nommu: fix kobjsize() for SLOB and SLUB
[linux-2.6.git] / mm / nommu.c
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  *  Copyright (c) 2007      Paul Mundt <lethal@linux-sh.org>
14  */
15
16 #include <linux/module.h>
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
37 void *high_memory;
38 struct page *mem_map;
39 unsigned long max_mapnr;
40 unsigned long num_physpages;
41 unsigned long askedalloc, realalloc;
42 atomic_long_t vm_committed_space = ATOMIC_LONG_INIT(0);
43 int sysctl_overcommit_memory = OVERCOMMIT_GUESS; /* heuristic overcommit */
44 int sysctl_overcommit_ratio = 50; /* default is 50% */
45 int sysctl_max_map_count = DEFAULT_MAX_MAP_COUNT;
46 int heap_stack_gap = 0;
47
48 EXPORT_SYMBOL(mem_map);
49 EXPORT_SYMBOL(num_physpages);
50
51 /* list of shareable VMAs */
52 struct rb_root nommu_vma_tree = RB_ROOT;
53 DECLARE_RWSEM(nommu_vma_sem);
54
55 struct 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  */
66 int 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
78 do_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
86 out_truncate:
87         if (inode->i_op && inode->i_op->truncate)
88                 inode->i_op->truncate(inode);
89         return 0;
90 out_sig:
91         send_sig(SIGXFSZ, current, 0);
92 out:
93         return -EFBIG;
94 }
95
96 EXPORT_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  */
104 unsigned int kobjsize(const void *objp)
105 {
106         struct page *page;
107         int order = 0;
108
109         /*
110          * If the object we have should not have ksize performed on it,
111          * return size of 0
112          */
113         if (!objp)
114                 return 0;
115
116         if ((unsigned long)objp >= memory_end)
117                 return 0;
118
119         page = virt_to_head_page(objp);
120         if (!page)
121                 return 0;
122
123         /*
124          * If the allocator sets PageSlab, we know the pointer came from
125          * kmalloc().
126          */
127         if (PageSlab(page))
128                 return ksize(objp);
129
130         /*
131          * The ksize() function is only guaranteed to work for pointers
132          * returned by kmalloc(). So handle arbitrary pointers, that we expect
133          * always to be compound pages, here.
134          */
135         if (PageCompound(page))
136                 order = compound_order(page);
137
138         /*
139          * Finally, handle arbitrary pointers that don't set PageSlab.
140          * Default to 0-order in the case when we're unable to ksize()
141          * the object.
142          */
143         return PAGE_SIZE << order;
144 }
145
146 /*
147  * get a list of pages in an address range belonging to the specified process
148  * and indicate the VMA that covers each page
149  * - this is potentially dodgy as we may end incrementing the page count of a
150  *   slab page or a secondary page from a compound page
151  * - don't permit access to VMAs that don't support it, such as I/O mappings
152  */
153 int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
154         unsigned long start, int len, int write, int force,
155         struct page **pages, struct vm_area_struct **vmas)
156 {
157         struct vm_area_struct *vma;
158         unsigned long vm_flags;
159         int i;
160
161         /* calculate required read or write permissions.
162          * - if 'force' is set, we only require the "MAY" flags.
163          */
164         vm_flags  = write ? (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
165         vm_flags &= force ? (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
166
167         for (i = 0; i < len; i++) {
168                 vma = find_vma(mm, start);
169                 if (!vma)
170                         goto finish_or_fault;
171
172                 /* protect what we can, including chardevs */
173                 if (vma->vm_flags & (VM_IO | VM_PFNMAP) ||
174                     !(vm_flags & vma->vm_flags))
175                         goto finish_or_fault;
176
177                 if (pages) {
178                         pages[i] = virt_to_page(start);
179                         if (pages[i])
180                                 page_cache_get(pages[i]);
181                 }
182                 if (vmas)
183                         vmas[i] = vma;
184                 start += PAGE_SIZE;
185         }
186
187         return i;
188
189 finish_or_fault:
190         return i ? : -EFAULT;
191 }
192 EXPORT_SYMBOL(get_user_pages);
193
194 DEFINE_RWLOCK(vmlist_lock);
195 struct vm_struct *vmlist;
196
197 void vfree(const void *addr)
198 {
199         kfree(addr);
200 }
201 EXPORT_SYMBOL(vfree);
202
203 void *__vmalloc(unsigned long size, gfp_t gfp_mask, pgprot_t prot)
204 {
205         /*
206          *  You can't specify __GFP_HIGHMEM with kmalloc() since kmalloc()
207          * returns only a logical address.
208          */
209         return kmalloc(size, (gfp_mask | __GFP_COMP) & ~__GFP_HIGHMEM);
210 }
211 EXPORT_SYMBOL(__vmalloc);
212
213 void *vmalloc_user(unsigned long size)
214 {
215         void *ret;
216
217         ret = __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
218                         PAGE_KERNEL);
219         if (ret) {
220                 struct vm_area_struct *vma;
221
222                 down_write(&current->mm->mmap_sem);
223                 vma = find_vma(current->mm, (unsigned long)ret);
224                 if (vma)
225                         vma->vm_flags |= VM_USERMAP;
226                 up_write(&current->mm->mmap_sem);
227         }
228
229         return ret;
230 }
231 EXPORT_SYMBOL(vmalloc_user);
232
233 struct page *vmalloc_to_page(const void *addr)
234 {
235         return virt_to_page(addr);
236 }
237 EXPORT_SYMBOL(vmalloc_to_page);
238
239 unsigned long vmalloc_to_pfn(const void *addr)
240 {
241         return page_to_pfn(virt_to_page(addr));
242 }
243 EXPORT_SYMBOL(vmalloc_to_pfn);
244
245 long vread(char *buf, char *addr, unsigned long count)
246 {
247         memcpy(buf, addr, count);
248         return count;
249 }
250
251 long vwrite(char *buf, char *addr, unsigned long count)
252 {
253         /* Don't allow overflow */
254         if ((unsigned long) addr + count < count)
255                 count = -(unsigned long) addr;
256
257         memcpy(addr, buf, count);
258         return(count);
259 }
260
261 /*
262  *      vmalloc  -  allocate virtually continguos memory
263  *
264  *      @size:          allocation size
265  *
266  *      Allocate enough pages to cover @size from the page level
267  *      allocator and map them into continguos kernel virtual space.
