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>
32 * kfree_const - conditionally free memory
33 * @x: pointer to the memory
35 * Function calls kfree only if @x is not in .rodata section.
37 void kfree_const(const void *x)
39 if (!is_kernel_rodata((unsigned long)x))
42 EXPORT_SYMBOL(kfree_const);
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
49 * Return: newly allocated copy of @s or %NULL in case of error
51 char *kstrdup(const char *s, gfp_t gfp)
60 buf = kmalloc_track_caller(len, gfp);
65 EXPORT_SYMBOL(kstrdup);
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
72 * Note: Strings allocated by kstrdup_const should be freed by kfree_const.
74 * Return: source string if it is in .rodata section otherwise
75 * fallback to kstrdup.
77 const char *kstrdup_const(const char *s, gfp_t gfp)
79 if (is_kernel_rodata((unsigned long)s))
82 return kstrdup(s, gfp);
84 EXPORT_SYMBOL(kstrdup_const);
87 * kstrndup - allocate space for and copy an existing string
88 * @s: the string to duplicate
89 * @max: read at most @max chars from @s
90 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
92 * Note: Use kmemdup_nul() instead if the size is known exactly.
94 * Return: newly allocated copy of @s or %NULL in case of error
96 char *kstrndup(const char *s, size_t max, gfp_t gfp)
104 len = strnlen(s, max);
105 buf = kmalloc_track_caller(len+1, gfp);
112 EXPORT_SYMBOL(kstrndup);
115 * kmemdup - duplicate region of memory
117 * @src: memory region to duplicate
118 * @len: memory region length
119 * @gfp: GFP mask to use
121 * Return: newly allocated copy of @src or %NULL in case of error
123 void *kmemdup(const void *src, size_t len, gfp_t gfp)
127 p = kmalloc_track_caller(len, gfp);
132 EXPORT_SYMBOL(kmemdup);
135 * kmemdup_nul - Create a NUL-terminated string from unterminated data
136 * @s: The data to stringify
137 * @len: The size of the data
138 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
140 * Return: newly allocated copy of @s with NUL-termination or %NULL in
143 char *kmemdup_nul(const char *s, size_t len, gfp_t gfp)
150 buf = kmalloc_track_caller(len + 1, gfp);
157 EXPORT_SYMBOL(kmemdup_nul);
160 * memdup_user - duplicate memory region from user space
162 * @src: source address in user space
163 * @len: number of bytes to copy
165 * Return: an ERR_PTR() on failure. Result is physically
166 * contiguous, to be freed by kfree().
168 void *memdup_user(const void __user *src, size_t len)
172 p = kmalloc_track_caller(len, GFP_USER | __GFP_NOWARN);
174 return ERR_PTR(-ENOMEM);
176 if (copy_from_user(p, src, len)) {
178 return ERR_PTR(-EFAULT);
183 EXPORT_SYMBOL(memdup_user);
186 * vmemdup_user - duplicate memory region from user space
188 * @src: source address in user space
189 * @len: number of bytes to copy
191 * Return: an ERR_PTR() on failure. Result may be not
192 * physically contiguous. Use kvfree() to free.
194 void *vmemdup_user(const void __user *src, size_t len)
198 p = kvmalloc(len, GFP_USER);
200 return ERR_PTR(-ENOMEM);
202 if (copy_from_user(p, src, len)) {
204 return ERR_PTR(-EFAULT);
209 EXPORT_SYMBOL(vmemdup_user);
212 * strndup_user - duplicate an existing string from user space
213 * @s: The string to duplicate
214 * @n: Maximum number of bytes to copy, including the trailing NUL.
216 * Return: newly allocated copy of @s or an ERR_PTR() in case of error
218 char *strndup_user(const char __user *s, long n)
223 length = strnlen_user(s, n);
226 return ERR_PTR(-EFAULT);
229 return ERR_PTR(-EINVAL);
231 p = memdup_user(s, length);
236 p[length - 1] = '\0';
240 EXPORT_SYMBOL(strndup_user);
243 * memdup_user_nul - duplicate memory region from user space and NUL-terminate
245 * @src: source address in user space
246 * @len: number of bytes to copy
248 * Return: an ERR_PTR() on failure.
