xref: /openbmc/linux/mm/nommu.c (revision a6978d1b7bb8f3a25305e8ff7d367f7289614c5d)
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 <linux/uio.h>
40  #include <asm/tlb.h>
41  #include <asm/tlbflush.h>
42  #include <asm/mmu_context.h>
43  #include "internal.h"
44  
45  void *high_memory;
46  EXPORT_SYMBOL(high_memory);
47  struct page *mem_map;
48  unsigned long max_mapnr;
49  EXPORT_SYMBOL(max_mapnr);
50  unsigned long highest_memmap_pfn;
51  int sysctl_nr_trim_pages = CONFIG_NOMMU_INITIAL_TRIM_EXCESS;
52  int heap_stack_gap = 0;
53  
54  atomic_long_t mmap_pages_allocated;
55  
56  EXPORT_SYMBOL(mem_map);
57  
58  /* list of mapped, potentially shareable regions */
59  static struct kmem_cache *vm_region_jar;
60  struct rb_root nommu_region_tree = RB_ROOT;
61  DECLARE_RWSEM(nommu_region_sem);
62  
63  const struct vm_operations_struct generic_file_vm_ops = {
64  };
65  
66  /*
67   * Return the total memory allocated for this pointer, not
68   * just what the caller asked for.
69   *
70   * Doesn't have to be accurate, i.e. may have races.
71   */
72  unsigned int kobjsize(const void *objp)
73  {
74  	struct page *page;
75  
76  	/*
77  	 * If the object we have should not have ksize performed on it,
78  	 * return size of 0
79  	 */
80  	if (!objp || !virt_addr_valid(objp))
81  		return 0;
82  
83  	page = virt_to_head_page(objp);
84  
85  	/*
86  	 * If the allocator sets PageSlab, we know the pointer came from
87  	 * kmalloc().
88  	 */
89  	if (PageSlab(page))
90  		return ksize(objp);
91  
92  	/*
93  	 * If it's not a compound page, see if we have a matching VMA
94  	 * region. This test is intentionally done in reverse order,
95  	 * so if there's no VMA, we still fall through and hand back
96  	 * PAGE_SIZE for 0-order pages.
97  	 */
98  	if (!PageCompound(page)) {
99  		struct vm_area_struct *vma;
100  
101  		vma = find_vma(current->mm, (unsigned long)objp);
102  		if (vma)
103  			return vma->vm_end - vma->vm_start;
104  	}
105  
106  	/*
107  	 * The ksize() function is only guaranteed to work for pointers
108  	 * returned by kmalloc(). So handle arbitrary pointers here.
109  	 */
110  	return page_size(page);
111  }
112  
113  /**
114   * follow_pfn - look up PFN at a user virtual address
115   * @vma: memory mapping
116   * @address: user virtual address
117   * @pfn: location to store found PFN
118   *
119   * Only IO mappings and raw PFN mappings are allowed.
120   *
121   * Returns zero and the pfn at @pfn on success, -ve otherwise.
122   */
123  int follow_pfn(struct vm_area_struct *vma, unsigned long address,
124  	unsigned long *pfn)
125  {
126  	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
127  		return -EINVAL;
128  
129  	*pfn = address >> PAGE_SHIFT;
130  	return 0;
131  }
132  EXPORT_SYMBOL(follow_pfn);
133  
134  LIST_HEAD(vmap_area_list);
135  
136  void vfree(const void *addr)
137  {
138  	kfree(addr);
139  }
140  EXPORT_SYMBOL(vfree);
141  
142  void *__vmalloc(unsigned long size, gfp_t gfp_mask)
143  {
144  	/*
145  	 *  You can't specify __GFP_HIGHMEM with kmalloc() since kmalloc()
146  	 * returns only a logical address.
147  	 */
148  	return kmalloc(size, (gfp_mask | __GFP_COMP) & ~__GFP_HIGHMEM);
149  }
150  EXPORT_SYMBOL(__vmalloc);
151  
152  void *__vmalloc_node_range(unsigned long size, unsigned long align,
153  		unsigned long start, unsigned long end, gfp_t gfp_mask,
154  		pgprot_t prot, unsigned long vm_flags, int node,
155  		const void *caller)
156  {
157  	return __vmalloc(size, gfp_mask);
158  }
159  
160  void *__vmalloc_node(unsigned long size, unsigned long align, gfp_t gfp_mask,
161  		int node, const void *caller)
162  {
163  	return __vmalloc(size, gfp_mask);
164  }
165  
166  static void *__vmalloc_user_flags(unsigned long size, gfp_t flags)
167  {
168  	void *ret;
169  
170  	ret = __vmalloc(size, flags);
171  	if (ret) {
172  		struct vm_area_struct *vma;
173  
174  		mmap_write_lock(current->mm);
175  		vma = find_vma(current->mm, (unsigned long)ret);
176  		if (vma)
177  			vm_flags_set(vma, VM_USERMAP);
178  		mmap_write_unlock(current->mm);
179  	}
180  
181  	return ret;
182  }
183  
184  void *vmalloc_user(unsigned long size)
185  {
186  	return __vmalloc_user_flags(size, GFP_KERNEL | __GFP_ZERO);
187  }
188  EXPORT_SYMBOL(vmalloc_user);
189  
190  struct page *vmalloc_to_page(const void *addr)
191  {
192  	return virt_to_page(addr);
193  }
194  EXPORT_SYMBOL(vmalloc_to_page);
195  
196  unsigned long vmalloc_to_pfn(const void *addr)
197  {
198  	return page_to_pfn(virt_to_page(addr));
199  }
200  EXPORT_SYMBOL(vmalloc_to_pfn);
201  
202  long vread_iter(struct iov_iter *iter, const char *addr, size_t count)
203  {
204  	/* Don't allow overflow */
205  	if ((unsigned long) addr + count < count)
206  		count = -(unsigned long) addr;
207  
208  	return copy_to_iter(addr, count, iter);
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   */
222  void *vmalloc(unsigned long size)
223  {
224  	return __vmalloc(size, GFP_KERNEL);
225  }
226  EXPORT_SYMBOL(vmalloc);
227  
228  void *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   */
242  void *vzalloc(unsigned long size)
243  {
244  	return __vmalloc(size, GFP_KERNEL | __GFP_ZERO);
245  }
246  EXPORT_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   */
259  void *vmalloc_node(unsigned long size, int node)
260  {
261  	return vmalloc(size);
262  }
263  EXPORT_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   */
277  void *vzalloc_node(unsigned long size, int node)