268  *
269  *      For tight control over page level allocator and protection flags
270  *      use __vmalloc() instead.
271  */
272 void *vmalloc(unsigned long size)
273 {
274        return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL);
275 }
276 EXPORT_SYMBOL(vmalloc);
277
278 void *vmalloc_node(unsigned long size, int node)
279 {
280         return vmalloc(size);
281 }
282 EXPORT_SYMBOL(vmalloc_node);
283
284 /**
285  * vmalloc_32  -  allocate virtually contiguous memory (32bit addressable)
286  *      @size:          allocation size
287  *
288  *      Allocate enough 32bit PA addressable pages to cover @size from the
289  *      page level allocator and map them into continguos kernel virtual space.
290  */
291 void *vmalloc_32(unsigned long size)
292 {
293         return __vmalloc(size, GFP_KERNEL, PAGE_KERNEL);
294 }
295 EXPORT_SYMBOL(vmalloc_32);
296
297 /**
298  * vmalloc_32_user - allocate zeroed virtually contiguous 32bit memory
299  *      @size:          allocation size
300  *
301  * The resulting memory area is 32bit addressable and zeroed so it can be
302  * mapped to userspace without leaking data.
303  *
304  * VM_USERMAP is set on the corresponding VMA so that subsequent calls to
305  * remap_vmalloc_range() are permissible.
306  */
307 void *vmalloc_32_user(unsigned long size)
308 {
309         /*
310          * We'll have to sort out the ZONE_DMA bits for 64-bit,
311          * but for now this can simply use vmalloc_user() directly.
312          */
313         return vmalloc_user(size);
314 }
315 EXPORT_SYMBOL(vmalloc_32_user);
316
317 void *vmap(struct page **pages, unsigned int count, unsigned long flags, pgprot_t prot)
318 {
319         BUG();
320         return NULL;
321 }
322 EXPORT_SYMBOL(vmap);
323
324 void vunmap(const void *addr)
325 {
326         BUG();
327 }
328 EXPORT_SYMBOL(vunmap);
329
330 /*
331  * Implement a stub for vmalloc_sync_all() if the architecture chose not to
332  * have one.
333  */
334 void  __attribute__((weak)) vmalloc_sync_all(void)
335 {
336 }
337
338 int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
339                    struct page *page)
340 {
341         return -EINVAL;
342 }
343 EXPORT_SYMBOL(vm_insert_page);
344
345 /*
346  *  sys_brk() for the most part doesn't need the global kernel
347  *  lock, except when an application is doing something nasty
348  *  like trying to un-brk an area that has already been mapped
349  *  to a regular file.  in this case, the unmapping will need
350  *  to invoke file system routines that need the global lock.
351  */
352 asmlinkage unsigned long sys_brk(unsigned long brk)
353 {
354         struct mm_struct *mm = current->mm;
355
356         if (brk < mm->start_brk || brk > mm->context.end_brk)
357                 return mm->brk;
358
359         if (mm->brk == brk)
360                 return mm->brk;
361
362         /*
363          * Always allow shrinking brk
364          */
365         if (brk <= mm->brk) {
366                 mm->brk = brk;
367                 return brk;
368         }
369
370         /*
371          * Ok, looks good - let it rip.
372          */
373         return mm->brk = brk;
374 }
375
376 #ifdef DEBUG
377 static void show_process_blocks(void)
378 {
379         struct vm_list_struct *vml;
380
381         printk("Process blocks %d:", current->pid);
382
383         for (vml = &current->mm->context.vmlist; vml; vml = vml->next) {
384                 printk(" %p: %p", vml, vml->vma);
385                 if (vml->vma)
386                         printk(" (%d @%lx #%d)",
387                                kobjsize((void *) vml->vma->vm_start),
388                                vml->vma->vm_start,
389                                atomic_read(&vml->vma->vm_usage));
390                 printk(vml->next ? " ->" : ".\n");
391         }
392 }
393 #endif /* DEBUG */
394
395 /*
396  * add a VMA into a process's mm_struct in the appropriate place in the list
397  * - should be called with mm->mmap_sem held writelocked
398  */
399 static void add_vma_to_mm(struct mm_struct *mm, struct vm_list_struct *vml)
400 {
401         struct vm_list_struct **ppv;
402
403         for (ppv = &current->mm->context.vmlist; *ppv; ppv = &(*ppv)->next)
404                 if ((*ppv)->vma->vm_start > vml->vma->vm_start)
405                         break;
406
407         vml->next = *ppv;
408         *ppv = vml;
409 }
410
411 /*
412  * look up the first VMA in which addr resides, NULL if none
413  * - should be called with mm->mmap_sem at least held readlocked
414  */
415 struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
416 {
417         struct vm_list_struct *loop, *vml;
418
419         /* search the vm_start ordered list */
420         vml = NULL;
421         for (loop = mm->context.vmlist; loop; loop = loop->next) {
422                 if (loop->vma->vm_start > addr)
423                         break;
424                 vml = loop;
425         }
426
427         if (vml && vml->vma->vm_end > addr)
428                 return vml->vma;
429
430         return NULL;
431 }
432 EXPORT_SYMBOL(find_vma);
433
434 /*
435  * find a VMA
436  * - we don't extend stack VMAs under NOMMU conditions
437  */
438 struct vm_area_struct *find_extend_vma(struct mm_struct *mm, unsigned long addr)
439 {
440         return find_vma(mm, addr);
441 }
442
443 int expand_stack(struct vm_area_struct *vma, unsigned long address)
444 {
445         return -ENOMEM;
446 }
447
448 /*
449  * look up the first VMA exactly that exactly matches addr
450  * - should be called with mm->mmap_sem at least held readlocked
451  */
452 static inline struct vm_area_struct *find_vma_exact(struct mm_struct *mm,
453                                                     unsigned long addr)
454 {
455         struct vm_list_struct *vml;
456
457         /* search the vm_start ordered list */
458         for (vml = mm->context.vmlist; vml; vml = vml->next) {
459                 if (vml->vma->vm_start == addr)
460                         return vml->vma;
461                 if (vml->vma->vm_start > addr)
462                         break;
463         }
464
465         return NULL;
466 }
467
468 /*
469  * find a VMA in the global tree
470  */
471 static inline struct vm_area_struct *find_nommu_vma(unsigned long start)
472 {
473         struct vm_area_struct *vma;
474         struct rb_node *n = nommu_vma_tree.rb_node;
475
476         while (n) {
477                 vma = rb_entry(n, struct vm_area_struct, vm_rb);
478
479                 if (start < vma->vm_start)
480                         n = n->rb_left;
