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/backing-dev.h>
  25 #include <linux/splice.h>
  26 #include <linux/pfn.h>
  27 #include <linux/export.h>
  28 #include <linux/io.h>
  29 #include <linux/uio.h>
  30
  31 #include <linux/uaccess.h>
  32
  33 #ifdef CONFIG_IA64
  34 # include <linux/efi.h>
  35 #endif
  36
  37 #define DEVPORT_MINOR   4
  38
  39 static inline unsigned long size_inside_page(unsigned long start,
  40                                              unsigned long size)
  41 {
  42         unsigned long sz;
  43
  44         sz = PAGE_SIZE - (start & (PAGE_SIZE - 1));
  45
  46         return min(sz, size);
  47 }
  48
  49 #ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE
  50 static inline int valid_phys_addr_range(phys_addr_t addr, size_t count)
  51 {
  52         return addr + count <= __pa(high_memory);
  53 }
  54
  55 static inline int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
  56 {
  57         return 1;
  58 }
  59 #endif
  60
  61 #ifdef CONFIG_STRICT_DEVMEM
  62 static inline int range_is_allowed(unsigned long pfn, unsigned long size)
  63 {
  64         u64 from = ((u64)pfn) << PAGE_SHIFT;
  65         u64 to = from + size;
  66         u64 cursor = from;
  67
  68         while (cursor < to) {
  69                 if (!devmem_is_allowed(pfn)) {
  70                         printk(KERN_INFO
  71                 "Program %s tried to access /dev/mem between %Lx->%Lx.\n",
  72                                 current->comm, from, to);
  73                         return 0;
  74                 }
  75                 cursor += PAGE_SIZE;
  76                 pfn++;
  77         }
  78         return 1;
  79 }
  80 #else
  81 static inline int range_is_allowed(unsigned long pfn, unsigned long size)
  82 {
  83         return 1;
  84 }
  85 #endif
  86
  87 #ifndef unxlate_dev_mem_ptr
  88 #define unxlate_dev_mem_ptr unxlate_dev_mem_ptr
  89 void __weak unxlate_dev_mem_ptr(phys_addr_t phys, void *addr)
  90 {
  91 }
  92 #endif
  93
  94 /*
  95  * This funcion reads the *physical* memory. The f_pos points directly to the
  96  * memory location.
  97  */
  98 static ssize_t read_mem(struct file *file, char __user *buf,
  99                         size_t count, loff_t *ppos)
 100 {
 101         phys_addr_t p = *ppos;
 102         ssize_t read, sz;
 103         void *ptr;
 104
 105         if (p != *ppos)
 106                 return 0;
 107
 108         if (!valid_phys_addr_range(p, count))
 109                 return -EFAULT;
 110         read = 0;
 111 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 112         /* we don't have page 0 mapped on sparc and m68k.. */
 113         if (p < PAGE_SIZE) {
 114                 sz = size_inside_page(p, count);
 115                 if (sz > 0) {
 116                         if (clear_user(buf, sz))
 117                                 return -EFAULT;
 118                         buf += sz;
 119                         p += sz;
 120                         count -= sz;
 121                         read += sz;
 122                 }
 123         }
 124 #endif
 125
 126         while (count > 0) {
 127                 unsigned long remaining;
 128
 129                 sz = size_inside_page(p, count);
 130
 131                 if (!range_is_allowed(p >> PAGE_SHIFT, count))
 132                         return -EPERM;
 133
 134                 /*
 135                  * On ia64 if a page has been mapped somewhere as uncached, then
 136                  * it must also be accessed uncached by the kernel or data
 137                  * corruption may occur.
