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 /*
  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_DSYNC 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_DSYNC will be done non-cached.
  60          */
  61         if (file->f_flags & O_DSYNC)
  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_STRICT_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 static const struct vm_operations_struct mmap_mem_ops = {
 304 #ifdef CONFIG_HAVE_IOREMAP_PROT
 305         .access = generic_access_phys
 306 #endif
 307 };
 308
 309 static int mmap_mem(struct file * file, struct vm_area_struct * vma)
 310 {
 311         size_t size = vma->vm_end - vma->vm_start;
 312
 313         if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))
 314                 return -EINVAL;
 315
 316         if (!private_mapping_ok(vma))
 317                 return -ENOSYS;
 318
 319         if (!range_is_allowed(vma->vm_pgoff, size))
 320                 return -EPERM;
 321
 322         if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size,
 323                                                 &vma->vm_page_prot))
 324                 return -EINVAL;
 325
 326         vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,
 327                                                  size,
 328                                                  vma->vm_page_prot);
 329
 330         vma->vm_ops = &mmap_mem_ops;
 331
 332         /* Remap-pfn-range will mark the range VM_IO and VM_RESERVED */
 333         if (remap_pfn_range(vma,
 334                             vma->vm_start,
 335                             vma->vm_pgoff,
 336                             size,
 337                             vma->vm_page_prot)) {
 338                 return -EAGAIN;
 339         }
 340         return 0;
 341 }
 342
 343 #ifdef CONFIG_DEVKMEM
 344 static int mmap_kmem(struct file * file, struct vm_area_struct * vma)
 345 {
 346         unsigned long pfn;
 347
 348         /* Turn a kernel-virtual address into a physical page frame */
 349         pfn = __pa((u64)vma->vm_pgoff << PAGE_SHIFT) >> PAGE_SHIFT;
 350
 351         /*
 352          * RED-PEN: on some architectures there is more mapped memory
 353          * than available in mem_map which pfn_valid checks
 354          * for. Perhaps should add a new macro here.
 355          *
 356          * RED-PEN: vmalloc is not supported right now.
 357          */
 358         if (!pfn_valid(pfn))
 359                 return -EIO;
 360
 361         vma->vm_pgoff = pfn;
 362         return mmap_mem(file, vma);
 363 }
 364 #endif
 365
 366 #ifdef CONFIG_CRASH_DUMP
 367 /*
 368  * Read memory corresponding to the old kernel.
 369  */
 370 static ssize_t read_oldmem(struct file *file, char __user *buf,
 371                                 size_t count, loff_t *ppos)
 372 {
 373         unsigned long pfn, offset;
 374         size_t read = 0, csize;
 375         int rc = 0;
 376
 377         while (count) {
 378                 pfn = *ppos / PAGE_SIZE;
 379                 if (pfn > saved_max_pfn)
 380                         return read;
 381
 382                 offset = (unsigned long)(*ppos % PAGE_SIZE);
 383                 if (count > PAGE_SIZE - offset)
 384                         csize = PAGE_SIZE - offset;
 385                 else
 386                         csize = count;
 387
 388                 rc = copy_oldmem_page(pfn, buf, csize, offset, 1);
 389                 if (rc < 0)
 390                         return rc;
 391                 buf += csize;
 392                 *ppos += csize;
 393                 read += csize;
 394                 count -= csize;
 395         }
 396         return read;
 397 }
 398 #endif
 399
 400 #ifdef CONFIG_DEVKMEM
 401 /*
 402  * This function reads the *virtual* memory as seen by the kernel.