481                 else if (start > vma->vm_start)
482                         n = n->rb_right;
483                 else
484                         return vma;
485         }
486
487         return NULL;
488 }
489
490 /*
491  * add a VMA in the global tree
492  */
493 static void add_nommu_vma(struct vm_area_struct *vma)
494 {
495         struct vm_area_struct *pvma;
496         struct address_space *mapping;
497         struct rb_node **p = &nommu_vma_tree.rb_node;
498         struct rb_node *parent = NULL;
499
500         /* add the VMA to the mapping */
501         if (vma->vm_file) {
502                 mapping = vma->vm_file->f_mapping;
503
504                 flush_dcache_mmap_lock(mapping);
505                 vma_prio_tree_insert(vma, &mapping->i_mmap);
506                 flush_dcache_mmap_unlock(mapping);
507         }
508
509         /* add the VMA to the master list */
510         while (*p) {
511                 parent = *p;
512                 pvma = rb_entry(parent, struct vm_area_struct, vm_rb);
513
514                 if (vma->vm_start < pvma->vm_start) {
515                         p = &(*p)->rb_left;
516                 }
517                 else if (vma->vm_start > pvma->vm_start) {
518                         p = &(*p)->rb_right;
519                 }
520                 else {
521                         /* mappings are at the same address - this can only
522                          * happen for shared-mem chardevs and shared file
523                          * mappings backed by ramfs/tmpfs */
524                         BUG_ON(!(pvma->vm_flags & VM_SHARED));
525
526                         if (vma < pvma)
527                                 p = &(*p)->rb_left;
528                         else if (vma > pvma)
529                                 p = &(*p)->rb_right;
530                         else
531                                 BUG();
532                 }
533         }
534
535         rb_link_node(&vma->vm_rb, parent, p);
536         rb_insert_color(&vma->vm_rb, &nommu_vma_tree);
537 }
538
539 /*
540  * delete a VMA from the global list
541  */
542 static void delete_nommu_vma(struct vm_area_struct *vma)
543 {
544         struct address_space *mapping;
545
546         /* remove the VMA from the mapping */
547         if (vma->vm_file) {
548                 mapping = vma->vm_file->f_mapping;
549
550                 flush_dcache_mmap_lock(mapping);
551                 vma_prio_tree_remove(vma, &mapping->i_mmap);
552                 flush_dcache_mmap_unlock(mapping);
553         }
554
555         /* remove from the master list */
556         rb_erase(&vma->vm_rb, &nommu_vma_tree);
557 }
558
559 /*
560  * determine whether a mapping should be permitted and, if so, what sort of
561  * mapping we're capable of supporting
562  */
563 static int validate_mmap_request(struct file *file,
564                                  unsigned long addr,
565                                  unsigned long len,
566                                  unsigned long prot,
567                                  unsigned long flags,
568                                  unsigned long pgoff,
569                                  unsigned long *_capabilities)
570 {
571         unsigned long capabilities;
572         unsigned long reqprot = prot;
573         int ret;
574
575         /* do the simple checks first */
576         if (flags & MAP_FIXED || addr) {
577                 printk(KERN_DEBUG
578                        "%d: Can't do fixed-address/overlay mmap of RAM\n",
579                        current->pid);
580                 return -EINVAL;
581         }
582
583         if ((flags & MAP_TYPE) != MAP_PRIVATE &&
584             (flags & MAP_TYPE) != MAP_SHARED)
585                 return -EINVAL;
586
587         if (!len)
588                 return -EINVAL;
589
590         /* Careful about overflows.. */
591         len = PAGE_ALIGN(len);
592         if (!len || len > TASK_SIZE)
593                 return -ENOMEM;
594
595         /* offset overflow? */
596         if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
597                 return -EOVERFLOW;
598
599         if (file) {
600                 /* validate file mapping requests */
601                 struct address_space *mapping;
602
603                 /* files must support mmap */
604                 if (!file->f_op || !file->f_op->mmap)
605                         return -ENODEV;
606
607                 /* work out if what we've got could possibly be shared
608                  * - we support chardevs that provide their own "memory"
609                  * - we support files/blockdevs that are memory backed
610                  */
611                 mapping = file->f_mapping;
612                 if (!mapping)
613                         mapping = file->f_path.dentry->d_inode->i_mapping;
614
615                 capabilities = 0;
616                 if (mapping && mapping->backing_dev_info)
617                         capabilities = mapping->backing_dev_info->capabilities;
618
619                 if (!capabilities) {
620                         /* no explicit capabilities set, so assume some
621                          * defaults */
622                         switch (file->f_path.dentry->d_inode->i_mode & S_IFMT) {
623                         case S_IFREG:
624                         case S_IFBLK:
625                                 capabilities = BDI_CAP_MAP_COPY;
626                                 break;
627
628                         case S_IFCHR:
629                                 capabilities =
630                                         BDI_CAP_MAP_DIRECT |
631                                         BDI_CAP_READ_MAP |
632                                         BDI_CAP_WRITE_MAP;
633                                 break;
634
635                         default:
636                                 return -EINVAL;
637                         }
638                 }
639
640                 /* eliminate any capabilities that we can't support on this
641                  * device */
642                 if (!file->f_op->get_unmapped_area)
643                         capabilities &= ~BDI_CAP_MAP_DIRECT;
644                 if (!file->f_op->read)
645                         capabilities &= ~BDI_CAP_MAP_COPY;
646
647                 if (flags & MAP_SHARED) {
648                         /* do checks for writing, appending and locking */
649                         if ((prot & PROT_WRITE) &&
650                             !(file->f_mode & FMODE_WRITE))
