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
  31#include <asm/uaccess.h>
  32#include <asm/io.h>
  33
  34#ifdef CONFIG_IA64
  35# include <linux/efi.h>
  36#endif
  37
  38static inline unsigned long size_inside_page(unsigned long start,
  39                                             unsigned long size)
  40{
  41        unsigned long sz;
  42
  43        sz = PAGE_SIZE - (start & (PAGE_SIZE - 1));
  44
  45        return min(sz, size);
  46}
  47
  48#ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE
  49static inline int valid_phys_addr_range(unsigned long addr, size_t count)
  50{
  51        return addr + count <= __pa(high_memory);
  52}
  53
  54static inline int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
  55{
  56        return 1;
  57}
  58#endif
  59
  60#ifdef CONFIG_STRICT_DEVMEM
  61static inline int range_is_allowed(unsigned long pfn, unsigned long size)
  62{
  63        u64 from = ((u64)pfn) << PAGE_SHIFT;
  64        u64 to = from + size;
  65        u64 cursor = from;
  66
  67        while (cursor < to) {
  68                if (!devmem_is_allowed(pfn)) {
  69                        printk(KERN_INFO
  70                "Program %s tried to access /dev/mem between %Lx->%Lx.\n",
  71                                current->comm, from, to);
  72                        return 0;
  73                }
  74                cursor += PAGE_SIZE;
  75                pfn++;
  76        }
  77        return 1;
  78}
  79#else
  80static inline int range_is_allowed(unsigned long pfn, unsigned long size)
  81{
  82        return 1;
  83}
  84#endif
  85
  86void __weak unxlate_dev_mem_ptr(unsigned long phys, void *addr)
  87{
  88}
  89
  90/*
  91 * This funcion reads the *physical* memory. The f_pos points directly to the
  92 * memory location.
  93 */
  94static ssize_t read_mem(struct file *file, char __user *buf,
  95                        size_t count, loff_t *ppos)
  96{
  97        unsigned long p = *ppos;
  98        ssize_t read, sz;
  99        char *ptr;
 100
 101        if (!valid_phys_addr_range(p, count))
 102                return -EFAULT;
 103        read = 0;
 104#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 105        /* we don't have page 0 mapped on sparc and m68k.. */
 106        if (p < PAGE_SIZE) {
 107                sz = size_inside_page(p, count);
 108                if (sz > 0) {
 109                        if (clear_user(buf, sz))
 110                                return -EFAULT;
 111                        buf += sz;
 112                        p += sz;
 113                        count -= sz;
 114                        read += sz;
 115                }
 116        }
 117#endif
 118
 119        while (count > 0) {
 120                unsigned long remaining;
 121
 122                sz = size_inside_page(p, count);
 123
 124                if (!range_is_allowed(p >> PAGE_SHIFT, count))
 125                        return -EPERM;
 126
 127                /*
 128                 * On ia64 if a page has been mapped somewhere as uncached, then
 129                 * it must also be accessed uncached by the kernel or data
 130                 * corruption may occur.
 131                 */
 132                ptr = xlate_dev_mem_ptr(p);
 133                if (!ptr)
 134                        return -EFAULT;
 135
 136                remaining = copy_to_user(buf, ptr, sz);
 137                unxlate_dev_mem_ptr(p, ptr);
 138                if (remaining)
 139                        return -EFAULT;
 140
 141                buf += sz;
 142                p += sz;
 143                count -= sz;
 144                read += sz;
 145        }
 146
 147        *ppos += read;
 148        return read;
 149}
 150
 151static ssize_t write_mem(struct file *file, const char __user *buf,
 152                         size_t count, loff_t *ppos)
 153{
 154        unsigned long p = *ppos;
 155        ssize_t written, sz;
 156        unsigned long copied;
 157        void *ptr;
 158
 159        if (!valid_phys_addr_range(p, count))
 160                return -EFAULT;
 161
 162        written = 0;
 163
 164#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 165        /* we don't have page 0 mapped on sparc and m68k.. */
 166        if (p < PAGE_SIZE) {
 167                sz = size_inside_page(p, count);
 168                /* Hmm. Do something? */
 169                buf += sz;
 170                p += sz;
 171                count -= sz;
 172                written += sz;
 173        }
 174#endif
 175
 176        while (count > 0) {
 177                sz = size_inside_page(p, count);
 178
 179                if (!range_is_allowed(p >> PAGE_SHIFT, sz))
 180                        return -EPERM;
 181
 182                /*
 183                 * On ia64 if a page has been mapped somewhere as uncached, then
 184                 * it must also be accessed uncached by the kernel or data
 185                 * corruption may occur.
