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 void __attribute__((weak))
 304 map_devmem(unsigned long pfn, unsigned long len, pgprot_t prot)
 305 {
 306         /* nothing. architectures can override. */
 307 }
 308
 309 void __attribute__((weak))
 310 unmap_devmem(unsigned long pfn, unsigned long len, pgprot_t prot)
 311 {
 312         /* nothing. architectures can override. */
 313 }
 314
 315 static void mmap_mem_open(struct vm_area_struct *vma)
 316 {
 317         map_devmem(vma->vm_pgoff,  vma->vm_end - vma->vm_start,
 318                         vma->vm_page_prot);
 319 }
 320
 321 static void mmap_mem_close(struct vm_area_struct *vma)
 322 {
 323         unmap_devmem(vma->vm_pgoff,  vma->vm_end - vma->vm_start,
 324                         vma->vm_page_prot);
 325 }
 326
 327 static struct vm_operations_struct mmap_mem_ops = {
 328         .open  = mmap_mem_open,
 329         .close = mmap_mem_close
 330 };
 331
 332 static int mmap_mem(struct file * file, struct vm_area_struct * vma)
 333 {
 334         size_t size = vma->vm_end - vma->vm_start;
 335
 336         if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))
 337                 return -EINVAL;
 338
 339         if (!private_mapping_ok(vma))
 340                 return -ENOSYS;
 341
 342         if (!range_is_allowed(vma->vm_pgoff, size))
 343                 return -EPERM;
 344
 345         if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size,
 346                                                 &vma->vm_page_prot))
 347                 return -EINVAL;
 348
 349         vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,
 350                                                  size,
 351                                                  vma->vm_page_prot);
 352
 353         vma->vm_ops = &mmap_mem_ops;
 354
 355         /* Remap-pfn-range will mark the range VM_IO and VM_RESERVED */
 356         if (remap_pfn_range(vma,
 357                             vma->vm_start,
 358                             vma->vm_pgoff,
 359                             size,
 360                             vma->vm_page_prot)) {
 361                 unmap_devmem(vma->vm_pgoff, size, vma->vm_page_prot);
 362                 return -EAGAIN;
 363         }
 364         return 0;
 365 }
 366
 367 static int mmap_kmem(struct file * file, struct vm_area_struct * vma)
 368 {
 369         unsigned long pfn;
 370
 371         /* Turn a kernel-virtual address into a physical page frame */
 372         pfn = __pa((u64)vma->vm_pgoff << PAGE_SHIFT) >> PAGE_SHIFT;
 373
 374         /*
 375          * RED-PEN: on some architectures there is more mapped memory
 376          * than available in mem_map which pfn_valid checks
 377          * for. Perhaps should add a new macro here.
 378          *
 379          * RED-PEN: vmalloc is not supported right now.
 380          */
 381         if (!pfn_valid(pfn))
 382                 return -EIO;
 383
 384         vma->vm_pgoff = pfn;
 385         return mmap_mem(file, vma);
 386 }
 387
 388 #ifdef CONFIG_CRASH_DUMP
 389 /*
 390  * Read memory corresponding to the old kernel.
 391  */
 392 static ssize_t read_oldmem(struct file *file, char __user *buf,
 393                                 size_t count, loff_t *ppos)
 394 {
 395         unsigned long pfn, offset;
 396         size_t read = 0, csize;
 397         int rc = 0;
 398
 399         while (count) {
 400                 pfn = *ppos / PAGE_SIZE;
 401                 if (pfn > saved_max_pfn)
 402                         return read;
 403
 404                 offset = (unsigned long)(*ppos % PAGE_SIZE);
 405                 if (count > PAGE_SIZE - offset)
 406                         csize = PAGE_SIZE - offset;
 407                 else
 408                         csize = count;
 409
 410                 rc = copy_oldmem_page(pfn, buf, csize, offset, 1);
 411                 if (rc < 0)
 412                         return rc;
 413                 buf += csize;
 414                 *ppos += csize;
 415                 read += csize;
 416                 count -= csize;
 417         }
 418         return read;
 419 }
 420 #endif
 421
 422 extern long vread(char *buf, char *addr, unsigned long count);
 423 extern long vwrite(char *buf, char *addr, unsigned long count);
 424
 425 /*
 426  * This function reads the *virtual* memory as seen by the kernel.
