linux/drivers/char/mem.c
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   1/*
   2 *  linux/drivers/char/mem.c
   3 *
   4 *  Copyright (C) 1991, 1992  Linus Torvalds
   5 *
   6 *  Added devfs support.
   7 *    Jan-11-1998, C. Scott Ananian <cananian@alumni.princeton.edu>
   8 *  Shared /dev/zero mmapping support, Feb 2000, Kanoj Sarcar <kanoj@sgi.com>
   9 */
  10
  11#include <linux/mm.h>
  12#include <linux/miscdevice.h>
  13#include <linux/slab.h>
  14#include <linux/vmalloc.h>
  15#include <linux/mman.h>
  16#include <linux/random.h>
  17#include <linux/init.h>
  18#include <linux/raw.h>
  19#include <linux/tty.h>
  20#include <linux/capability.h>
  21#include <linux/ptrace.h>
  22#include <linux/device.h>
  23#include <linux/highmem.h>
  24#include <linux/crash_dump.h>
  25#include <linux/backing-dev.h>
  26#include <linux/bootmem.h>
  27#include <linux/splice.h>
  28#include <linux/pfn.h>
  29#include <linux/export.h>
  30#include <linux/io.h>
  31
  32#include <asm/uaccess.h>
  33
  34#ifdef CONFIG_IA64
  35# include <linux/efi.h>
  36#endif
  37
  38#define DEVPORT_MINOR   4
  39
  40static inline unsigned long size_inside_page(unsigned long start,
  41                                             unsigned long size)
  42{
  43        unsigned long sz;
  44
  45        sz = PAGE_SIZE - (start & (PAGE_SIZE - 1));
  46
  47        return min(sz, size);
  48}
  49
  50#ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE
  51static inline int valid_phys_addr_range(phys_addr_t addr, size_t count)
  52{
  53        return addr + count <= __pa(high_memory);
  54}
  55
  56static inline int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
  57{
  58        return 1;
  59}
  60#endif
  61
  62#ifdef CONFIG_STRICT_DEVMEM
  63static inline int range_is_allowed(unsigned long pfn, unsigned long size)
  64{
  65        u64 from = ((u64)pfn) << PAGE_SHIFT;
  66        u64 to = from + size;
  67        u64 cursor = from;
  68
  69        while (cursor < to) {
  70                if (!devmem_is_allowed(pfn)) {
  71                        printk(KERN_INFO
  72                "Program %s tried to access /dev/mem between %Lx->%Lx.\n",
  73                                current->comm, from, to);
  74                        return 0;
  75                }
  76                cursor += PAGE_SIZE;
  77                pfn++;
  78        }
  79        return 1;
  80}
  81#else
  82static inline int range_is_allowed(unsigned long pfn, unsigned long size)
  83{
  84        return 1;
  85}
  86#endif
  87
  88void __weak unxlate_dev_mem_ptr(unsigned long phys, void *addr)
  89{
  90}
  91
  92/*
  93 * This funcion reads the *physical* memory. The f_pos points directly to the
  94 * memory location.
  95 */
  96static ssize_t read_mem(struct file *file, char __user *buf,
  97                        size_t count, loff_t *ppos)
  98{
  99        phys_addr_t p = *ppos;
 100        ssize_t read, sz;
 101        char *ptr;
 102
 103        if (!valid_phys_addr_range(p, count))
 104                return -EFAULT;
 105        read = 0;
 106#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 107        /* we don't have page 0 mapped on sparc and m68k.. */
 108        if (p < PAGE_SIZE) {
 109                sz = size_inside_page(p, count);
 110                if (sz > 0) {
 111                        if (clear_user(buf, sz))
 112                                return -EFAULT;
 113                        buf += sz;
 114                        p += sz;
 115                        count -= sz;
 116                        read += sz;
 117                }
 118        }
 119#endif
 120
 121        while (count > 0) {
 122                unsigned long remaining;
 123
 124                sz = size_inside_page(p, count);
 125
 126                if (!range_is_allowed(p >> PAGE_SHIFT, count))
 127                        return -EPERM;
 128
 129                /*
 130                 * On ia64 if a page has been mapped somewhere as uncached, then
 131                 * it must also be accessed uncached by the kernel or data
 132                 * corruption may occur.
