Loading...
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/mm/nommu.c
4 *
5 * Replacement code for mm functions to support CPU's that don't
6 * have any form of memory management unit (thus no virtual memory).
7 *
8 * See Documentation/admin-guide/mm/nommu-mmap.rst
9 *
10 * Copyright (c) 2004-2008 David Howells <dhowells@redhat.com>
11 * Copyright (c) 2000-2003 David McCullough <davidm@snapgear.com>
12 * Copyright (c) 2000-2001 D Jeff Dionne <jeff@uClinux.org>
13 * Copyright (c) 2002 Greg Ungerer <gerg@snapgear.com>
14 * Copyright (c) 2007-2010 Paul Mundt <lethal@linux-sh.org>
15 */
16
17#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
18
19#include <linux/export.h>
20#include <linux/mm.h>
21#include <linux/sched/mm.h>
22#include <linux/mman.h>
23#include <linux/swap.h>
24#include <linux/file.h>
25#include <linux/highmem.h>
26#include <linux/pagemap.h>
27#include <linux/slab.h>
28#include <linux/vmalloc.h>
29#include <linux/backing-dev.h>
30#include <linux/compiler.h>
31#include <linux/mount.h>
32#include <linux/personality.h>
33#include <linux/security.h>
34#include <linux/syscalls.h>
35#include <linux/audit.h>
36#include <linux/printk.h>
37
38#include <linux/uaccess.h>
39#include <asm/tlb.h>
40#include <asm/tlbflush.h>
41#include <asm/mmu_context.h>
42#include "internal.h"
43
44void *high_memory;
45EXPORT_SYMBOL(high_memory);
46struct page *mem_map;
47unsigned long max_mapnr;
48EXPORT_SYMBOL(max_mapnr);
49unsigned long highest_memmap_pfn;
50int sysctl_nr_trim_pages = CONFIG_NOMMU_INITIAL_TRIM_EXCESS;
51int heap_stack_gap = 0;
52
53atomic_long_t mmap_pages_allocated;
54
55EXPORT_SYMBOL(mem_map);
56
57/* list of mapped, potentially shareable regions */
58static struct kmem_cache *vm_region_jar;
59struct rb_root nommu_region_tree = RB_ROOT;
60DECLARE_RWSEM(nommu_region_sem);
61
62const struct vm_operations_struct generic_file_vm_ops = {
63};
64
65/*
66 * Return the total memory allocated for this pointer, not
67 * just what the caller asked for.
68 *
69 * Doesn't have to be accurate, i.e. may have races.
70 */
71unsigned int kobjsize(const void *objp)
72{
73 struct page *page;
74
75 /*
76 * If the object we have should not have ksize performed on it,
77 * return size of 0
78 */
79 if (!objp || !virt_addr_valid(objp))
80 return 0;
81
82 page = virt_to_head_page(objp);
83
84 /*
85 * If the allocator sets PageSlab, we know the pointer came from
86 * kmalloc().
87 */
88 if (PageSlab(page))
89 return ksize(objp);
90
91 /*
92 * If it's not a compound page, see if we have a matching VMA
93 * region. This test is intentionally done in reverse order,
94 * so if there's no VMA, we still fall through and hand back
95 * PAGE_SIZE for 0-order pages.
96 */
97 if (!PageCompound(page)) {
98 struct vm_area_struct *vma;
99
100 vma = find_vma(current->mm, (unsigned long)objp);
101 if (vma)
102 return vma->vm_end - vma->vm_start;
103 }
104
105 /*
106 * The ksize() function is only guaranteed to work for pointers
107 * returned by kmalloc(). So handle arbitrary pointers here.
108 */
109 return page_size(page);
110}
111
112/**
113 * follow_pfn - look up PFN at a user virtual address
114 * @vma: memory mapping
115 * @address: user virtual address
116 * @pfn: location to store found PFN
117 *
118 * Only IO mappings and raw PFN mappings are allowed.
119 *
120 * Returns zero and the pfn at @pfn on success, -ve otherwise.
121 */
122int follow_pfn(struct vm_area_struct *vma, unsigned long address,
123 unsigned long *pfn)
124{
125 if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
126 return -EINVAL;
127
128 *pfn = address >> PAGE_SHIFT;
129 return 0;
130}
131EXPORT_SYMBOL(follow_pfn);
132
133LIST_HEAD(vmap_area_list);
134
135void vfree(const void *addr)
136{
137 kfree(addr);
138}
139EXPORT_SYMBOL(vfree);
140
141void *__vmalloc(unsigned long size, gfp_t gfp_mask)
142{
143 /*
144 * You can't specify __GFP_HIGHMEM with kmalloc() since kmalloc()
145 * returns only a logical address.
146 */
147 return kmalloc(size, (gfp_mask | __GFP_COMP) & ~__GFP_HIGHMEM);
148}
149EXPORT_SYMBOL(__vmalloc);
150
151void *__vmalloc_node_range(unsigned long size, unsigned long align,
152 unsigned long start, unsigned long end, gfp_t gfp_mask,
153 pgprot_t prot, unsigned long vm_flags, int node,
154 const void *caller)
155{
156 return __vmalloc(size, gfp_mask);
157}
158
159void *__vmalloc_node(unsigned long size, unsigned long align, gfp_t gfp_mask,
160 int node, const void *caller)
161{
162 return __vmalloc(size, gfp_mask);
163}
164
165static void *__vmalloc_user_flags(unsigned long size, gfp_t flags)
166{
167 void *ret;
168
169 ret = __vmalloc(size, flags);
170 if (ret) {
171 struct vm_area_struct *vma;
172
173 mmap_write_lock(current->mm);
174 vma = find_vma(current->mm, (unsigned long)ret);
175 if (vma)
176 vma->vm_flags |= VM_USERMAP;
177 mmap_write_unlock(current->mm);
178 }
179
180 return ret;
181}
182
183void *vmalloc_user(unsigned long size)
184{
185 return __vmalloc_user_flags(size, GFP_KERNEL | __GFP_ZERO);
186}
187EXPORT_SYMBOL(vmalloc_user);
188
189struct page *vmalloc_to_page(const void *addr)
190{
191 return virt_to_page(addr);
192}
193EXPORT_SYMBOL(vmalloc_to_page);
194
195unsigned long vmalloc_to_pfn(const void *addr)
196{
197 return page_to_pfn(virt_to_page(addr));
198}
199EXPORT_SYMBOL(vmalloc_to_pfn);
200
201long vread(char *buf, char *addr, unsigned long count)
202{
203 /* Don't allow overflow */
204 if ((unsigned long) buf + count < count)
205 count = -(unsigned long) buf;
206
207 memcpy(buf, addr, count);
208 return count;
209}
210
211/*
212 * vmalloc - allocate virtually contiguous memory
213 *
214 * @size: allocation size
215 *
216 * Allocate enough pages to cover @size from the page level
217 * allocator and map them into contiguous kernel virtual space.
218 *
219 * For tight control over page level allocator and protection flags
220 * use __vmalloc() instead.
221 */
222void *vmalloc(unsigned long size)
223{
224 return __vmalloc(size, GFP_KERNEL);
225}
226EXPORT_SYMBOL(vmalloc);
227
228void *vmalloc_huge(unsigned long size, gfp_t gfp_mask) __weak __alias(__vmalloc);
229
230/*
231 * vzalloc - allocate virtually contiguous memory with zero fill
232 *
233 * @size: allocation size
234 *
235 * Allocate enough pages to cover @size from the page level
236 * allocator and map them into contiguous kernel virtual space.
237 * The memory allocated is set to zero.
238 *
239 * For tight control over page level allocator and protection flags
240 * use __vmalloc() instead.
241 */
242void *vzalloc(unsigned long size)
243{
244 return __vmalloc(size, GFP_KERNEL | __GFP_ZERO);
245}
246EXPORT_SYMBOL(vzalloc);
247
248/**
249 * vmalloc_node - allocate memory on a specific node
250 * @size: allocation size
251 * @node: numa node
252 *
253 * Allocate enough pages to cover @size from the page level
254 * allocator and map them into contiguous kernel virtual space.
255 *
256 * For tight control over page level allocator and protection flags
257 * use __vmalloc() instead.
258 */
259void *vmalloc_node(unsigned long size, int node)
260{
261 return vmalloc(size);
262}
263EXPORT_SYMBOL(vmalloc_node);
264
265/**
266 * vzalloc_node - allocate memory on a specific node with zero fill
267 * @size: allocation size
268 * @node: numa node
269 *
270 * Allocate enough pages to cover @size from the page level
271 * allocator and map them into contiguous kernel virtual space.
272 * The memory allocated is set to zero.
273 *
274 * For tight control over page level allocator and protection flags
275 * use __vmalloc() instead.
276 */
277void *vzalloc_node(unsigned long size, int node)
278{
279 return vzalloc(size);
280}
281EXPORT_SYMBOL(vzalloc_node);
282
283/**
284 * vmalloc_32 - allocate virtually contiguous memory (32bit addressable)
285 * @size: allocation size
286 *
287 * Allocate enough 32bit PA addressable pages to cover @size from the
288 * page level allocator and map them into contiguous kernel virtual space.
289 */
290void *vmalloc_32(unsigned long size)
291{
292 return __vmalloc(size, GFP_KERNEL);
293}
294EXPORT_SYMBOL(vmalloc_32);
295
296/**
297 * vmalloc_32_user - allocate zeroed virtually contiguous 32bit memory
298 * @size: allocation size
299 *
300 * The resulting memory area is 32bit addressable and zeroed so it can be
301 * mapped to userspace without leaking data.
302 *
303 * VM_USERMAP is set on the corresponding VMA so that subsequent calls to
304 * remap_vmalloc_range() are permissible.
305 */
306void *vmalloc_32_user(unsigned long size)
307{
308 /*
309 * We'll have to sort out the ZONE_DMA bits for 64-bit,
310 * but for now this can simply use vmalloc_user() directly.
311 */
312 return vmalloc_user(size);
313}
314EXPORT_SYMBOL(vmalloc_32_user);
315
316void *vmap(struct page **pages, unsigned int count, unsigned long flags, pgprot_t prot)
317{
318 BUG();
319 return NULL;
320}
321EXPORT_SYMBOL(vmap);
322
323void vunmap(const void *addr)
324{
325 BUG();
326}
327EXPORT_SYMBOL(vunmap);
328
329void *vm_map_ram(struct page **pages, unsigned int count, int node)
330{
331 BUG();
332 return NULL;
333}
334EXPORT_SYMBOL(vm_map_ram);
335
336void vm_unmap_ram(const void *mem, unsigned int count)
337{
338 BUG();
339}
340EXPORT_SYMBOL(vm_unmap_ram);
341
342void vm_unmap_aliases(void)
343{
344}
345EXPORT_SYMBOL_GPL(vm_unmap_aliases);
346
347void free_vm_area(struct vm_struct *area)
348{
349 BUG();
350}
351EXPORT_SYMBOL_GPL(free_vm_area);
352
353int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
354 struct page *page)
355{
356 return -EINVAL;
357}
358EXPORT_SYMBOL(vm_insert_page);
359
360int vm_map_pages(struct vm_area_struct *vma, struct page **pages,
361 unsigned long num)
362{
363 return -EINVAL;
364}
365EXPORT_SYMBOL(vm_map_pages);
366
367int vm_map_pages_zero(struct vm_area_struct *vma, struct page **pages,
368 unsigned long num)
369{
370 return -EINVAL;
371}
372EXPORT_SYMBOL(vm_map_pages_zero);
373
374/*
375 * sys_brk() for the most part doesn't need the global kernel
376 * lock, except when an application is doing something nasty
377 * like trying to un-brk an area that has already been mapped
378 * to a regular file. in this case, the unmapping will need
379 * to invoke file system routines that need the global lock.
380 */
381SYSCALL_DEFINE1(brk, unsigned long, brk)
382{
383 struct mm_struct *mm = current->mm;
384
385 if (brk < mm->start_brk || brk > mm->context.end_brk)
386 return mm->brk;
387
388 if (mm->brk == brk)
389 return mm->brk;
390
391 /*
392 * Always allow shrinking brk
393 */
394 if (brk <= mm->brk) {
395 mm->brk = brk;
396 return brk;
397 }
398
399 /*
400 * Ok, looks good - let it rip.
401 */
402 flush_icache_user_range(mm->brk, brk);
403 return mm->brk = brk;
404}
405
406/*
407 * initialise the percpu counter for VM and region record slabs
408 */
409void __init mmap_init(void)
410{
411 int ret;
412
413 ret = percpu_counter_init(&vm_committed_as, 0, GFP_KERNEL);
414 VM_BUG_ON(ret);
415 vm_region_jar = KMEM_CACHE(vm_region, SLAB_PANIC|SLAB_ACCOUNT);
416}
417
418/*
419 * validate the region tree
420 * - the caller must hold the region lock
421 */
422#ifdef CONFIG_DEBUG_NOMMU_REGIONS
423static noinline void validate_nommu_regions(void)
424{
425 struct vm_region *region, *last;
426 struct rb_node *p, *lastp;
427
428 lastp = rb_first(&nommu_region_tree);
429 if (!lastp)
430 return;
431
432 last = rb_entry(lastp, struct vm_region, vm_rb);
433 BUG_ON(last->vm_end <= last->vm_start);
434 BUG_ON(last->vm_top < last->vm_end);
435
436 while ((p = rb_next(lastp))) {
437 region = rb_entry(p, struct vm_region, vm_rb);
438 last = rb_entry(lastp, struct vm_region, vm_rb);
439
440 BUG_ON(region->vm_end <= region->vm_start);
441 BUG_ON(region->vm_top < region->vm_end);
442 BUG_ON(region->vm_start < last->vm_top);
443
444 lastp = p;
445 }
446}
447#else
448static void validate_nommu_regions(void)
449{
450}
451#endif
452
453/*
454 * add a region into the global tree
455 */
456static void add_nommu_region(struct vm_region *region)
457{
458 struct vm_region *pregion;
459 struct rb_node **p, *parent;
460
461 validate_nommu_regions();
462
463 parent = NULL;
464 p = &nommu_region_tree.rb_node;
465 while (*p) {
466 parent = *p;
467 pregion = rb_entry(parent, struct vm_region, vm_rb);
468 if (region->vm_start < pregion->vm_start)
469 p = &(*p)->rb_left;
470 else if (region->vm_start > pregion->vm_start)
471 p = &(*p)->rb_right;
472 else if (pregion == region)
473 return;
474 else
475 BUG();
476 }
477
478 rb_link_node(®ion->vm_rb, parent, p);
479 rb_insert_color(®ion->vm_rb, &nommu_region_tree);
480
481 validate_nommu_regions();
482}
483
484/*
485 * delete a region from the global tree
486 */
487static void delete_nommu_region(struct vm_region *region)
488{
489 BUG_ON(!nommu_region_tree.rb_node);
490
491 validate_nommu_regions();
492 rb_erase(®ion->vm_rb, &nommu_region_tree);
493 validate_nommu_regions();
494}
495
496/*
497 * free a contiguous series of pages
498 */
499static void free_page_series(unsigned long from, unsigned long to)
500{
501 for (; from < to; from += PAGE_SIZE) {
502 struct page *page = virt_to_page((void *)from);
503
504 atomic_long_dec(&mmap_pages_allocated);
505 put_page(page);
506 }
507}
508
509/*
510 * release a reference to a region
511 * - the caller must hold the region semaphore for writing, which this releases
512 * - the region may not have been added to the tree yet, in which case vm_top
513 * will equal vm_start
514 */
515static void __put_nommu_region(struct vm_region *region)
516 __releases(nommu_region_sem)
517{
518 BUG_ON(!nommu_region_tree.rb_node);
519
520 if (--region->vm_usage == 0) {
521 if (region->vm_top > region->vm_start)
522 delete_nommu_region(region);
523 up_write(&nommu_region_sem);
524
525 if (region->vm_file)
526 fput(region->vm_file);
527
528 /* IO memory and memory shared directly out of the pagecache
529 * from ramfs/tmpfs mustn't be released here */
530 if (region->vm_flags & VM_MAPPED_COPY)
531 free_page_series(region->vm_start, region->vm_top);
532 kmem_cache_free(vm_region_jar, region);
533 } else {
534 up_write(&nommu_region_sem);
535 }
536}
537
538/*
539 * release a reference to a region
540 */
541static void put_nommu_region(struct vm_region *region)
542{
543 down_write(&nommu_region_sem);
544 __put_nommu_region(region);
545}
546
547void vma_mas_store(struct vm_area_struct *vma, struct ma_state *mas)
548{
549 mas_set_range(mas, vma->vm_start, vma->vm_end - 1);
550 mas_store_prealloc(mas, vma);
551}
552
553void vma_mas_remove(struct vm_area_struct *vma, struct ma_state *mas)
554{
555 mas->index = vma->vm_start;
556 mas->last = vma->vm_end - 1;
557 mas_store_prealloc(mas, NULL);
558}
559
560static void setup_vma_to_mm(struct vm_area_struct *vma, struct mm_struct *mm)
561{
562 vma->vm_mm = mm;
563
564 /* add the VMA to the mapping */
565 if (vma->vm_file) {
566 struct address_space *mapping = vma->vm_file->f_mapping;
567
568 i_mmap_lock_write(mapping);
569 flush_dcache_mmap_lock(mapping);
570 vma_interval_tree_insert(vma, &mapping->i_mmap);
571 flush_dcache_mmap_unlock(mapping);
572 i_mmap_unlock_write(mapping);
573 }
574}
575
576/*
577 * mas_add_vma_to_mm() - Maple state variant of add_mas_to_mm().
