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