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CommitLineData
1da177e4
LT
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>
f905bc44 13 * Copyright (c) 2007 Paul Mundt <lethal@linux-sh.org>
1da177e4
LT
14 */
15
f2b8544f 16#include <linux/module.h>
1da177e4
LT
17#include <linux/mm.h>
18#include <linux/mman.h>
19#include <linux/swap.h>
20#include <linux/file.h>
21#include <linux/highmem.h>
22#include <linux/pagemap.h>
23#include <linux/slab.h>
24#include <linux/vmalloc.h>
25#include <linux/ptrace.h>
26#include <linux/blkdev.h>
27#include <linux/backing-dev.h>
28#include <linux/mount.h>
29#include <linux/personality.h>
30#include <linux/security.h>
31#include <linux/syscalls.h>
32
33#include <asm/uaccess.h>
34#include <asm/tlb.h>
35#include <asm/tlbflush.h>
36
37void *high_memory;
38struct page *mem_map;
39unsigned long max_mapnr;
40unsigned long num_physpages;
41unsigned long askedalloc, realalloc;
42atomic_t vm_committed_space = ATOMIC_INIT(0);
43int sysctl_overcommit_memory = OVERCOMMIT_GUESS; /* heuristic overcommit */
44int sysctl_overcommit_ratio = 50; /* default is 50% */
45int sysctl_max_map_count = DEFAULT_MAX_MAP_COUNT;
46int heap_stack_gap = 0;
47
48EXPORT_SYMBOL(mem_map);
6a04de6d 49EXPORT_SYMBOL(num_physpages);
1da177e4
LT
50
51/* list of shareable VMAs */
52struct rb_root nommu_vma_tree = RB_ROOT;
53DECLARE_RWSEM(nommu_vma_sem);
54
55struct vm_operations_struct generic_file_vm_ops = {
56};
57
58/*
59 * Handle all mappings that got truncated by a "truncate()"
60 * system call.
61 *
62 * NOTE! We have to be ready to update the memory sharing
63 * between the file and the memory map for a potential last
64 * incomplete page. Ugly, but necessary.
65 */
66int vmtruncate(struct inode *inode, loff_t offset)
67{
68 struct address_space *mapping = inode->i_mapping;
69 unsigned long limit;
70
71 if (inode->i_size < offset)
72 goto do_expand;
73 i_size_write(inode, offset);
74
75 truncate_inode_pages(mapping, offset);
76 goto out_truncate;
77
78do_expand:
79 limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
80 if (limit != RLIM_INFINITY && offset > limit)
81 goto out_sig;
82 if (offset > inode->i_sb->s_maxbytes)
83 goto out;
84 i_size_write(inode, offset);
85
86out_truncate:
87 if (inode->i_op && inode->i_op->truncate)
88 inode->i_op->truncate(inode);
89 return 0;
90out_sig:
91 send_sig(SIGXFSZ, current, 0);
92out:
93 return -EFBIG;
94}
95
96EXPORT_SYMBOL(vmtruncate);
97
98/*
99 * Return the total memory allocated for this pointer, not
100 * just what the caller asked for.
101 *
102 * Doesn't have to be accurate, i.e. may have races.
103 */
104unsigned int kobjsize(const void *objp)
105{
106 struct page *page;
107
108 if (!objp || !((page = virt_to_page(objp))))
109 return 0;
110
111 if (PageSlab(page))
112 return ksize(objp);
113
114 BUG_ON(page->index < 0);
115 BUG_ON(page->index >= MAX_ORDER);
116
117 return (PAGE_SIZE << page->index);
118}
119
120/*
7b4d5b8b
DH
121 * get a list of pages in an address range belonging to the specified process
122 * and indicate the VMA that covers each page
123 * - this is potentially dodgy as we may end incrementing the page count of a
124 * slab page or a secondary page from a compound page
125 * - don't permit access to VMAs that don't support it, such as I/O mappings
1da177e4
LT
126 */
127int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
128 unsigned long start, int len, int write, int force,
129 struct page **pages, struct vm_area_struct **vmas)
130{
910e46da 131 struct vm_area_struct *vma;
7b4d5b8b
DH
132 unsigned long vm_flags;
133 int i;
134
135 /* calculate required read or write permissions.
136 * - if 'force' is set, we only require the "MAY" flags.
137 */
138 vm_flags = write ? (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
139 vm_flags &= force ? (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
1da177e4
LT
140
141 for (i = 0; i < len; i++) {
910e46da 142 vma = find_vma(mm, start);
7b4d5b8b
DH
143 if (!vma)
144 goto finish_or_fault;
145
146 /* protect what we can, including chardevs */
147 if (vma->vm_flags & (VM_IO | VM_PFNMAP) ||
148 !(vm_flags & vma->vm_flags))
149 goto finish_or_fault;
910e46da 150
1da177e4
LT
151 if (pages) {
152 pages[i] = virt_to_page(start);
153 if (pages[i])
154 page_cache_get(pages[i]);
155 }
156 if (vmas)
910e46da 157 vmas[i] = vma;
1da177e4
LT
158 start += PAGE_SIZE;
159 }
7b4d5b8b
DH
160
161 return i;
162
163finish_or_fault:
164 return i ? : -EFAULT;
1da177e4 165}
66aa2b4b
GU
166EXPORT_SYMBOL(get_user_pages);
167
1da177e4
LT
168DEFINE_RWLOCK(vmlist_lock);
169struct vm_struct *vmlist;
170
b3bdda02 171void vfree(const void *addr)
1da177e4
LT
172{
173 kfree(addr);
174}
b5073173 175EXPORT_SYMBOL(vfree);
1da177e4 176
dd0fc66f 177void *__vmalloc(unsigned long size, gfp_t gfp_mask, pgprot_t prot)
1da177e4
LT
178{
179 /*
8518609d
RD
180 * You can't specify __GFP_HIGHMEM with kmalloc() since kmalloc()
181 * returns only a logical address.