 133                 */
 134                ptr = xlate_dev_mem_ptr(p);
 135                if (!ptr)
 136                        return -EFAULT;
 137
 138                remaining = copy_to_user(buf, ptr, sz);
 139                unxlate_dev_mem_ptr(p, ptr);
 140                if (remaining)
 141                        return -EFAULT;
 142
 143                buf += sz;
 144                p += sz;
 145                count -= sz;
 146                read += sz;
 147        }
 148
 149        *ppos += read;
 150        return read;
 151}
 152
 153static ssize_t write_mem(struct file *file, const char __user *buf,
 154                         size_t count, loff_t *ppos)
 155{
 156        phys_addr_t p = *ppos;
 157        ssize_t written, sz;
 158        unsigned long copied;
 159        void *ptr;
 160
 161        if (!valid_phys_addr_range(p, count))
 162                return -EFAULT;
 163
 164        written = 0;
 165
 166#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 167        /* we don't have page 0 mapped on sparc and m68k.. */
 168        if (p < PAGE_SIZE) {
 169                sz = size_inside_page(p, count);
 170                /* Hmm. Do something? */
 171                buf += sz;
 172                p += sz;
 173                count -= sz;
 174                written += sz;
 175        }
 176#endif
 177
 178        while (count > 0) {
 179                sz = size_inside_page(p, count);
 180
 181                if (!range_is_allowed(p >> PAGE_SHIFT, sz))
 182                        return -EPERM;
 183
 184                /*
 185                 * On ia64 if a page has been mapped somewhere as uncached, then
 186                 * it must also be accessed uncached by the kernel or data
 187                 * corruption may occur.
 188                 */
 189                ptr = xlate_dev_mem_ptr(p);
 190                if (!ptr) {
 191                        if (written)
 192                                break;
 193                        return -EFAULT;
 194                }
 195
 196                copied = copy_from_user(ptr, buf, sz);
 197                unxlate_dev_mem_ptr(p, ptr);
 198                if (copied) {
 199                        written += sz - copied;
 200                        if (written)
 201                                break;
 202                        return -EFAULT;
 203                }
 204
 205                buf += sz;
 206                p += sz;
 207                count -= sz;
 208                written += sz;
 209        }
 210
 211        *ppos += written;
 212        return written;
 213}
 214
 215int __weak phys_mem_access_prot_allowed(struct file *file,
 216        unsigned long pfn, unsigned long size, pgprot_t *vma_prot)
 217{
 218        return 1;
 219}
 220
 221#ifndef __HAVE_PHYS_MEM_ACCESS_PROT
 222
 223/*
 224 * Architectures vary in how they handle caching for addresses
 225 * outside of main memory.
 226 *
 227 */
 228#ifdef pgprot_noncached
 229static int uncached_access(struct file *file, phys_addr_t addr)
 230{
 231#if defined(CONFIG_IA64)
 232        /*
 233         * On ia64, we ignore O_DSYNC because we cannot tolerate memory
 234         * attribute aliases.
 235         */
 236        return !(efi_mem_attributes(addr) & EFI_MEMORY_WB);
 237#elif defined(CONFIG_MIPS)
 238        {
 239                extern int __uncached_access(struct file *file,
 240                                             unsigned long addr);
 241
 242                return __uncached_access(file, addr);
 243        }
 244#else
 245        /*
 246         * Accessing memory above the top the kernel knows about or through a
 247         * file pointer
 248         * that was marked O_DSYNC will be done non-cached.
