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   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 mmaping support, Feb 2000, Kanoj Sarcar <kanoj@sgi.com>
   9  */
  10
  11 #include <linux/config.h>
  12 #include <linux/mm.h>
  13 #include <linux/miscdevice.h>
  14 #include <linux/slab.h>
  15 #include <linux/vmalloc.h>
  16 #include <linux/mman.h>
  17 #include <linux/random.h>
  18 #include <linux/init.h>
  19 #include <linux/raw.h>
  20 #include <linux/tty.h>
  21 #include <linux/capability.h>
  22 #include <linux/smp_lock.h>
  23 #include <linux/devfs_fs_kernel.h>
  24 #include <linux/ptrace.h>
  25 #include <linux/device.h>
  26 #include <linux/highmem.h>
  27 #include <linux/crash_dump.h>
  28 #include <linux/backing-dev.h>
  29 #include <linux/bootmem.h>
  30
  31 #include <asm/uaccess.h>
  32 #include <asm/io.h>
  33
  34 #ifdef CONFIG_IA64
  35 # include <linux/efi.h>
  36 #endif
  37
  38 #if defined(CONFIG_S390_TAPE) && defined(CONFIG_S390_TAPE_CHAR)
  39 extern void tapechar_init(void);
  40 #endif
  41
  42 /*
  43  * Architectures vary in how they handle caching for addresses
  44  * outside of main memory.
  45  *
  46  */
  47 static inline int uncached_access(struct file *file, unsigned long addr)
  48 {
  49 #if defined(__i386__)
  50         /*
  51          * On the PPro and successors, the MTRRs are used to set
  52          * memory types for physical addresses outside main memory,
  53          * so blindly setting PCD or PWT on those pages is wrong.
  54          * For Pentiums and earlier, the surround logic should disable
  55          * caching for the high addresses through the KEN pin, but
  56          * we maintain the tradition of paranoia in this code.
  57          */
  58         if (file->f_flags & O_SYNC)
  59                 return 1;
  60         return !( test_bit(X86_FEATURE_MTRR, boot_cpu_data.x86_capability) ||
  61                   test_bit(X86_FEATURE_K6_MTRR, boot_cpu_data.x86_capability) ||
  62                   test_bit(X86_FEATURE_CYRIX_ARR, boot_cpu_data.x86_capability) ||
  63                   test_bit(X86_FEATURE_CENTAUR_MCR, boot_cpu_data.x86_capability) )
  64           && addr >= __pa(high_memory);
  65 #elif defined(__x86_64__)
  66         /*
  67          * This is broken because it can generate memory type aliases,
  68          * which can cause cache corruptions
  69          * But it is only available for root and we have to be bug-to-bug
  70          * compatible with i386.
  71          */
  72         if (file->f_flags & O_SYNC)
  73                 return 1;
  74         /* same behaviour as i386. PAT always set to cached and MTRRs control the
  75            caching behaviour.
  76            Hopefully a full PAT implementation will fix that soon. */
  77         return 0;
  78 #elif defined(CONFIG_IA64)
  79         /*
  80          * On ia64, we ignore O_SYNC because we cannot tolerate memory attribute aliases.
  81          */
  82         return !(efi_mem_attributes(addr) & EFI_MEMORY_WB);
  83 #else
  84         /*
  85          * Accessing memory above the top the kernel knows about or through a file pointer
  86          * that was marked O_SYNC will be done non-cached.
  87          */
  88         if (file->f_flags & O_SYNC)
  89                 return 1;
  90         return addr >= __pa(high_memory);
  91 #endif
  92 }
  93
  94 #ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE
  95 static inline int valid_phys_addr_range(unsigned long addr, size_t *count)
  96 {
  97         unsigned long end_mem;
  98
  99         end_mem = __pa(high_memory);
 100         if (addr >= end_mem)
 101                 return 0;
 102
 103         if (*count > end_mem - addr)
 104                 *count = end_mem - addr;
 105
 106         return 1;
 107 }
 108 #endif
 109
 110 /*
 111  * This funcion reads the *physical* memory. The f_pos points directly to the
 112  * memory location.
