linux/drivers/char/mem.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 *  linux/drivers/char/mem.c
   4 *
   5 *  Copyright (C) 1991, 1992  Linus Torvalds
   6 *
   7 *  Added devfs support.
   8 *    Jan-11-1998, C. Scott Ananian <cananian@alumni.princeton.edu>
   9 *  Shared /dev/zero mmapping support, Feb 2000, Kanoj Sarcar <kanoj@sgi.com>
  10 */
  11
  12#include <linux/mm.h>
  13#include <linux/miscdevice.h>
  14#include <linux/slab.h>
  15#include <linux/vmalloc.h>
  16#include <linux/mman.h>
  17#include <linux/random.h>
  18#include <linux/init.h>
  19#include <linux/raw.h>
  20#include <linux/tty.h>
  21#include <linux/capability.h>
  22#include <linux/ptrace.h>
  23#include <linux/device.h>
  24#include <linux/highmem.h>
  25#include <linux/backing-dev.h>
  26#include <linux/shmem_fs.h>
  27#include <linux/splice.h>
  28#include <linux/pfn.h>
  29#include <linux/export.h>
  30#include <linux/io.h>
  31#include <linux/uio.h>
  32
  33#include <linux/uaccess.h>
  34
  35#ifdef CONFIG_IA64
  36# include <linux/efi.h>
  37#endif
  38
  39#define DEVPORT_MINOR   4
  40
  41static inline unsigned long size_inside_page(unsigned long start,
  42                                             unsigned long size)
  43{
  44        unsigned long sz;
  45
  46        sz = PAGE_SIZE - (start & (PAGE_SIZE - 1));
  47
  48        return min(sz, size);
  49}
  50
  51#ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE
  52static inline int valid_phys_addr_range(phys_addr_t addr, size_t count)
  53{
  54        return addr + count <= __pa(high_memory);
  55}
  56
  57static inline int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
  58{
  59        return 1;
  60}
  61#endif
  62
  63#ifdef CONFIG_STRICT_DEVMEM
  64static inline int page_is_allowed(unsigned long pfn)
  65{
  66        return devmem_is_allowed(pfn);
  67}
  68static inline int range_is_allowed(unsigned long pfn, unsigned long size)
  69{
  70        u64 from = ((u64)pfn) << PAGE_SHIFT;
  71        u64 to = from + size;
  72        u64 cursor = from;
  73
  74        while (cursor < to) {
  75                if (!devmem_is_allowed(pfn))
  76                        return 0;
  77                cursor += PAGE_SIZE;
  78                pfn++;
  79        }
  80        return 1;
  81}
  82#else
  83static inline int page_is_allowed(unsigned long pfn)
  84{
  85        return 1;
  86}
  87static inline int range_is_allowed(unsigned long pfn, unsigned long size)
  88{
  89        return 1;
  90}
  91#endif
  92
  93#ifndef unxlate_dev_mem_ptr
  94#define unxlate_dev_mem_ptr unxlate_dev_mem_ptr
  95void __weak unxlate_dev_mem_ptr(phys_addr_t phys, void *addr)
  96{
  97}
  98#endif
  99
 100/*
 101 * This funcion reads the *physical* memory. The f_pos points directly to the
 102 * memory location.
 103 */
 104static ssize_t read_mem(struct file *file, char __user *buf,
 105                        size_t count, loff_t *ppos)
 106{
 107        phys_addr_t p = *ppos;
 108        ssize_t read, sz;
 109        void *ptr;
 110        char *bounce;
 111        int err;
 112
 113        if (p != *ppos)
 114                return 0;
 115
 116        if (!valid_phys_addr_range(p, count))
 117                return -EFAULT;
 118        read = 0;
 119#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 120        /* we don't have page 0 mapped on sparc and m68k.. */
 121        if (p < PAGE_SIZE) {
 122                sz = size_inside_page(p, count);
 123                if (sz > 0) {
 124                        if (clear_user(buf, sz))
 125                                return -EFAULT;
 126                        buf += sz;
 127                        p += sz;
 128                        count -= sz;
 129                        read += sz;
 130                }
 131        }
 132#endif
 133
 134        bounce = kmalloc(PAGE_SIZE, GFP_KERNEL);
 135        if (!bounce)
 136                return -ENOMEM;
 137
 138        while (count > 0) {
 139                unsigned long remaining;
 140                int allowed;
 141
 142                sz = size_inside_page(p, count);
 143
 144                err = -EPERM;
 145                allowed = page_is_allowed(p >> PAGE_SHIFT);
 146                if (!allowed)
 147                        goto failed;
 148
 149                err = -EFAULT;
 150                if (allowed == 2) {
 151                        /* Show zeros for restricted memory. */
 152                        remaining = clear_user(buf, sz);
 153                } else {
 154                        /*
 155                         * On ia64 if a page has been mapped somewhere as
 156                         * uncached, then it must also be accessed uncached
 157                         * by the kernel or data corruption may occur.