 249         */
 250        if (file->f_flags & O_DSYNC)
 251                return 1;
 252        return addr >= __pa(high_memory);
 253#endif
 254}
 255#endif
 256
 257static pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 258                                     unsigned long size, pgprot_t vma_prot)
 259{
 260#ifdef pgprot_noncached
 261        phys_addr_t offset = pfn << PAGE_SHIFT;
 262
 263        if (uncached_access(file, offset))
 264                return pgprot_noncached(vma_prot);
 265#endif
 266        return vma_prot;
 267}
 268#endif
 269
 270#ifndef CONFIG_MMU
 271static unsigned long get_unmapped_area_mem(struct file *file,
 272                                           unsigned long addr,
 273                                           unsigned long len,
 274                                           unsigned long pgoff,
 275                                           unsigned long flags)
 276{
 277        if (!valid_mmap_phys_addr_range(pgoff, len))
 278                return (unsigned long) -EINVAL;
 279        return pgoff << PAGE_SHIFT;
 280}
 281
 282/* can't do an in-place private mapping if there's no MMU */
 283static inline int private_mapping_ok(struct vm_area_struct *vma)
 284{
 285        return vma->vm_flags & VM_MAYSHARE;
 286}
 287#else
 288#define get_unmapped_area_mem   NULL
 289
 290static inline int private_mapping_ok(struct vm_area_struct *vma)
 291{
 292        return 1;
 293}
 294#endif
 295
 296static const struct vm_operations_struct mmap_mem_ops = {
 297#ifdef CONFIG_HAVE_IOREMAP_PROT
 298        .access = generic_access_phys
 299#endif
 300};
 301
 302static int mmap_mem(struct file *file, struct vm_area_struct *vma)
 303{
 304        size_t size = vma->vm_end - vma->vm_start;
 305
 306        if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))
 307                return -EINVAL;
 308
 309        if (!private_mapping_ok(vma))
 310                return -ENOSYS;
 311
 312        if (!range_is_allowed(vma->vm_pgoff, size))
 313                return -EPERM;
 314
 315        if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size,
 316                                                &vma->vm_page_prot))
 317                return -EINVAL;
 318
 319        vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,
 320                                                 size,
 321                                                 vma->vm_page_prot);
 322
 323        vma->vm_ops = &mmap_mem_ops;
 324
 325        /* Remap-pfn-range will mark the range VM_IO */
 326        if (remap_pfn_range(vma,
 327                            vma->vm_start,
 328                            vma->vm_pgoff,
 329                            size,
 330                            vma->vm_page_prot)) {
 331                return -EAGAIN;
 332        }
 333        return 0;
 334}
 335
 336#ifdef CONFIG_DEVKMEM
 337static int mmap_kmem(struct file *file, struct vm_area_struct *vma)
 338{
 339        unsigned long pfn;
 340
 341        /* Turn a kernel-virtual address into a physical page frame */
 342        pfn = __pa((u64)vma->vm_pgoff << PAGE_SHIFT) >> PAGE_SHIFT;
 343
 344        /*
 345         * RED-PEN: on some architectures there is more mapped memory than
 346         * available in mem_map which pfn_valid checks for. Perhaps should add a
 347         * new macro here.
 348         *
 349         * RED-PEN: vmalloc is not supported right now.
 350         */
 351        if (!pfn_valid(pfn))
 352                return -EIO;
 353
 354        vma->vm_pgoff = pfn;
 355        return mmap_mem(file, vma);
 356}
 357#endif
 358
 359#ifdef CONFIG_CRASH_DUMP
 360/*
 361 * Read memory corresponding to the old kernel.
 362 */
 363static ssize_t read_oldmem(struct file *file, char __user *buf,
 364                                size_t count, loff_t *ppos)
 365{
 366        unsigned long pfn, offset;
 367        size_t read = 0, csize;
 368        int rc = 0;
 369
 370        while (count) {
 371                pfn = *ppos / PAGE_SIZE;
 372                if (pfn > saved_max_pfn)
 373                        return read;
 374
 375                offset = (unsigned long)(*ppos % PAGE_SIZE);
 376                if (count > PAGE_SIZE - offset)
 377                        csize = PAGE_SIZE - offset;
 378                else
 379                        csize = count;
 380
 381                rc = copy_oldmem_page(pfn, buf, csize, offset, 1);
 382                if (rc < 0)
 383                        return rc;
 384                buf += csize;
 385                *ppos += csize;
 386                read += csize;
 387                count -= csize;
 388        }
 389        return read;
 390}
 391#endif
 392
 393#ifdef CONFIG_DEVKMEM
 394/*
 395 * This function reads the *virtual* memory as seen by the kernel.
