Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc-2.6
[linux-2.6.git] / drivers / char / mem.c
1 /*
2  *  linux/drivers/char/mem.c
3  *
4  *  Copyright (C) 1991, 1992  Linus Torvalds
5  *
6  *  Added devfs support.
7  *    Jan-11-1998, C. Scott Ananian <cananian@alumni.princeton.edu>
8  *  Shared /dev/zero mmapping support, Feb 2000, Kanoj Sarcar <kanoj@sgi.com>
9  */
10
11 #include <linux/mm.h>
12 #include <linux/miscdevice.h>
13 #include <linux/slab.h>
14 #include <linux/vmalloc.h>
15 #include <linux/mman.h>
16 #include <linux/random.h>
17 #include <linux/init.h>
18 #include <linux/raw.h>
19 #include <linux/tty.h>
20 #include <linux/capability.h>
21 #include <linux/ptrace.h>
22 #include <linux/device.h>
23 #include <linux/highmem.h>
24 #include <linux/crash_dump.h>
25 #include <linux/backing-dev.h>
26 #include <linux/bootmem.h>
27 #include <linux/splice.h>
28 #include <linux/pfn.h>
29
30 #include <asm/uaccess.h>
31 #include <asm/io.h>
32
33 #ifdef CONFIG_IA64
34 # include <linux/efi.h>
35 #endif
36
37 static inline unsigned long size_inside_page(unsigned long start,
38                                              unsigned long size)
39 {
40         unsigned long sz;
41
42         sz = PAGE_SIZE - (start & (PAGE_SIZE - 1));
43
44         return min(sz, size);
45 }
46
47 #ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE
48 static inline int valid_phys_addr_range(unsigned long addr, size_t count)
49 {
50         if (addr + count > __pa(high_memory))
51                 return 0;
52
53         return 1;
54 }
55
56 static inline int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
57 {
58         return 1;
59 }
60 #endif
61
62 #ifdef CONFIG_STRICT_DEVMEM
63 static inline int range_is_allowed(unsigned long pfn, unsigned long size)
64 {
65         u64 from = ((u64)pfn) << PAGE_SHIFT;
66         u64 to = from + size;
67         u64 cursor = from;
68
69         while (cursor < to) {
70                 if (!devmem_is_allowed(pfn)) {
71                         printk(KERN_INFO
72                 "Program %s tried to access /dev/mem between %Lx->%Lx.\n",
73                                 current->comm, from, to);
74                         return 0;
75                 }
76                 cursor += PAGE_SIZE;
77                 pfn++;
78         }
79         return 1;
80 }
81 #else
82 static inline int range_is_allowed(unsigned long pfn, unsigned long size)
83 {
84         return 1;
85 }
86 #endif
87
88 void __weak unxlate_dev_mem_ptr(unsigned long phys, void *addr)
89 {
90 }
91
92 /*
93  * This funcion reads the *physical* memory. The f_pos points directly to the
94  * memory location.
95  */
96 static ssize_t read_mem(struct file *file, char __user *buf,
97                         size_t count, loff_t *ppos)
98 {
99         unsigned long p = *ppos;
100         ssize_t read, sz;
101         char *ptr;
102
103         if (!valid_phys_addr_range(p, count))
104                 return -EFAULT;
105         read = 0;
106 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
107         /* we don't have page 0 mapped on sparc and m68k.. */
108         if (p < PAGE_SIZE) {
109                 sz = size_inside_page(p, count);
110                 if (sz > 0) {
111                         if (clear_user(buf, sz))
112                                 return -EFAULT;
113                         buf += sz;
114                         p += sz;
115                         count -= sz;
116                         read += sz;
117                 }
118         }
119 #endif
120
121         while (count > 0) {
122                 unsigned long remaining;
123
124                 sz = size_inside_page(p, count);
125
126                 if (!range_is_allowed(p >> PAGE_SHIFT, count))
127                         return -EPERM;
128
129                 /*
130                  * On ia64 if a page has been mapped somewhere as uncached, then
131                  * it must also be accessed uncached by the kernel or data
132                  * corruption may occur.
