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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/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 /*
  38  * Architectures vary in how they handle caching for addresses
  39  * outside of main memory.
  40  *
  41  */
  42 static inline int uncached_access(struct file *file, unsigned long addr)
  43 {
  44 #if defined(CONFIG_IA64)
  45         /*
  46          * On ia64, we ignore O_SYNC because we cannot tolerate memory attribute aliases.
  47          */
  48         return !(efi_mem_attributes(addr) & EFI_MEMORY_WB);
  49 #elif defined(CONFIG_MIPS)
  50         {
  51                 extern int __uncached_access(struct file *file,
  52                                              unsigned long addr);
  53
  54                 return __uncached_access(file, addr);
  55         }
  56 #else
  57         /*
  58          * Accessing memory above the top the kernel knows about or through a file pointer
  59          * that was marked O_SYNC will be done non-cached.
  60          */
  61         if (file->f_flags & O_SYNC)
  62                 return 1;
  63         return addr >= __pa(high_memory);
  64 #endif
  65 }
  66
  67 #ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE
  68 static inline int valid_phys_addr_range(unsigned long addr, size_t count)
  69 {
  70         if (addr + count > __pa(high_memory))
  71                 return 0;
  72
  73         return 1;
  74 }
  75
  76 static inline int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
  77 {
  78         return 1;
  79 }
  80 #endif
  81
  82 #ifdef CONFIG_NONPROMISC_DEVMEM
  83 static inline int range_is_allowed(unsigned long pfn, unsigned long size)
  84 {
  85         u64 from = ((u64)pfn) << PAGE_SHIFT;
  86         u64 to = from + size;
  87         u64 cursor = from;
  88
  89         while (cursor < to) {
  90                 if (!devmem_is_allowed(pfn)) {
  91                         printk(KERN_INFO
  92                 "Program %s tried to access /dev/mem between %Lx->%Lx.\n",
  93                                 current->comm, from, to);
  94                         return 0;
  95                 }
  96                 cursor += PAGE_SIZE;
  97                 pfn++;
  98         }
  99         return 1;
 100 }
 101 #else
 102 static inline int range_is_allowed(unsigned long pfn, unsigned long size)
 103 {
 104         return 1;
 105 }
 106 #endif
 107
 108 void __attribute__((weak)) unxlate_dev_mem_ptr(unsigned long phys, void *addr)
 109 {
 110 }
 111
 112 /*
 113  * This funcion reads the *physical* memory. The f_pos points directly to the
 114  * memory location.
 115  */
 116 static ssize_t read_mem(struct file * file, char __user * buf,
 117                         size_t count, loff_t *ppos)
 118 {
 119         unsigned long p = *ppos;
 120         ssize_t read, sz;
 121         char *ptr;
 122
 123         if (!valid_phys_addr_range(p, count))
 124                 return -EFAULT;
 125         read = 0;
 126 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 127         /* we don't have page 0 mapped on sparc and m68k.. */
 128         if (p < PAGE_SIZE) {
 129                 sz = PAGE_SIZE - p;
 130                 if (sz > count)
 131                         sz = count;
 132                 if (sz > 0) {
 133                         if (clear_user(buf, sz))
 134                                 return -EFAULT;
 135                         buf += sz;
 136                         p += sz;
 137                         count -= sz;
 138                         read += sz;
 139                 }
 140         }
 141 #endif
 142
 143         while (count > 0) {
 144                 /*
 145                  * Handle first page in case it's not aligned
 146                  */
 147                 if (-p & (PAGE_SIZE - 1))
 148                         sz = -p & (PAGE_SIZE - 1);
 149                 else
 150                         sz = PAGE_SIZE;
 151
 152                 sz = min_t(unsigned long, sz, count);
 153
 154                 if (!range_is_allowed(p >> PAGE_SHIFT, count))
 155                         return -EPERM;
 156
 157                 /*
 158                  * On ia64 if a page has been mapped somewhere as