 396 */
 397static ssize_t read_kmem(struct file *file, char __user *buf,
 398                         size_t count, loff_t *ppos)
 399{
 400        unsigned long p = *ppos;
 401        ssize_t low_count, read, sz;
 402        char * kbuf; /* k-addr because vread() takes vmlist_lock rwlock */
 403        int err = 0;
 404
 405        read = 0;
 406        if (p < (unsigned long) high_memory) {
 407                low_count = count;
 408                if (count > (unsigned long)high_memory - p)
 409                        low_count = (unsigned long)high_memory - p;
 410
 411#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 412                /* we don't have page 0 mapped on sparc and m68k.. */
 413                if (p < PAGE_SIZE && low_count > 0) {
 414                        sz = size_inside_page(p, low_count);
 415                        if (clear_user(buf, sz))
 416                                return -EFAULT;
 417                        buf += sz;
 418                        p += sz;
 419                        read += sz;
 420                        low_count -= sz;
 421                        count -= sz;
 422                }
 423#endif
 424                while (low_count > 0) {
 425                        sz = size_inside_page(p, low_count);
 426
 427                        /*
 428                         * On ia64 if a page has been mapped somewhere as
 429                         * uncached, then it must also be accessed uncached
 430                         * by the kernel or data corruption may occur
 431                         */
 432                        kbuf = xlate_dev_kmem_ptr((char *)p);
 433
 434                        if (copy_to_user(buf, kbuf, sz))
 435                                return -EFAULT;
 436                        buf += sz;
 437                        p += sz;
 438                        read += sz;
 439                        low_count -= sz;
 440                        count -= sz;
 441                }
 442        }
 443
 444        if (count > 0) {
 445                kbuf = (char *)__get_free_page(GFP_KERNEL);
 446                if (!kbuf)
 447                        return -ENOMEM;
 448                while (count > 0) {
 449                        sz = size_inside_page(p, count);
 450                        if (!is_vmalloc_or_module_addr((void *)p)) {
 451                                err = -ENXIO;
 452                                break;
 453                        }
 454                        sz = vread(kbuf, (char *)p, sz);
 455                        if (!sz)
 456                                break;
 457                        if (copy_to_user(buf, kbuf, sz)) {
 458                                err = -EFAULT;
 459                                break;
 460                        }
 461                        count -= sz;
 462                        buf += sz;
 463                        read += sz;
 464                        p += sz;
 465                }
 466                free_page((unsigned long)kbuf);
 467        }
 468        *ppos = p;
 469        return read ? read : err;
 470}
 471
 472
 473static ssize_t do_write_kmem(unsigned long p, const char __user *buf,
 474                                size_t count, loff_t *ppos)
 475{
 476        ssize_t written, sz;
 477        unsigned long copied;
 478
 479        written = 0;
 480#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 481        /* we don't have page 0 mapped on sparc and m68k.. */
 482        if (p < PAGE_SIZE) {
 483                sz = size_inside_page(p, count);
 484                /* Hmm. Do something? */
 485                buf += sz;
 486                p += sz;
 487                count -= sz;
 488                written += sz;
 489        }
 490#endif
 491
 492        while (count > 0) {
 493                char *ptr;
 494
 495                sz = size_inside_page(p, count);
 496
 497                /*
 498                 * On ia64 if a page has been mapped somewhere as uncached, then
 499                 * it must also be accessed uncached by the kernel or data
 500                 * corruption may occur.
 501                 */
 502                ptr = xlate_dev_kmem_ptr((char *)p);
 503
 504                copied = copy_from_user(ptr, buf, sz);
 505                if (copied) {
 506                        written += sz - copied;
 507                        if (written)
 508                                break;
 509                        return -EFAULT;
 510                }
 511                buf += sz;
 512                p += sz;
 513                count -= sz;
 514                written += sz;
 515        }
 516
 517        *ppos += written;
 518        return written;
 519}
 520
 521/*
 522 * This function writes to the *virtual* memory as seen by the kernel.
