fs/open.c

   1 /*
   2  *  linux/fs/open.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 #include <linux/string.h>
   8 #include <linux/mm.h>
   9 #include <linux/utime.h>
  10 #include <linux/file.h>
  11 #include <linux/smp_lock.h>
  12 #include <linux/quotaops.h>
  13 #include <linux/module.h>
  14 #include <linux/slab.h>
  15
  16 #include <asm/uaccess.h>
  17
  18 int vfs_statfs(struct super_block *sb, struct statfs *buf)
  19 {
  20         int retval = -ENODEV;
  21
  22         if (sb) {
  23                 retval = -ENOSYS;
  24                 if (sb->s_op && sb->s_op->statfs) {
  25                         memset(buf, 0, sizeof(struct statfs));
  26                         lock_kernel();
  27                         retval = sb->s_op->statfs(sb, buf);
  28                         unlock_kernel();
  29                 }
  30         }
  31         return retval;
  32 }
  33
  34
  35 asmlinkage long sys_statfs(const char * path, struct statfs * buf)
  36 {
  37         struct nameidata nd;
  38         int error;
  39
  40         error = user_path_walk(path, &nd);
  41         if (!error) {
  42                 struct statfs tmp;
  43                 error = vfs_statfs(nd.dentry->d_inode->i_sb, &tmp);
  44                 if (!error && copy_to_user(buf, &tmp, sizeof(struct statfs)))
  45                         error = -EFAULT;
  46                 path_release(&nd);
  47         }
  48         return error;
  49 }
  50
  51 asmlinkage long sys_fstatfs(unsigned int fd, struct statfs * buf)
  52 {
  53         struct file * file;
  54         struct statfs tmp;
  55         int error;
  56
  57         error = -EBADF;
  58         file = fget(fd);
  59         if (!file)
  60                 goto out;
  61         error = vfs_statfs(file->f_dentry->d_inode->i_sb, &tmp);
  62         if (!error && copy_to_user(buf, &tmp, sizeof(struct statfs)))
  63                 error = -EFAULT;
  64         fput(file);
  65 out:
  66         return error;
  67 }
  68
  69 int do_truncate(struct dentry *dentry, loff_t length)
  70 {
  71         struct inode *inode = dentry->d_inode;
  72         int error;
  73         struct iattr newattrs;
  74
  75         /* Not pretty: "inode->i_size" shouldn't really be signed. But it is. */
  76         if (length < 0)
  77                 return -EINVAL;
  78
  79         down(&inode->i_sem);
  80         newattrs.ia_size = length;
  81         newattrs.ia_valid = ATTR_SIZE | ATTR_CTIME;
  82         error = notify_change(dentry, &newattrs);
  83         up(&inode->i_sem);
  84         return error;
  85 }
  86
  87 static inline long do_sys_truncate(const char * path, loff_t length)
  88 {
  89         struct nameidata nd;
  90         struct inode * inode;
  91         int error;
  92
  93         error = -EINVAL;
  94         if (length < 0) /* sorry, but loff_t says... */
  95                 goto out;
  96
  97         error = user_path_walk(path, &nd);
  98         if (error)
  99                 goto out;
 100         inode = nd.dentry->d_inode;
 101
 102         error = -EACCES;
 103         if (S_ISDIR(inode->i_mode))
 104                 goto dput_and_out;
 105
 106         error = permission(inode,MAY_WRITE);
 107         if (error)
 108                 goto dput_and_out;
 109
 110         error = -EROFS;
 111         if (IS_RDONLY(inode))
 112                 goto dput_and_out;
 113
 114         error = -EPERM;
 115         if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
 116                 goto dput_and_out;
 117
 118         error = get_write_access(inode);
 119         if (error)
 120                 goto dput_and_out;
 121
 122         error = locks_verify_truncate(inode, NULL, length);
 123         if (!error) {
 124                 DQUOT_INIT(inode);
 125                 error = do_truncate(nd.dentry, length);
 126         }
 127         put_write_access(inode);
 128
 129 dput_and_out:
 130         path_release(&nd);
 131 out:
 132         return error;
 133 }
 134
 135 asmlinkage long sys_truncate(const char * path, unsigned long length)
 136 {
 137         return do_sys_truncate(path, length);
 138 }
 139
 140 static inline long do_sys_ftruncate(unsigned int fd, loff_t length)
 141 {
 142         struct inode * inode;
 143         struct dentry *dentry;
 144         struct file * file;
 145         int error;
 146
 147         error = -EINVAL;
 148         if (length < 0)
 149                 goto out;
 150         error = -EBADF;
 151         file = fget(fd);
