xref: /openbmc/linux/mm/nommu.c (revision b9ddb2500e7e544410f38476ab928fc2fe01e381)
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/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  
46  void *high_memory;
47  EXPORT_SYMBOL(high_memory);
48  struct page *mem_map;
49  unsigned long max_mapnr;
50  EXPORT_SYMBOL(max_mapnr);
51  unsigned long highest_memmap_pfn;
52  int sysctl_nr_trim_pages = CONFIG_NOMMU_INITIAL_TRIM_EXCESS;
53  int heap_stack_gap = 0;
54  
55  atomic_long_t mmap_pages_allocated;
56  
57  EXPORT_SYMBOL(mem_map);
58  
59  /* list of mapped, potentially shareable regions */
60  static struct kmem_cache *vm_region_jar;
61  struct rb_root nommu_region_tree = RB_ROOT;
62  DECLARE_RWSEM(nommu_region_sem);
63  
64  const 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   */
73  unsigned 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   */
124  int 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  }
133  EXPORT_SYMBOL(follow_pfn);
134  
135  LIST_HEAD(vmap_area_list);
136  
137  void vfree(const void *addr)
138  {
139  	kfree(addr);
140  }
141  EXPORT_SYMBOL(vfree);
142  
143  void *__vmalloc(unsigned long size, gfp_t gfp_mask)
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  }
151  EXPORT_SYMBOL(__vmalloc);
152  
153  void *__vmalloc_node_range(unsigned long size, unsigned long align,
154  		unsigned long start, unsigned long end, gfp_t gfp_mask,
155  		pgprot_t prot, unsigned long vm_flags, int node,
156  		const void *caller)
157  {
158  	return __vmalloc(size, gfp_mask);
159  }
160  
161  void *__vmalloc_node(unsigned long size, unsigned long align, gfp_t gfp_mask,
162  		int node, const void *caller)
163  {
164  	return __vmalloc(size, gfp_mask);
165  }
166  
167  static void *__vmalloc_user_flags(unsigned long size, gfp_t flags)
168  {
169  	void *ret;
170  
171  	ret = __vmalloc(size, flags);
172  	if (ret) {
173  		struct vm_area_struct *vma;
174  
175  		mmap_write_lock(current->mm);
176  		vma = find_vma(current->mm, (unsigned long)ret);
177  		if (vma)
178  			vma->vm_flags |= VM_USERMAP;
179  		mmap_write_unlock(current->mm);
180  	}
181  
182  	return ret;
183  }
184  
185  void *vmalloc_user(unsigned long size)
186  {
187  	return __vmalloc_user_flags(size, GFP_KERNEL | __GFP_ZERO);
188  }
189  EXPORT_SYMBOL(vmalloc_user);
190  
191  struct page *vmalloc_to_page(const void *addr)
192  {
193  	return virt_to_page(addr);
194  }
195  EXPORT_SYMBOL(vmalloc_to_page);
196  
197  unsigned long vmalloc_to_pfn(const void *addr)
198  {
199  	return page_to_pfn(virt_to_page(addr));
200  }
201  EXPORT_SYMBOL(vmalloc_to_pfn);
202  
203  long vread(char *buf, char *addr, unsigned long count)
204  {
205  	/* Don't allow overflow */
206  	if ((unsigned long) buf + count < count)
207  		count = -(unsigned long) buf;
208  
209  	memcpy(buf, addr, count);
210  	return count;
211  }
212  
213  long vwrite(char *buf, char *addr, unsigned long count)
214  {
215  	/* Don't allow overflow */
216  	if ((unsigned long) addr + count < count)
217  		count = -(unsigned long) addr;
218  
219  	memcpy(addr, buf, count);
220  	return count;
221  }
222  
223  /*
224   *	vmalloc  -  allocate virtually contiguous memory
225   *
226   *	@size:		allocation size
227   *
228   *	Allocate enough pages to cover @size from the page level
229   *	allocator and map them into contiguous kernel virtual space.
230   *
231   *	For tight control over page level allocator and protection flags
232   *	use __vmalloc() instead.
233   */
234  void *vmalloc(unsigned long size)
235  {
236         return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM);
237  }
238  EXPORT_SYMBOL(vmalloc);
239  
240  /*
241   *	vzalloc - allocate virtually contiguous memory with zero fill
242   *
243   *	@size:		allocation size
244   *
245   *	Allocate enough pages to cover @size from the page level
246   *	allocator and map them into contiguous kernel virtual space.
247   *	The memory allocated is set to zero.
248   *
249   *	For tight control over page level allocator and protection flags
250   *	use __vmalloc() instead.
251   */
252  void *vzalloc(unsigned long size)
253  {
254  	return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO);
255  }
256  EXPORT_SYMBOL(vzalloc);
257  
258  /**
259   * vmalloc_node - allocate memory on a specific node
260   * @size:	allocation size
261   * @node:	numa node
262   *
263   * Allocate enough pages to cover @size from the page level
264   * allocator and map them into contiguous kernel virtual space.
265   *
266   * For tight control over page level allocator and protection flags
267   * use __vmalloc() instead.
268   */
269  void *vmalloc_node(unsigned long size, int node)
270  {
271  	return vmalloc(size);
272  }
273  EXPORT_SYMBOL(vmalloc_node);
274  
275  /**
276   * vzalloc_node - allocate memory on a specific node with zero fill
277   * @size:	allocation size
278   * @node:	numa node
279   *
280   * Allocate enough pages to cover @size from the page level
281   * allocator and map them into contiguous kernel virtual space.
282   * The memory allocated is set to zero.
283   *
284   * For tight control over page level allocator and protection flags
285   * use __vmalloc() instead.
286   */
287  void *vzalloc_node(unsigned long size, int node)
288  {
289  	return vzalloc(size);
290  }
291  EXPORT_SYMBOL(vzalloc_node);
292  
293  /**
294   * vmalloc_32  -  allocate virtually contiguous memory (32bit addressable)
295   *	@size:		allocation size
296   *
297   *	Allocate enough 32bit PA addressable pages to cover @size from the
298   *	page level allocator and map them into contiguous kernel virtual space.
299   */
300  void *vmalloc_32(unsigned long size)
301  {
302  	return __vmalloc(size, GFP_KERNEL);
303  }
304  EXPORT_SYMBOL(vmalloc_32);
305  
306  /**
307   * vmalloc_32_user - allocate zeroed virtually contiguous 32bit memory
308   *	@size:		allocation size
309   *
310   * The resulting memory area is 32bit addressable and zeroed so it can be
311   * mapped to userspace without leaking data.
312   *
313   * VM_USERMAP is set on the corresponding VMA so that subsequent calls to
314   * remap_vmalloc_range() are permissible.
315   */
316  void *vmalloc_32_user(unsigned long size)
317  {
318  	/*
319  	 * We'll have to sort out the ZONE_DMA bits for 64-bit,
320  	 * but for now this can simply use vmalloc_user() directly.