 427  */
 428 static ssize_t read_kmem(struct file *file, char __user *buf,
 429                          size_t count, loff_t *ppos)
 430 {
 431         unsigned long p = *ppos;
 432         ssize_t low_count, read, sz;
 433         char * kbuf; /* k-addr because vread() takes vmlist_lock rwlock */
 434
 435         read = 0;
 436         if (p < (unsigned long) high_memory) {
 437                 low_count = count;
 438                 if (count > (unsigned long) high_memory - p)
 439                         low_count = (unsigned long) high_memory - p;
 440
 441 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 442                 /* we don't have page 0 mapped on sparc and m68k.. */
 443                 if (p < PAGE_SIZE && low_count > 0) {
 444                         size_t tmp = PAGE_SIZE - p;
 445                         if (tmp > low_count) tmp = low_count;
 446                         if (clear_user(buf, tmp))
 447                                 return -EFAULT;
 448                         buf += tmp;
 449                         p += tmp;
 450                         read += tmp;
 451                         low_count -= tmp;
 452                         count -= tmp;
 453                 }
 454 #endif
 455                 while (low_count > 0) {
 456                         /*
 457                          * Handle first page in case it's not aligned
 458                          */
 459                         if (-p & (PAGE_SIZE - 1))
 460                                 sz = -p & (PAGE_SIZE - 1);
 461                         else
 462                                 sz = PAGE_SIZE;
 463
 464                         sz = min_t(unsigned long, sz, low_count);
 465
 466                         /*
 467                          * On ia64 if a page has been mapped somewhere as
 468                          * uncached, then it must also be accessed uncached
 469                          * by the kernel or data corruption may occur
 470                          */
 471                         kbuf = xlate_dev_kmem_ptr((char *)p);
 472
 473                         if (copy_to_user(buf, kbuf, sz))
 474                                 return -EFAULT;
 475                         buf += sz;
 476                         p += sz;
 477                         read += sz;
 478                         low_count -= sz;
 479                         count -= sz;
 480                 }
 481         }
 482
 483         if (count > 0) {
 484                 kbuf = (char *)__get_free_page(GFP_KERNEL);
 485                 if (!kbuf)
 486                         return -ENOMEM;
 487                 while (count > 0) {
 488                         int len = count;
 489
 490                         if (len > PAGE_SIZE)
 491                                 len = PAGE_SIZE;
 492                         len = vread(kbuf, (char *)p, len);
 493                         if (!len)
 494                                 break;
 495                         if (copy_to_user(buf, kbuf, len)) {
 496                                 free_page((unsigned long)kbuf);
 497                                 return -EFAULT;
 498                         }
 499                         count -= len;
 500                         buf += len;
 501                         read += len;
 502                         p += len;
 503                 }
 504                 free_page((unsigned long)kbuf);
 505         }
 506         *ppos = p;
 507         return read;
 508 }
 509
 510
 511 static inline ssize_t
 512 do_write_kmem(void *p, unsigned long realp, const char __user * buf,
 513               size_t count, loff_t *ppos)
 514 {
 515         ssize_t written, sz;
 516         unsigned long copied;
 517
 518         written = 0;
 519 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 520         /* we don't have page 0 mapped on sparc and m68k.. */
 521         if (realp < PAGE_SIZE) {
 522                 unsigned long sz = PAGE_SIZE - realp;
 523                 if (sz > count)
 524                         sz = count;
 525                 /* Hmm. Do something? */
 526                 buf += sz;
 527                 p += sz;
 528                 realp += sz;
 529                 count -= sz;
 530                 written += sz;
 531         }
 532 #endif
 533
 534         while (count > 0) {
 535                 char *ptr;
 536                 /*
 537                  * Handle first page in case it's not aligned
 538                  */
 539                 if (-realp & (PAGE_SIZE - 1))
 540                         sz = -realp & (PAGE_SIZE - 1);
 541                 else
 542                         sz = PAGE_SIZE;
 543
 544                 sz = min_t(unsigned long, sz, count);
 545
 546                 /*
 547                  * On ia64 if a page has been mapped somewhere as
 548                  * uncached, then it must also be accessed uncached
 549                  * by the kernel or data corruption may occur
 550                  */
 551                 ptr = xlate_dev_kmem_ptr(p);
 552
 553                 copied = copy_from_user(ptr, buf, sz);
 554                 if (copied) {
 555                         written += sz - copied;
 556                         if (written)
 557                                 break;
 558                         return -EFAULT;
 559                 }
 560                 buf += sz;
 561                 p += sz;
 562                 realp += sz;
 563                 count -= sz;
 564                 written += sz;
 565         }
 566
 567         *ppos += written;
 568         return written;
 569 }
 570
 571
 572 /*
 573  * This function writes to the *virtual* memory as seen by the kernel.