 186                 */
 187                ptr = xlate_dev_mem_ptr(p);
 188                if (!ptr) {
 189                        if (written)
 190                                break;
 191                        return -EFAULT;
 192                }
 193
 194                copied = copy_from_user(ptr, buf, sz);
 195                unxlate_dev_mem_ptr(p, ptr);
 196                if (copied) {
 197                        written += sz - copied;
 198                        if (written)
 199                                break;
 200                        return -EFAULT;
 201                }
 202
 203                buf += sz;
 204                p += sz;
 205                count -= sz;
 206                written += sz;
 207        }
 208
 209        *ppos += written;
 210        return written;
 211}
 212
 213int __weak phys_mem_access_prot_allowed(struct file *file,
 214        unsigned long pfn, unsigned long size, pgprot_t *vma_prot)
 215{
 216        return 1;
 217}
 218
 219#ifndef __HAVE_PHYS_MEM_ACCESS_PROT
 220
 221/*
 222 * Architectures vary in how they handle caching for addresses
 223 * outside of main memory.
 224 *
 225 */
 226#ifdef pgprot_noncached
 227static int uncached_access(struct file *file, unsigned long addr)
 228{
 229#if defined(CONFIG_IA64)
 230        /*
 231         * On ia64, we ignore O_DSYNC because we cannot tolerate memory
 232         * attribute aliases.
 233         */
 234        return !(efi_mem_attributes(addr) & EFI_MEMORY_WB);
 235#elif defined(CONFIG_MIPS)
 236        {
 237                extern int __uncached_access(struct file *file,
 238                                             unsigned long addr);
 239
 240                return __uncached_access(file, addr);
 241        }
 242#else
 243        /*
 244         * Accessing memory above the top the kernel knows about or through a
 245         * file pointer
 246         * that was marked O_DSYNC will be done non-cached.
 247         */
 248        if (file->f_flags & O_DSYNC)
 249                return 1;
 250        return addr >= __pa(high_memory);
 251#endif
 252}
 253#endif
 254
 255static pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 256                                     unsigned long size, pgprot_t vma_prot)
 257{
 258#ifdef pgprot_noncached
 259        unsigned long offset = pfn << PAGE_SHIFT;
 260
 261        if (uncached_access(file, offset))
 262                return pgprot_noncached(vma_prot);
 263#endif
 264        return vma_prot;
 265}
 266#endif
 267
 268#ifndef CONFIG_MMU
 269static unsigned long get_unmapped_area_mem(struct file *file,
 270                                           unsigned long addr,
 271                                           unsigned long len,
 272                                           unsigned long pgoff,
 273                                           unsigned long flags)
 274{
 275        if (!valid_mmap_phys_addr_range(pgoff, len))
 276                return (unsigned long) -EINVAL;
 277        return pgoff << PAGE_SHIFT;
 278}
 279
 280/* can't do an in-place private mapping if there's no MMU */
 281static inline int private_mapping_ok(struct vm_area_struct *vma)
 282{
 283        return vma->vm_flags & VM_MAYSHARE;
 284}
 285#else
 286#define get_unmapped_area_mem   NULL
 287
 288static inline int private_mapping_ok(struct vm_area_struct *vma)
 289{
 290        return 1;
 291}
 292#endif
 293
 294static const struct vm_operations_struct mmap_mem_ops = {
 295#ifdef CONFIG_HAVE_IOREMAP_PROT
 296        .access = generic_access_phys
 297#endif
 298};
 299
 300static int mmap_mem(struct file *file, struct vm_area_struct *vma)
 301{
 302        size_t size = vma->vm_end - vma->vm_start;
 303
 304        if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))
 305                return -EINVAL;
 306
 307        if (!private_mapping_ok(vma))
 308                return -ENOSYS;
 309
 310        if (!range_is_allowed(vma->vm_pgoff, size))
 311                return -EPERM;
 312
 313        if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size,
 314                                                &vma->vm_page_prot))
 315                return -EINVAL;
 316
 317        vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,
 318                                                 size,
