linux/fs/read_write.c
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   1/*
   2 *  linux/fs/read_write.c
   3 *
   4 *  Copyright (C) 1991, 1992  Linus Torvalds
   5 */
   6
   7#include <linux/slab.h> 
   8#include <linux/stat.h>
   9#include <linux/fcntl.h>
  10#include <linux/file.h>
  11#include <linux/uio.h>
  12#include <linux/smp_lock.h>
  13#include <linux/fsnotify.h>
  14#include <linux/security.h>
  15#include <linux/module.h>
  16#include <linux/syscalls.h>
  17#include <linux/pagemap.h>
  18
  19#include <asm/uaccess.h>
  20#include <asm/unistd.h>
  21
  22const struct file_operations generic_ro_fops = {
  23        .llseek         = generic_file_llseek,
  24        .read           = generic_file_read,
  25        .mmap           = generic_file_readonly_mmap,
  26        .sendfile       = generic_file_sendfile,
  27};
  28
  29EXPORT_SYMBOL(generic_ro_fops);
  30
  31loff_t generic_file_llseek(struct file *file, loff_t offset, int origin)
  32{
  33        long long retval;
  34        struct inode *inode = file->f_mapping->host;
  35
  36        mutex_lock(&inode->i_mutex);
  37        switch (origin) {
  38                case 2:
  39                        offset += inode->i_size;
  40                        break;
  41                case 1:
  42                        offset += file->f_pos;
  43        }
  44        retval = -EINVAL;
  45        if (offset>=0 && offset<=inode->i_sb->s_maxbytes) {
  46                if (offset != file->f_pos) {
  47                        file->f_pos = offset;
  48                        file->f_version = 0;
  49                }
  50                retval = offset;
  51        }
  52        mutex_unlock(&inode->i_mutex);
  53        return retval;
  54}
  55
  56EXPORT_SYMBOL(generic_file_llseek);
  57
  58loff_t remote_llseek(struct file *file, loff_t offset, int origin)
  59{
  60        long long retval;
  61
  62        lock_kernel();
  63        switch (origin) {
  64                case 2:
  65                        offset += i_size_read(file->f_dentry->d_inode);
  66                        break;
  67                case 1:
  68                        offset += file->f_pos;
  69        }
  70        retval = -EINVAL;
  71        if (offset>=0 && offset<=file->f_dentry->d_inode->i_sb->s_maxbytes) {
  72                if (offset != file->f_pos) {
  73                        file->f_pos = offset;
  74                        file->f_version = 0;
  75                }
  76                retval = offset;
  77        }
  78        unlock_kernel();
  79        return retval;
  80}
  81EXPORT_SYMBOL(remote_llseek);
  82
  83loff_t no_llseek(struct file *file, loff_t offset, int origin)
  84{
  85        return -ESPIPE;
  86}
  87EXPORT_SYMBOL(no_llseek);
  88
  89loff_t default_llseek(struct file *file, loff_t offset, int origin)
  90{
  91        long long retval;
  92
  93        lock_kernel();
  94        switch (origin) {
  95                case 2:
  96                        offset += i_size_read(file->f_dentry->d_inode);
  97                        break;
  98                case 1:
  99                        offset += file->f_pos;
 100        }
 101        retval = -EINVAL;
 102        if (offset >= 0) {
 103                if (offset != file->f_pos) {
 104                        file->f_pos = offset;
 105                        file->f_version = 0;
 106                }
 107                retval = offset;
 108        }
 109        unlock_kernel();
 110        return retval;
 111}
 112EXPORT_SYMBOL(default_llseek);
 113
 114loff_t vfs_llseek(struct file *file, loff_t offset, int origin)
 115{
 116        loff_t (*fn)(struct file *, loff_t, int);
 117
 118        fn = no_llseek;
 119        if (file->f_mode & FMODE_LSEEK) {
 120                fn = default_llseek;
 121                if (file->f_op && file->f_op->llseek)
 122                        fn = file->f_op->llseek;
 123        }
 124        return fn(file, offset, origin);
 125}
 126EXPORT_SYMBOL(vfs_llseek);
 127
 128asmlinkage off_t sys_lseek(unsigned int fd, off_t offset, unsigned int origin)
 129{
 130        off_t retval;
 131        struct file * file;
 132        int fput_needed;
 133
 134        retval = -EBADF;
 135        file = fget_light(fd, &fput_needed);
