nommu.c revision 7a9166e3b037296366cea6f3c97f705d33e209e6 
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
35void *high_memory;
36struct page *mem_map;
37unsigned long max_mapnr;
38unsigned long num_physpages;
39unsigned long askedalloc, realalloc;
40atomic_t vm_committed_space = ATOMIC_INIT(0);
41int sysctl_overcommit_memory = OVERCOMMIT_GUESS; /* heuristic overcommit */
42int sysctl_overcommit_ratio = 50; /* default is 50% */
43int sysctl_max_map_count = DEFAULT_MAX_MAP_COUNT;
44int heap_stack_gap = 0;
45
46EXPORT_SYMBOL(mem_map);
47EXPORT_SYMBOL(__vm_enough_memory);
48
49/* list of shareable VMAs */
50struct rb_root nommu_vma_tree = RB_ROOT;
51DECLARE_RWSEM(nommu_vma_sem);
52
53struct vm_operations_struct generic_file_vm_ops = {
54};
55
56EXPORT_SYMBOL(vmalloc);
57EXPORT_SYMBOL(vfree);
58EXPORT_SYMBOL(vmalloc_to_page);
59EXPORT_SYMBOL(vmalloc_32);
60EXPORT_SYMBOL(vmap);
61EXPORT_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 */
71int 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
83do_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
91out_truncate:
92	if (inode->i_op && inode->i_op->truncate)
93		inode->i_op->truncate(inode);
94	return 0;
95out_sig:
96	send_sig(SIGXFSZ, current, 0);
97out:
98	return -EFBIG;
99}
100
101EXPORT_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 */
109unsigned 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 * The nommu dodgy version :-)
127 */
128int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
129	unsigned long start, int len, int write, int force,
130	struct page **pages, struct vm_area_struct **vmas)
131{
132	int i;
133	static struct vm_area_struct dummy_vma;
134
135	for (i = 0; i < len; i++) {
136		if (pages) {
137			pages[i] = virt_to_page(start);
138			if (pages[i])
139				page_cache_get(pages[i]);
140		}
141		if (vmas)
142			vmas[i] = &dummy_vma;
143		start += PAGE_SIZE;
144	}
145	return(i);
146}
147
148EXPORT_SYMBOL(get_user_pages);
149
150DEFINE_RWLOCK(vmlist_lock);
151struct vm_struct *vmlist;
152
153void vfree(void *addr)
154{
155	kfree(addr);
156}
157
158void *__vmalloc(unsigned long size, gfp_t gfp_mask, pgprot_t prot)
159{
160	/*
161	 * kmalloc doesn't like __GFP_HIGHMEM for some reason
162	 */
163	return kmalloc(size, gfp_mask & ~__GFP_HIGHMEM);
164}
165
166struct page * vmalloc_to_page(void *addr)
167{
168	return virt_to_page(addr);
169}
170
171unsigned long vmalloc_to_pfn(void *addr)
172{
173	return page_to_pfn(virt_to_page(addr));
174}
175
176
177long vread(char *buf, char *addr, unsigned long count)
178{
179	memcpy(buf, addr, count);
180	return count;
181}
182
183long vwrite(char *buf, char *addr, unsigned long count)
184{
185	/* Don't allow overflow */
186	if ((unsigned long) addr + count < count)
187		count = -(unsigned long) addr;
188
189	memcpy(addr, buf, count);
190	return(count);
191}
192
193/*
194 *	vmalloc  -  allocate virtually continguos memory
195 *
196 *	@size:		allocation size
197 *
198 *	Allocate enough pages to cover @size from the page level
199 *	allocator and map them into continguos kernel virtual space.
200 *
201 *	For tight cotrol over page level allocator and protection flags
202 *	use __vmalloc() instead.
203 */
204void *vmalloc(unsigned long size)
205{
206       return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL);
207}
208
209/*
210 *	vmalloc_32  -  allocate virtually continguos memory (32bit addressable)
211 *
212 *	@size:		allocation size
213 *
214 *	Allocate enough 32bit PA addressable pages to cover @size from the
215 *	page level allocator and map them into continguos kernel virtual space.