 159                  * uncached, then it must also be accessed uncached
 160                  * by the kernel or data corruption may occur
 161                  */
 162                 ptr = xlate_dev_mem_ptr(p);
 163                 if (!ptr)
 164                         return -EFAULT;
 165
 166                 if (copy_to_user(buf, ptr, sz)) {
 167                         unxlate_dev_mem_ptr(p, ptr);
 168                         return -EFAULT;
 169                 }
 170
 171                 unxlate_dev_mem_ptr(p, ptr);
 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                 unsigned long sz = PAGE_SIZE - p;
 200                 if (sz > count)
 201                         sz = count;
 202                 /* Hmm. Do something? */
 203                 buf += sz;
 204                 p += sz;
 205                 count -= sz;
 206                 written += sz;
 207         }
 208 #endif
 209
 210         while (count > 0) {
 211                 /*
 212                  * Handle first page in case it's not aligned
 213                  */
 214                 if (-p & (PAGE_SIZE - 1))
 215                         sz = -p & (PAGE_SIZE - 1);
 216                 else
 217                         sz = PAGE_SIZE;
 218
 219                 sz = min_t(unsigned long, sz, count);
 220
 221                 if (!range_is_allowed(p >> PAGE_SHIFT, sz))
 222                         return -EPERM;
 223
 224                 /*
 225                  * On ia64 if a page has been mapped somewhere as
 226                  * uncached, then it must also be accessed uncached
 227                  * by the kernel or data corruption may occur
 228                  */
 229                 ptr = xlate_dev_mem_ptr(p);
 230                 if (!ptr) {
 231                         if (written)
 232                                 break;
 233                         return -EFAULT;
 234                 }
 235
 236                 copied = copy_from_user(ptr, buf, sz);
 237                 if (copied) {
 238                         written += sz - copied;
 239                         unxlate_dev_mem_ptr(p, ptr);
 240                         if (written)
 241                                 break;
 242                         return -EFAULT;
 243                 }
 244
 245                 unxlate_dev_mem_ptr(p, ptr);
 246
 247                 buf += sz;
 248                 p += sz;
 249                 count -= sz;
 250                 written += sz;
 251         }
 252
 253         *ppos += written;
 254         return written;
 255 }
 256
 257 int __attribute__((weak)) phys_mem_access_prot_allowed(struct file *file,
 258         unsigned long pfn, unsigned long size, pgprot_t *vma_prot)
 259 {
 260         return 1;
 261 }
 262
 263 #ifndef __HAVE_PHYS_MEM_ACCESS_PROT
 264 static pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 265                                      unsigned long size, pgprot_t vma_prot)
 266 {
 267 #ifdef pgprot_noncached
 268         unsigned long offset = pfn << PAGE_SHIFT;
 269
 270         if (uncached_access(file, offset))
 271                 return pgprot_noncached(vma_prot);
 272 #endif
 273         return vma_prot;
 274 }
 275 #endif
 276
 277 #ifndef CONFIG_MMU
 278 static unsigned long get_unmapped_area_mem(struct file *file,
 279                                            unsigned long addr,
 280                                            unsigned long len,
 281                                            unsigned long pgoff,
 282                                            unsigned long flags)
 283 {
 284         if (!valid_mmap_phys_addr_range(pgoff, len))
 285                 return (unsigned long) -EINVAL;
 286         return pgoff << PAGE_SHIFT;
 287 }
 288
 289 /* can't do an in-place private mapping if there's no MMU */
 290 static inline int private_mapping_ok(struct vm_area_struct *vma)
 291 {
 292         return vma->vm_flags & VM_MAYSHARE;
 293 }
 294 #else
 295 #define get_unmapped_area_mem   NULL
 296
 297 static inline int private_mapping_ok(struct vm_area_struct *vma)
 298 {
 299         return 1;
 300 }
 301 #endif
 302
 303 void __attribute__((weak))
 304 map_devmem(unsigned long pfn, unsigned long len, pgprot_t prot)
 305 {