 136        if (!file)
 137                goto bad;
 138
 139        retval = -EINVAL;
 140        if (origin <= 2) {
 141                loff_t res = vfs_llseek(file, offset, origin);
 142                retval = res;
 143                if (res != (loff_t)retval)
 144                        retval = -EOVERFLOW;    /* LFS: should only happen on 32 bit platforms */
 145        }
 146        fput_light(file, fput_needed);
 147bad:
 148        return retval;
 149}
 150
 151#ifdef __ARCH_WANT_SYS_LLSEEK
 152asmlinkage long sys_llseek(unsigned int fd, unsigned long offset_high,
 153                           unsigned long offset_low, loff_t __user * result,
 154                           unsigned int origin)
 155{
 156        int retval;
 157        struct file * file;
 158        loff_t offset;
 159        int fput_needed;
 160
 161        retval = -EBADF;
 162        file = fget_light(fd, &fput_needed);
 163        if (!file)
 164                goto bad;
 165
 166        retval = -EINVAL;
 167        if (origin > 2)
 168                goto out_putf;
 169
 170        offset = vfs_llseek(file, ((loff_t) offset_high << 32) | offset_low,
 171                        origin);
 172
 173        retval = (int)offset;
 174        if (offset >= 0) {
 175                retval = -EFAULT;
 176                if (!copy_to_user(result, &offset, sizeof(offset)))
 177                        retval = 0;
 178        }
 179out_putf:
 180        fput_light(file, fput_needed);
 181bad:
 182        return retval;
 183}
 184#endif
 185
 186/*
 187 * rw_verify_area doesn't like huge counts. We limit
 188 * them to something that fits in "int" so that others
 189 * won't have to do range checks all the time.
 190 */
 191#define MAX_RW_COUNT (INT_MAX & PAGE_CACHE_MASK)
 192
 193int rw_verify_area(int read_write, struct file *file, loff_t *ppos, size_t count)
 194{
 195        struct inode *inode;
 196        loff_t pos;
 197
 198        if (unlikely((ssize_t) count < 0))
 199                goto Einval;
 200        pos = *ppos;
 201        if (unlikely((pos < 0) || (loff_t) (pos + count) < 0))
 202                goto Einval;
 203
 204        inode = file->f_dentry->d_inode;
 205        if (unlikely(inode->i_flock && MANDATORY_LOCK(inode))) {
 206                int retval = locks_mandatory_area(
 207                        read_write == READ ? FLOCK_VERIFY_READ : FLOCK_VERIFY_WRITE,
 208                        inode, file, pos, count);
 209                if (retval < 0)
 210                        return retval;
 211        }
 212        return count > MAX_RW_COUNT ? MAX_RW_COUNT : count;
 213
 214Einval:
 215        return -EINVAL;
 216}
 217
 218static void wait_on_retry_sync_kiocb(struct kiocb *iocb)
 219{
 220        set_current_state(TASK_UNINTERRUPTIBLE);
 221        if (!kiocbIsKicked(iocb))
 222                schedule();
 223        else
 224                kiocbClearKicked(iocb);
 225        __set_current_state(TASK_RUNNING);
 226}
 227
 228ssize_t do_sync_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
 229{
 230        struct kiocb kiocb;
 231        ssize_t ret;
 232
 233        init_sync_kiocb(&kiocb, filp);
 234        kiocb.ki_pos = *ppos;
 235        while (-EIOCBRETRY ==
 236                (ret = filp->f_op->aio_read(&kiocb, buf, len, kiocb.ki_pos)))
 237                wait_on_retry_sync_kiocb(&kiocb);
 238
 239        if (-EIOCBQUEUED == ret)
 240                ret = wait_on_sync_kiocb(&kiocb);
 241        *ppos = kiocb.ki_pos;
 242        return ret;
 243}
 244
 245EXPORT_SYMBOL(do_sync_read);
 246
 247ssize_t vfs_read(struct file *file, char __user *buf, size_t count, loff_t *pos)
 248{
 249        ssize_t ret;
 250
 251        if (!(file->f_mode & FMODE_READ))
 252                return -EBADF;
 253        if (!file->f_op || (!file->f_op->read && !file->f_op->aio_read))
 254                return -EINVAL;
 255        if (unlikely(!access_ok(VERIFY_WRITE, buf, count)))
 256                return -EFAULT;
 257
 258        ret = rw_verify_area(READ, file, pos, count);
 259        if (ret >= 0) {
 260                count = ret;
 261                ret = security_file_permission (file, MAY_READ);
 262                if (!ret) {
 263                        if (file->f_op->read)