 158                         */
 159                        ptr = xlate_dev_mem_ptr(p);
 160                        if (!ptr)
 161                                goto failed;
 162
 163                        err = probe_kernel_read(bounce, ptr, sz);
 164                        unxlate_dev_mem_ptr(p, ptr);
 165                        if (err)
 166                                goto failed;
 167
 168                        remaining = copy_to_user(buf, bounce, sz);
 169                }
 170
 171                if (remaining)
 172                        goto failed;
 173
 174                buf += sz;
 175                p += sz;
 176                count -= sz;
 177                read += sz;
 178        }
 179        kfree(bounce);
 180
 181        *ppos += read;
 182        return read;
 183
 184failed:
 185        kfree(bounce);
 186        return err;
 187}
 188
 189static ssize_t write_mem(struct file *file, const char __user *buf,
 190                         size_t count, loff_t *ppos)
 191{
 192        phys_addr_t p = *ppos;
 193        ssize_t written, sz;
 194        unsigned long copied;
 195        void *ptr;
 196
 197        if (p != *ppos)
 198                return -EFBIG;
 199
 200        if (!valid_phys_addr_range(p, count))
 201                return -EFAULT;
 202
 203        written = 0;
 204
 205#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 206        /* we don't have page 0 mapped on sparc and m68k.. */
 207        if (p < PAGE_SIZE) {
 208                sz = size_inside_page(p, count);
 209                /* Hmm. Do something? */
 210                buf += sz;
 211                p += sz;
 212                count -= sz;
 213                written += sz;
 214        }
 215#endif
 216
 217        while (count > 0) {
 218                int allowed;
 219
 220                sz = size_inside_page(p, count);
 221
 222                allowed = page_is_allowed(p >> PAGE_SHIFT);
 223                if (!allowed)
 224                        return -EPERM;
 225
 226                /* Skip actual writing when a page is marked as restricted. */
 227                if (allowed == 1) {
 228                        /*
 229                         * On ia64 if a page has been mapped somewhere as
 230                         * uncached, then it must also be accessed uncached
 231                         * by the kernel or data corruption may occur.
 232                         */
 233                        ptr = xlate_dev_mem_ptr(p);
 234                        if (!ptr) {
 235                                if (written)
 236                                        break;
 237                                return -EFAULT;
 238                        }
 239
 240                        copied = copy_from_user(ptr, buf, sz);
 241                        unxlate_dev_mem_ptr(p, ptr);
 242                        if (copied) {
 243                                written += sz - copied;
 244                                if (written)
 245                                        break;
 246                                return -EFAULT;
 247                        }
 248                }
 249
 250                buf += sz;
 251                p += sz;
 252                count -= sz;
 253                written += sz;
 254        }
 255
 256        *ppos += written;
 257        return written;
 258}
 259
 260int __weak phys_mem_access_prot_allowed(struct file *file,
 261        unsigned long pfn, unsigned long size, pgprot_t *vma_prot)
 262{
 263        return 1;
 264}
 265
 266#ifndef __HAVE_PHYS_MEM_ACCESS_PROT
 267
 268/*
 269 * Architectures vary in how they handle caching for addresses
 270 * outside of main memory.
 271 *
 272 */
 273#ifdef pgprot_noncached
 274static int uncached_access(struct file *file, phys_addr_t addr)
 275{
 276#if defined(CONFIG_IA64)
 277        /*
 278         * On ia64, we ignore O_DSYNC because we cannot tolerate memory
 279         * attribute aliases.
