xref: /openbmc/linux/mm/nommu.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
1 /*
2  *  linux/mm/nommu.c
3  *
4  *  Replacement code for mm functions to support CPU's that don't
5  *  have any form of memory management unit (thus no virtual memory).
6  *
7  *  See Documentation/nommu-mmap.txt
8  *
9  *  Copyright (c) 2004-2005 David Howells <dhowells@redhat.com>
10  *  Copyright (c) 2000-2003 David McCullough <davidm@snapgear.com>
11  *  Copyright (c) 2000-2001 D Jeff Dionne <jeff@uClinux.org>
12  *  Copyright (c) 2002      Greg Ungerer <gerg@snapgear.com>
13  */
14 
15 #include <linux/mm.h>
16 #include <linux/mman.h>
17 #include <linux/swap.h>
18 #include <linux/file.h>
19 #include <linux/highmem.h>
20 #include <linux/pagemap.h>
21 #include <linux/slab.h>
22 #include <linux/vmalloc.h>
23 #include <linux/ptrace.h>
24 #include <linux/blkdev.h>
25 #include <linux/backing-dev.h>
26 #include <linux/mount.h>
27 #include <linux/personality.h>
28 #include <linux/security.h>
29 #include <linux/syscalls.h>
30 
31 #include <asm/uaccess.h>
32 #include <asm/tlb.h>
33 #include <asm/tlbflush.h>
34 
35 void *high_memory;
36 struct page *mem_map;
37 unsigned long max_mapnr;
38 unsigned long num_physpages;
39 unsigned long askedalloc, realalloc;
40 atomic_t vm_committed_space = ATOMIC_INIT(0);
41 int sysctl_overcommit_memory = OVERCOMMIT_GUESS; /* heuristic overcommit */
42 int sysctl_overcommit_ratio = 50; /* default is 50% */
43 int sysctl_max_map_count = DEFAULT_MAX_MAP_COUNT;
44 int heap_stack_gap = 0;
45 
46 EXPORT_SYMBOL(mem_map);
47 EXPORT_SYMBOL(__vm_enough_memory);
48 EXPORT_SYMBOL(num_physpages);
49 
50 /* list of shareable VMAs */
51 struct rb_root nommu_vma_tree = RB_ROOT;
52 DECLARE_RWSEM(nommu_vma_sem);
53 
54 struct vm_operations_struct generic_file_vm_ops = {
55 };
56 
57 EXPORT_SYMBOL(vfree);
58 EXPORT_SYMBOL(vmalloc_to_page);
59 EXPORT_SYMBOL(vmalloc_32);
60 EXPORT_SYMBOL(vmap);
61 EXPORT_SYMBOL(vunmap);
62 
63 /*
64  * Handle all mappings that got truncated by a "truncate()"
65  * system call.
66  *
67  * NOTE! We have to be ready to update the memory sharing
68  * between the file and the memory map for a potential last
69  * incomplete page.  Ugly, but necessary.
70  */
71 int vmtruncate(struct inode *inode, loff_t offset)
72 {
73 	struct address_space *mapping = inode->i_mapping;
74 	unsigned long limit;
75 
76 	if (inode->i_size < offset)
77 		goto do_expand;
78 	i_size_write(inode, offset);
79 
80 	truncate_inode_pages(mapping, offset);
81 	goto out_truncate;
82 
83 do_expand:
84 	limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
85 	if (limit != RLIM_INFINITY && offset > limit)
86 		goto out_sig;
87 	if (offset > inode->i_sb->s_maxbytes)
88 		goto out;
89 	i_size_write(inode, offset);
90 
91 out_truncate:
92 	if (inode->i_op && inode->i_op->truncate)
93 		inode->i_op->truncate(inode);
94 	return 0;
95 out_sig:
96 	send_sig(SIGXFSZ, current, 0);
97 out:
98 	return -EFBIG;
99 }
100 
101 EXPORT_SYMBOL(vmtruncate);
102 
103 /*
104  * Return the total memory allocated for this pointer, not
105  * just what the caller asked for.
106  *
107  * Doesn't have to be accurate, i.e. may have races.
108  */
109 unsigned int kobjsize(const void *objp)
110 {
111 	struct page *page;
112 
113 	if (!objp || !((page = virt_to_page(objp))))
114 		return 0;
115 
116 	if (PageSlab(page))
117 		return ksize(objp);
118 
119 	BUG_ON(page->index < 0);
120 	BUG_ON(page->index >= MAX_ORDER);
121 
122 	return (PAGE_SIZE << page->index);
123 }
124 
125 /*
126  * get a list of pages in an address range belonging to the specified process
127  * and indicate the VMA that covers each page
128  * - this is potentially dodgy as we may end incrementing the page count of a
129  *   slab page or a secondary page from a compound page
130  * - don't permit access to VMAs that don't support it, such as I/O mappings
131  */
132 int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
133 	unsigned long start, int len, int write, int force,
134 	struct page **pages, struct vm_area_struct **vmas)
135 {
136 	struct vm_area_struct *vma;
137 	unsigned long vm_flags;
138 	int i;
139 
140 	/* calculate required read or write permissions.
141 	 * - if 'force' is set, we only require the "MAY" flags.