250 void *memdup_user_nul(const void __user *src, size_t len)
255 * Always use GFP_KERNEL, since copy_from_user() can sleep and
256 * cause pagefault, which makes it pointless to use GFP_NOFS
259 p = kmalloc_track_caller(len + 1, GFP_KERNEL);
261 return ERR_PTR(-ENOMEM);
263 if (copy_from_user(p, src, len)) {
265 return ERR_PTR(-EFAULT);
271 EXPORT_SYMBOL(memdup_user_nul);
273 void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
274 struct vm_area_struct *prev, struct rb_node *rb_parent)
276 struct vm_area_struct *next;
280 next = prev->vm_next;
285 next = rb_entry(rb_parent,
286 struct vm_area_struct, vm_rb);
295 /* Check if the vma is being used as a stack by this task */
296 int vma_is_stack_for_current(struct vm_area_struct *vma)
298 struct task_struct * __maybe_unused t = current;
300 return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
303 #ifndef STACK_RND_MASK
304 #define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12)) /* 8MB of VA */
307 unsigned long randomize_stack_top(unsigned long stack_top)
309 unsigned long random_variable = 0;
311 if (current->flags & PF_RANDOMIZE) {
312 random_variable = get_random_long();
313 random_variable &= STACK_RND_MASK;
314 random_variable <<= PAGE_SHIFT;
316 #ifdef CONFIG_STACK_GROWSUP
317 return PAGE_ALIGN(stack_top) + random_variable;
319 return PAGE_ALIGN(stack_top) - random_variable;
324 * randomize_page - Generate a random, page aligned address
325 * @start: The smallest acceptable address the caller will take.
326 * @range: The size of the area, starting at @start, within which the
327 * random address must fall.
329 * If @start + @range would overflow, @range is capped.
331 * NOTE: Historical use of randomize_range, which this replaces, presumed that
332 * @start was already page aligned. We now align it regardless.
334 * Return: A page aligned address within [start, start + range). On error,
335 * @start is returned.
337 unsigned long randomize_page(unsigned long start, unsigned long range)
339 if (!PAGE_ALIGNED(start)) {
340 range -= PAGE_ALIGN(start) - start;
341 start = PAGE_ALIGN(start);
344 if (start > ULONG_MAX - range)
345 range = ULONG_MAX - start;
347 range >>= PAGE_SHIFT;
352 return start + (get_random_long() % range << PAGE_SHIFT);
355 #ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
356 unsigned long arch_randomize_brk(struct mm_struct *mm)
358 /* Is the current task 32bit ? */
359 if (!IS_ENABLED(CONFIG_64BIT) || is_compat_task())
360 return randomize_page(mm->brk, SZ_32M);
362 return randomize_page(mm->brk, SZ_1G);
365 unsigned long arch_mmap_rnd(void)
369 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
370 if (is_compat_task())
371 rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
373 #endif /* CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS */
374 rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
376 return rnd << PAGE_SHIFT;
379 static int mmap_is_legacy(struct rlimit *rlim_stack)
381 if (current->personality & ADDR_COMPAT_LAYOUT)
384 if (rlim_stack->rlim_cur == RLIM_INFINITY)
387 return sysctl_legacy_va_layout;
391 * Leave enough space between the mmap area and the stack to honour ulimit in
392 * the face of randomisation.
394 #define MIN_GAP (SZ_128M)
395 #define MAX_GAP (STACK_TOP / 6 * 5)
397 static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack)
399 unsigned long gap = rlim_stack->rlim_cur;
400 unsigned long pad = stack_guard_gap;
402 /* Account for stack randomization if necessary */
403 if (current->flags & PF_RANDOMIZE)
404 pad += (STACK_RND_MASK << PAGE_SHIFT);
406 /* Values close to RLIM_INFINITY can overflow. */
412 else if (gap > MAX_GAP)
415 return PAGE_ALIGN(STACK_TOP - gap - rnd);
418 void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
420 unsigned long random_factor = 0UL;
422 if (current->flags & PF_RANDOMIZE)
423 random_factor = arch_mmap_rnd();
425 if (mmap_is_legacy(rlim_stack)) {
426 mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
427 mm->get_unmapped_area = arch_get_unmapped_area;
429 mm->mmap_base = mmap_base(random_factor, rlim_stack);
430 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
433 #elif defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
434 void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
436 mm->mmap_base = TASK_UNMAPPED_BASE;
437 mm->get_unmapped_area = arch_get_unmapped_area;
442 * __account_locked_vm - account locked pages to an mm's locked_vm
443 * @mm: mm to account against
444 * @pages: number of pages to account
445 * @inc: %true if @pages should be considered positive, %false if not
446 * @task: task used to check RLIMIT_MEMLOCK
447 * @bypass_rlim: %true if checking RLIMIT_MEMLOCK should be skipped
449 * Assumes @task and @mm are valid (i.e. at least one reference on each), and
450 * that mmap_sem is held as writer.