278  {
279  	return vzalloc(size);
280  }
281  EXPORT_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   */
290  void *vmalloc_32(unsigned long size)
291  {
292  	return __vmalloc(size, GFP_KERNEL);
293  }
294  EXPORT_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   */
306  void *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  }
314  EXPORT_SYMBOL(vmalloc_32_user);
315  
316  void *vmap(struct page **pages, unsigned int count, unsigned long flags, pgprot_t prot)
317  {
318  	BUG();
319  	return NULL;
320  }
321  EXPORT_SYMBOL(vmap);
322  
323  void vunmap(const void *addr)
324  {
325  	BUG();
326  }
327  EXPORT_SYMBOL(vunmap);
328  
329  void *vm_map_ram(struct page **pages, unsigned int count, int node)
330  {
331  	BUG();
332  	return NULL;
333  }
334  EXPORT_SYMBOL(vm_map_ram);
335  
336  void vm_unmap_ram(const void *mem, unsigned int count)
337  {
338  	BUG();
339  }
340  EXPORT_SYMBOL(vm_unmap_ram);
341  
342  void vm_unmap_aliases(void)
343  {
344  }
345  EXPORT_SYMBOL_GPL(vm_unmap_aliases);
346  
347  void free_vm_area(struct vm_struct *area)
348  {
349  	BUG();
350  }
351  EXPORT_SYMBOL_GPL(free_vm_area);
352  
353  int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
354  		   struct page *page)
355  {
356  	return -EINVAL;
357  }
358  EXPORT_SYMBOL(vm_insert_page);
359  
360  int vm_map_pages(struct vm_area_struct *vma, struct page **pages,
361  			unsigned long num)
362  {
363  	return -EINVAL;
364  }
365  EXPORT_SYMBOL(vm_map_pages);
366  
367  int vm_map_pages_zero(struct vm_area_struct *vma, struct page **pages,
368  				unsigned long num)
369  {
370  	return -EINVAL;
371  }
372  EXPORT_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   */
381  SYSCALL_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   */
409  void __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
423  static 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
448  static void validate_nommu_regions(void)
449  {
450  }
451  #endif
452  
453  /*
454   * add a region into the global tree
455   */
456  static 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(&region->vm_rb, parent, p);
479  	rb_insert_color(&region->vm_rb, &nommu_region_tree);
480  
481  	validate_nommu_regions();
482  }
483  
484  /*
485   * delete a region from the global tree
486   */
487  static 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(&region->vm_rb, &nommu_region_tree);
493  	validate_nommu_regions();
494  }
495  
496  /*
497   * free a contiguous series of pages
498   */
499  static 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   */
515  static 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   */
541  static void put_nommu_region(struct vm_region *region)
542  {
543  	down_write(&nommu_region_sem);
544  	__put_nommu_region(region);
545  }
546  
547  static void setup_vma_to_mm(struct vm_area_struct *vma, struct mm_struct *mm)
548  {
549  	vma->vm_mm = mm;
550  
551  	/* add the VMA to the mapping */
552  	if (vma->vm_file) {
553  		struct address_space *mapping = vma->vm_file->f_mapping;
554  
555  		i_mmap_lock_write(mapping);
556  		flush_dcache_mmap_lock(mapping);
557  		vma_interval_tree_insert(vma, &mapping->i_mmap);
558  		flush_dcache_mmap_unlock(mapping);
559  		i_mmap_unlock_write(mapping);
560  	}
561  }
562  
563  static void cleanup_vma_from_mm(struct vm_area_struct *vma)
564  {
565  	vma->vm_mm->map_count--;
566  	/* remove the VMA from the mapping */
567  	if (vma->vm_file) {
568  		struct address_space *mapping;
569  		mapping = vma->vm_file->f_mapping;
570  
571  		i_mmap_lock_write(mapping);
572  		flush_dcache_mmap_lock(mapping);
573  		vma_interval_tree_remove(vma, &mapping->i_mmap);
574  		flush_dcache_mmap_unlock(mapping);
575  		i_mmap_unlock_write(mapping);
576  	}
577  }
578  
579  /*
580   * delete a VMA from its owning mm_struct and address space
581   */
582  static int delete_vma_from_mm(struct vm_area_struct *vma)
583  {
584  	VMA_ITERATOR(vmi, vma->vm_mm, vma->vm_start);
585  
586  	vma_iter_config(&vmi, vma->vm_start, vma->vm_end);
587  	if (vma_iter_prealloc(&vmi, vma)) {
588  		pr_warn("Allocation of vma tree for process %d failed\n",
589  		       current->pid);
590  		return -ENOMEM;
591  	}
592  	cleanup_vma_from_mm(vma);
593  
594  	/* remove from the MM's tree and list */
595  	vma_iter_clear(&vmi);
596  	return 0;
597  }
598  /*
599   * destroy a VMA record
600   */
601  static void delete_vma(struct mm_struct *mm, struct vm_area_struct *vma)
602  {
603  	if (vma->vm_ops && vma->vm_ops->close)
604  		vma->vm_ops->close(vma);
605  	if (vma->vm_file)
606  		fput(vma->vm_file);
607  	put_nommu_region(vma->vm_region);
608  	vm_area_free(vma);
609  }
610  
611  struct vm_area_struct *find_vma_intersection(struct mm_struct *mm,
612  					     unsigned long start_addr,
613  					     unsigned long end_addr)
614  {
615  	unsigned long index = start_addr;
616  
617  	mmap_assert_locked(mm);
618  	return mt_find(&mm->mm_mt, &index, end_addr - 1);
619  }
620  EXPORT_SYMBOL(find_vma_intersection);
621  
622  /*
623   * look up the first VMA in which addr resides, NULL if none
624   * - should be called with mm->mmap_lock at least held readlocked
625   */
626  struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
627  {
628  	VMA_ITERATOR(vmi, mm, addr);
629  
630  	return vma_iter_load(&vmi);
631  }
632  EXPORT_SYMBOL(find_vma);
633  
634  /*
635   * At least xtensa ends up having protection faults even with no
636   * MMU.. No stack expansion, at least.
