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