142 	 */
143 	vm_flags  = write ? (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
144 	vm_flags &= force ? (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
145 
146 	for (i = 0; i < len; i++) {
147 		vma = find_vma(mm, start);
148 		if (!vma)
149 			goto finish_or_fault;
150 
151 		/* protect what we can, including chardevs */
152 		if (vma->vm_flags & (VM_IO | VM_PFNMAP) ||
153 		    !(vm_flags & vma->vm_flags))
154 			goto finish_or_fault;
155 
156 		if (pages) {
157 			pages[i] = virt_to_page(start);
158 			if (pages[i])
159 				page_cache_get(pages[i]);
160 		}
161 		if (vmas)
162 			vmas[i] = vma;
163 		start += PAGE_SIZE;
164 	}
165 
166 	return i;
167 
168 finish_or_fault:
169 	return i ? : -EFAULT;
170 }
171 
172 EXPORT_SYMBOL(get_user_pages);
173 
174 DEFINE_RWLOCK(vmlist_lock);
175 struct vm_struct *vmlist;
176 
177 void vfree(void *addr)
178 {
179 	kfree(addr);
180 }
181 
182 void *__vmalloc(unsigned long size, gfp_t gfp_mask, pgprot_t prot)
183 {
184 	/*
185 	 * kmalloc doesn't like __GFP_HIGHMEM for some reason
186 	 */
187 	return kmalloc(size, (gfp_mask | __GFP_COMP) & ~__GFP_HIGHMEM);
188 }
189 
190 struct page * vmalloc_to_page(void *addr)
191 {
192 	return virt_to_page(addr);
193 }
194 
195 unsigned long vmalloc_to_pfn(void *addr)
196 {
197 	return page_to_pfn(virt_to_page(addr));
198 }
199 
200 
201 long vread(char *buf, char *addr, unsigned long count)
202 {
203 	memcpy(buf, addr, count);
204 	return count;
205 }
206 
207 long vwrite(char *buf, char *addr, unsigned long count)
208 {
209 	/* Don't allow overflow */
210 	if ((unsigned long) addr + count < count)
211 		count = -(unsigned long) addr;
212 
213 	memcpy(addr, buf, count);
214 	return(count);
215 }
216 
217 /*
218  *	vmalloc  -  allocate virtually continguos memory
219  *
220  *	@size:		allocation size
221  *
222  *	Allocate enough pages to cover @size from the page level
223  *	allocator and map them into continguos kernel virtual space.
224  *
225  *	For tight control over page level allocator and protection flags
226  *	use __vmalloc() instead.
227  */
228 void *vmalloc(unsigned long size)
229 {
230        return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL);
231 }
232 EXPORT_SYMBOL(vmalloc);
233 
234 void *vmalloc_node(unsigned long size, int node)
235 {
236 	return vmalloc(size);
237 }
238 EXPORT_SYMBOL(vmalloc_node);
239 
240 /*
241  *	vmalloc_32  -  allocate virtually continguos memory (32bit addressable)
242  *
243  *	@size:		allocation size
244  *
245  *	Allocate enough 32bit PA addressable pages to cover @size from the
246  *	page level allocator and map them into continguos kernel virtual space.
247  */
248 void *vmalloc_32(unsigned long size)
249 {
250 	return __vmalloc(size, GFP_KERNEL, PAGE_KERNEL);
251 }
252 
253 void *vmap(struct page **pages, unsigned int count, unsigned long flags, pgprot_t prot)
254 {
255 	BUG();
256 	return NULL;
257 }
258 
259 void vunmap(void *addr)
260 {
261 	BUG();
262 }
263 
264 /*
265  * Implement a stub for vmalloc_sync_all() if the architecture chose not to
266  * have one.
267  */
268 void  __attribute__((weak)) vmalloc_sync_all(void)
269 {
270 }
271 
272 /*
273  *  sys_brk() for the most part doesn't need the global kernel
274  *  lock, except when an application is doing something nasty
275  *  like trying to un-brk an area that has already been mapped
276  *  to a regular file.  in this case, the unmapping will need
277  *  to invoke file system routines that need the global lock.
278  */
279 asmlinkage unsigned long sys_brk(unsigned long brk)
280 {
281 	struct mm_struct *mm = current->mm;
282 
283 	if (brk < mm->start_brk || brk > mm->context.end_brk)
284 		return mm->brk;
285 
286 	if (mm->brk == brk)
287 		return mm->brk;
288 
289 	/*
290 	 * Always allow shrinking brk
291 	 */
292 	if (brk <= mm->brk) {
293 		mm->brk = brk;
294 		return brk;
295 	}
296 
297 	/*
298 	 * Ok, looks good - let it rip.
299 	 */
300 	return mm->brk = brk;
301 }
302 
303 #ifdef DEBUG
304 static void show_process_blocks(void)
305 {
306 	struct vm_list_struct *vml;
307 
308 	printk("Process blocks %d:", current->pid);
309 
310 	for (vml = &current->mm->context.vmlist; vml; vml = vml->next) {
311 		printk(" %p: %p", vml, vml->vma);
312 		if (vml->vma)
313 			printk(" (%d @%lx #%d)",
314 			       kobjsize((void *) vml->vma->vm_start),
315 			       vml->vma->vm_start,
316 			       atomic_read(&vml->vma->vm_usage));
317 		printk(vml->next ? " ->" : ".\n");
318 	}
319 }
320 #endif /* DEBUG */
321 
322 /*
323  * add a VMA into a process's mm_struct in the appropriate place in the list
324  * - should be called with mm->mmap_sem held writelocked
325  */
326 static void add_vma_to_mm(struct mm_struct *mm, struct vm_list_struct *vml)
327 {
328 	struct vm_list_struct **ppv;
329 
330 	for (ppv = &current->mm->context.vmlist; *ppv; ppv = &(*ppv)->next)
331 		if ((*ppv)->vma->vm_start > vml->vma->vm_start)
332 			break;
333 
334 	vml->next = *ppv;
335 	*ppv = vml;
336 }
337 
338 /*
339  * look up the first VMA in which addr resides, NULL if none
340  * - should be called with mm->mmap_sem at least held readlocked