321  	 */
322  	return vmalloc_user(size);
323  }
324  EXPORT_SYMBOL(vmalloc_32_user);
325  
326  void *vmap(struct page **pages, unsigned int count, unsigned long flags, pgprot_t prot)
327  {
328  	BUG();
329  	return NULL;
330  }
331  EXPORT_SYMBOL(vmap);
332  
333  void vunmap(const void *addr)
334  {
335  	BUG();
336  }
337  EXPORT_SYMBOL(vunmap);
338  
339  void *vm_map_ram(struct page **pages, unsigned int count, int node)
340  {
341  	BUG();
342  	return NULL;
343  }
344  EXPORT_SYMBOL(vm_map_ram);
345  
346  void vm_unmap_ram(const void *mem, unsigned int count)
347  {
348  	BUG();
349  }
350  EXPORT_SYMBOL(vm_unmap_ram);
351  
352  void vm_unmap_aliases(void)
353  {
354  }
355  EXPORT_SYMBOL_GPL(vm_unmap_aliases);
356  
357  void free_vm_area(struct vm_struct *area)
358  {
359  	BUG();
360  }
361  EXPORT_SYMBOL_GPL(free_vm_area);
362  
363  int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
364  		   struct page *page)
365  {
366  	return -EINVAL;
367  }
368  EXPORT_SYMBOL(vm_insert_page);
369  
370  int vm_map_pages(struct vm_area_struct *vma, struct page **pages,
371  			unsigned long num)
372  {
373  	return -EINVAL;
374  }
375  EXPORT_SYMBOL(vm_map_pages);
376  
377  int vm_map_pages_zero(struct vm_area_struct *vma, struct page **pages,
378  				unsigned long num)
379  {
380  	return -EINVAL;
381  }
382  EXPORT_SYMBOL(vm_map_pages_zero);
383  
384  /*
385   *  sys_brk() for the most part doesn't need the global kernel
386   *  lock, except when an application is doing something nasty
387   *  like trying to un-brk an area that has already been mapped
388   *  to a regular file.  in this case, the unmapping will need
389   *  to invoke file system routines that need the global lock.
390   */
391  SYSCALL_DEFINE1(brk, unsigned long, brk)
392  {
393  	struct mm_struct *mm = current->mm;
394  
395  	if (brk < mm->start_brk || brk > mm->context.end_brk)
396  		return mm->brk;
397  
398  	if (mm->brk == brk)
399  		return mm->brk;
400  
401  	/*
402  	 * Always allow shrinking brk
403  	 */
404  	if (brk <= mm->brk) {
405  		mm->brk = brk;
406  		return brk;
407  	}
408  
409  	/*
410  	 * Ok, looks good - let it rip.
411  	 */
412  	flush_icache_user_range(mm->brk, brk);
413  	return mm->brk = brk;
414  }
415  
416  /*
417   * initialise the percpu counter for VM and region record slabs
418   */
419  void __init mmap_init(void)
420  {
421  	int ret;
422  
423  	ret = percpu_counter_init(&vm_committed_as, 0, GFP_KERNEL);
424  	VM_BUG_ON(ret);
425  	vm_region_jar = KMEM_CACHE(vm_region, SLAB_PANIC|SLAB_ACCOUNT);
426  }
427  
428  /*
429   * validate the region tree
430   * - the caller must hold the region lock
431   */
432  #ifdef CONFIG_DEBUG_NOMMU_REGIONS
433  static noinline void validate_nommu_regions(void)
434  {
435  	struct vm_region *region, *last;
436  	struct rb_node *p, *lastp;
437  
438  	lastp = rb_first(&nommu_region_tree);
439  	if (!lastp)
440  		return;
441  
442  	last = rb_entry(lastp, struct vm_region, vm_rb);
443  	BUG_ON(last->vm_end <= last->vm_start);
444  	BUG_ON(last->vm_top < last->vm_end);
445  
446  	while ((p = rb_next(lastp))) {
447  		region = rb_entry(p, struct vm_region, vm_rb);
448  		last = rb_entry(lastp, struct vm_region, vm_rb);
449  
450  		BUG_ON(region->vm_end <= region->vm_start);
451  		BUG_ON(region->vm_top < region->vm_end);
452  		BUG_ON(region->vm_start < last->vm_top);
453  
454  		lastp = p;
455  	}
456  }
457  #else
458  static void validate_nommu_regions(void)
459  {
460  }
461  #endif
462  
463  /*
464   * add a region into the global tree
465   */
466  static void add_nommu_region(struct vm_region *region)
467  {
468  	struct vm_region *pregion;
469  	struct rb_node **p, *parent;
470  
471  	validate_nommu_regions();
472  
473  	parent = NULL;
474  	p = &nommu_region_tree.rb_node;
475  	while (*p) {
476  		parent = *p;
477  		pregion = rb_entry(parent, struct vm_region, vm_rb);
478  		if (region->vm_start < pregion->vm_start)
479  			p = &(*p)->rb_left;
480  		else if (region->vm_start > pregion->vm_start)
481  			p = &(*p)->rb_right;
482  		else if (pregion == region)
483  			return;
484  		else
485  			BUG();
486  	}
487  
488  	rb_link_node(&region->vm_rb, parent, p);
489  	rb_insert_color(&region->vm_rb, &nommu_region_tree);
490  
491  	validate_nommu_regions();
492  }
493  
494  /*
495   * delete a region from the global tree
496   */
497  static void delete_nommu_region(struct vm_region *region)
498  {
499  	BUG_ON(!nommu_region_tree.rb_node);
500  
501  	validate_nommu_regions();
502  	rb_erase(&region->vm_rb, &nommu_region_tree);
503  	validate_nommu_regions();
504  }
505  
506  /*
507   * free a contiguous series of pages
508   */
509  static void free_page_series(unsigned long from, unsigned long to)
510  {
511  	for (; from < to; from += PAGE_SIZE) {
512  		struct page *page = virt_to_page(from);
513  
514  		atomic_long_dec(&mmap_pages_allocated);
515  		put_page(page);
516  	}
517  }
518  
519  /*
520   * release a reference to a region
521   * - the caller must hold the region semaphore for writing, which this releases
522   * - the region may not have been added to the tree yet, in which case vm_top
523   *   will equal vm_start
524   */
525  static void __put_nommu_region(struct vm_region *region)
526  	__releases(nommu_region_sem)
527  {
528  	BUG_ON(!nommu_region_tree.rb_node);
529  
530  	if (--region->vm_usage == 0) {
531  		if (region->vm_top > region->vm_start)
532  			delete_nommu_region(region);
533  		up_write(&nommu_region_sem);
534  
535  		if (region->vm_file)
536  			fput(region->vm_file);
537  
538  		/* IO memory and memory shared directly out of the pagecache
539  		 * from ramfs/tmpfs mustn't be released here */
540  		if (region->vm_flags & VM_MAPPED_COPY)
541  			free_page_series(region->vm_start, region->vm_top);
542  		kmem_cache_free(vm_region_jar, region);
543  	} else {
544  		up_write(&nommu_region_sem);
545  	}
546  }
547  
548  /*
549   * release a reference to a region
550   */
551  static void put_nommu_region(struct vm_region *region)
552  {
553  	down_write(&nommu_region_sem);
554  	__put_nommu_region(region);
555  }
556  
557  /*
558   * add a VMA into a process's mm_struct in the appropriate place in the list
559   * and tree and add to the address space's page tree also if not an anonymous
560   * page
561   * - should be called with mm->mmap_lock held writelocked
562   */
563  static void add_vma_to_mm(struct mm_struct *mm, struct vm_area_struct *vma)
564  {
565  	struct vm_area_struct *pvma, *prev;
566  	struct address_space *mapping;