 319                                                 vma->vm_page_prot);
 320
 321        vma->vm_ops = &mmap_mem_ops;
 322
 323        /* Remap-pfn-range will mark the range VM_IO and VM_RESERVED */
 324        if (remap_pfn_range(vma,
 325                            vma->vm_start,
 326                            vma->vm_pgoff,
 327                            size,
 328                            vma->vm_page_prot)) {
 329                return -EAGAIN;
 330        }
 331        return 0;
 332}
 333
 334#ifdef CONFIG_DEVKMEM
 335static int mmap_kmem(struct file *file, struct vm_area_struct *vma)
 336{
 337        unsigned long pfn;
 338
 339        /* Turn a kernel-virtual address into a physical page frame */
 340        pfn = __pa((u64)vma->vm_pgoff << PAGE_SHIFT) >> PAGE_SHIFT;
 341
 342        /*
 343         * RED-PEN: on some architectures there is more mapped memory than
 344         * available in mem_map which pfn_valid checks for. Perhaps should add a
 345         * new macro here.
 346         *
 347         * RED-PEN: vmalloc is not supported right now.
 348         */
 349        if (!pfn_valid(pfn))
 350                return -EIO;
 351
 352        vma->vm_pgoff = pfn;
 353        return mmap_mem(file, vma);
 354}
 355#endif
 356
 357#ifdef CONFIG_CRASH_DUMP
 358/*
 359 * Read memory corresponding to the old kernel.
 360 */
 361static ssize_t read_oldmem(struct file *file, char __user *buf,
 362                                size_t count, loff_t *ppos)
 363{
 364        unsigned long pfn, offset;
 365        size_t read = 0, csize;
 366        int rc = 0;
 367
 368        while (count) {
 369                pfn = *ppos / PAGE_SIZE;
 370                if (pfn > saved_max_pfn)
 371                        return read;
 372
 373                offset = (unsigned long)(*ppos % PAGE_SIZE);
 374                if (count > PAGE_SIZE - offset)
 375                        csize = PAGE_SIZE - offset;
 376                else
 377                        csize = count;
 378
 379                rc = copy_oldmem_page(pfn, buf, csize, offset, 1);
 380                if (rc < 0)
 381                        return rc;
 382                buf += csize;
 383                *ppos += csize;
 384                read += csize;
 385                count -= csize;
 386        }
 387        return read;
 388}
 389#endif
 390
 391#ifdef CONFIG_DEVKMEM
 392/*
 393 * This function reads the *virtual* memory as seen by the kernel.
 394 */
 395static ssize_t read_kmem(struct file *file, char __user *buf,
 396                         size_t count, loff_t *ppos)
 397{
 398        unsigned long p = *ppos;
 399        ssize_t low_count, read, sz;
 400        char * kbuf; /* k-addr because vread() takes vmlist_lock rwlock */
 401        int err = 0;
 402
 403        read = 0;
 404        if (p < (unsigned long) high_memory) {
 405                low_count = count;
 406                if (count > (unsigned long)high_memory - p)
 407                        low_count = (unsigned long)high_memory - p;
 408
 409#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 410                /* we don't have page 0 mapped on sparc and m68k.. */
 411                if (p < PAGE_SIZE && low_count > 0) {
 412                        sz = size_inside_page(p, low_count);
 413                        if (clear_user(buf, sz))
 414                                return -EFAULT;
 415                        buf += sz;
 416                        p += sz;
 417                        read += sz;
 418                        low_count -= sz;
 419                        count -= sz;
 420                }
 421#endif
 422                while (low_count > 0) {
 423                        sz = size_inside_page(p, low_count);
 424
 425                        /*
 426                         * On ia64 if a page has been mapped somewhere as
 427                         * uncached, then it must also be accessed uncached
 428                         * by the kernel or data corruption may occur
 429                         */
 430                        kbuf = xlate_dev_kmem_ptr((char *)p);
 431
 432                        if (copy_to_user(buf, kbuf, sz))
 433                                return -EFAULT;
 434                        buf += sz;
 435                        p += sz;
 436                        read += sz;
 437                        low_count -= sz;