341  */
342 struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
343 {
344 	struct vm_list_struct *loop, *vml;
345 
346 	/* search the vm_start ordered list */
347 	vml = NULL;
348 	for (loop = mm->context.vmlist; loop; loop = loop->next) {
349 		if (loop->vma->vm_start > addr)
350 			break;
351 		vml = loop;
352 	}
353 
354 	if (vml && vml->vma->vm_end > addr)
355 		return vml->vma;
356 
357 	return NULL;
358 }
359 EXPORT_SYMBOL(find_vma);
360 
361 /*
362  * find a VMA
363  * - we don't extend stack VMAs under NOMMU conditions
364  */
365 struct vm_area_struct *find_extend_vma(struct mm_struct *mm, unsigned long addr)
366 {
367 	return find_vma(mm, addr);
368 }
369 
370 /*
371  * look up the first VMA exactly that exactly matches addr
372  * - should be called with mm->mmap_sem at least held readlocked
373  */
374 static inline struct vm_area_struct *find_vma_exact(struct mm_struct *mm,
375 						    unsigned long addr)
376 {
377 	struct vm_list_struct *vml;
378 
379 	/* search the vm_start ordered list */
380 	for (vml = mm->context.vmlist; vml; vml = vml->next) {
381 		if (vml->vma->vm_start == addr)
382 			return vml->vma;
383 		if (vml->vma->vm_start > addr)
384 			break;
385 	}
386 
387 	return NULL;
388 }
389 
390 /*
391  * find a VMA in the global tree
392  */
393 static inline struct vm_area_struct *find_nommu_vma(unsigned long start)
394 {
395 	struct vm_area_struct *vma;
396 	struct rb_node *n = nommu_vma_tree.rb_node;
397 
398 	while (n) {
399 		vma = rb_entry(n, struct vm_area_struct, vm_rb);
400 
401 		if (start < vma->vm_start)
402 			n = n->rb_left;
403 		else if (start > vma->vm_start)
404 			n = n->rb_right;
405 		else
406 			return vma;
407 	}
408 
409 	return NULL;
410 }
411 
412 /*
413  * add a VMA in the global tree
414  */
415 static void add_nommu_vma(struct vm_area_struct *vma)
416 {
417 	struct vm_area_struct *pvma;
418 	struct address_space *mapping;
419 	struct rb_node **p = &nommu_vma_tree.rb_node;
420 	struct rb_node *parent = NULL;
421 
422 	/* add the VMA to the mapping */
423 	if (vma->vm_file) {
424 		mapping = vma->vm_file->f_mapping;
425 
426 		flush_dcache_mmap_lock(mapping);
427 		vma_prio_tree_insert(vma, &mapping->i_mmap);
428 		flush_dcache_mmap_unlock(mapping);
429 	}
430 
431 	/* add the VMA to the master list */
432 	while (*p) {
433 		parent = *p;
434 		pvma = rb_entry(parent, struct vm_area_struct, vm_rb);
435 
436 		if (vma->vm_start < pvma->vm_start) {
437 			p = &(*p)->rb_left;
438 		}
439 		else if (vma->vm_start > pvma->vm_start) {
440 			p = &(*p)->rb_right;
441 		}
442 		else {
443 			/* mappings are at the same address - this can only
444 			 * happen for shared-mem chardevs and shared file
445 			 * mappings backed by ramfs/tmpfs */
446 			BUG_ON(!(pvma->vm_flags & VM_SHARED));
447 
448 			if (vma < pvma)
449 				p = &(*p)->rb_left;
450 			else if (vma > pvma)
451 				p = &(*p)->rb_right;
452 			else
453 				BUG();
454 		}
455 	}
456 
457 	rb_link_node(&vma->vm_rb, parent, p);
458 	rb_insert_color(&vma->vm_rb, &nommu_vma_tree);
459 }
460 
461 /*
462  * delete a VMA from the global list
463  */
464 static void delete_nommu_vma(struct vm_area_struct *vma)
465 {
466 	struct address_space *mapping;
467 
468 	/* remove the VMA from the mapping */
469 	if (vma->vm_file) {
470 		mapping = vma->vm_file->f_mapping;
471 
472 		flush_dcache_mmap_lock(mapping);
473 		vma_prio_tree_remove(vma, &mapping->i_mmap);
474 		flush_dcache_mmap_unlock(mapping);
475 	}
476 
477 	/* remove from the master list */
478 	rb_erase(&vma->vm_rb, &nommu_vma_tree);
479 }
480 
481 /*
482  * determine whether a mapping should be permitted and, if so, what sort of
483  * mapping we're capable of supporting
484  */
485 static int validate_mmap_request(struct file *file,
486 				 unsigned long addr,
487 				 unsigned long len,
488 				 unsigned long prot,
489 				 unsigned long flags,
490 				 unsigned long pgoff,
491 				 unsigned long *_capabilities)
492 {
493 	unsigned long capabilities;
494 	unsigned long reqprot = prot;
495 	int ret;
496 
497 	/* do the simple checks first */
498 	if (flags & MAP_FIXED || addr) {
499 		printk(KERN_DEBUG
500 		       "%d: Can't do fixed-address/overlay mmap of RAM\n",
501 		       current->pid);
502 		return -EINVAL;
503 	}
504 
505 	if ((flags & MAP_TYPE) != MAP_PRIVATE &&
506 	    (flags & MAP_TYPE) != MAP_SHARED)
507 		return -EINVAL;
508 
509 	if (!len)
510 		return -EINVAL;
511 
512 	/* Careful about overflows.. */
513 	len = PAGE_ALIGN(len);
514 	if (!len || len > TASK_SIZE)
515 		return -ENOMEM;
516 
517 	/* offset overflow? */
518 	if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
519 		return -EOVERFLOW;
520 
521 	if (file) {
522 		/* validate file mapping requests */
523 		struct address_space *mapping;
524 
525 		/* files must support mmap */
526 		if (!file->f_op || !file->f_op->mmap)
527 			return -ENODEV;
528 
529 		/* work out if what we've got could possibly be shared
530 		 * - we support chardevs that provide their own "memory"
531 		 * - we support files/blockdevs that are memory backed
532 		 */