637   */
638  struct vm_area_struct *lock_mm_and_find_vma(struct mm_struct *mm,
639  			unsigned long addr, struct pt_regs *regs)
640  {
641  	struct vm_area_struct *vma;
642  
643  	mmap_read_lock(mm);
644  	vma = vma_lookup(mm, addr);
645  	if (!vma)
646  		mmap_read_unlock(mm);
647  	return vma;
648  }
649  
650  /*
651   * expand a stack to a given address
652   * - not supported under NOMMU conditions
653   */
654  int expand_stack_locked(struct vm_area_struct *vma, unsigned long addr)
655  {
656  	return -ENOMEM;
657  }
658  
659  struct vm_area_struct *expand_stack(struct mm_struct *mm, unsigned long addr)
660  {
661  	mmap_read_unlock(mm);
662  	return NULL;
663  }
664  
665  /*
666   * look up the first VMA exactly that exactly matches addr
667   * - should be called with mm->mmap_lock at least held readlocked
668   */
669  static struct vm_area_struct *find_vma_exact(struct mm_struct *mm,
670  					     unsigned long addr,
671  					     unsigned long len)
672  {
673  	struct vm_area_struct *vma;
674  	unsigned long end = addr + len;
675  	VMA_ITERATOR(vmi, mm, addr);
676  
677  	vma = vma_iter_load(&vmi);
678  	if (!vma)
679  		return NULL;
680  	if (vma->vm_start != addr)
681  		return NULL;
682  	if (vma->vm_end != end)
683  		return NULL;
684  
685  	return vma;
686  }
687  
688  /*
689   * determine whether a mapping should be permitted and, if so, what sort of
690   * mapping we're capable of supporting
691   */
692  static int validate_mmap_request(struct file *file,
693  				 unsigned long addr,
694  				 unsigned long len,
695  				 unsigned long prot,
696  				 unsigned long flags,
697  				 unsigned long pgoff,
698  				 unsigned long *_capabilities)
699  {
700  	unsigned long capabilities, rlen;
701  	int ret;
702  
703  	/* do the simple checks first */
704  	if (flags & MAP_FIXED)
705  		return -EINVAL;
706  
707  	if ((flags & MAP_TYPE) != MAP_PRIVATE &&
708  	    (flags & MAP_TYPE) != MAP_SHARED)
709  		return -EINVAL;
710  
711  	if (!len)
712  		return -EINVAL;
713  
714  	/* Careful about overflows.. */
715  	rlen = PAGE_ALIGN(len);
716  	if (!rlen || rlen > TASK_SIZE)
717  		return -ENOMEM;
718  
719  	/* offset overflow? */
720  	if ((pgoff + (rlen >> PAGE_SHIFT)) < pgoff)
721  		return -EOVERFLOW;
722  
723  	if (file) {
724  		/* files must support mmap */
725  		if (!file->f_op->mmap)
726  			return -ENODEV;
727  
728  		/* work out if what we've got could possibly be shared
729  		 * - we support chardevs that provide their own "memory"
730  		 * - we support files/blockdevs that are memory backed
731  		 */
732  		if (file->f_op->mmap_capabilities) {
733  			capabilities = file->f_op->mmap_capabilities(file);
734  		} else {
735  			/* no explicit capabilities set, so assume some
736  			 * defaults */
737  			switch (file_inode(file)->i_mode & S_IFMT) {
738  			case S_IFREG:
739  			case S_IFBLK:
740  				capabilities = NOMMU_MAP_COPY;
741  				break;
742  
743  			case S_IFCHR:
744  				capabilities =
745  					NOMMU_MAP_DIRECT |
746  					NOMMU_MAP_READ |
747  					NOMMU_MAP_WRITE;
748  				break;
749  
750  			default:
751  				return -EINVAL;
752  			}
753  		}
754  
755  		/* eliminate any capabilities that we can't support on this
756  		 * device */
757  		if (!file->f_op->get_unmapped_area)
758  			capabilities &= ~NOMMU_MAP_DIRECT;
759  		if (!(file->f_mode & FMODE_CAN_READ))
760  			capabilities &= ~NOMMU_MAP_COPY;
761  
762  		/* The file shall have been opened with read permission. */
763  		if (!(file->f_mode & FMODE_READ))
764  			return -EACCES;
765  
766  		if (flags & MAP_SHARED) {
767  			/* do checks for writing, appending and locking */
768  			if ((prot & PROT_WRITE) &&
769  			    !(file->f_mode & FMODE_WRITE))
770  				return -EACCES;
771  
772  			if (IS_APPEND(file_inode(file)) &&
773  			    (file->f_mode & FMODE_WRITE))
774  				return -EACCES;
775  
776  			if (!(capabilities & NOMMU_MAP_DIRECT))
777  				return -ENODEV;
778  
779  			/* we mustn't privatise shared mappings */
780  			capabilities &= ~NOMMU_MAP_COPY;
781  		} else {
782  			/* we're going to read the file into private memory we
783  			 * allocate */
784  			if (!(capabilities & NOMMU_MAP_COPY))
785  				return -ENODEV;
786  
787  			/* we don't permit a private writable mapping to be
788  			 * shared with the backing device */
789  			if (prot & PROT_WRITE)
790  				capabilities &= ~NOMMU_MAP_DIRECT;
791  		}
792  
793  		if (capabilities & NOMMU_MAP_DIRECT) {
794  			if (((prot & PROT_READ)  && !(capabilities & NOMMU_MAP_READ))  ||
795  			    ((prot & PROT_WRITE) && !(capabilities & NOMMU_MAP_WRITE)) ||
796  			    ((prot & PROT_EXEC)  && !(capabilities & NOMMU_MAP_EXEC))
797  			    ) {
798  				capabilities &= ~NOMMU_MAP_DIRECT;
799  				if (flags & MAP_SHARED) {
800  					pr_warn("MAP_SHARED not completely supported on !MMU\n");
801  					return -EINVAL;
802  				}
803  			}
804  		}
805  
806  		/* handle executable mappings and implied executable
807  		 * mappings */
808  		if (path_noexec(&file->f_path)) {
809  			if (prot & PROT_EXEC)
810  				return -EPERM;
811  		} else if ((prot & PROT_READ) && !(prot & PROT_EXEC)) {
812  			/* handle implication of PROT_EXEC by PROT_READ */
813  			if (current->personality & READ_IMPLIES_EXEC) {
814  				if (capabilities & NOMMU_MAP_EXEC)
815  					prot |= PROT_EXEC;
816  			}
817  		} else if ((prot & PROT_READ) &&
818  			 (prot & PROT_EXEC) &&
819  			 !(capabilities & NOMMU_MAP_EXEC)
820  			 ) {
821  			/* backing file is not executable, try to copy */
822  			capabilities &= ~NOMMU_MAP_DIRECT;
823  		}
824  	} else {
825  		/* anonymous mappings are always memory backed and can be
826  		 * privately mapped
827  		 */
828  		capabilities = NOMMU_MAP_COPY;
829  
830  		/* handle PROT_EXEC implication by PROT_READ */
831  		if ((prot & PROT_READ) &&
832  		    (current->personality & READ_IMPLIES_EXEC))
833  			prot |= PROT_EXEC;
834  	}
835  
836  	/* allow the security API to have its say */
837  	ret = security_mmap_addr(addr);
838  	if (ret < 0)
839  		return ret;
840  
841  	/* looks okay */
842  	*_capabilities = capabilities;
843  	return 0;
844  }
845  
846  /*
847   * we've determined that we can make the mapping, now translate what we
848   * now know into VMA flags
849   */
850  static unsigned long determine_vm_flags(struct file *file,
851  					unsigned long prot,
852  					unsigned long flags,
853  					unsigned long capabilities)
854  {
855  	unsigned long vm_flags;
856  
857  	vm_flags = calc_vm_prot_bits(prot, 0) | calc_vm_flag_bits(flags);
858  
859  	if (!file) {
860  		/*
861  		 * MAP_ANONYMOUS. MAP_SHARED is mapped to MAP_PRIVATE, because
862  		 * there is no fork().
863  		 */
864  		vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
865  	} else if (flags & MAP_PRIVATE) {
866  		/* MAP_PRIVATE file mapping */
867  		if (capabilities & NOMMU_MAP_DIRECT)
868  			vm_flags |= (capabilities & NOMMU_VMFLAGS);
869  		else
870  			vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
871  
872  		if (!(prot & PROT_WRITE) && !current->ptrace)
873  			/*
874  			 * R/O private file mapping which cannot be used to
875  			 * modify memory, especially also not via active ptrace
876  			 * (e.g., set breakpoints) or later by upgrading
877  			 * permissions (no mprotect()). We can try overlaying
878  			 * the file mapping, which will work e.g., on chardevs,
879  			 * ramfs/tmpfs/shmfs and romfs/cramf.