 438                        count -= sz;
 439                }
 440        }
 441
 442        if (count > 0) {
 443                kbuf = (char *)__get_free_page(GFP_KERNEL);
 444                if (!kbuf)
 445                        return -ENOMEM;
 446                while (count > 0) {
 447                        sz = size_inside_page(p, count);
 448                        if (!is_vmalloc_or_module_addr((void *)p)) {
 449                                err = -ENXIO;
 450                                break;
 451                        }
 452                        sz = vread(kbuf, (char *)p, sz);
 453                        if (!sz)
 454                                break;
 455                        if (copy_to_user(buf, kbuf, sz)) {
 456                                err = -EFAULT;
 457                                break;
 458                        }
 459                        count -= sz;
 460                        buf += sz;
 461                        read += sz;
 462                        p += sz;
 463                }
 464                free_page((unsigned long)kbuf);
 465        }
 466        *ppos = p;
 467        return read ? read : err;
 468}
 469
 470
 471static ssize_t do_write_kmem(unsigned long p, const char __user *buf,
 472                                size_t count, loff_t *ppos)
 473{
 474        ssize_t written, sz;
 475        unsigned long copied;
 476
 477        written = 0;
 478#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 479        /* we don't have page 0 mapped on sparc and m68k.. */
 480        if (p < PAGE_SIZE) {
 481                sz = size_inside_page(p, count);
 482                /* Hmm. Do something? */
 483                buf += sz;
 484                p += sz;
 485                count -= sz;
 486                written += sz;
 487        }
 488#endif
 489
 490        while (count > 0) {
 491                char *ptr;
 492
 493                sz = size_inside_page(p, count);
 494
 495                /*
 496                 * On ia64 if a page has been mapped somewhere as uncached, then
 497                 * it must also be accessed uncached by the kernel or data
 498                 * corruption may occur.
 499                 */
 500                ptr = xlate_dev_kmem_ptr((char *)p);
 501
 502                copied = copy_from_user(ptr, buf, sz);
 503                if (copied) {
 504                        written += sz - copied;
 505                        if (written)
 506                                break;
 507                        return -EFAULT;
 508                }
 509                buf += sz;
 510                p += sz;
 511                count -= sz;
 512                written += sz;
 513        }
 514
 515        *ppos += written;
 516        return written;
 517}
 518
 519/*
 520 * This function writes to the *virtual* memory as seen by the kernel.
 521 */
 522static ssize_t write_kmem(struct file *file, const char __user *buf,
 523                          size_t count, loff_t *ppos)
 524{
 525        unsigned long p = *ppos;
 526        ssize_t wrote = 0;
 527        ssize_t virtr = 0;
 528        char * kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
 529        int err = 0;
 530
 531        if (p < (unsigned long) high_memory) {
 532                unsigned long to_write = min_t(unsigned long, count,
 533                                               (unsigned long)high_memory - p);
 534                wrote = do_write_kmem(p, buf, to_write, ppos);
 535                if (wrote != to_write)
 536                        return wrote;
 537                p += wrote;
 538                buf += wrote;
 539                count -= wrote;
 540        }
 541
 542        if (count > 0) {
 543                kbuf = (char *)__get_free_page(GFP_KERNEL);
 544                if (!kbuf)
 545                        return wrote ? wrote : -ENOMEM;
 546                while (count > 0) {
 547                        unsigned long sz = size_inside_page(p, count);
 548                        unsigned long n;
 549
 550                        if (!is_vmalloc_or_module_addr((void *)p)) {
 551                                err = -ENXIO;
 552                                break;
 553                        }
 554                        n = copy_from_user(kbuf, buf, sz);
 555                        if (n) {