216 */
217void *vmalloc_32(unsigned long size)
218{
219	return __vmalloc(size, GFP_KERNEL, PAGE_KERNEL);
220}
221
222void *vmap(struct page **pages, unsigned int count, unsigned long flags, pgprot_t prot)
223{
224	BUG();
225	return NULL;
226}
227
228void vunmap(void *addr)
229{
230	BUG();
231}
232
233/*
234 *  sys_brk() for the most part doesn't need the global kernel
235 *  lock, except when an application is doing something nasty
236 *  like trying to un-brk an area that has already been mapped
237 *  to a regular file.  in this case, the unmapping will need
238 *  to invoke file system routines that need the global lock.
239 */
240asmlinkage unsigned long sys_brk(unsigned long brk)
241{
242	struct mm_struct *mm = current->mm;
243
244	if (brk < mm->start_brk || brk > mm->context.end_brk)
245		return mm->brk;
246
247	if (mm->brk == brk)
248		return mm->brk;
249
250	/*
251	 * Always allow shrinking brk
252	 */
253	if (brk <= mm->brk) {
254		mm->brk = brk;
255		return brk;
256	}
257
258	/*
259	 * Ok, looks good - let it rip.
260	 */
261	return mm->brk = brk;
262}
263
264#ifdef DEBUG
265static void show_process_blocks(void)
266{
267	struct vm_list_struct *vml;
268
269	printk("Process blocks %d:", current->pid);
270
271	for (vml = &current->mm->context.vmlist; vml; vml = vml->next) {
272		printk(" %p: %p", vml, vml->vma);
273		if (vml->vma)
274			printk(" (%d @%lx #%d)",
275			       kobjsize((void *) vml->vma->vm_start),
276			       vml->vma->vm_start,
277			       atomic_read(&vml->vma->vm_usage));
278		printk(vml->next ? " ->" : ".\n");
279	}
280}
281#endif /* DEBUG */
282
283static inline struct vm_area_struct *find_nommu_vma(unsigned long start)
284{
285	struct vm_area_struct *vma;
286	struct rb_node *n = nommu_vma_tree.rb_node;
287
288	while (n) {
289		vma = rb_entry(n, struct vm_area_struct, vm_rb);
290
291		if (start < vma->vm_start)
292			n = n->rb_left;
293		else if (start > vma->vm_start)
294			n = n->rb_right;
295		else
296			return vma;
297	}
298
299	return NULL;
300}
301
302static void add_nommu_vma(struct vm_area_struct *vma)
303{
304	struct vm_area_struct *pvma;
305	struct address_space *mapping;
306	struct rb_node **p = &nommu_vma_tree.rb_node;
307	struct rb_node *parent = NULL;
308
309	/* add the VMA to the mapping */
310	if (vma->vm_file) {
311		mapping = vma->vm_file->f_mapping;
312
313		flush_dcache_mmap_lock(mapping);
314		vma_prio_tree_insert(vma, &mapping->i_mmap);
315		flush_dcache_mmap_unlock(mapping);
316	}
317
318	/* add the VMA to the master list */
319	while (*p) {
320		parent = *p;
321		pvma = rb_entry(parent, struct vm_area_struct, vm_rb);
322
323		if (vma->vm_start < pvma->vm_start) {
324			p = &(*p)->rb_left;
325		}
326		else if (vma->vm_start > pvma->vm_start) {
327			p = &(*p)->rb_right;
328		}
329		else {
330			/* mappings are at the same address - this can only
331			 * happen for shared-mem chardevs and shared file
332			 * mappings backed by ramfs/tmpfs */
333			BUG_ON(!(pvma->vm_flags & VM_SHARED));
334
335			if (vma < pvma)
336				p = &(*p)->rb_left;
337			else if (vma > pvma)
338				p = &(*p)->rb_right;
339			else
340				BUG();
341		}
342	}
343
344	rb_link_node(&vma->vm_rb, parent, p);
345	rb_insert_color(&vma->vm_rb, &nommu_vma_tree);
346}
347
348static void delete_nommu_vma(struct vm_area_struct *vma)
349{
350	struct address_space *mapping;
351
352	/* remove the VMA from the mapping */
353	if (vma->vm_file) {
354		mapping = vma->vm_file->f_mapping;
355
356		flush_dcache_mmap_lock(mapping);
357		vma_prio_tree_remove(vma, &mapping->i_mmap);
358		flush_dcache_mmap_unlock(mapping);
359	}
360
361	/* remove from the master list */
362	rb_erase(&vma->vm_rb, &nommu_vma_tree);
363}
364
365/*
366 * determine whether a mapping should be permitted and, if so, what sort of