578 * @mas: The maple state with preallocations.
579 * @mm: The mm_struct
580 * @vma: The vma to add
581 *
582 */
583static void mas_add_vma_to_mm(struct ma_state *mas, struct mm_struct *mm,
584 struct vm_area_struct *vma)
585{
586 BUG_ON(!vma->vm_region);
587
588 setup_vma_to_mm(vma, mm);
589 mm->map_count++;
590
591 /* add the VMA to the tree */
592 vma_mas_store(vma, mas);
593}
594
595/*
596 * add a VMA into a process's mm_struct in the appropriate place in the list
597 * and tree and add to the address space's page tree also if not an anonymous
598 * page
599 * - should be called with mm->mmap_lock held writelocked
600 */
601static int add_vma_to_mm(struct mm_struct *mm, struct vm_area_struct *vma)
602{
603 MA_STATE(mas, &mm->mm_mt, vma->vm_start, vma->vm_end);
604
605 if (mas_preallocate(&mas, vma, GFP_KERNEL)) {
606 pr_warn("Allocation of vma tree for process %d failed\n",
607 current->pid);
608 return -ENOMEM;
609 }
610 mas_add_vma_to_mm(&mas, mm, vma);
611 return 0;
612}
613
614static void cleanup_vma_from_mm(struct vm_area_struct *vma)
615{
616 vma->vm_mm->map_count--;
617 /* remove the VMA from the mapping */
618 if (vma->vm_file) {
619 struct address_space *mapping;
620 mapping = vma->vm_file->f_mapping;
621
622 i_mmap_lock_write(mapping);
623 flush_dcache_mmap_lock(mapping);
624 vma_interval_tree_remove(vma, &mapping->i_mmap);
625 flush_dcache_mmap_unlock(mapping);
626 i_mmap_unlock_write(mapping);
627 }
628}
629/*
630 * delete a VMA from its owning mm_struct and address space
631 */
632static int delete_vma_from_mm(struct vm_area_struct *vma)
633{
634 MA_STATE(mas, &vma->vm_mm->mm_mt, 0, 0);
635
636 if (mas_preallocate(&mas, vma, GFP_KERNEL)) {
637 pr_warn("Allocation of vma tree for process %d failed\n",
638 current->pid);
639 return -ENOMEM;
640 }
641 cleanup_vma_from_mm(vma);
642
643 /* remove from the MM's tree and list */
644 vma_mas_remove(vma, &mas);
645 return 0;
646}
647
648/*
649 * destroy a VMA record
650 */
651static void delete_vma(struct mm_struct *mm, struct vm_area_struct *vma)
652{
653 if (vma->vm_ops && vma->vm_ops->close)
654 vma->vm_ops->close(vma);
655 if (vma->vm_file)
656 fput(vma->vm_file);
657 put_nommu_region(vma->vm_region);
658 vm_area_free(vma);
659}
660
661struct vm_area_struct *find_vma_intersection(struct mm_struct *mm,
662 unsigned long start_addr,
663 unsigned long end_addr)
664{
665 unsigned long index = start_addr;
666
667 mmap_assert_locked(mm);
668 return mt_find(&mm->mm_mt, &index, end_addr - 1);
669}
670EXPORT_SYMBOL(find_vma_intersection);
671
672/*
673 * look up the first VMA in which addr resides, NULL if none
674 * - should be called with mm->mmap_lock at least held readlocked
675 */
676struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
677{
678 MA_STATE(mas, &mm->mm_mt, addr, addr);
679
680 return mas_walk(&mas);
681}
682EXPORT_SYMBOL(find_vma);
683
684/*
685 * find a VMA
686 * - we don't extend stack VMAs under NOMMU conditions
687 */
688struct vm_area_struct *find_extend_vma(struct mm_struct *mm, unsigned long addr)
689{
690 return find_vma(mm, addr);
691}
692
693/*
694 * expand a stack to a given address
695 * - not supported under NOMMU conditions
696 */
697int expand_stack(struct vm_area_struct *vma, unsigned long address)
698{
699 return -ENOMEM;
700}
701
702/*
703 * look up the first VMA exactly that exactly matches addr
704 * - should be called with mm->mmap_lock at least held readlocked
705 */
706static struct vm_area_struct *find_vma_exact(struct mm_struct *mm,
707 unsigned long addr,
708 unsigned long len)
709{
710 struct vm_area_struct *vma;
711 unsigned long end = addr + len;
712 MA_STATE(mas, &mm->mm_mt, addr, addr);
713
714 vma = mas_walk(&mas);
715 if (!vma)
716 return NULL;
717 if (vma->vm_start != addr)
718 return NULL;
719 if (vma->vm_end != end)
720 return NULL;
721
722 return vma;
723}
724
725/*
726 * determine whether a mapping should be permitted and, if so, what sort of
727 * mapping we're capable of supporting
728 */
729static int validate_mmap_request(struct file *file,
730 unsigned long addr,
731 unsigned long len,
732 unsigned long prot,
733 unsigned long flags,
734 unsigned long pgoff,
735 unsigned long *_capabilities)
736{
737 unsigned long capabilities, rlen;
738 int ret;
739
740 /* do the simple checks first */
741 if (flags & MAP_FIXED)
742 return -EINVAL;
743
744 if ((flags & MAP_TYPE) != MAP_PRIVATE &&
745 (flags & MAP_TYPE) != MAP_SHARED)
746 return -EINVAL;
747
748 if (!len)
749 return -EINVAL;
750
751 /* Careful about overflows.. */
752 rlen = PAGE_ALIGN(len);
753 if (!rlen || rlen > TASK_SIZE)
754 return -ENOMEM;
755
756 /* offset overflow? */
757 if ((pgoff + (rlen >> PAGE_SHIFT)) < pgoff)
758 return -EOVERFLOW;
759
760 if (file) {
761 /* files must support mmap */
762 if (!file->f_op->mmap)
763 return -ENODEV;
764
765 /* work out if what we've got could possibly be shared
766 * - we support chardevs that provide their own "memory"
767 * - we support files/blockdevs that are memory backed
768 */
769 if (file->f_op->mmap_capabilities) {
770 capabilities = file->f_op->mmap_capabilities(file);
771 } else {
772 /* no explicit capabilities set, so assume some
773 * defaults */
774 switch (file_inode(file)->i_mode & S_IFMT) {
775 case S_IFREG:
776 case S_IFBLK:
777 capabilities = NOMMU_MAP_COPY;
778 break;
779
780 case S_IFCHR:
781 capabilities =
782 NOMMU_MAP_DIRECT |
783 NOMMU_MAP_READ |
784 NOMMU_MAP_WRITE;
785 break;
786
787 default:
788 return -EINVAL;
789 }
790 }
791
792 /* eliminate any capabilities that we can't support on this
793 * device */
794 if (!file->f_op->get_unmapped_area)
795 capabilities &= ~NOMMU_MAP_DIRECT;
796 if (!(file->f_mode & FMODE_CAN_READ))
797 capabilities &= ~NOMMU_MAP_COPY;
798
799 /* The file shall have been opened with read permission. */
800 if (!(file->f_mode & FMODE_READ))
801 return -EACCES;
802
803 if (flags & MAP_SHARED) {
804 /* do checks for writing, appending and locking */
805 if ((prot & PROT_WRITE) &&
806 !(file->f_mode & FMODE_WRITE))
807 return -EACCES;
808
809 if (IS_APPEND(file_inode(file)) &&
810 (file->f_mode & FMODE_WRITE))
811 return -EACCES;
812
813 if (!(capabilities & NOMMU_MAP_DIRECT))
814 return -ENODEV;
815
816 /* we mustn't privatise shared mappings */
817 capabilities &= ~NOMMU_MAP_COPY;
818 } else {
819 /* we're going to read the file into private memory we
820 * allocate */
821 if (!(capabilities & NOMMU_MAP_COPY))
822 return -ENODEV;
823
824 /* we don't permit a private writable mapping to be
825 * shared with the backing device */
826 if (prot & PROT_WRITE)
827 capabilities &= ~NOMMU_MAP_DIRECT;
828 }
829
830 if (capabilities & NOMMU_MAP_DIRECT) {
831 if (((prot & PROT_READ) && !(capabilities & NOMMU_MAP_READ)) ||
832 ((prot & PROT_WRITE) && !(capabilities & NOMMU_MAP_WRITE)) ||
833 ((prot & PROT_EXEC) && !(capabilities & NOMMU_MAP_EXEC))
834 ) {
835 capabilities &= ~NOMMU_MAP_DIRECT;
836 if (flags & MAP_SHARED) {
837 pr_warn("MAP_SHARED not completely supported on !MMU\n");
838 return -EINVAL;
839 }
840 }
841 }
842
843 /* handle executable mappings and implied executable
844 * mappings */
845 if (path_noexec(&file->f_path)) {
846 if (prot & PROT_EXEC)
847 return -EPERM;
848 } else if ((prot & PROT_READ) && !(prot & PROT_EXEC)) {
849 /* handle implication of PROT_EXEC by PROT_READ */
850 if (current->personality & READ_IMPLIES_EXEC) {
851 if (capabilities & NOMMU_MAP_EXEC)
852 prot |= PROT_EXEC;
853 }
854 } else if ((prot & PROT_READ) &&
855 (prot & PROT_EXEC) &&
856 !(capabilities & NOMMU_MAP_EXEC)
857 ) {
858 /* backing file is not executable, try to copy */
859 capabilities &= ~NOMMU_MAP_DIRECT;
860 }
861 } else {
862 /* anonymous mappings are always memory backed and can be
863 * privately mapped
864 */
865 capabilities = NOMMU_MAP_COPY;
866
867 /* handle PROT_EXEC implication by PROT_READ */
868 if ((prot & PROT_READ) &&
869 (current->personality & READ_IMPLIES_EXEC))
870 prot |= PROT_EXEC;
871 }
872
873 /* allow the security API to have its say */
874 ret = security_mmap_addr(addr);
875 if (ret < 0)
876 return ret;
877
878 /* looks okay */
879 *_capabilities = capabilities;
880 return 0;
881}
882
883/*
884 * we've determined that we can make the mapping, now translate what we
885 * now know into VMA flags
886 */
887static unsigned long determine_vm_flags(struct file *file,
888 unsigned long prot,
889 unsigned long flags,
890 unsigned long capabilities)
891{
892 unsigned long vm_flags;
893
894 vm_flags = calc_vm_prot_bits(prot, 0) | calc_vm_flag_bits(flags);
895 /* vm_flags |= mm->def_flags; */
896
897 if (!(capabilities & NOMMU_MAP_DIRECT)) {
898 /* attempt to share read-only copies of mapped file chunks */
899 vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
900 if (file && !(prot & PROT_WRITE))
901 vm_flags |= VM_MAYSHARE;
902 } else {
903 /* overlay a shareable mapping on the backing device or inode
904 * if possible - used for chardevs, ramfs/tmpfs/shmfs and
905 * romfs/cramfs */
906 vm_flags |= VM_MAYSHARE | (capabilities & NOMMU_VMFLAGS);
907 if (flags & MAP_SHARED)
908 vm_flags |= VM_SHARED;
909 }
910
911 /* refuse to let anyone share private mappings with this process if
912 * it's being traced - otherwise breakpoints set in it may interfere
913 * with another untraced process
914 */
915 if ((flags & MAP_PRIVATE) && current->ptrace)
916 vm_flags &= ~VM_MAYSHARE;
917
918 return vm_flags;
919}
920
921/*
922 * set up a shared mapping on a file (the driver or filesystem provides and
923 * pins the storage)
924 */
925static int do_mmap_shared_file(struct vm_area_struct *vma)
926{
927 int ret;
928
929 ret = call_mmap(vma->vm_file, vma);
930 if (ret == 0) {
931 vma->vm_region->vm_top = vma->vm_region->vm_end;
932 return 0;
933 }
934 if (ret != -ENOSYS)
935 return ret;
936
937 /* getting -ENOSYS indicates that direct mmap isn't possible (as
938 * opposed to tried but failed) so we can only give a suitable error as
939 * it's not possible to make a private copy if MAP_SHARED was given */
940 return -ENODEV;
941}
942
943/*
944 * set up a private mapping or an anonymous shared mapping
945 */
946static int do_mmap_private(struct vm_area_struct *vma,
947 struct vm_region *region,
948 unsigned long len,
949 unsigned long capabilities)
950{
951 unsigned long total, point;
952 void *base;
953 int ret, order;
954
955 /* invoke the file's mapping function so that it can keep track of
956 * shared mappings on devices or memory
957 * - VM_MAYSHARE will be set if it may attempt to share
958 */
959 if (capabilities & NOMMU_MAP_DIRECT) {
960 ret = call_mmap(vma->vm_file, vma);
961 if (ret == 0) {
962 /* shouldn't return success if we're not sharing */
963 BUG_ON(!(vma->vm_flags & VM_MAYSHARE));