533 		mapping = file->f_mapping;
534 		if (!mapping)
535 			mapping = file->f_path.dentry->d_inode->i_mapping;
536 
537 		capabilities = 0;
538 		if (mapping && mapping->backing_dev_info)
539 			capabilities = mapping->backing_dev_info->capabilities;
540 
541 		if (!capabilities) {
542 			/* no explicit capabilities set, so assume some
543 			 * defaults */
544 			switch (file->f_path.dentry->d_inode->i_mode & S_IFMT) {
545 			case S_IFREG:
546 			case S_IFBLK:
547 				capabilities = BDI_CAP_MAP_COPY;
548 				break;
549 
550 			case S_IFCHR:
551 				capabilities =
552 					BDI_CAP_MAP_DIRECT |
553 					BDI_CAP_READ_MAP |
554 					BDI_CAP_WRITE_MAP;
555 				break;
556 
557 			default:
558 				return -EINVAL;
559 			}
560 		}
561 
562 		/* eliminate any capabilities that we can't support on this
563 		 * device */
564 		if (!file->f_op->get_unmapped_area)
565 			capabilities &= ~BDI_CAP_MAP_DIRECT;
566 		if (!file->f_op->read)
567 			capabilities &= ~BDI_CAP_MAP_COPY;
568 
569 		if (flags & MAP_SHARED) {
570 			/* do checks for writing, appending and locking */
571 			if ((prot & PROT_WRITE) &&
572 			    !(file->f_mode & FMODE_WRITE))
573 				return -EACCES;
574 
575 			if (IS_APPEND(file->f_path.dentry->d_inode) &&
576 			    (file->f_mode & FMODE_WRITE))
577 				return -EACCES;
578 
579 			if (locks_verify_locked(file->f_path.dentry->d_inode))
580 				return -EAGAIN;
581 
582 			if (!(capabilities & BDI_CAP_MAP_DIRECT))
583 				return -ENODEV;
584 
585 			if (((prot & PROT_READ)  && !(capabilities & BDI_CAP_READ_MAP))  ||
586 			    ((prot & PROT_WRITE) && !(capabilities & BDI_CAP_WRITE_MAP)) ||
587 			    ((prot & PROT_EXEC)  && !(capabilities & BDI_CAP_EXEC_MAP))
588 			    ) {
589 				printk("MAP_SHARED not completely supported on !MMU\n");
590 				return -EINVAL;
591 			}
592 
593 			/* we mustn't privatise shared mappings */
594 			capabilities &= ~BDI_CAP_MAP_COPY;
595 		}
596 		else {
597 			/* we're going to read the file into private memory we
598 			 * allocate */
599 			if (!(capabilities & BDI_CAP_MAP_COPY))
600 				return -ENODEV;
601 
602 			/* we don't permit a private writable mapping to be
603 			 * shared with the backing device */
604 			if (prot & PROT_WRITE)
605 				capabilities &= ~BDI_CAP_MAP_DIRECT;
606 		}
607 
608 		/* handle executable mappings and implied executable
609 		 * mappings */
610 		if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) {
611 			if (prot & PROT_EXEC)
612 				return -EPERM;
613 		}
614 		else if ((prot & PROT_READ) && !(prot & PROT_EXEC)) {
615 			/* handle implication of PROT_EXEC by PROT_READ */
616 			if (current->personality & READ_IMPLIES_EXEC) {
617 				if (capabilities & BDI_CAP_EXEC_MAP)
618 					prot |= PROT_EXEC;
619 			}
620 		}
621 		else if ((prot & PROT_READ) &&
622 			 (prot & PROT_EXEC) &&
623 			 !(capabilities & BDI_CAP_EXEC_MAP)
624 			 ) {
625 			/* backing file is not executable, try to copy */
626 			capabilities &= ~BDI_CAP_MAP_DIRECT;
627 		}
628 	}
629 	else {
630 		/* anonymous mappings are always memory backed and can be
631 		 * privately mapped
632 		 */
633 		capabilities = BDI_CAP_MAP_COPY;
634 
635 		/* handle PROT_EXEC implication by PROT_READ */
636 		if ((prot & PROT_READ) &&
637 		    (current->personality & READ_IMPLIES_EXEC))
638 			prot |= PROT_EXEC;
639 	}
640 
641 	/* allow the security API to have its say */
642 	ret = security_file_mmap(file, reqprot, prot, flags);
643 	if (ret < 0)
644 		return ret;
645 
646 	/* looks okay */
647 	*_capabilities = capabilities;
648 	return 0;
649 }
650 
651 /*
652  * we've determined that we can make the mapping, now translate what we
653  * now know into VMA flags
654  */
655 static unsigned long determine_vm_flags(struct file *file,
656 					unsigned long prot,
657 					unsigned long flags,
658 					unsigned long capabilities)
659 {
660 	unsigned long vm_flags;
661 
662 	vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags);
663 	vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
664 	/* vm_flags |= mm->def_flags; */
665 
666 	if (!(capabilities & BDI_CAP_MAP_DIRECT)) {
667 		/* attempt to share read-only copies of mapped file chunks */
668 		if (file && !(prot & PROT_WRITE))
669 			vm_flags |= VM_MAYSHARE;
670 	}
671 	else {
672 		/* overlay a shareable mapping on the backing device or inode
673 		 * if possible - used for chardevs, ramfs/tmpfs/shmfs and
674 		 * romfs/cramfs */
675 		if (flags & MAP_SHARED)
676 			vm_flags |= VM_MAYSHARE | VM_SHARED;
677 		else if ((((vm_flags & capabilities) ^ vm_flags) & BDI_CAP_VMFLAGS) == 0)
678 			vm_flags |= VM_MAYSHARE;
679 	}
680 
681 	/* refuse to let anyone share private mappings with this process if
682 	 * it's being traced - otherwise breakpoints set in it may interfere
683 	 * with another untraced process
684 	 */
685 	if ((flags & MAP_PRIVATE) && (current->ptrace & PT_PTRACED))
686 		vm_flags &= ~VM_MAYSHARE;
687 
688 	return vm_flags;
689 }
690 
691 /*
692  * set up a shared mapping on a file
693  */
694 static int do_mmap_shared_file(struct vm_area_struct *vma, unsigned long len)
695 {
696 	int ret;
697 