567  	struct rb_node **p, *parent, *rb_prev;
568  
569  	BUG_ON(!vma->vm_region);
570  
571  	mm->map_count++;
572  	vma->vm_mm = mm;
573  
574  	/* add the VMA to the mapping */
575  	if (vma->vm_file) {
576  		mapping = vma->vm_file->f_mapping;
577  
578  		i_mmap_lock_write(mapping);
579  		flush_dcache_mmap_lock(mapping);
580  		vma_interval_tree_insert(vma, &mapping->i_mmap);
581  		flush_dcache_mmap_unlock(mapping);
582  		i_mmap_unlock_write(mapping);
583  	}
584  
585  	/* add the VMA to the tree */
586  	parent = rb_prev = NULL;
587  	p = &mm->mm_rb.rb_node;
588  	while (*p) {
589  		parent = *p;
590  		pvma = rb_entry(parent, struct vm_area_struct, vm_rb);
591  
592  		/* sort by: start addr, end addr, VMA struct addr in that order
593  		 * (the latter is necessary as we may get identical VMAs) */
594  		if (vma->vm_start < pvma->vm_start)
595  			p = &(*p)->rb_left;
596  		else if (vma->vm_start > pvma->vm_start) {
597  			rb_prev = parent;
598  			p = &(*p)->rb_right;
599  		} else if (vma->vm_end < pvma->vm_end)
600  			p = &(*p)->rb_left;
601  		else if (vma->vm_end > pvma->vm_end) {
602  			rb_prev = parent;
603  			p = &(*p)->rb_right;
604  		} else if (vma < pvma)
605  			p = &(*p)->rb_left;
606  		else if (vma > pvma) {
607  			rb_prev = parent;
608  			p = &(*p)->rb_right;
609  		} else
610  			BUG();
611  	}
612  
613  	rb_link_node(&vma->vm_rb, parent, p);
614  	rb_insert_color(&vma->vm_rb, &mm->mm_rb);
615  
616  	/* add VMA to the VMA list also */
617  	prev = NULL;
618  	if (rb_prev)
619  		prev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
620  
621  	__vma_link_list(mm, vma, prev);
622  }
623  
624  /*
625   * delete a VMA from its owning mm_struct and address space
626   */
627  static void delete_vma_from_mm(struct vm_area_struct *vma)
628  {
629  	int i;
630  	struct address_space *mapping;
631  	struct mm_struct *mm = vma->vm_mm;
632  	struct task_struct *curr = current;
633  
634  	mm->map_count--;
635  	for (i = 0; i < VMACACHE_SIZE; i++) {
636  		/* if the vma is cached, invalidate the entire cache */
637  		if (curr->vmacache.vmas[i] == vma) {
638  			vmacache_invalidate(mm);
639  			break;
640  		}
641  	}
642  
643  	/* remove the VMA from the mapping */
644  	if (vma->vm_file) {
645  		mapping = vma->vm_file->f_mapping;
646  
647  		i_mmap_lock_write(mapping);
648  		flush_dcache_mmap_lock(mapping);
649  		vma_interval_tree_remove(vma, &mapping->i_mmap);
650  		flush_dcache_mmap_unlock(mapping);
651  		i_mmap_unlock_write(mapping);
652  	}
653  
654  	/* remove from the MM's tree and list */
655  	rb_erase(&vma->vm_rb, &mm->mm_rb);
656  
657  	__vma_unlink_list(mm, vma);
658  }
659  
660  /*
661   * destroy a VMA record
662   */
663  static void delete_vma(struct mm_struct *mm, struct vm_area_struct *vma)
664  {
665  	if (vma->vm_ops && vma->vm_ops->close)
666  		vma->vm_ops->close(vma);
667  	if (vma->vm_file)
668  		fput(vma->vm_file);
669  	put_nommu_region(vma->vm_region);
670  	vm_area_free(vma);
671  }
672  
673  /*
674   * look up the first VMA in which addr resides, NULL if none
675   * - should be called with mm->mmap_lock at least held readlocked
676   */
677  struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
678  {
679  	struct vm_area_struct *vma;
680  
681  	/* check the cache first */
682  	vma = vmacache_find(mm, addr);
683  	if (likely(vma))
684  		return vma;
685  
686  	/* trawl the list (there may be multiple mappings in which addr
687  	 * resides) */
688  	for (vma = mm->mmap; vma; vma = vma->vm_next) {
689  		if (vma->vm_start > addr)
690  			return NULL;
691  		if (vma->vm_end > addr) {
692  			vmacache_update(addr, vma);
693  			return vma;
694  		}
695  	}
696  
697  	return NULL;
698  }
699  EXPORT_SYMBOL(find_vma);
700  
701  /*
702   * find a VMA
703   * - we don't extend stack VMAs under NOMMU conditions
704   */
705  struct vm_area_struct *find_extend_vma(struct mm_struct *mm, unsigned long addr)
706  {
707  	return find_vma(mm, addr);
708  }
709  
710  /*
711   * expand a stack to a given address
712   * - not supported under NOMMU conditions
713   */
714  int expand_stack(struct vm_area_struct *vma, unsigned long address)
715  {
716  	return -ENOMEM;
717  }
718  
719  /*
720   * look up the first VMA exactly that exactly matches addr
721   * - should be called with mm->mmap_lock at least held readlocked
722   */
723  static struct vm_area_struct *find_vma_exact(struct mm_struct *mm,
724  					     unsigned long addr,
725  					     unsigned long len)
726  {
727  	struct vm_area_struct *vma;
728  	unsigned long end = addr + len;
729  
730  	/* check the cache first */
731  	vma = vmacache_find_exact(mm, addr, end);
732  	if (vma)
733  		return vma;
734  
735  	/* trawl the list (there may be multiple mappings in which addr
736  	 * resides) */
737  	for (vma = mm->mmap; vma; vma = vma->vm_next) {
738  		if (vma->vm_start < addr)
739  			continue;
740  		if (vma->vm_start > addr)
741  			return NULL;
742  		if (vma->vm_end == end) {
743  			vmacache_update(addr, vma);
744  			return vma;
745  		}
746  	}
747  
748  	return NULL;
749  }
750  
751  /*
752   * determine whether a mapping should be permitted and, if so, what sort of
753   * mapping we're capable of supporting
754   */
755  static int validate_mmap_request(struct file *file,
756  				 unsigned long addr,
757  				 unsigned long len,
758  				 unsigned long prot,
759  				 unsigned long flags,
760  				 unsigned long pgoff,
761  				 unsigned long *_capabilities)
762  {
763  	unsigned long capabilities, rlen;
764  	int ret;
765  
766  	/* do the simple checks first */
767  	if (flags & MAP_FIXED)
768  		return -EINVAL;
769  
770  	if ((flags & MAP_TYPE) != MAP_PRIVATE &&
771  	    (flags & MAP_TYPE) != MAP_SHARED)
772  		return -EINVAL;
773  
774  	if (!len)
775  		return -EINVAL;
776  
777  	/* Careful about overflows.. */
778  	rlen = PAGE_ALIGN(len);
779  	if (!rlen || rlen > TASK_SIZE)
780  		return -ENOMEM;
781  
782  	/* offset overflow? */
783  	if ((pgoff + (rlen >> PAGE_SHIFT)) < pgoff)
784  		return -EOVERFLOW;
785  
786  	if (file) {
787  		/* files must support mmap */
788  		if (!file->f_op->mmap)
789  			return -ENODEV;
790  
791  		/* work out if what we've got could possibly be shared
792  		 * - we support chardevs that provide their own "memory"
793  		 * - we support files/blockdevs that are memory backed
794  		 */
795  		if (file->f_op->mmap_capabilities) {
796  			capabilities = file->f_op->mmap_capabilities(file);
797  		} else {
798  			/* no explicit capabilities set, so assume some
799  			 * defaults */