 306         /* nothing. architectures can override. */
 307 }
 308
 309 void __attribute__((weak))
 310 unmap_devmem(unsigned long pfn, unsigned long len, pgprot_t prot)
 311 {
 312         /* nothing. architectures can override. */
 313 }
 314
 315 static void mmap_mem_open(struct vm_area_struct *vma)
 316 {
 317         map_devmem(vma->vm_pgoff,  vma->vm_end - vma->vm_start,
 318                         vma->vm_page_prot);
 319 }
 320
 321 static void mmap_mem_close(struct vm_area_struct *vma)
 322 {
 323         unmap_devmem(vma->vm_pgoff,  vma->vm_end - vma->vm_start,
 324                         vma->vm_page_prot);
 325 }
 326
 327 static struct vm_operations_struct mmap_mem_ops = {
 328         .open  = mmap_mem_open,
 329         .close = mmap_mem_close
 330 };
 331
 332 static int mmap_mem(struct file * file, struct vm_area_struct * vma)
 333 {
 334         size_t size = vma->vm_end - vma->vm_start;
 335
 336         if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))
 337                 return -EINVAL;
 338
 339         if (!private_mapping_ok(vma))
 340                 return -ENOSYS;
 341
 342         if (!range_is_allowed(vma->vm_pgoff, size))
 343                 return -EPERM;
 344
 345         if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size,
 346                                                 &vma->vm_page_prot))
 347                 return -EINVAL;
 348
 349         vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,
 350                                                  size,
 351                                                  vma->vm_page_prot);
 352
 353         vma->vm_ops = &mmap_mem_ops;
 354
 355         /* Remap-pfn-range will mark the range VM_IO and VM_RESERVED */
 356         if (remap_pfn_range(vma,
 357                             vma->vm_start,
 358                             vma->vm_pgoff,
 359                             size,
 360                             vma->vm_page_prot)) {
 361                 unmap_devmem(vma->vm_pgoff, size, vma->vm_page_prot);
 362                 return -EAGAIN;
 363         }
 364         return 0;
 365 }
 366
 367 #ifdef CONFIG_DEVKMEM
 368 static int mmap_kmem(struct file * file, struct vm_area_struct * vma)
 369 {
 370         unsigned long pfn;
 371
 372         /* Turn a kernel-virtual address into a physical page frame */
 373         pfn = __pa((u64)vma->vm_pgoff << PAGE_SHIFT) >> PAGE_SHIFT;
 374
 375         /*
 376          * RED-PEN: on some architectures there is more mapped memory
 377          * than available in mem_map which pfn_valid checks
 378          * for. Perhaps should add a new macro here.
 379          *
 380          * RED-PEN: vmalloc is not supported right now.
 381          */
 382         if (!pfn_valid(pfn))
 383                 return -EIO;
 384
 385         vma->vm_pgoff = pfn;
 386         return mmap_mem(file, vma);
 387 }
 388 #endif
 389
 390 #ifdef CONFIG_CRASH_DUMP
 391 /*
 392  * Read memory corresponding to the old kernel.
 393  */
 394 static ssize_t read_oldmem(struct file *file, char __user *buf,
 395                                 size_t count, loff_t *ppos)
 396 {
 397         unsigned long pfn, offset;
 398         size_t read = 0, csize;
 399         int rc = 0;
 400
 401         while (count) {
 402                 pfn = *ppos / PAGE_SIZE;
 403                 if (pfn > saved_max_pfn)
 404                         return read;
 405
 406                 offset = (unsigned long)(*ppos % PAGE_SIZE);
 407                 if (count > PAGE_SIZE - offset)
 408                         csize = PAGE_SIZE - offset;
 409                 else
 410                         csize = count;
 411
 412                 rc = copy_oldmem_page(pfn, buf, csize, offset, 1);
 413                 if (rc < 0)
 414                         return rc;
 415                 buf += csize;
 416                 *ppos += csize;
 417                 read += csize;
 418                 count -= csize;
 419         }
 420         return read;
 421 }
 422 #endif
 423
 424 extern long vread(char *buf, char *addr, unsigned long count);
 425 extern long vwrite(char *buf, char *addr, unsigned long count);
 426
 427 #ifdef CONFIG_DEVKMEM
 428 /*
 429  * This function reads the *virtual* memory as seen by the kernel.