 113  */
 114 static ssize_t read_mem(struct file * file, char __user * buf,
 115                         size_t count, loff_t *ppos)
 116 {
 117         unsigned long p = *ppos;
 118         ssize_t read, sz;
 119         char *ptr;
 120
 121         if (!valid_phys_addr_range(p, &count))
 122                 return -EFAULT;
 123         read = 0;
 124 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 125         /* we don't have page 0 mapped on sparc and m68k.. */
 126         if (p < PAGE_SIZE) {
 127                 sz = PAGE_SIZE - p;
 128                 if (sz > count)
 129                         sz = count;
 130                 if (sz > 0) {
 131                         if (clear_user(buf, sz))
 132                                 return -EFAULT;
 133                         buf += sz;
 134                         p += sz;
 135                         count -= sz;
 136                         read += sz;
 137                 }
 138         }
 139 #endif
 140
 141         while (count > 0) {
 142                 /*
 143                  * Handle first page in case it's not aligned
 144                  */
 145                 if (-p & (PAGE_SIZE - 1))
 146                         sz = -p & (PAGE_SIZE - 1);
 147                 else
 148                         sz = PAGE_SIZE;
 149
 150                 sz = min_t(unsigned long, sz, count);
 151
 152                 /*
 153                  * On ia64 if a page has been mapped somewhere as
 154                  * uncached, then it must also be accessed uncached
 155                  * by the kernel or data corruption may occur
 156                  */
 157                 ptr = xlate_dev_mem_ptr(p);
 158
 159                 if (copy_to_user(buf, ptr, sz))
 160                         return -EFAULT;
 161                 buf += sz;
 162                 p += sz;
 163                 count -= sz;
 164                 read += sz;
 165         }
 166
 167         *ppos += read;
 168         return read;
 169 }
 170
 171 static ssize_t write_mem(struct file * file, const char __user * buf,
 172                          size_t count, loff_t *ppos)
 173 {
 174         unsigned long p = *ppos;
 175         ssize_t written, sz;
 176         unsigned long copied;
 177         void *ptr;
 178
 179         if (!valid_phys_addr_range(p, &count))
 180                 return -EFAULT;
 181
 182         written = 0;
 183
 184 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 185         /* we don't have page 0 mapped on sparc and m68k.. */
 186         if (p < PAGE_SIZE) {
 187                 unsigned long sz = PAGE_SIZE - p;
 188                 if (sz > count)
 189                         sz = count;
 190                 /* Hmm. Do something? */
 191                 buf += sz;
 192                 p += sz;
 193                 count -= sz;
 194                 written += sz;
 195         }
 196 #endif
 197
 198         while (count > 0) {
 199                 /*
 200                  * Handle first page in case it's not aligned
 201                  */
 202                 if (-p & (PAGE_SIZE - 1))
 203                         sz = -p & (PAGE_SIZE - 1);
 204                 else
 205                         sz = PAGE_SIZE;
 206
 207                 sz = min_t(unsigned long, sz, count);
 208
 209                 /*
 210                  * On ia64 if a page has been mapped somewhere as
 211                  * uncached, then it must also be accessed uncached
 212                  * by the kernel or data corruption may occur
 213                  */
 214                 ptr = xlate_dev_mem_ptr(p);
 215
 216                 copied = copy_from_user(ptr, buf, sz);
 217                 if (copied) {
 218                         ssize_t ret;
 219
 220                         ret = written + (sz - copied);
 221                         if (ret)
 222                                 return ret;
 223                         return -EFAULT;
 224                 }
 225                 buf += sz;
 226                 p += sz;
 227                 count -= sz;
 228                 written += sz;
 229         }
 230
 231         *ppos += written;
 232         return written;
 233 }
 234
 235 static int mmap_mem(struct file * file, struct vm_area_struct * vma)
 236 {
 237 #if defined(__HAVE_PHYS_MEM_ACCESS_PROT)
 238         unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
 239
 240         vma->vm_page_prot = phys_mem_access_prot(file, offset,
 241                                                  vma->vm_end - vma->vm_start,
 242                                                  vma->vm_page_prot);
 243 #elif defined(pgprot_noncached)
 244         unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
 245         int uncached;
 246
 247         uncached = uncached_access(file, offset);
 248         if (uncached)
 249                 vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 250 #endif
 251
 252         /* Remap-pfn-range will mark the range VM_IO and VM_RESERVED */
 253         if (remap_pfn_range(vma,
 254                             vma->vm_start,
 255                             vma->vm_pgoff,
 256                             vma->vm_end-vma->vm_start,
 257                             vma->vm_page_prot))
 258                 return -EAGAIN;
 259         return 0;
 260 }
 261
 262 static int mmap_kmem(struct file * file, struct vm_area_struct * vma)
 263 {
 264         unsigned long long val;
 265         /*
 266          * RED-PEN: on some architectures there is more mapped memory
 267          * than available in mem_map which pfn_valid checks
 268          * for. Perhaps should add a new macro here.