964 vma->vm_region->vm_top = vma->vm_region->vm_end;
965 return 0;
966 }
967 if (ret != -ENOSYS)
968 return ret;
969
970 /* getting an ENOSYS error indicates that direct mmap isn't
971 * possible (as opposed to tried but failed) so we'll try to
972 * make a private copy of the data and map that instead */
973 }
974
975
976 /* allocate some memory to hold the mapping
977 * - note that this may not return a page-aligned address if the object
978 * we're allocating is smaller than a page
979 */
980 order = get_order(len);
981 total = 1 << order;
982 point = len >> PAGE_SHIFT;
983
984 /* we don't want to allocate a power-of-2 sized page set */
985 if (sysctl_nr_trim_pages && total - point >= sysctl_nr_trim_pages)
986 total = point;
987
988 base = alloc_pages_exact(total << PAGE_SHIFT, GFP_KERNEL);
989 if (!base)
990 goto enomem;
991
992 atomic_long_add(total, &mmap_pages_allocated);
993
994 region->vm_flags = vma->vm_flags |= VM_MAPPED_COPY;
995 region->vm_start = (unsigned long) base;
996 region->vm_end = region->vm_start + len;
997 region->vm_top = region->vm_start + (total << PAGE_SHIFT);
998
999 vma->vm_start = region->vm_start;
1000 vma->vm_end = region->vm_start + len;
1001
1002 if (vma->vm_file) {
1003 /* read the contents of a file into the copy */
1004 loff_t fpos;
1005
1006 fpos = vma->vm_pgoff;
1007 fpos <<= PAGE_SHIFT;
1008
1009 ret = kernel_read(vma->vm_file, base, len, &fpos);
1010 if (ret < 0)
1011 goto error_free;
1012
1013 /* clear the last little bit */
1014 if (ret < len)
1015 memset(base + ret, 0, len - ret);
1016
1017 } else {
1018 vma_set_anonymous(vma);
1019 }
1020
1021 return 0;
1022
1023error_free:
1024 free_page_series(region->vm_start, region->vm_top);
1025 region->vm_start = vma->vm_start = 0;
1026 region->vm_end = vma->vm_end = 0;
1027 region->vm_top = 0;
1028 return ret;
1029
1030enomem:
1031 pr_err("Allocation of length %lu from process %d (%s) failed\n",
1032 len, current->pid, current->comm);
1033 show_free_areas(0, NULL);
1034 return -ENOMEM;
1035}
1036
1037/*
1038 * handle mapping creation for uClinux
1039 */
1040unsigned long do_mmap(struct file *file,
1041 unsigned long addr,
1042 unsigned long len,
1043 unsigned long prot,
1044 unsigned long flags,
1045 unsigned long pgoff,
1046 unsigned long *populate,
1047 struct list_head *uf)
1048{
1049 struct vm_area_struct *vma;
1050 struct vm_region *region;
1051 struct rb_node *rb;
1052 vm_flags_t vm_flags;
1053 unsigned long capabilities, result;
1054 int ret;
1055 MA_STATE(mas, ¤t->mm->mm_mt, 0, 0);
1056
1057 *populate = 0;
1058
1059 /* decide whether we should attempt the mapping, and if so what sort of
1060 * mapping */
1061 ret = validate_mmap_request(file, addr, len, prot, flags, pgoff,
1062 &capabilities);
1063 if (ret < 0)
1064 return ret;
1065
1066 /* we ignore the address hint */
1067 addr = 0;
1068 len = PAGE_ALIGN(len);
1069
1070 /* we've determined that we can make the mapping, now translate what we
1071 * now know into VMA flags */
1072 vm_flags = determine_vm_flags(file, prot, flags, capabilities);
1073
1074
1075 /* we're going to need to record the mapping */
1076 region = kmem_cache_zalloc(vm_region_jar, GFP_KERNEL);
1077 if (!region)
1078 goto error_getting_region;
1079
1080 vma = vm_area_alloc(current->mm);
1081 if (!vma)
1082 goto error_getting_vma;
1083
1084 if (mas_preallocate(&mas, vma, GFP_KERNEL))
1085 goto error_maple_preallocate;
1086
1087 region->vm_usage = 1;
1088 region->vm_flags = vm_flags;
1089 region->vm_pgoff = pgoff;
1090
1091 vma->vm_flags = vm_flags;
1092 vma->vm_pgoff = pgoff;
1093
1094 if (file) {
1095 region->vm_file = get_file(file);
1096 vma->vm_file = get_file(file);
1097 }
1098
1099 down_write(&nommu_region_sem);
1100
1101 /* if we want to share, we need to check for regions created by other
1102 * mmap() calls that overlap with our proposed mapping
1103 * - we can only share with a superset match on most regular files
1104 * - shared mappings on character devices and memory backed files are
1105 * permitted to overlap inexactly as far as we are concerned for in
1106 * these cases, sharing is handled in the driver or filesystem rather
1107 * than here
1108 */
1109 if (vm_flags & VM_MAYSHARE) {
1110 struct vm_region *pregion;
1111 unsigned long pglen, rpglen, pgend, rpgend, start;
1112
1113 pglen = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1114 pgend = pgoff + pglen;
1115
1116 for (rb = rb_first(&nommu_region_tree); rb; rb = rb_next(rb)) {
1117 pregion = rb_entry(rb, struct vm_region, vm_rb);
1118
1119 if (!(pregion->vm_flags & VM_MAYSHARE))
1120 continue;
1121
1122 /* search for overlapping mappings on the same file */
1123 if (file_inode(pregion->vm_file) !=
1124 file_inode(file))
1125 continue;
1126
1127 if (pregion->vm_pgoff >= pgend)
1128 continue;
1129
1130 rpglen = pregion->vm_end - pregion->vm_start;
1131 rpglen = (rpglen + PAGE_SIZE - 1) >> PAGE_SHIFT;
1132 rpgend = pregion->vm_pgoff + rpglen;
1133 if (pgoff >= rpgend)
1134 continue;
1135
1136 /* handle inexactly overlapping matches between
1137 * mappings */
1138 if ((pregion->vm_pgoff != pgoff || rpglen != pglen) &&
1139 !(pgoff >= pregion->vm_pgoff && pgend <= rpgend)) {
1140 /* new mapping is not a subset of the region */
1141 if (!(capabilities & NOMMU_MAP_DIRECT))
1142 goto sharing_violation;
1143 continue;
1144 }
1145
1146 /* we've found a region we can share */
1147 pregion->vm_usage++;
1148 vma->vm_region = pregion;
1149 start = pregion->vm_start;
1150 start += (pgoff - pregion->vm_pgoff) << PAGE_SHIFT;
1151 vma->vm_start = start;
1152 vma->vm_end = start + len;
1153
1154 if (pregion->vm_flags & VM_MAPPED_COPY)
1155 vma->vm_flags |= VM_MAPPED_COPY;
1156 else {
1157 ret = do_mmap_shared_file(vma);
1158 if (ret < 0) {
1159 vma->vm_region = NULL;
1160 vma->vm_start = 0;
1161 vma->vm_end = 0;
1162 pregion->vm_usage--;
1163 pregion = NULL;
1164 goto error_just_free;
1165 }
1166 }
1167 fput(region->vm_file);
1168 kmem_cache_free(vm_region_jar, region);
1169 region = pregion;
1170 result = start;
1171 goto share;
1172 }
1173
1174 /* obtain the address at which to make a shared mapping
1175 * - this is the hook for quasi-memory character devices to
1176 * tell us the location of a shared mapping
1177 */
1178 if (capabilities & NOMMU_MAP_DIRECT) {
1179 addr = file->f_op->get_unmapped_area(file, addr, len,
1180 pgoff, flags);
1181 if (IS_ERR_VALUE(addr)) {
1182 ret = addr;
1183 if (ret != -ENOSYS)
1184 goto error_just_free;
1185
1186 /* the driver refused to tell us where to site
1187 * the mapping so we'll have to attempt to copy
1188 * it */
1189 ret = -ENODEV;
1190 if (!(capabilities & NOMMU_MAP_COPY))
1191 goto error_just_free;
1192
1193 capabilities &= ~NOMMU_MAP_DIRECT;
1194 } else {
1195 vma->vm_start = region->vm_start = addr;
1196 vma->vm_end = region->vm_end = addr + len;
1197 }
1198 }
1199 }
1200
1201 vma->vm_region = region;
1202
1203 /* set up the mapping
1204 * - the region is filled in if NOMMU_MAP_DIRECT is still set
1205 */
1206 if (file && vma->vm_flags & VM_SHARED)
1207 ret = do_mmap_shared_file(vma);
1208 else
1209 ret = do_mmap_private(vma, region, len, capabilities);
1210 if (ret < 0)
1211 goto error_just_free;
1212 add_nommu_region(region);
1213
1214 /* clear anonymous mappings that don't ask for uninitialized data */
1215 if (!vma->vm_file &&
1216 (!IS_ENABLED(CONFIG_MMAP_ALLOW_UNINITIALIZED) ||
1217 !(flags & MAP_UNINITIALIZED)))
1218 memset((void *)region->vm_start, 0,
1219 region->vm_end - region->vm_start);
1220
1221 /* okay... we have a mapping; now we have to register it */
1222 result = vma->vm_start;
1223
1224 current->mm->total_vm += len >> PAGE_SHIFT;
1225
1226share:
1227 mas_add_vma_to_mm(&mas, current->mm, vma);
1228
1229 /* we flush the region from the icache only when the first executable
1230 * mapping of it is made */
1231 if (vma->vm_flags & VM_EXEC && !region->vm_icache_flushed) {
1232 flush_icache_user_range(region->vm_start, region->vm_end);
1233 region->vm_icache_flushed = true;
1234 }
1235
1236 up_write(&nommu_region_sem);
1237
1238 return result;
1239
1240error_just_free:
1241 up_write(&nommu_region_sem);
1242error:
1243 mas_destroy(&mas);
1244 if (region->vm_file)
1245 fput(region->vm_file);
1246 kmem_cache_free(vm_region_jar, region);
1247 if (vma->vm_file)
1248 fput(vma->vm_file);
1249 vm_area_free(vma);
1250 return ret;
1251
1252sharing_violation:
1253 up_write(&nommu_region_sem);
1254 pr_warn("Attempt to share mismatched mappings\n");
1255 ret = -EINVAL;
1256 goto error;
1257
1258error_getting_vma:
1259 kmem_cache_free(vm_region_jar, region);
1260 pr_warn("Allocation of vma for %lu byte allocation from process %d failed\n",
1261 len, current->pid);
1262 show_free_areas(0, NULL);
1263 return -ENOMEM;
1264
1265error_getting_region:
1266 pr_warn("Allocation of vm region for %lu byte allocation from process %d failed\n",
1267 len, current->pid);
1268 show_free_areas(0, NULL);
1269 return -ENOMEM;
1270
1271error_maple_preallocate:
1272 kmem_cache_free(vm_region_jar, region);
1273 vm_area_free(vma);
1274 pr_warn("Allocation of vma tree for process %d failed\n", current->pid);
1275 show_free_areas(0, NULL);
1276 return -ENOMEM;
1277
1278}
1279
1280unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
1281 unsigned long prot, unsigned long flags,
1282 unsigned long fd, unsigned long pgoff)
1283{
1284 struct file *file = NULL;
1285 unsigned long retval = -EBADF;
1286
1287 audit_mmap_fd(fd, flags);
1288 if (!(flags & MAP_ANONYMOUS)) {
1289 file = fget(fd);
1290 if (!file)
1291 goto out;
1292 }
1293
1294 retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
1295
1296 if (file)
1297 fput(file);
1298out:
1299 return retval;
1300}
1301
1302SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
1303 unsigned long, prot, unsigned long, flags,
1304 unsigned long, fd, unsigned long, pgoff)
1305{
1306 return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
1307}
1308
1309#ifdef __ARCH_WANT_SYS_OLD_MMAP
1310struct mmap_arg_struct {
1311 unsigned long addr;
1312 unsigned long len;
1313 unsigned long prot;
1314 unsigned long flags;
1315 unsigned long fd;
1316 unsigned long offset;
1317};
1318
1319SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
1320{
1321 struct mmap_arg_struct a;
1322
1323 if (copy_from_user(&a, arg, sizeof(a)))
1324 return -EFAULT;
1325 if (offset_in_page(a.offset))
1326 return -EINVAL;
1327
1328 return ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
1329 a.offset >> PAGE_SHIFT);
1330}
1331#endif /* __ARCH_WANT_SYS_OLD_MMAP */
1332
1333/*
1334 * split a vma into two pieces at address 'addr', a new vma is allocated either
1335 * for the first part or the tail.