 430  */
 431 static ssize_t read_kmem(struct file *file, char __user *buf,
 432                          size_t count, loff_t *ppos)
 433 {
 434         unsigned long p = *ppos;
 435         ssize_t low_count, read, sz;
 436         char * kbuf; /* k-addr because vread() takes vmlist_lock rwlock */
 437
 438         read = 0;
 439         if (p < (unsigned long) high_memory) {
 440                 low_count = count;
 441                 if (count > (unsigned long) high_memory - p)
 442                         low_count = (unsigned long) high_memory - p;
 443
 444 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 445                 /* we don't have page 0 mapped on sparc and m68k.. */
 446                 if (p < PAGE_SIZE && low_count > 0) {
 447                         size_t tmp = PAGE_SIZE - p;
 448                         if (tmp > low_count) tmp = low_count;
 449                         if (clear_user(buf, tmp))
 450                                 return -EFAULT;
 451                         buf += tmp;
 452                         p += tmp;
 453                         read += tmp;
 454                         low_count -= tmp;
 455                         count -= tmp;
 456                 }
 457 #endif
 458                 while (low_count > 0) {
 459                         /*
 460                          * Handle first page in case it's not aligned
 461                          */
 462                         if (-p & (PAGE_SIZE - 1))
 463                                 sz = -p & (PAGE_SIZE - 1);
 464                         else
 465                                 sz = PAGE_SIZE;
 466
 467                         sz = min_t(unsigned long, sz, low_count);
 468
 469                         /*
 470                          * On ia64 if a page has been mapped somewhere as
 471                          * uncached, then it must also be accessed uncached
 472                          * by the kernel or data corruption may occur
 473                          */
 474                         kbuf = xlate_dev_kmem_ptr((char *)p);
 475
 476                         if (copy_to_user(buf, kbuf, sz))
 477                                 return -EFAULT;
 478                         buf += sz;
 479                         p += sz;
 480                         read += sz;
 481                         low_count -= sz;
 482                         count -= sz;
 483                 }
 484         }
 485
 486         if (count > 0) {
 487                 kbuf = (char *)__get_free_page(GFP_KERNEL);
 488                 if (!kbuf)
 489                         return -ENOMEM;
 490                 while (count > 0) {
 491                         int len = count;
 492
 493                         if (len > PAGE_SIZE)
 494                                 len = PAGE_SIZE;
 495                         len = vread(kbuf, (char *)p, len);
 496                         if (!len)
 497                                 break;
 498                         if (copy_to_user(buf, kbuf, len)) {
 499                                 free_page((unsigned long)kbuf);
 500                                 return -EFAULT;
 501                         }
 502                         count -= len;
 503                         buf += len;
 504                         read += len;
 505                         p += len;
 506                 }
 507                 free_page((unsigned long)kbuf);
 508         }
 509         *ppos = p;
 510         return read;
 511 }
 512
 513
 514 static inline ssize_t
 515 do_write_kmem(void *p, unsigned long realp, const char __user * buf,
 516               size_t count, loff_t *ppos)
 517 {
 518         ssize_t written, sz;
 519         unsigned long copied;
 520
 521         written = 0;
 522 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 523         /* we don't have page 0 mapped on sparc and m68k.. */
 524         if (realp < PAGE_SIZE) {
 525                 unsigned long sz = PAGE_SIZE - realp;
 526                 if (sz > count)
 527                         sz = count;