133                  */
134                 ptr = xlate_dev_mem_ptr(p);
135                 if (!ptr)
136                         return -EFAULT;
137
138                 remaining = copy_to_user(buf, ptr, sz);
139                 unxlate_dev_mem_ptr(p, ptr);
140                 if (remaining)
141                         return -EFAULT;
142
143                 buf += sz;
144                 p += sz;
145                 count -= sz;
146                 read += sz;
147         }
148
149         *ppos += read;
150         return read;
151 }
152
153 static ssize_t write_mem(struct file *file, const char __user *buf,
154                          size_t count, loff_t *ppos)
155 {
156         unsigned long p = *ppos;
157         ssize_t written, sz;
158         unsigned long copied;
159         void *ptr;
160
161         if (!valid_phys_addr_range(p, count))
162                 return -EFAULT;
163
164         written = 0;
165
166 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
167         /* we don't have page 0 mapped on sparc and m68k.. */
168         if (p < PAGE_SIZE) {
169                 sz = size_inside_page(p, count);
170                 /* Hmm. Do something? */
171                 buf += sz;
172                 p += sz;
173                 count -= sz;
174                 written += sz;
175         }
176 #endif
177
178         while (count > 0) {
179                 sz = size_inside_page(p, count);
180
181                 if (!range_is_allowed(p >> PAGE_SHIFT, sz))
182                         return -EPERM;
183
184                 /*
185                  * On ia64 if a page has been mapped somewhere as uncached, then
186                  * it must also be accessed uncached by the kernel or data
187                  * corruption may occur.
188                  */
189                 ptr = xlate_dev_mem_ptr(p);
190                 if (!ptr) {
191                         if (written)
192                                 break;
193                         return -EFAULT;
194                 }
195
196                 copied = copy_from_user(ptr, buf, sz);
197                 unxlate_dev_mem_ptr(p, ptr);
198                 if (copied) {
199                         written += sz - copied;
200                         if (written)
201                                 break;
202                         return -EFAULT;
203                 }
204
205                 buf += sz;
206                 p += sz;
207                 count -= sz;
208                 written += sz;
209         }
210
211         *ppos += written;
212         return written;
213 }
214
215 int __weak phys_mem_access_prot_allowed(struct file *file,
216         unsigned long pfn, unsigned long size, pgprot_t *vma_prot)
217 {
218         return 1;
219 }
220
221 #ifndef __HAVE_PHYS_MEM_ACCESS_PROT
222
223 /*
224  * Architectures vary in how they handle caching for addresses
225  * outside of main memory.
226  *
227  */
228 static int uncached_access(struct file *file, unsigned long addr)
229 {
230 #if defined(CONFIG_IA64)
231         /*
232          * On ia64, we ignore O_DSYNC because we cannot tolerate memory
233          * attribute aliases.
234          */
235         return !(efi_mem_attributes(addr) & EFI_MEMORY_WB);
236 #elif defined(CONFIG_MIPS)
237         {
238                 extern int __uncached_access(struct file *file,
239                                              unsigned long addr);
240
241                 return __uncached_access(file, addr);
242         }
243 #else
244         /*
245          * Accessing memory above the top the kernel knows about or through a
246          * file pointer
247          * that was marked O_DSYNC will be done non-cached.