1da177e4 182 */
84097518 183 return kmalloc(size, (gfp_mask | __GFP_COMP) & ~__GFP_HIGHMEM);
1da177e4 184}
b5073173 185EXPORT_SYMBOL(__vmalloc);
1da177e4 186
f905bc44
PM
187void *vmalloc_user(unsigned long size)
188{
189 void *ret;
190
191 ret = __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
192 PAGE_KERNEL);
193 if (ret) {
194 struct vm_area_struct *vma;
195
196 down_write(&current->mm->mmap_sem);
197 vma = find_vma(current->mm, (unsigned long)ret);
198 if (vma)
199 vma->vm_flags |= VM_USERMAP;
200 up_write(&current->mm->mmap_sem);
201 }
202
203 return ret;
204}
205EXPORT_SYMBOL(vmalloc_user);
206
b3bdda02 207struct page *vmalloc_to_page(const void *addr)
1da177e4
LT
208{
209 return virt_to_page(addr);
210}
b5073173 211EXPORT_SYMBOL(vmalloc_to_page);
1da177e4 212
b3bdda02 213unsigned long vmalloc_to_pfn(const void *addr)
1da177e4
LT
214{
215 return page_to_pfn(virt_to_page(addr));
216}
b5073173 217EXPORT_SYMBOL(vmalloc_to_pfn);
1da177e4
LT
218
219long vread(char *buf, char *addr, unsigned long count)
220{
221 memcpy(buf, addr, count);
222 return count;
223}
224
225long vwrite(char *buf, char *addr, unsigned long count)
226{
227 /* Don't allow overflow */
228 if ((unsigned long) addr + count < count)
229 count = -(unsigned long) addr;
230
231 memcpy(addr, buf, count);
232 return(count);
233}
234
235/*
236 * vmalloc - allocate virtually continguos memory
237 *
238 * @size: allocation size
239 *
240 * Allocate enough pages to cover @size from the page level
241 * allocator and map them into continguos kernel virtual space.
242 *
c1c8897f 243 * For tight control over page level allocator and protection flags
1da177e4
LT
244 * use __vmalloc() instead.
245 */
246void *vmalloc(unsigned long size)
247{
248 return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL);
249}
f6138882
AM
250EXPORT_SYMBOL(vmalloc);
251
252void *vmalloc_node(unsigned long size, int node)
253{
254 return vmalloc(size);
255}
256EXPORT_SYMBOL(vmalloc_node);
1da177e4 257
b5073173
PM
258/**
259 * vmalloc_32 - allocate virtually contiguous memory (32bit addressable)
1da177e4
LT
260 * @size: allocation size
261 *
262 * Allocate enough 32bit PA addressable pages to cover @size from the
263 * page level allocator and map them into continguos kernel virtual space.
264 */
265void *vmalloc_32(unsigned long size)
266{
267 return __vmalloc(size, GFP_KERNEL, PAGE_KERNEL);
268}
b5073173
PM
269EXPORT_SYMBOL(vmalloc_32);
270
271/**
272 * vmalloc_32_user - allocate zeroed virtually contiguous 32bit memory
273 * @size: allocation size
274 *
275 * The resulting memory area is 32bit addressable and zeroed so it can be
276 * mapped to userspace without leaking data.
f905bc44
PM
277 *
278 * VM_USERMAP is set on the corresponding VMA so that subsequent calls to
279 * remap_vmalloc_range() are permissible.
b5073173
PM
280 */
281void *vmalloc_32_user(unsigned long size)
282{
f905bc44
PM
283 /*
284 * We'll have to sort out the ZONE_DMA bits for 64-bit,
285 * but for now this can simply use vmalloc_user() directly.
286 */
287 return vmalloc_user(size);
b5073173
PM
288}
289EXPORT_SYMBOL(vmalloc_32_user);
1da177e4
LT
290
291void *vmap(struct page **pages, unsigned int count, unsigned long flags, pgprot_t prot)
292{
293 BUG();
294 return NULL;
295}
b5073173 296EXPORT_SYMBOL(vmap);
1da177e4 297
b3bdda02 298void vunmap(const void *addr)
1da177e4
LT
299{
300 BUG();
301}
b5073173 302EXPORT_SYMBOL(vunmap);
1da177e4 303
1eeb66a1
CH
304/*
305 * Implement a stub for vmalloc_sync_all() if the architecture chose not to
306 * have one.
307 */
308void __attribute__((weak)) vmalloc_sync_all(void)
309{
310}
311
b5073173
PM
312int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
313 struct page *page)
314{
315 return -EINVAL;
316}
317EXPORT_SYMBOL(vm_insert_page);
318
1da177e4
LT
319/*
320 * sys_brk() for the most part doesn't need the global kernel
321 * lock, except when an application is doing something nasty
322 * like trying to un-brk an area that has already been mapped
323 * to a regular file. in this case, the unmapping will need
324 * to invoke file system routines that need the global lock.
325 */
326asmlinkage unsigned long sys_brk(unsigned long brk)
327{
328 struct mm_struct *mm = current->mm;
329
330 if (brk < mm->start_brk || brk > mm->context.end_brk)
331 return mm->brk;
332
333 if (mm->brk == brk)
334 return mm->brk;
335
336 /*
337 * Always allow shrinking brk
338 */
339 if (brk <= mm->brk) {
340 mm->brk = brk;
341 return brk;
342 }
343
344 /*
345 * Ok, looks good - let it rip.