 403  */
 404 static ssize_t read_kmem(struct file *file, char __user *buf,
 405                          size_t count, loff_t *ppos)
 406 {
 407         unsigned long p = *ppos;
 408         ssize_t low_count, read, sz;
 409         char * kbuf; /* k-addr because vread() takes vmlist_lock rwlock */
 410
 411         read = 0;
 412         if (p < (unsigned long) high_memory) {
 413                 low_count = count;
 414                 if (count > (unsigned long) high_memory - p)
 415                         low_count = (unsigned long) high_memory - p;
 416
 417 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 418                 /* we don't have page 0 mapped on sparc and m68k.. */
 419                 if (p < PAGE_SIZE && low_count > 0) {
 420                         size_t tmp = PAGE_SIZE - p;
 421                         if (tmp > low_count) tmp = low_count;
 422                         if (clear_user(buf, tmp))
 423                                 return -EFAULT;
 424                         buf += tmp;
 425                         p += tmp;
 426                         read += tmp;
 427                         low_count -= tmp;
 428                         count -= tmp;
 429                 }
 430 #endif
 431                 while (low_count > 0) {
 432                         /*
 433                          * Handle first page in case it's not aligned
 434                          */
 435                         if (-p & (PAGE_SIZE - 1))
 436                                 sz = -p & (PAGE_SIZE - 1);
 437                         else
 438                                 sz = PAGE_SIZE;
 439
 440                         sz = min_t(unsigned long, sz, low_count);
 441
 442                         /*
 443                          * On ia64 if a page has been mapped somewhere as
 444                          * uncached, then it must also be accessed uncached
 445                          * by the kernel or data corruption may occur
 446                          */
 447                         kbuf = xlate_dev_kmem_ptr((char *)p);
 448
 449                         if (copy_to_user(buf, kbuf, sz))
 450                                 return -EFAULT;
 451                         buf += sz;
 452                         p += sz;
 453                         read += sz;
 454                         low_count -= sz;
 455                         count -= sz;
 456                 }
 457         }
 458
 459         if (count > 0) {
 460                 kbuf = (char *)__get_free_page(GFP_KERNEL);
 461                 if (!kbuf)
 462                         return -ENOMEM;
 463                 while (count > 0) {
 464                         int len = count;
 465
 466                         if (len > PAGE_SIZE)
 467                                 len = PAGE_SIZE;
 468                         len = vread(kbuf, (char *)p, len);
 469                         if (!len)
 470                                 break;
 471                         if (copy_to_user(buf, kbuf, len)) {
 472                                 free_page((unsigned long)kbuf);
 473                                 return -EFAULT;
 474                         }
 475                         count -= len;
 476                         buf += len;
 477                         read += len;
 478                         p += len;
 479                 }
 480                 free_page((unsigned long)kbuf);
 481         }
 482         *ppos = p;
 483         return read;
 484 }
 485
 486
 487 static inline ssize_t
 488 do_write_kmem(void *p, unsigned long realp, const char __user * buf,
 489               size_t count, loff_t *ppos)
 490 {
 491         ssize_t written, sz;
 492         unsigned long copied;
 493
 494         written = 0;
 495 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 496         /* we don't have page 0 mapped on sparc and m68k.. */
 497         if (realp < PAGE_SIZE) {
 498                 unsigned long sz = PAGE_SIZE - realp;
 499                 if (sz > count)
 500                         sz = count;
 501                 /* Hmm. Do something? */
 502                 buf += sz;
 503                 p += sz;
 504                 realp += sz;
 505                 count -= sz;
 506                 written += sz;
 507         }
 508 #endif
 509
 510         while (count > 0) {
 511                 char *ptr;
 512                 /*
 513                  * Handle first page in case it's not aligned
 514                  */
 515                 if (-realp & (PAGE_SIZE - 1))
 516                         sz = -realp & (PAGE_SIZE - 1);
 517                 else
 518                         sz = PAGE_SIZE;
 519
 520                 sz = min_t(unsigned long, sz, count);
 521
 522                 /*
 523                  * On ia64 if a page has been mapped somewhere as
 524                  * uncached, then it must also be accessed uncached
 525                  * by the kernel or data corruption may occur
 526                  */
 527                 ptr = xlate_dev_kmem_ptr(p);
 528
 529                 copied = copy_from_user(ptr, buf, sz);
 530                 if (copied) {
 531                         written += sz - copied;
 532                         if (written)
 533                                 break;
 534                         return -EFAULT;
 535                 }
 536                 buf += sz;
 537                 p += sz;
 538                 realp += sz;
 539                 count -= sz;
 540                 written += sz;
 541         }
 542
 543         *ppos += written;
 544         return written;
 545 }
 546
 547
 548 /*
 549  * This function writes to the *virtual* memory as seen by the kernel.