 523 */
 524static ssize_t write_kmem(struct file *file, const char __user *buf,
 525                          size_t count, loff_t *ppos)
 526{
 527        unsigned long p = *ppos;
 528        ssize_t wrote = 0;
 529        ssize_t virtr = 0;
 530        char * kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
 531        int err = 0;
 532
 533        if (p < (unsigned long) high_memory) {
 534                unsigned long to_write = min_t(unsigned long, count,
 535                                               (unsigned long)high_memory - p);
 536                wrote = do_write_kmem(p, buf, to_write, ppos);
 537                if (wrote != to_write)
 538                        return wrote;
 539                p += wrote;
 540                buf += wrote;
 541                count -= wrote;
 542        }
 543
 544        if (count > 0) {
 545                kbuf = (char *)__get_free_page(GFP_KERNEL);
 546                if (!kbuf)
 547                        return wrote ? wrote : -ENOMEM;
 548                while (count > 0) {
 549                        unsigned long sz = size_inside_page(p, count);
 550                        unsigned long n;
 551
 552                        if (!is_vmalloc_or_module_addr((void *)p)) {
 553                                err = -ENXIO;
 554                                break;
 555                        }
 556                        n = copy_from_user(kbuf, buf, sz);
 557                        if (n) {
 558                                err = -EFAULT;
 559                                break;
 560                        }
 561                        vwrite(kbuf, (char *)p, sz);
 562                        count -= sz;
 563                        buf += sz;
 564                        virtr += sz;
 565                        p += sz;
 566                }
 567                free_page((unsigned long)kbuf);
 568        }
 569
 570        *ppos = p;
 571        return virtr + wrote ? : err;
 572}
 573#endif
 574
 575#ifdef CONFIG_DEVPORT
 576static ssize_t read_port(struct file *file, char __user *buf,
 577                         size_t count, loff_t *ppos)
 578{
 579        unsigned long i = *ppos;
 580        char __user *tmp = buf;
 581
 582        if (!access_ok(VERIFY_WRITE, buf, count))
 583                return -EFAULT;
 584        while (count-- > 0 && i < 65536) {
 585                if (__put_user(inb(i), tmp) < 0)
 586                        return -EFAULT;
 587                i++;
 588                tmp++;
 589        }
 590        *ppos = i;
 591        return tmp-buf;
 592}
 593
 594static ssize_t write_port(struct file *file, const char __user *buf,
 595                          size_t count, loff_t *ppos)
 596{
 597        unsigned long i = *ppos;
 598        const char __user * tmp = buf;
 599
 600        if (!access_ok(VERIFY_READ, buf, count))
 601                return -EFAULT;
 602        while (count-- > 0 && i < 65536) {
 603                char c;
 604                if (__get_user(c, tmp)) {
 605                        if (tmp > buf)
 606                                break;
 607                        return -EFAULT;
 608                }
 609                outb(c, i);
 610                i++;
 611                tmp++;
 612        }
 613        *ppos = i;
 614        return tmp-buf;
 615}
 616#endif
 617
 618static ssize_t read_null(struct file *file, char __user *buf,
 619                         size_t count, loff_t *ppos)
 620{
 621        return 0;
 622}
 623
 624static ssize_t write_null(struct file *file, const char __user *buf,
 625                          size_t count, loff_t *ppos)
 626{
 627        return count;
 628}
 629
 630static int pipe_to_null(struct pipe_inode_info *info, struct pipe_buffer *buf,
 631                        struct splice_desc *sd)
 632{
 633        return sd->len;
 634}
 635
 636static ssize_t splice_write_null(struct pipe_inode_info *pipe, struct file *out,
 637                                 loff_t *ppos, size_t len, unsigned int flags)
 638{
 639        return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_null);
 640}
 641
 642static ssize_t read_zero(struct file *file, char __user *buf,
 643                         size_t count, loff_t *ppos)
 644{
 645        size_t written;
 646
 647        if (!count)
 648                return 0;
 649
 650        if (!access_ok(VERIFY_WRITE, buf, count))
 651                return -EFAULT;
 652
 653        written = 0;
 654        while (count) {
 655                unsigned long unwritten;
 656                size_t chunk = count;
 657
 658                if (chunk > PAGE_SIZE)
 659                        chunk = PAGE_SIZE;      /* Just for latency reasons */
 660                unwritten = __clear_user(buf, chunk);
 661                written += chunk - unwritten;
 662                if (unwritten)
 663                        break;
 664                if (signal_pending(current))
 665                        return written ? written : -ERESTARTSYS;
 666                buf += chunk;
 667                count -= chunk;
 668                cond_resched();
 669        }
 670        return written ? written : -EFAULT;
 671}
 672
 673static int mmap_zero(struct file *file, struct vm_area_struct *vma)
 674{
 675#ifndef CONFIG_MMU
 676        return -ENOSYS;
 677#endif
 678        if (vma->vm_flags & VM_SHARED)
 679                return shmem_zero_setup(vma);
 680        return 0;
 681}
 682
 683static ssize_t write_full(struct file *file, const char __user *buf,
 684                          size_t count, loff_t *ppos)
 685{
 686        return -ENOSPC;
 687}
 688
 689/*
 690 * Special lseek() function for /dev/null and /dev/zero.  Most notably, you
 691 * can fopen() both devices with "a" now.  This was previously impossible.