1336 */
1337int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
1338 unsigned long addr, int new_below)
1339{
1340 struct vm_area_struct *new;
1341 struct vm_region *region;
1342 unsigned long npages;
1343 MA_STATE(mas, &mm->mm_mt, vma->vm_start, vma->vm_end);
1344
1345 /* we're only permitted to split anonymous regions (these should have
1346 * only a single usage on the region) */
1347 if (vma->vm_file)
1348 return -ENOMEM;
1349
1350 mm = vma->vm_mm;
1351 if (mm->map_count >= sysctl_max_map_count)
1352 return -ENOMEM;
1353
1354 region = kmem_cache_alloc(vm_region_jar, GFP_KERNEL);
1355 if (!region)
1356 return -ENOMEM;
1357
1358 new = vm_area_dup(vma);
1359 if (!new)
1360 goto err_vma_dup;
1361
1362 if (mas_preallocate(&mas, vma, GFP_KERNEL)) {
1363 pr_warn("Allocation of vma tree for process %d failed\n",
1364 current->pid);
1365 goto err_mas_preallocate;
1366 }
1367
1368 /* most fields are the same, copy all, and then fixup */
1369 *region = *vma->vm_region;
1370 new->vm_region = region;
1371
1372 npages = (addr - vma->vm_start) >> PAGE_SHIFT;
1373
1374 if (new_below) {
1375 region->vm_top = region->vm_end = new->vm_end = addr;
1376 } else {
1377 region->vm_start = new->vm_start = addr;
1378 region->vm_pgoff = new->vm_pgoff += npages;
1379 }
1380
1381 if (new->vm_ops && new->vm_ops->open)
1382 new->vm_ops->open(new);
1383
1384 down_write(&nommu_region_sem);
1385 delete_nommu_region(vma->vm_region);
1386 if (new_below) {
1387 vma->vm_region->vm_start = vma->vm_start = addr;
1388 vma->vm_region->vm_pgoff = vma->vm_pgoff += npages;
1389 } else {
1390 vma->vm_region->vm_end = vma->vm_end = addr;
1391 vma->vm_region->vm_top = addr;
1392 }
1393 add_nommu_region(vma->vm_region);
1394 add_nommu_region(new->vm_region);
1395 up_write(&nommu_region_sem);
1396
1397 setup_vma_to_mm(vma, mm);
1398 setup_vma_to_mm(new, mm);
1399 mas_set_range(&mas, vma->vm_start, vma->vm_end - 1);
1400 mas_store(&mas, vma);
1401 vma_mas_store(new, &mas);
1402 mm->map_count++;
1403 return 0;
1404
1405err_mas_preallocate:
1406 vm_area_free(new);
1407err_vma_dup:
1408 kmem_cache_free(vm_region_jar, region);
1409 return -ENOMEM;
1410}
1411
1412/*
1413 * shrink a VMA by removing the specified chunk from either the beginning or
1414 * the end
1415 */
1416static int shrink_vma(struct mm_struct *mm,
1417 struct vm_area_struct *vma,
1418 unsigned long from, unsigned long to)
1419{
1420 struct vm_region *region;
1421
1422 /* adjust the VMA's pointers, which may reposition it in the MM's tree
1423 * and list */
1424 if (delete_vma_from_mm(vma))
1425 return -ENOMEM;
1426 if (from > vma->vm_start)
1427 vma->vm_end = from;
1428 else
1429 vma->vm_start = to;
1430 if (add_vma_to_mm(mm, vma))
1431 return -ENOMEM;
1432
1433 /* cut the backing region down to size */
1434 region = vma->vm_region;
1435 BUG_ON(region->vm_usage != 1);
1436
1437 down_write(&nommu_region_sem);
1438 delete_nommu_region(region);
1439 if (from > region->vm_start) {
1440 to = region->vm_top;
1441 region->vm_top = region->vm_end = from;
1442 } else {
1443 region->vm_start = to;
1444 }
1445 add_nommu_region(region);
1446 up_write(&nommu_region_sem);
1447
1448 free_page_series(from, to);
1449 return 0;
1450}
1451
1452/*
1453 * release a mapping
1454 * - under NOMMU conditions the chunk to be unmapped must be backed by a single
1455 * VMA, though it need not cover the whole VMA
1456 */
1457int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, struct list_head *uf)
1458{
1459 MA_STATE(mas, &mm->mm_mt, start, start);
1460 struct vm_area_struct *vma;
1461 unsigned long end;
1462 int ret = 0;
1463
1464 len = PAGE_ALIGN(len);
1465 if (len == 0)
1466 return -EINVAL;
1467
1468 end = start + len;
1469
1470 /* find the first potentially overlapping VMA */
1471 vma = mas_find(&mas, end - 1);
1472 if (!vma) {
1473 static int limit;
1474 if (limit < 5) {
1475 pr_warn("munmap of memory not mmapped by process %d (%s): 0x%lx-0x%lx\n",
1476 current->pid, current->comm,
1477 start, start + len - 1);
1478 limit++;
1479 }
1480 return -EINVAL;
1481 }
1482
1483 /* we're allowed to split an anonymous VMA but not a file-backed one */
1484 if (vma->vm_file) {
1485 do {
1486 if (start > vma->vm_start)
1487 return -EINVAL;
1488 if (end == vma->vm_end)
1489 goto erase_whole_vma;
1490 vma = mas_next(&mas, end - 1);
1491 } while (vma);
1492 return -EINVAL;
1493 } else {
1494 /* the chunk must be a subset of the VMA found */
1495 if (start == vma->vm_start && end == vma->vm_end)
1496 goto erase_whole_vma;
1497 if (start < vma->vm_start || end > vma->vm_end)
1498 return -EINVAL;
1499 if (offset_in_page(start))
1500 return -EINVAL;
1501 if (end != vma->vm_end && offset_in_page(end))
1502 return -EINVAL;
1503 if (start != vma->vm_start && end != vma->vm_end) {
1504 ret = split_vma(mm, vma, start, 1);
1505 if (ret < 0)
1506 return ret;
1507 }
1508 return shrink_vma(mm, vma, start, end);
1509 }
1510
1511erase_whole_vma:
1512 if (delete_vma_from_mm(vma))
1513 ret = -ENOMEM;
1514 else
1515 delete_vma(mm, vma);
1516 return ret;
1517}
1518
1519int vm_munmap(unsigned long addr, size_t len)
1520{
1521 struct mm_struct *mm = current->mm;
1522 int ret;
1523
1524 mmap_write_lock(mm);
1525 ret = do_munmap(mm, addr, len, NULL);
1526 mmap_write_unlock(mm);
1527 return ret;
1528}
1529EXPORT_SYMBOL(vm_munmap);
1530
1531SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
1532{
1533 return vm_munmap(addr, len);
1534}
1535
1536/*
1537 * release all the mappings made in a process's VM space
1538 */
1539void exit_mmap(struct mm_struct *mm)
1540{
1541 VMA_ITERATOR(vmi, mm, 0);
1542 struct vm_area_struct *vma;
1543
1544 if (!mm)
1545 return;
1546
1547 mm->total_vm = 0;
1548
1549 /*
1550 * Lock the mm to avoid assert complaining even though this is the only
1551 * user of the mm
1552 */
1553 mmap_write_lock(mm);
1554 for_each_vma(vmi, vma) {
1555 cleanup_vma_from_mm(vma);
1556 delete_vma(mm, vma);
1557 cond_resched();
1558 }
1559 __mt_destroy(&mm->mm_mt);
1560 mmap_write_unlock(mm);
1561}
1562
1563int vm_brk(unsigned long addr, unsigned long len)
1564{
1565 return -ENOMEM;
1566}
1567
1568/*
1569 * expand (or shrink) an existing mapping, potentially moving it at the same
1570 * time (controlled by the MREMAP_MAYMOVE flag and available VM space)
1571 *
1572 * under NOMMU conditions, we only permit changing a mapping's size, and only
1573 * as long as it stays within the region allocated by do_mmap_private() and the
1574 * block is not shareable
1575 *
1576 * MREMAP_FIXED is not supported under NOMMU conditions
1577 */
1578static unsigned long do_mremap(unsigned long addr,
1579 unsigned long old_len, unsigned long new_len,
1580 unsigned long flags, unsigned long new_addr)
1581{
1582 struct vm_area_struct *vma;
1583
1584 /* insanity checks first */
1585 old_len = PAGE_ALIGN(old_len);
1586 new_len = PAGE_ALIGN(new_len);
1587 if (old_len == 0 || new_len == 0)
1588 return (unsigned long) -EINVAL;
1589
1590 if (offset_in_page(addr))
1591 return -EINVAL;
1592
1593 if (flags & MREMAP_FIXED && new_addr != addr)
1594 return (unsigned long) -EINVAL;
1595
1596 vma = find_vma_exact(current->mm, addr, old_len);
1597 if (!vma)
1598 return (unsigned long) -EINVAL;
1599
1600 if (vma->vm_end != vma->vm_start + old_len)
1601 return (unsigned long) -EFAULT;
1602
1603 if (vma->vm_flags & VM_MAYSHARE)
1604 return (unsigned long) -EPERM;
1605
1606 if (new_len > vma->vm_region->vm_end - vma->vm_region->vm_start)
1607 return (unsigned long) -ENOMEM;
1608
1609 /* all checks complete - do it */
1610 vma->vm_end = vma->vm_start + new_len;
1611 return vma->vm_start;
1612}
1613
1614SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
1615 unsigned long, new_len, unsigned long, flags,
1616 unsigned long, new_addr)
1617{
1618 unsigned long ret;
1619
1620 mmap_write_lock(current->mm);
1621 ret = do_mremap(addr, old_len, new_len, flags, new_addr);
1622 mmap_write_unlock(current->mm);
1623 return ret;
1624}
1625
1626struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
1627 unsigned int foll_flags)
1628{
1629 return NULL;
1630}
1631
1632int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
1633 unsigned long pfn, unsigned long size, pgprot_t prot)
1634{
1635 if (addr != (pfn << PAGE_SHIFT))
1636 return -EINVAL;
1637
1638 vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
1639 return 0;
1640}
1641EXPORT_SYMBOL(remap_pfn_range);
1642
1643int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len)
1644{
1645 unsigned long pfn = start >> PAGE_SHIFT;
1646 unsigned long vm_len = vma->vm_end - vma->vm_start;
1647
1648 pfn += vma->vm_pgoff;
1649 return io_remap_pfn_range(vma, vma->vm_start, pfn, vm_len, vma->vm_page_prot);
1650}
1651EXPORT_SYMBOL(vm_iomap_memory);
1652
1653int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
1654 unsigned long pgoff)
1655{
1656 unsigned int size = vma->vm_end - vma->vm_start;
1657
1658 if (!(vma->vm_flags & VM_USERMAP))
1659 return -EINVAL;
1660
1661 vma->vm_start = (unsigned long)(addr + (pgoff << PAGE_SHIFT));
1662 vma->vm_end = vma->vm_start + size;
1663
1664 return 0;
1665}
1666EXPORT_SYMBOL(remap_vmalloc_range);
1667
1668vm_fault_t filemap_fault(struct vm_fault *vmf)
1669{
1670 BUG();
1671 return 0;
1672}
1673EXPORT_SYMBOL(filemap_fault);
1674
1675vm_fault_t filemap_map_pages(struct vm_fault *vmf,
1676 pgoff_t start_pgoff, pgoff_t end_pgoff)
1677{
1678 BUG();
1679 return 0;
1680}
1681EXPORT_SYMBOL(filemap_map_pages);
1682
1683int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf,
1684 int len, unsigned int gup_flags)
1685{
1686 struct vm_area_struct *vma;
1687 int write = gup_flags & FOLL_WRITE;
1688
1689 if (mmap_read_lock_killable(mm))
1690 return 0;
1691
1692 /* the access must start within one of the target process's mappings */
1693 vma = find_vma(mm, addr);
1694 if (vma) {
1695 /* don't overrun this mapping */
1696 if (addr + len >= vma->vm_end)
1697 len = vma->vm_end - addr;
1698
1699 /* only read or write mappings where it is permitted */
1700 if (write && vma->vm_flags & VM_MAYWRITE)
1701 copy_to_user_page(vma, NULL, addr,
1702 (void *) addr, buf, len);
1703 else if (!write && vma->vm_flags & VM_MAYREAD)
1704 copy_from_user_page(vma, NULL, addr,
1705 buf, (void *) addr, len);
1706 else
1707 len = 0;
1708 } else {
1709 len = 0;
1710 }
1711
1712 mmap_read_unlock(mm);
1713
1714 return len;
1715}
1716
1717/**
1718 * access_remote_vm - access another process' address space
1719 * @mm: the mm_struct of the target address space
1720 * @addr: start address to access
1721 * @buf: source or destination buffer
1722 * @len: number of bytes to transfer
1723 * @gup_flags: flags modifying lookup behaviour
1724 *
1725 * The caller must hold a reference on @mm.
1726 */
1727int access_remote_vm(struct mm_struct *mm, unsigned long addr,
1728 void *buf, int len, unsigned int gup_flags)
1729{
1730 return __access_remote_vm(mm, addr, buf, len, gup_flags);
1731}
1732
1733/*
1734 * Access another process' address space.
1735 * - source/target buffer must be kernel space
1736 */
1737int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len,
1738 unsigned int gup_flags)
1739{
1740 struct mm_struct *mm;
1741
1742 if (addr + len < addr)
1743 return 0;
1744
1745 mm = get_task_mm(tsk);
1746 if (!mm)
1747 return 0;
1748
1749 len = __access_remote_vm(mm, addr, buf, len, gup_flags);
1750
1751 mmput(mm);
1752 return len;
1753}
1754EXPORT_SYMBOL_GPL(access_process_vm);
1755
1756/**
1757 * nommu_shrink_inode_mappings - Shrink the shared mappings on an inode
1758 * @inode: The inode to check
1759 * @size: The current filesize of the inode
1760 * @newsize: The proposed filesize of the inode
1761 *
1762 * Check the shared mappings on an inode on behalf of a shrinking truncate to
1763 * make sure that any outstanding VMAs aren't broken and then shrink the
1764 * vm_regions that extend beyond so that do_mmap() doesn't
1765 * automatically grant mappings that are too large.
1766 */
1767int nommu_shrink_inode_mappings(struct inode *inode, size_t size,
1768 size_t newsize)
1769{
1770 struct vm_area_struct *vma;
1771 struct vm_region *region;
1772 pgoff_t low, high;
1773 size_t r_size, r_top;
1774
1775 low = newsize >> PAGE_SHIFT;
1776 high = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1777
1778 down_write(&nommu_region_sem);
1779 i_mmap_lock_read(inode->i_mapping);
1780
1781 /* search for VMAs that fall within the dead zone */
1782 vma_interval_tree_foreach(vma, &inode->i_mapping->i_mmap, low, high) {
1783 /* found one - only interested if it's shared out of the page
1784 * cache */
1785 if (vma->vm_flags & VM_SHARED) {
1786 i_mmap_unlock_read(inode->i_mapping);
1787 up_write(&nommu_region_sem);
1788 return -ETXTBSY; /* not quite true, but near enough */
1789 }
1790 }
1791
1792 /* reduce any regions that overlap the dead zone - if in existence,
1793 * these will be pointed to by VMAs that don't overlap the dead zone
1794 *
1795 * we don't check for any regions that start beyond the EOF as there
1796 * shouldn't be any
1797 */
1798 vma_interval_tree_foreach(vma, &inode->i_mapping->i_mmap, 0, ULONG_MAX) {
1799 if (!(vma->vm_flags & VM_SHARED))
1800 continue;
1801
1802 region = vma->vm_region;
1803 r_size = region->vm_top - region->vm_start;
1804 r_top = (region->vm_pgoff << PAGE_SHIFT) + r_size;
1805
1806 if (r_top > newsize) {
1807 region->vm_top -= r_top - newsize;
1808 if (region->vm_end > region->vm_top)
1809 region->vm_end = region->vm_top;
1810 }
1811 }
1812
1813 i_mmap_unlock_read(inode->i_mapping);
1814 up_write(&nommu_region_sem);
1815 return 0;
1816}
1817
1818/*
1819 * Initialise sysctl_user_reserve_kbytes.
1820 *
1821 * This is intended to prevent a user from starting a single memory hogging
1822 * process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER
1823 * mode.
1824 *
1825 * The default value is min(3% of free memory, 128MB)
1826 * 128MB is enough to recover with sshd/login, bash, and top/kill.
1827 */
1828static int __meminit init_user_reserve(void)
1829{
1830 unsigned long free_kbytes;
1831
1832 free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
1833
1834 sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17);
1835 return 0;
1836}
1837subsys_initcall(init_user_reserve);
1838
1839/*
1840 * Initialise sysctl_admin_reserve_kbytes.
1841 *
1842 * The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin
1843 * to log in and kill a memory hogging process.
1844 *
1845 * Systems with more than 256MB will reserve 8MB, enough to recover
1846 * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
1847 * only reserve 3% of free pages by default.
1848 */
1849static int __meminit init_admin_reserve(void)
1850{
1851 unsigned long free_kbytes;
1852
1853 free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
1854
1855 sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
1856 return 0;
1857}
1858subsys_initcall(init_admin_reserve);
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/mm/nommu.c
4 *
5 * Replacement code for mm functions to support CPU's that don't
6 * have any form of memory management unit (thus no virtual memory).