346 */
347 return mm->brk = brk;
348}
349
350#ifdef DEBUG
351static void show_process_blocks(void)
352{
353 struct vm_list_struct *vml;
354
355 printk("Process blocks %d:", current->pid);
356
357 for (vml = &current->mm->context.vmlist; vml; vml = vml->next) {
358 printk(" %p: %p", vml, vml->vma);
359 if (vml->vma)
360 printk(" (%d @%lx #%d)",
361 kobjsize((void *) vml->vma->vm_start),
362 vml->vma->vm_start,
363 atomic_read(&vml->vma->vm_usage));
364 printk(vml->next ? " ->" : ".\n");
365 }
366}
367#endif /* DEBUG */
368
3034097a
DH
369/*
370 * add a VMA into a process's mm_struct in the appropriate place in the list
371 * - should be called with mm->mmap_sem held writelocked
372 */
373static void add_vma_to_mm(struct mm_struct *mm, struct vm_list_struct *vml)
374{
375 struct vm_list_struct **ppv;
376
377 for (ppv = &current->mm->context.vmlist; *ppv; ppv = &(*ppv)->next)
378 if ((*ppv)->vma->vm_start > vml->vma->vm_start)
379 break;
380
381 vml->next = *ppv;
382 *ppv = vml;
383}
384
385/*
386 * look up the first VMA in which addr resides, NULL if none
387 * - should be called with mm->mmap_sem at least held readlocked
388 */
389struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
390{
391 struct vm_list_struct *loop, *vml;
392
393 /* search the vm_start ordered list */
394 vml = NULL;
395 for (loop = mm->context.vmlist; loop; loop = loop->next) {
396 if (loop->vma->vm_start > addr)
397 break;
398 vml = loop;
399 }
400
401 if (vml && vml->vma->vm_end > addr)
402 return vml->vma;
403
404 return NULL;
405}
406EXPORT_SYMBOL(find_vma);
407
930e652a
DH
408/*
409 * find a VMA
410 * - we don't extend stack VMAs under NOMMU conditions
411 */
412struct vm_area_struct *find_extend_vma(struct mm_struct *mm, unsigned long addr)
413{
414 return find_vma(mm, addr);
415}
416
57c8f63e
GU
417int expand_stack(struct vm_area_struct *vma, unsigned long address)
418{
419 return -ENOMEM;
420}
421
6fa5f80b
DH
422/*
423 * look up the first VMA exactly that exactly matches addr
424 * - should be called with mm->mmap_sem at least held readlocked
425 */
426static inline struct vm_area_struct *find_vma_exact(struct mm_struct *mm,
427 unsigned long addr)
428{
429 struct vm_list_struct *vml;
430
431 /* search the vm_start ordered list */
432 for (vml = mm->context.vmlist; vml; vml = vml->next) {
433 if (vml->vma->vm_start == addr)
434 return vml->vma;
435 if (vml->vma->vm_start > addr)
436 break;
437 }
438
439 return NULL;
440}
441
3034097a
DH
442/*
443 * find a VMA in the global tree
444 */
1da177e4
LT
445static inline struct vm_area_struct *find_nommu_vma(unsigned long start)
446{
447 struct vm_area_struct *vma;
448 struct rb_node *n = nommu_vma_tree.rb_node;
449
450 while (n) {
451 vma = rb_entry(n, struct vm_area_struct, vm_rb);
452
453 if (start < vma->vm_start)
454 n = n->rb_left;
455 else if (start > vma->vm_start)
456 n = n->rb_right;
457 else
458 return vma;
459 }
460
461 return NULL;
462}
463
3034097a
DH
464/*
465 * add a VMA in the global tree
466 */
1da177e4
LT
467static void add_nommu_vma(struct vm_area_struct *vma)
468{
469 struct vm_area_struct *pvma;
470 struct address_space *mapping;
471 struct rb_node **p = &nommu_vma_tree.rb_node;
472 struct rb_node *parent = NULL;
473
474 /* add the VMA to the mapping */
475 if (vma->vm_file) {
476 mapping = vma->vm_file->f_mapping;
477
478 flush_dcache_mmap_lock(mapping);
479 vma_prio_tree_insert(vma, &mapping->i_mmap);
480 flush_dcache_mmap_unlock(mapping);
481 }
482
483 /* add the VMA to the master list */
484 while (*p) {
485 parent = *p;
486 pvma = rb_entry(parent, struct vm_area_struct, vm_rb);
487
488 if (vma->vm_start < pvma->vm_start) {
489 p = &(*p)->rb_left;
490 }
491 else if (vma->vm_start > pvma->vm_start) {
492 p = &(*p)->rb_right;
493 }
494 else {
495 /* mappings are at the same address - this can only
496 * happen for shared-mem chardevs and shared file
497 * mappings backed by ramfs/tmpfs */
498 BUG_ON(!(pvma->vm_flags & VM_SHARED));
499
500 if (vma < pvma)
501 p = &(*p)->rb_left;
502 else if (vma > pvma)
503 p = &(*p)->rb_right;
504 else
505 BUG();
506 }
507 }
508
509 rb_link_node(&vma->vm_rb, parent, p);
510 rb_insert_color(&vma->vm_rb, &nommu_vma_tree);
511}
512
3034097a
DH
513/*
514 * delete a VMA from the global list
515 */
1da177e4
LT
516static void delete_nommu_vma(struct vm_area_struct *vma)
517{
518 struct address_space *mapping;
519
520 /* remove the VMA from the mapping */
521 if (vma->vm_file) {
522 mapping = vma->vm_file->f_mapping;
523
524 flush_dcache_mmap_lock(mapping);
525 vma_prio_tree_remove(vma, &mapping->i_mmap);
526 flush_dcache_mmap_unlock(mapping);
527 }
528
529 /* remove from the master list */
530 rb_erase(&vma->vm_rb, &nommu_vma_tree);
531}
532
533/*
534 * determine whether a mapping should be permitted and, if so, what sort of
535 * mapping we're capable of supporting
536 */
537static int validate_mmap_request(struct file *file,
538 unsigned long addr,
539 unsigned long len,
540 unsigned long prot,
541 unsigned long flags,
542 unsigned long pgoff,
543 unsigned long *_capabilities)
544{
545 unsigned long capabilities;
546 unsigned long reqprot = prot;
547 int ret;
548
549 /* do the simple checks first */
550 if (flags & MAP_FIXED || addr) {
551 printk(KERN_DEBUG
552 "%d: Can't do fixed-address/overlay mmap of RAM\n",
553 current->pid);
554 return -EINVAL;
555 }
556
557 if ((flags & MAP_TYPE) != MAP_PRIVATE &&