651                                 return -EACCES;
652
653                         if (IS_APPEND(file->f_path.dentry->d_inode) &&
654                             (file->f_mode & FMODE_WRITE))
655                                 return -EACCES;
656
657                         if (locks_verify_locked(file->f_path.dentry->d_inode))
658                                 return -EAGAIN;
659
660                         if (!(capabilities & BDI_CAP_MAP_DIRECT))
661                                 return -ENODEV;
662
663                         if (((prot & PROT_READ)  && !(capabilities & BDI_CAP_READ_MAP))  ||
664                             ((prot & PROT_WRITE) && !(capabilities & BDI_CAP_WRITE_MAP)) ||
665                             ((prot & PROT_EXEC)  && !(capabilities & BDI_CAP_EXEC_MAP))
666                             ) {
667                                 printk("MAP_SHARED not completely supported on !MMU\n");
668                                 return -EINVAL;
669                         }
670
671                         /* we mustn't privatise shared mappings */
672                         capabilities &= ~BDI_CAP_MAP_COPY;
673                 }
674                 else {
675                         /* we're going to read the file into private memory we
676                          * allocate */
677                         if (!(capabilities & BDI_CAP_MAP_COPY))
678                                 return -ENODEV;
679
680                         /* we don't permit a private writable mapping to be
681                          * shared with the backing device */
682                         if (prot & PROT_WRITE)
683                                 capabilities &= ~BDI_CAP_MAP_DIRECT;
684                 }
685
686                 /* handle executable mappings and implied executable
687                  * mappings */
688                 if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) {
689                         if (prot & PROT_EXEC)
690                                 return -EPERM;
691                 }
692                 else if ((prot & PROT_READ) && !(prot & PROT_EXEC)) {
693                         /* handle implication of PROT_EXEC by PROT_READ */
694                         if (current->personality & READ_IMPLIES_EXEC) {
695                                 if (capabilities & BDI_CAP_EXEC_MAP)
696                                         prot |= PROT_EXEC;
697                         }
698                 }
699                 else if ((prot & PROT_READ) &&
700                          (prot & PROT_EXEC) &&
701                          !(capabilities & BDI_CAP_EXEC_MAP)
702                          ) {
703                         /* backing file is not executable, try to copy */
704                         capabilities &= ~BDI_CAP_MAP_DIRECT;
705                 }
706         }
707         else {
708                 /* anonymous mappings are always memory backed and can be
709                  * privately mapped
710                  */
711                 capabilities = BDI_CAP_MAP_COPY;
712
713                 /* handle PROT_EXEC implication by PROT_READ */
714                 if ((prot & PROT_READ) &&
715                     (current->personality & READ_IMPLIES_EXEC))
716                         prot |= PROT_EXEC;
717         }
718
719         /* allow the security API to have its say */
720         ret = security_file_mmap(file, reqprot, prot, flags, addr, 0);
721         if (ret < 0)
722                 return ret;
723
724         /* looks okay */
725         *_capabilities = capabilities;
726         return 0;
727 }
728
729 /*
730  * we've determined that we can make the mapping, now translate what we
731  * now know into VMA flags
732  */
733 static unsigned long determine_vm_flags(struct file *file,
734                                         unsigned long prot,
735                                         unsigned long flags,
736                                         unsigned long capabilities)
737 {
738         unsigned long vm_flags;
739
740         vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags);
741         vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
742         /* vm_flags |= mm->def_flags; */
743
744         if (!(capabilities & BDI_CAP_MAP_DIRECT)) {
745                 /* attempt to share read-only copies of mapped file chunks */
746                 if (file && !(prot & PROT_WRITE))
747                         vm_flags |= VM_MAYSHARE;
748         }
749         else {
750                 /* overlay a shareable mapping on the backing device or inode
751                  * if possible - used for chardevs, ramfs/tmpfs/shmfs and
752                  * romfs/cramfs */
753                 if (flags & MAP_SHARED)
754                         vm_flags |= VM_MAYSHARE | VM_SHARED;
755                 else if ((((vm_flags & capabilities) ^ vm_flags) & BDI_CAP_VMFLAGS) == 0)
756                         vm_flags |= VM_MAYSHARE;
757         }
758
759         /* refuse to let anyone share private mappings with this process if
760          * it's being traced - otherwise breakpoints set in it may interfere
761          * with another untraced process
762          */
763         if ((flags & MAP_PRIVATE) && (current->ptrace & PT_PTRACED))
764                 vm_flags &= ~VM_MAYSHARE;
765
766         return vm_flags;
767 }
768
769 /*
770  * set up a shared mapping on a file
771  */
772 static int do_mmap_shared_file(struct vm_area_struct *vma, unsigned long len)
773 {
774         int ret;
775
776         ret = vma->vm_file->f_op->mmap(vma->vm_file, vma);
777         if (ret != -ENOSYS)
778                 return ret;
779
780         /* getting an ENOSYS error indicates that direct mmap isn't
781          * possible (as opposed to tried but failed) so we'll fall
782          * through to making a private copy of the data and mapping
783          * that if we can */
784         return -ENODEV;
785 }
786
787 /*
788  * set up a private mapping or an anonymous shared mapping
789  */
790 static int do_mmap_private(struct vm_area_struct *vma, unsigned long len)
791 {
792         void *base;
793         int ret;
794
795         /* invoke the file's mapping function so that it can keep track of
796          * shared mappings on devices or memory
797          * - VM_MAYSHARE will be set if it may attempt to share
798          */
799         if (vma->vm_file) {
800                 ret = vma->vm_file->f_op->mmap(vma->vm_file, vma);
801                 if (ret != -ENOSYS) {
802                         /* shouldn't return success if we're not sharing */