 692 * -- SRB.
 693 */
 694static loff_t null_lseek(struct file *file, loff_t offset, int orig)
 695{
 696        return file->f_pos = 0;
 697}
 698
 699/*
 700 * The memory devices use the full 32/64 bits of the offset, and so we cannot
 701 * check against negative addresses: they are ok. The return value is weird,
 702 * though, in that case (0).
 703 *
 704 * also note that seeking relative to the "end of file" isn't supported:
 705 * it has no meaning, so it returns -EINVAL.
 706 */
 707static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
 708{
 709        loff_t ret;
 710
 711        mutex_lock(&file->f_path.dentry->d_inode->i_mutex);
 712        switch (orig) {
 713        case SEEK_CUR:
 714                offset += file->f_pos;
 715        case SEEK_SET:
 716                /* to avoid userland mistaking f_pos=-9 as -EBADF=-9 */
 717                if ((unsigned long long)offset >= ~0xFFFULL) {
 718                        ret = -EOVERFLOW;
 719                        break;
 720                }
 721                file->f_pos = offset;
 722                ret = file->f_pos;
 723                force_successful_syscall_return();
 724                break;
 725        default:
 726                ret = -EINVAL;
 727        }
 728        mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
 729        return ret;
 730}
 731
 732static int open_port(struct inode * inode, struct file * filp)
 733{
 734        return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
 735}
 736
 737#define zero_lseek      null_lseek
 738#define full_lseek      null_lseek
 739#define write_zero      write_null
 740#define read_full       read_zero
 741#define open_mem        open_port
 742#define open_kmem       open_mem
 743#define open_oldmem     open_mem
 744
 745static const struct file_operations mem_fops = {
 746        .llseek         = memory_lseek,
 747        .read           = read_mem,
 748        .write          = write_mem,
 749        .mmap           = mmap_mem,
 750        .open           = open_mem,
 751        .get_unmapped_area = get_unmapped_area_mem,
 752};
 753
 754#ifdef CONFIG_DEVKMEM
 755static const struct file_operations kmem_fops = {
 756        .llseek         = memory_lseek,
 757        .read           = read_kmem,
 758        .write          = write_kmem,
 759        .mmap           = mmap_kmem,
 760        .open           = open_kmem,
 761        .get_unmapped_area = get_unmapped_area_mem,
 762};
 763#endif
 764
 765static const struct file_operations null_fops = {
 766        .llseek         = null_lseek,
 767        .read           = read_null,
 768        .write          = write_null,
 769        .splice_write   = splice_write_null,
 770};
 771
 772#ifdef CONFIG_DEVPORT
 773static const struct file_operations port_fops = {
 774        .llseek         = memory_lseek,
 775        .read           = read_port,
 776        .write          = write_port,
 777        .open           = open_port,
 778};
 779#endif
 780
 781static const struct file_operations zero_fops = {
 782        .llseek         = zero_lseek,
 783        .read           = read_zero,
 784        .write          = write_zero,
 785        .mmap           = mmap_zero,
 786};
 787
 788/*
 789 * capabilities for /dev/zero
 790 * - permits private mappings, "copies" are taken of the source of zeros
 791 * - no writeback happens
 792 */
 793static struct backing_dev_info zero_bdi = {
 794        .name           = "char/mem",
 795        .capabilities   = BDI_CAP_MAP_COPY | BDI_CAP_NO_ACCT_AND_WRITEBACK,
 796};
 797
 798static const struct file_operations full_fops = {
 799        .llseek         = full_lseek,