248          */
249         if (file->f_flags & O_DSYNC)
250                 return 1;
251         return addr >= __pa(high_memory);
252 #endif
253 }
254
255 static pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
256                                      unsigned long size, pgprot_t vma_prot)
257 {
258 #ifdef pgprot_noncached
259         unsigned long offset = pfn << PAGE_SHIFT;
260
261         if (uncached_access(file, offset))
262                 return pgprot_noncached(vma_prot);
263 #endif
264         return vma_prot;
265 }
266 #endif
267
268 #ifndef CONFIG_MMU
269 static unsigned long get_unmapped_area_mem(struct file *file,
270                                            unsigned long addr,
271                                            unsigned long len,
272                                            unsigned long pgoff,
273                                            unsigned long flags)
274 {
275         if (!valid_mmap_phys_addr_range(pgoff, len))
276                 return (unsigned long) -EINVAL;
277         return pgoff << PAGE_SHIFT;
278 }
279
280 /* can't do an in-place private mapping if there's no MMU */
281 static inline int private_mapping_ok(struct vm_area_struct *vma)
282 {
283         return vma->vm_flags & VM_MAYSHARE;
284 }
285 #else
286 #define get_unmapped_area_mem   NULL
287
288 static inline int private_mapping_ok(struct vm_area_struct *vma)
289 {
290         return 1;
291 }
292 #endif
293
294 static const struct vm_operations_struct mmap_mem_ops = {
295 #ifdef CONFIG_HAVE_IOREMAP_PROT
296         .access = generic_access_phys
297 #endif
298 };
299
300 static int mmap_mem(struct file *file, struct vm_area_struct *vma)
301 {
302         size_t size = vma->vm_end - vma->vm_start;
303
304         if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))
305                 return -EINVAL;
306
307         if (!private_mapping_ok(vma))
308                 return -ENOSYS;
309
310         if (!range_is_allowed(vma->vm_pgoff, size))
311                 return -EPERM;
312
313         if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size,
314                                                 &vma->vm_page_prot))
315                 return -EINVAL;
316
317         vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,
318                                                  size,
319                                                  vma->vm_page_prot);
320
321         vma->vm_ops = &mmap_mem_ops;
322
323         /* Remap-pfn-range will mark the range VM_IO and VM_RESERVED */
324         if (remap_pfn_range(vma,
325                             vma->vm_start,
326                             vma->vm_pgoff,
327                             size,
328                             vma->vm_page_prot)) {
329                 return -EAGAIN;
330         }
331         return 0;
332 }
333
334 #ifdef CONFIG_DEVKMEM
335 static int mmap_kmem(struct file *file, struct vm_area_struct *vma)
336 {
337         unsigned long pfn;
338
339         /* Turn a kernel-virtual address into a physical page frame */
340         pfn = __pa((u64)vma->vm_pgoff << PAGE_SHIFT) >> PAGE_SHIFT;
341
342         /*
343          * RED-PEN: on some architectures there is more mapped memory than
344          * available in mem_map which pfn_valid checks for. Perhaps should add a
345          * new macro here.
346          *
347          * RED-PEN: vmalloc is not supported right now.
348          */
349         if (!pfn_valid(pfn))
350                 return -EIO;
351
352         vma->vm_pgoff = pfn;
353         return mmap_mem(file, vma);
354 }
355 #endif
356
357 #ifdef CONFIG_CRASH_DUMP
358 /*
359  * Read memory corresponding to the old kernel.
360  */
361 static ssize_t read_oldmem(struct file *file, char __user *buf,
362                                 size_t count, loff_t *ppos)
363 {
364         unsigned long pfn, offset;
365         size_t read = 0, csize;
366         int rc = 0;
367
368         while (count) {
369                 pfn = *ppos / PAGE_SIZE;
370                 if (pfn > saved_max_pfn)
371                         return read;
372
373                 offset = (unsigned long)(*ppos % PAGE_SIZE);
374                 if (count > PAGE_SIZE - offset)
375                         csize = PAGE_SIZE - offset;
376                 else
377                         csize = count;
378
379                 rc = copy_oldmem_page(pfn, buf, csize, offset, 1);
380                 if (rc < 0)
381                         return rc;
382                 buf += csize;
383                 *ppos += csize;
384                 read += csize;
385                 count -= csize;
386         }
387         return read;
388 }
389 #endif
390
391 #ifdef CONFIG_DEVKMEM
392 /*
393  * This function reads the *virtual* memory as seen by the kernel.