 528                 /* Hmm. Do something? */
 529                 buf += sz;
 530                 p += sz;
 531                 realp += sz;
 532                 count -= sz;
 533                 written += sz;
 534         }
 535 #endif
 536
 537         while (count > 0) {
 538                 char *ptr;
 539                 /*
 540                  * Handle first page in case it's not aligned
 541                  */
 542                 if (-realp & (PAGE_SIZE - 1))
 543                         sz = -realp & (PAGE_SIZE - 1);
 544                 else
 545                         sz = PAGE_SIZE;
 546
 547                 sz = min_t(unsigned long, sz, count);
 548
 549                 /*
 550                  * On ia64 if a page has been mapped somewhere as
 551                  * uncached, then it must also be accessed uncached
 552                  * by the kernel or data corruption may occur
 553                  */
 554                 ptr = xlate_dev_kmem_ptr(p);
 555
 556                 copied = copy_from_user(ptr, buf, sz);
 557                 if (copied) {
 558                         written += sz - copied;
 559                         if (written)
 560                                 break;
 561                         return -EFAULT;
 562                 }
 563                 buf += sz;
 564                 p += sz;
 565                 realp += sz;
 566                 count -= sz;
 567                 written += sz;
 568         }
 569
 570         *ppos += written;
 571         return written;
 572 }
 573
 574
 575 /*
 576  * This function writes to the *virtual* memory as seen by the kernel.
 577  */
 578 static ssize_t write_kmem(struct file * file, const char __user * buf,
 579                           size_t count, loff_t *ppos)
 580 {
 581         unsigned long p = *ppos;
 582         ssize_t wrote = 0;
 583         ssize_t virtr = 0;
 584         ssize_t written;
 585         char * kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
 586
 587         if (p < (unsigned long) high_memory) {
 588
 589                 wrote = count;
 590                 if (count > (unsigned long) high_memory - p)
 591                         wrote = (unsigned long) high_memory - p;
 592
 593                 written = do_write_kmem((void*)p, p, buf, wrote, ppos);
 594                 if (written != wrote)
 595                         return written;
 596                 wrote = written;
 597                 p += wrote;
 598                 buf += wrote;
 599                 count -= wrote;
 600         }
 601
 602         if (count > 0) {
 603                 kbuf = (char *)__get_free_page(GFP_KERNEL);
 604                 if (!kbuf)
 605                         return wrote ? wrote : -ENOMEM;
 606                 while (count > 0) {
 607                         int len = count;
 608
 609                         if (len > PAGE_SIZE)
 610                                 len = PAGE_SIZE;
 611                         if (len) {
 612                                 written = copy_from_user(kbuf, buf, len);
 613                                 if (written) {
 614                                         if (wrote + virtr)
 615                                                 break;
 616                                         free_page((unsigned long)kbuf);
 617                                         return -EFAULT;
 618                                 }
 619                         }
 620                         len = vwrite(kbuf, (char *)p, len);
 621                         count -= len;
 622                         buf += len;
 623                         virtr += len;
 624                         p += len;
 625                 }
 626                 free_page((unsigned long)kbuf);
 627         }
 628
 629         *ppos = p;
 630         return virtr + wrote;
 631 }
 632 #endif
 633
 634 #ifdef CONFIG_DEVPORT
 635 static ssize_t read_port(struct file * file, char __user * buf,
 636                          size_t count, loff_t *ppos)
 637 {
 638         unsigned long i = *ppos;
 639         char __user *tmp = buf;