454 * * -ENOMEM if RLIMIT_MEMLOCK would be exceeded.
456 int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc,
457 struct task_struct *task, bool bypass_rlim)
459 unsigned long locked_vm, limit;
462 lockdep_assert_held_write(&mm->mmap_sem);
464 locked_vm = mm->locked_vm;
467 limit = task_rlimit(task, RLIMIT_MEMLOCK) >> PAGE_SHIFT;
468 if (locked_vm + pages > limit)
472 mm->locked_vm = locked_vm + pages;
474 WARN_ON_ONCE(pages > locked_vm);
475 mm->locked_vm = locked_vm - pages;
478 pr_debug("%s: [%d] caller %ps %c%lu %lu/%lu%s\n", __func__, task->pid,
479 (void *)_RET_IP_, (inc) ? '+' : '-', pages << PAGE_SHIFT,
480 locked_vm << PAGE_SHIFT, task_rlimit(task, RLIMIT_MEMLOCK),
481 ret ? " - exceeded" : "");
485 EXPORT_SYMBOL_GPL(__account_locked_vm);
488 * account_locked_vm - account locked pages to an mm's locked_vm
489 * @mm: mm to account against, may be NULL
490 * @pages: number of pages to account
491 * @inc: %true if @pages should be considered positive, %false if not
493 * Assumes a non-NULL @mm is valid (i.e. at least one reference on it).
496 * * 0 on success, or if mm is NULL
497 * * -ENOMEM if RLIMIT_MEMLOCK would be exceeded.
499 int account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc)
503 if (pages == 0 || !mm)
506 down_write(&mm->mmap_sem);
507 ret = __account_locked_vm(mm, pages, inc, current,
508 capable(CAP_IPC_LOCK));
509 up_write(&mm->mmap_sem);
513 EXPORT_SYMBOL_GPL(account_locked_vm);
515 unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
516 unsigned long len, unsigned long prot,
517 unsigned long flag, unsigned long pgoff)
520 struct mm_struct *mm = current->mm;
521 unsigned long populate;
524 ret = security_mmap_file(file, prot, flag);
526 if (down_write_killable(&mm->mmap_sem))
528 ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff,
530 up_write(&mm->mmap_sem);
531 userfaultfd_unmap_complete(mm, &uf);
533 mm_populate(ret, populate);
538 unsigned long vm_mmap(struct file *file, unsigned long addr,
539 unsigned long len, unsigned long prot,
540 unsigned long flag, unsigned long offset)
542 if (unlikely(offset + PAGE_ALIGN(len) < offset))
544 if (unlikely(offset_in_page(offset)))
547 return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
549 EXPORT_SYMBOL(vm_mmap);
552 * kvmalloc_node - attempt to allocate physically contiguous memory, but upon
553 * failure, fall back to non-contiguous (vmalloc) allocation.
554 * @size: size of the request.
555 * @flags: gfp mask for the allocation - must be compatible (superset) with GFP_KERNEL.
556 * @node: numa node to allocate from
558 * Uses kmalloc to get the memory but if the allocation fails then falls back
559 * to the vmalloc allocator. Use kvfree for freeing the memory.
561 * Reclaim modifiers - __GFP_NORETRY and __GFP_NOFAIL are not supported.
562 * __GFP_RETRY_MAYFAIL is supported, and it should be used only if kmalloc is
563 * preferable to the vmalloc fallback, due to visible performance drawbacks.
565 * Please note that any use of gfp flags outside of GFP_KERNEL is careful to not
566 * fall back to vmalloc.
568 * Return: pointer to the allocated memory of %NULL in case of failure
570 void *kvmalloc_node(size_t size, gfp_t flags, int node)
572 gfp_t kmalloc_flags = flags;
576 * vmalloc uses GFP_KERNEL for some internal allocations (e.g page tables)
577 * so the given set of flags has to be compatible.
579 if ((flags & GFP_KERNEL) != GFP_KERNEL)
580 return kmalloc_node(size, flags, node);
583 * We want to attempt a large physically contiguous block first because
584 * it is less likely to fragment multiple larger blocks and therefore
585 * contribute to a long term fragmentation less than vmalloc fallback.
586 * However make sure that larger requests are not too disruptive - no
587 * OOM killer and no allocation failure warnings as we have a fallback.