394  */
395 static ssize_t read_kmem(struct file *file, char __user *buf,
396                          size_t count, loff_t *ppos)
397 {
398         unsigned long p = *ppos;
399         ssize_t low_count, read, sz;
400         char * kbuf; /* k-addr because vread() takes vmlist_lock rwlock */
401         int err = 0;
402
403         read = 0;
404         if (p < (unsigned long) high_memory) {
405                 low_count = count;
406                 if (count > (unsigned long)high_memory - p)
407                         low_count = (unsigned long)high_memory - p;
408
409 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
410                 /* we don't have page 0 mapped on sparc and m68k.. */
411                 if (p < PAGE_SIZE && low_count > 0) {
412                         sz = size_inside_page(p, low_count);
413                         if (clear_user(buf, sz))
414                                 return -EFAULT;
415                         buf += sz;
416                         p += sz;
417                         read += sz;
418                         low_count -= sz;
419                         count -= sz;
420                 }
421 #endif
422                 while (low_count > 0) {
423                         sz = size_inside_page(p, low_count);
424
425                         /*
426                          * On ia64 if a page has been mapped somewhere as
427                          * uncached, then it must also be accessed uncached
428                          * by the kernel or data corruption may occur
429                          */
430                         kbuf = xlate_dev_kmem_ptr((char *)p);
431
432                         if (copy_to_user(buf, kbuf, sz))
433                                 return -EFAULT;
434                         buf += sz;
435                         p += sz;
436                         read += sz;
437                         low_count -= sz;
438                         count -= sz;
439                 }
440         }
441
442         if (count > 0) {
443                 kbuf = (char *)__get_free_page(GFP_KERNEL);
444                 if (!kbuf)
445                         return -ENOMEM;
446                 while (count > 0) {
447                         sz = size_inside_page(p, count);
448                         if (!is_vmalloc_or_module_addr((void *)p)) {
449                                 err = -ENXIO;
450                                 break;
451                         }
452                         sz = vread(kbuf, (char *)p, sz);
453                         if (!sz)
454                                 break;
455                         if (copy_to_user(buf, kbuf, sz)) {
456                                 err = -EFAULT;
457                                 break;
458                         }
459                         count -= sz;
460                         buf += sz;
461                         read += sz;
462                         p += sz;
463                 }
464                 free_page((unsigned long)kbuf);
465         }
466         *ppos = p;
467         return read ? read : err;
468 }
469
470
471 static ssize_t do_write_kmem(unsigned long p, const char __user *buf,
472                                 size_t count, loff_t *ppos)
473 {
474         ssize_t written, sz;
475         unsigned long copied;
476
477         written = 0;
478 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
479         /* we don't have page 0 mapped on sparc and m68k.. */
480         if (p < PAGE_SIZE) {
481                 sz = size_inside_page(p, count);
482                 /* Hmm. Do something? */
483                 buf += sz;
484                 p += sz;
485                 count -= sz;
486                 written += sz;
487         }
488 #endif
489
490         while (count > 0) {
491                 char *ptr;
492
493                 sz = size_inside_page(p, count);
494
495                 /*
496                  * On ia64 if a page has been mapped somewhere as uncached, then
497                  * it must also be accessed uncached by the kernel or data
498                  * corruption may occur.
499                  */
500                 ptr = xlate_dev_kmem_ptr((char *)p);
501
502                 copied = copy_from_user(ptr, buf, sz);
503                 if (copied) {
504                         written += sz - copied;
505                         if (written)
506                                 break;
507                         return -EFAULT;
508                 }
509                 buf += sz;
510                 p += sz;
511                 count -= sz;
512                 written += sz;
513         }
514
515         *ppos += written;
516         return written;
517 }
518
519 /*
520  * This function writes to the *virtual* memory as seen by the kernel.