 269          *
 270          * RED-PEN: vmalloc is not supported right now.
 271          */
 272         if (!pfn_valid(vma->vm_pgoff))
 273                 return -EIO;
 274         val = (u64)vma->vm_pgoff << PAGE_SHIFT;
 275         vma->vm_pgoff = __pa(val) >> PAGE_SHIFT;
 276         return mmap_mem(file, vma);
 277 }
 278
 279 #ifdef CONFIG_CRASH_DUMP
 280 /*
 281  * Read memory corresponding to the old kernel.
 282  */
 283 static ssize_t read_oldmem(struct file *file, char __user *buf,
 284                                 size_t count, loff_t *ppos)
 285 {
 286         unsigned long pfn, offset;
 287         size_t read = 0, csize;
 288         int rc = 0;
 289
 290         while (count) {
 291                 pfn = *ppos / PAGE_SIZE;
 292                 if (pfn > saved_max_pfn)
 293                         return read;
 294
 295                 offset = (unsigned long)(*ppos % PAGE_SIZE);
 296                 if (count > PAGE_SIZE - offset)
 297                         csize = PAGE_SIZE - offset;
 298                 else
 299                         csize = count;
 300
 301                 rc = copy_oldmem_page(pfn, buf, csize, offset, 1);
 302                 if (rc < 0)
 303                         return rc;
 304                 buf += csize;
 305                 *ppos += csize;
 306                 read += csize;
 307                 count -= csize;
 308         }
 309         return read;
 310 }
 311 #endif
 312
 313 extern long vread(char *buf, char *addr, unsigned long count);
 314 extern long vwrite(char *buf, char *addr, unsigned long count);
 315
 316 /*
 317  * This function reads the *virtual* memory as seen by the kernel.
 318  */
 319 static ssize_t read_kmem(struct file *file, char __user *buf,
 320                          size_t count, loff_t *ppos)
 321 {
 322         unsigned long p = *ppos;
 323         ssize_t low_count, read, sz;
 324         char * kbuf; /* k-addr because vread() takes vmlist_lock rwlock */
 325
 326         read = 0;
 327         if (p < (unsigned long) high_memory) {
 328                 low_count = count;
 329                 if (count > (unsigned long) high_memory - p)
 330                         low_count = (unsigned long) high_memory - p;
 331
 332 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 333                 /* we don't have page 0 mapped on sparc and m68k.. */
 334                 if (p < PAGE_SIZE && low_count > 0) {
 335                         size_t tmp = PAGE_SIZE - p;
 336                         if (tmp > low_count) tmp = low_count;
 337                         if (clear_user(buf, tmp))
 338                                 return -EFAULT;
 339                         buf += tmp;
 340                         p += tmp;
 341                         read += tmp;
 342                         low_count -= tmp;
 343                         count -= tmp;
 344                 }
 345 #endif
 346                 while (low_count > 0) {
 347                         /*
 348                          * Handle first page in case it's not aligned
 349                          */
 350                         if (-p & (PAGE_SIZE - 1))
 351                                 sz = -p & (PAGE_SIZE - 1);
 352                         else
 353                                 sz = PAGE_SIZE;
 354
 355                         sz = min_t(unsigned long, sz, low_count);
 356
 357                         /*
 358                          * On ia64 if a page has been mapped somewhere as
 359                          * uncached, then it must also be accessed uncached
 360                          * by the kernel or data corruption may occur
 361                          */