 264                                ret = file->f_op->read(file, buf, count, pos);
 265                        else
 266                                ret = do_sync_read(file, buf, count, pos);
 267                        if (ret > 0) {
 268                                fsnotify_access(file->f_dentry);
 269                                current->rchar += ret;
 270                        }
 271                        current->syscr++;
 272                }
 273        }
 274
 275        return ret;
 276}
 277
 278EXPORT_SYMBOL(vfs_read);
 279
 280ssize_t do_sync_write(struct file *filp, const char __user *buf, size_t len, loff_t *ppos)
 281{
 282        struct kiocb kiocb;
 283        ssize_t ret;
 284
 285        init_sync_kiocb(&kiocb, filp);
 286        kiocb.ki_pos = *ppos;
 287        while (-EIOCBRETRY ==
 288               (ret = filp->f_op->aio_write(&kiocb, buf, len, kiocb.ki_pos)))
 289                wait_on_retry_sync_kiocb(&kiocb);
 290
 291        if (-EIOCBQUEUED == ret)
 292                ret = wait_on_sync_kiocb(&kiocb);
 293        *ppos = kiocb.ki_pos;
 294        return ret;
 295}
 296
 297EXPORT_SYMBOL(do_sync_write);
 298
 299ssize_t vfs_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
 300{
 301        ssize_t ret;
 302
 303        if (!(file->f_mode & FMODE_WRITE))
 304                return -EBADF;
 305        if (!file->f_op || (!file->f_op->write && !file->f_op->aio_write))
 306                return -EINVAL;
 307        if (unlikely(!access_ok(VERIFY_READ, buf, count)))
 308                return -EFAULT;
 309
 310        ret = rw_verify_area(WRITE, file, pos, count);
 311        if (ret >= 0) {
 312                count = ret;
 313                ret = security_file_permission (file, MAY_WRITE);
 314                if (!ret) {
 315                        if (file->f_op->write)
 316                                ret = file->f_op->write(file, buf, count, pos);
 317                        else
 318                                ret = do_sync_write(file, buf, count, pos);
 319                        if (ret > 0) {
 320                                fsnotify_modify(file->f_dentry);
 321                                current->wchar += ret;
 322                        }
 323                        current->syscw++;
 324                }
 325        }
 326
 327        return ret;
 328}
 329
 330EXPORT_SYMBOL(vfs_write);
 331
 332static inline loff_t file_pos_read(struct file *file)
 333{
 334        return file->f_pos;
 335}
 336
 337static inline void file_pos_write(struct file *file, loff_t pos)
 338{
 339        file->f_pos = pos;
 340}
 341
 342asmlinkage ssize_t sys_read(unsigned int fd, char __user * buf, size_t count)
 343{
 344        struct file *file;
 345        ssize_t ret = -EBADF;
 346        int fput_needed;
 347
 348        file = fget_light(fd, &fput_needed);
 349        if (file) {
 350                loff_t pos = file_pos_read(file);
 351                ret = vfs_read(file, buf, count, &pos);
 352                file_pos_write(file, pos);
 353                fput_light(file, fput_needed);
 354        }
 355
 356        return ret;
 357}
 358EXPORT_SYMBOL_GPL(sys_read);
 359
 360asmlinkage ssize_t sys_write(unsigned int fd, const char __user * buf, size_t count)
 361{
 362        struct file *file;
 363        ssize_t ret = -EBADF;
 364        int fput_needed;
 365
 366        file = fget_light(fd, &fput_needed);
 367        if (file) {
 368                loff_t pos = file_pos_read(file);
 369                ret = vfs_write(file, buf, count, &pos);
 370                file_pos_write(file, pos);
 371                fput_light(file, fput_needed);
 372        }
 373
 374        return ret;
 375}
 376
 377asmlinkage ssize_t sys_pread64(unsigned int fd, char __user *buf,
 378                             size_t count, loff_t pos)
 379{
 380        struct file *file;
 381        ssize_t ret = -EBADF;
 382        int fput_needed;
 383
 384        if (pos < 0)
 385                return -EINVAL;
 386
 387        file = fget_light(fd, &fput_needed);
 388        if (file) {
 389                ret = -ESPIPE;
 390                if (file->f_mode & FMODE_PREAD)
 391                        ret = vfs_read(file, buf, count, &pos);
 392                fput_light(file, fput_needed);