7 *
8 * See Documentation/nommu-mmap.txt
9 *
10 * Copyright (c) 2004-2008 David Howells <dhowells@redhat.com>
11 * Copyright (c) 2000-2003 David McCullough <davidm@snapgear.com>
12 * Copyright (c) 2000-2001 D Jeff Dionne <jeff@uClinux.org>
13 * Copyright (c) 2002 Greg Ungerer <gerg@snapgear.com>
14 * Copyright (c) 2007-2010 Paul Mundt <lethal@linux-sh.org>
15 */
16
17#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
18
19#include <linux/export.h>
20#include <linux/mm.h>
21#include <linux/sched/mm.h>
22#include <linux/vmacache.h>
23#include <linux/mman.h>
24#include <linux/swap.h>
25#include <linux/file.h>
26#include <linux/highmem.h>
27#include <linux/pagemap.h>
28#include <linux/slab.h>
29#include <linux/vmalloc.h>
30#include <linux/blkdev.h>
31#include <linux/backing-dev.h>
32#include <linux/compiler.h>
33#include <linux/mount.h>
34#include <linux/personality.h>
35#include <linux/security.h>
36#include <linux/syscalls.h>
37#include <linux/audit.h>
38#include <linux/printk.h>
39
40#include <linux/uaccess.h>
41#include <asm/tlb.h>
42#include <asm/tlbflush.h>
43#include <asm/mmu_context.h>
44#include "internal.h"
45
46void *high_memory;
47EXPORT_SYMBOL(high_memory);
48struct page *mem_map;
49unsigned long max_mapnr;
50EXPORT_SYMBOL(max_mapnr);
51unsigned long highest_memmap_pfn;
52int sysctl_nr_trim_pages = CONFIG_NOMMU_INITIAL_TRIM_EXCESS;
53int heap_stack_gap = 0;
54
55atomic_long_t mmap_pages_allocated;
56
57EXPORT_SYMBOL(mem_map);
58
59/* list of mapped, potentially shareable regions */
60static struct kmem_cache *vm_region_jar;
61struct rb_root nommu_region_tree = RB_ROOT;
62DECLARE_RWSEM(nommu_region_sem);
63
64const struct vm_operations_struct generic_file_vm_ops = {
65};
66
67/*
68 * Return the total memory allocated for this pointer, not
69 * just what the caller asked for.
70 *
71 * Doesn't have to be accurate, i.e. may have races.
72 */
73unsigned int kobjsize(const void *objp)
74{
75 struct page *page;
76
77 /*
78 * If the object we have should not have ksize performed on it,
79 * return size of 0
80 */
81 if (!objp || !virt_addr_valid(objp))
82 return 0;
83
84 page = virt_to_head_page(objp);
85
86 /*
87 * If the allocator sets PageSlab, we know the pointer came from
88 * kmalloc().
89 */
90 if (PageSlab(page))
91 return ksize(objp);
92
93 /*
94 * If it's not a compound page, see if we have a matching VMA
95 * region. This test is intentionally done in reverse order,
96 * so if there's no VMA, we still fall through and hand back
97 * PAGE_SIZE for 0-order pages.
98 */
99 if (!PageCompound(page)) {
100 struct vm_area_struct *vma;
101
102 vma = find_vma(current->mm, (unsigned long)objp);
103 if (vma)
104 return vma->vm_end - vma->vm_start;
105 }
106
107 /*
108 * The ksize() function is only guaranteed to work for pointers
109 * returned by kmalloc(). So handle arbitrary pointers here.
110 */
111 return page_size(page);
112}
113
114/**
115 * follow_pfn - look up PFN at a user virtual address
116 * @vma: memory mapping
117 * @address: user virtual address
118 * @pfn: location to store found PFN
119 *
120 * Only IO mappings and raw PFN mappings are allowed.
121 *
122 * Returns zero and the pfn at @pfn on success, -ve otherwise.
123 */
124int follow_pfn(struct vm_area_struct *vma, unsigned long address,
125 unsigned long *pfn)
126{
127 if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
128 return -EINVAL;
129
130 *pfn = address >> PAGE_SHIFT;
131 return 0;
132}
133EXPORT_SYMBOL(follow_pfn);
134
135LIST_HEAD(vmap_area_list);
136
137void vfree(const void *addr)
138{
139 kfree(addr);
140}
141EXPORT_SYMBOL(vfree);
142
143void *__vmalloc(unsigned long size, gfp_t gfp_mask, pgprot_t prot)
144{
145 /*
146 * You can't specify __GFP_HIGHMEM with kmalloc() since kmalloc()
147 * returns only a logical address.
148 */
149 return kmalloc(size, (gfp_mask | __GFP_COMP) & ~__GFP_HIGHMEM);
150}
151EXPORT_SYMBOL(__vmalloc);
152
153void *__vmalloc_node_flags(unsigned long size, int node, gfp_t flags)
154{
155 return __vmalloc(size, flags, PAGE_KERNEL);
156}
157
158void *vmalloc_user(unsigned long size)
159{
160 void *ret;
161
162 ret = __vmalloc(size, GFP_KERNEL | __GFP_ZERO, PAGE_KERNEL);
163 if (ret) {
164 struct vm_area_struct *vma;
165
166 down_write(¤t->mm->mmap_sem);
167 vma = find_vma(current->mm, (unsigned long)ret);
168 if (vma)
169 vma->vm_flags |= VM_USERMAP;
170 up_write(¤t->mm->mmap_sem);
171 }
172
173 return ret;
174}
175EXPORT_SYMBOL(vmalloc_user);
176
177struct page *vmalloc_to_page(const void *addr)
178{
179 return virt_to_page(addr);
180}
181EXPORT_SYMBOL(vmalloc_to_page);
182
183unsigned long vmalloc_to_pfn(const void *addr)
184{
185 return page_to_pfn(virt_to_page(addr));
186}
187EXPORT_SYMBOL(vmalloc_to_pfn);
188
189long vread(char *buf, char *addr, unsigned long count)
190{
191 /* Don't allow overflow */
192 if ((unsigned long) buf + count < count)
193 count = -(unsigned long) buf;
194
195 memcpy(buf, addr, count);
196 return count;
197}
198
199long vwrite(char *buf, char *addr, unsigned long count)
200{
201 /* Don't allow overflow */
202 if ((unsigned long) addr + count < count)
203 count = -(unsigned long) addr;
204
205 memcpy(addr, buf, count);
206 return count;
207}
208
209/*
210 * vmalloc - allocate virtually contiguous memory
211 *
212 * @size: allocation size
213 *
214 * Allocate enough pages to cover @size from the page level
215 * allocator and map them into contiguous kernel virtual space.
216 *
217 * For tight control over page level allocator and protection flags
218 * use __vmalloc() instead.
219 */
220void *vmalloc(unsigned long size)
221{
222 return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL);
223}
224EXPORT_SYMBOL(vmalloc);
225
226/*
227 * vzalloc - allocate virtually contiguous memory with zero fill
228 *
229 * @size: allocation size
230 *
231 * Allocate enough pages to cover @size from the page level
232 * allocator and map them into contiguous kernel virtual space.
233 * The memory allocated is set to zero.
234 *
235 * For tight control over page level allocator and protection flags
236 * use __vmalloc() instead.
237 */
238void *vzalloc(unsigned long size)
239{
240 return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
241 PAGE_KERNEL);
242}
243EXPORT_SYMBOL(vzalloc);
244
245/**
246 * vmalloc_node - allocate memory on a specific node
247 * @size: allocation size
248 * @node: numa node
249 *
250 * Allocate enough pages to cover @size from the page level
251 * allocator and map them into contiguous kernel virtual space.
252 *
253 * For tight control over page level allocator and protection flags
254 * use __vmalloc() instead.
255 */
256void *vmalloc_node(unsigned long size, int node)
257{
258 return vmalloc(size);
259}
260EXPORT_SYMBOL(vmalloc_node);
261
262/**
263 * vzalloc_node - allocate memory on a specific node with zero fill
264 * @size: allocation size
265 * @node: numa node
266 *
267 * Allocate enough pages to cover @size from the page level
268 * allocator and map them into contiguous kernel virtual space.
269 * The memory allocated is set to zero.
270 *
271 * For tight control over page level allocator and protection flags
272 * use __vmalloc() instead.
273 */
274void *vzalloc_node(unsigned long size, int node)
275{
276 return vzalloc(size);
277}
278EXPORT_SYMBOL(vzalloc_node);
279
280/**
281 * vmalloc_exec - allocate virtually contiguous, executable memory
282 * @size: allocation size
283 *
284 * Kernel-internal function to allocate enough pages to cover @size
285 * the page level allocator and map them into contiguous and
286 * executable kernel virtual space.
287 *
288 * For tight control over page level allocator and protection flags
289 * use __vmalloc() instead.
290 */
291
292void *vmalloc_exec(unsigned long size)
293{
294 return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL_EXEC);
295}
296
297/**
298 * vmalloc_32 - allocate virtually contiguous memory (32bit addressable)
299 * @size: allocation size
300 *
301 * Allocate enough 32bit PA addressable pages to cover @size from the
302 * page level allocator and map them into contiguous kernel virtual space.
303 */
304void *vmalloc_32(unsigned long size)
305{
306 return __vmalloc(size, GFP_KERNEL, PAGE_KERNEL);
307}
308EXPORT_SYMBOL(vmalloc_32);
309
310/**
311 * vmalloc_32_user - allocate zeroed virtually contiguous 32bit memory
312 * @size: allocation size
313 *
314 * The resulting memory area is 32bit addressable and zeroed so it can be
315 * mapped to userspace without leaking data.
316 *
317 * VM_USERMAP is set on the corresponding VMA so that subsequent calls to
318 * remap_vmalloc_range() are permissible.
319 */
320void *vmalloc_32_user(unsigned long size)
321{
322 /*
323 * We'll have to sort out the ZONE_DMA bits for 64-bit,
324 * but for now this can simply use vmalloc_user() directly.
325 */
326 return vmalloc_user(size);
327}
328EXPORT_SYMBOL(vmalloc_32_user);
329
330void *vmap(struct page **pages, unsigned int count, unsigned long flags, pgprot_t prot)
331{
332 BUG();
333 return NULL;
334}
335EXPORT_SYMBOL(vmap);
336
337void vunmap(const void *addr)
338{
339 BUG();
340}
341EXPORT_SYMBOL(vunmap);
342
343void *vm_map_ram(struct page **pages, unsigned int count, int node, pgprot_t prot)
344{
345 BUG();
346 return NULL;
347}
348EXPORT_SYMBOL(vm_map_ram);
349
350void vm_unmap_ram(const void *mem, unsigned int count)
351{
352 BUG();
353}
354EXPORT_SYMBOL(vm_unmap_ram);
355
356void vm_unmap_aliases(void)
357{
358}
359EXPORT_SYMBOL_GPL(vm_unmap_aliases);
360
361/*
362 * Implement a stub for vmalloc_sync_all() if the architecture chose not to
363 * have one.
364 */
365void __weak vmalloc_sync_all(void)
366{
367}
368
369struct vm_struct *alloc_vm_area(size_t size, pte_t **ptes)
370{
371 BUG();
372 return NULL;
373}
374EXPORT_SYMBOL_GPL(alloc_vm_area);
375
376void free_vm_area(struct vm_struct *area)
377{
378 BUG();
379}
380EXPORT_SYMBOL_GPL(free_vm_area);
381
382int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
383 struct page *page)
384{
385 return -EINVAL;
386}
387EXPORT_SYMBOL(vm_insert_page);
388
389int vm_map_pages(struct vm_area_struct *vma, struct page **pages,
390 unsigned long num)
391{
392 return -EINVAL;
393}
394EXPORT_SYMBOL(vm_map_pages);
395
396int vm_map_pages_zero(struct vm_area_struct *vma, struct page **pages,
397 unsigned long num)
398{
399 return -EINVAL;
400}
401EXPORT_SYMBOL(vm_map_pages_zero);
402
403/*
404 * sys_brk() for the most part doesn't need the global kernel
405 * lock, except when an application is doing something nasty
406 * like trying to un-brk an area that has already been mapped
407 * to a regular file. in this case, the unmapping will need
408 * to invoke file system routines that need the global lock.
409 */
410SYSCALL_DEFINE1(brk, unsigned long, brk)
411{
412 struct mm_struct *mm = current->mm;
413
414 if (brk < mm->start_brk || brk > mm->context.end_brk)
415 return mm->brk;
416
417 if (mm->brk == brk)
418 return mm->brk;
419
420 /*
421 * Always allow shrinking brk
422 */
423 if (brk <= mm->brk) {
424 mm->brk = brk;
425 return brk;
426 }
427
428 /*
429 * Ok, looks good - let it rip.