 574  */
 575 static ssize_t write_kmem(struct file * file, const char __user * buf,
 576                           size_t count, loff_t *ppos)
 577 {
 578         unsigned long p = *ppos;
 579         ssize_t wrote = 0;
 580         ssize_t virtr = 0;
 581         ssize_t written;
 582         char * kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
 583
 584         if (p < (unsigned long) high_memory) {
 585
 586                 wrote = count;
 587                 if (count > (unsigned long) high_memory - p)
 588                         wrote = (unsigned long) high_memory - p;
 589
 590                 written = do_write_kmem((void*)p, p, buf, wrote, ppos);
 591                 if (written != wrote)
 592                         return written;
 593                 wrote = written;
 594                 p += wrote;
 595                 buf += wrote;
 596                 count -= wrote;
 597         }
 598
 599         if (count > 0) {
 600                 kbuf = (char *)__get_free_page(GFP_KERNEL);
 601                 if (!kbuf)
 602                         return wrote ? wrote : -ENOMEM;
 603                 while (count > 0) {
 604                         int len = count;
 605
 606                         if (len > PAGE_SIZE)
 607                                 len = PAGE_SIZE;
 608                         if (len) {
 609                                 written = copy_from_user(kbuf, buf, len);
 610                                 if (written) {
 611                                         if (wrote + virtr)
 612                                                 break;
 613                                         free_page((unsigned long)kbuf);
 614                                         return -EFAULT;
 615                                 }
 616                         }
 617                         len = vwrite(kbuf, (char *)p, len);
 618                         count -= len;
 619                         buf += len;
 620                         virtr += len;
 621                         p += len;
 622                 }
 623                 free_page((unsigned long)kbuf);
 624         }
 625
 626         *ppos = p;
 627         return virtr + wrote;
 628 }
 629
 630 #ifdef CONFIG_DEVPORT
 631 static ssize_t read_port(struct file * file, char __user * buf,
 632                          size_t count, loff_t *ppos)
 633 {
 634         unsigned long i = *ppos;
 635         char __user *tmp = buf;
 636
 637         if (!access_ok(VERIFY_WRITE, buf, count))
 638                 return -EFAULT;
 639         while (count-- > 0 && i < 65536) {
 640                 if (__put_user(inb(i),tmp) < 0)
 641                         return -EFAULT;
 642                 i++;
 643                 tmp++;
 644         }
 645         *ppos = i;
 646         return tmp-buf;
 647 }
 648
 649 static ssize_t write_port(struct file * file, const char __user * buf,
 650                           size_t count, loff_t *ppos)
 651 {
 652         unsigned long i = *ppos;
 653         const char __user * tmp = buf;
 654
 655         if (!access_ok(VERIFY_READ,buf,count))
 656                 return -EFAULT;
 657         while (count-- > 0 && i < 65536) {
 658                 char c;
 659                 if (__get_user(c, tmp)) {
 660                         if (tmp > buf)
 661                                 break;
 662                         return -EFAULT;
 663                 }
 664                 outb(c,i);
 665                 i++;
 666                 tmp++;
 667         }
 668         *ppos = i;
 669         return tmp-buf;
 670 }
 671 #endif
 672
 673 static ssize_t read_null(struct file * file, char __user * buf,
 674                          size_t count, loff_t *ppos)
 675 {
 676         return 0;
 677 }
 678
 679 static ssize_t write_null(struct file * file, const char __user * buf,
 680                           size_t count, loff_t *ppos)
 681 {
 682         return count;
 683 }
 684
 685 static int pipe_to_null(struct pipe_inode_info *info, struct pipe_buffer *buf,
 686                         struct splice_desc *sd)
 687 {
 688         return sd->len;
 689 }
 690
 691 static ssize_t splice_write_null(struct pipe_inode_info *pipe,struct file *out,
 692                                  loff_t *ppos, size_t len, unsigned int flags)
 693 {
 694         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_null);
 695 }
 696
 697 static ssize_t read_zero(struct file * file, char __user * buf,
 698                          size_t count, loff_t *ppos)
 699 {
 700         size_t written;
 701
 702         if (!count)
 703                 return 0;
 704
 705         if (!access_ok(VERIFY_WRITE, buf, count))
 706                 return -EFAULT;
 707
 708         written = 0;
 709         while (count) {
 710                 unsigned long unwritten;
 711                 size_t chunk = count;
 712
 713                 if (chunk > PAGE_SIZE)
 714                         chunk = PAGE_SIZE;      /* Just for latency reasons */
 715                 unwritten = clear_user(buf, chunk);
 716                 written += chunk - unwritten;
 717                 if (unwritten)
 718                         break;
 719                 buf += chunk;
 720                 count -= chunk;
 721                 cond_resched();
 722         }
 723         return written ? written : -EFAULT;
 724 }
 725
 726 static int mmap_zero(struct file * file, struct vm_area_struct * vma)
 727 {
 728 #ifndef CONFIG_MMU
 729         return -ENOSYS;
 730 #endif
 731         if (vma->vm_flags & VM_SHARED)
 732                 return shmem_zero_setup(vma);
 733         return 0;
 734 }
 735
 736 static ssize_t write_full(struct file * file, const char __user * buf,
 737                           size_t count, loff_t *ppos)
 738 {
 739         return -ENOSPC;
 740 }
 741
 742 /*
 743  * Special lseek() function for /dev/null and /dev/zero.  Most notably, you
 744  * can fopen() both devices with "a" now.  This was previously impossible.