521  */
522 static ssize_t write_kmem(struct file *file, const char __user *buf,
523                           size_t count, loff_t *ppos)
524 {
525         unsigned long p = *ppos;
526         ssize_t wrote = 0;
527         ssize_t virtr = 0;
528         char * kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
529         int err = 0;
530
531         if (p < (unsigned long) high_memory) {
532                 unsigned long to_write = min_t(unsigned long, count,
533                                                (unsigned long)high_memory - p);
534                 wrote = do_write_kmem(p, buf, to_write, ppos);
535                 if (wrote != to_write)
536                         return wrote;
537                 p += wrote;
538                 buf += wrote;
539                 count -= wrote;
540         }
541
542         if (count > 0) {
543                 kbuf = (char *)__get_free_page(GFP_KERNEL);
544                 if (!kbuf)
545                         return wrote ? wrote : -ENOMEM;
546                 while (count > 0) {
547                         unsigned long sz = size_inside_page(p, count);
548                         unsigned long n;
549
550                         if (!is_vmalloc_or_module_addr((void *)p)) {
551                                 err = -ENXIO;
552                                 break;
553                         }
554                         n = copy_from_user(kbuf, buf, sz);
555                         if (n) {
556                                 err = -EFAULT;
557                                 break;
558                         }
559                         vwrite(kbuf, (char *)p, sz);
560                         count -= sz;
561                         buf += sz;
562                         virtr += sz;
563                         p += sz;
564                 }
565                 free_page((unsigned long)kbuf);
566         }
567
568         *ppos = p;
569         return virtr + wrote ? : err;
570 }
571 #endif
572
573 #ifdef CONFIG_DEVPORT
574 static ssize_t read_port(struct file *file, char __user *buf,
575                          size_t count, loff_t *ppos)
576 {
577         unsigned long i = *ppos;
578         char __user *tmp = buf;
579
580         if (!access_ok(VERIFY_WRITE, buf, count))
581                 return -EFAULT;
582         while (count-- > 0 && i < 65536) {
583                 if (__put_user(inb(i), tmp) < 0)
584                         return -EFAULT;
585                 i++;
586                 tmp++;
587         }
588         *ppos = i;
589         return tmp-buf;
590 }
591
592 static ssize_t write_port(struct file *file, const char __user *buf,
593                           size_t count, loff_t *ppos)
594 {
595         unsigned long i = *ppos;
596         const char __user * tmp = buf;
597
598         if (!access_ok(VERIFY_READ, buf, count))
599                 return -EFAULT;
600         while (count-- > 0 && i < 65536) {
601                 char c;
602                 if (__get_user(c, tmp)) {
603                         if (tmp > buf)
604                                 break;
605                         return -EFAULT;
606                 }
607                 outb(c, i);
608                 i++;
609                 tmp++;
610         }
611         *ppos = i;
612         return tmp-buf;
613 }
614 #endif
615
616 static ssize_t read_null(struct file *file, char __user *buf,
617                          size_t count, loff_t *ppos)
618 {
619         return 0;
620 }
621
622 static ssize_t write_null(struct file *file, const char __user *buf,
623                           size_t count, loff_t *ppos)
624 {
625         return count;
626 }
627
628 static int pipe_to_null(struct pipe_inode_info *info, struct pipe_buffer *buf,
629                         struct splice_desc *sd)
630 {
631         return sd->len;
632 }
633
634 static ssize_t splice_write_null(struct pipe_inode_info *pipe, struct file *out,
635                                  loff_t *ppos, size_t len, unsigned int flags)
636 {
637         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_null);
638 }
639
640 static ssize_t read_zero(struct file *file, char __user *buf,
641                          size_t count, loff_t *ppos)
642 {
643         size_t written;
644
645         if (!count)
646                 return 0;
647
648         if (!access_ok(VERIFY_WRITE, buf, count))
649                 return -EFAULT;
650
651         written = 0;
652         while (count) {
653                 unsigned long unwritten;
654                 size_t chunk = count;
655
656                 if (chunk > PAGE_SIZE)
657                         chunk = PAGE_SIZE;      /* Just for latency reasons */
658                 unwritten = __clear_user(buf, chunk);
659                 written += chunk - unwritten;
660                 if (unwritten)
661                         break;
662                 if (signal_pending(current))
663                         return written ? written : -ERESTARTSYS;
664                 buf += chunk;
665                 count -= chunk;
666                 cond_resched();
667         }
668         return written ? written : -EFAULT;
669 }
670
671 static int mmap_zero(struct file *file, struct vm_area_struct *vma)
672 {
673 #ifndef CONFIG_MMU
674         return -ENOSYS;
675 #endif
676         if (vma->vm_flags & VM_SHARED)
677                 return shmem_zero_setup(vma);
678         return 0;
679 }
680
681 static ssize_t write_full(struct file *file, const char __user *buf,
682                           size_t count, loff_t *ppos)
683 {
684         return -ENOSPC;
685 }
686
687 /*
688  * Special lseek() function for /dev/null and /dev/zero.  Most notably, you
689  * can fopen() both devices with "a" now.  This was previously impossible.