 640
 641         if (!access_ok(VERIFY_WRITE, buf, count))
 642                 return -EFAULT;
 643         while (count-- > 0 && i < 65536) {
 644                 if (__put_user(inb(i),tmp) < 0)
 645                         return -EFAULT;
 646                 i++;
 647                 tmp++;
 648         }
 649         *ppos = i;
 650         return tmp-buf;
 651 }
 652
 653 static ssize_t write_port(struct file * file, const char __user * buf,
 654                           size_t count, loff_t *ppos)
 655 {
 656         unsigned long i = *ppos;
 657         const char __user * tmp = buf;
 658
 659         if (!access_ok(VERIFY_READ,buf,count))
 660                 return -EFAULT;
 661         while (count-- > 0 && i < 65536) {
 662                 char c;
 663                 if (__get_user(c, tmp)) {
 664                         if (tmp > buf)
 665                                 break;
 666                         return -EFAULT;
 667                 }
 668                 outb(c,i);
 669                 i++;
 670                 tmp++;
 671         }
 672         *ppos = i;
 673         return tmp-buf;
 674 }
 675 #endif
 676
 677 static ssize_t read_null(struct file * file, char __user * buf,
 678                          size_t count, loff_t *ppos)
 679 {
 680         return 0;
 681 }
 682
 683 static ssize_t write_null(struct file * file, const char __user * buf,
 684                           size_t count, loff_t *ppos)
 685 {
 686         return count;
 687 }
 688
 689 static int pipe_to_null(struct pipe_inode_info *info, struct pipe_buffer *buf,
 690                         struct splice_desc *sd)
 691 {
 692         return sd->len;
 693 }
 694
 695 static ssize_t splice_write_null(struct pipe_inode_info *pipe,struct file *out,
 696                                  loff_t *ppos, size_t len, unsigned int flags)
 697 {
 698         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_null);
 699 }
 700
 701 static ssize_t read_zero(struct file * file, char __user * buf,
 702                          size_t count, loff_t *ppos)
 703 {
 704         size_t written;
 705
 706         if (!count)
 707                 return 0;
 708
 709         if (!access_ok(VERIFY_WRITE, buf, count))
 710                 return -EFAULT;
 711
 712         written = 0;
 713         while (count) {
 714                 unsigned long unwritten;
 715                 size_t chunk = count;
 716
 717                 if (chunk > PAGE_SIZE)
 718                         chunk = PAGE_SIZE;      /* Just for latency reasons */
 719                 unwritten = clear_user(buf, chunk);
 720                 written += chunk - unwritten;
 721                 if (unwritten)
 722                         break;
 723                 buf += chunk;
 724                 count -= chunk;
 725                 cond_resched();
 726         }
 727         return written ? written : -EFAULT;
 728 }
 729
 730 static int mmap_zero(struct file * file, struct vm_area_struct * vma)
 731 {
 732 #ifndef CONFIG_MMU
 733         return -ENOSYS;
 734 #endif
 735         if (vma->vm_flags & VM_SHARED)
 736                 return shmem_zero_setup(vma);
 737         return 0;
 738 }
 739
 740 static ssize_t write_full(struct file * file, const char __user * buf,
 741                           size_t count, loff_t *ppos)
 742 {
 743         return -ENOSPC;
 744 }
 745
 746 /*
 747  * Special lseek() function for /dev/null and /dev/zero.  Most notably, you
 748  * can fopen() both devices with "a" now.  This was previously impossible.
 749  * -- SRB.
 750  */
 751
 752 static loff_t null_lseek(struct file * file, loff_t offset, int orig)
 753 {
 754         return file->f_pos = 0;
 755 }
 756
 757 /*
 758  * The memory devices use the full 32/64 bits of the offset, and so we cannot
 759  * check against negative addresses: they are ok. The return value is weird,
 760  * though, in that case (0).
 761  *
 762  * also note that seeking relative to the "end of file" isn't supported:
 763  * it has no meaning, so it returns -EINVAL.