558 (flags & MAP_TYPE) != MAP_SHARED)
559 return -EINVAL;
560
f81cff0d 561 if (!len)
1da177e4
LT
562 return -EINVAL;
563
f81cff0d
MF
564 /* Careful about overflows.. */
565 len = PAGE_ALIGN(len);
566 if (!len || len > TASK_SIZE)
567 return -ENOMEM;
568
1da177e4
LT
569 /* offset overflow? */
570 if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
f81cff0d 571 return -EOVERFLOW;
1da177e4
LT
572
573 if (file) {
574 /* validate file mapping requests */
575 struct address_space *mapping;
576
577 /* files must support mmap */
578 if (!file->f_op || !file->f_op->mmap)
579 return -ENODEV;
580
581 /* work out if what we've got could possibly be shared
582 * - we support chardevs that provide their own "memory"
583 * - we support files/blockdevs that are memory backed
584 */
585 mapping = file->f_mapping;
586 if (!mapping)
e9536ae7 587 mapping = file->f_path.dentry->d_inode->i_mapping;
1da177e4
LT
588
589 capabilities = 0;
590 if (mapping && mapping->backing_dev_info)
591 capabilities = mapping->backing_dev_info->capabilities;
592
593 if (!capabilities) {
594 /* no explicit capabilities set, so assume some
595 * defaults */
e9536ae7 596 switch (file->f_path.dentry->d_inode->i_mode & S_IFMT) {
1da177e4
LT
597 case S_IFREG:
598 case S_IFBLK:
599 capabilities = BDI_CAP_MAP_COPY;
600 break;
601
602 case S_IFCHR:
603 capabilities =
604 BDI_CAP_MAP_DIRECT |
605 BDI_CAP_READ_MAP |
606 BDI_CAP_WRITE_MAP;
607 break;
608
609 default:
610 return -EINVAL;
611 }
612 }
613
614 /* eliminate any capabilities that we can't support on this
615 * device */
616 if (!file->f_op->get_unmapped_area)
617 capabilities &= ~BDI_CAP_MAP_DIRECT;
618 if (!file->f_op->read)
619 capabilities &= ~BDI_CAP_MAP_COPY;
620
621 if (flags & MAP_SHARED) {
622 /* do checks for writing, appending and locking */
623 if ((prot & PROT_WRITE) &&
624 !(file->f_mode & FMODE_WRITE))
625 return -EACCES;
626
e9536ae7 627 if (IS_APPEND(file->f_path.dentry->d_inode) &&
1da177e4
LT
628 (file->f_mode & FMODE_WRITE))
629 return -EACCES;
630
e9536ae7 631 if (locks_verify_locked(file->f_path.dentry->d_inode))
1da177e4
LT
632 return -EAGAIN;
633
634 if (!(capabilities & BDI_CAP_MAP_DIRECT))
635 return -ENODEV;
636
637 if (((prot & PROT_READ) && !(capabilities & BDI_CAP_READ_MAP)) ||
638 ((prot & PROT_WRITE) && !(capabilities & BDI_CAP_WRITE_MAP)) ||
639 ((prot & PROT_EXEC) && !(capabilities & BDI_CAP_EXEC_MAP))
640 ) {
641 printk("MAP_SHARED not completely supported on !MMU\n");
642 return -EINVAL;
643 }
644
645 /* we mustn't privatise shared mappings */
646 capabilities &= ~BDI_CAP_MAP_COPY;
647 }
648 else {
649 /* we're going to read the file into private memory we
650 * allocate */
651 if (!(capabilities & BDI_CAP_MAP_COPY))
652 return -ENODEV;
653
654 /* we don't permit a private writable mapping to be
655 * shared with the backing device */
656 if (prot & PROT_WRITE)
657 capabilities &= ~BDI_CAP_MAP_DIRECT;
658 }
659
660 /* handle executable mappings and implied executable
661 * mappings */
e9536ae7 662 if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) {
1da177e4
LT
663 if (prot & PROT_EXEC)
664 return -EPERM;
665 }
666 else if ((prot & PROT_READ) && !(prot & PROT_EXEC)) {
667 /* handle implication of PROT_EXEC by PROT_READ */
668 if (current->personality & READ_IMPLIES_EXEC) {
669 if (capabilities & BDI_CAP_EXEC_MAP)
670 prot |= PROT_EXEC;
671 }
672 }
673 else if ((prot & PROT_READ) &&
674 (prot & PROT_EXEC) &&
675 !(capabilities & BDI_CAP_EXEC_MAP)
676 ) {
677 /* backing file is not executable, try to copy */
678 capabilities &= ~BDI_CAP_MAP_DIRECT;
679 }
680 }
681 else {
682 /* anonymous mappings are always memory backed and can be
683 * privately mapped
684 */
685 capabilities = BDI_CAP_MAP_COPY;
686
687 /* handle PROT_EXEC implication by PROT_READ */
688 if ((prot & PROT_READ) &&
689 (current->personality & READ_IMPLIES_EXEC))
690 prot |= PROT_EXEC;
691 }
692
693 /* allow the security API to have its say */
ed032189 694 ret = security_file_mmap(file, reqprot, prot, flags, addr, 0);
1da177e4
LT
695 if (ret < 0)
696 return ret;
697
698 /* looks okay */
699 *_capabilities = capabilities;
700 return 0;
701}
702
703/*
704 * we've determined that we can make the mapping, now translate what we
705 * now know into VMA flags
706 */
707static unsigned long determine_vm_flags(struct file *file,
708 unsigned long prot,
709 unsigned long flags,
710 unsigned long capabilities)
711{
712 unsigned long vm_flags;
713
714 vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags);
715 vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
716 /* vm_flags |= mm->def_flags; */
717
718 if (!(capabilities & BDI_CAP_MAP_DIRECT)) {
719 /* attempt to share read-only copies of mapped file chunks */
720 if (file && !(prot & PROT_WRITE))
721 vm_flags |= VM_MAYSHARE;
722 }
723 else {
724 /* overlay a shareable mapping on the backing device or inode
725 * if possible - used for chardevs, ramfs/tmpfs/shmfs and
726 * romfs/cramfs */
727 if (flags & MAP_SHARED)
728 vm_flags |= VM_MAYSHARE | VM_SHARED;
729 else if ((((vm_flags & capabilities) ^ vm_flags) & BDI_CAP_VMFLAGS) == 0)
730 vm_flags |= VM_MAYSHARE;
731 }
732
733 /* refuse to let anyone share private mappings with this process if
734 * it's being traced - otherwise breakpoints set in it may interfere
735 * with another untraced process
736 */
737 if ((flags & MAP_PRIVATE) && (current->ptrace & PT_PTRACED))