 556                                err = -EFAULT;
 557                                break;
 558                        }
 559                        vwrite(kbuf, (char *)p, sz);
 560                        count -= sz;
 561                        buf += sz;
 562                        virtr += sz;
 563                        p += sz;
 564                }
 565                free_page((unsigned long)kbuf);
 566        }
 567
 568        *ppos = p;
 569        return virtr + wrote ? : err;
 570}
 571#endif
 572
 573#ifdef CONFIG_DEVPORT
 574static ssize_t read_port(struct file *file, char __user *buf,
 575                         size_t count, loff_t *ppos)
 576{
 577        unsigned long i = *ppos;
 578        char __user *tmp = buf;
 579
 580        if (!access_ok(VERIFY_WRITE, buf, count))
 581                return -EFAULT;
 582        while (count-- > 0 && i < 65536) {
 583                if (__put_user(inb(i), tmp) < 0)
 584                        return -EFAULT;
 585                i++;
 586                tmp++;
 587        }
 588        *ppos = i;
 589        return tmp-buf;
 590}
 591
 592static ssize_t write_port(struct file *file, const char __user *buf,
 593                          size_t count, loff_t *ppos)
 594{
 595        unsigned long i = *ppos;
 596        const char __user * tmp = buf;
 597
 598        if (!access_ok(VERIFY_READ, buf, count))
 599                return -EFAULT;
 600        while (count-- > 0 && i < 65536) {
 601                char c;
 602                if (__get_user(c, tmp)) {
 603                        if (tmp > buf)
 604                                break;
 605                        return -EFAULT;
 606                }
 607                outb(c, i);
 608                i++;
 609                tmp++;
 610        }
 611        *ppos = i;
 612        return tmp-buf;
 613}
 614#endif
 615
 616static ssize_t read_null(struct file *file, char __user *buf,
 617                         size_t count, loff_t *ppos)
 618{
 619        return 0;
 620}
 621
 622static ssize_t write_null(struct file *file, const char __user *buf,
 623                          size_t count, loff_t *ppos)
 624{
 625        return count;
 626}
 627
 628static int pipe_to_null(struct pipe_inode_info *info, struct pipe_buffer *buf,
 629                        struct splice_desc *sd)
 630{
 631        return sd->len;
 632}
 633
 634static ssize_t splice_write_null(struct pipe_inode_info *pipe, struct file *out,
 635                                 loff_t *ppos, size_t len, unsigned int flags)
 636{
 637        return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_null);
 638}
 639
 640static ssize_t read_zero(struct file *file, char __user *buf,
 641                         size_t count, loff_t *ppos)
 642{
 643        size_t written;
 644
 645        if (!count)
 646                return 0;
 647
 648        if (!access_ok(VERIFY_WRITE, buf, count))
 649                return -EFAULT;
 650
 651        written = 0;
 652        while (count) {
 653                unsigned long unwritten;
 654                size_t chunk = count;
 655
 656                if (chunk > PAGE_SIZE)
 657                        chunk = PAGE_SIZE;      /* Just for latency reasons */
 658                unwritten = __clear_user(buf, chunk);
 659                written += chunk - unwritten;
 660                if (unwritten)
 661                        break;
 662                if (signal_pending(current))
 663                        return written ? written : -ERESTARTSYS;
 664                buf += chunk;
 665                count -= chunk;
 666                cond_resched();
 667        }
 668        return written ? written : -EFAULT;
 669}
 670
 671static int mmap_zero(struct file *file, struct vm_area_struct *vma)
 672{
 673#ifndef CONFIG_MMU
 674        return -ENOSYS;
 675#endif
 676        if (vma->vm_flags & VM_SHARED)
 677                return shmem_zero_setup(vma);
 678        return 0;
 679}
 680
 681static ssize_t write_full(struct file *file, const char __user *buf,
 682                          size_t count, loff_t *ppos)
 683{
 684        return -ENOSPC;
 685}
 686
 687/*
 688 * Special lseek() function for /dev/null and /dev/zero.  Most notably, you
 689 * can fopen() both devices with "a" now.  This was previously impossible.
 690 * -- SRB.