 800        .read           = read_full,
 801        .write          = write_full,
 802};
 803
 804#ifdef CONFIG_CRASH_DUMP
 805static const struct file_operations oldmem_fops = {
 806        .read   = read_oldmem,
 807        .open   = open_oldmem,
 808        .llseek = default_llseek,
 809};
 810#endif
 811
 812static const struct memdev {
 813        const char *name;
 814        umode_t mode;
 815        const struct file_operations *fops;
 816        struct backing_dev_info *dev_info;
 817} devlist[] = {
 818         [1] = { "mem", 0, &mem_fops, &directly_mappable_cdev_bdi },
 819#ifdef CONFIG_DEVKMEM
 820         [2] = { "kmem", 0, &kmem_fops, &directly_mappable_cdev_bdi },
 821#endif
 822         [3] = { "null", 0666, &null_fops, NULL },
 823#ifdef CONFIG_DEVPORT
 824         [4] = { "port", 0, &port_fops, NULL },
 825#endif
 826         [5] = { "zero", 0666, &zero_fops, &zero_bdi },
 827         [7] = { "full", 0666, &full_fops, NULL },
 828         [8] = { "random", 0666, &random_fops, NULL },
 829         [9] = { "urandom", 0666, &urandom_fops, NULL },
 830#ifdef CONFIG_PRINTK
 831        [11] = { "kmsg", 0644, &kmsg_fops, NULL },
 832#endif
 833#ifdef CONFIG_CRASH_DUMP
 834        [12] = { "oldmem", 0, &oldmem_fops, NULL },
 835#endif
 836};
 837
 838static int memory_open(struct inode *inode, struct file *filp)
 839{
 840        int minor;
 841        const struct memdev *dev;
 842
 843        minor = iminor(inode);
 844        if (minor >= ARRAY_SIZE(devlist))
 845                return -ENXIO;
 846
 847        dev = &devlist[minor];
 848        if (!dev->fops)
 849                return -ENXIO;
 850
 851        filp->f_op = dev->fops;
 852        if (dev->dev_info)
 853                filp->f_mapping->backing_dev_info = dev->dev_info;
 854
 855        /* Is /dev/mem or /dev/kmem ? */
 856        if (dev->dev_info == &directly_mappable_cdev_bdi)
 857                filp->f_mode |= FMODE_UNSIGNED_OFFSET;
 858
 859        if (dev->fops->open)
 860                return dev->fops->open(inode, filp);
 861
 862        return 0;
 863}
 864
 865static const struct file_operations memory_fops = {
 866        .open = memory_open,
 867        .llseek = noop_llseek,
 868};
 869
 870static char *mem_devnode(struct device *dev, umode_t *mode)
 871{
 872        if (mode && devlist[MINOR(dev->devt)].mode)
 873                *mode = devlist[MINOR(dev->devt)].mode;
 874        return NULL;
 875}
 876
 877static struct class *mem_class;
 878
 879static int __init chr_dev_init(void)
 880{
 881        int minor;
 882        int err;
 883
 884        err = bdi_init(&zero_bdi);
 885        if (err)
 886                return err;
 887
 888        if (register_chrdev(MEM_MAJOR, "mem", &memory_fops))
 889                printk("unable to get major %d for memory devs\n", MEM_MAJOR);
 890
 891        mem_class = class_create(THIS_MODULE, "mem");
 892        if (IS_ERR(mem_class))
 893                return PTR_ERR(mem_class);
 894
 895        mem_class->devnode = mem_devnode;
 896        for (minor = 1; minor < ARRAY_SIZE(devlist); minor++) {
 897                if (!devlist[minor].name)
 898                        continue;
 899
 900                /*
 901                 * Create /dev/port? 
 902                 */
 903                if ((minor == DEVPORT_MINOR) && !arch_has_dev_port())
 904                        continue;
 905
 906                device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor),
 907                              NULL, devlist[minor].name);
 908        }
 909
 910        return tty_init();
 911}
 912
 913fs_initcall(chr_dev_init);
 914
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