800  			switch (file_inode(file)->i_mode & S_IFMT) {
801  			case S_IFREG:
802  			case S_IFBLK:
803  				capabilities = NOMMU_MAP_COPY;
804  				break;
805  
806  			case S_IFCHR:
807  				capabilities =
808  					NOMMU_MAP_DIRECT |
809  					NOMMU_MAP_READ |
810  					NOMMU_MAP_WRITE;
811  				break;
812  
813  			default:
814  				return -EINVAL;
815  			}
816  		}
817  
818  		/* eliminate any capabilities that we can't support on this
819  		 * device */
820  		if (!file->f_op->get_unmapped_area)
821  			capabilities &= ~NOMMU_MAP_DIRECT;
822  		if (!(file->f_mode & FMODE_CAN_READ))
823  			capabilities &= ~NOMMU_MAP_COPY;
824  
825  		/* The file shall have been opened with read permission. */
826  		if (!(file->f_mode & FMODE_READ))
827  			return -EACCES;
828  
829  		if (flags & MAP_SHARED) {
830  			/* do checks for writing, appending and locking */
831  			if ((prot & PROT_WRITE) &&
832  			    !(file->f_mode & FMODE_WRITE))
833  				return -EACCES;
834  
835  			if (IS_APPEND(file_inode(file)) &&
836  			    (file->f_mode & FMODE_WRITE))
837  				return -EACCES;
838  
839  			if (locks_verify_locked(file))
840  				return -EAGAIN;
841  
842  			if (!(capabilities & NOMMU_MAP_DIRECT))
843  				return -ENODEV;
844  
845  			/* we mustn't privatise shared mappings */
846  			capabilities &= ~NOMMU_MAP_COPY;
847  		} else {
848  			/* we're going to read the file into private memory we
849  			 * allocate */
850  			if (!(capabilities & NOMMU_MAP_COPY))
851  				return -ENODEV;
852  
853  			/* we don't permit a private writable mapping to be
854  			 * shared with the backing device */
855  			if (prot & PROT_WRITE)
856  				capabilities &= ~NOMMU_MAP_DIRECT;
857  		}
858  
859  		if (capabilities & NOMMU_MAP_DIRECT) {
860  			if (((prot & PROT_READ)  && !(capabilities & NOMMU_MAP_READ))  ||
861  			    ((prot & PROT_WRITE) && !(capabilities & NOMMU_MAP_WRITE)) ||
862  			    ((prot & PROT_EXEC)  && !(capabilities & NOMMU_MAP_EXEC))
863  			    ) {
864  				capabilities &= ~NOMMU_MAP_DIRECT;
865  				if (flags & MAP_SHARED) {
866  					pr_warn("MAP_SHARED not completely supported on !MMU\n");
867  					return -EINVAL;
868  				}
869  			}
870  		}
871  
872  		/* handle executable mappings and implied executable
873  		 * mappings */
874  		if (path_noexec(&file->f_path)) {
875  			if (prot & PROT_EXEC)
876  				return -EPERM;
877  		} else if ((prot & PROT_READ) && !(prot & PROT_EXEC)) {
878  			/* handle implication of PROT_EXEC by PROT_READ */
879  			if (current->personality & READ_IMPLIES_EXEC) {
880  				if (capabilities & NOMMU_MAP_EXEC)
881  					prot |= PROT_EXEC;
882  			}
883  		} else if ((prot & PROT_READ) &&
884  			 (prot & PROT_EXEC) &&
885  			 !(capabilities & NOMMU_MAP_EXEC)
886  			 ) {
887  			/* backing file is not executable, try to copy */
888  			capabilities &= ~NOMMU_MAP_DIRECT;
889  		}
890  	} else {
891  		/* anonymous mappings are always memory backed and can be
892  		 * privately mapped
893  		 */
894  		capabilities = NOMMU_MAP_COPY;
895  
896  		/* handle PROT_EXEC implication by PROT_READ */
897  		if ((prot & PROT_READ) &&
898  		    (current->personality & READ_IMPLIES_EXEC))
899  			prot |= PROT_EXEC;
900  	}
901  
902  	/* allow the security API to have its say */
903  	ret = security_mmap_addr(addr);
904  	if (ret < 0)
905  		return ret;
906  
907  	/* looks okay */
908  	*_capabilities = capabilities;
909  	return 0;
910  }
911  
912  /*
913   * we've determined that we can make the mapping, now translate what we
914   * now know into VMA flags
915   */
916  static unsigned long determine_vm_flags(struct file *file,
917  					unsigned long prot,
918  					unsigned long flags,
919  					unsigned long capabilities)
920  {
921  	unsigned long vm_flags;
922  
923  	vm_flags = calc_vm_prot_bits(prot, 0) | calc_vm_flag_bits(flags);
924  	/* vm_flags |= mm->def_flags; */
925  
926  	if (!(capabilities & NOMMU_MAP_DIRECT)) {
927  		/* attempt to share read-only copies of mapped file chunks */
928  		vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
929  		if (file && !(prot & PROT_WRITE))
930  			vm_flags |= VM_MAYSHARE;
931  	} else {
932  		/* overlay a shareable mapping on the backing device or inode
933  		 * if possible - used for chardevs, ramfs/tmpfs/shmfs and
934  		 * romfs/cramfs */
935  		vm_flags |= VM_MAYSHARE | (capabilities & NOMMU_VMFLAGS);
936  		if (flags & MAP_SHARED)
937  			vm_flags |= VM_SHARED;
938  	}
939  
940  	/* refuse to let anyone share private mappings with this process if
941  	 * it's being traced - otherwise breakpoints set in it may interfere
942  	 * with another untraced process
943  	 */
944  	if ((flags & MAP_PRIVATE) && current->ptrace)
945  		vm_flags &= ~VM_MAYSHARE;
946  
947  	return vm_flags;
948  }
949  
950  /*
951   * set up a shared mapping on a file (the driver or filesystem provides and
952   * pins the storage)
953   */
954  static int do_mmap_shared_file(struct vm_area_struct *vma)
955  {
956  	int ret;
957  
958  	ret = call_mmap(vma->vm_file, vma);
959  	if (ret == 0) {
960  		vma->vm_region->vm_top = vma->vm_region->vm_end;
961  		return 0;
962  	}
963  	if (ret != -ENOSYS)
964  		return ret;
965  
966  	/* getting -ENOSYS indicates that direct mmap isn't possible (as
967  	 * opposed to tried but failed) so we can only give a suitable error as
968  	 * it's not possible to make a private copy if MAP_SHARED was given */
969  	return -ENODEV;
970  }
971  
972  /*
973   * set up a private mapping or an anonymous shared mapping
974   */
975  static int do_mmap_private(struct vm_area_struct *vma,
976  			   struct vm_region *region,
977  			   unsigned long len,
978  			   unsigned long capabilities)
979  {
980  	unsigned long total, point;
981  	void *base;
982  	int ret, order;
983  
984  	/* invoke the file's mapping function so that it can keep track of
985  	 * shared mappings on devices or memory
986  	 * - VM_MAYSHARE will be set if it may attempt to share
987  	 */
988  	if (capabilities & NOMMU_MAP_DIRECT) {
989  		ret = call_mmap(vma->vm_file, vma);
990  		if (ret == 0) {
991  			/* shouldn't return success if we're not sharing */
992  			BUG_ON(!(vma->vm_flags & VM_MAYSHARE));
993  			vma->vm_region->vm_top = vma->vm_region->vm_end;
994  			return 0;
995  		}
996  		if (ret != -ENOSYS)
997  			return ret;
998  
999  		/* getting an ENOSYS error indicates that direct mmap isn't
1000  		 * possible (as opposed to tried but failed) so we'll try to
1001  		 * make a private copy of the data and map that instead */
1002  	}
1003  
1004  
1005  	/* allocate some memory to hold the mapping