 280         */
 281        return !(efi_mem_attributes(addr) & EFI_MEMORY_WB);
 282#elif defined(CONFIG_MIPS)
 283        {
 284                extern int __uncached_access(struct file *file,
 285                                             unsigned long addr);
 286
 287                return __uncached_access(file, addr);
 288        }
 289#else
 290        /*
 291         * Accessing memory above the top the kernel knows about or through a
 292         * file pointer
 293         * that was marked O_DSYNC will be done non-cached.
 294         */
 295        if (file->f_flags & O_DSYNC)
 296                return 1;
 297        return addr >= __pa(high_memory);
 298#endif
 299}
 300#endif
 301
 302static pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 303                                     unsigned long size, pgprot_t vma_prot)
 304{
 305#ifdef pgprot_noncached
 306        phys_addr_t offset = pfn << PAGE_SHIFT;
 307
 308        if (uncached_access(file, offset))
 309                return pgprot_noncached(vma_prot);
 310#endif
 311        return vma_prot;
 312}
 313#endif
 314
 315#ifndef CONFIG_MMU
 316static unsigned long get_unmapped_area_mem(struct file *file,
 317                                           unsigned long addr,
 318                                           unsigned long len,
 319                                           unsigned long pgoff,
 320                                           unsigned long flags)
 321{
 322        if (!valid_mmap_phys_addr_range(pgoff, len))
 323                return (unsigned long) -EINVAL;
 324        return pgoff << PAGE_SHIFT;
 325}
 326
 327/* permit direct mmap, for read, write or exec */
 328static unsigned memory_mmap_capabilities(struct file *file)
 329{
 330        return NOMMU_MAP_DIRECT |
 331                NOMMU_MAP_READ | NOMMU_MAP_WRITE | NOMMU_MAP_EXEC;
 332}
 333
 334static unsigned zero_mmap_capabilities(struct file *file)
 335{
 336        return NOMMU_MAP_COPY;
 337}
 338
 339/* can't do an in-place private mapping if there's no MMU */
 340static inline int private_mapping_ok(struct vm_area_struct *vma)
 341{
 342        return vma->vm_flags & VM_MAYSHARE;
 343}
 344#else
 345
 346static inline int private_mapping_ok(struct vm_area_struct *vma)
 347{
 348        return 1;
 349}
 350#endif
 351
 352static const struct vm_operations_struct mmap_mem_ops = {
 353#ifdef CONFIG_HAVE_IOREMAP_PROT
 354        .access = generic_access_phys
 355#endif
 356};
 357
 358static int mmap_mem(struct file *file, struct vm_area_struct *vma)
 359{
 360        size_t size = vma->vm_end - vma->vm_start;
 361        phys_addr_t offset = (phys_addr_t)vma->vm_pgoff << PAGE_SHIFT;
 362
 363        /* Does it even fit in phys_addr_t? */
 364        if (offset >> PAGE_SHIFT != vma->vm_pgoff)
 365                return -EINVAL;
 366
 367        /* It's illegal to wrap around the end of the physical address space. */
 368        if (offset + (phys_addr_t)size - 1 < offset)
 369                return -EINVAL;
 370
 371        if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))
 372                return -EINVAL;
 373
 374        if (!private_mapping_ok(vma))
 375                return -ENOSYS;
 376
 377        if (!range_is_allowed(vma->vm_pgoff, size))
 378                return -EPERM;
 379
 380        if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size,
 381                                                &vma->vm_page_prot))
 382                return -EINVAL;
 383
 384        vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,
 385                                                 size,
 386                                                 vma->vm_page_prot);
 387
 388        vma->vm_ops = &mmap_mem_ops;
 389
 390        /* Remap-pfn-range will mark the range VM_IO */
 391        if (remap_pfn_range(vma,
 392                            vma->vm_start,
 393                            vma->vm_pgoff,
 394                            size,
 395                            vma->vm_page_prot)) {
 396                return -EAGAIN;
 397        }
 398        return 0;
 399}
 400
 401static int mmap_kmem(struct file *file, struct vm_area_struct *vma)
 402{
 403        unsigned long pfn;
 404
 405        /* Turn a kernel-virtual address into a physical page frame */
 406        pfn = __pa((u64)vma->vm_pgoff << PAGE_SHIFT) >> PAGE_SHIFT;
 407
 408        /*
 409         * RED-PEN: on some architectures there is more mapped memory than
 410         * available in mem_map which pfn_valid checks for. Perhaps should add a
 411         * new macro here.