880  			 */
881  			vm_flags |= VM_MAYOVERLAY;
882  	} else {
883  		/* MAP_SHARED file mapping: NOMMU_MAP_DIRECT is set. */
884  		vm_flags |= VM_SHARED | VM_MAYSHARE |
885  			    (capabilities & NOMMU_VMFLAGS);
886  	}
887  
888  	return vm_flags;
889  }
890  
891  /*
892   * set up a shared mapping on a file (the driver or filesystem provides and
893   * pins the storage)
894   */
895  static int do_mmap_shared_file(struct vm_area_struct *vma)
896  {
897  	int ret;
898  
899  	ret = call_mmap(vma->vm_file, vma);
900  	if (ret == 0) {
901  		vma->vm_region->vm_top = vma->vm_region->vm_end;
902  		return 0;
903  	}
904  	if (ret != -ENOSYS)
905  		return ret;
906  
907  	/* getting -ENOSYS indicates that direct mmap isn't possible (as
908  	 * opposed to tried but failed) so we can only give a suitable error as
909  	 * it's not possible to make a private copy if MAP_SHARED was given */
910  	return -ENODEV;
911  }
912  
913  /*
914   * set up a private mapping or an anonymous shared mapping
915   */
916  static int do_mmap_private(struct vm_area_struct *vma,
917  			   struct vm_region *region,
918  			   unsigned long len,
919  			   unsigned long capabilities)
920  {
921  	unsigned long total, point;
922  	void *base;
923  	int ret, order;
924  
925  	/*
926  	 * Invoke the file's mapping function so that it can keep track of
927  	 * shared mappings on devices or memory. VM_MAYOVERLAY will be set if
928  	 * it may attempt to share, which will make is_nommu_shared_mapping()
929  	 * happy.
930  	 */
931  	if (capabilities & NOMMU_MAP_DIRECT) {
932  		ret = call_mmap(vma->vm_file, vma);
933  		/* shouldn't return success if we're not sharing */
934  		if (WARN_ON_ONCE(!is_nommu_shared_mapping(vma->vm_flags)))
935  			ret = -ENOSYS;
936  		if (ret == 0) {
937  			vma->vm_region->vm_top = vma->vm_region->vm_end;
938  			return 0;
939  		}
940  		if (ret != -ENOSYS)
941  			return ret;
942  
943  		/* getting an ENOSYS error indicates that direct mmap isn't
944  		 * possible (as opposed to tried but failed) so we'll try to
945  		 * make a private copy of the data and map that instead */
946  	}
947  
948  
949  	/* allocate some memory to hold the mapping
950  	 * - note that this may not return a page-aligned address if the object
951  	 *   we're allocating is smaller than a page
952  	 */
953  	order = get_order(len);
954  	total = 1 << order;
955  	point = len >> PAGE_SHIFT;
956  
957  	/* we don't want to allocate a power-of-2 sized page set */
958  	if (sysctl_nr_trim_pages && total - point >= sysctl_nr_trim_pages)
959  		total = point;
960  
961  	base = alloc_pages_exact(total << PAGE_SHIFT, GFP_KERNEL);
962  	if (!base)
963  		goto enomem;
964  
965  	atomic_long_add(total, &mmap_pages_allocated);
966  
967  	vm_flags_set(vma, VM_MAPPED_COPY);
968  	region->vm_flags = vma->vm_flags;
969  	region->vm_start = (unsigned long) base;
970  	region->vm_end   = region->vm_start + len;
971  	region->vm_top   = region->vm_start + (total << PAGE_SHIFT);
972  
973  	vma->vm_start = region->vm_start;
974  	vma->vm_end   = region->vm_start + len;
975  
976  	if (vma->vm_file) {
977  		/* read the contents of a file into the copy */
978  		loff_t fpos;
979  
980  		fpos = vma->vm_pgoff;
981  		fpos <<= PAGE_SHIFT;
982  
983  		ret = kernel_read(vma->vm_file, base, len, &fpos);
984  		if (ret < 0)
985  			goto error_free;
986  
987  		/* clear the last little bit */
988  		if (ret < len)
989  			memset(base + ret, 0, len - ret);
990  
991  	} else {
992  		vma_set_anonymous(vma);
993  	}
994  
995  	return 0;
996  
997  error_free:
998  	free_page_series(region->vm_start, region->vm_top);
999  	region->vm_start = vma->vm_start = 0;
1000  	region->vm_end   = vma->vm_end = 0;
1001  	region->vm_top   = 0;
1002  	return ret;
1003  
1004  enomem:
1005  	pr_err("Allocation of length %lu from process %d (%s) failed\n",
1006  	       len, current->pid, current->comm);
1007  	show_mem();
1008  	return -ENOMEM;
1009  }
1010  
1011  /*
1012   * handle mapping creation for uClinux
1013   */
1014  unsigned long do_mmap(struct file *file,
1015  			unsigned long addr,
1016  			unsigned long len,
1017  			unsigned long prot,
1018  			unsigned long flags,
1019  			vm_flags_t vm_flags,
1020  			unsigned long pgoff,
1021  			unsigned long *populate,
1022  			struct list_head *uf)
1023  {
1024  	struct vm_area_struct *vma;
1025  	struct vm_region *region;
1026  	struct rb_node *rb;
1027  	unsigned long capabilities, result;
1028  	int ret;
1029  	VMA_ITERATOR(vmi, current->mm, 0);
1030  
1031  	*populate = 0;
1032  
1033  	/* decide whether we should attempt the mapping, and if so what sort of
1034  	 * mapping */
1035  	ret = validate_mmap_request(file, addr, len, prot, flags, pgoff,
1036  				    &capabilities);
1037  	if (ret < 0)
1038  		return ret;
1039  
1040  	/* we ignore the address hint */
1041  	addr = 0;
1042  	len = PAGE_ALIGN(len);
1043  
1044  	/* we've determined that we can make the mapping, now translate what we
1045  	 * now know into VMA flags */
1046  	vm_flags |= determine_vm_flags(file, prot, flags, capabilities);
1047  
1048  
1049  	/* we're going to need to record the mapping */
1050  	region = kmem_cache_zalloc(vm_region_jar, GFP_KERNEL);
1051  	if (!region)
1052  		goto error_getting_region;
1053  
1054  	vma = vm_area_alloc(current->mm);
1055  	if (!vma)
1056  		goto error_getting_vma;
1057  
1058  	region->vm_usage = 1;
1059  	region->vm_flags = vm_flags;
1060  	region->vm_pgoff = pgoff;
1061  
1062  	vm_flags_init(vma, vm_flags);
1063  	vma->vm_pgoff = pgoff;
1064  
1065  	if (file) {
1066  		region->vm_file = get_file(file);
1067  		vma->vm_file = get_file(file);
1068  	}
1069  
1070  	down_write(&nommu_region_sem);
1071  
1072  	/* if we want to share, we need to check for regions created by other
1073  	 * mmap() calls that overlap with our proposed mapping
1074  	 * - we can only share with a superset match on most regular files
1075  	 * - shared mappings on character devices and memory backed files are
1076  	 *   permitted to overlap inexactly as far as we are concerned for in
1077  	 *   these cases, sharing is handled in the driver or filesystem rather
1078  	 *   than here
1079  	 */
1080  	if (is_nommu_shared_mapping(vm_flags)) {
1081  		struct vm_region *pregion;
1082  		unsigned long pglen, rpglen, pgend, rpgend, start;
1083  
1084  		pglen = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1085  		pgend = pgoff + pglen;
1086  
1087  		for (rb = rb_first(&nommu_region_tree); rb; rb = rb_next(rb)) {
1088  			pregion = rb_entry(rb, struct vm_region, vm_rb);
1089  
1090  			if (!is_nommu_shared_mapping(pregion->vm_flags))
1091  				continue;
1092  