 362                         kbuf = xlate_dev_kmem_ptr((char *)p);
 363
 364                         if (copy_to_user(buf, kbuf, sz))
 365                                 return -EFAULT;
 366                         buf += sz;
 367                         p += sz;
 368                         read += sz;
 369                         low_count -= sz;
 370                         count -= sz;
 371                 }
 372         }
 373
 374         if (count > 0) {
 375                 kbuf = (char *)__get_free_page(GFP_KERNEL);
 376                 if (!kbuf)
 377                         return -ENOMEM;
 378                 while (count > 0) {
 379                         int len = count;
 380
 381                         if (len > PAGE_SIZE)
 382                                 len = PAGE_SIZE;
 383                         len = vread(kbuf, (char *)p, len);
 384                         if (!len)
 385                                 break;
 386                         if (copy_to_user(buf, kbuf, len)) {
 387                                 free_page((unsigned long)kbuf);
 388                                 return -EFAULT;
 389                         }
 390                         count -= len;
 391                         buf += len;
 392                         read += len;
 393                         p += len;
 394                 }
 395                 free_page((unsigned long)kbuf);
 396         }
 397         *ppos = p;
 398         return read;
 399 }
 400
 401
 402 static inline ssize_t
 403 do_write_kmem(void *p, unsigned long realp, const char __user * buf,
 404               size_t count, loff_t *ppos)
 405 {
 406         ssize_t written, sz;
 407         unsigned long copied;
 408
 409         written = 0;
 410 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 411         /* we don't have page 0 mapped on sparc and m68k.. */
 412         if (realp < PAGE_SIZE) {
 413                 unsigned long sz = PAGE_SIZE - realp;
 414                 if (sz > count)
 415                         sz = count;
 416                 /* Hmm. Do something? */
 417                 buf += sz;
 418                 p += sz;
 419                 realp += sz;
 420                 count -= sz;
 421                 written += sz;
 422         }
 423 #endif
 424
 425         while (count > 0) {
 426                 char *ptr;
 427                 /*
 428                  * Handle first page in case it's not aligned
 429                  */
 430                 if (-realp & (PAGE_SIZE - 1))
 431                         sz = -realp & (PAGE_SIZE - 1);
 432                 else
 433                         sz = PAGE_SIZE;
 434
 435                 sz = min_t(unsigned long, sz, count);
 436
 437                 /*
 438                  * On ia64 if a page has been mapped somewhere as
 439                  * uncached, then it must also be accessed uncached
 440                  * by the kernel or data corruption may occur
 441                  */
 442                 ptr = xlate_dev_kmem_ptr(p);
 443
 444                 copied = copy_from_user(ptr, buf, sz);
 445                 if (copied) {
 446                         ssize_t ret;
 447
 448                         ret = written + (sz - copied);
 449                         if (ret)
 450                                 return ret;
 451                         return -EFAULT;
 452                 }
 453                 buf += sz;
 454                 p += sz;
 455                 realp += sz;
 456                 count -= sz;
 457                 written += sz;
 458         }
 459
 460         *ppos += written;
 461         return written;
 462 }
 463
 464
 465 /*
 466  * This function writes to the *virtual* memory as seen by the kernel.