 691 */
 692static loff_t null_lseek(struct file *file, loff_t offset, int orig)
 693{
 694        return file->f_pos = 0;
 695}
 696
 697/*
 698 * The memory devices use the full 32/64 bits of the offset, and so we cannot
 699 * check against negative addresses: they are ok. The return value is weird,
 700 * though, in that case (0).
 701 *
 702 * also note that seeking relative to the "end of file" isn't supported:
 703 * it has no meaning, so it returns -EINVAL.
 704 */
 705static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
 706{
 707        loff_t ret;
 708
 709        mutex_lock(&file->f_path.dentry->d_inode->i_mutex);
 710        switch (orig) {
 711        case SEEK_CUR:
 712                offset += file->f_pos;
 713        case SEEK_SET:
 714                /* to avoid userland mistaking f_pos=-9 as -EBADF=-9 */
 715                if ((unsigned long long)offset >= ~0xFFFULL) {
 716                        ret = -EOVERFLOW;
 717                        break;
 718                }
 719                file->f_pos = offset;
 720                ret = file->f_pos;
 721                force_successful_syscall_return();
 722                break;
 723        default:
 724                ret = -EINVAL;
 725        }
 726        mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
 727        return ret;
 728}
 729
 730static int open_port(struct inode * inode, struct file * filp)
 731{
 732        return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
 733}
 734
 735#define zero_lseek      null_lseek
 736#define full_lseek      null_lseek
 737#define write_zero      write_null
 738#define read_full       read_zero
 739#define open_mem        open_port
 740#define open_kmem       open_mem
 741#define open_oldmem     open_mem
 742
 743static const struct file_operations mem_fops = {
 744        .llseek         = memory_lseek,
 745        .read           = read_mem,
 746        .write          = write_mem,
 747        .mmap           = mmap_mem,
 748        .open           = open_mem,
 749        .get_unmapped_area = get_unmapped_area_mem,
 750};
 751
 752#ifdef CONFIG_DEVKMEM
 753static const struct file_operations kmem_fops = {
 754        .llseek         = memory_lseek,
 755        .read           = read_kmem,
 756        .write          = write_kmem,
 757        .mmap           = mmap_kmem,
 758        .open           = open_kmem,
 759        .get_unmapped_area = get_unmapped_area_mem,
 760};
 761#endif
 762
 763static const struct file_operations null_fops = {
 764        .llseek         = null_lseek,
 765        .read           = read_null,
 766        .write          = write_null,
 767        .splice_write   = splice_write_null,
 768};
 769
 770#ifdef CONFIG_DEVPORT
 771static const struct file_operations port_fops = {
 772        .llseek         = memory_lseek,
 773        .read           = read_port,
 774        .write          = write_port,
 775        .open           = open_port,
 776};
 777#endif
 778
 779static const struct file_operations zero_fops = {
 780        .llseek         = zero_lseek,
 781        .read           = read_zero,
 782        .write          = write_zero,
 783        .mmap           = mmap_zero,
 784};
 785
 786/*
 787 * capabilities for /dev/zero
 788 * - permits private mappings, "copies" are taken of the source of zeros
 789 * - no writeback happens
 790 */
 791static struct backing_dev_info zero_bdi = {
 792        .name           = "char/mem",
 793        .capabilities   = BDI_CAP_MAP_COPY | BDI_CAP_NO_ACCT_AND_WRITEBACK,
 794};
 795
 796static const struct file_operations full_fops = {
 797        .llseek         = full_lseek,
 798        .read           = read_full,
 799        .write          = write_full,
 800};
 801
 802#ifdef CONFIG_CRASH_DUMP
 803static const struct file_operations oldmem_fops = {
 804        .read   = read_oldmem,
 805        .open   = open_oldmem,
 806        .llseek = default_llseek,
 807};
 808#endif
 809
 810static ssize_t kmsg_writev(struct kiocb *iocb, const struct iovec *iv,
 811                           unsigned long count, loff_t pos)
 812{
 813        char *line, *p;