430 */
431 flush_icache_range(mm->brk, brk);
432 return mm->brk = brk;
433}
434
435/*
436 * initialise the percpu counter for VM and region record slabs
437 */
438void __init mmap_init(void)
439{
440 int ret;
441
442 ret = percpu_counter_init(&vm_committed_as, 0, GFP_KERNEL);
443 VM_BUG_ON(ret);
444 vm_region_jar = KMEM_CACHE(vm_region, SLAB_PANIC|SLAB_ACCOUNT);
445}
446
447/*
448 * validate the region tree
449 * - the caller must hold the region lock
450 */
451#ifdef CONFIG_DEBUG_NOMMU_REGIONS
452static noinline void validate_nommu_regions(void)
453{
454 struct vm_region *region, *last;
455 struct rb_node *p, *lastp;
456
457 lastp = rb_first(&nommu_region_tree);
458 if (!lastp)
459 return;
460
461 last = rb_entry(lastp, struct vm_region, vm_rb);
462 BUG_ON(last->vm_end <= last->vm_start);
463 BUG_ON(last->vm_top < last->vm_end);
464
465 while ((p = rb_next(lastp))) {
466 region = rb_entry(p, struct vm_region, vm_rb);
467 last = rb_entry(lastp, struct vm_region, vm_rb);
468
469 BUG_ON(region->vm_end <= region->vm_start);
470 BUG_ON(region->vm_top < region->vm_end);
471 BUG_ON(region->vm_start < last->vm_top);
472
473 lastp = p;
474 }
475}
476#else
477static void validate_nommu_regions(void)
478{
479}
480#endif
481
482/*
483 * add a region into the global tree
484 */
485static void add_nommu_region(struct vm_region *region)
486{
487 struct vm_region *pregion;
488 struct rb_node **p, *parent;
489
490 validate_nommu_regions();
491
492 parent = NULL;
493 p = &nommu_region_tree.rb_node;
494 while (*p) {
495 parent = *p;
496 pregion = rb_entry(parent, struct vm_region, vm_rb);
497 if (region->vm_start < pregion->vm_start)
498 p = &(*p)->rb_left;
499 else if (region->vm_start > pregion->vm_start)
500 p = &(*p)->rb_right;
501 else if (pregion == region)
502 return;
503 else
504 BUG();
505 }
506
507 rb_link_node(®ion->vm_rb, parent, p);
508 rb_insert_color(®ion->vm_rb, &nommu_region_tree);
509
510 validate_nommu_regions();
511}
512
513/*
514 * delete a region from the global tree
515 */
516static void delete_nommu_region(struct vm_region *region)
517{
518 BUG_ON(!nommu_region_tree.rb_node);
519
520 validate_nommu_regions();
521 rb_erase(®ion->vm_rb, &nommu_region_tree);
522 validate_nommu_regions();
523}
524
525/*
526 * free a contiguous series of pages
527 */
528static void free_page_series(unsigned long from, unsigned long to)
529{
530 for (; from < to; from += PAGE_SIZE) {
531 struct page *page = virt_to_page(from);
532
533 atomic_long_dec(&mmap_pages_allocated);
534 put_page(page);
535 }
536}
537
538/*
539 * release a reference to a region
540 * - the caller must hold the region semaphore for writing, which this releases
541 * - the region may not have been added to the tree yet, in which case vm_top
542 * will equal vm_start
543 */
544static void __put_nommu_region(struct vm_region *region)
545 __releases(nommu_region_sem)
546{
547 BUG_ON(!nommu_region_tree.rb_node);
548
549 if (--region->vm_usage == 0) {
550 if (region->vm_top > region->vm_start)
551 delete_nommu_region(region);
552 up_write(&nommu_region_sem);
553
554 if (region->vm_file)
555 fput(region->vm_file);
556
557 /* IO memory and memory shared directly out of the pagecache
558 * from ramfs/tmpfs mustn't be released here */
559 if (region->vm_flags & VM_MAPPED_COPY)
560 free_page_series(region->vm_start, region->vm_top);
561 kmem_cache_free(vm_region_jar, region);
562 } else {
563 up_write(&nommu_region_sem);
564 }
565}
566
567/*
568 * release a reference to a region
569 */
570static void put_nommu_region(struct vm_region *region)
571{
572 down_write(&nommu_region_sem);
573 __put_nommu_region(region);
574}
575
576/*
577 * add a VMA into a process's mm_struct in the appropriate place in the list
578 * and tree and add to the address space's page tree also if not an anonymous
579 * page
580 * - should be called with mm->mmap_sem held writelocked
581 */
582static void add_vma_to_mm(struct mm_struct *mm, struct vm_area_struct *vma)
583{
584 struct vm_area_struct *pvma, *prev;
585 struct address_space *mapping;
586 struct rb_node **p, *parent, *rb_prev;
587
588 BUG_ON(!vma->vm_region);
589
590 mm->map_count++;
591 vma->vm_mm = mm;
592
593 /* add the VMA to the mapping */
594 if (vma->vm_file) {
595 mapping = vma->vm_file->f_mapping;
596
597 i_mmap_lock_write(mapping);
598 flush_dcache_mmap_lock(mapping);
599 vma_interval_tree_insert(vma, &mapping->i_mmap);
600 flush_dcache_mmap_unlock(mapping);
601 i_mmap_unlock_write(mapping);
602 }
603
604 /* add the VMA to the tree */
605 parent = rb_prev = NULL;
606 p = &mm->mm_rb.rb_node;
607 while (*p) {
608 parent = *p;
609 pvma = rb_entry(parent, struct vm_area_struct, vm_rb);
610
611 /* sort by: start addr, end addr, VMA struct addr in that order
612 * (the latter is necessary as we may get identical VMAs) */
613 if (vma->vm_start < pvma->vm_start)
614 p = &(*p)->rb_left;
615 else if (vma->vm_start > pvma->vm_start) {
616 rb_prev = parent;
617 p = &(*p)->rb_right;
618 } else if (vma->vm_end < pvma->vm_end)
619 p = &(*p)->rb_left;
620 else if (vma->vm_end > pvma->vm_end) {
621 rb_prev = parent;
622 p = &(*p)->rb_right;
623 } else if (vma < pvma)
624 p = &(*p)->rb_left;
625 else if (vma > pvma) {
626 rb_prev = parent;
627 p = &(*p)->rb_right;
628 } else
629 BUG();
630 }
631
632 rb_link_node(&vma->vm_rb, parent, p);
633 rb_insert_color(&vma->vm_rb, &mm->mm_rb);
634
635 /* add VMA to the VMA list also */
636 prev = NULL;
637 if (rb_prev)
638 prev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
639
640 __vma_link_list(mm, vma, prev, parent);
641}
642
643/*
644 * delete a VMA from its owning mm_struct and address space
645 */
646static void delete_vma_from_mm(struct vm_area_struct *vma)
647{
648 int i;
649 struct address_space *mapping;
650 struct mm_struct *mm = vma->vm_mm;
651 struct task_struct *curr = current;
652
653 mm->map_count--;
654 for (i = 0; i < VMACACHE_SIZE; i++) {
655 /* if the vma is cached, invalidate the entire cache */
656 if (curr->vmacache.vmas[i] == vma) {
657 vmacache_invalidate(mm);
658 break;
659 }
660 }
661
662 /* remove the VMA from the mapping */
663 if (vma->vm_file) {
664 mapping = vma->vm_file->f_mapping;
665
666 i_mmap_lock_write(mapping);
667 flush_dcache_mmap_lock(mapping);
668 vma_interval_tree_remove(vma, &mapping->i_mmap);
669 flush_dcache_mmap_unlock(mapping);
670 i_mmap_unlock_write(mapping);
671 }
672
673 /* remove from the MM's tree and list */
674 rb_erase(&vma->vm_rb, &mm->mm_rb);
675
676 if (vma->vm_prev)
677 vma->vm_prev->vm_next = vma->vm_next;
678 else
679 mm->mmap = vma->vm_next;
680
681 if (vma->vm_next)
682 vma->vm_next->vm_prev = vma->vm_prev;
683}
684
685/*
686 * destroy a VMA record
687 */
688static void delete_vma(struct mm_struct *mm, struct vm_area_struct *vma)
689{
690 if (vma->vm_ops && vma->vm_ops->close)
691 vma->vm_ops->close(vma);
692 if (vma->vm_file)
693 fput(vma->vm_file);
694 put_nommu_region(vma->vm_region);
695 vm_area_free(vma);
696}
697
698/*
699 * look up the first VMA in which addr resides, NULL if none
700 * - should be called with mm->mmap_sem at least held readlocked
701 */
702struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
703{
704 struct vm_area_struct *vma;
705
706 /* check the cache first */
707 vma = vmacache_find(mm, addr);
708 if (likely(vma))
709 return vma;
710
711 /* trawl the list (there may be multiple mappings in which addr
712 * resides) */
713 for (vma = mm->mmap; vma; vma = vma->vm_next) {
714 if (vma->vm_start > addr)
715 return NULL;
716 if (vma->vm_end > addr) {
717 vmacache_update(addr, vma);
718 return vma;
719 }
720 }
721
722 return NULL;
723}
724EXPORT_SYMBOL(find_vma);
725
726/*
727 * find a VMA
728 * - we don't extend stack VMAs under NOMMU conditions
729 */
730struct vm_area_struct *find_extend_vma(struct mm_struct *mm, unsigned long addr)
731{
732 return find_vma(mm, addr);
733}
734
735/*
736 * expand a stack to a given address
737 * - not supported under NOMMU conditions
738 */
739int expand_stack(struct vm_area_struct *vma, unsigned long address)
740{
741 return -ENOMEM;
742}
743
744/*
745 * look up the first VMA exactly that exactly matches addr
746 * - should be called with mm->mmap_sem at least held readlocked
747 */
748static struct vm_area_struct *find_vma_exact(struct mm_struct *mm,
749 unsigned long addr,
750 unsigned long len)
751{
752 struct vm_area_struct *vma;
753 unsigned long end = addr + len;
754
755 /* check the cache first */
756 vma = vmacache_find_exact(mm, addr, end);
757 if (vma)
758 return vma;
759
760 /* trawl the list (there may be multiple mappings in which addr
761 * resides) */
762 for (vma = mm->mmap; vma; vma = vma->vm_next) {
763 if (vma->vm_start < addr)
764 continue;
765 if (vma->vm_start > addr)
766 return NULL;
767 if (vma->vm_end == end) {
768 vmacache_update(addr, vma);
769 return vma;
770 }
771 }
772
773 return NULL;
774}
775
776/*
777 * determine whether a mapping should be permitted and, if so, what sort of
778 * mapping we're capable of supporting
779 */
780static int validate_mmap_request(struct file *file,
781 unsigned long addr,
782 unsigned long len,
783 unsigned long prot,
784 unsigned long flags,
785 unsigned long pgoff,
786 unsigned long *_capabilities)
787{
788 unsigned long capabilities, rlen;
789 int ret;
790
791 /* do the simple checks first */
792 if (flags & MAP_FIXED)
793 return -EINVAL;
794
795 if ((flags & MAP_TYPE) != MAP_PRIVATE &&
796 (flags & MAP_TYPE) != MAP_SHARED)
797 return -EINVAL;
798
799 if (!len)
800 return -EINVAL;
801
802 /* Careful about overflows.. */
803 rlen = PAGE_ALIGN(len);
804 if (!rlen || rlen > TASK_SIZE)
805 return -ENOMEM;
806
807 /* offset overflow? */
808 if ((pgoff + (rlen >> PAGE_SHIFT)) < pgoff)
809 return -EOVERFLOW;
810
811 if (file) {
812 /* files must support mmap */
813 if (!file->f_op->mmap)
814 return -ENODEV;
815
816 /* work out if what we've got could possibly be shared
817 * - we support chardevs that provide their own "memory"
818 * - we support files/blockdevs that are memory backed
819 */
820 if (file->f_op->mmap_capabilities) {
821 capabilities = file->f_op->mmap_capabilities(file);
822 } else {
823 /* no explicit capabilities set, so assume some
824 * defaults */
825 switch (file_inode(file)->i_mode & S_IFMT) {
826 case S_IFREG:
827 case S_IFBLK:
828 capabilities = NOMMU_MAP_COPY;
829 break;
830
831 case S_IFCHR:
832 capabilities =
833 NOMMU_MAP_DIRECT |
834 NOMMU_MAP_READ |
835 NOMMU_MAP_WRITE;
836 break;
837
838 default:
839 return -EINVAL;
840 }
841 }
842
843 /* eliminate any capabilities that we can't support on this
844 * device */
845 if (!file->f_op->get_unmapped_area)
846 capabilities &= ~NOMMU_MAP_DIRECT;
847 if (!(file->f_mode & FMODE_CAN_READ))
848 capabilities &= ~NOMMU_MAP_COPY;
849
850 /* The file shall have been opened with read permission. */
851 if (!(file->f_mode & FMODE_READ))
852 return -EACCES;
853
854 if (flags & MAP_SHARED) {
855 /* do checks for writing, appending and locking */
856 if ((prot & PROT_WRITE) &&
857 !(file->f_mode & FMODE_WRITE))
858 return -EACCES;
859
860 if (IS_APPEND(file_inode(file)) &&
861 (file->f_mode & FMODE_WRITE))
862 return -EACCES;
863
864 if (locks_verify_locked(file))
865 return -EAGAIN;
866
867 if (!(capabilities & NOMMU_MAP_DIRECT))
868 return -ENODEV;
869
870 /* we mustn't privatise shared mappings */
871 capabilities &= ~NOMMU_MAP_COPY;
872 } else {
873 /* we're going to read the file into private memory we
874 * allocate */
875 if (!(capabilities & NOMMU_MAP_COPY))
876 return -ENODEV;
877
878 /* we don't permit a private writable mapping to be
879 * shared with the backing device */
880 if (prot & PROT_WRITE)
881 capabilities &= ~NOMMU_MAP_DIRECT;
882 }
883
884 if (capabilities & NOMMU_MAP_DIRECT) {
885 if (((prot & PROT_READ) && !(capabilities & NOMMU_MAP_READ)) ||
886 ((prot & PROT_WRITE) && !(capabilities & NOMMU_MAP_WRITE)) ||
887 ((prot & PROT_EXEC) && !(capabilities & NOMMU_MAP_EXEC))
888 ) {
889 capabilities &= ~NOMMU_MAP_DIRECT;
890 if (flags & MAP_SHARED) {
891 pr_warn("MAP_SHARED not completely supported on !MMU\n");
892 return -EINVAL;
893 }
894 }
895 }
896
897 /* handle executable mappings and implied executable
898 * mappings */
899 if (path_noexec(&file->f_path)) {
900 if (prot & PROT_EXEC)
901 return -EPERM;
902 } else if ((prot & PROT_READ) && !(prot & PROT_EXEC)) {
903 /* handle implication of PROT_EXEC by PROT_READ */
904 if (current->personality & READ_IMPLIES_EXEC) {
905 if (capabilities & NOMMU_MAP_EXEC)
906 prot |= PROT_EXEC;
907 }
908 } else if ((prot & PROT_READ) &&
909 (prot & PROT_EXEC) &&
910 !(capabilities & NOMMU_MAP_EXEC)
911 ) {
912 /* backing file is not executable, try to copy */
913 capabilities &= ~NOMMU_MAP_DIRECT;
914 }
915 } else {
916 /* anonymous mappings are always memory backed and can be
917 * privately mapped
918 */
919 capabilities = NOMMU_MAP_COPY;
920
921 /* handle PROT_EXEC implication by PROT_READ */
922 if ((prot & PROT_READ) &&
923 (current->personality & READ_IMPLIES_EXEC))
924 prot |= PROT_EXEC;
925 }
926
927 /* allow the security API to have its say */
