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/aio.h>
  30
  31 #include <asm/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 #ifdef CONFIG_DEVKMEM
 356 static int mmap_kmem(struct file *file, struct vm_area_struct *vma)
 357 {
 358         unsigned long pfn;
 359
 360         /* Turn a kernel-virtual address into a physical page frame */
 361         pfn = __pa((u64)vma->vm_pgoff << PAGE_SHIFT) >> PAGE_SHIFT;
 362
 363         /*
 364          * RED-PEN: on some architectures there is more mapped memory than
 365          * available in mem_map which pfn_valid checks for. Perhaps should add a
 366          * new macro here.
 367          *
 368          * RED-PEN: vmalloc is not supported right now.
 369          */
 370         if (!pfn_valid(pfn))
 371                 return -EIO;
 372
 373         vma->vm_pgoff = pfn;
 374         return mmap_mem(file, vma);
 375 }
 376 #endif
 377
 378 #ifdef CONFIG_DEVKMEM
 379 /*
 380  * This function reads the *virtual* memory as seen by the kernel.
 381  */
 382 static ssize_t read_kmem(struct file *file, char __user *buf,
 383                          size_t count, loff_t *ppos)
 384 {
 385         unsigned long p = *ppos;
 386         ssize_t low_count, read, sz;
 387         char *kbuf; /* k-addr because vread() takes vmlist_lock rwlock */
 388         int err = 0;
 389
 390         read = 0;
 391         if (p < (unsigned long) high_memory) {
 392                 low_count = count;
 393                 if (count > (unsigned long)high_memory - p)
 394                         low_count = (unsigned long)high_memory - p;
 395
 396 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 397                 /* we don't have page 0 mapped on sparc and m68k.. */
 398                 if (p < PAGE_SIZE && low_count > 0) {
 399                         sz = size_inside_page(p, low_count);
 400                         if (clear_user(buf, sz))
 401                                 return -EFAULT;
 402                         buf += sz;
 403                         p += sz;
 404                         read += sz;
 405                         low_count -= sz;
 406                         count -= sz;
 407                 }
 408 #endif
 409                 while (low_count > 0) {
 410                         sz = size_inside_page(p, low_count);
 411
 412                         /*
 413                          * On ia64 if a page has been mapped somewhere as
 414                          * uncached, then it must also be accessed uncached
 415                          * by the kernel or data corruption may occur
 416                          */
 417                         kbuf = xlate_dev_kmem_ptr((void *)p);
 418
 419                         if (copy_to_user(buf, kbuf, sz))
 420                                 return -EFAULT;
 421                         buf += sz;
 422                         p += sz;
 423                         read += sz;
 424                         low_count -= sz;
 425                         count -= sz;
 426                 }
 427         }
 428
 429         if (count > 0) {
 430                 kbuf = (char *)__get_free_page(GFP_KERNEL);
 431                 if (!kbuf)
 432                         return -ENOMEM;
 433                 while (count > 0) {
 434                         sz = size_inside_page(p, count);
 435                         if (!is_vmalloc_or_module_addr((void *)p)) {
 436                                 err = -ENXIO;
 437                                 break;
 438                         }
 439                         sz = vread(kbuf, (char *)p, sz);
 440                         if (!sz)
 441                                 break;
 442                         if (copy_to_user(buf, kbuf, sz)) {
 443                                 err = -EFAULT;
 444                                 break;
 445                         }
 446                         count -= sz;
 447                         buf += sz;
 448                         read += sz;
 449                         p += sz;
 450                 }
 451                 free_page((unsigned long)kbuf);
 452         }
 453         *ppos = p;
 454         return read ? read : err;
 455 }
 456
 457
 458 static ssize_t do_write_kmem(unsigned long p, const char __user *buf,
 459                                 size_t count, loff_t *ppos)
 460 {
 461         ssize_t written, sz;
 462         unsigned long copied;
 463
 464         written = 0;
 465 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 466         /* we don't have page 0 mapped on sparc and m68k.. */
 467         if (p < PAGE_SIZE) {
 468                 sz = size_inside_page(p, count);
 469                 /* Hmm. Do something? */
 470                 buf += sz;
 471                 p += sz;
 472                 count -= sz;
 473                 written += sz;
 474         }
 475 #endif
 476
 477         while (count > 0) {
 478                 void *ptr;
 479
 480                 sz = size_inside_page(p, count);
 481
 482                 /*
 483                  * On ia64 if a page has been mapped somewhere as uncached, then
 484                  * it must also be accessed uncached by the kernel or data
 485                  * corruption may occur.
