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