1093  			/* search for overlapping mappings on the same file */
1094  			if (file_inode(pregion->vm_file) !=
1095  			    file_inode(file))
1096  				continue;
1097  
1098  			if (pregion->vm_pgoff >= pgend)
1099  				continue;
1100  
1101  			rpglen = pregion->vm_end - pregion->vm_start;
1102  			rpglen = (rpglen + PAGE_SIZE - 1) >> PAGE_SHIFT;
1103  			rpgend = pregion->vm_pgoff + rpglen;
1104  			if (pgoff >= rpgend)
1105  				continue;
1106  
1107  			/* handle inexactly overlapping matches between
1108  			 * mappings */
1109  			if ((pregion->vm_pgoff != pgoff || rpglen != pglen) &&
1110  			    !(pgoff >= pregion->vm_pgoff && pgend <= rpgend)) {
1111  				/* new mapping is not a subset of the region */
1112  				if (!(capabilities & NOMMU_MAP_DIRECT))
1113  					goto sharing_violation;
1114  				continue;
1115  			}
1116  
1117  			/* we've found a region we can share */
1118  			pregion->vm_usage++;
1119  			vma->vm_region = pregion;
1120  			start = pregion->vm_start;
1121  			start += (pgoff - pregion->vm_pgoff) << PAGE_SHIFT;
1122  			vma->vm_start = start;
1123  			vma->vm_end = start + len;
1124  
1125  			if (pregion->vm_flags & VM_MAPPED_COPY)
1126  				vm_flags_set(vma, VM_MAPPED_COPY);
1127  			else {
1128  				ret = do_mmap_shared_file(vma);
1129  				if (ret < 0) {
1130  					vma->vm_region = NULL;
1131  					vma->vm_start = 0;
1132  					vma->vm_end = 0;
1133  					pregion->vm_usage--;
1134  					pregion = NULL;
1135  					goto error_just_free;
1136  				}
1137  			}
1138  			fput(region->vm_file);
1139  			kmem_cache_free(vm_region_jar, region);
1140  			region = pregion;
1141  			result = start;
1142  			goto share;
1143  		}
1144  
1145  		/* obtain the address at which to make a shared mapping
1146  		 * - this is the hook for quasi-memory character devices to
1147  		 *   tell us the location of a shared mapping
1148  		 */
1149  		if (capabilities & NOMMU_MAP_DIRECT) {
1150  			addr = file->f_op->get_unmapped_area(file, addr, len,
1151  							     pgoff, flags);
1152  			if (IS_ERR_VALUE(addr)) {
1153  				ret = addr;
1154  				if (ret != -ENOSYS)
1155  					goto error_just_free;
1156  
1157  				/* the driver refused to tell us where to site
1158  				 * the mapping so we'll have to attempt to copy
1159  				 * it */
1160  				ret = -ENODEV;
1161  				if (!(capabilities & NOMMU_MAP_COPY))
1162  					goto error_just_free;
1163  
1164  				capabilities &= ~NOMMU_MAP_DIRECT;
1165  			} else {
1166  				vma->vm_start = region->vm_start = addr;
1167  				vma->vm_end = region->vm_end = addr + len;
1168  			}
1169  		}
1170  	}
1171  
1172  	vma->vm_region = region;
1173  
1174  	/* set up the mapping
1175  	 * - the region is filled in if NOMMU_MAP_DIRECT is still set
1176  	 */
1177  	if (file && vma->vm_flags & VM_SHARED)
1178  		ret = do_mmap_shared_file(vma);
1179  	else
1180  		ret = do_mmap_private(vma, region, len, capabilities);
1181  	if (ret < 0)
1182  		goto error_just_free;
1183  	add_nommu_region(region);
1184  
1185  	/* clear anonymous mappings that don't ask for uninitialized data */
1186  	if (!vma->vm_file &&
1187  	    (!IS_ENABLED(CONFIG_MMAP_ALLOW_UNINITIALIZED) ||
1188  	     !(flags & MAP_UNINITIALIZED)))
1189  		memset((void *)region->vm_start, 0,
1190  		       region->vm_end - region->vm_start);
1191  
1192  	/* okay... we have a mapping; now we have to register it */
1193  	result = vma->vm_start;
1194  
1195  	current->mm->total_vm += len >> PAGE_SHIFT;
1196  
1197  share:
1198  	BUG_ON(!vma->vm_region);
1199  	vma_iter_config(&vmi, vma->vm_start, vma->vm_end);
1200  	if (vma_iter_prealloc(&vmi, vma))
1201  		goto error_just_free;
1202  
1203  	setup_vma_to_mm(vma, current->mm);
1204  	current->mm->map_count++;
1205  	/* add the VMA to the tree */
1206  	vma_iter_store(&vmi, vma);
1207  
1208  	/* we flush the region from the icache only when the first executable
1209  	 * mapping of it is made  */
1210  	if (vma->vm_flags & VM_EXEC && !region->vm_icache_flushed) {
1211  		flush_icache_user_range(region->vm_start, region->vm_end);
1212  		region->vm_icache_flushed = true;
1213  	}
1214  
1215  	up_write(&nommu_region_sem);
1216  
1217  	return result;
1218  
1219  error_just_free:
1220  	up_write(&nommu_region_sem);
1221  error:
1222  	vma_iter_free(&vmi);
1223  	if (region->vm_file)
1224  		fput(region->vm_file);
1225  	kmem_cache_free(vm_region_jar, region);
1226  	if (vma->vm_file)
1227  		fput(vma->vm_file);
1228  	vm_area_free(vma);
1229  	return ret;
1230  
1231  sharing_violation:
1232  	up_write(&nommu_region_sem);
1233  	pr_warn("Attempt to share mismatched mappings\n");
1234  	ret = -EINVAL;
1235  	goto error;
1236  
1237  error_getting_vma:
1238  	kmem_cache_free(vm_region_jar, region);
1239  	pr_warn("Allocation of vma for %lu byte allocation from process %d failed\n",
1240  			len, current->pid);
1241  	show_mem();
1242  	return -ENOMEM;
1243  
1244  error_getting_region:
1245  	pr_warn("Allocation of vm region for %lu byte allocation from process %d failed\n",
1246  			len, current->pid);
1247  	show_mem();
1248  	return -ENOMEM;
1249  }
1250  
1251  unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
1252  			      unsigned long prot, unsigned long flags,
1253  			      unsigned long fd, unsigned long pgoff)
1254  {
1255  	struct file *file = NULL;
1256  	unsigned long retval = -EBADF;
1257  
1258  	audit_mmap_fd(fd, flags);
1259  	if (!(flags & MAP_ANONYMOUS)) {
1260  		file = fget(fd);
1261  		if (!file)
1262  			goto out;
1263  	}
1264  
1265  	retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
1266  
1267  	if (file)
1268  		fput(file);
1269  out:
1270  	return retval;
1271  }
1272  
1273  SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
1274  		unsigned long, prot, unsigned long, flags,
1275  		unsigned long, fd, unsigned long, pgoff)
1276  {
1277  	return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
1278  }
1279  
1280  #ifdef __ARCH_WANT_SYS_OLD_MMAP
1281  struct mmap_arg_struct {
1282  	unsigned long addr;
1283  	unsigned long len;
1284  	unsigned long prot;
1285  	unsigned long flags;
1286  	unsigned long fd;
1287  	unsigned long offset;
1288  };
1289  
1290  SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
1291  {
1292  	struct mmap_arg_struct a;
1293  
1294  	if (copy_from_user(&a, arg, sizeof(a)))
1295  		return -EFAULT;
1296  	if (offset_in_page(a.offset))
1297  		return -EINVAL;
1298  
1299  	return ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
1300  			       a.offset >> PAGE_SHIFT);
1301  }
1302  #endif /* __ARCH_WANT_SYS_OLD_MMAP */
1303  
1304  /*
1305   * split a vma into two pieces at address 'addr', a new vma is allocated either
1306   * for the first part or the tail.