 486                  */
 487                 ptr = xlate_dev_kmem_ptr((void *)p);
 488
 489                 copied = copy_from_user(ptr, buf, sz);
 490                 if (copied) {
 491                         written += sz - copied;
 492                         if (written)
 493                                 break;
 494                         return -EFAULT;
 495                 }
 496                 buf += sz;
 497                 p += sz;
 498                 count -= sz;
 499                 written += sz;
 500         }
 501
 502         *ppos += written;
 503         return written;
 504 }
 505
 506 /*
 507  * This function writes to the *virtual* memory as seen by the kernel.
 508  */
 509 static ssize_t write_kmem(struct file *file, const char __user *buf,
 510                           size_t count, loff_t *ppos)
 511 {
 512         unsigned long p = *ppos;
 513         ssize_t wrote = 0;
 514         ssize_t virtr = 0;
 515         char *kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
 516         int err = 0;
 517
 518         if (p < (unsigned long) high_memory) {
 519                 unsigned long to_write = min_t(unsigned long, count,
 520                                                (unsigned long)high_memory - p);
 521                 wrote = do_write_kmem(p, buf, to_write, ppos);
 522                 if (wrote != to_write)
 523                         return wrote;
 524                 p += wrote;
 525                 buf += wrote;
 526                 count -= wrote;
 527         }
 528
 529         if (count > 0) {
 530                 kbuf = (char *)__get_free_page(GFP_KERNEL);
 531                 if (!kbuf)
 532                         return wrote ? wrote : -ENOMEM;
 533                 while (count > 0) {
 534                         unsigned long sz = size_inside_page(p, count);
 535                         unsigned long n;
 536
 537                         if (!is_vmalloc_or_module_addr((void *)p)) {
 538                                 err = -ENXIO;
 539                                 break;
 540                         }
 541                         n = copy_from_user(kbuf, buf, sz);
 542                         if (n) {
 543                                 err = -EFAULT;
 544                                 break;
 545                         }
 546                         vwrite(kbuf, (char *)p, sz);
 547                         count -= sz;
 548                         buf += sz;
 549                         virtr += sz;
 550                         p += sz;
 551                 }
 552                 free_page((unsigned long)kbuf);
 553         }
 554
 555         *ppos = p;
 556         return virtr + wrote ? : err;
 557 }
 558 #endif
 559
 560 #ifdef CONFIG_DEVPORT
 561 static ssize_t read_port(struct file *file, char __user *buf,
 562                          size_t count, loff_t *ppos)
 563 {
 564         unsigned long i = *ppos;
 565         char __user *tmp = buf;
 566
 567         if (!access_ok(VERIFY_WRITE, buf, count))
 568                 return -EFAULT;
 569         while (count-- > 0 && i < 65536) {
 570                 if (__put_user(inb(i), tmp) < 0)
 571                         return -EFAULT;
 572                 i++;
 573                 tmp++;
 574         }
 575         *ppos = i;
 576         return tmp-buf;
 577 }
 578
 579 static ssize_t write_port(struct file *file, const char __user *buf,
 580                           size_t count, loff_t *ppos)
 581 {
 582         unsigned long i = *ppos;
 583         const char __user *tmp = buf;
 584
 585         if (!access_ok(VERIFY_READ, buf, count))
 586                 return -EFAULT;
 587         while (count-- > 0 && i < 65536) {
 588                 char c;
 589                 if (__get_user(c, tmp)) {
 590                         if (tmp > buf)
 591                                 break;
 592                         return -EFAULT;
 593                 }
 594                 outb(c, i);
 595                 i++;
 596                 tmp++;
 597         }
 598         *ppos = i;
 599         return tmp-buf;
 600 }
 601 #endif
 602
 603 static ssize_t read_null(struct file *file, char __user *buf,
 604                          size_t count, loff_t *ppos)
 605 {
 606         return 0;
 607 }
 608
 609 static ssize_t write_null(struct file *file, const char __user *buf,
 610                           size_t count, loff_t *ppos)
 611 {
 612         return count;
 613 }
 614
 615 static ssize_t aio_read_null(struct kiocb *iocb, const struct iovec *iov,