589 if (size > PAGE_SIZE) {
590 kmalloc_flags |= __GFP_NOWARN;
592 if (!(kmalloc_flags & __GFP_RETRY_MAYFAIL))
593 kmalloc_flags |= __GFP_NORETRY;
596 ret = kmalloc_node(size, kmalloc_flags, node);
599 * It doesn't really make sense to fallback to vmalloc for sub page
602 if (ret || size <= PAGE_SIZE)
605 return __vmalloc_node_flags_caller(size, node, flags,
606 __builtin_return_address(0));
608 EXPORT_SYMBOL(kvmalloc_node);
611 * kvfree() - Free memory.
612 * @addr: Pointer to allocated memory.
614 * kvfree frees memory allocated by any of vmalloc(), kmalloc() or kvmalloc().
615 * It is slightly more efficient to use kfree() or vfree() if you are certain
616 * that you know which one to use.
618 * Context: Either preemptible task context or not-NMI interrupt.
620 void kvfree(const void *addr)
622 if (is_vmalloc_addr(addr))
627 EXPORT_SYMBOL(kvfree);
630 * kvfree_sensitive - Free a data object containing sensitive information.
631 * @addr: address of the data object to be freed.
632 * @len: length of the data object.
634 * Use the special memzero_explicit() function to clear the content of a
635 * kvmalloc'ed object containing sensitive data to make sure that the
636 * compiler won't optimize out the data clearing.
638 void kvfree_sensitive(const void *addr, size_t len)
640 if (likely(!ZERO_OR_NULL_PTR(addr))) {
641 memzero_explicit((void *)addr, len);
645 EXPORT_SYMBOL(kvfree_sensitive);
647 static inline void *__page_rmapping(struct page *page)
649 unsigned long mapping;
651 mapping = (unsigned long)page->mapping;
652 mapping &= ~PAGE_MAPPING_FLAGS;
654 return (void *)mapping;
657 /* Neutral page->mapping pointer to address_space or anon_vma or other */
658 void *page_rmapping(struct page *page)
660 page = compound_head(page);
661 return __page_rmapping(page);
665 * Return true if this page is mapped into pagetables.
666 * For compound page it returns true if any subpage of compound page is mapped.
668 bool page_mapped(struct page *page)
672 if (likely(!PageCompound(page)))
673 return atomic_read(&page->_mapcount) >= 0;
674 page = compound_head(page);
675 if (atomic_read(compound_mapcount_ptr(page)) >= 0)
679 for (i = 0; i < compound_nr(page); i++) {
680 if (atomic_read(&page[i]._mapcount) >= 0)
685 EXPORT_SYMBOL(page_mapped);
687 struct anon_vma *page_anon_vma(struct page *page)
689 unsigned long mapping;
691 page = compound_head(page);
692 mapping = (unsigned long)page->mapping;
693 if ((mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
695 return __page_rmapping(page);
698 struct address_space *page_mapping(struct page *page)
700 struct address_space *mapping;
702 page = compound_head(page);
704 /* This happens if someone calls flush_dcache_page on slab page */
705 if (unlikely(PageSlab(page)))
708 if (unlikely(PageSwapCache(page))) {
711 entry.val = page_private(page);
712 return swap_address_space(entry);
715 mapping = page->mapping;
716 if ((unsigned long)mapping & PAGE_MAPPING_ANON)
719 return (void *)((unsigned long)mapping & ~PAGE_MAPPING_FLAGS);
721 EXPORT_SYMBOL(page_mapping);
724 * For file cache pages, return the address_space, otherwise return NULL
726 struct address_space *page_mapping_file(struct page *page)
728 if (unlikely(PageSwapCache(page)))
730 return page_mapping(page);
733 /* Slow path of page_mapcount() for compound pages */
734 int __page_mapcount(struct page *page)
738 ret = atomic_read(&page->_mapcount) + 1;
740 * For file THP page->_mapcount contains total number of mapping
741 * of the page: no need to look into compound_mapcount.