690  * -- SRB.
691  */
692 static loff_t null_lseek(struct file *file, loff_t offset, int orig)
693 {
694         return file->f_pos = 0;
695 }
696
697 /*
698  * The memory devices use the full 32/64 bits of the offset, and so we cannot
699  * check against negative addresses: they are ok. The return value is weird,
700  * though, in that case (0).
701  *
702  * also note that seeking relative to the "end of file" isn't supported:
703  * it has no meaning, so it returns -EINVAL.
704  */
705 static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
706 {
707         loff_t ret;
708
709         mutex_lock(&file->f_path.dentry->d_inode->i_mutex);
710         switch (orig) {
711         case SEEK_CUR:
712                 offset += file->f_pos;
713                 if ((unsigned long long)offset <
714                     (unsigned long long)file->f_pos) {
715                         ret = -EOVERFLOW;
716                         break;
717                 }
718         case SEEK_SET:
719                 /* to avoid userland mistaking f_pos=-9 as -EBADF=-9 */
720                 if ((unsigned long long)offset >= ~0xFFFULL) {
721                         ret = -EOVERFLOW;
722                         break;
723                 }
724                 file->f_pos = offset;
725                 ret = file->f_pos;
726                 force_successful_syscall_return();
727                 break;
728         default:
729                 ret = -EINVAL;
730         }
731         mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
732         return ret;
733 }
734
735 static int open_port(struct inode * inode, struct file * filp)
736 {
737         return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
738 }
739
740 #define zero_lseek      null_lseek
741 #define full_lseek      null_lseek
742 #define write_zero      write_null
743 #define read_full       read_zero
744 #define open_mem        open_port
745 #define open_kmem       open_mem
746 #define open_oldmem     open_mem
747
748 static const struct file_operations mem_fops = {
749         .llseek         = memory_lseek,
750         .read           = read_mem,
751         .write          = write_mem,
752         .mmap           = mmap_mem,
753         .open           = open_mem,
754         .get_unmapped_area = get_unmapped_area_mem,
755 };
756
757 #ifdef CONFIG_DEVKMEM
758 static const struct file_operations kmem_fops = {
759         .llseek         = memory_lseek,
760         .read           = read_kmem,
761         .write          = write_kmem,
762         .mmap           = mmap_kmem,
763         .open           = open_kmem,
764         .get_unmapped_area = get_unmapped_area_mem,
765 };
766 #endif
767
768 static const struct file_operations null_fops = {
769         .llseek         = null_lseek,
770         .read           = read_null,
771         .write          = write_null,
772         .splice_write   = splice_write_null,
773 };
774
775 #ifdef CONFIG_DEVPORT
776 static const struct file_operations port_fops = {
777         .llseek         = memory_lseek,
778         .read           = read_port,
779         .write          = write_port,
780         .open           = open_port,
781 };
782 #endif
783
784 static const struct file_operations zero_fops = {
785         .llseek         = zero_lseek,
786         .read           = read_zero,
787         .write          = write_zero,
788         .mmap           = mmap_zero,
789 };
790
791 /*
792  * capabilities for /dev/zero
793  * - permits private mappings, "copies" are taken of the source of zeros
794  */
795 static struct backing_dev_info zero_bdi = {
796         .name           = "char/mem",
797         .capabilities   = BDI_CAP_MAP_COPY,
798 };
799
800 static const struct file_operations full_fops = {
801         .llseek         = full_lseek,