928 ret = security_mmap_addr(addr);
929 if (ret < 0)
930 return ret;
931
932 /* looks okay */
933 *_capabilities = capabilities;
934 return 0;
935}
936
937/*
938 * we've determined that we can make the mapping, now translate what we
939 * now know into VMA flags
940 */
941static unsigned long determine_vm_flags(struct file *file,
942 unsigned long prot,
943 unsigned long flags,
944 unsigned long capabilities)
945{
946 unsigned long vm_flags;
947
948 vm_flags = calc_vm_prot_bits(prot, 0) | calc_vm_flag_bits(flags);
949 /* vm_flags |= mm->def_flags; */
950
951 if (!(capabilities & NOMMU_MAP_DIRECT)) {
952 /* attempt to share read-only copies of mapped file chunks */
953 vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
954 if (file && !(prot & PROT_WRITE))
955 vm_flags |= VM_MAYSHARE;
956 } else {
957 /* overlay a shareable mapping on the backing device or inode
958 * if possible - used for chardevs, ramfs/tmpfs/shmfs and
959 * romfs/cramfs */
960 vm_flags |= VM_MAYSHARE | (capabilities & NOMMU_VMFLAGS);
961 if (flags & MAP_SHARED)
962 vm_flags |= VM_SHARED;
963 }
964
965 /* refuse to let anyone share private mappings with this process if
966 * it's being traced - otherwise breakpoints set in it may interfere
967 * with another untraced process
968 */
969 if ((flags & MAP_PRIVATE) && current->ptrace)
970 vm_flags &= ~VM_MAYSHARE;
971
972 return vm_flags;
973}
974
975/*
976 * set up a shared mapping on a file (the driver or filesystem provides and
977 * pins the storage)
978 */
979static int do_mmap_shared_file(struct vm_area_struct *vma)
980{
981 int ret;
982
983 ret = call_mmap(vma->vm_file, vma);
984 if (ret == 0) {
985 vma->vm_region->vm_top = vma->vm_region->vm_end;
986 return 0;
987 }
988 if (ret != -ENOSYS)
989 return ret;
990
991 /* getting -ENOSYS indicates that direct mmap isn't possible (as
992 * opposed to tried but failed) so we can only give a suitable error as
993 * it's not possible to make a private copy if MAP_SHARED was given */
994 return -ENODEV;
995}
996
997/*
998 * set up a private mapping or an anonymous shared mapping
999 */
1000static int do_mmap_private(struct vm_area_struct *vma,
1001 struct vm_region *region,
1002 unsigned long len,
1003 unsigned long capabilities)
1004{
1005 unsigned long total, point;
1006 void *base;
1007 int ret, order;
1008
1009 /* invoke the file's mapping function so that it can keep track of
1010 * shared mappings on devices or memory
1011 * - VM_MAYSHARE will be set if it may attempt to share
1012 */
1013 if (capabilities & NOMMU_MAP_DIRECT) {
1014 ret = call_mmap(vma->vm_file, vma);
1015 if (ret == 0) {
1016 /* shouldn't return success if we're not sharing */
1017 BUG_ON(!(vma->vm_flags & VM_MAYSHARE));
1018 vma->vm_region->vm_top = vma->vm_region->vm_end;
1019 return 0;
1020 }
1021 if (ret != -ENOSYS)
1022 return ret;
1023
1024 /* getting an ENOSYS error indicates that direct mmap isn't
1025 * possible (as opposed to tried but failed) so we'll try to
1026 * make a private copy of the data and map that instead */
1027 }
1028
1029
1030 /* allocate some memory to hold the mapping
1031 * - note that this may not return a page-aligned address if the object
1032 * we're allocating is smaller than a page
1033 */
1034 order = get_order(len);
1035 total = 1 << order;
1036 point = len >> PAGE_SHIFT;
1037
1038 /* we don't want to allocate a power-of-2 sized page set */
1039 if (sysctl_nr_trim_pages && total - point >= sysctl_nr_trim_pages)
1040 total = point;
1041
1042 base = alloc_pages_exact(total << PAGE_SHIFT, GFP_KERNEL);
1043 if (!base)
1044 goto enomem;
1045
1046 atomic_long_add(total, &mmap_pages_allocated);
1047
1048 region->vm_flags = vma->vm_flags |= VM_MAPPED_COPY;
1049 region->vm_start = (unsigned long) base;
1050 region->vm_end = region->vm_start + len;
1051 region->vm_top = region->vm_start + (total << PAGE_SHIFT);
1052
1053 vma->vm_start = region->vm_start;
1054 vma->vm_end = region->vm_start + len;
1055
1056 if (vma->vm_file) {
1057 /* read the contents of a file into the copy */
1058 loff_t fpos;
1059
1060 fpos = vma->vm_pgoff;
1061 fpos <<= PAGE_SHIFT;
1062
1063 ret = kernel_read(vma->vm_file, base, len, &fpos);
1064 if (ret < 0)
1065 goto error_free;
1066
1067 /* clear the last little bit */
1068 if (ret < len)
1069 memset(base + ret, 0, len - ret);
1070
1071 } else {
1072 vma_set_anonymous(vma);
1073 }
1074
1075 return 0;
1076
1077error_free:
1078 free_page_series(region->vm_start, region->vm_top);
1079 region->vm_start = vma->vm_start = 0;
1080 region->vm_end = vma->vm_end = 0;
1081 region->vm_top = 0;
1082 return ret;
1083
1084enomem:
1085 pr_err("Allocation of length %lu from process %d (%s) failed\n",
1086 len, current->pid, current->comm);
1087 show_free_areas(0, NULL);
1088 return -ENOMEM;
1089}
1090
1091/*
1092 * handle mapping creation for uClinux
1093 */
1094unsigned long do_mmap(struct file *file,
1095 unsigned long addr,
1096 unsigned long len,
1097 unsigned long prot,
1098 unsigned long flags,
1099 vm_flags_t vm_flags,
1100 unsigned long pgoff,
1101 unsigned long *populate,
1102 struct list_head *uf)
1103{
1104 struct vm_area_struct *vma;
1105 struct vm_region *region;
1106 struct rb_node *rb;
1107 unsigned long capabilities, result;
1108 int ret;
1109
1110 *populate = 0;
1111
1112 /* decide whether we should attempt the mapping, and if so what sort of
1113 * mapping */
1114 ret = validate_mmap_request(file, addr, len, prot, flags, pgoff,
1115 &capabilities);
1116 if (ret < 0)
1117 return ret;
1118
1119 /* we ignore the address hint */
1120 addr = 0;
1121 len = PAGE_ALIGN(len);
1122
1123 /* we've determined that we can make the mapping, now translate what we
1124 * now know into VMA flags */
1125 vm_flags |= determine_vm_flags(file, prot, flags, capabilities);
1126
1127 /* we're going to need to record the mapping */
1128 region = kmem_cache_zalloc(vm_region_jar, GFP_KERNEL);
1129 if (!region)
1130 goto error_getting_region;
1131
1132 vma = vm_area_alloc(current->mm);
1133 if (!vma)
1134 goto error_getting_vma;
1135
1136 region->vm_usage = 1;
1137 region->vm_flags = vm_flags;
1138 region->vm_pgoff = pgoff;
1139
1140 vma->vm_flags = vm_flags;
1141 vma->vm_pgoff = pgoff;
1142
1143 if (file) {
1144 region->vm_file = get_file(file);
1145 vma->vm_file = get_file(file);
1146 }
1147
1148 down_write(&nommu_region_sem);
1149
1150 /* if we want to share, we need to check for regions created by other
1151 * mmap() calls that overlap with our proposed mapping
1152 * - we can only share with a superset match on most regular files
1153 * - shared mappings on character devices and memory backed files are
1154 * permitted to overlap inexactly as far as we are concerned for in
1155 * these cases, sharing is handled in the driver or filesystem rather
1156 * than here
1157 */
1158 if (vm_flags & VM_MAYSHARE) {
1159 struct vm_region *pregion;
1160 unsigned long pglen, rpglen, pgend, rpgend, start;
1161
1162 pglen = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1163 pgend = pgoff + pglen;
1164
1165 for (rb = rb_first(&nommu_region_tree); rb; rb = rb_next(rb)) {
1166 pregion = rb_entry(rb, struct vm_region, vm_rb);
1167
1168 if (!(pregion->vm_flags & VM_MAYSHARE))
1169 continue;
1170
1171 /* search for overlapping mappings on the same file */
1172 if (file_inode(pregion->vm_file) !=
1173 file_inode(file))
1174 continue;
1175
1176 if (pregion->vm_pgoff >= pgend)
1177 continue;
1178
1179 rpglen = pregion->vm_end - pregion->vm_start;
1180 rpglen = (rpglen + PAGE_SIZE - 1) >> PAGE_SHIFT;
1181 rpgend = pregion->vm_pgoff + rpglen;
1182 if (pgoff >= rpgend)
1183 continue;
1184
1185 /* handle inexactly overlapping matches between
1186 * mappings */
1187 if ((pregion->vm_pgoff != pgoff || rpglen != pglen) &&
1188 !(pgoff >= pregion->vm_pgoff && pgend <= rpgend)) {
1189 /* new mapping is not a subset of the region */
1190 if (!(capabilities & NOMMU_MAP_DIRECT))
1191 goto sharing_violation;
1192 continue;
1193 }
1194
1195 /* we've found a region we can share */
1196 pregion->vm_usage++;
1197 vma->vm_region = pregion;
1198 start = pregion->vm_start;
1199 start += (pgoff - pregion->vm_pgoff) << PAGE_SHIFT;
1200 vma->vm_start = start;
1201 vma->vm_end = start + len;
1202
1203 if (pregion->vm_flags & VM_MAPPED_COPY)
1204 vma->vm_flags |= VM_MAPPED_COPY;
1205 else {
1206 ret = do_mmap_shared_file(vma);
1207 if (ret < 0) {
1208 vma->vm_region = NULL;
1209 vma->vm_start = 0;
1210 vma->vm_end = 0;
1211 pregion->vm_usage--;
1212 pregion = NULL;
1213 goto error_just_free;
1214 }
1215 }
1216 fput(region->vm_file);
1217 kmem_cache_free(vm_region_jar, region);
1218 region = pregion;
1219 result = start;
1220 goto share;
1221 }
1222
1223 /* obtain the address at which to make a shared mapping
1224 * - this is the hook for quasi-memory character devices to
1225 * tell us the location of a shared mapping
1226 */
1227 if (capabilities & NOMMU_MAP_DIRECT) {
1228 addr = file->f_op->get_unmapped_area(file, addr, len,
1229 pgoff, flags);
1230 if (IS_ERR_VALUE(addr)) {
1231 ret = addr;
1232 if (ret != -ENOSYS)
1233 goto error_just_free;
1234
1235 /* the driver refused to tell us where to site
1236 * the mapping so we'll have to attempt to copy
1237 * it */
1238 ret = -ENODEV;
1239 if (!(capabilities & NOMMU_MAP_COPY))
1240 goto error_just_free;
1241
1242 capabilities &= ~NOMMU_MAP_DIRECT;
1243 } else {
1244 vma->vm_start = region->vm_start = addr;
1245 vma->vm_end = region->vm_end = addr + len;
1246 }
1247 }
1248 }
1249
1250 vma->vm_region = region;
1251
1252 /* set up the mapping
1253 * - the region is filled in if NOMMU_MAP_DIRECT is still set
1254 */
1255 if (file && vma->vm_flags & VM_SHARED)
1256 ret = do_mmap_shared_file(vma);
1257 else
1258 ret = do_mmap_private(vma, region, len, capabilities);
1259 if (ret < 0)
1260 goto error_just_free;
1261 add_nommu_region(region);
1262
1263 /* clear anonymous mappings that don't ask for uninitialized data */
1264 if (!vma->vm_file &&
1265 (!IS_ENABLED(CONFIG_MMAP_ALLOW_UNINITIALIZED) ||
1266 !(flags & MAP_UNINITIALIZED)))
1267 memset((void *)region->vm_start, 0,
1268 region->vm_end - region->vm_start);
1269
1270 /* okay... we have a mapping; now we have to register it */
1271 result = vma->vm_start;
1272
1273 current->mm->total_vm += len >> PAGE_SHIFT;
1274
1275share:
1276 add_vma_to_mm(current->mm, vma);
1277
1278 /* we flush the region from the icache only when the first executable
1279 * mapping of it is made */
1280 if (vma->vm_flags & VM_EXEC && !region->vm_icache_flushed) {
1281 flush_icache_range(region->vm_start, region->vm_end);
1282 region->vm_icache_flushed = true;
1283 }
1284
1285 up_write(&nommu_region_sem);
1286
1287 return result;
1288
1289error_just_free:
1290 up_write(&nommu_region_sem);
1291error:
1292 if (region->vm_file)
1293 fput(region->vm_file);
1294 kmem_cache_free(vm_region_jar, region);
1295 if (vma->vm_file)
1296 fput(vma->vm_file);
1297 vm_area_free(vma);
1298 return ret;
1299
1300sharing_violation:
1301 up_write(&nommu_region_sem);
1302 pr_warn("Attempt to share mismatched mappings\n");
1303 ret = -EINVAL;
1304 goto error;
1305
1306error_getting_vma:
1307 kmem_cache_free(vm_region_jar, region);
1308 pr_warn("Allocation of vma for %lu byte allocation from process %d failed\n",
1309 len, current->pid);
1310 show_free_areas(0, NULL);
1311 return -ENOMEM;
1312
1313error_getting_region:
1314 pr_warn("Allocation of vm region for %lu byte allocation from process %d failed\n",
1315 len, current->pid);
1316 show_free_areas(0, NULL);
1317 return -ENOMEM;
1318}
1319
1320unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
1321 unsigned long prot, unsigned long flags,
1322 unsigned long fd, unsigned long pgoff)
1323{
1324 struct file *file = NULL;
1325 unsigned long retval = -EBADF;
1326
1327 audit_mmap_fd(fd, flags);
1328 if (!(flags & MAP_ANONYMOUS)) {
1329 file = fget(fd);
1330 if (!file)
1331 goto out;
1332 }
1333
1334 flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
1335
1336 retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
1337
1338 if (file)
1339 fput(file);
1340out:
1341 return retval;
1342}
1343
1344SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
1345 unsigned long, prot, unsigned long, flags,
1346 unsigned long, fd, unsigned long, pgoff)
1347{
1348 return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
1349}
1350
1351#ifdef __ARCH_WANT_SYS_OLD_MMAP
1352struct mmap_arg_struct {
1353 unsigned long addr;
1354 unsigned long len;
1355 unsigned long prot;
1356 unsigned long flags;
1357 unsigned long fd;
1358 unsigned long offset;
1359};
1360
1361SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
1362{
1363 struct mmap_arg_struct a;
1364
1365 if (copy_from_user(&a, arg, sizeof(a)))
1366 return -EFAULT;
1367 if (offset_in_page(a.offset))
1368 return -EINVAL;
1369
1370 return ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
1371 a.offset >> PAGE_SHIFT);
1372}
1373#endif /* __ARCH_WANT_SYS_OLD_MMAP */
1374
1375/*
1376 * split a vma into two pieces at address 'addr', a new vma is allocated either
1377 * for the first part or the tail.