698 	ret = vma->vm_file->f_op->mmap(vma->vm_file, vma);
699 	if (ret != -ENOSYS)
700 		return ret;
701 
702 	/* getting an ENOSYS error indicates that direct mmap isn't
703 	 * possible (as opposed to tried but failed) so we'll fall
704 	 * through to making a private copy of the data and mapping
705 	 * that if we can */
706 	return -ENODEV;
707 }
708 
709 /*
710  * set up a private mapping or an anonymous shared mapping
711  */
712 static int do_mmap_private(struct vm_area_struct *vma, unsigned long len)
713 {
714 	void *base;
715 	int ret;
716 
717 	/* invoke the file's mapping function so that it can keep track of
718 	 * shared mappings on devices or memory
719 	 * - VM_MAYSHARE will be set if it may attempt to share
720 	 */
721 	if (vma->vm_file) {
722 		ret = vma->vm_file->f_op->mmap(vma->vm_file, vma);
723 		if (ret != -ENOSYS) {
724 			/* shouldn't return success if we're not sharing */
725 			BUG_ON(ret == 0 && !(vma->vm_flags & VM_MAYSHARE));
726 			return ret; /* success or a real error */
727 		}
728 
729 		/* getting an ENOSYS error indicates that direct mmap isn't
730 		 * possible (as opposed to tried but failed) so we'll try to
731 		 * make a private copy of the data and map that instead */
732 	}
733 
734 	/* allocate some memory to hold the mapping
735 	 * - note that this may not return a page-aligned address if the object
736 	 *   we're allocating is smaller than a page
737 	 */
738 	base = kmalloc(len, GFP_KERNEL|__GFP_COMP);
739 	if (!base)
740 		goto enomem;
741 
742 	vma->vm_start = (unsigned long) base;
743 	vma->vm_end = vma->vm_start + len;
744 	vma->vm_flags |= VM_MAPPED_COPY;
745 
746 #ifdef WARN_ON_SLACK
747 	if (len + WARN_ON_SLACK <= kobjsize(result))
748 		printk("Allocation of %lu bytes from process %d has %lu bytes of slack\n",
749 		       len, current->pid, kobjsize(result) - len);
750 #endif
751 
752 	if (vma->vm_file) {
753 		/* read the contents of a file into the copy */
754 		mm_segment_t old_fs;
755 		loff_t fpos;
756 
757 		fpos = vma->vm_pgoff;
758 		fpos <<= PAGE_SHIFT;
759 
760 		old_fs = get_fs();
761 		set_fs(KERNEL_DS);
762 		ret = vma->vm_file->f_op->read(vma->vm_file, base, len, &fpos);
763 		set_fs(old_fs);
764 
765 		if (ret < 0)
766 			goto error_free;
767 
768 		/* clear the last little bit */
769 		if (ret < len)
770 			memset(base + ret, 0, len - ret);
771 
772 	} else {
773 		/* if it's an anonymous mapping, then just clear it */
774 		memset(base, 0, len);
775 	}
776 
777 	return 0;
778 
779 error_free:
780 	kfree(base);
781 	vma->vm_start = 0;
782 	return ret;
783 
784 enomem:
785 	printk("Allocation of length %lu from process %d failed\n",
786 	       len, current->pid);
787 	show_free_areas();
788 	return -ENOMEM;
789 }
790 
791 /*
792  * handle mapping creation for uClinux
793  */
794 unsigned long do_mmap_pgoff(struct file *file,
795 			    unsigned long addr,
796 			    unsigned long len,
797 			    unsigned long prot,
798 			    unsigned long flags,
799 			    unsigned long pgoff)
800 {
801 	struct vm_list_struct *vml = NULL;
802 	struct vm_area_struct *vma = NULL;
803 	struct rb_node *rb;
804 	unsigned long capabilities, vm_flags;
805 	void *result;
806 	int ret;
807 
808 	/* decide whether we should attempt the mapping, and if so what sort of
809 	 * mapping */
810 	ret = validate_mmap_request(file, addr, len, prot, flags, pgoff,
811 				    &capabilities);
812 	if (ret < 0)
813 		return ret;
814 
815 	/* we've determined that we can make the mapping, now translate what we
816 	 * now know into VMA flags */
817 	vm_flags = determine_vm_flags(file, prot, flags, capabilities);
818 
819 	/* we're going to need to record the mapping if it works */
820 	vml = kzalloc(sizeof(struct vm_list_struct), GFP_KERNEL);
821 	if (!vml)
822 		goto error_getting_vml;
823 
824 	down_write(&nommu_vma_sem);
825 
826 	/* if we want to share, we need to check for VMAs created by other
827 	 * mmap() calls that overlap with our proposed mapping
828 	 * - we can only share with an exact match on most regular files
829 	 * - shared mappings on character devices and memory backed files are
830 	 *   permitted to overlap inexactly as far as we are concerned for in
831 	 *   these cases, sharing is handled in the driver or filesystem rather
832 	 *   than here
833 	 */
834 	if (vm_flags & VM_MAYSHARE) {
835 		unsigned long pglen = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
836 		unsigned long vmpglen;
837 
838 		/* suppress VMA sharing for shared regions */
839 		if (vm_flags & VM_SHARED &&
840 		    capabilities & BDI_CAP_MAP_DIRECT)
841 			goto dont_share_VMAs;
842 
843 		for (rb = rb_first(&nommu_vma_tree); rb; rb = rb_next(rb)) {
844 			vma = rb_entry(rb, struct vm_area_struct, vm_rb);
845 
846 			if (!(vma->vm_flags & VM_MAYSHARE))
847 				continue;
848 
849 			/* search for overlapping mappings on the same file */
850 			if (vma->vm_file->f_path.dentry->d_inode != file->f_path.dentry->d_inode)
851 				continue;
852 
853 			if (vma->vm_pgoff >= pgoff + pglen)
854 				continue;
855 
856 			vmpglen = vma->vm_end - vma->vm_start + PAGE_SIZE - 1;
857 			vmpglen >>= PAGE_SHIFT;