 550  */
 551 static ssize_t write_kmem(struct file * file, const char __user * buf,
 552                           size_t count, loff_t *ppos)
 553 {
 554         unsigned long p = *ppos;
 555         ssize_t wrote = 0;
 556         ssize_t virtr = 0;
 557         ssize_t written;
 558         char * kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
 559
 560         if (p < (unsigned long) high_memory) {
 561
 562                 wrote = count;
 563                 if (count > (unsigned long) high_memory - p)
 564                         wrote = (unsigned long) high_memory - p;
 565
 566                 written = do_write_kmem((void*)p, p, buf, wrote, ppos);
 567                 if (written != wrote)
 568                         return written;
 569                 wrote = written;
 570                 p += wrote;
 571                 buf += wrote;
 572                 count -= wrote;
 573         }
 574
 575         if (count > 0) {
 576                 kbuf = (char *)__get_free_page(GFP_KERNEL);
 577                 if (!kbuf)
 578                         return wrote ? wrote : -ENOMEM;
 579                 while (count > 0) {
 580                         int len = count;
 581
 582                         if (len > PAGE_SIZE)
 583                                 len = PAGE_SIZE;
 584                         if (len) {
 585                                 written = copy_from_user(kbuf, buf, len);
 586                                 if (written) {
 587                                         if (wrote + virtr)
 588                                                 break;
 589                                         free_page((unsigned long)kbuf);
 590                                         return -EFAULT;
 591                                 }
 592                         }
 593                         len = vwrite(kbuf, (char *)p, len);
 594                         count -= len;
 595                         buf += len;
 596                         virtr += len;
 597                         p += len;
 598                 }
 599                 free_page((unsigned long)kbuf);
 600         }
 601
 602         *ppos = p;
 603         return virtr + wrote;
 604 }
 605 #endif
 606
 607 #ifdef CONFIG_DEVPORT
 608 static ssize_t read_port(struct file * file, char __user * buf,
 609                          size_t count, loff_t *ppos)
 610 {
 611         unsigned long i = *ppos;
 612         char __user *tmp = buf;
 613
 614         if (!access_ok(VERIFY_WRITE, buf, count))
 615                 return -EFAULT;
 616         while (count-- > 0 && i < 65536) {
 617                 if (__put_user(inb(i),tmp) < 0)
 618                         return -EFAULT;
 619                 i++;
 620                 tmp++;
 621         }
 622         *ppos = i;
 623         return tmp-buf;
 624 }
 625
 626 static ssize_t write_port(struct file * file, const char __user * buf,
 627                           size_t count, loff_t *ppos)
 628 {
 629         unsigned long i = *ppos;
 630         const char __user * tmp = buf;
 631
 632         if (!access_ok(VERIFY_READ,buf,count))
 633                 return -EFAULT;
 634         while (count-- > 0 && i < 65536) {
 635                 char c;
 636                 if (__get_user(c, tmp)) {
 637                         if (tmp > buf)
 638                                 break;
 639                         return -EFAULT;
 640                 }
 641                 outb(c,i);
 642                 i++;
 643                 tmp++;
 644         }
 645         *ppos = i;
 646         return tmp-buf;
 647 }
 648 #endif
 649
 650 static ssize_t read_null(struct file * file, char __user * buf,
 651                          size_t count, loff_t *ppos)
 652 {
 653         return 0;
 654 }
 655
 656 static ssize_t write_null(struct file * file, const char __user * buf,
 657                           size_t count, loff_t *ppos)
 658 {
 659         return count;
 660 }
 661
 662 static int pipe_to_null(struct pipe_inode_info *info, struct pipe_buffer *buf,
 663                         struct splice_desc *sd)
 664 {
 665         return sd->len;
 666 }
 667
 668 static ssize_t splice_write_null(struct pipe_inode_info *pipe,struct file *out,
 669                                  loff_t *ppos, size_t len, unsigned int flags)
 670 {
 671         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_null);
 672 }
 673
 674 static ssize_t read_zero(struct file * file, char __user * buf,
 675                          size_t count, loff_t *ppos)
 676 {
 677         size_t written;
 678
 679         if (!count)
 680                 return 0;
 681
 682         if (!access_ok(VERIFY_WRITE, buf, count))
 683                 return -EFAULT;
 684
 685         written = 0;
 686         while (count) {
 687                 unsigned long unwritten;
 688                 size_t chunk = count;
 689
 690                 if (chunk > PAGE_SIZE)
 691                         chunk = PAGE_SIZE;      /* Just for latency reasons */
 692                 unwritten = __clear_user(buf, chunk);
 693                 written += chunk - unwritten;
 694                 if (unwritten)
 695                         break;
 696                 if (signal_pending(current))
 697                         return written ? written : -ERESTARTSYS;
 698                 buf += chunk;
 699                 count -= chunk;
 700                 cond_resched();
 701         }
 702         return written ? written : -EFAULT;
 703 }
 704
 705 static int mmap_zero(struct file * file, struct vm_area_struct * vma)
 706 {
 707 #ifndef CONFIG_MMU
 708         return -ENOSYS;
 709 #endif
 710         if (vma->vm_flags & VM_SHARED)
 711                 return shmem_zero_setup(vma);
 712         return 0;
 713 }
 714
 715 static ssize_t write_full(struct file * file, const char __user * buf,
 716                           size_t count, loff_t *ppos)
 717 {
 718         return -ENOSPC;
 719 }
 720
 721 /*
 722  * Special lseek() function for /dev/null and /dev/zero.  Most notably, you
 723  * can fopen() both devices with "a" now.  This was previously impossible.