 138                  */
 139                 ptr = xlate_dev_mem_ptr(p);
 140                 if (!ptr)
 141                         return -EFAULT;
 142
 143                 remaining = copy_to_user(buf, ptr, sz);
 144                 unxlate_dev_mem_ptr(p, ptr);
 145                 if (remaining)
 146                         return -EFAULT;
 147
 148                 buf += sz;
 149                 p += sz;
 150                 count -= sz;
 151                 read += sz;
 152         }
 153
 154         *ppos += read;
 155         return read;
 156 }
 157
 158 static ssize_t write_mem(struct file *file, const char __user *buf,
 159                          size_t count, loff_t *ppos)
 160 {
 161         phys_addr_t p = *ppos;
 162         ssize_t written, sz;
 163         unsigned long copied;
 164         void *ptr;
 165
 166         if (p != *ppos)
 167                 return -EFBIG;
 168
 169         if (!valid_phys_addr_range(p, count))
 170                 return -EFAULT;
 171
 172         written = 0;
 173
 174 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 175         /* we don't have page 0 mapped on sparc and m68k.. */
 176         if (p < PAGE_SIZE) {
 177                 sz = size_inside_page(p, count);
 178                 /* Hmm. Do something? */
 179                 buf += sz;
 180                 p += sz;
 181                 count -= sz;
 182                 written += sz;
 183         }
 184 #endif
 185
 186         while (count > 0) {
 187                 sz = size_inside_page(p, count);
 188
 189                 if (!range_is_allowed(p >> PAGE_SHIFT, sz))
 190                         return -EPERM;
 191
 192                 /*
 193                  * On ia64 if a page has been mapped somewhere as uncached, then
 194                  * it must also be accessed uncached by the kernel or data
 195                  * corruption may occur.
 196                  */
 197                 ptr = xlate_dev_mem_ptr(p);
 198                 if (!ptr) {
 199                         if (written)
 200                                 break;
 201                         return -EFAULT;
 202                 }
 203
 204                 copied = copy_from_user(ptr, buf, sz);
 205                 unxlate_dev_mem_ptr(p, ptr);
 206                 if (copied) {
 207                         written += sz - copied;
 208                         if (written)
 209                                 break;
 210                         return -EFAULT;
 211                 }
 212
 213                 buf += sz;
 214                 p += sz;
 215                 count -= sz;
 216                 written += sz;
 217         }
 218
 219         *ppos += written;
 220         return written;
 221 }
 222
 223 int __weak phys_mem_access_prot_allowed(struct file *file,
 224         unsigned long pfn, unsigned long size, pgprot_t *vma_prot)
 225 {
 226         return 1;
 227 }
 228
 229 #ifndef __HAVE_PHYS_MEM_ACCESS_PROT
 230
 231 /*
 232  * Architectures vary in how they handle caching for addresses
 233  * outside of main memory.
 234  *
 235  */
 236 #ifdef pgprot_noncached
 237 static int uncached_access(struct file *file, phys_addr_t addr)
 238 {
 239 #if defined(CONFIG_IA64)
 240         /*
 241          * On ia64, we ignore O_DSYNC because we cannot tolerate memory
 242          * attribute aliases.
 243          */
 244         return !(efi_mem_attributes(addr) & EFI_MEMORY_WB);
 245 #elif defined(CONFIG_MIPS)
 246         {
 247                 extern int __uncached_access(struct file *file,
 248                                              unsigned long addr);
 249
 250                 return __uncached_access(file, addr);
 251         }
 252 #else
 253         /*
 254          * Accessing memory above the top the kernel knows about or through a
 255          * file pointer
 256          * that was marked O_DSYNC will be done non-cached.