 412         *
 413         * RED-PEN: vmalloc is not supported right now.
 414         */
 415        if (!pfn_valid(pfn))
 416                return -EIO;
 417
 418        vma->vm_pgoff = pfn;
 419        return mmap_mem(file, vma);
 420}
 421
 422/*
 423 * This function reads the *virtual* memory as seen by the kernel.
 424 */
 425static ssize_t read_kmem(struct file *file, char __user *buf,
 426                         size_t count, loff_t *ppos)
 427{
 428        unsigned long p = *ppos;
 429        ssize_t low_count, read, sz;
 430        char *kbuf; /* k-addr because vread() takes vmlist_lock rwlock */
 431        int err = 0;
 432
 433        read = 0;
 434        if (p < (unsigned long) high_memory) {
 435                low_count = count;
 436                if (count > (unsigned long)high_memory - p)
 437                        low_count = (unsigned long)high_memory - p;
 438
 439#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 440                /* we don't have page 0 mapped on sparc and m68k.. */
 441                if (p < PAGE_SIZE && low_count > 0) {
 442                        sz = size_inside_page(p, low_count);
 443                        if (clear_user(buf, sz))
 444                                return -EFAULT;
 445                        buf += sz;
 446                        p += sz;
 447                        read += sz;
 448                        low_count -= sz;
 449                        count -= sz;
 450                }
 451#endif
 452                while (low_count > 0) {
 453                        sz = size_inside_page(p, low_count);
 454
 455                        /*
 456                         * On ia64 if a page has been mapped somewhere as
 457                         * uncached, then it must also be accessed uncached
 458                         * by the kernel or data corruption may occur
 459                         */
 460                        kbuf = xlate_dev_kmem_ptr((void *)p);
 461                        if (!virt_addr_valid(kbuf))
 462                                return -ENXIO;
 463
 464                        if (copy_to_user(buf, kbuf, sz))
 465                                return -EFAULT;
 466                        buf += sz;
 467                        p += sz;
 468                        read += sz;
 469                        low_count -= sz;
 470                        count -= sz;
 471                }
 472        }
 473
 474        if (count > 0) {
 475                kbuf = (char *)__get_free_page(GFP_KERNEL);
 476                if (!kbuf)
 477                        return -ENOMEM;
 478                while (count > 0) {
 479                        sz = size_inside_page(p, count);
 480                        if (!is_vmalloc_or_module_addr((void *)p)) {
 481                                err = -ENXIO;
 482                                break;
 483                        }
 484                        sz = vread(kbuf, (char *)p, sz);
 485                        if (!sz)
 486                                break;
 487                        if (copy_to_user(buf, kbuf, sz)) {
 488                                err = -EFAULT;
 489                                break;
 490                        }
 491                        count -= sz;
 492                        buf += sz;
 493                        read += sz;
 494                        p += sz;
 495                }
 496                free_page((unsigned long)kbuf);
 497        }
 498        *ppos = p;
 499        return read ? read : err;
 500}
 501
 502
 503static ssize_t do_write_kmem(unsigned long p, const char __user *buf,
 504                                size_t count, loff_t *ppos)
 505{
 506        ssize_t written, sz;
 507        unsigned long copied;
 508
 509        written = 0;
 510#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 511        /* we don't have page 0 mapped on sparc and m68k.. */
 512        if (p < PAGE_SIZE) {
 513                sz = size_inside_page(p, count);
 514                /* Hmm. Do something? */
 515                buf += sz;
 516                p += sz;
 517                count -= sz;
 518                written += sz;
 519        }
 520#endif
 521
 522        while (count > 0) {
 523                void *ptr;
 524
 525                sz = size_inside_page(p, count);
 526
 527                /*
 528                 * On ia64 if a page has been mapped somewhere as uncached, then
 529                 * it must also be accessed uncached by the kernel or data
 530                 * corruption may occur.
 531                 */
 532                ptr = xlate_dev_kmem_ptr((void *)p);
 533                if (!virt_addr_valid(ptr))
 534                        return -ENXIO;
 535
 536                copied = copy_from_user(ptr, buf, sz);
 537                if (copied) {
 538                        written += sz - copied;
 539                        if (written)
 540                                break;
 541                        return -EFAULT;
 542                }
 543                buf += sz;
 544                p += sz;
 545                count -= sz;
 546                written += sz;
 547        }
 548
 549        *ppos += written;
 550        return written;
 551}
 552
 553/*
 554 * This function writes to the *virtual* memory as seen by the kernel.