 724  * -- SRB.
 725  */
 726
 727 static loff_t null_lseek(struct file * file, loff_t offset, int orig)
 728 {
 729         return file->f_pos = 0;
 730 }
 731
 732 /*
 733  * The memory devices use the full 32/64 bits of the offset, and so we cannot
 734  * check against negative addresses: they are ok. The return value is weird,
 735  * though, in that case (0).
 736  *
 737  * also note that seeking relative to the "end of file" isn't supported:
 738  * it has no meaning, so it returns -EINVAL.
 739  */
 740 static loff_t memory_lseek(struct file * file, loff_t offset, int orig)
 741 {
 742         loff_t ret;
 743
 744         mutex_lock(&file->f_path.dentry->d_inode->i_mutex);
 745         switch (orig) {
 746                 case 0:
 747                         file->f_pos = offset;
 748                         ret = file->f_pos;
 749                         force_successful_syscall_return();
 750                         break;
 751                 case 1:
 752                         file->f_pos += offset;
 753                         ret = file->f_pos;
 754                         force_successful_syscall_return();
 755                         break;
 756                 default:
 757                         ret = -EINVAL;
 758         }
 759         mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
 760         return ret;
 761 }
 762
 763 static int open_port(struct inode * inode, struct file * filp)
 764 {
 765         return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
 766 }
 767
 768 #define zero_lseek      null_lseek
 769 #define full_lseek      null_lseek
 770 #define write_zero      write_null
 771 #define read_full       read_zero
 772 #define open_mem        open_port
 773 #define open_kmem       open_mem
 774 #define open_oldmem     open_mem
 775
 776 static const struct file_operations mem_fops = {
 777         .llseek         = memory_lseek,
 778         .read           = read_mem,
 779         .write          = write_mem,
 780         .mmap           = mmap_mem,
 781         .open           = open_mem,
 782         .get_unmapped_area = get_unmapped_area_mem,
 783 };
 784
 785 #ifdef CONFIG_DEVKMEM
 786 static const struct file_operations kmem_fops = {
 787         .llseek         = memory_lseek,
 788         .read           = read_kmem,
 789         .write          = write_kmem,
 790         .mmap           = mmap_kmem,
 791         .open           = open_kmem,
 792         .get_unmapped_area = get_unmapped_area_mem,
 793 };
 794 #endif
 795
 796 static const struct file_operations null_fops = {
 797         .llseek         = null_lseek,
 798         .read           = read_null,
 799         .write          = write_null,
 800         .splice_write   = splice_write_null,
 801 };
 802
 803 #ifdef CONFIG_DEVPORT
 804 static const struct file_operations port_fops = {
 805         .llseek         = memory_lseek,
 806         .read           = read_port,
 807         .write          = write_port,
 808         .open           = open_port,
 809 };
 810 #endif
 811
 812 static const struct file_operations zero_fops = {
 813         .llseek         = zero_lseek,
 814         .read           = read_zero,
 815         .write          = write_zero,
 816         .mmap           = mmap_zero,
 817 };
 818
 819 /*
 820  * capabilities for /dev/zero
 821  * - permits private mappings, "copies" are taken of the source of zeros
 822  */
 823 static struct backing_dev_info zero_bdi = {
 824         .name           = "char/mem",
 825         .capabilities   = BDI_CAP_MAP_COPY,
 826 };
 827
 828 static const struct file_operations full_fops = {
 829         .llseek         = full_lseek,
 830         .read           = read_full,
 831         .write          = write_full,
 832 };
 833
 834 #ifdef CONFIG_CRASH_DUMP