1006  	 * - note that this may not return a page-aligned address if the object
1007  	 *   we're allocating is smaller than a page
1008  	 */
1009  	order = get_order(len);
1010  	total = 1 << order;
1011  	point = len >> PAGE_SHIFT;
1012  
1013  	/* we don't want to allocate a power-of-2 sized page set */
1014  	if (sysctl_nr_trim_pages && total - point >= sysctl_nr_trim_pages)
1015  		total = point;
1016  
1017  	base = alloc_pages_exact(total << PAGE_SHIFT, GFP_KERNEL);
1018  	if (!base)
1019  		goto enomem;
1020  
1021  	atomic_long_add(total, &mmap_pages_allocated);
1022  
1023  	region->vm_flags = vma->vm_flags |= VM_MAPPED_COPY;
1024  	region->vm_start = (unsigned long) base;
1025  	region->vm_end   = region->vm_start + len;
1026  	region->vm_top   = region->vm_start + (total << PAGE_SHIFT);
1027  
1028  	vma->vm_start = region->vm_start;
1029  	vma->vm_end   = region->vm_start + len;
1030  
1031  	if (vma->vm_file) {
1032  		/* read the contents of a file into the copy */
1033  		loff_t fpos;
1034  
1035  		fpos = vma->vm_pgoff;
1036  		fpos <<= PAGE_SHIFT;
1037  
1038  		ret = kernel_read(vma->vm_file, base, len, &fpos);
1039  		if (ret < 0)
1040  			goto error_free;
1041  
1042  		/* clear the last little bit */
1043  		if (ret < len)
1044  			memset(base + ret, 0, len - ret);
1045  
1046  	} else {
1047  		vma_set_anonymous(vma);
1048  	}
1049  
1050  	return 0;
1051  
1052  error_free:
1053  	free_page_series(region->vm_start, region->vm_top);
1054  	region->vm_start = vma->vm_start = 0;
1055  	region->vm_end   = vma->vm_end = 0;
1056  	region->vm_top   = 0;
1057  	return ret;
1058  
1059  enomem:
1060  	pr_err("Allocation of length %lu from process %d (%s) failed\n",
1061  	       len, current->pid, current->comm);
1062  	show_free_areas(0, NULL);
1063  	return -ENOMEM;
1064  }
1065  
1066  /*
1067   * handle mapping creation for uClinux
1068   */
1069  unsigned long do_mmap(struct file *file,
1070  			unsigned long addr,
1071  			unsigned long len,
1072  			unsigned long prot,
1073  			unsigned long flags,
1074  			unsigned long pgoff,
1075  			unsigned long *populate,
1076  			struct list_head *uf)
1077  {
1078  	struct vm_area_struct *vma;
1079  	struct vm_region *region;
1080  	struct rb_node *rb;
1081  	vm_flags_t vm_flags;
1082  	unsigned long capabilities, result;
1083  	int ret;
1084  
1085  	*populate = 0;
1086  
1087  	/* decide whether we should attempt the mapping, and if so what sort of
1088  	 * mapping */
1089  	ret = validate_mmap_request(file, addr, len, prot, flags, pgoff,
1090  				    &capabilities);
1091  	if (ret < 0)
1092  		return ret;
1093  
1094  	/* we ignore the address hint */
1095  	addr = 0;
1096  	len = PAGE_ALIGN(len);
1097  
1098  	/* we've determined that we can make the mapping, now translate what we
1099  	 * now know into VMA flags */
1100  	vm_flags = determine_vm_flags(file, prot, flags, capabilities);
1101  
1102  	/* we're going to need to record the mapping */
1103  	region = kmem_cache_zalloc(vm_region_jar, GFP_KERNEL);
1104  	if (!region)
1105  		goto error_getting_region;
1106  
1107  	vma = vm_area_alloc(current->mm);
1108  	if (!vma)
1109  		goto error_getting_vma;
1110  
1111  	region->vm_usage = 1;
1112  	region->vm_flags = vm_flags;
1113  	region->vm_pgoff = pgoff;
1114  
1115  	vma->vm_flags = vm_flags;
1116  	vma->vm_pgoff = pgoff;
1117  
1118  	if (file) {
1119  		region->vm_file = get_file(file);
1120  		vma->vm_file = get_file(file);
1121  	}
1122  
1123  	down_write(&nommu_region_sem);
1124  
1125  	/* if we want to share, we need to check for regions created by other
1126  	 * mmap() calls that overlap with our proposed mapping
1127  	 * - we can only share with a superset match on most regular files
1128  	 * - shared mappings on character devices and memory backed files are
1129  	 *   permitted to overlap inexactly as far as we are concerned for in
1130  	 *   these cases, sharing is handled in the driver or filesystem rather
1131  	 *   than here
1132  	 */
1133  	if (vm_flags & VM_MAYSHARE) {
1134  		struct vm_region *pregion;
1135  		unsigned long pglen, rpglen, pgend, rpgend, start;
1136  
1137  		pglen = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1138  		pgend = pgoff + pglen;
1139  
1140  		for (rb = rb_first(&nommu_region_tree); rb; rb = rb_next(rb)) {
1141  			pregion = rb_entry(rb, struct vm_region, vm_rb);
1142  
1143  			if (!(pregion->vm_flags & VM_MAYSHARE))
1144  				continue;
1145  
1146  			/* search for overlapping mappings on the same file */
1147  			if (file_inode(pregion->vm_file) !=
1148  			    file_inode(file))
1149  				continue;
1150  
1151  			if (pregion->vm_pgoff >= pgend)
1152  				continue;
1153  
1154  			rpglen = pregion->vm_end - pregion->vm_start;
1155  			rpglen = (rpglen + PAGE_SIZE - 1) >> PAGE_SHIFT;
1156  			rpgend = pregion->vm_pgoff + rpglen;
1157  			if (pgoff >= rpgend)
1158  				continue;
1159  
1160  			/* handle inexactly overlapping matches between
1161  			 * mappings */
1162  			if ((pregion->vm_pgoff != pgoff || rpglen != pglen) &&
1163  			    !(pgoff >= pregion->vm_pgoff && pgend <= rpgend)) {
1164  				/* new mapping is not a subset of the region */
1165  				if (!(capabilities & NOMMU_MAP_DIRECT))
1166  					goto sharing_violation;
1167  				continue;
1168  			}
1169  
1170  			/* we've found a region we can share */
1171  			pregion->vm_usage++;
1172  			vma->vm_region = pregion;
1173  			start = pregion->vm_start;
1174  			start += (pgoff - pregion->vm_pgoff) << PAGE_SHIFT;
1175  			vma->vm_start = start;
1176  			vma->vm_end = start + len;
1177  
1178  			if (pregion->vm_flags & VM_MAPPED_COPY)
1179  				vma->vm_flags |= VM_MAPPED_COPY;
1180  			else {
1181  				ret = do_mmap_shared_file(vma);
1182  				if (ret < 0) {
1183  					vma->vm_region = NULL;
1184  					vma->vm_start = 0;
1185  					vma->vm_end = 0;
1186  					pregion->vm_usage--;
1187  					pregion = NULL;
1188  					goto error_just_free;
1189  				}
1190  			}
1191  			fput(region->vm_file);
1192  			kmem_cache_free(vm_region_jar, region);
1193  			region = pregion;
1194  			result = start;
1195  			goto share;
1196  		}
1197  
1198  		/* obtain the address at which to make a shared mapping
1199  		 * - this is the hook for quasi-memory character devices to
1200  		 *   tell us the location of a shared mapping
1201  		 */
1202  		if (capabilities & NOMMU_MAP_DIRECT) {
1203  			addr = file->f_op->get_unmapped_area(file, addr, len,
1204  							     pgoff, flags);
1205  			if (IS_ERR_VALUE(addr)) {
1206  				ret = addr;
1207  				if (ret != -ENOSYS)
1208  					goto error_just_free;