858 			if (pgoff >= vma->vm_pgoff + vmpglen)
859 				continue;
860 
861 			/* handle inexactly overlapping matches between mappings */
862 			if (vma->vm_pgoff != pgoff || vmpglen != pglen) {
863 				if (!(capabilities & BDI_CAP_MAP_DIRECT))
864 					goto sharing_violation;
865 				continue;
866 			}
867 
868 			/* we've found a VMA we can share */
869 			atomic_inc(&vma->vm_usage);
870 
871 			vml->vma = vma;
872 			result = (void *) vma->vm_start;
873 			goto shared;
874 		}
875 
876 	dont_share_VMAs:
877 		vma = NULL;
878 
879 		/* obtain the address at which to make a shared mapping
880 		 * - this is the hook for quasi-memory character devices to
881 		 *   tell us the location of a shared mapping
882 		 */
883 		if (file && file->f_op->get_unmapped_area) {
884 			addr = file->f_op->get_unmapped_area(file, addr, len,
885 							     pgoff, flags);
886 			if (IS_ERR((void *) addr)) {
887 				ret = addr;
888 				if (ret != (unsigned long) -ENOSYS)
889 					goto error;
890 
891 				/* the driver refused to tell us where to site
892 				 * the mapping so we'll have to attempt to copy
893 				 * it */
894 				ret = (unsigned long) -ENODEV;
895 				if (!(capabilities & BDI_CAP_MAP_COPY))
896 					goto error;
897 
898 				capabilities &= ~BDI_CAP_MAP_DIRECT;
899 			}
900 		}
901 	}
902 
903 	/* we're going to need a VMA struct as well */
904 	vma = kzalloc(sizeof(struct vm_area_struct), GFP_KERNEL);
905 	if (!vma)
906 		goto error_getting_vma;
907 
908 	INIT_LIST_HEAD(&vma->anon_vma_node);
909 	atomic_set(&vma->vm_usage, 1);
910 	if (file)
911 		get_file(file);
912 	vma->vm_file	= file;
913 	vma->vm_flags	= vm_flags;
914 	vma->vm_start	= addr;
915 	vma->vm_end	= addr + len;
916 	vma->vm_pgoff	= pgoff;
917 
918 	vml->vma = vma;
919 
920 	/* set up the mapping */
921 	if (file && vma->vm_flags & VM_SHARED)
922 		ret = do_mmap_shared_file(vma, len);
923 	else
924 		ret = do_mmap_private(vma, len);
925 	if (ret < 0)
926 		goto error;
927 
928 	/* okay... we have a mapping; now we have to register it */
929 	result = (void *) vma->vm_start;
930 
931 	if (vma->vm_flags & VM_MAPPED_COPY) {
932 		realalloc += kobjsize(result);
933 		askedalloc += len;
934 	}
935 
936 	realalloc += kobjsize(vma);
937 	askedalloc += sizeof(*vma);
938 
939 	current->mm->total_vm += len >> PAGE_SHIFT;
940 
941 	add_nommu_vma(vma);
942 
943  shared:
944 	realalloc += kobjsize(vml);
945 	askedalloc += sizeof(*vml);
946 
947 	add_vma_to_mm(current->mm, vml);
948 
949 	up_write(&nommu_vma_sem);
950 
951 	if (prot & PROT_EXEC)
952 		flush_icache_range((unsigned long) result,
953 				   (unsigned long) result + len);
954 
955 #ifdef DEBUG
956 	printk("do_mmap:\n");
957 	show_process_blocks();
958 #endif
959 
960 	return (unsigned long) result;
961 
962  error:
963 	up_write(&nommu_vma_sem);
964 	kfree(vml);
965 	if (vma) {
966 		if (vma->vm_file)
967 			fput(vma->vm_file);
968 		kfree(vma);
969 	}
970 	return ret;
971 
972  sharing_violation:
973 	up_write(&nommu_vma_sem);
974 	printk("Attempt to share mismatched mappings\n");
975 	kfree(vml);
976 	return -EINVAL;
977 
978  error_getting_vma:
979 	up_write(&nommu_vma_sem);
980 	kfree(vml);
981 	printk("Allocation of vma for %lu byte allocation from process %d failed\n",
982 	       len, current->pid);
983 	show_free_areas();
984 	return -ENOMEM;
985 
986  error_getting_vml:
987 	printk("Allocation of vml for %lu byte allocation from process %d failed\n",
988 	       len, current->pid);
989 	show_free_areas();
990 	return -ENOMEM;
991 }
992 
993 /*
994  * handle mapping disposal for uClinux
995  */
996 static void put_vma(struct vm_area_struct *vma)
997 {
998 	if (vma) {
999 		down_write(&nommu_vma_sem);
1000 
1001 		if (atomic_dec_and_test(&vma->vm_usage)) {
1002 			delete_nommu_vma(vma);
1003 
1004 			if (vma->vm_ops && vma->vm_ops->close)
1005 				vma->vm_ops->close(vma);
1006 
1007 			/* IO memory and memory shared directly out of the pagecache from
1008 			 * ramfs/tmpfs mustn't be released here */
1009 			if (vma->vm_flags & VM_MAPPED_COPY) {
1010 				realalloc -= kobjsize((void *) vma->vm_start);
1011 				askedalloc -= vma->vm_end - vma->vm_start;
1012 				kfree((void *) vma->vm_start);
1013 			}
1014 
1015 			realalloc -= kobjsize(vma);
1016 			askedalloc -= sizeof(*vma);
1017 
1018 			if (vma->vm_file)
1019 				fput(vma->vm_file);
1020 			kfree(vma);
1021 		}
1022 
1023 		up_write(&nommu_vma_sem);
1024 	}
1025 }
1026 
1027 /*
1028  * release a mapping
1029  * - under NOMMU conditions the parameters must match exactly to the mapping to
1030  *   be removed
1031  */
1032 int do_munmap(struct mm_struct *mm, unsigned long addr, size_t len)
1033 {
1034 	struct vm_list_struct *vml, **parent;
1035 	unsigned long end = addr + len;
1036 
1037 #ifdef DEBUG
1038 	printk("do_munmap:\n");
1039 #endif
1040 
1041 	for (parent = &mm->context.vmlist; *parent; parent = &(*parent)->next) {
1042 		if ((*parent)->vma->vm_start > addr)
1043 			break;
1044 		if ((*parent)->vma->vm_start == addr &&
1045 		    ((len == 0) || ((*parent)->vma->vm_end == end)))
1046 			goto found;
1047 	}
1048 