367 * mapping we're capable of supporting
368 */
369static int validate_mmap_request(struct file *file,
370				 unsigned long addr,
371				 unsigned long len,
372				 unsigned long prot,
373				 unsigned long flags,
374				 unsigned long pgoff,
375				 unsigned long *_capabilities)
376{
377	unsigned long capabilities;
378	unsigned long reqprot = prot;
379	int ret;
380
381	/* do the simple checks first */
382	if (flags & MAP_FIXED || addr) {
383		printk(KERN_DEBUG
384		       "%d: Can't do fixed-address/overlay mmap of RAM\n",
385		       current->pid);
386		return -EINVAL;
387	}
388
389	if ((flags & MAP_TYPE) != MAP_PRIVATE &&
390	    (flags & MAP_TYPE) != MAP_SHARED)
391		return -EINVAL;
392
393	if (PAGE_ALIGN(len) == 0)
394		return addr;
395
396	if (len > TASK_SIZE)
397		return -EINVAL;
398
399	/* offset overflow? */
400	if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
401		return -EINVAL;
402
403	if (file) {
404		/* validate file mapping requests */
405		struct address_space *mapping;
406
407		/* files must support mmap */
408		if (!file->f_op || !file->f_op->mmap)
409			return -ENODEV;
410
411		/* work out if what we've got could possibly be shared
412		 * - we support chardevs that provide their own "memory"
413		 * - we support files/blockdevs that are memory backed
414		 */
415		mapping = file->f_mapping;
416		if (!mapping)
417			mapping = file->f_dentry->d_inode->i_mapping;
418
419		capabilities = 0;
420		if (mapping && mapping->backing_dev_info)
421			capabilities = mapping->backing_dev_info->capabilities;
422
423		if (!capabilities) {
424			/* no explicit capabilities set, so assume some
425			 * defaults */
426			switch (file->f_dentry->d_inode->i_mode & S_IFMT) {
427			case S_IFREG:
428			case S_IFBLK:
429				capabilities = BDI_CAP_MAP_COPY;
430				break;
431
432			case S_IFCHR:
433				capabilities =
434					BDI_CAP_MAP_DIRECT |
435					BDI_CAP_READ_MAP |
436					BDI_CAP_WRITE_MAP;
437				break;
438
439			default:
440				return -EINVAL;
441			}
442		}
443
444		/* eliminate any capabilities that we can't support on this
445		 * device */
446		if (!file->f_op->get_unmapped_area)
447			capabilities &= ~BDI_CAP_MAP_DIRECT;
448		if (!file->f_op->read)
449			capabilities &= ~BDI_CAP_MAP_COPY;
450
451		if (flags & MAP_SHARED) {
452			/* do checks for writing, appending and locking */
453			if ((prot & PROT_WRITE) &&
454			    !(file->f_mode & FMODE_WRITE))
455				return -EACCES;
456
457			if (IS_APPEND(file->f_dentry->d_inode) &&
458			    (file->f_mode & FMODE_WRITE))
459				return -EACCES;
460
461			if (locks_verify_locked(file->f_dentry->d_inode))
462				return -EAGAIN;
463
464			if (!(capabilities & BDI_CAP_MAP_DIRECT))
465				return -ENODEV;
466
467			if (((prot & PROT_READ)  && !(capabilities & BDI_CAP_READ_MAP))  ||
468			    ((prot & PROT_WRITE) && !(capabilities & BDI_CAP_WRITE_MAP)) ||
469			    ((prot & PROT_EXEC)  && !(capabilities & BDI_CAP_EXEC_MAP))
470			    ) {
471				printk("MAP_SHARED not completely supported on !MMU\n");
472				return -EINVAL;
473			}
474
475			/* we mustn't privatise shared mappings */
476			capabilities &= ~BDI_CAP_MAP_COPY;
477		}
478		else {
479			/* we're going to read the file into private memory we
480			 * allocate */
481			if (!(capabilities & BDI_CAP_MAP_COPY))
482				return -ENODEV;
483
484			/* we don't permit a private writable mapping to be
485			 * shared with the backing device */
486			if (prot & PROT_WRITE)
487				capabilities &= ~BDI_CAP_MAP_DIRECT;
488		}
489
490		/* handle executable mappings and implied executable
491		 * mappings */
492		if (file->f_vfsmnt->mnt_flags & MNT_NOEXEC) {
493			if (prot & PROT_EXEC)
494				return -EPERM;
495		}
496		else if ((prot & PROT_READ) && !(prot & PROT_EXEC)) {
497			/* handle implication of PROT_EXEC by PROT_READ */