 467  */
 468 static ssize_t write_kmem(struct file * file, const char __user * buf,
 469                           size_t count, loff_t *ppos)
 470 {
 471         unsigned long p = *ppos;
 472         ssize_t wrote = 0;
 473         ssize_t virtr = 0;
 474         ssize_t written;
 475         char * kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
 476
 477         if (p < (unsigned long) high_memory) {
 478
 479                 wrote = count;
 480                 if (count > (unsigned long) high_memory - p)
 481                         wrote = (unsigned long) high_memory - p;
 482
 483                 written = do_write_kmem((void*)p, p, buf, wrote, ppos);
 484                 if (written != wrote)
 485                         return written;
 486                 wrote = written;
 487                 p += wrote;
 488                 buf += wrote;
 489                 count -= wrote;
 490         }
 491
 492         if (count > 0) {
 493                 kbuf = (char *)__get_free_page(GFP_KERNEL);
 494                 if (!kbuf)
 495                         return wrote ? wrote : -ENOMEM;
 496                 while (count > 0) {
 497                         int len = count;
 498
 499                         if (len > PAGE_SIZE)
 500                                 len = PAGE_SIZE;
 501                         if (len) {
 502                                 written = copy_from_user(kbuf, buf, len);
 503                                 if (written) {
 504                                         ssize_t ret;
 505
 506                                         free_page((unsigned long)kbuf);
 507                                         ret = wrote + virtr + (len - written);
 508                                         return ret ? ret : -EFAULT;
 509                                 }
 510                         }
 511                         len = vwrite(kbuf, (char *)p, len);
 512                         count -= len;
 513                         buf += len;
 514                         virtr += len;
 515                         p += len;
 516                 }
 517                 free_page((unsigned long)kbuf);
 518         }
 519
 520         *ppos = p;
 521         return virtr + wrote;
 522 }
 523
 524 #if (defined(CONFIG_ISA) || !defined(__mc68000__)) && (!defined(CONFIG_PPC_ISERIES) || defined(CONFIG_PCI))
 525 static ssize_t read_port(struct file * file, char __user * buf,
 526                          size_t count, loff_t *ppos)
 527 {
 528         unsigned long i = *ppos;
 529         char __user *tmp = buf;
 530
 531         if (!access_ok(VERIFY_WRITE, buf, count))
 532                 return -EFAULT;
 533         while (count-- > 0 && i < 65536) {
 534                 if (__put_user(inb(i),tmp) < 0)
 535                         return -EFAULT;
 536                 i++;
 537                 tmp++;
 538         }
 539         *ppos = i;
 540         return tmp-buf;
 541 }
 542
 543 static ssize_t write_port(struct file * file, const char __user * buf,
 544                           size_t count, loff_t *ppos)
 545 {
 546         unsigned long i = *ppos;
 547         const char __user * tmp = buf;
 548
 549         if (!access_ok(VERIFY_READ,buf,count))
 550                 return -EFAULT;
 551         while (count-- > 0 && i < 65536) {
 552                 char c;
 553                 if (__get_user(c, tmp))
 554                         return -EFAULT;
 555                 outb(c,i);
 556                 i++;
 557                 tmp++;
 558         }
 559         *ppos = i;
 560         return tmp-buf;
 561 }
 562 #endif
 563
 564 static ssize_t read_null(struct file * file, char __user * buf,
 565                          size_t count, loff_t *ppos)
 566 {
 567         return 0;
 568 }
 569
 570 static ssize_t write_null(struct file * file, const char __user * buf,
 571                           size_t count, loff_t *ppos)
 572 {
 573         return count;
 574 }
 575
 576 #ifdef CONFIG_MMU
 577 /*
 578  * For fun, we are using the MMU for this.