 393        }
 394
 395        return ret;
 396}
 397
 398asmlinkage ssize_t sys_pwrite64(unsigned int fd, const char __user *buf,
 399                              size_t count, loff_t pos)
 400{
 401        struct file *file;
 402        ssize_t ret = -EBADF;
 403        int fput_needed;
 404
 405        if (pos < 0)
 406                return -EINVAL;
 407
 408        file = fget_light(fd, &fput_needed);
 409        if (file) {
 410                ret = -ESPIPE;
 411                if (file->f_mode & FMODE_PWRITE)  
 412                        ret = vfs_write(file, buf, count, &pos);
 413                fput_light(file, fput_needed);
 414        }
 415
 416        return ret;
 417}
 418
 419/*
 420 * Reduce an iovec's length in-place.  Return the resulting number of segments
 421 */
 422unsigned long iov_shorten(struct iovec *iov, unsigned long nr_segs, size_t to)
 423{
 424        unsigned long seg = 0;
 425        size_t len = 0;
 426
 427        while (seg < nr_segs) {
 428                seg++;
 429                if (len + iov->iov_len >= to) {
 430                        iov->iov_len = to - len;
 431                        break;
 432                }
 433                len += iov->iov_len;
 434                iov++;
 435        }
 436        return seg;
 437}
 438
 439EXPORT_UNUSED_SYMBOL(iov_shorten);  /*  June 2006  */
 440
 441/* A write operation does a read from user space and vice versa */
 442#define vrfy_dir(type) ((type) == READ ? VERIFY_WRITE : VERIFY_READ)
 443
 444static ssize_t do_readv_writev(int type, struct file *file,
 445                               const struct iovec __user * uvector,
 446                               unsigned long nr_segs, loff_t *pos)
 447{
 448        typedef ssize_t (*io_fn_t)(struct file *, char __user *, size_t, loff_t *);
 449        typedef ssize_t (*iov_fn_t)(struct file *, const struct iovec *, unsigned long, loff_t *);
 450
 451        size_t tot_len;
 452        struct iovec iovstack[UIO_FASTIOV];
 453        struct iovec *iov=iovstack, *vector;
 454        ssize_t ret;
 455        int seg;
 456        io_fn_t fn;
 457        iov_fn_t fnv;
 458
 459        /*
 460         * SuS says "The readv() function *may* fail if the iovcnt argument
 461         * was less than or equal to 0, or greater than {IOV_MAX}.  Linux has
 462         * traditionally returned zero for zero segments, so...
 463         */
 464        ret = 0;
 465        if (nr_segs == 0)
 466                goto out;
 467
 468        /*
 469         * First get the "struct iovec" from user memory and
 470         * verify all the pointers
 471         */
 472        ret = -EINVAL;
 473        if (nr_segs > UIO_MAXIOV)
 474                goto out;
 475        if (!file->f_op)
 476                goto out;
 477        if (nr_segs > UIO_FASTIOV) {
 478                ret = -ENOMEM;
 479                iov = kmalloc(nr_segs*sizeof(struct iovec), GFP_KERNEL);
 480                if (!iov)
 481                        goto out;
 482        }
 483        ret = -EFAULT;
 484        if (copy_from_user(iov, uvector, nr_segs*sizeof(*uvector)))
 485                goto out;
 486
 487        /*
 488         * Single unix specification:
 489         * We should -EINVAL if an element length is not >= 0 and fitting an
 490         * ssize_t.  The total length is fitting an ssize_t
 491         *
 492         * Be careful here because iov_len is a size_t not an ssize_t
 493         */
 494        tot_len = 0;
 495        ret = -EINVAL;
 496        for (seg = 0; seg < nr_segs; seg++) {
 497                void __user *buf = iov[seg].iov_base;
 498                ssize_t len = (ssize_t)iov[seg].iov_len;
 499
 500                if (len < 0)    /* size_t not fitting an ssize_t .. */
 501                        goto out;
 502                if (unlikely(!access_ok(vrfy_dir(type), buf, len)))
 503                        goto Efault;
 504                tot_len += len;
 505                if ((ssize_t)tot_len < 0) /* maths overflow on the ssize_t */
 506                        goto out;
 507        }
 508        if (tot_len == 0) {
 509                ret = 0;
 510                goto out;
 511        }
 512
 513        ret = rw_verify_area(type, file, pos, tot_len);
 514        if (ret < 0)