498			if (current->personality & READ_IMPLIES_EXEC) {
499				if (capabilities & BDI_CAP_EXEC_MAP)
500					prot |= PROT_EXEC;
501			}
502		}
503		else if ((prot & PROT_READ) &&
504			 (prot & PROT_EXEC) &&
505			 !(capabilities & BDI_CAP_EXEC_MAP)
506			 ) {
507			/* backing file is not executable, try to copy */
508			capabilities &= ~BDI_CAP_MAP_DIRECT;
509		}
510	}
511	else {
512		/* anonymous mappings are always memory backed and can be
513		 * privately mapped
514		 */
515		capabilities = BDI_CAP_MAP_COPY;
516
517		/* handle PROT_EXEC implication by PROT_READ */
518		if ((prot & PROT_READ) &&
519		    (current->personality & READ_IMPLIES_EXEC))
520			prot |= PROT_EXEC;
521	}
522
523	/* allow the security API to have its say */
524	ret = security_file_mmap(file, reqprot, prot, flags);
525	if (ret < 0)
526		return ret;
527
528	/* looks okay */
529	*_capabilities = capabilities;
530	return 0;
531}
532
533/*
534 * we've determined that we can make the mapping, now translate what we
535 * now know into VMA flags
536 */
537static unsigned long determine_vm_flags(struct file *file,
538					unsigned long prot,
539					unsigned long flags,
540					unsigned long capabilities)
541{
542	unsigned long vm_flags;
543
544	vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags);
545	vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
546	/* vm_flags |= mm->def_flags; */
547
548	if (!(capabilities & BDI_CAP_MAP_DIRECT)) {
549		/* attempt to share read-only copies of mapped file chunks */
550		if (file && !(prot & PROT_WRITE))
551			vm_flags |= VM_MAYSHARE;
552	}
553	else {
554		/* overlay a shareable mapping on the backing device or inode
555		 * if possible - used for chardevs, ramfs/tmpfs/shmfs and
556		 * romfs/cramfs */
557		if (flags & MAP_SHARED)
558			vm_flags |= VM_MAYSHARE | VM_SHARED;
559		else if ((((vm_flags & capabilities) ^ vm_flags) & BDI_CAP_VMFLAGS) == 0)
560			vm_flags |= VM_MAYSHARE;
561	}
562
563	/* refuse to let anyone share private mappings with this process if
564	 * it's being traced - otherwise breakpoints set in it may interfere
565	 * with another untraced process
566	 */
567	if ((flags & MAP_PRIVATE) && (current->ptrace & PT_PTRACED))
568		vm_flags &= ~VM_MAYSHARE;
569
570	return vm_flags;
571}
572
573/*
574 * set up a shared mapping on a file
575 */
576static int do_mmap_shared_file(struct vm_area_struct *vma, unsigned long len)
577{
578	int ret;
579
580	ret = vma->vm_file->f_op->mmap(vma->vm_file, vma);
581	if (ret != -ENOSYS)
582		return ret;
583
584	/* getting an ENOSYS error indicates that direct mmap isn't
585	 * possible (as opposed to tried but failed) so we'll fall
586	 * through to making a private copy of the data and mapping
587	 * that if we can */
588	return -ENODEV;
589}
590
591/*
592 * set up a private mapping or an anonymous shared mapping
593 */
594static int do_mmap_private(struct vm_area_struct *vma, unsigned long len)
595{
596	void *base;
597	int ret;
598
599	/* invoke the file's mapping function so that it can keep track of
600	 * shared mappings on devices or memory
601	 * - VM_MAYSHARE will be set if it may attempt to share
602	 */
603	if (vma->vm_file) {
604		ret = vma->vm_file->f_op->mmap(vma->vm_file, vma);
605		if (ret != -ENOSYS) {
606			/* shouldn't return success if we're not sharing */
607			BUG_ON(ret == 0 && !(vma->vm_flags & VM_MAYSHARE));
608			return ret; /* success or a real error */
609		}
610
611		/* getting an ENOSYS error indicates that direct mmap isn't
612		 * possible (as opposed to tried but failed) so we'll try to
613		 * make a private copy of the data and map that instead */
614	}
615
616	/* allocate some memory to hold the mapping
617	 * - note that this may not return a page-aligned address if the object