 764  */
 765 static loff_t memory_lseek(struct file * file, loff_t offset, int orig)
 766 {
 767         loff_t ret;
 768
 769         mutex_lock(&file->f_path.dentry->d_inode->i_mutex);
 770         switch (orig) {
 771                 case 0:
 772                         file->f_pos = offset;
 773                         ret = file->f_pos;
 774                         force_successful_syscall_return();
 775                         break;
 776                 case 1:
 777                         file->f_pos += offset;
 778                         ret = file->f_pos;
 779                         force_successful_syscall_return();
 780                         break;
 781                 default:
 782                         ret = -EINVAL;
 783         }
 784         mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
 785         return ret;
 786 }
 787
 788 static int open_port(struct inode * inode, struct file * filp)
 789 {
 790         return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
 791 }
 792
 793 #define zero_lseek      null_lseek
 794 #define full_lseek      null_lseek
 795 #define write_zero      write_null
 796 #define read_full       read_zero
 797 #define open_mem        open_port
 798 #define open_kmem       open_mem
 799 #define open_oldmem     open_mem
 800
 801 static const struct file_operations mem_fops = {
 802         .llseek         = memory_lseek,
 803         .read           = read_mem,
 804         .write          = write_mem,
 805         .mmap           = mmap_mem,
 806         .open           = open_mem,
 807         .get_unmapped_area = get_unmapped_area_mem,
 808 };
 809
 810 #ifdef CONFIG_DEVKMEM
 811 static const struct file_operations kmem_fops = {
 812         .llseek         = memory_lseek,
 813         .read           = read_kmem,
 814         .write          = write_kmem,
 815         .mmap           = mmap_kmem,
 816         .open           = open_kmem,
 817         .get_unmapped_area = get_unmapped_area_mem,
 818 };
 819 #endif
 820
 821 static const struct file_operations null_fops = {
 822         .llseek         = null_lseek,
 823         .read           = read_null,
 824         .write          = write_null,
 825         .splice_write   = splice_write_null,
 826 };
 827
 828 #ifdef CONFIG_DEVPORT
 829 static const struct file_operations port_fops = {
 830         .llseek         = memory_lseek,
 831         .read           = read_port,
 832         .write          = write_port,
 833         .open           = open_port,
 834 };
 835 #endif
 836
 837 static const struct file_operations zero_fops = {
 838         .llseek         = zero_lseek,
 839         .read           = read_zero,
 840         .write          = write_zero,
 841         .mmap           = mmap_zero,
 842 };
 843
 844 /*
 845  * capabilities for /dev/zero
 846  * - permits private mappings, "copies" are taken of the source of zeros
 847  */
 848 static struct backing_dev_info zero_bdi = {
 849         .capabilities   = BDI_CAP_MAP_COPY,
 850 };
 851
 852 static const struct file_operations full_fops = {
 853         .llseek         = full_lseek,
 854         .read           = read_full,
 855         .write          = write_full,
 856 };
 857
 858 #ifdef CONFIG_CRASH_DUMP
 859 static const struct file_operations oldmem_fops = {
 860         .read   = read_oldmem,
 861         .open   = open_oldmem,
 862 };
 863 #endif
 864
 865 static ssize_t kmsg_write(struct file * file, const char __user * buf,
 866                           size_t count, loff_t *ppos)
 867 {
 868         char *tmp;
 869         ssize_t ret;
 870
 871         tmp = kmalloc(count + 1, GFP_KERNEL);
 872         if (tmp == NULL)
 873                 return -ENOMEM;
 874         ret = -EFAULT;
 875         if (!copy_from_user(tmp, buf, count)) {
 876                 tmp[count] = 0;
 877                 ret = printk("%s", tmp);
 878                 if (ret > count)
 879                         /* printk can add a prefix */
 880                         ret = count;
 881         }
 882         kfree(tmp);
 883         return ret;
 884 }
 885