 515                goto out;
 516        ret = security_file_permission(file, type == READ ? MAY_READ : MAY_WRITE);
 517        if (ret)
 518                goto out;
 519
 520        fnv = NULL;
 521        if (type == READ) {
 522                fn = file->f_op->read;
 523                fnv = file->f_op->readv;
 524        } else {
 525                fn = (io_fn_t)file->f_op->write;
 526                fnv = file->f_op->writev;
 527        }
 528        if (fnv) {
 529                ret = fnv(file, iov, nr_segs, pos);
 530                goto out;
 531        }
 532
 533        /* Do it by hand, with file-ops */
 534        ret = 0;
 535        vector = iov;
 536        while (nr_segs > 0) {
 537                void __user * base;
 538                size_t len;
 539                ssize_t nr;
 540
 541                base = vector->iov_base;
 542                len = vector->iov_len;
 543                vector++;
 544                nr_segs--;
 545
 546                nr = fn(file, base, len, pos);
 547
 548                if (nr < 0) {
 549                        if (!ret) ret = nr;
 550                        break;
 551                }
 552                ret += nr;
 553                if (nr != len)
 554                        break;
 555        }
 556out:
 557        if (iov != iovstack)
 558                kfree(iov);
 559        if ((ret + (type == READ)) > 0) {
 560                if (type == READ)
 561                        fsnotify_access(file->f_dentry);
 562                else
 563                        fsnotify_modify(file->f_dentry);
 564        }
 565        return ret;
 566Efault:
 567        ret = -EFAULT;
 568        goto out;
 569}
 570
 571ssize_t vfs_readv(struct file *file, const struct iovec __user *vec,
 572                  unsigned long vlen, loff_t *pos)
 573{
 574        if (!(file->f_mode & FMODE_READ))
 575                return -EBADF;
 576        if (!file->f_op || (!file->f_op->readv && !file->f_op->read))
 577                return -EINVAL;
 578
 579        return do_readv_writev(READ, file, vec, vlen, pos);
 580}
 581
 582EXPORT_SYMBOL(vfs_readv);
 583
 584ssize_t vfs_writev(struct file *file, const struct iovec __user *vec,
 585                   unsigned long vlen, loff_t *pos)
 586{
 587        if (!(file->f_mode & FMODE_WRITE))
 588                return -EBADF;
 589        if (!file->f_op || (!file->f_op->writev && !file->f_op->write))
 590                return -EINVAL;
 591
 592        return do_readv_writev(WRITE, file, vec, vlen, pos);
 593}
 594
 595EXPORT_SYMBOL(vfs_writev);
 596
 597asmlinkage ssize_t
 598sys_readv(unsigned long fd, const struct iovec __user *vec, unsigned long vlen)
 599{
 600        struct file *file;
 601        ssize_t ret = -EBADF;
 602        int fput_needed;
 603
 604        file = fget_light(fd, &fput_needed);
 605        if (file) {
 606                loff_t pos = file_pos_read(file);
 607                ret = vfs_readv(file, vec, vlen, &pos);
 608                file_pos_write(file, pos);
 609                fput_light(file, fput_needed);
 610        }
 611
 612        if (ret > 0)
 613                current->rchar += ret;
 614        current->syscr++;
 615        return ret;
 616}
 617
 618asmlinkage ssize_t
 619sys_writev(unsigned long fd, const struct iovec __user *vec, unsigned long vlen)
 620{
 621        struct file *file;
 622        ssize_t ret = -EBADF;
 623        int fput_needed;
 624
 625        file = fget_light(fd, &fput_needed);
 626        if (file) {
 627                loff_t pos = file_pos_read(file);
 628                ret = vfs_writev(file, vec, vlen, &pos);
 629                file_pos_write(file, pos);
 630                fput_light(file, fput_needed);
 631        }
 632
 633        if (ret > 0)
 634                current->wchar += ret;
 635        current->syscw++;
 636        return ret;
 637}
 638
 639static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
 640                           size_t count, loff_t max)
 641{
 642        struct file * in_file, * out_file;
 643        struct inode * in_inode, * out_inode;
 644        loff_t pos;
 645        ssize_t retval;
 646        int fput_needed_in, fput_needed_out;
 647
 648        /*
 649         * Get input file, and verify that it is ok..