 616                              unsigned long nr_segs, loff_t pos)
 617 {
 618         return 0;
 619 }
 620
 621 static ssize_t aio_write_null(struct kiocb *iocb, const struct iovec *iov,
 622                               unsigned long nr_segs, loff_t pos)
 623 {
 624         return iov_length(iov, nr_segs);
 625 }
 626
 627 static int pipe_to_null(struct pipe_inode_info *info, struct pipe_buffer *buf,
 628                         struct splice_desc *sd)
 629 {
 630         return sd->len;
 631 }
 632
 633 static ssize_t splice_write_null(struct pipe_inode_info *pipe, struct file *out,
 634                                  loff_t *ppos, size_t len, unsigned int flags)
 635 {
 636         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_null);
 637 }
 638
 639 static ssize_t read_iter_zero(struct kiocb *iocb, struct iov_iter *iter)
 640 {
 641         size_t written = 0;
 642
 643         while (iov_iter_count(iter)) {
 644                 size_t chunk = iov_iter_count(iter), n;
 645                 if (chunk > PAGE_SIZE)
 646                         chunk = PAGE_SIZE;      /* Just for latency reasons */
 647                 n = iov_iter_zero(chunk, iter);
 648                 if (!n && iov_iter_count(iter))
 649                         return written ? written : -EFAULT;
 650                 written += n;
 651                 if (signal_pending(current))
 652                         return written ? written : -ERESTARTSYS;
 653                 cond_resched();
 654         }
 655         return written;
 656 }
 657
 658 static int mmap_zero(struct file *file, struct vm_area_struct *vma)
 659 {
 660 #ifndef CONFIG_MMU
 661         return -ENOSYS;
 662 #endif
 663         if (vma->vm_flags & VM_SHARED)
 664                 return shmem_zero_setup(vma);
 665         return 0;
 666 }
 667
 668 static ssize_t write_full(struct file *file, const char __user *buf,
 669                           size_t count, loff_t *ppos)
 670 {
 671         return -ENOSPC;
 672 }
 673
 674 /*
 675  * Special lseek() function for /dev/null and /dev/zero.  Most notably, you
 676  * can fopen() both devices with "a" now.  This was previously impossible.
 677  * -- SRB.
 678  */
 679 static loff_t null_lseek(struct file *file, loff_t offset, int orig)
 680 {
 681         return file->f_pos = 0;
 682 }
 683
 684 /*
 685  * The memory devices use the full 32/64 bits of the offset, and so we cannot
 686  * check against negative addresses: they are ok. The return value is weird,
 687  * though, in that case (0).
 688  *
 689  * also note that seeking relative to the "end of file" isn't supported:
 690  * it has no meaning, so it returns -EINVAL.
 691  */
 692 static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
 693 {
 694         loff_t ret;
 695
 696         mutex_lock(&file_inode(file)->i_mutex);
 697         switch (orig) {
 698         case SEEK_CUR:
 699                 offset += file->f_pos;
 700         case SEEK_SET:
 701                 /* to avoid userland mistaking f_pos=-9 as -EBADF=-9 */
 702                 if (IS_ERR_VALUE((unsigned long long)offset)) {
 703                         ret = -EOVERFLOW;
 704                         break;
 705                 }
 706                 file->f_pos = offset;
 707                 ret = file->f_pos;
 708                 force_successful_syscall_return();
 709                 break;
 710         default:
 711                 ret = -EINVAL;
 712         }
 713         mutex_unlock(&file_inode(file)->i_mutex);
 714         return ret;
 715 }
 716
 717 static int open_port(struct inode *inode, struct file *filp)
 718 {
 719         return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
 720 }
 721
 722 #define zero_lseek      null_lseek
 723 #define full_lseek      null_lseek
 724 #define write_zero      write_null
 725 #define aio_write_zero  aio_write_null
 726 #define open_mem        open_port
 727 #define open_kmem       open_mem
 728
 729 static const struct file_operations mem_fops = {
 730         .llseek         = memory_lseek,
 731         .read           = read_mem,
 732         .write          = write_mem,
 733         .mmap           = mmap_mem,
 734         .open           = open_mem,
 735 #ifndef CONFIG_MMU
 736         .get_unmapped_area = get_unmapped_area_mem,
 737         .mmap_capabilities = memory_mmap_capabilities,
 738 #endif
 739 };
 740
 741 #ifdef CONFIG_DEVKMEM
 742 static const struct file_operations kmem_fops = {
 743         .llseek         = memory_lseek,