618	 *   we're allocating is smaller than a page
619	 */
620	base = kmalloc(len, GFP_KERNEL);
621	if (!base)
622		goto enomem;
623
624	vma->vm_start = (unsigned long) base;
625	vma->vm_end = vma->vm_start + len;
626	vma->vm_flags |= VM_MAPPED_COPY;
627
628#ifdef WARN_ON_SLACK
629	if (len + WARN_ON_SLACK <= kobjsize(result))
630		printk("Allocation of %lu bytes from process %d has %lu bytes of slack\n",
631		       len, current->pid, kobjsize(result) - len);
632#endif
633
634	if (vma->vm_file) {
635		/* read the contents of a file into the copy */
636		mm_segment_t old_fs;
637		loff_t fpos;
638
639		fpos = vma->vm_pgoff;
640		fpos <<= PAGE_SHIFT;
641
642		old_fs = get_fs();
643		set_fs(KERNEL_DS);
644		ret = vma->vm_file->f_op->read(vma->vm_file, base, len, &fpos);
645		set_fs(old_fs);
646
647		if (ret < 0)
648			goto error_free;
649
650		/* clear the last little bit */
651		if (ret < len)
652			memset(base + ret, 0, len - ret);
653
654	} else {
655		/* if it's an anonymous mapping, then just clear it */
656		memset(base, 0, len);
657	}
658
659	return 0;
660
661error_free:
662	kfree(base);
663	vma->vm_start = 0;
664	return ret;
665
666enomem:
667	printk("Allocation of length %lu from process %d failed\n",
668	       len, current->pid);
669	show_free_areas();
670	return -ENOMEM;
671}
672
673/*
674 * handle mapping creation for uClinux
675 */
676unsigned long do_mmap_pgoff(struct file *file,
677			    unsigned long addr,
678			    unsigned long len,
679			    unsigned long prot,
680			    unsigned long flags,
681			    unsigned long pgoff)
682{
683	struct vm_list_struct *vml = NULL;
684	struct vm_area_struct *vma = NULL;
685	struct rb_node *rb;
686	unsigned long capabilities, vm_flags;
687	void *result;
688	int ret;
689
690	/* decide whether we should attempt the mapping, and if so what sort of
691	 * mapping */
692	ret = validate_mmap_request(file, addr, len, prot, flags, pgoff,
693				    &capabilities);
694	if (ret < 0)
695		return ret;
696
697	/* we've determined that we can make the mapping, now translate what we
698	 * now know into VMA flags */
699	vm_flags = determine_vm_flags(file, prot, flags, capabilities);
700
701	/* we're going to need to record the mapping if it works */
702	vml = kmalloc(sizeof(struct vm_list_struct), GFP_KERNEL);
703	if (!vml)
704		goto error_getting_vml;
705	memset(vml, 0, sizeof(*vml));
706
707	down_write(&nommu_vma_sem);
708
709	/* if we want to share, we need to check for VMAs created by other
710	 * mmap() calls that overlap with our proposed mapping
711	 * - we can only share with an exact match on most regular files
712	 * - shared mappings on character devices and memory backed files are
713	 *   permitted to overlap inexactly as far as we are concerned for in
714	 *   these cases, sharing is handled in the driver or filesystem rather
715	 *   than here
716	 */
717	if (vm_flags & VM_MAYSHARE) {
718		unsigned long pglen = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
719		unsigned long vmpglen;
720
721		for (rb = rb_first(&nommu_vma_tree); rb; rb = rb_next(rb)) {
722			vma = rb_entry(rb, struct vm_area_struct, vm_rb);
723
724			if (!(vma->vm_flags & VM_MAYSHARE))
725				continue;
726
727			/* search for overlapping mappings on the same file */
728			if (vma->vm_file->f_dentry->d_inode != file->f_dentry->d_inode)
729				continue;
730
731			if (vma->vm_pgoff >= pgoff + pglen)
732				continue;
733
734			vmpglen = vma->vm_end - vma->vm_start + PAGE_SIZE - 1;
735			vmpglen >>= PAGE_SHIFT;
736			if (pgoff >= vma->vm_pgoff + vmpglen)
737				continue;
738
739			/* handle inexactly overlapping matches between mappings */
740			if (vma->vm_pgoff != pgoff || vmpglen != pglen) {
741				if (!(capabilities & BDI_CAP_MAP_DIRECT))
742					goto sharing_violation;
743				continue;
744			}
745