 650         */
 651        retval = -EBADF;
 652        in_file = fget_light(in_fd, &fput_needed_in);
 653        if (!in_file)
 654                goto out;
 655        if (!(in_file->f_mode & FMODE_READ))
 656                goto fput_in;
 657        retval = -EINVAL;
 658        in_inode = in_file->f_dentry->d_inode;
 659        if (!in_inode)
 660                goto fput_in;
 661        if (!in_file->f_op || !in_file->f_op->sendfile)
 662                goto fput_in;
 663        retval = -ESPIPE;
 664        if (!ppos)
 665                ppos = &in_file->f_pos;
 666        else
 667                if (!(in_file->f_mode & FMODE_PREAD))
 668                        goto fput_in;
 669        retval = rw_verify_area(READ, in_file, ppos, count);
 670        if (retval < 0)
 671                goto fput_in;
 672        count = retval;
 673
 674        retval = security_file_permission (in_file, MAY_READ);
 675        if (retval)
 676                goto fput_in;
 677
 678        /*
 679         * Get output file, and verify that it is ok..
 680         */
 681        retval = -EBADF;
 682        out_file = fget_light(out_fd, &fput_needed_out);
 683        if (!out_file)
 684                goto fput_in;
 685        if (!(out_file->f_mode & FMODE_WRITE))
 686                goto fput_out;
 687        retval = -EINVAL;
 688        if (!out_file->f_op || !out_file->f_op->sendpage)
 689                goto fput_out;
 690        out_inode = out_file->f_dentry->d_inode;
 691        retval = rw_verify_area(WRITE, out_file, &out_file->f_pos, count);
 692        if (retval < 0)
 693                goto fput_out;
 694        count = retval;
 695
 696        retval = security_file_permission (out_file, MAY_WRITE);
 697        if (retval)
 698                goto fput_out;
 699
 700        if (!max)
 701                max = min(in_inode->i_sb->s_maxbytes, out_inode->i_sb->s_maxbytes);
 702
 703        pos = *ppos;
 704        retval = -EINVAL;
 705        if (unlikely(pos < 0))
 706                goto fput_out;
 707        if (unlikely(pos + count > max)) {
 708                retval = -EOVERFLOW;
 709                if (pos >= max)
 710                        goto fput_out;
 711                count = max - pos;
 712        }
 713
 714        retval = in_file->f_op->sendfile(in_file, ppos, count, file_send_actor, out_file);
 715
 716        if (retval > 0) {
 717                current->rchar += retval;
 718                current->wchar += retval;
 719        }
 720        current->syscr++;
 721        current->syscw++;
 722
 723        if (*ppos > max)
 724                retval = -EOVERFLOW;
 725
 726fput_out:
 727        fput_light(out_file, fput_needed_out);
 728fput_in:
 729        fput_light(in_file, fput_needed_in);
 730out:
 731        return retval;
 732}
 733
 734asmlinkage ssize_t sys_sendfile(int out_fd, int in_fd, off_t __user *offset, size_t count)
 735{
 736        loff_t pos;
 737        off_t off;
 738        ssize_t ret;
 739
 740        if (offset) {
 741                if (unlikely(get_user(off, offset)))
 742                        return -EFAULT;
 743                pos = off;
 744                ret = do_sendfile(out_fd, in_fd, &pos, count, MAX_NON_LFS);
 745                if (unlikely(put_user(pos, offset)))
 746                        return -EFAULT;
 747                return ret;
 748        }
 749
 750        return do_sendfile(out_fd, in_fd, NULL, count, 0);
 751}
 752
 753asmlinkage ssize_t sys_sendfile64(int out_fd, int in_fd, loff_t __user *offset, size_t count)
 754{
 755        loff_t pos;
 756        ssize_t ret;
 757
 758        if (offset) {
 759                if (unlikely(copy_from_user(&pos, offset, sizeof(loff_t))))
 760                        return -EFAULT;
 761                ret = do_sendfile(out_fd, in_fd, &pos, count, 0);
 762                if (unlikely(put_user(pos, offset)))
 763                        return -EFAULT;
 764                return ret;
 765        }
 766
 767        return do_sendfile(out_fd, in_fd, NULL, count, 0);
 768}
 769
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