 257          */
 258         if (file->f_flags & O_DSYNC)
 259                 return 1;
 260         return addr >= __pa(high_memory);
 261 #endif
 262 }
 263 #endif
 264
 265 static pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 266                                      unsigned long size, pgprot_t vma_prot)
 267 {
 268 #ifdef pgprot_noncached
 269         phys_addr_t offset = pfn << PAGE_SHIFT;
 270
 271         if (uncached_access(file, offset))
 272                 return pgprot_noncached(vma_prot);
 273 #endif
 274         return vma_prot;
 275 }
 276 #endif
 277
 278 #ifndef CONFIG_MMU
 279 static unsigned long get_unmapped_area_mem(struct file *file,
 280                                            unsigned long addr,
 281                                            unsigned long len,
 282                                            unsigned long pgoff,
 283                                            unsigned long flags)
 284 {
 285         if (!valid_mmap_phys_addr_range(pgoff, len))
 286                 return (unsigned long) -EINVAL;
 287         return pgoff << PAGE_SHIFT;
 288 }
 289
 290 /* permit direct mmap, for read, write or exec */
 291 static unsigned memory_mmap_capabilities(struct file *file)
 292 {
 293         return NOMMU_MAP_DIRECT |
 294                 NOMMU_MAP_READ | NOMMU_MAP_WRITE | NOMMU_MAP_EXEC;
 295 }
 296
 297 static unsigned zero_mmap_capabilities(struct file *file)
 298 {
 299         return NOMMU_MAP_COPY;
 300 }
 301
 302 /* can't do an in-place private mapping if there's no MMU */
 303 static inline int private_mapping_ok(struct vm_area_struct *vma)
 304 {
 305         return vma->vm_flags & VM_MAYSHARE;
 306 }
 307 #else
 308
 309 static inline int private_mapping_ok(struct vm_area_struct *vma)
 310 {
 311         return 1;
 312 }
 313 #endif
 314
 315 static const struct vm_operations_struct mmap_mem_ops = {
 316 #ifdef CONFIG_HAVE_IOREMAP_PROT
 317         .access = generic_access_phys
 318 #endif
 319 };
 320
 321 static int mmap_mem(struct file *file, struct vm_area_struct *vma)
 322 {
 323         size_t size = vma->vm_end - vma->vm_start;
 324
 325         if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))
 326                 return -EINVAL;
 327
 328         if (!private_mapping_ok(vma))
 329                 return -ENOSYS;
 330
 331         if (!range_is_allowed(vma->vm_pgoff, size))
 332                 return -EPERM;
 333
 334         if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size,
 335                                                 &vma->vm_page_prot))
 336                 return -EINVAL;
 337
 338         vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,
 339                                                  size,
 340                                                  vma->vm_page_prot);
 341
 342         vma->vm_ops = &mmap_mem_ops;
 343
 344         /* Remap-pfn-range will mark the range VM_IO */
 345         if (remap_pfn_range(vma,
 346                             vma->vm_start,
 347                             vma->vm_pgoff,
 348                             size,
 349                             vma->vm_page_prot)) {
 350                 return -EAGAIN;
 351         }
 352         return 0;
 353 }
 354
 355 static int mmap_kmem(struct file *file, struct vm_area_struct *vma)
 356 {
 357         unsigned long pfn;
 358
 359         /* Turn a kernel-virtual address into a physical page frame */
 360         pfn = __pa((u64)vma->vm_pgoff << PAGE_SHIFT) >> PAGE_SHIFT;
 361
 362         /*
 363          * RED-PEN: on some architectures there is more mapped memory than
 364          * available in mem_map which pfn_valid checks for. Perhaps should add a
 365          * new macro here.
 366          *
 367          * RED-PEN: vmalloc is not supported right now.
 368          */
 369         if (!pfn_valid(pfn))
 370                 return -EIO;
 371
 372         vma->vm_pgoff = pfn;
 373         return mmap_mem(file, vma);
 374 }
 375
 376 /*
 377  * This function reads the *virtual* memory as seen by the kernel.