 579  */
 580 static inline size_t read_zero_pagealigned(char __user * buf, size_t size)
 581 {
 582         struct mm_struct *mm;
 583         struct vm_area_struct * vma;
 584         unsigned long addr=(unsigned long)buf;
 585
 586         mm = current->mm;
 587         /* Oops, this was forgotten before. -ben */
 588         down_read(&mm->mmap_sem);
 589
 590         /* For private mappings, just map in zero pages. */
 591         for (vma = find_vma(mm, addr); vma; vma = vma->vm_next) {
 592                 unsigned long count;
 593
 594                 if (vma->vm_start > addr || (vma->vm_flags & VM_WRITE) == 0)
 595                         goto out_up;
 596                 if (vma->vm_flags & (VM_SHARED | VM_HUGETLB))
 597                         break;
 598                 count = vma->vm_end - addr;
 599                 if (count > size)
 600                         count = size;
 601
 602                 zap_page_range(vma, addr, count, NULL);
 603                 zeromap_page_range(vma, addr, count, PAGE_COPY);
 604
 605                 size -= count;
 606                 buf += count;
 607                 addr += count;
 608                 if (size == 0)
 609                         goto out_up;
 610         }
 611
 612         up_read(&mm->mmap_sem);
 613
 614         /* The shared case is hard. Let's do the conventional zeroing. */
 615         do {
 616                 unsigned long unwritten = clear_user(buf, PAGE_SIZE);
 617                 if (unwritten)
 618                         return size + unwritten - PAGE_SIZE;
 619                 cond_resched();
 620                 buf += PAGE_SIZE;
 621                 size -= PAGE_SIZE;
 622         } while (size);
 623
 624         return size;
 625 out_up:
 626         up_read(&mm->mmap_sem);
 627         return size;
 628 }
 629
 630 static ssize_t read_zero(struct file * file, char __user * buf,
 631                          size_t count, loff_t *ppos)
 632 {
 633         unsigned long left, unwritten, written = 0;
 634
 635         if (!count)
 636                 return 0;
 637
 638         if (!access_ok(VERIFY_WRITE, buf, count))
 639                 return -EFAULT;
 640
 641         left = count;
 642
 643         /* do we want to be clever? Arbitrary cut-off */
 644         if (count >= PAGE_SIZE*4) {
 645                 unsigned long partial;
 646
 647                 /* How much left of the page? */
 648                 partial = (PAGE_SIZE-1) & -(unsigned long) buf;
 649                 unwritten = clear_user(buf, partial);
 650                 written = partial - unwritten;
 651                 if (unwritten)
 652                         goto out;
 653                 left -= partial;
 654                 buf += partial;
 655                 unwritten = read_zero_pagealigned(buf, left & PAGE_MASK);
 656                 written += (left & PAGE_MASK) - unwritten;
 657                 if (unwritten)
 658                         goto out;
 659                 buf += left & PAGE_MASK;
 660                 left &= ~PAGE_MASK;
 661         }
 662         unwritten = clear_user(buf, left);
 663         written += left - unwritten;
 664 out:
 665         return written ? written : -EFAULT;
 666 }
 667
 668 static int mmap_zero(struct file * file, struct vm_area_struct * vma)
 669 {
 670         if (vma->vm_flags & VM_SHARED)
 671                 return shmem_zero_setup(vma);
 672         if (zeromap_page_range(vma, vma->vm_start, vma->vm_end - vma->vm_start, vma->vm_page_prot))
 673                 return -EAGAIN;
 674         return 0;
 675 }
 676 #else /* CONFIG_MMU */
 677 static ssize_t read_zero(struct file * file, char * buf,
 678                          size_t count, loff_t *ppos)
 679 {
 680         size_t todo = count;
 681
 682         while (todo) {
 683                 size_t chunk = todo;
 684
 685                 if (chunk > 4096)
 686                         chunk = 4096;   /* Just for latency reasons */
 687                 if (clear_user(buf, chunk))
 688                         return -EFAULT;
 689                 buf += chunk;
 690                 todo -= chunk;
 691                 cond_resched();
 692         }
 693         return count;
 694 }
 695
 696 static int mmap_zero(struct file * file, struct vm_area_struct * vma)
 697 {
 698         return -ENOSYS;
 699 }
 700 #endif /* CONFIG_MMU */
 701
 702 static ssize_t write_full(struct file * file, const char __user * buf,
 703                           size_t count, loff_t *ppos)
 704 {
 705         return -ENOSPC;
 706 }
 707
 708 /*
 709  * Special lseek() function for /dev/null and /dev/zero.  Most notably, you
 710  * can fopen() both devices with "a" now.  This was previously impossible.
 711  * -- SRB.