1209  
1210  				/* the driver refused to tell us where to site
1211  				 * the mapping so we'll have to attempt to copy
1212  				 * it */
1213  				ret = -ENODEV;
1214  				if (!(capabilities & NOMMU_MAP_COPY))
1215  					goto error_just_free;
1216  
1217  				capabilities &= ~NOMMU_MAP_DIRECT;
1218  			} else {
1219  				vma->vm_start = region->vm_start = addr;
1220  				vma->vm_end = region->vm_end = addr + len;
1221  			}
1222  		}
1223  	}
1224  
1225  	vma->vm_region = region;
1226  
1227  	/* set up the mapping
1228  	 * - the region is filled in if NOMMU_MAP_DIRECT is still set
1229  	 */
1230  	if (file && vma->vm_flags & VM_SHARED)
1231  		ret = do_mmap_shared_file(vma);
1232  	else
1233  		ret = do_mmap_private(vma, region, len, capabilities);
1234  	if (ret < 0)
1235  		goto error_just_free;
1236  	add_nommu_region(region);
1237  
1238  	/* clear anonymous mappings that don't ask for uninitialized data */
1239  	if (!vma->vm_file &&
1240  	    (!IS_ENABLED(CONFIG_MMAP_ALLOW_UNINITIALIZED) ||
1241  	     !(flags & MAP_UNINITIALIZED)))
1242  		memset((void *)region->vm_start, 0,
1243  		       region->vm_end - region->vm_start);
1244  
1245  	/* okay... we have a mapping; now we have to register it */
1246  	result = vma->vm_start;
1247  
1248  	current->mm->total_vm += len >> PAGE_SHIFT;
1249  
1250  share:
1251  	add_vma_to_mm(current->mm, vma);
1252  
1253  	/* we flush the region from the icache only when the first executable
1254  	 * mapping of it is made  */
1255  	if (vma->vm_flags & VM_EXEC && !region->vm_icache_flushed) {
1256  		flush_icache_user_range(region->vm_start, region->vm_end);
1257  		region->vm_icache_flushed = true;
1258  	}
1259  
1260  	up_write(&nommu_region_sem);
1261  
1262  	return result;
1263  
1264  error_just_free:
1265  	up_write(&nommu_region_sem);
1266  error:
1267  	if (region->vm_file)
1268  		fput(region->vm_file);
1269  	kmem_cache_free(vm_region_jar, region);
1270  	if (vma->vm_file)
1271  		fput(vma->vm_file);
1272  	vm_area_free(vma);
1273  	return ret;
1274  
1275  sharing_violation:
1276  	up_write(&nommu_region_sem);
1277  	pr_warn("Attempt to share mismatched mappings\n");
1278  	ret = -EINVAL;
1279  	goto error;
1280  
1281  error_getting_vma:
1282  	kmem_cache_free(vm_region_jar, region);
1283  	pr_warn("Allocation of vma for %lu byte allocation from process %d failed\n",
1284  			len, current->pid);
1285  	show_free_areas(0, NULL);
1286  	return -ENOMEM;
1287  
1288  error_getting_region:
1289  	pr_warn("Allocation of vm region for %lu byte allocation from process %d failed\n",
1290  			len, current->pid);
1291  	show_free_areas(0, NULL);
1292  	return -ENOMEM;
1293  }
1294  
1295  unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
1296  			      unsigned long prot, unsigned long flags,
1297  			      unsigned long fd, unsigned long pgoff)
1298  {
1299  	struct file *file = NULL;
1300  	unsigned long retval = -EBADF;
1301  
1302  	audit_mmap_fd(fd, flags);
1303  	if (!(flags & MAP_ANONYMOUS)) {
1304  		file = fget(fd);
1305  		if (!file)
1306  			goto out;
1307  	}
1308  
1309  	flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
1310  
1311  	retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
1312  
1313  	if (file)
1314  		fput(file);
1315  out:
1316  	return retval;
1317  }
1318  
1319  SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
1320  		unsigned long, prot, unsigned long, flags,
1321  		unsigned long, fd, unsigned long, pgoff)
1322  {
1323  	return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
1324  }
1325  
1326  #ifdef __ARCH_WANT_SYS_OLD_MMAP
1327  struct mmap_arg_struct {
1328  	unsigned long addr;
1329  	unsigned long len;
1330  	unsigned long prot;
1331  	unsigned long flags;
1332  	unsigned long fd;
1333  	unsigned long offset;
1334  };
1335  
1336  SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
1337  {
1338  	struct mmap_arg_struct a;
1339  
1340  	if (copy_from_user(&a, arg, sizeof(a)))
1341  		return -EFAULT;
1342  	if (offset_in_page(a.offset))
1343  		return -EINVAL;
1344  
1345  	return ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
1346  			       a.offset >> PAGE_SHIFT);
1347  }
1348  #endif /* __ARCH_WANT_SYS_OLD_MMAP */
1349  
1350  /*
1351   * split a vma into two pieces at address 'addr', a new vma is allocated either
1352   * for the first part or the tail.
1353   */
1354  int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
1355  	      unsigned long addr, int new_below)
1356  {
1357  	struct vm_area_struct *new;
1358  	struct vm_region *region;
1359  	unsigned long npages;
1360  
1361  	/* we're only permitted to split anonymous regions (these should have
1362  	 * only a single usage on the region) */
1363  	if (vma->vm_file)
1364  		return -ENOMEM;
1365  
1366  	if (mm->map_count >= sysctl_max_map_count)
1367  		return -ENOMEM;
1368  
1369  	region = kmem_cache_alloc(vm_region_jar, GFP_KERNEL);
1370  	if (!region)
1371  		return -ENOMEM;
1372  
1373  	new = vm_area_dup(vma);
1374  	if (!new) {
1375  		kmem_cache_free(vm_region_jar, region);
1376  		return -ENOMEM;
1377  	}
1378  
1379  	/* most fields are the same, copy all, and then fixup */
1380  	*region = *vma->vm_region;
1381  	new->vm_region = region;
1382  
1383  	npages = (addr - vma->vm_start) >> PAGE_SHIFT;
1384  
1385  	if (new_below) {
1386  		region->vm_top = region->vm_end = new->vm_end = addr;
1387  	} else {
1388  		region->vm_start = new->vm_start = addr;
1389  		region->vm_pgoff = new->vm_pgoff += npages;
1390  	}
1391  
1392  	if (new->vm_ops && new->vm_ops->open)
1393  		new->vm_ops->open(new);
1394  
1395  	delete_vma_from_mm(vma);
1396  	down_write(&nommu_region_sem);
1397  	delete_nommu_region(vma->vm_region);
1398  	if (new_below) {
1399  		vma->vm_region->vm_start = vma->vm_start = addr;
1400  		vma->vm_region->vm_pgoff = vma->vm_pgoff += npages;
1401  	} else {
1402  		vma->vm_region->vm_end = vma->vm_end = addr;
1403  		vma->vm_region->vm_top = addr;
1404  	}
1405  	add_nommu_region(vma->vm_region);
1406  	add_nommu_region(new->vm_region);
1407  	up_write(&nommu_region_sem);
1408  	add_vma_to_mm(mm, vma);
1409  	add_vma_to_mm(mm, new);
1410  	return 0;
1411  }
1412  
1413  /*
1414   * shrink a VMA by removing the specified chunk from either the beginning or
1415   * the end
1416   */
1417  static int shrink_vma(struct mm_struct *mm,
1418  		      struct vm_area_struct *vma,
1419  		      unsigned long from, unsigned long to)
1420  {
1421  	struct vm_region *region;
1422  
1423  	/* adjust the VMA's pointers, which may reposition it in the MM's tree