 378  */
 379 static ssize_t read_kmem(struct file *file, char __user *buf,
 380                          size_t count, loff_t *ppos)
 381 {
 382         unsigned long p = *ppos;
 383         ssize_t low_count, read, sz;
 384         char *kbuf; /* k-addr because vread() takes vmlist_lock rwlock */
 385         int err = 0;
 386
 387         read = 0;
 388         if (p < (unsigned long) high_memory) {
 389                 low_count = count;
 390                 if (count > (unsigned long)high_memory - p)
 391                         low_count = (unsigned long)high_memory - p;
 392
 393 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 394                 /* we don't have page 0 mapped on sparc and m68k.. */
 395                 if (p < PAGE_SIZE && low_count > 0) {
 396                         sz = size_inside_page(p, low_count);
 397                         if (clear_user(buf, sz))
 398                                 return -EFAULT;
 399                         buf += sz;
 400                         p += sz;
 401                         read += sz;
 402                         low_count -= sz;
 403                         count -= sz;
 404                 }
 405 #endif
 406                 while (low_count > 0) {
 407                         sz = size_inside_page(p, low_count);
 408
 409                         /*
 410                          * On ia64 if a page has been mapped somewhere as
 411                          * uncached, then it must also be accessed uncached
 412                          * by the kernel or data corruption may occur
 413                          */
 414                         kbuf = xlate_dev_kmem_ptr((void *)p);
 415
 416                         if (copy_to_user(buf, kbuf, sz))
 417                                 return -EFAULT;
 418                         buf += sz;
 419                         p += sz;
 420                         read += sz;
 421                         low_count -= sz;
 422                         count -= sz;
 423                 }
 424         }
 425
 426         if (count > 0) {
 427                 kbuf = (char *)__get_free_page(GFP_KERNEL);
 428                 if (!kbuf)
 429                         return -ENOMEM;
 430                 while (count > 0) {
 431                         sz = size_inside_page(p, count);
 432                         if (!is_vmalloc_or_module_addr((void *)p)) {
 433                                 err = -ENXIO;
 434                                 break;
 435                         }
 436                         sz = vread(kbuf, (char *)p, sz);
 437                         if (!sz)
 438                                 break;
 439                         if (copy_to_user(buf, kbuf, sz)) {
 440                                 err = -EFAULT;
 441                                 break;
 442                         }
 443                         count -= sz;
 444                         buf += sz;
 445                         read += sz;
 446                         p += sz;
 447                 }
 448                 free_page((unsigned long)kbuf);
 449         }
 450         *ppos = p;
 451         return read ? read : err;
 452 }
 453
 454
 455 static ssize_t do_write_kmem(unsigned long p, const char __user *buf,
 456                                 size_t count, loff_t *ppos)
 457 {
 458         ssize_t written, sz;
 459         unsigned long copied;
 460
 461         written = 0;
 462 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 463         /* we don't have page 0 mapped on sparc and m68k.. */
 464         if (p < PAGE_SIZE) {
 465                 sz = size_inside_page(p, count);
 466                 /* Hmm. Do something? */
 467                 buf += sz;
 468                 p += sz;
 469                 count -= sz;
 470                 written += sz;
 471         }
 472 #endif
 473
 474         while (count > 0) {
 475                 void *ptr;
 476
 477                 sz = size_inside_page(p, count);
 478
 479                 /*
 480                  * On ia64 if a page has been mapped somewhere as uncached, then
 481                  * it must also be accessed uncached by the kernel or data
 482                  * corruption may occur.
 483                  */
 484                 ptr = xlate_dev_kmem_ptr((void *)p);
 485
 486                 copied = copy_from_user(ptr, buf, sz);
 487                 if (copied) {
 488                         written += sz - copied;
 489                         if (written)
 490                                 break;
 491                         return -EFAULT;
 492                 }
 493                 buf += sz;
 494                 p += sz;
 495                 count -= sz;
 496                 written += sz;
 497         }
 498
 499         *ppos += written;
 500         return written;
 501 }
 502
 503 /*
 504  * This function writes to the *virtual* memory as seen by the kernel.