1307   */
1308  int split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma,
1309  	      unsigned long addr, int new_below)
1310  {
1311  	struct vm_area_struct *new;
1312  	struct vm_region *region;
1313  	unsigned long npages;
1314  	struct mm_struct *mm;
1315  
1316  	/* we're only permitted to split anonymous regions (these should have
1317  	 * only a single usage on the region) */
1318  	if (vma->vm_file)
1319  		return -ENOMEM;
1320  
1321  	mm = vma->vm_mm;
1322  	if (mm->map_count >= sysctl_max_map_count)
1323  		return -ENOMEM;
1324  
1325  	region = kmem_cache_alloc(vm_region_jar, GFP_KERNEL);
1326  	if (!region)
1327  		return -ENOMEM;
1328  
1329  	new = vm_area_dup(vma);
1330  	if (!new)
1331  		goto err_vma_dup;
1332  
1333  	/* most fields are the same, copy all, and then fixup */
1334  	*region = *vma->vm_region;
1335  	new->vm_region = region;
1336  
1337  	npages = (addr - vma->vm_start) >> PAGE_SHIFT;
1338  
1339  	if (new_below) {
1340  		region->vm_top = region->vm_end = new->vm_end = addr;
1341  	} else {
1342  		region->vm_start = new->vm_start = addr;
1343  		region->vm_pgoff = new->vm_pgoff += npages;
1344  	}
1345  
1346  	vma_iter_config(vmi, new->vm_start, new->vm_end);
1347  	if (vma_iter_prealloc(vmi, vma)) {
1348  		pr_warn("Allocation of vma tree for process %d failed\n",
1349  			current->pid);
1350  		goto err_vmi_preallocate;
1351  	}
1352  
1353  	if (new->vm_ops && new->vm_ops->open)
1354  		new->vm_ops->open(new);
1355  
1356  	down_write(&nommu_region_sem);
1357  	delete_nommu_region(vma->vm_region);
1358  	if (new_below) {
1359  		vma->vm_region->vm_start = vma->vm_start = addr;
1360  		vma->vm_region->vm_pgoff = vma->vm_pgoff += npages;
1361  	} else {
1362  		vma->vm_region->vm_end = vma->vm_end = addr;
1363  		vma->vm_region->vm_top = addr;
1364  	}
1365  	add_nommu_region(vma->vm_region);
1366  	add_nommu_region(new->vm_region);
1367  	up_write(&nommu_region_sem);
1368  
1369  	setup_vma_to_mm(vma, mm);
1370  	setup_vma_to_mm(new, mm);
1371  	vma_iter_store(vmi, new);
1372  	mm->map_count++;
1373  	return 0;
1374  
1375  err_vmi_preallocate:
1376  	vm_area_free(new);
1377  err_vma_dup:
1378  	kmem_cache_free(vm_region_jar, region);
1379  	return -ENOMEM;
1380  }
1381  
1382  /*
1383   * shrink a VMA by removing the specified chunk from either the beginning or
1384   * the end
1385   */
1386  static int vmi_shrink_vma(struct vma_iterator *vmi,
1387  		      struct vm_area_struct *vma,
1388  		      unsigned long from, unsigned long to)
1389  {
1390  	struct vm_region *region;
1391  
1392  	/* adjust the VMA's pointers, which may reposition it in the MM's tree
1393  	 * and list */
1394  	if (from > vma->vm_start) {
1395  		if (vma_iter_clear_gfp(vmi, from, vma->vm_end, GFP_KERNEL))
1396  			return -ENOMEM;
1397  		vma->vm_end = from;
1398  	} else {
1399  		if (vma_iter_clear_gfp(vmi, vma->vm_start, to, GFP_KERNEL))
1400  			return -ENOMEM;
1401  		vma->vm_start = to;
1402  	}
1403  
1404  	/* cut the backing region down to size */
1405  	region = vma->vm_region;
1406  	BUG_ON(region->vm_usage != 1);
1407  
1408  	down_write(&nommu_region_sem);
1409  	delete_nommu_region(region);
1410  	if (from > region->vm_start) {
1411  		to = region->vm_top;
1412  		region->vm_top = region->vm_end = from;
1413  	} else {
1414  		region->vm_start = to;
1415  	}
1416  	add_nommu_region(region);
1417  	up_write(&nommu_region_sem);
1418  
1419  	free_page_series(from, to);
1420  	return 0;
1421  }
1422  
1423  /*
1424   * release a mapping
1425   * - under NOMMU conditions the chunk to be unmapped must be backed by a single
1426   *   VMA, though it need not cover the whole VMA
1427   */
1428  int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, struct list_head *uf)
1429  {
1430  	VMA_ITERATOR(vmi, mm, start);
1431  	struct vm_area_struct *vma;
1432  	unsigned long end;
1433  	int ret = 0;
1434  
1435  	len = PAGE_ALIGN(len);
1436  	if (len == 0)
1437  		return -EINVAL;
1438  
1439  	end = start + len;
1440  
1441  	/* find the first potentially overlapping VMA */
1442  	vma = vma_find(&vmi, end);
1443  	if (!vma) {
1444  		static int limit;
1445  		if (limit < 5) {
1446  			pr_warn("munmap of memory not mmapped by process %d (%s): 0x%lx-0x%lx\n",
1447  					current->pid, current->comm,
1448  					start, start + len - 1);
1449  			limit++;
1450  		}
1451  		return -EINVAL;
1452  	}
1453  
1454  	/* we're allowed to split an anonymous VMA but not a file-backed one */
1455  	if (vma->vm_file) {
1456  		do {
1457  			if (start > vma->vm_start)
1458  				return -EINVAL;
1459  			if (end == vma->vm_end)
1460  				goto erase_whole_vma;
1461  			vma = vma_find(&vmi, end);
1462  		} while (vma);
1463  		return -EINVAL;
1464  	} else {
1465  		/* the chunk must be a subset of the VMA found */
1466  		if (start == vma->vm_start && end == vma->vm_end)
1467  			goto erase_whole_vma;
1468  		if (start < vma->vm_start || end > vma->vm_end)
1469  			return -EINVAL;
1470  		if (offset_in_page(start))
1471  			return -EINVAL;
1472  		if (end != vma->vm_end && offset_in_page(end))
1473  			return -EINVAL;
1474  		if (start != vma->vm_start && end != vma->vm_end) {
1475  			ret = split_vma(&vmi, vma, start, 1);
1476  			if (ret < 0)
1477  				return ret;
1478  		}
1479  		return vmi_shrink_vma(&vmi, vma, start, end);
1480  	}
1481  
1482  erase_whole_vma:
