as) < allowed)
1059 vm_unacct_memory(pages);
1065 * get_cmdline() - copy the cmdline value to a buffer.
1066 * @task: the task whose cmdline value to copy.
1067 * @buffer: the buffer to copy to.
1068 * @buflen: the length of the buffer. Larger cmdline values are truncated
1071 * Return: the size of the cmdline field copied. Note that the copy does
1072 * not guarantee an ending NULL byte.
1074 int get_cmdline(struct task_struct *task, char *buffer, int buflen)
1078 struct mm_struct *mm = get_task_mm(task);
1079 unsigned long arg_start, arg_end, env_start, env_end;
1083 goto out_mm; /* Shh! No looking before we're done */
1085 spin_lock(&mm->arg_lock);
1086 arg_start = mm->arg_start;
1087 arg_end = mm->arg_end;
1088 env_start = mm->env_start;
1089 env_end = mm->env_end;
1090 spin_unlock(&mm->arg_lock);
1092 len = arg_end - arg_start;
1097 res = access_process_vm(task, arg_start, buffer, len, FOLL_FORCE);
1100 * If the nul at the end of args has been overwritten, then
1101 * assume application is using setproctitle(3).
1103 if (res > 0 && buffer[res-1] != '\0' && len < buflen) {
1104 len = strnlen(buffer, res);
1108 len = env_end - env_start;
1109 if (len > buflen - res)
1111 res += access_process_vm(task, env_start,
1114 res = strnlen(buffer, res);
1123 int __weak memcmp_pages(struct page *page1, struct page *page2)
1125 char *addr1, *addr2;
1128 addr1 = kmap_atomic(page1);
1129 addr2 = kmap_atomic(page2);
1130 ret = memcmp(addr1, addr2, PAGE_SIZE);
1131 kunmap_atomic(addr2);
1132 kunmap_atomic(addr1);
1136 #ifdef CONFIG_PRINTK
1138 * mem_dump_obj - Print available provenance information
1139 * @object: object for which to find provenance information.
1141 * This function uses pr_cont(), so that the caller is expected to have
1142 * printed out whatever preamble is appropriate. The provenance information
1143 * depends on the type of object and on how much debugging is enabled.
1144 * For example, for a slab-cache object, the slab name is printed, and,
1145 * if available, the return address and stack trace from the allocation
1146 * and last free path of that object.
1148 void mem_dump_obj(void *object)
1152 if (kmem_valid_obj(object)) {
1153 kmem_dump_obj(object);
1157 if (vmalloc_dump_obj(object))
1160 if (virt_addr_valid(object))
1161 type = "non-slab/vmalloc memory";
1162 else if (object == NULL)
1163 type = "NULL pointer";
1164 else if (object == ZERO_SIZE_PTR)
1165 type = "zero-size pointer";
1167 type = "non-paged memory";
1169 pr_cont(" %s\n", type);
1171 EXPORT_SYMBOL_GPL(mem_dump_obj);
1175 * A driver might set a page logically offline -- PageOffline() -- and
1176 * turn the page inaccessible in the hypervisor; after that, access to page
1177 * content can be fatal.
1179 * Some special PFN walkers -- i.e., /proc/kcore -- read content of random
1180 * pages after checking PageOffline(); however, these PFN walkers can race
1181 * with drivers that set PageOffline().
1183 * page_offline_freeze()/page_offline_thaw() allows for a subsystem to
1184 * synchronize with such drivers, achieving that a page cannot be set
1185 * PageOffline() while frozen.
1187 * page_offline_begin()/page_offline_end() is used by drivers that care about
1188 * such races when setting a page PageOffline().
1190 static DECLARE_RWSEM(page_offline_rwsem);
1192 void page_offline_freeze(void)
1194 down_read(&page_offline_rwsem);
1197 void page_offline_thaw(void)
1199 up_read(&page_offline_rwsem);
1202 void page_offline_begin(void)
1204 down_write(&page_offline_rwsem);
1206 EXPORT_SYMBOL(page_offline_begin);
1208 void page_offline_end(void)
1210 up_write(&page_offline_rwsem);
1212 EXPORT_SYMBOL(page_offline_end);
1214 #ifndef ARCH_IMPLEMENTS_FLUSH_DCACHE_FOLIO
1215 void flush_dcache_folio(struct folio *folio)
1217 long i, nr = folio_nr_pages(folio);
1219 for (i = 0; i < nr; i++)
1220 flush_dcache_page(folio_page(folio, i));
1222 EXPORT_SYMBOL(flush_dcache_folio);