1049 	printk("munmap of non-mmaped memory by process %d (%s): %p\n",
1050 	       current->pid, current->comm, (void *) addr);
1051 	return -EINVAL;
1052 
1053  found:
1054 	vml = *parent;
1055 
1056 	put_vma(vml->vma);
1057 
1058 	*parent = vml->next;
1059 	realalloc -= kobjsize(vml);
1060 	askedalloc -= sizeof(*vml);
1061 	kfree(vml);
1062 
1063 	update_hiwater_vm(mm);
1064 	mm->total_vm -= len >> PAGE_SHIFT;
1065 
1066 #ifdef DEBUG
1067 	show_process_blocks();
1068 #endif
1069 
1070 	return 0;
1071 }
1072 
1073 asmlinkage long sys_munmap(unsigned long addr, size_t len)
1074 {
1075 	int ret;
1076 	struct mm_struct *mm = current->mm;
1077 
1078 	down_write(&mm->mmap_sem);
1079 	ret = do_munmap(mm, addr, len);
1080 	up_write(&mm->mmap_sem);
1081 	return ret;
1082 }
1083 
1084 /*
1085  * Release all mappings
1086  */
1087 void exit_mmap(struct mm_struct * mm)
1088 {
1089 	struct vm_list_struct *tmp;
1090 
1091 	if (mm) {
1092 #ifdef DEBUG
1093 		printk("Exit_mmap:\n");
1094 #endif
1095 
1096 		mm->total_vm = 0;
1097 
1098 		while ((tmp = mm->context.vmlist)) {
1099 			mm->context.vmlist = tmp->next;
1100 			put_vma(tmp->vma);
1101 
1102 			realalloc -= kobjsize(tmp);
1103 			askedalloc -= sizeof(*tmp);
1104 			kfree(tmp);
1105 		}
1106 
1107 #ifdef DEBUG
1108 		show_process_blocks();
1109 #endif
1110 	}
1111 }
1112 
1113 unsigned long do_brk(unsigned long addr, unsigned long len)
1114 {
1115 	return -ENOMEM;
1116 }
1117 
1118 /*
1119  * expand (or shrink) an existing mapping, potentially moving it at the same
1120  * time (controlled by the MREMAP_MAYMOVE flag and available VM space)
1121  *
1122  * under NOMMU conditions, we only permit changing a mapping's size, and only
1123  * as long as it stays within the hole allocated by the kmalloc() call in
1124  * do_mmap_pgoff() and the block is not shareable
1125  *
1126  * MREMAP_FIXED is not supported under NOMMU conditions
1127  */
1128 unsigned long do_mremap(unsigned long addr,
1129 			unsigned long old_len, unsigned long new_len,
1130 			unsigned long flags, unsigned long new_addr)
1131 {
1132 	struct vm_area_struct *vma;
1133 
1134 	/* insanity checks first */
1135 	if (new_len == 0)
1136 		return (unsigned long) -EINVAL;
1137 
1138 	if (flags & MREMAP_FIXED && new_addr != addr)
1139 		return (unsigned long) -EINVAL;
1140 
1141 	vma = find_vma_exact(current->mm, addr);
1142 	if (!vma)
1143 		return (unsigned long) -EINVAL;
1144 
1145 	if (vma->vm_end != vma->vm_start + old_len)
1146 		return (unsigned long) -EFAULT;
1147 
1148 	if (vma->vm_flags & VM_MAYSHARE)
1149 		return (unsigned long) -EPERM;
1150 
1151 	if (new_len > kobjsize((void *) addr))
1152 		return (unsigned long) -ENOMEM;
1153 
1154 	/* all checks complete - do it */
1155 	vma->vm_end = vma->vm_start + new_len;
1156 
1157 	askedalloc -= old_len;
1158 	askedalloc += new_len;
1159 
1160 	return vma->vm_start;
1161 }
1162 
1163 asmlinkage unsigned long sys_mremap(unsigned long addr,
1164 	unsigned long old_len, unsigned long new_len,
1165 	unsigned long flags, unsigned long new_addr)
1166 {
1167 	unsigned long ret;
1168 
1169 	down_write(&current->mm->mmap_sem);
1170 	ret = do_mremap(addr, old_len, new_len, flags, new_addr);
1171 	up_write(&current->mm->mmap_sem);
1172 	return ret;
1173 }
1174 
1175 struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
1176 			unsigned int foll_flags)
1177 {
1178 	return NULL;
1179 }
1180 
1181 int remap_pfn_range(struct vm_area_struct *vma, unsigned long from,
1182 		unsigned long to, unsigned long size, pgprot_t prot)
1183 {
1184 	vma->vm_start = vma->vm_pgoff << PAGE_SHIFT;
1185 	return 0;
1186 }
1187 EXPORT_SYMBOL(remap_pfn_range);
1188 
1189 void swap_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
1190 {
1191 }
1192 
1193 unsigned long arch_get_unmapped_area(struct file *file, unsigned long addr,
1194 	unsigned long len, unsigned long pgoff, unsigned long flags)
1195 {
1196 	return -ENOMEM;
1197 }
1198 
1199 void arch_unmap_area(struct mm_struct *mm, unsigned long addr)
1200 {
1201 }
1202 
1203 void unmap_mapping_range(struct address_space *mapping,
1204 			 loff_t const holebegin, loff_t const holelen,
1205 			 int even_cows)
1206 {
1207 }
1208 EXPORT_SYMBOL(unmap_mapping_range);
1209 
1210 /*
1211  * ask for an unmapped area at which to create a mapping on a file
1212  */
1213 unsigned long get_unmapped_area(struct file *file, unsigned long addr,
1214 				unsigned long len, unsigned long pgoff,
1215 				unsigned long flags)
1216 {
1217 	unsigned long (*get_area)(struct file *, unsigned long, unsigned long,
1218 				  unsigned long, unsigned long);
1219 
1220 	get_area = current->mm->get_unmapped_area;
1221 	if (file && file->f_op && file->f_op->get_unmapped_area)
1222 		get_area = file->f_op->get_unmapped_area;
1223 
1224 	if (!get_area)
1225 		return -ENOSYS;
1226 
1227 	return get_area(file, addr, len, pgoff, flags);
1228 }
1229 
1230 EXPORT_SYMBOL(get_unmapped_area);
1231 
1232 /*
1233  * Check that a process has enough memory to allocate a new virtual
1234  * mapping. 0 means there is enough memory for the allocation to
1235  * succeed and -ENOMEM implies there is not.