 505  */
 506 static ssize_t write_kmem(struct file *file, const char __user *buf,
 507                           size_t count, loff_t *ppos)
 508 {
 509         unsigned long p = *ppos;
 510         ssize_t wrote = 0;
 511         ssize_t virtr = 0;
 512         char *kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
 513         int err = 0;
 514
 515         if (p < (unsigned long) high_memory) {
 516                 unsigned long to_write = min_t(unsigned long, count,
 517                                                (unsigned long)high_memory - p);
 518                 wrote = do_write_kmem(p, buf, to_write, ppos);
 519                 if (wrote != to_write)
 520                         return wrote;
 521                 p += wrote;
 522                 buf += wrote;
 523                 count -= wrote;
 524         }
 525
 526         if (count > 0) {
 527                 kbuf = (char *)__get_free_page(GFP_KERNEL);
 528                 if (!kbuf)
 529                         return wrote ? wrote : -ENOMEM;
 530                 while (count > 0) {
 531                         unsigned long sz = size_inside_page(p, count);
 532                         unsigned long n;
 533
 534                         if (!is_vmalloc_or_module_addr((void *)p)) {
 535                                 err = -ENXIO;
 536                                 break;
 537                         }
 538                         n = copy_from_user(kbuf, buf, sz);
 539                         if (n) {
 540                                 err = -EFAULT;
 541                                 break;
 542                         }
 543                         vwrite(kbuf, (char *)p, sz);
 544                         count -= sz;
 545                         buf += sz;
 546                         virtr += sz;
 547                         p += sz;
 548                 }
 549                 free_page((unsigned long)kbuf);
 550         }
 551
 552         *ppos = p;
 553         return virtr + wrote ? : err;
 554 }
 555
 556 static ssize_t read_port(struct file *file, char __user *buf,
 557                          size_t count, loff_t *ppos)
 558 {
 559         unsigned long i = *ppos;
 560         char __user *tmp = buf;
 561
 562         if (!access_ok(VERIFY_WRITE, buf, count))
 563                 return -EFAULT;
 564         while (count-- > 0 && i < 65536) {
 565                 if (__put_user(inb(i), tmp) < 0)
 566                         return -EFAULT;
 567                 i++;
 568                 tmp++;
 569         }
 570         *ppos = i;
 571         return tmp-buf;
 572 }
 573
 574 static ssize_t write_port(struct file *file, const char __user *buf,
 575                           size_t count, loff_t *ppos)
 576 {
 577         unsigned long i = *ppos;
 578         const char __user *tmp = buf;
 579
 580         if (!access_ok(VERIFY_READ, buf, count))
 581                 return -EFAULT;
 582         while (count-- > 0 && i < 65536) {
 583                 char c;
 584
 585                 if (__get_user(c, tmp)) {
 586                         if (tmp > buf)
 587                                 break;
 588                         return -EFAULT;
 589                 }
 590                 outb(c, i);
 591                 i++;
 592                 tmp++;
 593         }
 594         *ppos = i;
 595         return tmp-buf;
 596 }
 597
 598 static ssize_t read_null(struct file *file, char __user *buf,
 599                          size_t count, loff_t *ppos)
 600 {
 601         return 0;
 602 }
 603
 604 static ssize_t write_null(struct file *file, const char __user *buf,
 605                           size_t count, loff_t *ppos)
 606 {
 607         return count;
 608 }
 609
 610 static ssize_t read_iter_null(struct kiocb *iocb, struct iov_iter *to)
 611 {
 612         return 0;
 613 }
 614
 615 static ssize_t write_iter_null(struct kiocb *iocb, struct iov_iter *from)
 616 {
 617         size_t count = iov_iter_count(from);
 618         iov_iter_advance(from, count);
 619         return count;
 620 }
 621
 622 static int pipe_to_null(struct pipe_inode_info *info, struct pipe_buffer *buf,
 623                         struct splice_desc *sd)
 624 {
 625         return sd->len;
 626 }
 627
 628 static ssize_t splice_write_null(struct pipe_inode_info *pipe, struct file *out,
 629                                  loff_t *ppos, size_t len, unsigned int flags)
 630 {
 631         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_null);
 632 }
 633
 634 static ssize_t read_iter_zero(struct kiocb *iocb, struct iov_iter *iter)
 635 {
 636         size_t written = 0;
 637
 638         while (iov_iter_count(iter)) {
 639                 size_t chunk = iov_iter_count(iter), n;
 640
 641                 if (chunk > PAGE_SIZE)
 642                         chunk = PAGE_SIZE;      /* Just for latency reasons */
 643                 n = iov_iter_zero(chunk, iter);
 644                 if (!n && iov_iter_count(iter))
 645                         return written ? written : -EFAULT;
 646                 written += n;
 647                 if (signal_pending(current))
 648                         return written ? written : -ERESTARTSYS;
 649                 cond_resched();
 650         }
 651         return written;
 652 }
 653
 654 static int mmap_zero(struct file *file, struct vm_area_struct *vma)
 655 {
 656 #ifndef CONFIG_MMU
 657         return -ENOSYS;
 658 #endif
 659         if (vma->vm_flags & VM_SHARED)
 660                 return shmem_zero_setup(vma);
 661         return 0;
 662 }
 663
 664 static ssize_t write_full(struct file *file, const char __user *buf,
 665                           size_t count, loff_t *ppos)
 666 {
 667         return -ENOSPC;
 668 }
 669
 670 /*
 671  * Special lseek() function for /dev/null and /dev/zero.  Most notably, you
 672  * can fopen() both devices with "a" now.  This was previously impossible.