 814        int i;
 815        ssize_t ret = -EFAULT;
 816        size_t len = iov_length(iv, count);
 817
 818        line = kmalloc(len + 1, GFP_KERNEL);
 819        if (line == NULL)
 820                return -ENOMEM;
 821
 822        /*
 823         * copy all vectors into a single string, to ensure we do
 824         * not interleave our log line with other printk calls
 825         */
 826        p = line;
 827        for (i = 0; i < count; i++) {
 828                if (copy_from_user(p, iv[i].iov_base, iv[i].iov_len))
 829                        goto out;
 830                p += iv[i].iov_len;
 831        }
 832        p[0] = '\0';
 833
 834        ret = printk("%s", line);
 835        /* printk can add a prefix */
 836        if (ret > len)
 837                ret = len;
 838out:
 839        kfree(line);
 840        return ret;
 841}
 842
 843static const struct file_operations kmsg_fops = {
 844        .aio_write = kmsg_writev,
 845        .llseek = noop_llseek,
 846};
 847
 848static const struct memdev {
 849        const char *name;
 850        mode_t mode;
 851        const struct file_operations *fops;
 852        struct backing_dev_info *dev_info;
 853} devlist[] = {
 854         [1] = { "mem", 0, &mem_fops, &directly_mappable_cdev_bdi },
 855#ifdef CONFIG_DEVKMEM
 856         [2] = { "kmem", 0, &kmem_fops, &directly_mappable_cdev_bdi },
 857#endif
 858         [3] = { "null", 0666, &null_fops, NULL },
 859#ifdef CONFIG_DEVPORT
 860         [4] = { "port", 0, &port_fops, NULL },
 861#endif
 862         [5] = { "zero", 0666, &zero_fops, &zero_bdi },
 863         [7] = { "full", 0666, &full_fops, NULL },
 864         [8] = { "random", 0666, &random_fops, NULL },
 865         [9] = { "urandom", 0666, &urandom_fops, NULL },
 866        [11] = { "kmsg", 0, &kmsg_fops, NULL },
 867#ifdef CONFIG_CRASH_DUMP
 868        [12] = { "oldmem", 0, &oldmem_fops, NULL },
 869#endif
 870};
 871
 872static int memory_open(struct inode *inode, struct file *filp)
 873{
 874        int minor;
 875        const struct memdev *dev;
 876
 877        minor = iminor(inode);
 878        if (minor >= ARRAY_SIZE(devlist))
 879                return -ENXIO;
 880
 881        dev = &devlist[minor];
 882        if (!dev->fops)
 883                return -ENXIO;
 884
 885        filp->f_op = dev->fops;
 886        if (dev->dev_info)
 887                filp->f_mapping->backing_dev_info = dev->dev_info;
 888
 889        /* Is /dev/mem or /dev/kmem ? */
 890        if (dev->dev_info == &directly_mappable_cdev_bdi)
 891                filp->f_mode |= FMODE_UNSIGNED_OFFSET;
 892
 893        if (dev->fops->open)
 894                return dev->fops->open(inode, filp);
 895
 896        return 0;
 897}
 898
 899static const struct file_operations memory_fops = {
 900        .open = memory_open,
 901        .llseek = noop_llseek,
 902};
 903
 904static char *mem_devnode(struct device *dev, mode_t *mode)
 905{
 906        if (mode && devlist[MINOR(dev->devt)].mode)
 907                *mode = devlist[MINOR(dev->devt)].mode;
 908        return NULL;
 909}
 910
 911static struct class *mem_class;
 912
 913static int __init chr_dev_init(void)
 914{
 915        int minor;
 916        int err;
 917
 918        err = bdi_init(&zero_bdi);
 919        if (err)
 920                return err;
 921
 922        if (register_chrdev(MEM_MAJOR, "mem", &memory_fops))
 923                printk("unable to get major %d for memory devs\n", MEM_MAJOR);
 924
 925        mem_class = class_create(THIS_MODULE, "mem");
 926        if (IS_ERR(mem_class))
 927                return PTR_ERR(mem_class);
 928
 929        mem_class->devnode = mem_devnode;
 930        for (minor = 1; minor < ARRAY_SIZE(devlist); minor++) {
 931                if (!devlist[minor].name)
 932                        continue;
 933                device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor),
 934                              NULL, devlist[minor].name);
 935        }
 936
 937        return tty_init();
 938}
 939
 940fs_initcall(chr_dev_init);
 941
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