1483  	if (delete_vma_from_mm(vma))
1484  		ret = -ENOMEM;
1485  	else
1486  		delete_vma(mm, vma);
1487  	return ret;
1488  }
1489  
1490  int vm_munmap(unsigned long addr, size_t len)
1491  {
1492  	struct mm_struct *mm = current->mm;
1493  	int ret;
1494  
1495  	mmap_write_lock(mm);
1496  	ret = do_munmap(mm, addr, len, NULL);
1497  	mmap_write_unlock(mm);
1498  	return ret;
1499  }
1500  EXPORT_SYMBOL(vm_munmap);
1501  
1502  SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
1503  {
1504  	return vm_munmap(addr, len);
1505  }
1506  
1507  /*
1508   * release all the mappings made in a process's VM space
1509   */
1510  void exit_mmap(struct mm_struct *mm)
1511  {
1512  	VMA_ITERATOR(vmi, mm, 0);
1513  	struct vm_area_struct *vma;
1514  
1515  	if (!mm)
1516  		return;
1517  
1518  	mm->total_vm = 0;
1519  
1520  	/*
1521  	 * Lock the mm to avoid assert complaining even though this is the only
1522  	 * user of the mm
1523  	 */
1524  	mmap_write_lock(mm);
1525  	for_each_vma(vmi, vma) {
1526  		cleanup_vma_from_mm(vma);
1527  		delete_vma(mm, vma);
1528  		cond_resched();
1529  	}
1530  	__mt_destroy(&mm->mm_mt);
1531  	mmap_write_unlock(mm);
1532  }
1533  
1534  int vm_brk(unsigned long addr, unsigned long len)
1535  {
1536  	return -ENOMEM;
1537  }
1538  
1539  /*
1540   * expand (or shrink) an existing mapping, potentially moving it at the same
1541   * time (controlled by the MREMAP_MAYMOVE flag and available VM space)
1542   *
1543   * under NOMMU conditions, we only permit changing a mapping's size, and only
1544   * as long as it stays within the region allocated by do_mmap_private() and the
1545   * block is not shareable
1546   *
1547   * MREMAP_FIXED is not supported under NOMMU conditions
1548   */
1549  static unsigned long do_mremap(unsigned long addr,
1550  			unsigned long old_len, unsigned long new_len,
1551  			unsigned long flags, unsigned long new_addr)
1552  {
1553  	struct vm_area_struct *vma;
1554  
1555  	/* insanity checks first */
1556  	old_len = PAGE_ALIGN(old_len);
1557  	new_len = PAGE_ALIGN(new_len);
1558  	if (old_len == 0 || new_len == 0)
1559  		return (unsigned long) -EINVAL;
1560  
1561  	if (offset_in_page(addr))
1562  		return -EINVAL;
1563  
1564  	if (flags & MREMAP_FIXED && new_addr != addr)
1565  		return (unsigned long) -EINVAL;
1566  
1567  	vma = find_vma_exact(current->mm, addr, old_len);
1568  	if (!vma)
1569  		return (unsigned long) -EINVAL;
1570  
1571  	if (vma->vm_end != vma->vm_start + old_len)
1572  		return (unsigned long) -EFAULT;
1573  
1574  	if (is_nommu_shared_mapping(vma->vm_flags))
1575  		return (unsigned long) -EPERM;
1576  
1577  	if (new_len > vma->vm_region->vm_end - vma->vm_region->vm_start)
1578  		return (unsigned long) -ENOMEM;
1579  
1580  	/* all checks complete - do it */
1581  	vma->vm_end = vma->vm_start + new_len;
1582  	return vma->vm_start;
1583  }
1584  
1585  SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
1586  		unsigned long, new_len, unsigned long, flags,
1587  		unsigned long, new_addr)
1588  {
1589  	unsigned long ret;
1590  
1591  	mmap_write_lock(current->mm);
1592  	ret = do_mremap(addr, old_len, new_len, flags, new_addr);
1593  	mmap_write_unlock(current->mm);
1594  	return ret;
1595  }
1596  
1597  struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
1598  			 unsigned int foll_flags)
1599  {
1600  	return NULL;
1601  }
1602  
1603  int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
1604  		unsigned long pfn, unsigned long size, pgprot_t prot)
1605  {
1606  	if (addr != (pfn << PAGE_SHIFT))
1607  		return -EINVAL;
1608  
1609  	vm_flags_set(vma, VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP);
1610  	return 0;
1611  }
1612  EXPORT_SYMBOL(remap_pfn_range);
1613  
1614  int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len)
1615  {
1616  	unsigned long pfn = start >> PAGE_SHIFT;
1617  	unsigned long vm_len = vma->vm_end - vma->vm_start;
1618  
1619  	pfn += vma->vm_pgoff;
1620  	return io_remap_pfn_range(vma, vma->vm_start, pfn, vm_len, vma->vm_page_prot);
1621  }
1622  EXPORT_SYMBOL(vm_iomap_memory);
1623  
1624  int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
1625  			unsigned long pgoff)
1626  {
1627  	unsigned int size = vma->vm_end - vma->vm_start;
1628  
1629  	if (!(vma->vm_flags & VM_USERMAP))
1630  		return -EINVAL;
1631  
1632  	vma->vm_start = (unsigned long)(addr + (pgoff << PAGE_SHIFT));
1633  	vma->vm_end = vma->vm_start + size;
1634  
1635  	return 0;
1636  }
1637  EXPORT_SYMBOL(remap_vmalloc_range);
1638  
1639  vm_fault_t filemap_fault(struct vm_fault *vmf)
1640  {
1641  	BUG();
1642  	return 0;
1643  }
1644  EXPORT_SYMBOL(filemap_fault);
1645  
1646  vm_fault_t filemap_map_pages(struct vm_fault *vmf,
1647  		pgoff_t start_pgoff, pgoff_t end_pgoff)
1648  {
1649  	BUG();
1650  	return 0;
1651  }
1652  EXPORT_SYMBOL(filemap_map_pages);
1653  
1654  int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf,
1655  		       int len, unsigned int gup_flags)
1656  {
1657  	struct vm_area_struct *vma;
1658  	int write = gup_flags & FOLL_WRITE;
1659  
1660  	if (mmap_read_lock_killable(mm))
1661  		return 0;
1662  
1663  	/* the access must start within one of the target process's mappings */
1664  	vma = find_vma(mm, addr);
1665  	if (vma) {
1666  		/* don't overrun this mapping */
1667  		if (addr + len >= vma->vm_end)