738 vm_flags &= ~VM_MAYSHARE;
739
740 return vm_flags;
741}
742
743/*
744 * set up a shared mapping on a file
745 */
746static int do_mmap_shared_file(struct vm_area_struct *vma, unsigned long len)
747{
748 int ret;
749
750 ret = vma->vm_file->f_op->mmap(vma->vm_file, vma);
751 if (ret != -ENOSYS)
752 return ret;
753
754 /* getting an ENOSYS error indicates that direct mmap isn't
755 * possible (as opposed to tried but failed) so we'll fall
756 * through to making a private copy of the data and mapping
757 * that if we can */
758 return -ENODEV;
759}
760
761/*
762 * set up a private mapping or an anonymous shared mapping
763 */
764static int do_mmap_private(struct vm_area_struct *vma, unsigned long len)
765{
766 void *base;
767 int ret;
768
769 /* invoke the file's mapping function so that it can keep track of
770 * shared mappings on devices or memory
771 * - VM_MAYSHARE will be set if it may attempt to share
772 */
773 if (vma->vm_file) {
774 ret = vma->vm_file->f_op->mmap(vma->vm_file, vma);
775 if (ret != -ENOSYS) {
776 /* shouldn't return success if we're not sharing */
777 BUG_ON(ret == 0 && !(vma->vm_flags & VM_MAYSHARE));
778 return ret; /* success or a real error */
779 }
780
781 /* getting an ENOSYS error indicates that direct mmap isn't
782 * possible (as opposed to tried but failed) so we'll try to
783 * make a private copy of the data and map that instead */
784 }
785
786 /* allocate some memory to hold the mapping
787 * - note that this may not return a page-aligned address if the object
788 * we're allocating is smaller than a page
789 */
84097518 790 base = kmalloc(len, GFP_KERNEL|__GFP_COMP);
1da177e4
LT
791 if (!base)
792 goto enomem;
793
794 vma->vm_start = (unsigned long) base;
795 vma->vm_end = vma->vm_start + len;
796 vma->vm_flags |= VM_MAPPED_COPY;
797
798#ifdef WARN_ON_SLACK
799 if (len + WARN_ON_SLACK <= kobjsize(result))
800 printk("Allocation of %lu bytes from process %d has %lu bytes of slack\n",
801 len, current->pid, kobjsize(result) - len);
802#endif
803
804 if (vma->vm_file) {
805 /* read the contents of a file into the copy */
806 mm_segment_t old_fs;
807 loff_t fpos;
808
809 fpos = vma->vm_pgoff;
810 fpos <<= PAGE_SHIFT;
811
812 old_fs = get_fs();
813 set_fs(KERNEL_DS);
814 ret = vma->vm_file->f_op->read(vma->vm_file, base, len, &fpos);
815 set_fs(old_fs);
816
817 if (ret < 0)
818 goto error_free;
819
820 /* clear the last little bit */
821 if (ret < len)
822 memset(base + ret, 0, len - ret);
823
824 } else {
825 /* if it's an anonymous mapping, then just clear it */
826 memset(base, 0, len);
827 }
828
829 return 0;
830
831error_free:
832 kfree(base);
833 vma->vm_start = 0;
834 return ret;
835
836enomem:
837 printk("Allocation of length %lu from process %d failed\n",
838 len, current->pid);
839 show_free_areas();
840 return -ENOMEM;
841}
842
843/*
844 * handle mapping creation for uClinux
845 */
846unsigned long do_mmap_pgoff(struct file *file,
847 unsigned long addr,
848 unsigned long len,
849 unsigned long prot,
850 unsigned long flags,
851 unsigned long pgoff)
852{
853 struct vm_list_struct *vml = NULL;
854 struct vm_area_struct *vma = NULL;
855 struct rb_node *rb;
856 unsigned long capabilities, vm_flags;
857 void *result;
858 int ret;
859
7cd94146
EP
860 if (!(flags & MAP_FIXED))
861 addr = round_hint_to_min(addr);
862
1da177e4
LT
863 /* decide whether we should attempt the mapping, and if so what sort of
864 * mapping */
865 ret = validate_mmap_request(file, addr, len, prot, flags, pgoff,
866 &capabilities);
867 if (ret < 0)
868 return ret;
869
870 /* we've determined that we can make the mapping, now translate what we
871 * now know into VMA flags */
872 vm_flags = determine_vm_flags(file, prot, flags, capabilities);
873
874 /* we're going to need to record the mapping if it works */
4668edc3 875 vml = kzalloc(sizeof(struct vm_list_struct), GFP_KERNEL);
1da177e4
LT
876 if (!vml)
877 goto error_getting_vml;
1da177e4
LT
878
879 down_write(&nommu_vma_sem);
880
881 /* if we want to share, we need to check for VMAs created by other
882 * mmap() calls that overlap with our proposed mapping
883 * - we can only share with an exact match on most regular files
884 * - shared mappings on character devices and memory backed files are
885 * permitted to overlap inexactly as far as we are concerned for in
886 * these cases, sharing is handled in the driver or filesystem rather
887 * than here
888 */
889 if (vm_flags & VM_MAYSHARE) {
890 unsigned long pglen = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
891 unsigned long vmpglen;
892
165b2392
DH
893 /* suppress VMA sharing for shared regions */
894 if (vm_flags & VM_SHARED &&
895 capabilities & BDI_CAP_MAP_DIRECT)
896 goto dont_share_VMAs;
897
1da177e4
LT
898 for (rb = rb_first(&nommu_vma_tree); rb; rb = rb_next(rb)) {
899 vma = rb_entry(rb, struct vm_area_struct, vm_rb);
900
901 if (!(vma->vm_flags & VM_MAYSHARE))
902 continue;
903
904 /* search for overlapping mappings on the same file */
e9536ae7 905 if (vma->vm_file->f_path.dentry->d_inode != file->f_path.dentry->d_inode)
1da177e4
LT
906 continue;
907
908 if (vma->vm_pgoff >= pgoff + pglen)
909 continue;
910
911 vmpglen = vma->vm_end - vma->vm_start + PAGE_SIZE - 1;
912 vmpglen >>= PAGE_SHIFT;
913 if (pgoff >= vma->vm_pgoff + vmpglen)
914 continue;
915
916 /* handle inexactly overlapping matches between mappings */