 555 */
 556static ssize_t write_kmem(struct file *file, const char __user *buf,
 557                          size_t count, loff_t *ppos)
 558{
 559        unsigned long p = *ppos;
 560        ssize_t wrote = 0;
 561        ssize_t virtr = 0;
 562        char *kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
 563        int err = 0;
 564
 565        if (p < (unsigned long) high_memory) {
 566                unsigned long to_write = min_t(unsigned long, count,
 567                                               (unsigned long)high_memory - p);
 568                wrote = do_write_kmem(p, buf, to_write, ppos);
 569                if (wrote != to_write)
 570                        return wrote;
 571                p += wrote;
 572                buf += wrote;
 573                count -= wrote;
 574        }
 575
 576        if (count > 0) {
 577                kbuf = (char *)__get_free_page(GFP_KERNEL);
 578                if (!kbuf)
 579                        return wrote ? wrote : -ENOMEM;
 580                while (count > 0) {
 581                        unsigned long sz = size_inside_page(p, count);
 582                        unsigned long n;
 583
 584                        if (!is_vmalloc_or_module_addr((void *)p)) {
 585                                err = -ENXIO;
 586                                break;
 587                        }
 588                        n = copy_from_user(kbuf, buf, sz);
 589                        if (n) {
 590                                err = -EFAULT;
 591                                break;
 592                        }
 593                        vwrite(kbuf, (char *)p, sz);
 594                        count -= sz;
 595                        buf += sz;
 596                        virtr += sz;
 597                        p += sz;
 598                }
 599                free_page((unsigned long)kbuf);
 600        }
 601
 602        *ppos = p;
 603        return virtr + wrote ? : err;
 604}
 605
 606static ssize_t read_port(struct file *file, char __user *buf,
 607                         size_t count, loff_t *ppos)
 608{
 609        unsigned long i = *ppos;
 610        char __user *tmp = buf;
 611
 612        if (!access_ok(VERIFY_WRITE, buf, count))
 613                return -EFAULT;
 614        while (count-- > 0 && i < 65536) {
 615                if (__put_user(inb(i), tmp) < 0)
 616                        return -EFAULT;
 617                i++;
 618                tmp++;
 619        }
 620        *ppos = i;
 621        return tmp-buf;
 622}
 623
 624static ssize_t write_port(struct file *file, const char __user *buf,
 625                          size_t count, loff_t *ppos)
 626{
 627        unsigned long i = *ppos;
 628        const char __user *tmp = buf;
 629
 630        if (!access_ok(VERIFY_READ, buf, count))
 631                return -EFAULT;
 632        while (count-- > 0 && i < 65536) {
 633                char c;
 634
 635                if (__get_user(c, tmp)) {
 636                        if (tmp > buf)
 637                                break;
 638                        return -EFAULT;
 639                }
 640                outb(c, i);
 641                i++;
 642                tmp++;
 643        }
 644        *ppos = i;
 645        return tmp-buf;
 646}
 647
 648static ssize_t read_null(struct file *file, char __user *buf,
 649                         size_t count, loff_t *ppos)
 650{
 651        return 0;
 652}
 653
 654static ssize_t write_null(struct file *file, const char __user *buf,
 655                          size_t count, loff_t *ppos)
 656{
 657        return count;
 658}
 659
 660static ssize_t read_iter_null(struct kiocb *iocb, struct iov_iter *to)
 661{
 662        return 0;
 663}
 664
 665static ssize_t write_iter_null(struct kiocb *iocb, struct iov_iter *from)
 666{
 667        size_t count = iov_iter_count(from);
 668        iov_iter_advance(from, count);
 669        return count;
 670}
 671
 672static int pipe_to_null(struct pipe_inode_info *info, struct pipe_buffer *buf,
 673                        struct splice_desc *sd)
 674{
 675        return sd->len;
 676}
 677
 678static ssize_t splice_write_null(struct pipe_inode_info *pipe, struct file *out,
 679                                 loff_t *ppos, size_t len, unsigned int flags)
 680{
 681        return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_null);