 673  * -- SRB.
 674  */
 675 static loff_t null_lseek(struct file *file, loff_t offset, int orig)
 676 {
 677         return file->f_pos = 0;
 678 }
 679
 680 /*
 681  * The memory devices use the full 32/64 bits of the offset, and so we cannot
 682  * check against negative addresses: they are ok. The return value is weird,
 683  * though, in that case (0).
 684  *
 685  * also note that seeking relative to the "end of file" isn't supported:
 686  * it has no meaning, so it returns -EINVAL.
 687  */
 688 static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
 689 {
 690         loff_t ret;
 691
 692         mutex_lock(&file_inode(file)->i_mutex);
 693         switch (orig) {
 694         case SEEK_CUR:
 695                 offset += file->f_pos;
 696         case SEEK_SET:
 697                 /* to avoid userland mistaking f_pos=-9 as -EBADF=-9 */
 698                 if (IS_ERR_VALUE((unsigned long long)offset)) {
 699                         ret = -EOVERFLOW;
 700                         break;
 701                 }
 702                 file->f_pos = offset;
 703                 ret = file->f_pos;
 704                 force_successful_syscall_return();
 705                 break;
 706         default:
 707                 ret = -EINVAL;
 708         }
 709         mutex_unlock(&file_inode(file)->i_mutex);
 710         return ret;
 711 }
 712
 713 static int open_port(struct inode *inode, struct file *filp)
 714 {
 715         return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
 716 }
 717
 718 #define zero_lseek      null_lseek
 719 #define full_lseek      null_lseek
 720 #define write_zero      write_null
 721 #define write_iter_zero write_iter_null
 722 #define open_mem        open_port
 723 #define open_kmem       open_mem
 724
 725 static const struct file_operations __maybe_unused mem_fops = {
 726         .llseek         = memory_lseek,
 727         .read           = read_mem,
 728         .write          = write_mem,
 729         .mmap           = mmap_mem,
 730         .open           = open_mem,
 731 #ifndef CONFIG_MMU
 732         .get_unmapped_area = get_unmapped_area_mem,
 733         .mmap_capabilities = memory_mmap_capabilities,
 734 #endif
 735 };
 736
 737 static const struct file_operations __maybe_unused kmem_fops = {
 738         .llseek         = memory_lseek,
 739         .read           = read_kmem,
 740         .write          = write_kmem,
 741         .mmap           = mmap_kmem,
 742         .open           = open_kmem,
 743 #ifndef CONFIG_MMU
 744         .get_unmapped_area = get_unmapped_area_mem,
 745         .mmap_capabilities = memory_mmap_capabilities,
 746 #endif
 747 };
 748
 749 static const struct file_operations null_fops = {
 750         .llseek         = null_lseek,
 751         .read           = read_null,
 752         .write          = write_null,
 753         .read_iter      = read_iter_null,
 754         .write_iter     = write_iter_null,
 755         .splice_write   = splice_write_null,
 756 };
 757
 758 static const struct file_operations __maybe_unused port_fops = {
 759         .llseek         = memory_lseek,
 760         .read           = read_port,
 761         .write          = write_port,
 762         .open           = open_port,
 763 };
 764
 765 static const struct file_operations zero_fops = {
 766         .llseek         = zero_lseek,