917 if (vma->vm_pgoff != pgoff || vmpglen != pglen) {
918 if (!(capabilities & BDI_CAP_MAP_DIRECT))
919 goto sharing_violation;
920 continue;
921 }
922
923 /* we've found a VMA we can share */
924 atomic_inc(&vma->vm_usage);
925
926 vml->vma = vma;
927 result = (void *) vma->vm_start;
928 goto shared;
929 }
930
165b2392 931 dont_share_VMAs:
1da177e4
LT
932 vma = NULL;
933
934 /* obtain the address at which to make a shared mapping
935 * - this is the hook for quasi-memory character devices to
936 * tell us the location of a shared mapping
937 */
938 if (file && file->f_op->get_unmapped_area) {
939 addr = file->f_op->get_unmapped_area(file, addr, len,
940 pgoff, flags);
941 if (IS_ERR((void *) addr)) {
942 ret = addr;
943 if (ret != (unsigned long) -ENOSYS)
944 goto error;
945
946 /* the driver refused to tell us where to site
947 * the mapping so we'll have to attempt to copy
948 * it */
949 ret = (unsigned long) -ENODEV;
950 if (!(capabilities & BDI_CAP_MAP_COPY))
951 goto error;
952
953 capabilities &= ~BDI_CAP_MAP_DIRECT;
954 }
955 }
956 }
957
958 /* we're going to need a VMA struct as well */
4668edc3 959 vma = kzalloc(sizeof(struct vm_area_struct), GFP_KERNEL);
1da177e4
LT
960 if (!vma)
961 goto error_getting_vma;
962
1da177e4
LT
963 INIT_LIST_HEAD(&vma->anon_vma_node);
964 atomic_set(&vma->vm_usage, 1);
965 if (file)
966 get_file(file);
967 vma->vm_file = file;
968 vma->vm_flags = vm_flags;
969 vma->vm_start = addr;
970 vma->vm_end = addr + len;
971 vma->vm_pgoff = pgoff;
972
973 vml->vma = vma;
974
975 /* set up the mapping */
976 if (file && vma->vm_flags & VM_SHARED)
977 ret = do_mmap_shared_file(vma, len);
978 else
979 ret = do_mmap_private(vma, len);
980 if (ret < 0)
981 goto error;
982
983 /* okay... we have a mapping; now we have to register it */
984 result = (void *) vma->vm_start;
985
986 if (vma->vm_flags & VM_MAPPED_COPY) {
987 realalloc += kobjsize(result);
988 askedalloc += len;
989 }
990
991 realalloc += kobjsize(vma);
992 askedalloc += sizeof(*vma);
993
994 current->mm->total_vm += len >> PAGE_SHIFT;
995
996 add_nommu_vma(vma);
997
998 shared:
999 realalloc += kobjsize(vml);
1000 askedalloc += sizeof(*vml);
1001
3034097a 1002 add_vma_to_mm(current->mm, vml);
1da177e4
LT
1003
1004 up_write(&nommu_vma_sem);
1005
1006 if (prot & PROT_EXEC)
1007 flush_icache_range((unsigned long) result,
1008 (unsigned long) result + len);
1009
1010#ifdef DEBUG
1011 printk("do_mmap:\n");
1012 show_process_blocks();
1013#endif
1014
1015 return (unsigned long) result;
1016
1017 error:
1018 up_write(&nommu_vma_sem);
1019 kfree(vml);
1020 if (vma) {
3fcd03e0
GL
1021 if (vma->vm_file)
1022 fput(vma->vm_file);
1da177e4
LT
1023 kfree(vma);
1024 }
1025 return ret;
1026
1027 sharing_violation:
1028 up_write(&nommu_vma_sem);
1029 printk("Attempt to share mismatched mappings\n");
1030 kfree(vml);
1031 return -EINVAL;
1032
1033 error_getting_vma:
1034 up_write(&nommu_vma_sem);
1035 kfree(vml);
66aa2b4b 1036 printk("Allocation of vma for %lu byte allocation from process %d failed\n",
1da177e4
LT
1037 len, current->pid);
1038 show_free_areas();
1039 return -ENOMEM;
1040
1041 error_getting_vml:
1042 printk("Allocation of vml for %lu byte allocation from process %d failed\n",
1043 len, current->pid);
1044 show_free_areas();
1045 return -ENOMEM;
1046}
b5073173 1047EXPORT_SYMBOL(do_mmap_pgoff);
1da177e4
LT
1048
1049/*
1050 * handle mapping disposal for uClinux
1051 */
1052static void put_vma(struct vm_area_struct *vma)
1053{
1054 if (vma) {
1055 down_write(&nommu_vma_sem);
1056
1057 if (atomic_dec_and_test(&vma->vm_usage)) {
1058 delete_nommu_vma(vma);
1059
1060 if (vma->vm_ops && vma->vm_ops->close)
1061 vma->vm_ops->close(vma);
1062
1063 /* IO memory and memory shared directly out of the pagecache from
1064 * ramfs/tmpfs mustn't be released here */
1065 if (vma->vm_flags & VM_MAPPED_COPY) {
1066 realalloc -= kobjsize((void *) vma->vm_start);
1067 askedalloc -= vma->vm_end - vma->vm_start;
1068 kfree((void *) vma->vm_start);
1069 }
1070
1071 realalloc -= kobjsize(vma);
1072 askedalloc -= sizeof(*vma);
1073
1074 if (vma->vm_file)
1075 fput(vma->vm_file);
1076 kfree(vma);
1077 }
1078
1079 up_write(&nommu_vma_sem);
1080 }
1081}
1082
3034097a
DH
1083/*
1084 * release a mapping
1085 * - under NOMMU conditions the parameters must match exactly to the mapping to
1086 * be removed
1087 */
1da177e4
LT
1088int do_munmap(struct mm_struct *mm, unsigned long addr, size_t len)
1089{
1090 struct vm_list_struct *vml, **parent;
1091 unsigned long end = addr + len;
1092
1093#ifdef DEBUG
1094 printk("do_munmap:\n");
1095#endif
1096
3034097a
DH
1097 for (parent = &mm->context.vmlist; *parent; parent = &(*parent)->next) {
1098 if ((*parent)->vma->vm_start > addr)
1099 break;
1da177e4 1100 if ((*parent)->vma->vm_start == addr &&
66aa2b4b 1101 ((len == 0) || ((*parent)->vma->vm_end == end)))
1da177e4 1102 goto found;
3034097a 1103 }
1da177e4
LT
1104
1105 printk("munmap of non-mmaped memory by process %d (%s): %p\n",
1106 current->pid, current->comm, (void *) addr);
1107 return -EINVAL;
1108
1109 found:
1110 vml = *parent;
1111
1112 put_vma(vml->vma);
1113
1114 *parent = vml->next;
1115 realalloc -= kobjsize(vml);
1116 askedalloc -= sizeof(*vml);
1117 kfree(vml);
365e9c87
HD
1118
1119 update_hiwater_vm(mm);
1da177e4
LT
1120 mm->total_vm -= len >> PAGE_SHIFT;
1121
1122#ifdef DEBUG
1123 show_process_blocks();