1424  	 * and list */
1425  	delete_vma_from_mm(vma);
1426  	if (from > vma->vm_start)
1427  		vma->vm_end = from;
1428  	else
1429  		vma->vm_start = to;
1430  	add_vma_to_mm(mm, vma);
1431  
1432  	/* cut the backing region down to size */
1433  	region = vma->vm_region;
1434  	BUG_ON(region->vm_usage != 1);
1435  
1436  	down_write(&nommu_region_sem);
1437  	delete_nommu_region(region);
1438  	if (from > region->vm_start) {
1439  		to = region->vm_top;
1440  		region->vm_top = region->vm_end = from;
1441  	} else {
1442  		region->vm_start = to;
1443  	}
1444  	add_nommu_region(region);
1445  	up_write(&nommu_region_sem);
1446  
1447  	free_page_series(from, to);
1448  	return 0;
1449  }
1450  
1451  /*
1452   * release a mapping
1453   * - under NOMMU conditions the chunk to be unmapped must be backed by a single
1454   *   VMA, though it need not cover the whole VMA
1455   */
1456  int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, struct list_head *uf)
1457  {
1458  	struct vm_area_struct *vma;
1459  	unsigned long end;
1460  	int ret;
1461  
1462  	len = PAGE_ALIGN(len);
1463  	if (len == 0)
1464  		return -EINVAL;
1465  
1466  	end = start + len;
1467  
1468  	/* find the first potentially overlapping VMA */
1469  	vma = find_vma(mm, start);
1470  	if (!vma) {
1471  		static int limit;
1472  		if (limit < 5) {
1473  			pr_warn("munmap of memory not mmapped by process %d (%s): 0x%lx-0x%lx\n",
1474  					current->pid, current->comm,
1475  					start, start + len - 1);
1476  			limit++;
1477  		}
1478  		return -EINVAL;
1479  	}
1480  
1481  	/* we're allowed to split an anonymous VMA but not a file-backed one */
1482  	if (vma->vm_file) {
1483  		do {
1484  			if (start > vma->vm_start)
1485  				return -EINVAL;
1486  			if (end == vma->vm_end)
1487  				goto erase_whole_vma;
1488  			vma = vma->vm_next;
1489  		} while (vma);
1490  		return -EINVAL;
1491  	} else {
1492  		/* the chunk must be a subset of the VMA found */
1493  		if (start == vma->vm_start && end == vma->vm_end)
1494  			goto erase_whole_vma;
1495  		if (start < vma->vm_start || end > vma->vm_end)
1496  			return -EINVAL;
1497  		if (offset_in_page(start))
1498  			return -EINVAL;
1499  		if (end != vma->vm_end && offset_in_page(end))
1500  			return -EINVAL;
1501  		if (start != vma->vm_start && end != vma->vm_end) {
1502  			ret = split_vma(mm, vma, start, 1);
1503  			if (ret < 0)
1504  				return ret;
1505  		}
1506  		return shrink_vma(mm, vma, start, end);
1507  	}
1508  
1509  erase_whole_vma:
1510  	delete_vma_from_mm(vma);
1511  	delete_vma(mm, vma);
1512  	return 0;
1513  }
1514  EXPORT_SYMBOL(do_munmap);
1515  
1516  int vm_munmap(unsigned long addr, size_t len)
1517  {
1518  	struct mm_struct *mm = current->mm;
1519  	int ret;
1520  
1521  	mmap_write_lock(mm);
1522  	ret = do_munmap(mm, addr, len, NULL);
1523  	mmap_write_unlock(mm);
1524  	return ret;
1525  }
1526  EXPORT_SYMBOL(vm_munmap);
1527  
1528  SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
1529  {
1530  	return vm_munmap(addr, len);
1531  }
1532  
1533  /*
1534   * release all the mappings made in a process's VM space
1535   */
1536  void exit_mmap(struct mm_struct *mm)
1537  {
1538  	struct vm_area_struct *vma;
1539  
1540  	if (!mm)
1541  		return;
1542  
1543  	mm->total_vm = 0;
1544  
1545  	while ((vma = mm->mmap)) {
1546  		mm->mmap = vma->vm_next;
1547  		delete_vma_from_mm(vma);
1548  		delete_vma(mm, vma);
1549  		cond_resched();
1550  	}
1551  }
1552  
1553  int vm_brk(unsigned long addr, unsigned long len)
1554  {
1555  	return -ENOMEM;
1556  }
1557  
1558  /*
1559   * expand (or shrink) an existing mapping, potentially moving it at the same
1560   * time (controlled by the MREMAP_MAYMOVE flag and available VM space)
1561   *
1562   * under NOMMU conditions, we only permit changing a mapping's size, and only
1563   * as long as it stays within the region allocated by do_mmap_private() and the
1564   * block is not shareable
1565   *
1566   * MREMAP_FIXED is not supported under NOMMU conditions
1567   */
1568  static unsigned long do_mremap(unsigned long addr,
1569  			unsigned long old_len, unsigned long new_len,
1570  			unsigned long flags, unsigned long new_addr)
1571  {
1572  	struct vm_area_struct *vma;
1573  
1574  	/* insanity checks first */
1575  	old_len = PAGE_ALIGN(old_len);
1576  	new_len = PAGE_ALIGN(new_len);
1577  	if (old_len == 0 || new_len == 0)
1578  		return (unsigned long) -EINVAL;
1579  
1580  	if (offset_in_page(addr))
1581  		return -EINVAL;
1582  
1583  	if (flags & MREMAP_FIXED && new_addr != addr)
1584  		return (unsigned long) -EINVAL;
1585  
1586  	vma = find_vma_exact(current->mm, addr, old_len);
1587  	if (!vma)
1588  		return (unsigned long) -EINVAL;
1589  
1590  	if (vma->vm_end != vma->vm_start + old_len)
1591  		return (unsigned long) -EFAULT;
1592  
1593  	if (vma->vm_flags & VM_MAYSHARE)
1594  		return (unsigned long) -EPERM;
1595  
1596  	if (new_len > vma->vm_region->vm_end - vma->vm_region->vm_start)
1597  		return (unsigned long) -ENOMEM;
1598  
1599  	/* all checks complete - do it */
1600  	vma->vm_end = vma->vm_start + new_len;
1601  	return vma->vm_start;
1602  }
1603  
1604  SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
1605  		unsigned long, new_len, unsigned long, flags,
1606  		unsigned long, new_addr)
1607  {
1608  	unsigned long ret;
1609  
1610  	mmap_write_lock(current->mm);
1611  	ret = do_mremap(addr, old_len, new_len, flags, new_addr);
1612  	mmap_write_unlock(current->mm);
1613  	return ret;
1614  }
1615  
1616  struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
1617  			 unsigned int foll_flags)
1618  {
1619  	return NULL;
1620  }
1621  
1622  int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
1623  		unsigned long pfn, unsigned long size, pgprot_t prot)
1624  {
1625  	if (addr != (pfn << PAGE_SHIFT))
1626  		return -EINVAL;
1627  
1628  	vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
1629  	return 0;
1630  }
1631  EXPORT_SYMBOL(remap_pfn_range);
1632  
1633  int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len)
1634  {
1635  	unsigned long pfn = start >> PAGE_SHIFT;
1636  	unsigned long vm_len = vma->vm_end - vma->vm_start;
1637  
1638  	pfn += vma->vm_pgoff;
1639  	return io_remap_pfn_range(vma, vma->vm_start, pfn, vm_len, vma->vm_page_prot);
1640  }
1641  EXPORT_SYMBOL(vm_iomap_memory);
1642  
1643  int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
1644  			unsigned long pgoff)
1645  {
1646  	unsigned int size = vma->vm_end - vma->vm_start;
1647  
1648  	if (!(vma->vm_flags & VM_USERMAP))