746			/* we've found a VMA we can share */
747			atomic_inc(&vma->vm_usage);
748
749			vml->vma = vma;
750			result = (void *) vma->vm_start;
751			goto shared;
752		}
753
754		vma = NULL;
755
756		/* obtain the address at which to make a shared mapping
757		 * - this is the hook for quasi-memory character devices to
758		 *   tell us the location of a shared mapping
759		 */
760		if (file && file->f_op->get_unmapped_area) {
761			addr = file->f_op->get_unmapped_area(file, addr, len,
762							     pgoff, flags);
763			if (IS_ERR((void *) addr)) {
764				ret = addr;
765				if (ret != (unsigned long) -ENOSYS)
766					goto error;
767
768				/* the driver refused to tell us where to site
769				 * the mapping so we'll have to attempt to copy
770				 * it */
771				ret = (unsigned long) -ENODEV;
772				if (!(capabilities & BDI_CAP_MAP_COPY))
773					goto error;
774
775				capabilities &= ~BDI_CAP_MAP_DIRECT;
776			}
777		}
778	}
779
780	/* we're going to need a VMA struct as well */
781	vma = kmalloc(sizeof(struct vm_area_struct), GFP_KERNEL);
782	if (!vma)
783		goto error_getting_vma;
784
785	memset(vma, 0, sizeof(*vma));
786	INIT_LIST_HEAD(&vma->anon_vma_node);
787	atomic_set(&vma->vm_usage, 1);
788	if (file)
789		get_file(file);
790	vma->vm_file	= file;
791	vma->vm_flags	= vm_flags;
792	vma->vm_start	= addr;
793	vma->vm_end	= addr + len;
794	vma->vm_pgoff	= pgoff;
795
796	vml->vma = vma;
797
798	/* set up the mapping */
799	if (file && vma->vm_flags & VM_SHARED)
800		ret = do_mmap_shared_file(vma, len);
801	else
802		ret = do_mmap_private(vma, len);
803	if (ret < 0)
804		goto error;
805
806	/* okay... we have a mapping; now we have to register it */
807	result = (void *) vma->vm_start;
808
809	if (vma->vm_flags & VM_MAPPED_COPY) {
810		realalloc += kobjsize(result);
811		askedalloc += len;
812	}
813
814	realalloc += kobjsize(vma);
815	askedalloc += sizeof(*vma);
816
817	current->mm->total_vm += len >> PAGE_SHIFT;
818
819	add_nommu_vma(vma);
820
821 shared:
822	realalloc += kobjsize(vml);
823	askedalloc += sizeof(*vml);
824
825	vml->next = current->mm->context.vmlist;
826	current->mm->context.vmlist = vml;
827
828	up_write(&nommu_vma_sem);
829
830	if (prot & PROT_EXEC)
831		flush_icache_range((unsigned long) result,
832				   (unsigned long) result + len);
833
834#ifdef DEBUG
835	printk("do_mmap:\n");
836	show_process_blocks();
837#endif
838
839	return (unsigned long) result;
840
841 error:
842	up_write(&nommu_vma_sem);
843	kfree(vml);
844	if (vma) {
845		fput(vma->vm_file);
846		kfree(vma);
847	}
848	return ret;
849
850 sharing_violation:
851	up_write(&nommu_vma_sem);
852	printk("Attempt to share mismatched mappings\n");
853	kfree(vml);
854	return -EINVAL;
855
856 error_getting_vma:
857	up_write(&nommu_vma_sem);
858	kfree(vml);
859	printk("Allocation of vma for %lu byte allocation from process %d failed\n",
860	       len, current->pid);
861	show_free_areas();
862	return -ENOMEM;
863
864 error_getting_vml:
865	printk("Allocation of vml for %lu byte allocation from process %d failed\n",
866	       len, current->pid);
867	show_free_areas();
868	return -ENOMEM;
869}
870
871/*
872 * handle mapping disposal for uClinux
873 */
874static void put_vma(struct vm_area_struct *vma)
875{
876	if (vma) {
877		down_write(&nommu_vma_sem);
878
879		if (atomic_dec_and_test(&vma->vm_usage)) {
880			delete_nommu_vma(vma);
881
882			if (vma->vm_ops && vma->vm_ops->close)
883				vma->vm_ops->close(vma);
884
885			/* IO memory and memory shared directly out of the pagecache from
886			 * ramfs/tmpfs mustn't be released here */
887			if (vma->vm_flags & VM_MAPPED_COPY) {
888				realalloc -= kobjsize((void *) vma->vm_start);
889				askedalloc -= vma->vm_end - vma->vm_start;
890				kfree((void *) vma->vm_start);
891			}
892