802         .read           = read_full,
803         .write          = write_full,
804 };
805
806 #ifdef CONFIG_CRASH_DUMP
807 static const struct file_operations oldmem_fops = {
808         .read   = read_oldmem,
809         .open   = open_oldmem,
810 };
811 #endif
812
813 static ssize_t kmsg_write(struct file *file, const char __user *buf,
814                           size_t count, loff_t *ppos)
815 {
816         char *tmp;
817         ssize_t ret;
818
819         tmp = kmalloc(count + 1, GFP_KERNEL);
820         if (tmp == NULL)
821                 return -ENOMEM;
822         ret = -EFAULT;
823         if (!copy_from_user(tmp, buf, count)) {
824                 tmp[count] = 0;
825                 ret = printk("%s", tmp);
826                 if (ret > count)
827                         /* printk can add a prefix */
828                         ret = count;
829         }
830         kfree(tmp);
831         return ret;
832 }
833
834 static const struct file_operations kmsg_fops = {
835         .write = kmsg_write,
836 };
837
838 static const struct memdev {
839         const char *name;
840         mode_t mode;
841         const struct file_operations *fops;
842         struct backing_dev_info *dev_info;
843 } devlist[] = {
844          [1] = { "mem", 0, &mem_fops, &directly_mappable_cdev_bdi },
845 #ifdef CONFIG_DEVKMEM
846          [2] = { "kmem", 0, &kmem_fops, &directly_mappable_cdev_bdi },
847 #endif
848          [3] = { "null", 0666, &null_fops, NULL },
849 #ifdef CONFIG_DEVPORT
850          [4] = { "port", 0, &port_fops, NULL },
851 #endif
852          [5] = { "zero", 0666, &zero_fops, &zero_bdi },
853          [7] = { "full", 0666, &full_fops, NULL },
854          [8] = { "random", 0666, &random_fops, NULL },
855          [9] = { "urandom", 0666, &urandom_fops, NULL },
856         [11] = { "kmsg", 0, &kmsg_fops, NULL },
857 #ifdef CONFIG_CRASH_DUMP
858         [12] = { "oldmem", 0, &oldmem_fops, NULL },
859 #endif
860 };
861
862 static int memory_open(struct inode *inode, struct file *filp)
863 {
864         int minor;
865         const struct memdev *dev;
866
867         minor = iminor(inode);
868         if (minor >= ARRAY_SIZE(devlist))
869                 return -ENXIO;
870
871         dev = &devlist[minor];
872         if (!dev->fops)
873                 return -ENXIO;
874
875         filp->f_op = dev->fops;
876         if (dev->dev_info)
877                 filp->f_mapping->backing_dev_info = dev->dev_info;
878
879         if (dev->fops->open)
880                 return dev->fops->open(inode, filp);
881
882         return 0;
883 }
884
885 static const struct file_operations memory_fops = {
886         .open = memory_open,
887 };
888
889 static char *mem_devnode(struct device *dev, mode_t *mode)
890 {
891         if (mode && devlist[MINOR(dev->devt)].mode)
892                 *mode = devlist[MINOR(dev->devt)].mode;
893         return NULL;
894 }
895
896 static struct class *mem_class;
897
898 static int __init chr_dev_init(void)
899 {
900         int minor;
901         int err;
902
903         err = bdi_init(&zero_bdi);
904         if (err)
905                 return err;
906
907         if (register_chrdev(MEM_MAJOR, "mem", &memory_fops))
908                 printk("unable to get major %d for memory devs\n", MEM_MAJOR);
909
910         mem_class = class_create(THIS_MODULE, "mem");
911         mem_class->devnode = mem_devnode;
912         for (minor = 1; minor < ARRAY_SIZE(devlist); minor++) {
913                 if (!devlist[minor].name)
914                         continue;
915                 device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor),
916                               NULL, devlist[minor].name);
917         }
918
919         return 0;
920 }
921
922 fs_initcall(chr_dev_init);