803                         BUG_ON(ret == 0 && !(vma->vm_flags & VM_MAYSHARE));
804                         return ret; /* success or a real error */
805                 }
806
807                 /* getting an ENOSYS error indicates that direct mmap isn't
808                  * possible (as opposed to tried but failed) so we'll try to
809                  * make a private copy of the data and map that instead */
810         }
811
812         /* allocate some memory to hold the mapping
813          * - note that this may not return a page-aligned address if the object
814          *   we're allocating is smaller than a page
815          */
816         base = kmalloc(len, GFP_KERNEL|__GFP_COMP);
817         if (!base)
818                 goto enomem;
819
820         vma->vm_start = (unsigned long) base;
821         vma->vm_end = vma->vm_start + len;
822         vma->vm_flags |= VM_MAPPED_COPY;
823
824 #ifdef WARN_ON_SLACK
825         if (len + WARN_ON_SLACK <= kobjsize(result))
826                 printk("Allocation of %lu bytes from process %d has %lu bytes of slack\n",
827                        len, current->pid, kobjsize(result) - len);
828 #endif
829
830         if (vma->vm_file) {
831                 /* read the contents of a file into the copy */
832                 mm_segment_t old_fs;
833                 loff_t fpos;
834
835                 fpos = vma->vm_pgoff;
836                 fpos <<= PAGE_SHIFT;
837
838                 old_fs = get_fs();
839                 set_fs(KERNEL_DS);
840                 ret = vma->vm_file->f_op->read(vma->vm_file, base, len, &fpos);
841                 set_fs(old_fs);
842
843                 if (ret < 0)
844                         goto error_free;
845
846                 /* clear the last little bit */
847                 if (ret < len)
848                         memset(base + ret, 0, len - ret);
849
850         } else {
851                 /* if it's an anonymous mapping, then just clear it */
852                 memset(base, 0, len);
853         }
854
855         return 0;
856
857 error_free:
858         kfree(base);
859         vma->vm_start = 0;
860         return ret;
861
862 enomem:
863         printk("Allocation of length %lu from process %d failed\n",
864                len, current->pid);
865         show_free_areas();
866         return -ENOMEM;
867 }
868
869 /*
870  * handle mapping creation for uClinux
871  */
872 unsigned long do_mmap_pgoff(struct file *file,
873                             unsigned long addr,
874                             unsigned long len,
875                             unsigned long prot,
876                             unsigned long flags,
877                             unsigned long pgoff)
878 {
879         struct vm_list_struct *vml = NULL;
880         struct vm_area_struct *vma = NULL;
881         struct rb_node *rb;
882         unsigned long capabilities, vm_flags;
883         void *result;
884         int ret;
885
886         if (!(flags & MAP_FIXED))
887                 addr = round_hint_to_min(addr);
888
889         /* decide whether we should attempt the mapping, and if so what sort of
890          * mapping */
891         ret = validate_mmap_request(file, addr, len, prot, flags, pgoff,
892                                     &capabilities);
893         if (ret < 0)
894                 return ret;
895
896         /* we've determined that we can make the mapping, now translate what we
897          * now know into VMA flags */
898         vm_flags = determine_vm_flags(file, prot, flags, capabilities);
899
900         /* we're going to need to record the mapping if it works */
901         vml = kzalloc(sizeof(struct vm_list_struct), GFP_KERNEL);
902         if (!vml)
903                 goto error_getting_vml;
904
905         down_write(&nommu_vma_sem);
906
907         /* if we want to share, we need to check for VMAs created by other
908          * mmap() calls that overlap with our proposed mapping
909          * - we can only share with an exact match on most regular files
910          * - shared mappings on character devices and memory backed files are
911          *   permitted to overlap inexactly as far as we are concerned for in
912          *   these cases, sharing is handled in the driver or filesystem rather
913          *   than here
914          */
915         if (vm_flags & VM_MAYSHARE) {
916                 unsigned long pglen = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
917                 unsigned long vmpglen;
918
919                 /* suppress VMA sharing for shared regions */
920                 if (vm_flags & VM_SHARED &&
921                     capabilities & BDI_CAP_MAP_DIRECT)
922                         goto dont_share_VMAs;
923
924                 for (rb = rb_first(&nommu_vma_tree); rb; rb = rb_next(rb)) {
925                         vma = rb_entry(rb, struct vm_area_struct, vm_rb);
926
927                         if (!(vma->vm_flags & VM_MAYSHARE))
928                                 continue;
929
930                         /* search for overlapping mappings on the same file */
931                         if (vma->vm_file->f_path.dentry->d_inode != file->f_path.dentry->d_inode)
932                                 continue;
933
934                         if (vma->vm_pgoff >= pgoff + pglen)
935                                 continue;
936
937                         vmpglen = vma->vm_end - vma->vm_start + PAGE_SIZE - 1;
938                         vmpglen >>= PAGE_SHIFT;
939                         if (pgoff >= vma->vm_pgoff + vmpglen)
940                                 continue;
941
942                         /* handle inexactly overlapping matches between mappings */
943                         if (vma->vm_pgoff != pgoff || vmpglen != pglen) {
944                                 if (!(capabilities & BDI_CAP_MAP_DIRECT))
945                                         goto sharing_violation;
946                                 continue;
947                         }
948
949                         /* we've found a VMA we can share */
950                         atomic_inc(&vma->vm_usage);
951
952                         vml->vma = vma;
953                         result = (void *) vma->vm_start;
954                         goto shared;
955                 }
956
957         dont_share_VMAs:
958                 vma = NULL;
959
960                 /* obtain the address at which to make a shared mapping
961                  * - this is the hook for quasi-memory character devices to