 712  */
 713
 714 static loff_t null_lseek(struct file * file, loff_t offset, int orig)
 715 {
 716         return file->f_pos = 0;
 717 }
 718
 719 /*
 720  * The memory devices use the full 32/64 bits of the offset, and so we cannot
 721  * check against negative addresses: they are ok. The return value is weird,
 722  * though, in that case (0).
 723  *
 724  * also note that seeking relative to the "end of file" isn't supported:
 725  * it has no meaning, so it returns -EINVAL.
 726  */
 727 static loff_t memory_lseek(struct file * file, loff_t offset, int orig)
 728 {
 729         loff_t ret;
 730
 731         down(&file->f_dentry->d_inode->i_sem);
 732         switch (orig) {
 733                 case 0:
 734                         file->f_pos = offset;
 735                         ret = file->f_pos;
 736                         force_successful_syscall_return();
 737                         break;
 738                 case 1:
 739                         file->f_pos += offset;
 740                         ret = file->f_pos;
 741                         force_successful_syscall_return();
 742                         break;
 743                 default:
 744                         ret = -EINVAL;
 745         }
 746         up(&file->f_dentry->d_inode->i_sem);
 747         return ret;
 748 }
 749
 750 static int open_port(struct inode * inode, struct file * filp)
 751 {
 752         return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
 753 }
 754
 755 #define zero_lseek      null_lseek
 756 #define full_lseek      null_lseek
 757 #define write_zero      write_null
 758 #define read_full       read_zero
 759 #define open_mem        open_port
 760 #define open_kmem       open_mem
 761 #define open_oldmem     open_mem
 762
 763 static struct file_operations mem_fops = {
 764         .llseek         = memory_lseek,
 765         .read           = read_mem,
 766         .write          = write_mem,
 767         .mmap           = mmap_mem,
 768         .open           = open_mem,
 769 };
 770
 771 static struct file_operations kmem_fops = {
 772         .llseek         = memory_lseek,
 773         .read           = read_kmem,
 774         .write          = write_kmem,
 775         .mmap           = mmap_kmem,
 776         .open           = open_kmem,
 777 };
 778
 779 static struct file_operations null_fops = {
 780         .llseek         = null_lseek,
 781         .read           = read_null,
 782         .write          = write_null,
 783 };
 784
 785 #if (defined(CONFIG_ISA) || !defined(__mc68000__)) && (!defined(CONFIG_PPC_ISERIES) || defined(CONFIG_PCI))
 786 static struct file_operations port_fops = {
 787         .llseek         = memory_lseek,
 788         .read           = read_port,
 789         .write          = write_port,
 790         .open           = open_port,
 791 };
 792 #endif
 793
 794 static struct file_operations zero_fops = {
 795         .llseek         = zero_lseek,
 796         .read           = read_zero,
 797         .write          = write_zero,
 798         .mmap           = mmap_zero,
 799 };
 800
 801 static struct backing_dev_info zero_bdi = {
 802         .capabilities   = BDI_CAP_MAP_COPY,
 803 };
 804
 805 static struct file_operations full_fops = {
 806         .llseek         = full_lseek,
 807         .read           = read_full,
 808         .write          = write_full,
 809 };
 810
 811 #ifdef CONFIG_CRASH_DUMP
 812 static struct file_operations oldmem_fops = {
 813         .read   = read_oldmem,
 814         .open   = open_oldmem,
 815 };
 816 #endif
 817
 818 static ssize_t kmsg_write(struct file * file, const char __user * buf,
 819                           size_t count, loff_t *ppos)
 820 {
 821         char *tmp;
 822         int ret;
 823
 824         tmp = kmalloc(count + 1, GFP_KERNEL);
 825         if (tmp == NULL)
 826                 return -ENOMEM;
 827         ret = -EFAULT;
 828         if (!copy_from_user(tmp, buf, count)) {
 829                 tmp[count] = 0;
 830                 ret = printk("%s", tmp);