 745  * -- SRB.
 746  */
 747
 748 static loff_t null_lseek(struct file * file, loff_t offset, int orig)
 749 {
 750         return file->f_pos = 0;
 751 }
 752
 753 /*
 754  * The memory devices use the full 32/64 bits of the offset, and so we cannot
 755  * check against negative addresses: they are ok. The return value is weird,
 756  * though, in that case (0).
 757  *
 758  * also note that seeking relative to the "end of file" isn't supported:
 759  * it has no meaning, so it returns -EINVAL.
 760  */
 761 static loff_t memory_lseek(struct file * file, loff_t offset, int orig)
 762 {
 763         loff_t ret;
 764
 765         mutex_lock(&file->f_path.dentry->d_inode->i_mutex);
 766         switch (orig) {
 767                 case 0:
 768                         file->f_pos = offset;
 769                         ret = file->f_pos;
 770                         force_successful_syscall_return();
 771                         break;
 772                 case 1:
 773                         file->f_pos += offset;
 774                         ret = file->f_pos;
 775                         force_successful_syscall_return();
 776                         break;
 777                 default:
 778                         ret = -EINVAL;
 779         }
 780         mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
 781         return ret;
 782 }
 783
 784 static int open_port(struct inode * inode, struct file * filp)
 785 {
 786         return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
 787 }
 788
 789 #define zero_lseek      null_lseek
 790 #define full_lseek      null_lseek
 791 #define write_zero      write_null
 792 #define read_full       read_zero
 793 #define open_mem        open_port
 794 #define open_kmem       open_mem
 795 #define open_oldmem     open_mem
 796
 797 static const struct file_operations mem_fops = {
 798         .llseek         = memory_lseek,
 799         .read           = read_mem,
 800         .write          = write_mem,
 801         .mmap           = mmap_mem,
 802         .open           = open_mem,
 803         .get_unmapped_area = get_unmapped_area_mem,
 804 };
 805
 806 static const struct file_operations kmem_fops = {
 807         .llseek         = memory_lseek,
 808         .read           = read_kmem,
 809         .write          = write_kmem,
 810         .mmap           = mmap_kmem,
 811         .open           = open_kmem,
 812         .get_unmapped_area = get_unmapped_area_mem,
 813 };
 814
 815 static const struct file_operations null_fops = {
 816         .llseek         = null_lseek,
 817         .read           = read_null,
 818         .write          = write_null,
 819         .splice_write   = splice_write_null,
 820 };
 821
 822 #ifdef CONFIG_DEVPORT
 823 static const struct file_operations port_fops = {
 824         .llseek         = memory_lseek,
 825         .read           = read_port,
 826         .write          = write_port,
 827         .open           = open_port,
 828 };
 829 #endif
 830
 831 static const struct file_operations zero_fops = {
 832         .llseek         = zero_lseek,
 833         .read           = read_zero,
 834         .write          = write_zero,
 835         .mmap           = mmap_zero,
 836 };
 837
 838 /*
 839  * capabilities for /dev/zero
 840  * - permits private mappings, "copies" are taken of the source of zeros
 841  */
 842 static struct backing_dev_info zero_bdi = {
 843         .capabilities   = BDI_CAP_MAP_COPY,
 844 };
 845
 846 static const struct file_operations full_fops = {
 847         .llseek         = full_lseek,
 848         .read           = read_full,
 849         .write          = write_full,
 850 };
 851
 852 #ifdef CONFIG_CRASH_DUMP
 853 static const struct file_operations oldmem_fops = {
 854         .read   = read_oldmem,
 855         .open   = open_oldmem,
 856 };
 857 #endif
 858
 859 static ssize_t kmsg_write(struct file * file, const char __user * buf,
 860                           size_t count, loff_t *ppos)
 861 {
 862         char *tmp;
 863         ssize_t ret;
 864
 865         tmp = kmalloc(count + 1, GFP_KERNEL);
 866         if (tmp == NULL)
 867                 return -ENOMEM;
 868         ret = -EFAULT;
 869         if (!copy_from_user(tmp, buf, count)) {
 870                 tmp[count] = 0;