1649  		return -EINVAL;
1650  
1651  	vma->vm_start = (unsigned long)(addr + (pgoff << PAGE_SHIFT));
1652  	vma->vm_end = vma->vm_start + size;
1653  
1654  	return 0;
1655  }
1656  EXPORT_SYMBOL(remap_vmalloc_range);
1657  
1658  unsigned long arch_get_unmapped_area(struct file *file, unsigned long addr,
1659  	unsigned long len, unsigned long pgoff, unsigned long flags)
1660  {
1661  	return -ENOMEM;
1662  }
1663  
1664  vm_fault_t filemap_fault(struct vm_fault *vmf)
1665  {
1666  	BUG();
1667  	return 0;
1668  }
1669  EXPORT_SYMBOL(filemap_fault);
1670  
1671  void filemap_map_pages(struct vm_fault *vmf,
1672  		pgoff_t start_pgoff, pgoff_t end_pgoff)
1673  {
1674  	BUG();
1675  }
1676  EXPORT_SYMBOL(filemap_map_pages);
1677  
1678  int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf,
1679  		       int len, unsigned int gup_flags)
1680  {
1681  	struct vm_area_struct *vma;
1682  	int write = gup_flags & FOLL_WRITE;
1683  
1684  	if (mmap_read_lock_killable(mm))
1685  		return 0;
1686  
1687  	/* the access must start within one of the target process's mappings */
1688  	vma = find_vma(mm, addr);
1689  	if (vma) {
1690  		/* don't overrun this mapping */
1691  		if (addr + len >= vma->vm_end)
1692  			len = vma->vm_end - addr;
1693  
1694  		/* only read or write mappings where it is permitted */
1695  		if (write && vma->vm_flags & VM_MAYWRITE)
1696  			copy_to_user_page(vma, NULL, addr,
1697  					 (void *) addr, buf, len);
1698  		else if (!write && vma->vm_flags & VM_MAYREAD)
1699  			copy_from_user_page(vma, NULL, addr,
1700  					    buf, (void *) addr, len);
1701  		else
1702  			len = 0;
1703  	} else {
1704  		len = 0;
1705  	}
1706  
1707  	mmap_read_unlock(mm);
1708  
1709  	return len;
1710  }
1711  
1712  /**
1713   * access_remote_vm - access another process' address space
1714   * @mm:		the mm_struct of the target address space
1715   * @addr:	start address to access
1716   * @buf:	source or destination buffer
1717   * @len:	number of bytes to transfer
1718   * @gup_flags:	flags modifying lookup behaviour
1719   *
1720   * The caller must hold a reference on @mm.
1721   */
1722  int access_remote_vm(struct mm_struct *mm, unsigned long addr,
1723  		void *buf, int len, unsigned int gup_flags)
1724  {
1725  	return __access_remote_vm(mm, addr, buf, len, gup_flags);
1726  }
1727  
1728  /*
1729   * Access another process' address space.
1730   * - source/target buffer must be kernel space
1731   */
1732  int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len,
1733  		unsigned int gup_flags)
1734  {
1735  	struct mm_struct *mm;
1736  
1737  	if (addr + len < addr)
1738  		return 0;
1739  
1740  	mm = get_task_mm(tsk);
1741  	if (!mm)
1742  		return 0;
1743  
1744  	len = __access_remote_vm(mm, addr, buf, len, gup_flags);
1745  
1746  	mmput(mm);
1747  	return len;
1748  }
1749  EXPORT_SYMBOL_GPL(access_process_vm);
1750  
1751  /**
1752   * nommu_shrink_inode_mappings - Shrink the shared mappings on an inode
1753   * @inode: The inode to check
1754   * @size: The current filesize of the inode
1755   * @newsize: The proposed filesize of the inode
1756   *
1757   * Check the shared mappings on an inode on behalf of a shrinking truncate to
1758   * make sure that any outstanding VMAs aren't broken and then shrink the
1759   * vm_regions that extend beyond so that do_mmap() doesn't
1760   * automatically grant mappings that are too large.
1761   */
1762  int nommu_shrink_inode_mappings(struct inode *inode, size_t size,
1763  				size_t newsize)
1764  {
1765  	struct vm_area_struct *vma;
1766  	struct vm_region *region;
1767  	pgoff_t low, high;
1768  	size_t r_size, r_top;
1769  
1770  	low = newsize >> PAGE_SHIFT;
1771  	high = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1772  
1773  	down_write(&nommu_region_sem);
1774  	i_mmap_lock_read(inode->i_mapping);
1775  
1776  	/* search for VMAs that fall within the dead zone */
1777  	vma_interval_tree_foreach(vma, &inode->i_mapping->i_mmap, low, high) {
1778  		/* found one - only interested if it's shared out of the page
1779  		 * cache */
1780  		if (vma->vm_flags & VM_SHARED) {
1781  			i_mmap_unlock_read(inode->i_mapping);
1782  			up_write(&nommu_region_sem);
1783  			return -ETXTBSY; /* not quite true, but near enough */
1784  		}
1785  	}
1786  
1787  	/* reduce any regions that overlap the dead zone - if in existence,
1788  	 * these will be pointed to by VMAs that don't overlap the dead zone
1789  	 *
1790  	 * we don't check for any regions that start beyond the EOF as there
1791  	 * shouldn't be any
1792  	 */
1793  	vma_interval_tree_foreach(vma, &inode->i_mapping->i_mmap, 0, ULONG_MAX) {
1794  		if (!(vma->vm_flags & VM_SHARED))
1795  			continue;
1796  
1797  		region = vma->vm_region;
1798  		r_size = region->vm_top - region->vm_start;
1799  		r_top = (region->vm_pgoff << PAGE_SHIFT) + r_size;
1800  
1801  		if (r_top > newsize) {
1802  			region->vm_top -= r_top - newsize;
1803  			if (region->vm_end > region->vm_top)
1804  				region->vm_end = region->vm_top;
1805  		}
1806  	}
1807  
1808  	i_mmap_unlock_read(inode->i_mapping);
1809  	up_write(&nommu_region_sem);
1810  	return 0;
1811  }
1812  
1813  /*
1814   * Initialise sysctl_user_reserve_kbytes.
1815   *
1816   * This is intended to prevent a user from starting a single memory hogging
1817   * process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER
1818   * mode.
1819   *
1820   * The default value is min(3% of free memory, 128MB)
1821   * 128MB is enough to recover with sshd/login, bash, and top/kill.
1822   */
1823  static int __meminit init_user_reserve(void)
1824  {
1825  	unsigned long free_kbytes;
1826  
1827  	free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
1828  
1829  	sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17);
1830  	return 0;
1831  }
1832  subsys_initcall(init_user_reserve);
1833  
1834  /*
1835   * Initialise sysctl_admin_reserve_kbytes.
1836   *
1837   * The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin
1838   * to log in and kill a memory hogging process.
1839   *
1840   * Systems with more than 256MB will reserve 8MB, enough to recover
1841   * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
1842   * only reserve 3% of free pages by default.
1843   */
1844  static int __meminit init_admin_reserve(void)
1845  {
1846  	unsigned long free_kbytes;
1847  
1848  	free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
1849  
1850  	sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
1851  	return 0;
1852  }
1853  subsys_initcall(init_admin_reserve);
1854