 831         }
 832         kfree(tmp);
 833         return ret;
 834 }
 835
 836 static struct file_operations kmsg_fops = {
 837         .write =        kmsg_write,
 838 };
 839
 840 static int memory_open(struct inode * inode, struct file * filp)
 841 {
 842         switch (iminor(inode)) {
 843                 case 1:
 844                         filp->f_op = &mem_fops;
 845                         break;
 846                 case 2:
 847                         filp->f_op = &kmem_fops;
 848                         break;
 849                 case 3:
 850                         filp->f_op = &null_fops;
 851                         break;
 852 #if (defined(CONFIG_ISA) || !defined(__mc68000__)) && (!defined(CONFIG_PPC_ISERIES) || defined(CONFIG_PCI))
 853                 case 4:
 854                         filp->f_op = &port_fops;
 855                         break;
 856 #endif
 857                 case 5:
 858                         filp->f_mapping->backing_dev_info = &zero_bdi;
 859                         filp->f_op = &zero_fops;
 860                         break;
 861                 case 7:
 862                         filp->f_op = &full_fops;
 863                         break;
 864                 case 8:
 865                         filp->f_op = &random_fops;
 866                         break;
 867                 case 9:
 868                         filp->f_op = &urandom_fops;
 869                         break;
 870                 case 11:
 871                         filp->f_op = &kmsg_fops;
 872                         break;
 873 #ifdef CONFIG_CRASH_DUMP
 874                 case 12:
 875                         filp->f_op = &oldmem_fops;
 876                         break;
 877 #endif
 878                 default:
 879                         return -ENXIO;
 880         }
 881         if (filp->f_op && filp->f_op->open)
 882                 return filp->f_op->open(inode,filp);
 883         return 0;
 884 }
 885
 886 static struct file_operations memory_fops = {
 887         .open           = memory_open,  /* just a selector for the real open */
 888 };
 889
 890 static const struct {
 891         unsigned int            minor;
 892         char                    *name;
 893         umode_t                 mode;
 894         struct file_operations  *fops;
 895 } devlist[] = { /* list of minor devices */
 896         {1, "mem",     S_IRUSR | S_IWUSR | S_IRGRP, &mem_fops},
 897         {2, "kmem",    S_IRUSR | S_IWUSR | S_IRGRP, &kmem_fops},
 898         {3, "null",    S_IRUGO | S_IWUGO,           &null_fops},
 899 #if (defined(CONFIG_ISA) || !defined(__mc68000__)) && (!defined(CONFIG_PPC_ISERIES) || defined(CONFIG_PCI))
 900         {4, "port",    S_IRUSR | S_IWUSR | S_IRGRP, &port_fops},
 901 #endif
 902         {5, "zero",    S_IRUGO | S_IWUGO,           &zero_fops},
 903         {7, "full",    S_IRUGO | S_IWUGO,           &full_fops},
 904         {8, "random",  S_IRUGO | S_IWUSR,           &random_fops},
 905         {9, "urandom", S_IRUGO | S_IWUSR,           &urandom_fops},
 906         {11,"kmsg",    S_IRUGO | S_IWUSR,           &kmsg_fops},
 907 #ifdef CONFIG_CRASH_DUMP
 908         {12,"oldmem",    S_IRUSR | S_IWUSR | S_IRGRP, &oldmem_fops},
 909 #endif
 910 };
 911
 912 static struct class *mem_class;
 913
 914 static int __init chr_dev_init(void)
 915 {
 916         int i;
 917
 918         if (register_chrdev(MEM_MAJOR,"mem",&memory_fops))
 919                 printk("unable to get major %d for memory devs\n", MEM_MAJOR);
 920
 921         mem_class = class_create(THIS_MODULE, "mem");
 922         for (i = 0; i < ARRAY_SIZE(devlist); i++) {
 923                 class_device_create(mem_class, MKDEV(MEM_MAJOR, devlist[i].minor),
 924                                         NULL, devlist[i].name);
 925                 devfs_mk_cdev(MKDEV(MEM_MAJOR, devlist[i].minor),
 926                                 S_IFCHR | devlist[i].mode, devlist[i].name);
 927         }
 928
 929         return 0;
 930 }
 931
 932 fs_initcall(chr_dev_init);