1668  			len = vma->vm_end - addr;
1669  
1670  		/* only read or write mappings where it is permitted */
1671  		if (write && vma->vm_flags & VM_MAYWRITE)
1672  			copy_to_user_page(vma, NULL, addr,
1673  					 (void *) addr, buf, len);
1674  		else if (!write && vma->vm_flags & VM_MAYREAD)
1675  			copy_from_user_page(vma, NULL, addr,
1676  					    buf, (void *) addr, len);
1677  		else
1678  			len = 0;
1679  	} else {
1680  		len = 0;
1681  	}
1682  
1683  	mmap_read_unlock(mm);
1684  
1685  	return len;
1686  }
1687  
1688  /**
1689   * access_remote_vm - access another process' address space
1690   * @mm:		the mm_struct of the target address space
1691   * @addr:	start address to access
1692   * @buf:	source or destination buffer
1693   * @len:	number of bytes to transfer
1694   * @gup_flags:	flags modifying lookup behaviour
1695   *
1696   * The caller must hold a reference on @mm.
1697   */
1698  int access_remote_vm(struct mm_struct *mm, unsigned long addr,
1699  		void *buf, int len, unsigned int gup_flags)
1700  {
1701  	return __access_remote_vm(mm, addr, buf, len, gup_flags);
1702  }
1703  
1704  /*
1705   * Access another process' address space.
1706   * - source/target buffer must be kernel space
1707   */
1708  int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len,
1709  		unsigned int gup_flags)
1710  {
1711  	struct mm_struct *mm;
1712  
1713  	if (addr + len < addr)
1714  		return 0;
1715  
1716  	mm = get_task_mm(tsk);
1717  	if (!mm)
1718  		return 0;
1719  
1720  	len = __access_remote_vm(mm, addr, buf, len, gup_flags);
1721  
1722  	mmput(mm);
1723  	return len;
1724  }
1725  EXPORT_SYMBOL_GPL(access_process_vm);
1726  
1727  /**
1728   * nommu_shrink_inode_mappings - Shrink the shared mappings on an inode
1729   * @inode: The inode to check
1730   * @size: The current filesize of the inode
1731   * @newsize: The proposed filesize of the inode
1732   *
1733   * Check the shared mappings on an inode on behalf of a shrinking truncate to
1734   * make sure that any outstanding VMAs aren't broken and then shrink the
1735   * vm_regions that extend beyond so that do_mmap() doesn't
1736   * automatically grant mappings that are too large.
1737   */
1738  int nommu_shrink_inode_mappings(struct inode *inode, size_t size,
1739  				size_t newsize)
1740  {
1741  	struct vm_area_struct *vma;
1742  	struct vm_region *region;
1743  	pgoff_t low, high;
1744  	size_t r_size, r_top;
1745  
1746  	low = newsize >> PAGE_SHIFT;
1747  	high = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1748  
1749  	down_write(&nommu_region_sem);
1750  	i_mmap_lock_read(inode->i_mapping);
1751  
1752  	/* search for VMAs that fall within the dead zone */
1753  	vma_interval_tree_foreach(vma, &inode->i_mapping->i_mmap, low, high) {
1754  		/* found one - only interested if it's shared out of the page
1755  		 * cache */
1756  		if (vma->vm_flags & VM_SHARED) {
1757  			i_mmap_unlock_read(inode->i_mapping);
1758  			up_write(&nommu_region_sem);
1759  			return -ETXTBSY; /* not quite true, but near enough */
1760  		}
1761  	}
1762  
1763  	/* reduce any regions that overlap the dead zone - if in existence,
1764  	 * these will be pointed to by VMAs that don't overlap the dead zone
1765  	 *
1766  	 * we don't check for any regions that start beyond the EOF as there
1767  	 * shouldn't be any
1768  	 */
1769  	vma_interval_tree_foreach(vma, &inode->i_mapping->i_mmap, 0, ULONG_MAX) {
1770  		if (!(vma->vm_flags & VM_SHARED))
1771  			continue;
1772  
1773  		region = vma->vm_region;
1774  		r_size = region->vm_top - region->vm_start;
1775  		r_top = (region->vm_pgoff << PAGE_SHIFT) + r_size;
1776  
1777  		if (r_top > newsize) {
1778  			region->vm_top -= r_top - newsize;
1779  			if (region->vm_end > region->vm_top)
1780  				region->vm_end = region->vm_top;
1781  		}
1782  	}
1783  
1784  	i_mmap_unlock_read(inode->i_mapping);
1785  	up_write(&nommu_region_sem);
1786  	return 0;
1787  }
1788  
1789  /*
1790   * Initialise sysctl_user_reserve_kbytes.
1791   *
1792   * This is intended to prevent a user from starting a single memory hogging
1793   * process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER
1794   * mode.
1795   *
1796   * The default value is min(3% of free memory, 128MB)
1797   * 128MB is enough to recover with sshd/login, bash, and top/kill.
1798   */
1799  static int __meminit init_user_reserve(void)
1800  {
1801  	unsigned long free_kbytes;
1802  
1803  	free_kbytes = K(global_zone_page_state(NR_FREE_PAGES));
1804  
1805  	sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17);
1806  	return 0;
1807  }
1808  subsys_initcall(init_user_reserve);
1809  
1810  /*
1811   * Initialise sysctl_admin_reserve_kbytes.
1812   *
1813   * The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin
1814   * to log in and kill a memory hogging process.
1815   *
1816   * Systems with more than 256MB will reserve 8MB, enough to recover
1817   * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
1818   * only reserve 3% of free pages by default.
1819   */
1820  static int __meminit init_admin_reserve(void)
1821  {
1822  	unsigned long free_kbytes;
1823  
1824  	free_kbytes = K(global_zone_page_state(NR_FREE_PAGES));
1825  
1826  	sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
1827  	return 0;
1828  }
1829  subsys_initcall(init_admin_reserve);
1830