 835 static const struct file_operations oldmem_fops = {
 836         .read   = read_oldmem,
 837         .open   = open_oldmem,
 838 };
 839 #endif
 840
 841 static ssize_t kmsg_write(struct file * file, const char __user * buf,
 842                           size_t count, loff_t *ppos)
 843 {
 844         char *tmp;
 845         ssize_t ret;
 846
 847         tmp = kmalloc(count + 1, GFP_KERNEL);
 848         if (tmp == NULL)
 849                 return -ENOMEM;
 850         ret = -EFAULT;
 851         if (!copy_from_user(tmp, buf, count)) {
 852                 tmp[count] = 0;
 853                 ret = printk("%s", tmp);
 854                 if (ret > count)
 855                         /* printk can add a prefix */
 856                         ret = count;
 857         }
 858         kfree(tmp);
 859         return ret;
 860 }
 861
 862 static const struct file_operations kmsg_fops = {
 863         .write =        kmsg_write,
 864 };
 865
 866 static const struct memdev {
 867         const char *name;
 868         mode_t mode;
 869         const struct file_operations *fops;
 870         struct backing_dev_info *dev_info;
 871 } devlist[] = {
 872          [1] = { "mem", 0, &mem_fops, &directly_mappable_cdev_bdi },
 873 #ifdef CONFIG_DEVKMEM
 874          [2] = { "kmem", 0, &kmem_fops, &directly_mappable_cdev_bdi },
 875 #endif
 876          [3] = { "null", 0666, &null_fops, NULL },
 877 #ifdef CONFIG_DEVPORT
 878          [4] = { "port", 0, &port_fops, NULL },
 879 #endif
 880          [5] = { "zero", 0666, &zero_fops, &zero_bdi },
 881          [7] = { "full", 0666, &full_fops, NULL },
 882          [8] = { "random", 0666, &random_fops, NULL },
 883          [9] = { "urandom", 0666, &urandom_fops, NULL },
 884         [11] = { "kmsg", 0, &kmsg_fops, NULL },
 885 #ifdef CONFIG_CRASH_DUMP
 886         [12] = { "oldmem", 0, &oldmem_fops, NULL },
 887 #endif
 888 };
 889
 890 static int memory_open(struct inode *inode, struct file *filp)
 891 {
 892         int minor;
 893         const struct memdev *dev;
 894
 895         minor = iminor(inode);
 896         if (minor >= ARRAY_SIZE(devlist))
 897                 return -ENXIO;
 898
 899         dev = &devlist[minor];
 900         if (!dev->fops)
 901                 return -ENXIO;
 902
 903         filp->f_op = dev->fops;
 904         if (dev->dev_info)
 905                 filp->f_mapping->backing_dev_info = dev->dev_info;
 906
 907         if (dev->fops->open)
 908                 return dev->fops->open(inode, filp);
 909
 910         return 0;
 911 }
 912
 913 static const struct file_operations memory_fops = {
 914         .open           = memory_open,
 915 };
 916
 917 static char *mem_devnode(struct device *dev, mode_t *mode)
 918 {
 919         if (mode && devlist[MINOR(dev->devt)].mode)
 920                 *mode = devlist[MINOR(dev->devt)].mode;
 921         return NULL;
 922 }
 923
 924 static struct class *mem_class;
 925
 926 static int __init chr_dev_init(void)
 927 {
 928         int minor;
 929         int err;
 930
 931         err = bdi_init(&zero_bdi);
 932         if (err)
 933                 return err;
 934
 935         if (register_chrdev(MEM_MAJOR,"mem",&memory_fops))
 936                 printk("unable to get major %d for memory devs\n", MEM_MAJOR);
 937
 938         mem_class = class_create(THIS_MODULE, "mem");
 939         mem_class->devnode = mem_devnode;
 940         for (minor = 1; minor < ARRAY_SIZE(devlist); minor++) {
 941                 if (!devlist[minor].name)
 942                         continue;
 943                 device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor),
 944                               NULL, devlist[minor].name);
 945         }
 946
 947         return 0;
 948 }
 949
 950 fs_initcall(chr_dev_init);