1378 */
1379int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
1380 unsigned long addr, int new_below)
1381{
1382 struct vm_area_struct *new;
1383 struct vm_region *region;
1384 unsigned long npages;
1385
1386 /* we're only permitted to split anonymous regions (these should have
1387 * only a single usage on the region) */
1388 if (vma->vm_file)
1389 return -ENOMEM;
1390
1391 if (mm->map_count >= sysctl_max_map_count)
1392 return -ENOMEM;
1393
1394 region = kmem_cache_alloc(vm_region_jar, GFP_KERNEL);
1395 if (!region)
1396 return -ENOMEM;
1397
1398 new = vm_area_dup(vma);
1399 if (!new) {
1400 kmem_cache_free(vm_region_jar, region);
1401 return -ENOMEM;
1402 }
1403
1404 /* most fields are the same, copy all, and then fixup */
1405 *region = *vma->vm_region;
1406 new->vm_region = region;
1407
1408 npages = (addr - vma->vm_start) >> PAGE_SHIFT;
1409
1410 if (new_below) {
1411 region->vm_top = region->vm_end = new->vm_end = addr;
1412 } else {
1413 region->vm_start = new->vm_start = addr;
1414 region->vm_pgoff = new->vm_pgoff += npages;
1415 }
1416
1417 if (new->vm_ops && new->vm_ops->open)
1418 new->vm_ops->open(new);
1419
1420 delete_vma_from_mm(vma);
1421 down_write(&nommu_region_sem);
1422 delete_nommu_region(vma->vm_region);
1423 if (new_below) {
1424 vma->vm_region->vm_start = vma->vm_start = addr;
1425 vma->vm_region->vm_pgoff = vma->vm_pgoff += npages;
1426 } else {
1427 vma->vm_region->vm_end = vma->vm_end = addr;
1428 vma->vm_region->vm_top = addr;
1429 }
1430 add_nommu_region(vma->vm_region);
1431 add_nommu_region(new->vm_region);
1432 up_write(&nommu_region_sem);
1433 add_vma_to_mm(mm, vma);
1434 add_vma_to_mm(mm, new);
1435 return 0;
1436}
1437
1438/*
1439 * shrink a VMA by removing the specified chunk from either the beginning or
1440 * the end
1441 */
1442static int shrink_vma(struct mm_struct *mm,
1443 struct vm_area_struct *vma,
1444 unsigned long from, unsigned long to)
1445{
1446 struct vm_region *region;
1447
1448 /* adjust the VMA's pointers, which may reposition it in the MM's tree
1449 * and list */
1450 delete_vma_from_mm(vma);
1451 if (from > vma->vm_start)
1452 vma->vm_end = from;
1453 else
1454 vma->vm_start = to;
1455 add_vma_to_mm(mm, vma);
1456
1457 /* cut the backing region down to size */
1458 region = vma->vm_region;
1459 BUG_ON(region->vm_usage != 1);
1460
1461 down_write(&nommu_region_sem);
1462 delete_nommu_region(region);
1463 if (from > region->vm_start) {
1464 to = region->vm_top;
1465 region->vm_top = region->vm_end = from;
1466 } else {
1467 region->vm_start = to;
1468 }
1469 add_nommu_region(region);
1470 up_write(&nommu_region_sem);
1471
1472 free_page_series(from, to);
1473 return 0;
1474}
1475
1476/*
1477 * release a mapping
1478 * - under NOMMU conditions the chunk to be unmapped must be backed by a single
1479 * VMA, though it need not cover the whole VMA
1480 */
1481int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, struct list_head *uf)
1482{
1483 struct vm_area_struct *vma;
1484 unsigned long end;
1485 int ret;
1486
1487 len = PAGE_ALIGN(len);
1488 if (len == 0)
1489 return -EINVAL;
1490
1491 end = start + len;
1492
1493 /* find the first potentially overlapping VMA */
1494 vma = find_vma(mm, start);
1495 if (!vma) {
1496 static int limit;
1497 if (limit < 5) {
1498 pr_warn("munmap of memory not mmapped by process %d (%s): 0x%lx-0x%lx\n",
1499 current->pid, current->comm,
1500 start, start + len - 1);
1501 limit++;
1502 }
1503 return -EINVAL;
1504 }
1505
1506 /* we're allowed to split an anonymous VMA but not a file-backed one */
1507 if (vma->vm_file) {
1508 do {
1509 if (start > vma->vm_start)
1510 return -EINVAL;
1511 if (end == vma->vm_end)
1512 goto erase_whole_vma;
1513 vma = vma->vm_next;
1514 } while (vma);
1515 return -EINVAL;
1516 } else {
1517 /* the chunk must be a subset of the VMA found */
1518 if (start == vma->vm_start && end == vma->vm_end)
1519 goto erase_whole_vma;
1520 if (start < vma->vm_start || end > vma->vm_end)
1521 return -EINVAL;
1522 if (offset_in_page(start))
1523 return -EINVAL;
1524 if (end != vma->vm_end && offset_in_page(end))
1525 return -EINVAL;
1526 if (start != vma->vm_start && end != vma->vm_end) {
1527 ret = split_vma(mm, vma, start, 1);
1528 if (ret < 0)
1529 return ret;
1530 }
1531 return shrink_vma(mm, vma, start, end);
1532 }
1533
1534erase_whole_vma:
1535 delete_vma_from_mm(vma);
1536 delete_vma(mm, vma);
1537 return 0;
1538}
1539EXPORT_SYMBOL(do_munmap);
1540
1541int vm_munmap(unsigned long addr, size_t len)
1542{
1543 struct mm_struct *mm = current->mm;
1544 int ret;
1545
1546 down_write(&mm->mmap_sem);
1547 ret = do_munmap(mm, addr, len, NULL);
1548 up_write(&mm->mmap_sem);
1549 return ret;
1550}
1551EXPORT_SYMBOL(vm_munmap);
1552
1553SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
1554{
1555 return vm_munmap(addr, len);
1556}
1557
1558/*
1559 * release all the mappings made in a process's VM space
1560 */
1561void exit_mmap(struct mm_struct *mm)
1562{
1563 struct vm_area_struct *vma;
1564
1565 if (!mm)
1566 return;
1567
1568 mm->total_vm = 0;
1569
1570 while ((vma = mm->mmap)) {
1571 mm->mmap = vma->vm_next;
1572 delete_vma_from_mm(vma);
1573 delete_vma(mm, vma);
1574 cond_resched();
1575 }
1576}
1577
1578int vm_brk(unsigned long addr, unsigned long len)
1579{
1580 return -ENOMEM;
1581}
1582
1583/*
1584 * expand (or shrink) an existing mapping, potentially moving it at the same
1585 * time (controlled by the MREMAP_MAYMOVE flag and available VM space)
1586 *
1587 * under NOMMU conditions, we only permit changing a mapping's size, and only
1588 * as long as it stays within the region allocated by do_mmap_private() and the
1589 * block is not shareable
1590 *
1591 * MREMAP_FIXED is not supported under NOMMU conditions
1592 */
1593static unsigned long do_mremap(unsigned long addr,
1594 unsigned long old_len, unsigned long new_len,
1595 unsigned long flags, unsigned long new_addr)
1596{
1597 struct vm_area_struct *vma;
1598
1599 /* insanity checks first */
1600 old_len = PAGE_ALIGN(old_len);
1601 new_len = PAGE_ALIGN(new_len);
1602 if (old_len == 0 || new_len == 0)
1603 return (unsigned long) -EINVAL;
1604
1605 if (offset_in_page(addr))
1606 return -EINVAL;
1607
1608 if (flags & MREMAP_FIXED && new_addr != addr)
1609 return (unsigned long) -EINVAL;
1610
1611 vma = find_vma_exact(current->mm, addr, old_len);
1612 if (!vma)
1613 return (unsigned long) -EINVAL;
1614
1615 if (vma->vm_end != vma->vm_start + old_len)
1616 return (unsigned long) -EFAULT;
1617
1618 if (vma->vm_flags & VM_MAYSHARE)
1619 return (unsigned long) -EPERM;
1620
1621 if (new_len > vma->vm_region->vm_end - vma->vm_region->vm_start)
1622 return (unsigned long) -ENOMEM;
1623
1624 /* all checks complete - do it */
1625 vma->vm_end = vma->vm_start + new_len;
1626 return vma->vm_start;
1627}
1628
1629SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
1630 unsigned long, new_len, unsigned long, flags,
1631 unsigned long, new_addr)
1632{
1633 unsigned long ret;
1634
1635 down_write(¤t->mm->mmap_sem);
1636 ret = do_mremap(addr, old_len, new_len, flags, new_addr);
1637 up_write(¤t->mm->mmap_sem);
1638 return ret;
1639}
1640
1641struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
1642 unsigned int foll_flags)
1643{
1644 return NULL;
1645}
1646
1647int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
1648 unsigned long pfn, unsigned long size, pgprot_t prot)
1649{
1650 if (addr != (pfn << PAGE_SHIFT))
1651 return -EINVAL;
1652
1653 vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
1654 return 0;
1655}
1656EXPORT_SYMBOL(remap_pfn_range);
1657
1658int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len)
1659{
1660 unsigned long pfn = start >> PAGE_SHIFT;
1661 unsigned long vm_len = vma->vm_end - vma->vm_start;
1662
1663 pfn += vma->vm_pgoff;
1664 return io_remap_pfn_range(vma, vma->vm_start, pfn, vm_len, vma->vm_page_prot);
1665}
1666EXPORT_SYMBOL(vm_iomap_memory);
1667
1668int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
1669 unsigned long pgoff)
1670{
1671 unsigned int size = vma->vm_end - vma->vm_start;
1672
1673 if (!(vma->vm_flags & VM_USERMAP))
1674 return -EINVAL;
1675
1676 vma->vm_start = (unsigned long)(addr + (pgoff << PAGE_SHIFT));
1677 vma->vm_end = vma->vm_start + size;
1678
1679 return 0;
1680}
1681EXPORT_SYMBOL(remap_vmalloc_range);
1682
1683unsigned long arch_get_unmapped_area(struct file *file, unsigned long addr,
1684 unsigned long len, unsigned long pgoff, unsigned long flags)
1685{
1686 return -ENOMEM;
1687}
1688
1689vm_fault_t filemap_fault(struct vm_fault *vmf)
1690{
1691 BUG();
1692 return 0;
1693}
1694EXPORT_SYMBOL(filemap_fault);
1695
1696void filemap_map_pages(struct vm_fault *vmf,
1697 pgoff_t start_pgoff, pgoff_t end_pgoff)
1698{
1699 BUG();
1700}
1701EXPORT_SYMBOL(filemap_map_pages);
1702
1703int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
1704 unsigned long addr, void *buf, int len, unsigned int gup_flags)
1705{
1706 struct vm_area_struct *vma;
1707 int write = gup_flags & FOLL_WRITE;
1708
1709 if (down_read_killable(&mm->mmap_sem))
1710 return 0;
1711
1712 /* the access must start within one of the target process's mappings */
1713 vma = find_vma(mm, addr);
1714 if (vma) {
1715 /* don't overrun this mapping */
1716 if (addr + len >= vma->vm_end)
1717 len = vma->vm_end - addr;
1718
1719 /* only read or write mappings where it is permitted */
1720 if (write && vma->vm_flags & VM_MAYWRITE)
1721 copy_to_user_page(vma, NULL, addr,
1722 (void *) addr, buf, len);
1723 else if (!write && vma->vm_flags & VM_MAYREAD)
1724 copy_from_user_page(vma, NULL, addr,
1725 buf, (void *) addr, len);
1726 else
1727 len = 0;
1728 } else {
1729 len = 0;
1730 }
1731
1732 up_read(&mm->mmap_sem);
1733
1734 return len;
1735}
1736
1737/**
1738 * access_remote_vm - access another process' address space
1739 * @mm: the mm_struct of the target address space
1740 * @addr: start address to access
1741 * @buf: source or destination buffer
1742 * @len: number of bytes to transfer
1743 * @gup_flags: flags modifying lookup behaviour
1744 *
1745 * The caller must hold a reference on @mm.
1746 */
1747int access_remote_vm(struct mm_struct *mm, unsigned long addr,
1748 void *buf, int len, unsigned int gup_flags)
1749{
1750 return __access_remote_vm(NULL, mm, addr, buf, len, gup_flags);
1751}
1752
1753/*
1754 * Access another process' address space.
1755 * - source/target buffer must be kernel space
1756 */
1757int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len,
1758 unsigned int gup_flags)
1759{
1760 struct mm_struct *mm;
1761
1762 if (addr + len < addr)
1763 return 0;
1764
1765 mm = get_task_mm(tsk);
1766 if (!mm)
1767 return 0;
1768
1769 len = __access_remote_vm(tsk, mm, addr, buf, len, gup_flags);
1770
1771 mmput(mm);
1772 return len;
1773}
1774EXPORT_SYMBOL_GPL(access_process_vm);
1775
1776/**
1777 * nommu_shrink_inode_mappings - Shrink the shared mappings on an inode
1778 * @inode: The inode to check
1779 * @size: The current filesize of the inode
1780 * @newsize: The proposed filesize of the inode
1781 *
1782 * Check the shared mappings on an inode on behalf of a shrinking truncate to
1783 * make sure that that any outstanding VMAs aren't broken and then shrink the
1784 * vm_regions that extend that beyond so that do_mmap_pgoff() doesn't
1785 * automatically grant mappings that are too large.
1786 */
1787int nommu_shrink_inode_mappings(struct inode *inode, size_t size,
1788 size_t newsize)
1789{
1790 struct vm_area_struct *vma;
1791 struct vm_region *region;
1792 pgoff_t low, high;
1793 size_t r_size, r_top;
1794
1795 low = newsize >> PAGE_SHIFT;
1796 high = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1797
1798 down_write(&nommu_region_sem);
1799 i_mmap_lock_read(inode->i_mapping);
1800
1801 /* search for VMAs that fall within the dead zone */
1802 vma_interval_tree_foreach(vma, &inode->i_mapping->i_mmap, low, high) {
1803 /* found one - only interested if it's shared out of the page
1804 * cache */
1805 if (vma->vm_flags & VM_SHARED) {
1806 i_mmap_unlock_read(inode->i_mapping);
1807 up_write(&nommu_region_sem);
1808 return -ETXTBSY; /* not quite true, but near enough */
1809 }
1810 }
1811
1812 /* reduce any regions that overlap the dead zone - if in existence,
1813 * these will be pointed to by VMAs that don't overlap the dead zone
1814 *
1815 * we don't check for any regions that start beyond the EOF as there
1816 * shouldn't be any
1817 */
1818 vma_interval_tree_foreach(vma, &inode->i_mapping->i_mmap, 0, ULONG_MAX) {
1819 if (!(vma->vm_flags & VM_SHARED))
1820 continue;
1821
1822 region = vma->vm_region;
1823 r_size = region->vm_top - region->vm_start;
1824 r_top = (region->vm_pgoff << PAGE_SHIFT) + r_size;
1825
1826 if (r_top > newsize) {
1827 region->vm_top -= r_top - newsize;
1828 if (region->vm_end > region->vm_top)
1829 region->vm_end = region->vm_top;
1830 }
1831 }
1832
1833 i_mmap_unlock_read(inode->i_mapping);
1834 up_write(&nommu_region_sem);
1835 return 0;
1836}
1837
1838/*
1839 * Initialise sysctl_user_reserve_kbytes.
1840 *
1841 * This is intended to prevent a user from starting a single memory hogging
1842 * process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER
1843 * mode.
1844 *
1845 * The default value is min(3% of free memory, 128MB)
1846 * 128MB is enough to recover with sshd/login, bash, and top/kill.
1847 */
1848static int __meminit init_user_reserve(void)
1849{
1850 unsigned long free_kbytes;
1851
1852 free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
1853
1854 sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17);
1855 return 0;
1856}
1857subsys_initcall(init_user_reserve);
1858
1859/*
1860 * Initialise sysctl_admin_reserve_kbytes.
1861 *
1862 * The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin
1863 * to log in and kill a memory hogging process.
1864 *
1865 * Systems with more than 256MB will reserve 8MB, enough to recover
1866 * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
1867 * only reserve 3% of free pages by default.
1868 */
1869static int __meminit init_admin_reserve(void)
1870{
1871 unsigned long free_kbytes;
1872
1873 free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
1874
1875 sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
1876 return 0;
1877}
1878subsys_initcall(init_admin_reserve);