 682}
 683
 684static ssize_t read_iter_zero(struct kiocb *iocb, struct iov_iter *iter)
 685{
 686        size_t written = 0;
 687
 688        while (iov_iter_count(iter)) {
 689                size_t chunk = iov_iter_count(iter), n;
 690
 691                if (chunk > PAGE_SIZE)
 692                        chunk = PAGE_SIZE;      /* Just for latency reasons */
 693                n = iov_iter_zero(chunk, iter);
 694                if (!n && iov_iter_count(iter))
 695                        return written ? written : -EFAULT;
 696                written += n;
 697                if (signal_pending(current))
 698                        return written ? written : -ERESTARTSYS;
 699                cond_resched();
 700        }
 701        return written;
 702}
 703
 704static int mmap_zero(struct file *file, struct vm_area_struct *vma)
 705{
 706#ifndef CONFIG_MMU
 707        return -ENOSYS;
 708#endif
 709        if (vma->vm_flags & VM_SHARED)
 710                return shmem_zero_setup(vma);
 711        return 0;
 712}
 713
 714static unsigned long get_unmapped_area_zero(struct file *file,
 715                                unsigned long addr, unsigned long len,
 716                                unsigned long pgoff, unsigned long flags)
 717{
 718#ifdef CONFIG_MMU
 719        if (flags & MAP_SHARED) {
 720                /*
 721                 * mmap_zero() will call shmem_zero_setup() to create a file,
 722                 * so use shmem's get_unmapped_area in case it can be huge;
 723                 * and pass NULL for file as in mmap.c's get_unmapped_area(),
 724                 * so as not to confuse shmem with our handle on "/dev/zero".
 725                 */
 726                return shmem_get_unmapped_area(NULL, addr, len, pgoff, flags);
 727        }
 728
 729        /* Otherwise flags & MAP_PRIVATE: with no shmem object beneath it */
 730        return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
 731#else
 732        return -ENOSYS;
 733#endif
 734}
 735
 736static 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 */
 747static loff_t null_lseek(struct file *file, loff_t offset, int orig)
 748{
 749        return file->f_pos = 0;
 750}
 751
 752/*
 753 * The memory devices use the full 32/64 bits of the offset, and so we cannot
 754 * check against negative addresses: they are ok. The return value is weird,
 755 * though, in that case (0).
 756 *
 757 * also note that seeking relative to the "end of file" isn't supported:
 758 * it has no meaning, so it returns -EINVAL.
 759 */
 760static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
 761{
 762        loff_t ret;
 763
 764        inode_lock(file_inode(file));
 765        switch (orig) {
 766        case SEEK_CUR:
 767                offset += file->f_pos;
 768        case SEEK_SET:
 769                /* to avoid userland mistaking f_pos=-9 as -EBADF=-9 */
 770                if ((unsigned long long)offset >= -MAX_ERRNO) {
 771                        ret = -EOVERFLOW;
 772                        break;
 773                }
 774                file->f_pos = offset;
 775                ret = file->f_pos;
 776                force_successful_syscall_return();
 777                break;
 778        default:
 779                ret = -EINVAL;
 780        }
 781        inode_unlock(file_inode(file));
 782        return ret;
 783}
 784
 785static int open_port(struct inode *inode, struct file *filp)
 786{
 787        return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
 788}
 789
 790#define zero_lseek      null_lseek
 791#define full_lseek      null_lseek
 792#define write_zero      write_null
 793#define write_iter_zero write_iter_null
 794#define open_mem        open_port
 795#define open_kmem       open_mem
 796
 797static const struct file_operations __maybe_unused mem_fops = {
 798        .llseek         = memory_lseek,
 799        .read           = read_mem,
 800        .write          = write_mem,
 801        .mmap           = mmap_mem,
 802        .open           = open_mem,
 803#ifndef CONFIG_MMU
 804        .get_unmapped_area = get_unmapped_area_mem,
 805        .mmap_capabilities = memory_mmap_capabilities,
 806#endif
 807};
 808
 809static const struct file_operations __maybe_unused kmem_fops = {
 810        .llseek         = memory_lseek,
 811        .read           = read_kmem,