 886 static const struct file_operations kmsg_fops = {
 887         .write =        kmsg_write,
 888 };
 889
 890 static int memory_open(struct inode * inode, struct file * filp)
 891 {
 892         switch (iminor(inode)) {
 893                 case 1:
 894                         filp->f_op = &mem_fops;
 895                         filp->f_mapping->backing_dev_info =
 896                                 &directly_mappable_cdev_bdi;
 897                         break;
 898 #ifdef CONFIG_DEVKMEM
 899                 case 2:
 900                         filp->f_op = &kmem_fops;
 901                         filp->f_mapping->backing_dev_info =
 902                                 &directly_mappable_cdev_bdi;
 903                         break;
 904 #endif
 905                 case 3:
 906                         filp->f_op = &null_fops;
 907                         break;
 908 #ifdef CONFIG_DEVPORT
 909                 case 4:
 910                         filp->f_op = &port_fops;
 911                         break;
 912 #endif
 913                 case 5:
 914                         filp->f_mapping->backing_dev_info = &zero_bdi;
 915                         filp->f_op = &zero_fops;
 916                         break;
 917                 case 7:
 918                         filp->f_op = &full_fops;
 919                         break;
 920                 case 8:
 921                         filp->f_op = &random_fops;
 922                         break;
 923                 case 9:
 924                         filp->f_op = &urandom_fops;
 925                         break;
 926                 case 11:
 927                         filp->f_op = &kmsg_fops;
 928                         break;
 929 #ifdef CONFIG_CRASH_DUMP
 930                 case 12:
 931                         filp->f_op = &oldmem_fops;
 932                         break;
 933 #endif
 934                 default:
 935                         return -ENXIO;
 936         }
 937         if (filp->f_op && filp->f_op->open)
 938                 return filp->f_op->open(inode,filp);
 939         return 0;
 940 }
 941
 942 static const struct file_operations memory_fops = {
 943         .open           = memory_open,  /* just a selector for the real open */
 944 };
 945
 946 static const struct {
 947         unsigned int            minor;
 948         char                    *name;
 949         umode_t                 mode;
 950         const struct file_operations    *fops;
 951 } devlist[] = { /* list of minor devices */
 952         {1, "mem",     S_IRUSR | S_IWUSR | S_IRGRP, &mem_fops},
 953 #ifdef CONFIG_DEVKMEM
 954         {2, "kmem",    S_IRUSR | S_IWUSR | S_IRGRP, &kmem_fops},
 955 #endif
 956         {3, "null",    S_IRUGO | S_IWUGO,           &null_fops},
 957 #ifdef CONFIG_DEVPORT
 958         {4, "port",    S_IRUSR | S_IWUSR | S_IRGRP, &port_fops},
 959 #endif
 960         {5, "zero",    S_IRUGO | S_IWUGO,           &zero_fops},
 961         {7, "full",    S_IRUGO | S_IWUGO,           &full_fops},
 962         {8, "random",  S_IRUGO | S_IWUSR,           &random_fops},
 963         {9, "urandom", S_IRUGO | S_IWUSR,           &urandom_fops},
 964         {11,"kmsg",    S_IRUGO | S_IWUSR,           &kmsg_fops},
 965 #ifdef CONFIG_CRASH_DUMP
 966         {12,"oldmem",    S_IRUSR | S_IWUSR | S_IRGRP, &oldmem_fops},
 967 #endif
 968 };
 969
 970 static struct class *mem_class;
 971
 972 static int __init chr_dev_init(void)
 973 {
 974         int i;
 975         int err;
 976
 977         err = bdi_init(&zero_bdi);
 978         if (err)
 979                 return err;
 980
 981         if (register_chrdev(MEM_MAJOR,"mem",&memory_fops))
 982                 printk("unable to get major %d for memory devs\n", MEM_MAJOR);
 983
 984         mem_class = class_create(THIS_MODULE, "mem");
 985         for (i = 0; i < ARRAY_SIZE(devlist); i++)
 986                 device_create(mem_class, NULL,
 987                               MKDEV(MEM_MAJOR, devlist[i].minor),
 988                               devlist[i].name);
 989
 990         return 0;
 991 }
 992
 993 fs_initcall(chr_dev_init);