893			realalloc -= kobjsize(vma);
894			askedalloc -= sizeof(*vma);
895
896			if (vma->vm_file)
897				fput(vma->vm_file);
898			kfree(vma);
899		}
900
901		up_write(&nommu_vma_sem);
902	}
903}
904
905int do_munmap(struct mm_struct *mm, unsigned long addr, size_t len)
906{
907	struct vm_list_struct *vml, **parent;
908	unsigned long end = addr + len;
909
910#ifdef DEBUG
911	printk("do_munmap:\n");
912#endif
913
914	for (parent = &mm->context.vmlist; *parent; parent = &(*parent)->next)
915		if ((*parent)->vma->vm_start == addr &&
916		    ((len == 0) || ((*parent)->vma->vm_end == end)))
917			goto found;
918
919	printk("munmap of non-mmaped memory by process %d (%s): %p\n",
920	       current->pid, current->comm, (void *) addr);
921	return -EINVAL;
922
923 found:
924	vml = *parent;
925
926	put_vma(vml->vma);
927
928	*parent = vml->next;
929	realalloc -= kobjsize(vml);
930	askedalloc -= sizeof(*vml);
931	kfree(vml);
932
933	update_hiwater_vm(mm);
934	mm->total_vm -= len >> PAGE_SHIFT;
935
936#ifdef DEBUG
937	show_process_blocks();
938#endif
939
940	return 0;
941}
942
943/* Release all mmaps. */
944void exit_mmap(struct mm_struct * mm)
945{
946	struct vm_list_struct *tmp;
947
948	if (mm) {
949#ifdef DEBUG
950		printk("Exit_mmap:\n");
951#endif
952
953		mm->total_vm = 0;
954
955		while ((tmp = mm->context.vmlist)) {
956			mm->context.vmlist = tmp->next;
957			put_vma(tmp->vma);
958
959			realalloc -= kobjsize(tmp);
960			askedalloc -= sizeof(*tmp);
961			kfree(tmp);
962		}
963
964#ifdef DEBUG
965		show_process_blocks();
966#endif
967	}
968}
969
970asmlinkage long sys_munmap(unsigned long addr, size_t len)
971{
972	int ret;
973	struct mm_struct *mm = current->mm;
974
975	down_write(&mm->mmap_sem);
976	ret = do_munmap(mm, addr, len);
977	up_write(&mm->mmap_sem);
978	return ret;
979}
980
981unsigned long do_brk(unsigned long addr, unsigned long len)
982{
983	return -ENOMEM;
984}
985
986/*
987 * Expand (or shrink) an existing mapping, potentially moving it at the
988 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
989 *
990 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
991 * This option implies MREMAP_MAYMOVE.
992 *
993 * on uClinux, we only permit changing a mapping's size, and only as long as it stays within the
994 * hole allocated by the kmalloc() call in do_mmap_pgoff() and the block is not shareable
995 */
996unsigned long do_mremap(unsigned long addr,
997			unsigned long old_len, unsigned long new_len,
998			unsigned long flags, unsigned long new_addr)
999{
1000	struct vm_list_struct *vml = NULL;
1001
1002	/* insanity checks first */
1003	if (new_len == 0)
1004		return (unsigned long) -EINVAL;
1005
1006	if (flags & MREMAP_FIXED && new_addr != addr)
1007		return (unsigned long) -EINVAL;
1008
1009	for (vml = current->mm->context.vmlist; vml; vml = vml->next)
1010		if (vml->vma->vm_start == addr)
1011			goto found;
1012
1013	return (unsigned long) -EINVAL;
1014
1015 found:
1016	if (vml->vma->vm_end != vml->vma->vm_start + old_len)
1017		return (unsigned long) -EFAULT;
1018
1019	if (vml->vma->vm_flags & VM_MAYSHARE)
1020		return (unsigned long) -EPERM;
1021
1022	if (new_len > kobjsize((void *) addr))
1023		return (unsigned long) -ENOMEM;
1024
1025	/* all checks complete - do it */
1026	vml->vma->vm_end = vml->vma->vm_start + new_len;
1027
1028	askedalloc -= old_len;
1029	askedalloc += new_len;
1030
1031	return vml->vma->vm_start;
1032}
1033
1034/*
1035 * Look up the first VMA which satisfies  addr < vm_end,  NULL if none
1036 */
1037struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
1038{
1039	struct vm_list_struct *vml;
1040
1041	for (vml = mm->context.vmlist; vml; vml = vml->next)
1042		if (addr >= vml->vma->vm_start && addr < vml->vma->vm_end)
1043			return vml->vma;
1044
1045	return NULL;