962                  *   tell us the location of a shared mapping
963                  */
964                 if (file && file->f_op->get_unmapped_area) {
965                         addr = file->f_op->get_unmapped_area(file, addr, len,
966                                                              pgoff, flags);
967                         if (IS_ERR((void *) addr)) {
968                                 ret = addr;
969                                 if (ret != (unsigned long) -ENOSYS)
970                                         goto error;
971
972                                 /* the driver refused to tell us where to site
973                                  * the mapping so we'll have to attempt to copy
974                                  * it */
975                                 ret = (unsigned long) -ENODEV;
976                                 if (!(capabilities & BDI_CAP_MAP_COPY))
977                                         goto error;
978
979                                 capabilities &= ~BDI_CAP_MAP_DIRECT;
980                         }
981                 }
982         }
983
984         /* we're going to need a VMA struct as well */
985         vma = kzalloc(sizeof(struct vm_area_struct), GFP_KERNEL);
986         if (!vma)
987                 goto error_getting_vma;
988
989         INIT_LIST_HEAD(&vma->anon_vma_node);
990         atomic_set(&vma->vm_usage, 1);
991         if (file) {
992                 get_file(file);
993                 if (vm_flags & VM_EXECUTABLE) {
994                         added_exe_file_vma(current->mm);
995                         vma->vm_mm = current->mm;
996                 }
997         }
998         vma->vm_file    = file;
999         vma->vm_flags   = vm_flags;
1000         vma->vm_start   = addr;
1001         vma->vm_end     = addr + len;
1002         vma->vm_pgoff   = pgoff;
1003
1004         vml->vma = vma;
1005
1006         /* set up the mapping */
1007         if (file && vma->vm_flags & VM_SHARED)
1008                 ret = do_mmap_shared_file(vma, len);
1009         else
1010                 ret = do_mmap_private(vma, len);
1011         if (ret < 0)
1012                 goto error;
1013
1014         /* okay... we have a mapping; now we have to register it */
1015         result = (void *) vma->vm_start;
1016
1017         if (vma->vm_flags & VM_MAPPED_COPY) {
1018                 realalloc += kobjsize(result);
1019                 askedalloc += len;
1020         }
1021
1022         realalloc += kobjsize(vma);
1023         askedalloc += sizeof(*vma);
1024
1025         current->mm->total_vm += len >> PAGE_SHIFT;
1026
1027         add_nommu_vma(vma);
1028
1029  shared:
1030         realalloc += kobjsize(vml);
1031         askedalloc += sizeof(*vml);
1032
1033         add_vma_to_mm(current->mm, vml);
1034
1035         up_write(&nommu_vma_sem);
1036
1037         if (prot & PROT_EXEC)
1038                 flush_icache_range((unsigned long) result,
1039                                    (unsigned long) result + len);
1040
1041 #ifdef DEBUG
1042         printk("do_mmap:\n");
1043         show_process_blocks();
1044 #endif
1045
1046         return (unsigned long) result;
1047
1048  error:
1049         up_write(&nommu_vma_sem);
1050         kfree(vml);
1051         if (vma) {
1052                 if (vma->vm_file) {
1053                         fput(vma->vm_file);
1054                         if (vma->vm_flags & VM_EXECUTABLE)
1055                                 removed_exe_file_vma(vma->vm_mm);
1056                 }
1057                 kfree(vma);
1058         }
1059         return ret;
1060
1061  sharing_violation:
1062         up_write(&nommu_vma_sem);
1063         printk("Attempt to share mismatched mappings\n");
1064         kfree(vml);
1065         return -EINVAL;
1066
1067  error_getting_vma:
1068         up_write(&nommu_vma_sem);
1069         kfree(vml);
1070         printk("Allocation of vma for %lu byte allocation from process %d failed\n",
1071                len, current->pid);
1072         show_free_areas();
1073         return -ENOMEM;
1074
1075  error_getting_vml:
1076         printk("Allocation of vml for %lu byte allocation from process %d failed\n",
1077                len, current->pid);
1078         show_free_areas();
1079         return -ENOMEM;
1080 }
1081 EXPORT_SYMBOL(do_mmap_pgoff);
1082
1083 /*
1084  * handle mapping disposal for uClinux
1085  */
1086 static void put_vma(struct mm_struct *mm, struct vm_area_struct *vma)
1087 {
1088         if (vma) {
1089                 down_write(&nommu_vma_sem);
1090
1091                 if (atomic_dec_and_test(&vma->vm_usage)) {
1092                         delete_nommu_vma(vma);
1093
1094                         if (vma->vm_ops && vma->vm_ops->close)
1095                                 vma->vm_ops->close(vma);
1096
1097                         /* IO memory and memory shared directly out of the pagecache from
1098                          * ramfs/tmpfs mustn't be released here */
1099                         if (vma->vm_flags & VM_MAPPED_COPY) {
1100                                 realalloc -= kobjsize((void *) vma->vm_start);
1101                                 askedalloc -= vma->vm_end - vma->vm_start;
1102                                 kfree((void *) vma->vm_start);
1103                         }
1104
1105                         realalloc -= kobjsize(vma);
1106                         askedalloc -= sizeof(*vma);
1107
1108                         if (vma->vm_file) {
1109                                 fput(vma->vm_file);
1110                                 if (vma->vm_flags & VM_EXECUTABLE)
1111                                         removed_exe_file_vma(mm);
1112                         }
1113                         kfree(vma);
1114                 }
1115
1116                 up_write(&nommu_vma_sem);
1117         }
1118 }
1119
1120 /*
1121  * release a mapping
1122  * - under NOMMU conditions the parameters must match exactly to the mapping to
1123  *   be removed
1124  */
1125 int do_munmap(struct mm_struct *mm, unsigned long addr, size_t len)
1126 {
1127         struct vm_list_struct *vml, **parent;
1128         unsigned long end = addr + len;
1129
1130 #ifdef DEBUG
1131         printk("do_munmap:\n");
1132 #endif
1133
1134         for (parent = &mm->context.vmlist; *parent; parent = &(*parent)->next) {
1135                 if ((*parent)->vma->vm_start > addr)
1136                         break;
1137                 if ((*parent)->vma->vm_start == addr &&
1138                     ((len == 0) || ((*parent)->vma->vm_end == end)))