1124#endif
1125
1126 return 0;
1127}
b5073173 1128EXPORT_SYMBOL(do_munmap);
1da177e4 1129
3034097a
DH
1130asmlinkage long sys_munmap(unsigned long addr, size_t len)
1131{
1132 int ret;
1133 struct mm_struct *mm = current->mm;
1134
1135 down_write(&mm->mmap_sem);
1136 ret = do_munmap(mm, addr, len);
1137 up_write(&mm->mmap_sem);
1138 return ret;
1139}
1140
1141/*
1142 * Release all mappings
1143 */
1da177e4
LT
1144void exit_mmap(struct mm_struct * mm)
1145{
1146 struct vm_list_struct *tmp;
1147
1148 if (mm) {
1149#ifdef DEBUG
1150 printk("Exit_mmap:\n");
1151#endif
1152
1153 mm->total_vm = 0;
1154
1155 while ((tmp = mm->context.vmlist)) {
1156 mm->context.vmlist = tmp->next;
1157 put_vma(tmp->vma);
1158
1159 realalloc -= kobjsize(tmp);
1160 askedalloc -= sizeof(*tmp);
1161 kfree(tmp);
1162 }
1163
1164#ifdef DEBUG
1165 show_process_blocks();
1166#endif
1167 }
1168}
1169
1da177e4
LT
1170unsigned long do_brk(unsigned long addr, unsigned long len)
1171{
1172 return -ENOMEM;
1173}
1174
1175/*
6fa5f80b
DH
1176 * expand (or shrink) an existing mapping, potentially moving it at the same
1177 * time (controlled by the MREMAP_MAYMOVE flag and available VM space)
1da177e4 1178 *
6fa5f80b
DH
1179 * under NOMMU conditions, we only permit changing a mapping's size, and only
1180 * as long as it stays within the hole allocated by the kmalloc() call in
1181 * do_mmap_pgoff() and the block is not shareable
1da177e4 1182 *
6fa5f80b 1183 * MREMAP_FIXED is not supported under NOMMU conditions
1da177e4
LT
1184 */
1185unsigned long do_mremap(unsigned long addr,
1186 unsigned long old_len, unsigned long new_len,
1187 unsigned long flags, unsigned long new_addr)
1188{
6fa5f80b 1189 struct vm_area_struct *vma;
1da177e4
LT
1190
1191 /* insanity checks first */
1192 if (new_len == 0)
1193 return (unsigned long) -EINVAL;
1194
1195 if (flags & MREMAP_FIXED && new_addr != addr)
1196 return (unsigned long) -EINVAL;
1197
6fa5f80b
DH
1198 vma = find_vma_exact(current->mm, addr);
1199 if (!vma)
1200 return (unsigned long) -EINVAL;
1da177e4 1201
6fa5f80b 1202 if (vma->vm_end != vma->vm_start + old_len)
1da177e4
LT
1203 return (unsigned long) -EFAULT;
1204
6fa5f80b 1205 if (vma->vm_flags & VM_MAYSHARE)
1da177e4
LT
1206 return (unsigned long) -EPERM;
1207
1208 if (new_len > kobjsize((void *) addr))
1209 return (unsigned long) -ENOMEM;
1210
1211 /* all checks complete - do it */
6fa5f80b 1212 vma->vm_end = vma->vm_start + new_len;
1da177e4
LT
1213
1214 askedalloc -= old_len;
1215 askedalloc += new_len;
1216
6fa5f80b
DH
1217 return vma->vm_start;
1218}
b5073173 1219EXPORT_SYMBOL(do_mremap);
6fa5f80b
DH
1220
1221asmlinkage unsigned long sys_mremap(unsigned long addr,
1222 unsigned long old_len, unsigned long new_len,
1223 unsigned long flags, unsigned long new_addr)
1224{
1225 unsigned long ret;
1226
1227 down_write(&current->mm->mmap_sem);
1228 ret = do_mremap(addr, old_len, new_len, flags, new_addr);
1229 up_write(&current->mm->mmap_sem);
1230 return ret;
1da177e4
LT
1231}
1232
6aab341e 1233struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
deceb6cd 1234 unsigned int foll_flags)
1da177e4
LT
1235{
1236 return NULL;
1237}
1238
1da177e4
LT
1239int remap_pfn_range(struct vm_area_struct *vma, unsigned long from,
1240 unsigned long to, unsigned long size, pgprot_t prot)
1241{
66aa2b4b
GU
1242 vma->vm_start = vma->vm_pgoff << PAGE_SHIFT;
1243 return 0;
1da177e4 1244}
22c4af40 1245EXPORT_SYMBOL(remap_pfn_range);
1da177e4 1246
f905bc44
PM
1247int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
1248 unsigned long pgoff)
1249{
1250 unsigned int size = vma->vm_end - vma->vm_start;
1251
1252 if (!(vma->vm_flags & VM_USERMAP))
1253 return -EINVAL;
1254
1255 vma->vm_start = (unsigned long)(addr + (pgoff << PAGE_SHIFT));
1256 vma->vm_end = vma->vm_start + size;
1257
1258 return 0;
1259}
1260EXPORT_SYMBOL(remap_vmalloc_range);
1261
1da177e4
LT
1262void swap_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
1263{
1264}
1265
1266unsigned long arch_get_unmapped_area(struct file *file, unsigned long addr,
1267 unsigned long len, unsigned long pgoff, unsigned long flags)
1268{
1269 return -ENOMEM;
1270}
1271
1363c3cd 1272void arch_unmap_area(struct mm_struct *mm, unsigned long addr)
1da177e4
LT
1273{
1274}
1275
1da177e4
LT
1276void unmap_mapping_range(struct address_space *mapping,
1277 loff_t const holebegin, loff_t const holelen,
1278 int even_cows)
1279{
1280}
22c4af40 1281EXPORT_SYMBOL(unmap_mapping_range);
1da177e4 1282
d56e03cd
DH
1283/*
1284 * ask for an unmapped area at which to create a mapping on a file
1285 */
1286unsigned long get_unmapped_area(struct file *file, unsigned long addr,
1287 unsigned long len, unsigned long pgoff,
1288 unsigned long flags)
1289{
1290 unsigned long (*get_area)(struct file *, unsigned long, unsigned long,
1291 unsigned long, unsigned long);
1292
1293 get_area = current->mm->get_unmapped_area;
1294 if (file && file->f_op && file->f_op->get_unmapped_area)
1295 get_area = file->f_op->get_unmapped_area;
1296
1297 if (!get_area)
1298 return -ENOSYS;
1299
1300 return get_area(file, addr, len, pgoff, flags);
1301}
d56e03cd
DH
1302EXPORT_SYMBOL(get_unmapped_area);
1303
1da177e4
LT
1304/*
1305 * Check that a process has enough memory to allocate a new virtual
1306 * mapping. 0 means there is enough memory for the allocation to
1307 * succeed and -ENOMEM implies there is not.