1046}
1047
1048EXPORT_SYMBOL(find_vma);
1049
1050struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
1051			unsigned int foll_flags)
1052{
1053	return NULL;
1054}
1055
1056struct vm_area_struct *find_extend_vma(struct mm_struct *mm, unsigned long addr)
1057{
1058	return NULL;
1059}
1060
1061int remap_pfn_range(struct vm_area_struct *vma, unsigned long from,
1062		unsigned long to, unsigned long size, pgprot_t prot)
1063{
1064	vma->vm_start = vma->vm_pgoff << PAGE_SHIFT;
1065	return 0;
1066}
1067
1068void swap_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
1069{
1070}
1071
1072unsigned long arch_get_unmapped_area(struct file *file, unsigned long addr,
1073	unsigned long len, unsigned long pgoff, unsigned long flags)
1074{
1075	return -ENOMEM;
1076}
1077
1078void arch_unmap_area(struct mm_struct *mm, unsigned long addr)
1079{
1080}
1081
1082void unmap_mapping_range(struct address_space *mapping,
1083			 loff_t const holebegin, loff_t const holelen,
1084			 int even_cows)
1085{
1086}
1087
1088/*
1089 * Check that a process has enough memory to allocate a new virtual
1090 * mapping. 0 means there is enough memory for the allocation to
1091 * succeed and -ENOMEM implies there is not.
1092 *
1093 * We currently support three overcommit policies, which are set via the
1094 * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-accounting
1095 *
1096 * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
1097 * Additional code 2002 Jul 20 by Robert Love.
1098 *
1099 * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
1100 *
1101 * Note this is a helper function intended to be used by LSMs which
1102 * wish to use this logic.
1103 */
1104int __vm_enough_memory(long pages, int cap_sys_admin)
1105{
1106	unsigned long free, allowed;
1107
1108	vm_acct_memory(pages);
1109
1110	/*
1111	 * Sometimes we want to use more memory than we have
1112	 */
1113	if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
1114		return 0;
1115
1116	if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
1117		unsigned long n;
1118
1119		free = get_page_cache_size();
1120		free += nr_swap_pages;
1121
1122		/*
1123		 * Any slabs which are created with the
1124		 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
1125		 * which are reclaimable, under pressure.  The dentry
1126		 * cache and most inode caches should fall into this
1127		 */
1128		free += atomic_read(&slab_reclaim_pages);
1129
1130		/*
1131		 * Leave the last 3% for root
1132		 */
1133		if (!cap_sys_admin)
1134			free -= free / 32;
1135
1136		if (free > pages)
1137			return 0;
1138
1139		/*
1140		 * nr_free_pages() is very expensive on large systems,
1141		 * only call if we're about to fail.
1142		 */
1143		n = nr_free_pages();
1144		if (!cap_sys_admin)
1145			n -= n / 32;
1146		free += n;
1147
1148		if (free > pages)
1149			return 0;
1150		vm_unacct_memory(pages);
1151		return -ENOMEM;
1152	}
1153
1154	allowed = totalram_pages * sysctl_overcommit_ratio / 100;
1155	/*
1156	 * Leave the last 3% for root
1157	 */
1158	if (!cap_sys_admin)
1159		allowed -= allowed / 32;
1160	allowed += total_swap_pages;
1161
1162	/* Don't let a single process grow too big:
1163	   leave 3% of the size of this process for other processes */
1164	allowed -= current->mm->total_vm / 32;
1165
1166	/*
1167	 * cast `allowed' as a signed long because vm_committed_space
1168	 * sometimes has a negative value
1169	 */
1170	if (atomic_read(&vm_committed_space) < (long)allowed)
1171		return 0;
1172
1173	vm_unacct_memory(pages);
1174
1175	return -ENOMEM;
1176}
1177
1178int in_gate_area_no_task(unsigned long addr)
1179{
1180	return 0;
1181}
1182
1183struct page *filemap_nopage(struct vm_area_struct *area,
1184			unsigned long address, int *type)
1185{
1186	BUG();
1187	return NULL;
1188}
1189