1139                         goto found;
1140         }
1141
1142         printk("munmap of non-mmaped memory by process %d (%s): %p\n",
1143                current->pid, current->comm, (void *) addr);
1144         return -EINVAL;
1145
1146  found:
1147         vml = *parent;
1148
1149         put_vma(mm, vml->vma);
1150
1151         *parent = vml->next;
1152         realalloc -= kobjsize(vml);
1153         askedalloc -= sizeof(*vml);
1154         kfree(vml);
1155
1156         update_hiwater_vm(mm);
1157         mm->total_vm -= len >> PAGE_SHIFT;
1158
1159 #ifdef DEBUG
1160         show_process_blocks();
1161 #endif
1162
1163         return 0;
1164 }
1165 EXPORT_SYMBOL(do_munmap);
1166
1167 asmlinkage long sys_munmap(unsigned long addr, size_t len)
1168 {
1169         int ret;
1170         struct mm_struct *mm = current->mm;
1171
1172         down_write(&mm->mmap_sem);
1173         ret = do_munmap(mm, addr, len);
1174         up_write(&mm->mmap_sem);
1175         return ret;
1176 }
1177
1178 /*
1179  * Release all mappings
1180  */
1181 void exit_mmap(struct mm_struct * mm)
1182 {
1183         struct vm_list_struct *tmp;
1184
1185         if (mm) {
1186 #ifdef DEBUG
1187                 printk("Exit_mmap:\n");
1188 #endif
1189
1190                 mm->total_vm = 0;
1191
1192                 while ((tmp = mm->context.vmlist)) {
1193                         mm->context.vmlist = tmp->next;
1194                         put_vma(mm, tmp->vma);
1195
1196                         realalloc -= kobjsize(tmp);
1197                         askedalloc -= sizeof(*tmp);
1198                         kfree(tmp);
1199                 }
1200
1201 #ifdef DEBUG
1202                 show_process_blocks();
1203 #endif
1204         }
1205 }
1206
1207 unsigned long do_brk(unsigned long addr, unsigned long len)
1208 {
1209         return -ENOMEM;
1210 }
1211
1212 /*
1213  * expand (or shrink) an existing mapping, potentially moving it at the same
1214  * time (controlled by the MREMAP_MAYMOVE flag and available VM space)
1215  *
1216  * under NOMMU conditions, we only permit changing a mapping's size, and only
1217  * as long as it stays within the hole allocated by the kmalloc() call in
1218  * do_mmap_pgoff() and the block is not shareable
1219  *
1220  * MREMAP_FIXED is not supported under NOMMU conditions
1221  */
1222 unsigned long do_mremap(unsigned long addr,
1223                         unsigned long old_len, unsigned long new_len,
1224                         unsigned long flags, unsigned long new_addr)
1225 {
1226         struct vm_area_struct *vma;
1227
1228         /* insanity checks first */
1229         if (new_len == 0)
1230                 return (unsigned long) -EINVAL;
1231
1232         if (flags & MREMAP_FIXED && new_addr != addr)
1233                 return (unsigned long) -EINVAL;
1234
1235         vma = find_vma_exact(current->mm, addr);
1236         if (!vma)
1237                 return (unsigned long) -EINVAL;
1238
1239         if (vma->vm_end != vma->vm_start + old_len)
1240                 return (unsigned long) -EFAULT;
1241
1242         if (vma->vm_flags & VM_MAYSHARE)
1243                 return (unsigned long) -EPERM;
1244
1245         if (new_len > kobjsize((void *) addr))
1246                 return (unsigned long) -ENOMEM;
1247
1248         /* all checks complete - do it */
1249         vma->vm_end = vma->vm_start + new_len;
1250
1251         askedalloc -= old_len;
1252         askedalloc += new_len;
1253
1254         return vma->vm_start;
1255 }
1256 EXPORT_SYMBOL(do_mremap);
1257
1258 asmlinkage unsigned long sys_mremap(unsigned long addr,
1259         unsigned long old_len, unsigned long new_len,
1260         unsigned long flags, unsigned long new_addr)
1261 {
1262         unsigned long ret;
1263
1264         down_write(&current->mm->mmap_sem);
1265         ret = do_mremap(addr, old_len, new_len, flags, new_addr);
1266         up_write(&current->mm->mmap_sem);
1267         return ret;
1268 }
1269
1270 struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
1271                         unsigned int foll_flags)
1272 {
1273         return NULL;
1274 }
1275
1276 int remap_pfn_range(struct vm_area_struct *vma, unsigned long from,
1277                 unsigned long to, unsigned long size, pgprot_t prot)
1278 {
1279         vma->vm_start = vma->vm_pgoff << PAGE_SHIFT;
1280         return 0;
1281 }
1282 EXPORT_SYMBOL(remap_pfn_range);
1283
1284 int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
1285                         unsigned long pgoff)
1286 {
1287         unsigned int size = vma->vm_end - vma->vm_start;
1288
1289         if (!(vma->vm_flags & VM_USERMAP))
1290                 return -EINVAL;
1291
1292         vma->vm_start = (unsigned long)(addr + (pgoff << PAGE_SHIFT));
1293         vma->vm_end = vma->vm_start + size;
1294
1295         return 0;
1296 }
1297 EXPORT_SYMBOL(remap_vmalloc_range);
1298
1299 void swap_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
1300 {
1301 }
1302
1303 unsigned long arch_get_unmapped_area(struct file *file, unsigned long addr,
1304         unsigned long len, unsigned long pgoff, unsigned long flags)
1305 {
1306         return -ENOMEM;
1307 }
1308
1309 void arch_unmap_area(struct mm_struct *mm, unsigned long addr)
1310 {
1311 }
1312
1313 void unmap_mapping_range(struct address_space *mapping,
1314                          loff_t const holebegin, loff_t const holelen,
1315                          int even_cows)
1316 {
1317 }
1318 EXPORT_SYMBOL(unmap_mapping_range);
1319
1320 /*
1321  * ask for an unmapped area at which to create a mapping on a file
1322  */
1323 unsigned long get_unmapped_area(struct file *file, unsigned long addr,
1324                                 unsigned long len, unsigned long pgoff,
1325                                 unsigned long flags)
1326 {
1327         unsigned long (*get_area)(struct file *, unsigned long, unsigned long,
1328                                   unsigned long, unsigned long);
1329
1330         get_area = current->mm->get_unmapped_area;
1331         if (file && file->f_op && file->f_op->get_unmapped_area)
1332                 get_area = file->f_op->get_unmapped_area;
1333
1334         if (!get_area)
1335                 return -ENOSYS;
1336
1337         return get_area(file, addr, len, pgoff, flags);
1338 }
1339 EXPORT_SYMBOL(get_unmapped_area);
1340
1341 /*
1342  * Check that a process has enough memory to allocate a new virtual
1343  * mapping. 0 means there is enough memory for the allocation to
1344  * succeed and -ENOMEM implies there is not.