1236  *
1237  * We currently support three overcommit policies, which are set via the
1238  * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-accounting
1239  *
1240  * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
1241  * Additional code 2002 Jul 20 by Robert Love.
1242  *
1243  * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
1244  *
1245  * Note this is a helper function intended to be used by LSMs which
1246  * wish to use this logic.
1247  */
1248 int __vm_enough_memory(long pages, int cap_sys_admin)
1249 {
1250 	unsigned long free, allowed;
1251 
1252 	vm_acct_memory(pages);
1253 
1254 	/*
1255 	 * Sometimes we want to use more memory than we have
1256 	 */
1257 	if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
1258 		return 0;
1259 
1260 	if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
1261 		unsigned long n;
1262 
1263 		free = global_page_state(NR_FILE_PAGES);
1264 		free += nr_swap_pages;
1265 
1266 		/*
1267 		 * Any slabs which are created with the
1268 		 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
1269 		 * which are reclaimable, under pressure.  The dentry
1270 		 * cache and most inode caches should fall into this
1271 		 */
1272 		free += global_page_state(NR_SLAB_RECLAIMABLE);
1273 
1274 		/*
1275 		 * Leave the last 3% for root
1276 		 */
1277 		if (!cap_sys_admin)
1278 			free -= free / 32;
1279 
1280 		if (free > pages)
1281 			return 0;
1282 
1283 		/*
1284 		 * nr_free_pages() is very expensive on large systems,
1285 		 * only call if we're about to fail.
1286 		 */
1287 		n = nr_free_pages();
1288 
1289 		/*
1290 		 * Leave reserved pages. The pages are not for anonymous pages.
1291 		 */
1292 		if (n <= totalreserve_pages)
1293 			goto error;
1294 		else
1295 			n -= totalreserve_pages;
1296 
1297 		/*
1298 		 * Leave the last 3% for root
1299 		 */
1300 		if (!cap_sys_admin)
1301 			n -= n / 32;
1302 		free += n;
1303 
1304 		if (free > pages)
1305 			return 0;
1306 
1307 		goto error;
1308 	}
1309 
1310 	allowed = totalram_pages * sysctl_overcommit_ratio / 100;
1311 	/*
1312 	 * Leave the last 3% for root
1313 	 */
1314 	if (!cap_sys_admin)
1315 		allowed -= allowed / 32;
1316 	allowed += total_swap_pages;
1317 
1318 	/* Don't let a single process grow too big:
1319 	   leave 3% of the size of this process for other processes */
1320 	allowed -= current->mm->total_vm / 32;
1321 
1322 	/*
1323 	 * cast `allowed' as a signed long because vm_committed_space
1324 	 * sometimes has a negative value
1325 	 */
1326 	if (atomic_read(&vm_committed_space) < (long)allowed)
1327 		return 0;
1328 error:
1329 	vm_unacct_memory(pages);
1330 
1331 	return -ENOMEM;
1332 }
1333 
1334 int in_gate_area_no_task(unsigned long addr)
1335 {
1336 	return 0;
1337 }
1338 
1339 struct page *filemap_nopage(struct vm_area_struct *area,
1340 			unsigned long address, int *type)
1341 {
1342 	BUG();
1343 	return NULL;
1344 }
1345 
1346 /*
1347  * Access another process' address space.
1348  * - source/target buffer must be kernel space
1349  */
1350 int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
1351 {
1352 	struct vm_area_struct *vma;
1353 	struct mm_struct *mm;
1354 
1355 	if (addr + len < addr)
1356 		return 0;
1357 
1358 	mm = get_task_mm(tsk);
1359 	if (!mm)
1360 		return 0;
1361 
1362 	down_read(&mm->mmap_sem);
1363 
1364 	/* the access must start within one of the target process's mappings */
1365 	vma = find_vma(mm, addr);
1366 	if (vma) {
1367 		/* don't overrun this mapping */
1368 		if (addr + len >= vma->vm_end)
1369 			len = vma->vm_end - addr;
1370 
1371 		/* only read or write mappings where it is permitted */
1372 		if (write && vma->vm_flags & VM_MAYWRITE)
1373 			len -= copy_to_user((void *) addr, buf, len);
1374 		else if (!write && vma->vm_flags & VM_MAYREAD)
1375 			len -= copy_from_user(buf, (void *) addr, len);
1376 		else
1377 			len = 0;
1378 	} else {
1379 		len = 0;
1380 	}
1381 
1382 	up_read(&mm->mmap_sem);
1383 	mmput(mm);
1384 	return len;
1385 }
1386