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