 812        .write          = write_kmem,
 813        .mmap           = mmap_kmem,
 814        .open           = open_kmem,
 815#ifndef CONFIG_MMU
 816        .get_unmapped_area = get_unmapped_area_mem,
 817        .mmap_capabilities = memory_mmap_capabilities,
 818#endif
 819};
 820
 821static const struct file_operations null_fops = {
 822        .llseek         = null_lseek,
 823        .read           = read_null,
 824        .write          = write_null,
 825        .read_iter      = read_iter_null,
 826        .write_iter     = write_iter_null,
 827        .splice_write   = splice_write_null,
 828};
 829
 830static const struct file_operations __maybe_unused port_fops = {
 831        .llseek         = memory_lseek,
 832        .read           = read_port,
 833        .write          = write_port,
 834        .open           = open_port,
 835};
 836
 837static const struct file_operations zero_fops = {
 838        .llseek         = zero_lseek,
 839        .write          = write_zero,
 840        .read_iter      = read_iter_zero,
 841        .write_iter     = write_iter_zero,
 842        .mmap           = mmap_zero,
 843        .get_unmapped_area = get_unmapped_area_zero,
 844#ifndef CONFIG_MMU
 845        .mmap_capabilities = zero_mmap_capabilities,
 846#endif
 847};
 848
 849static const struct file_operations full_fops = {
 850        .llseek         = full_lseek,
 851        .read_iter      = read_iter_zero,
 852        .write          = write_full,
 853};
 854
 855static const struct memdev {
 856        const char *name;
 857        umode_t mode;
 858        const struct file_operations *fops;
 859        fmode_t fmode;
 860} devlist[] = {
 861#ifdef CONFIG_DEVMEM
 862         [1] = { "mem", 0, &mem_fops, FMODE_UNSIGNED_OFFSET },
 863#endif
 864#ifdef CONFIG_DEVKMEM
 865         [2] = { "kmem", 0, &kmem_fops, FMODE_UNSIGNED_OFFSET },
 866#endif
 867         [3] = { "null", 0666, &null_fops, 0 },
 868#ifdef CONFIG_DEVPORT
 869         [4] = { "port", 0, &port_fops, 0 },
 870#endif
 871         [5] = { "zero", 0666, &zero_fops, 0 },
 872         [7] = { "full", 0666, &full_fops, 0 },
 873         [8] = { "random", 0666, &random_fops, 0 },
 874         [9] = { "urandom", 0666, &urandom_fops, 0 },
 875#ifdef CONFIG_PRINTK
 876        [11] = { "kmsg", 0644, &kmsg_fops, 0 },
 877#endif
 878};
 879
 880static int memory_open(struct inode *inode, struct file *filp)
 881{
 882        int minor;
 883        const struct memdev *dev;
 884
 885        minor = iminor(inode);
 886        if (minor >= ARRAY_SIZE(devlist))
 887                return -ENXIO;
 888
 889        dev = &devlist[minor];
 890        if (!dev->fops)
 891                return -ENXIO;
 892
 893        filp->f_op = dev->fops;
 894        filp->f_mode |= dev->fmode;
 895
 896        if (dev->fops->open)
 897                return dev->fops->open(inode, filp);
 898
 899        return 0;
 900}
 901
 902static const struct file_operations memory_fops = {
 903        .open = memory_open,
 904        .llseek = noop_llseek,
 905};
 906
 907static char *mem_devnode(struct device *dev, umode_t *mode)
 908{
 909        if (mode && devlist[MINOR(dev->devt)].mode)
 910                *mode = devlist[MINOR(dev->devt)].mode;
 911        return NULL;
 912}
 913
 914static struct class *mem_class;
 915
 916static int __init chr_dev_init(void)
 917{
 918        int minor;
 919
 920        if (register_chrdev(MEM_MAJOR, "mem", &memory_fops))
 921                printk("unable to get major %d for memory devs\n", MEM_MAJOR);
 922
 923        mem_class = class_create(THIS_MODULE, "mem");
 924        if (IS_ERR(mem_class))
 925                return PTR_ERR(mem_class);
 926
 927        mem_class->devnode = mem_devnode;
 928        for (minor = 1; minor < ARRAY_SIZE(devlist); minor++) {
 929                if (!devlist[minor].name)
 930                        continue;
 931
 932                /*
 933                 * Create /dev/port?
 934                 */
 935                if ((minor == DEVPORT_MINOR) && !arch_has_dev_port())
 936                        continue;
 937
 938                device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor),
 939                              NULL, devlist[minor].name);
 940        }
 941
 942        return tty_init();
 943}
 944
 945fs_initcall(chr_dev_init);
 946
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