1308 *
1309 * We currently support three overcommit policies, which are set via the
1310 * vm.overcommit_memory sysctl. See Documentation/vm/overcommit-accounting
1311 *
1312 * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
1313 * Additional code 2002 Jul 20 by Robert Love.
1314 *
1315 * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
1316 *
1317 * Note this is a helper function intended to be used by LSMs which
1318 * wish to use this logic.
1319 */
34b4e4aa 1320int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
1da177e4
LT
1321{
1322 unsigned long free, allowed;
1323
1324 vm_acct_memory(pages);
1325
1326 /*
1327 * Sometimes we want to use more memory than we have
1328 */
1329 if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
1330 return 0;
1331
1332 if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
1333 unsigned long n;
1334
347ce434 1335 free = global_page_state(NR_FILE_PAGES);
1da177e4
LT
1336 free += nr_swap_pages;
1337
1338 /*
1339 * Any slabs which are created with the
1340 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
1341 * which are reclaimable, under pressure. The dentry
1342 * cache and most inode caches should fall into this
1343 */
972d1a7b 1344 free += global_page_state(NR_SLAB_RECLAIMABLE);
1da177e4
LT
1345
1346 /*
1347 * Leave the last 3% for root
1348 */
1349 if (!cap_sys_admin)
1350 free -= free / 32;
1351
1352 if (free > pages)
1353 return 0;
1354
1355 /*
1356 * nr_free_pages() is very expensive on large systems,
1357 * only call if we're about to fail.
1358 */
1359 n = nr_free_pages();
d5ddc79b
HA
1360
1361 /*
1362 * Leave reserved pages. The pages are not for anonymous pages.
1363 */
1364 if (n <= totalreserve_pages)
1365 goto error;
1366 else
1367 n -= totalreserve_pages;
1368
1369 /*
1370 * Leave the last 3% for root
1371 */
1da177e4
LT
1372 if (!cap_sys_admin)
1373 n -= n / 32;
1374 free += n;
1375
1376 if (free > pages)
1377 return 0;
d5ddc79b
HA
1378
1379 goto error;
1da177e4
LT
1380 }
1381
1382 allowed = totalram_pages * sysctl_overcommit_ratio / 100;
1383 /*
1384 * Leave the last 3% for root
1385 */
1386 if (!cap_sys_admin)
1387 allowed -= allowed / 32;
1388 allowed += total_swap_pages;
1389
1390 /* Don't let a single process grow too big:
1391 leave 3% of the size of this process for other processes */
1392 allowed -= current->mm->total_vm / 32;
1393
2f60f8d3
SD
1394 /*
1395 * cast `allowed' as a signed long because vm_committed_space
1396 * sometimes has a negative value
1397 */
1398 if (atomic_read(&vm_committed_space) < (long)allowed)
1da177e4 1399 return 0;
d5ddc79b 1400error:
1da177e4
LT
1401 vm_unacct_memory(pages);
1402
1403 return -ENOMEM;
1404}
1405
1406int in_gate_area_no_task(unsigned long addr)
1407{
1408 return 0;
1409}
b0e15190 1410
d0217ac0 1411int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
b0e15190
DH
1412{
1413 BUG();
d0217ac0 1414 return 0;
b0e15190 1415}
b5073173 1416EXPORT_SYMBOL(filemap_fault);
0ec76a11
DH
1417
1418/*
1419 * Access another process' address space.
1420 * - source/target buffer must be kernel space
1421 */
1422int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
1423{
0ec76a11
DH
1424 struct vm_area_struct *vma;
1425 struct mm_struct *mm;
1426
1427 if (addr + len < addr)
1428 return 0;
1429
1430 mm = get_task_mm(tsk);
1431 if (!mm)
1432 return 0;
1433
1434 down_read(&mm->mmap_sem);
1435
1436 /* the access must start within one of the target process's mappings */
0159b141
DH
1437 vma = find_vma(mm, addr);
1438 if (vma) {
0ec76a11
DH
1439 /* don't overrun this mapping */
1440 if (addr + len >= vma->vm_end)
1441 len = vma->vm_end - addr;
1442
1443 /* only read or write mappings where it is permitted */
d00c7b99 1444 if (write && vma->vm_flags & VM_MAYWRITE)
0ec76a11 1445 len -= copy_to_user((void *) addr, buf, len);
d00c7b99 1446 else if (!write && vma->vm_flags & VM_MAYREAD)
0ec76a11
DH
1447 len -= copy_from_user(buf, (void *) addr, len);
1448 else
1449 len = 0;
1450 } else {
1451 len = 0;
1452 }
1453
1454 up_read(&mm->mmap_sem);
1455 mmput(mm);
1456 return len;
1457}