 871                 ret = printk("%s", tmp);
 872                 if (ret > count)
 873                         /* printk can add a prefix */
 874                         ret = count;
 875         }
 876         kfree(tmp);
 877         return ret;
 878 }
 879
 880 static const struct file_operations kmsg_fops = {
 881         .write =        kmsg_write,
 882 };
 883
 884 static int memory_open(struct inode * inode, struct file * filp)
 885 {
 886         switch (iminor(inode)) {
 887                 case 1:
 888                         filp->f_op = &mem_fops;
 889                         filp->f_mapping->backing_dev_info =
 890                                 &directly_mappable_cdev_bdi;
 891                         break;
 892                 case 2:
 893                         filp->f_op = &kmem_fops;
 894                         filp->f_mapping->backing_dev_info =
 895                                 &directly_mappable_cdev_bdi;
 896                         break;
 897                 case 3:
 898                         filp->f_op = &null_fops;
 899                         break;
 900 #ifdef CONFIG_DEVPORT
 901                 case 4:
 902                         filp->f_op = &port_fops;
 903                         break;
 904 #endif
 905                 case 5:
 906                         filp->f_mapping->backing_dev_info = &zero_bdi;
 907                         filp->f_op = &zero_fops;
 908                         break;
 909                 case 7:
 910                         filp->f_op = &full_fops;
 911                         break;
 912                 case 8:
 913                         filp->f_op = &random_fops;
 914                         break;
 915                 case 9:
 916                         filp->f_op = &urandom_fops;
 917                         break;
 918                 case 11:
 919                         filp->f_op = &kmsg_fops;
 920                         break;
 921 #ifdef CONFIG_CRASH_DUMP
 922                 case 12:
 923                         filp->f_op = &oldmem_fops;
 924                         break;
 925 #endif
 926                 default:
 927                         return -ENXIO;
 928         }
 929         if (filp->f_op && filp->f_op->open)
 930                 return filp->f_op->open(inode,filp);
 931         return 0;
 932 }
 933
 934 static const struct file_operations memory_fops = {
 935         .open           = memory_open,  /* just a selector for the real open */
 936 };
 937
 938 static const struct {
 939         unsigned int            minor;
 940         char                    *name;
 941         umode_t                 mode;
 942         const struct file_operations    *fops;
 943 } devlist[] = { /* list of minor devices */
 944         {1, "mem",     S_IRUSR | S_IWUSR | S_IRGRP, &mem_fops},
 945         {2, "kmem",    S_IRUSR | S_IWUSR | S_IRGRP, &kmem_fops},
 946         {3, "null",    S_IRUGO | S_IWUGO,           &null_fops},
 947 #ifdef CONFIG_DEVPORT
 948         {4, "port",    S_IRUSR | S_IWUSR | S_IRGRP, &port_fops},
 949 #endif
 950         {5, "zero",    S_IRUGO | S_IWUGO,           &zero_fops},
 951         {7, "full",    S_IRUGO | S_IWUGO,           &full_fops},
 952         {8, "random",  S_IRUGO | S_IWUSR,           &random_fops},
 953         {9, "urandom", S_IRUGO | S_IWUSR,           &urandom_fops},
 954         {11,"kmsg",    S_IRUGO | S_IWUSR,           &kmsg_fops},
 955 #ifdef CONFIG_CRASH_DUMP
 956         {12,"oldmem",    S_IRUSR | S_IWUSR | S_IRGRP, &oldmem_fops},
 957 #endif
 958 };
 959
 960 static struct class *mem_class;
 961
 962 static int __init chr_dev_init(void)
 963 {
 964         int i;
 965         int err;
 966
 967         err = bdi_init(&zero_bdi);
 968         if (err)
 969                 return err;
 970
 971         if (register_chrdev(MEM_MAJOR,"mem",&memory_fops))
 972                 printk("unable to get major %d for memory devs\n", MEM_MAJOR);
 973
 974         mem_class = class_create(THIS_MODULE, "mem");
 975         for (i = 0; i < ARRAY_SIZE(devlist); i++)
 976                 device_create(mem_class, NULL,
 977                               MKDEV(MEM_MAJOR, devlist[i].minor),
 978                               devlist[i].name);
 979
 980         return 0;
 981 }
 982
 983 fs_initcall(chr_dev_init);