 744         .read           = read_kmem,
 745         .write          = write_kmem,
 746         .mmap           = mmap_kmem,
 747         .open           = open_kmem,
 748 #ifndef CONFIG_MMU
 749         .get_unmapped_area = get_unmapped_area_mem,
 750         .mmap_capabilities = memory_mmap_capabilities,
 751 #endif
 752 };
 753 #endif
 754
 755 static const struct file_operations null_fops = {
 756         .llseek         = null_lseek,
 757         .read           = read_null,
 758         .write          = write_null,
 759         .aio_read       = aio_read_null,
 760         .aio_write      = aio_write_null,
 761         .splice_write   = splice_write_null,
 762 };
 763
 764 #ifdef CONFIG_DEVPORT
 765 static const struct file_operations port_fops = {
 766         .llseek         = memory_lseek,
 767         .read           = read_port,
 768         .write          = write_port,
 769         .open           = open_port,
 770 };
 771 #endif
 772
 773 static const struct file_operations zero_fops = {
 774         .llseek         = zero_lseek,
 775         .read           = new_sync_read,
 776         .write          = write_zero,
 777         .read_iter      = read_iter_zero,
 778         .aio_write      = aio_write_zero,
 779         .mmap           = mmap_zero,
 780 #ifndef CONFIG_MMU
 781         .mmap_capabilities = zero_mmap_capabilities,
 782 #endif
 783 };
 784
 785 static const struct file_operations full_fops = {
 786         .llseek         = full_lseek,
 787         .read           = new_sync_read,
 788         .read_iter      = read_iter_zero,
 789         .write          = write_full,
 790 };
 791
 792 static const struct memdev {
 793         const char *name;
 794         umode_t mode;
 795         const struct file_operations *fops;
 796         fmode_t fmode;
 797 } devlist[] = {
 798          [1] = { "mem", 0, &mem_fops, FMODE_UNSIGNED_OFFSET },
 799 #ifdef CONFIG_DEVKMEM
 800          [2] = { "kmem", 0, &kmem_fops, FMODE_UNSIGNED_OFFSET },
 801 #endif
 802          [3] = { "null", 0666, &null_fops, 0 },
 803 #ifdef CONFIG_DEVPORT
 804          [4] = { "port", 0, &port_fops, 0 },
 805 #endif
 806          [5] = { "zero", 0666, &zero_fops, 0 },
 807          [7] = { "full", 0666, &full_fops, 0 },
 808          [8] = { "random", 0666, &random_fops, 0 },
 809          [9] = { "urandom", 0666, &urandom_fops, 0 },
 810 #ifdef CONFIG_PRINTK
 811         [11] = { "kmsg", 0644, &kmsg_fops, 0 },
 812 #endif
 813 };
 814
 815 static int memory_open(struct inode *inode, struct file *filp)
 816 {
 817         int minor;
 818         const struct memdev *dev;
 819
 820         minor = iminor(inode);
 821         if (minor >= ARRAY_SIZE(devlist))
 822                 return -ENXIO;
 823
 824         dev = &devlist[minor];
 825         if (!dev->fops)
 826                 return -ENXIO;
 827
 828         filp->f_op = dev->fops;
 829         filp->f_mode |= dev->fmode;
 830
 831         if (dev->fops->open)
 832                 return dev->fops->open(inode, filp);
 833
 834         return 0;
 835 }
 836
 837 static const struct file_operations memory_fops = {
 838         .open = memory_open,
 839         .llseek = noop_llseek,
 840 };
 841
 842 static char *mem_devnode(struct device *dev, umode_t *mode)
 843 {
 844         if (mode && devlist[MINOR(dev->devt)].mode)
 845                 *mode = devlist[MINOR(dev->devt)].mode;
 846         return NULL;
 847 }
 848
 849 static struct class *mem_class;
 850
 851 static int __init chr_dev_init(void)
 852 {
 853         int minor;
 854
 855         if (register_chrdev(MEM_MAJOR, "mem", &memory_fops))
 856                 printk("unable to get major %d for memory devs\n", MEM_MAJOR);
 857
 858         mem_class = class_create(THIS_MODULE, "mem");
 859         if (IS_ERR(mem_class))
 860                 return PTR_ERR(mem_class);
 861
 862         mem_class->devnode = mem_devnode;
 863         for (minor = 1; minor < ARRAY_SIZE(devlist); minor++) {
 864                 if (!devlist[minor].name)
 865                         continue;
 866
 867                 /*
 868                  * Create /dev/port?
 869                  */
 870                 if ((minor == DEVPORT_MINOR) && !arch_has_dev_port())
 871                         continue;
 872
 873                 device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor),
 874                               NULL, devlist[minor].name);
 875         }
 876
 877         return tty_init();
 878 }
 879
 880 fs_initcall(chr_dev_init);