743 if (!PageAnon(page) && !PageHuge(page))
745 page = compound_head(page);
746 ret += atomic_read(compound_mapcount_ptr(page)) + 1;
747 if (PageDoubleMap(page))
751 EXPORT_SYMBOL_GPL(__page_mapcount);
753 int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS;
754 int sysctl_overcommit_ratio __read_mostly = 50;
755 unsigned long sysctl_overcommit_kbytes __read_mostly;
756 int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
757 unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */
758 unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */
760 int overcommit_ratio_handler(struct ctl_table *table, int write,
761 void __user *buffer, size_t *lenp,
766 ret = proc_dointvec(table, write, buffer, lenp, ppos);
767 if (ret == 0 && write)
768 sysctl_overcommit_kbytes = 0;
772 int overcommit_kbytes_handler(struct ctl_table *table, int write,
773 void __user *buffer, size_t *lenp,
778 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
779 if (ret == 0 && write)
780 sysctl_overcommit_ratio = 0;
785 * Committed memory limit enforced when OVERCOMMIT_NEVER policy is used
787 unsigned long vm_commit_limit(void)
789 unsigned long allowed;
791 if (sysctl_overcommit_kbytes)
792 allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10);
794 allowed = ((totalram_pages() - hugetlb_total_pages())
795 * sysctl_overcommit_ratio / 100);
796 allowed += total_swap_pages;
802 * Make sure vm_committed_as in one cacheline and not cacheline shared with
803 * other variables. It can be updated by several CPUs frequently.
805 struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
808 * The global memory commitment made in the system can be a metric
809 * that can be used to drive ballooning decisions when Linux is hosted
810 * as a guest. On Hyper-V, the host implements a policy engine for dynamically
811 * balancing memory across competing virtual machines that are hosted.
812 * Several metrics drive this policy engine including the guest reported
815 unsigned long vm_memory_committed(void)
817 return percpu_counter_read_positive(&vm_committed_as);
819 EXPORT_SYMBOL_GPL(vm_memory_committed);
822 * Check that a process has enough memory to allocate a new virtual
823 * mapping. 0 means there is enough memory for the allocation to
824 * succeed and -ENOMEM implies there is not.
826 * We currently support three overcommit policies, which are set via the
827 * vm.overcommit_memory sysctl. See Documentation/vm/overcommit-accounting.rst
829 * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
830 * Additional code 2002 Jul 20 by Robert Love.
832 * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
834 * Note this is a helper function intended to be used by LSMs which
835 * wish to use this logic.
837 int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
841 VM_WARN_ONCE(percpu_counter_read(&vm_committed_as) <
842 -(s64)vm_committed_as_batch * num_online_cpus(),
843 "memory commitment underflow");
845 vm_acct_memory(pages);
848 * Sometimes we want to use more memory than we have
850 if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
853 if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
854 if (pages > totalram_pages() + total_swap_pages)
859 allowed = vm_commit_limit();
861 * Reserve some for root
864 allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
867 * Don't let a single process grow so big a user can't recover
870 long reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10);
872 allowed -= min_t(long, mm->total_vm / 32, reserve);
875 if (percpu_counter_read_positive(&vm_committed_as) < allowed)
878 vm_unacct_memory(pages);
884 * get_cmdline() - copy the cmdline value to a buffer.
885 * @task: the task whose cmdline value to copy.
886 * @buffer: the buffer to copy to.
887 * @buflen: the length of the buffer. Larger cmdline values are truncated
890 * Return: the size of the cmdline field copied. Note that the copy does
891 * not guarantee an ending NULL byte.
893 int get_cmdline(struct task_struct *task, char *buffer, int buflen)
897 struct mm_struct *mm = get_task_mm(task);
898 unsigned long arg_start, arg_end, env_start, env_end;
902 goto out_mm; /* Shh! No looking before we're done */
904 spin_lock(&mm->arg_lock);
905 arg_start = mm->arg_start;
906 arg_end = mm->arg_end;
907 env_start = mm->env_start;
908 env_end = mm->env_end;
909 spin_unlock(&mm->arg_lock);
911 len = arg_end - arg_start;
916 res = access_process_vm(task, arg_start, buffer, len, FOLL_FORCE);
919 * If the nul at the end of args has been overwritten, then
920 * assume application is using setproctitle(3).
922 if (res > 0 && buffer[res-1] != '\0' && len < buflen) {
923 len = strnlen(buffer, res);
927 len = env_end - env_start;
928 if (len > buflen - res)
930 res += access_process_vm(task, env_start,
933 res = strnlen(buffer, res);
942 int memcmp_pages(struct page *page1, struct page *page2)
947 addr1 = kmap_atomic(page1);
948 addr2 = kmap_atomic(page2);
949 ret = memcmp(addr1, addr2, PAGE_SIZE);
950 kunmap_atomic(addr2);
951 kunmap_atomic(addr1);