1345  *
1346  * We currently support three overcommit policies, which are set via the
1347  * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-accounting
1348  *
1349  * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
1350  * Additional code 2002 Jul 20 by Robert Love.
1351  *
1352  * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
1353  *
1354  * Note this is a helper function intended to be used by LSMs which
1355  * wish to use this logic.
1356  */
1357 int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
1358 {
1359         unsigned long free, allowed;
1360
1361         vm_acct_memory(pages);
1362
1363         /*
1364          * Sometimes we want to use more memory than we have
1365          */
1366         if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
1367                 return 0;
1368
1369         if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
1370                 unsigned long n;
1371
1372                 free = global_page_state(NR_FILE_PAGES);
1373                 free += nr_swap_pages;
1374
1375                 /*
1376                  * Any slabs which are created with the
1377                  * SLAB_RECLAIM_ACCOUNT flag claim to have contents
1378                  * which are reclaimable, under pressure.  The dentry
1379                  * cache and most inode caches should fall into this
1380                  */
1381                 free += global_page_state(NR_SLAB_RECLAIMABLE);
1382
1383                 /*
1384                  * Leave the last 3% for root
1385                  */
1386                 if (!cap_sys_admin)
1387                         free -= free / 32;
1388
1389                 if (free > pages)
1390                         return 0;
1391
1392                 /*
1393                  * nr_free_pages() is very expensive on large systems,
1394                  * only call if we're about to fail.
1395                  */
1396                 n = nr_free_pages();
1397
1398                 /*
1399                  * Leave reserved pages. The pages are not for anonymous pages.
1400                  */
1401                 if (n <= totalreserve_pages)
1402                         goto error;
1403                 else
1404                         n -= totalreserve_pages;
1405
1406                 /*
1407                  * Leave the last 3% for root
1408                  */
1409                 if (!cap_sys_admin)
1410                         n -= n / 32;
1411                 free += n;
1412
1413                 if (free > pages)
1414                         return 0;
1415
1416                 goto error;
1417         }
1418
1419         allowed = totalram_pages * sysctl_overcommit_ratio / 100;
1420         /*
1421          * Leave the last 3% for root
1422          */
1423         if (!cap_sys_admin)
1424                 allowed -= allowed / 32;
1425         allowed += total_swap_pages;
1426
1427         /* Don't let a single process grow too big:
1428            leave 3% of the size of this process for other processes */
1429         allowed -= current->mm->total_vm / 32;
1430
1431         /*
1432          * cast `allowed' as a signed long because vm_committed_space
1433          * sometimes has a negative value
1434          */
1435         if (atomic_long_read(&vm_committed_space) < (long)allowed)
1436                 return 0;
1437 error:
1438         vm_unacct_memory(pages);
1439
1440         return -ENOMEM;
1441 }
1442
1443 int in_gate_area_no_task(unsigned long addr)
1444 {
1445         return 0;
1446 }
1447
1448 int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1449 {
1450         BUG();
1451         return 0;
1452 }
1453 EXPORT_SYMBOL(filemap_fault);
1454
1455 /*
1456  * Access another process' address space.
1457  * - source/target buffer must be kernel space
1458  */
1459 int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
1460 {
1461         struct vm_area_struct *vma;
1462         struct mm_struct *mm;
1463
1464         if (addr + len < addr)
1465                 return 0;
1466
1467         mm = get_task_mm(tsk);
1468         if (!mm)
1469                 return 0;
1470
1471         down_read(&mm->mmap_sem);
1472
1473         /* the access must start within one of the target process's mappings */
1474         vma = find_vma(mm, addr);
1475         if (vma) {
1476                 /* don't overrun this mapping */
1477                 if (addr + len >= vma->vm_end)
1478                         len = vma->vm_end - addr;
1479
1480                 /* only read or write mappings where it is permitted */
1481                 if (write && vma->vm_flags & VM_MAYWRITE)
1482                         len -= copy_to_user((void *) addr, buf, len);
1483                 else if (!write && vma->vm_flags & VM_MAYREAD)
1484                         len -= copy_from_user(buf, (void *) addr, len);
1485                 else
1486                         len = 0;
1487         } else {
1488                 len = 0;
1489         }
1490
1491         up_read(&mm->mmap_sem);
1492         mmput(mm);
1493         return len;
1494 }