 767         .write          = write_zero,
 768         .read_iter      = read_iter_zero,
 769         .write_iter     = write_iter_zero,
 770         .mmap           = mmap_zero,
 771 #ifndef CONFIG_MMU
 772         .mmap_capabilities = zero_mmap_capabilities,
 773 #endif
 774 };
 775
 776 static const struct file_operations full_fops = {
 777         .llseek         = full_lseek,
 778         .read_iter      = read_iter_zero,
 779         .write          = write_full,
 780 };
 781
 782 static const struct memdev {
 783         const char *name;
 784         umode_t mode;
 785         const struct file_operations *fops;
 786         fmode_t fmode;
 787 } devlist[] = {
 788 #ifdef CONFIG_DEVMEM
 789          [1] = { "mem", 0, &mem_fops, FMODE_UNSIGNED_OFFSET },
 790 #endif
 791 #ifdef CONFIG_DEVKMEM
 792          [2] = { "kmem", 0, &kmem_fops, FMODE_UNSIGNED_OFFSET },
 793 #endif
 794          [3] = { "null", 0666, &null_fops, 0 },
 795 #ifdef CONFIG_DEVPORT
 796          [4] = { "port", 0, &port_fops, 0 },
 797 #endif
 798          [5] = { "zero", 0666, &zero_fops, 0 },
 799          [7] = { "full", 0666, &full_fops, 0 },
 800          [8] = { "random", 0666, &random_fops, 0 },
 801          [9] = { "urandom", 0666, &urandom_fops, 0 },
 802 #ifdef CONFIG_PRINTK
 803         [11] = { "kmsg", 0644, &kmsg_fops, 0 },
 804 #endif
 805 };
 806
 807 static int memory_open(struct inode *inode, struct file *filp)
 808 {
 809         int minor;
 810         const struct memdev *dev;
 811
 812         minor = iminor(inode);
 813         if (minor >= ARRAY_SIZE(devlist))
 814                 return -ENXIO;
 815
 816         dev = &devlist[minor];
 817         if (!dev->fops)
 818                 return -ENXIO;
 819
 820         filp->f_op = dev->fops;
 821         filp->f_mode |= dev->fmode;
 822
 823         if (dev->fops->open)
 824                 return dev->fops->open(inode, filp);
 825
 826         return 0;
 827 }
 828
 829 static const struct file_operations memory_fops = {
 830         .open = memory_open,
 831         .llseek = noop_llseek,
 832 };
 833
 834 static char *mem_devnode(struct device *dev, umode_t *mode)
 835 {
 836         if (mode && devlist[MINOR(dev->devt)].mode)
 837                 *mode = devlist[MINOR(dev->devt)].mode;
 838         return NULL;
 839 }
 840
 841 static struct class *mem_class;
 842
 843 static int __init chr_dev_init(void)
 844 {
 845         int minor;
 846
 847         if (register_chrdev(MEM_MAJOR, "mem", &memory_fops))
 848                 printk("unable to get major %d for memory devs\n", MEM_MAJOR);
 849
 850         mem_class = class_create(THIS_MODULE, "mem");
 851         if (IS_ERR(mem_class))
 852                 return PTR_ERR(mem_class);
 853
 854         mem_class->devnode = mem_devnode;
 855         for (minor = 1; minor < ARRAY_SIZE(devlist); minor++) {
 856                 if (!devlist[minor].name)
 857                         continue;
 858
 859                 /*
 860                  * Create /dev/port?
 861                  */
 862                 if ((minor == DEVPORT_MINOR) && !arch_has_dev_port())
 863                         continue;
 864
 865                 device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor),
 866                               NULL, devlist[minor].name);
 867         }
 868
 869         return tty_init();
 870 }
 871
 872 fs_initcall(chr_dev_init);