 152         if (!file)
 153                 goto out;
 154         dentry = file->f_dentry;
 155         inode = dentry->d_inode;
 156         error = -EACCES;
 157         if (S_ISDIR(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
 158                 goto out_putf;
 159         error = -EPERM;
 160         if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
 161                 goto out_putf;
 162
 163         error = locks_verify_truncate(inode, file, length);
 164         if (!error)
 165                 error = do_truncate(dentry, length);
 166 out_putf:
 167         fput(file);
 168 out:
 169         return error;
 170 }
 171
 172 asmlinkage long sys_ftruncate(unsigned int fd, unsigned long length)
 173 {
 174         return do_sys_ftruncate(fd, length);
 175 }
 176
 177 /* LFS versions of truncate are only needed on 32 bit machines */
 178 #if BITS_PER_LONG == 32
 179 asmlinkage long sys_truncate64(const char * path, loff_t length)
 180 {
 181         return do_sys_truncate(path, length);
 182 }
 183
 184 asmlinkage long sys_ftruncate64(unsigned int fd, loff_t length)
 185 {
 186         return do_sys_ftruncate(fd, length);
 187 }
 188 #endif
 189
 190 #if !(defined(__alpha__) || defined(__ia64__))
 191
 192 /*
 193  * sys_utime() can be implemented in user-level using sys_utimes().
 194  * Is this for backwards compatibility?  If so, why not move it
 195  * into the appropriate arch directory (for those architectures that
 196  * need it).
 197  */
 198
 199 /* If times==NULL, set access and modification to current time,
 200  * must be owner or have write permission.
 201  * Else, update from *times, must be owner or super user.
 202  */
 203 asmlinkage long sys_utime(char * filename, struct utimbuf * times)
 204 {
 205         int error;
 206         struct nameidata nd;
 207         struct inode * inode;
 208         struct iattr newattrs;
 209
 210         error = user_path_walk(filename, &nd);
 211         if (error)
 212                 goto out;
 213         inode = nd.dentry->d_inode;
 214
 215         error = -EROFS;
 216         if (IS_RDONLY(inode))
 217                 goto dput_and_out;
 218
 219         /* Don't worry, the checks are done in inode_change_ok() */
 220         newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
 221         if (times) {
 222                 error = get_user(newattrs.ia_atime, &times->actime);
 223                 if (!error)
 224                         error = get_user(newattrs.ia_mtime, &times->modtime);
 225                 if (error)
 226                         goto dput_and_out;
 227
 228                 newattrs.ia_valid |= ATTR_ATIME_SET | ATTR_MTIME_SET;
 229         } else {
 230                 if (current->fsuid != inode->i_uid &&
 231                     (error = permission(inode,MAY_WRITE)) != 0)
 232                         goto dput_and_out;
 233         }
 234         error = notify_change(nd.dentry, &newattrs);
 235 dput_and_out:
 236         path_release(&nd);
 237 out:
 238         return error;
 239 }
 240
 241 #endif
 242
 243 /* If times==NULL, set access and modification to current time,
 244  * must be owner or have write permission.
 245  * Else, update from *times, must be owner or super user.
 246  */
 247 asmlinkage long sys_utimes(char * filename, struct timeval * utimes)
 248 {
 249         int error;
 250         struct nameidata nd;
 251         struct inode * inode;
 252         struct iattr newattrs;
 253
 254         error = user_path_walk(filename, &nd);
 255
 256         if (error)
 257                 goto out;
 258         inode = nd.dentry->d_inode;
 259
 260         error = -EROFS;
 261         if (IS_RDONLY(inode))
 262                 goto dput_and_out;
 263
 264         /* Don't worry, the checks are done in inode_change_ok() */
 265         newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
 266         if (utimes) {
 267                 struct timeval times[2];
 268                 error = -EFAULT;
 269                 if (copy_from_user(&times, utimes, sizeof(times)))
 270                         goto dput_and_out;
 271                 newattrs.ia_atime = times[0].tv_sec;
 272                 newattrs.ia_mtime = times[1].tv_sec;
 273                 newattrs.ia_valid |= ATTR_ATIME_SET | ATTR_MTIME_SET;
 274         } else {
 275                 if ((error = permission(inode,MAY_WRITE)) != 0)
 276                         goto dput_and_out;
 277         }
 278         error = notify_change(nd.dentry, &newattrs);
 279 dput_and_out:
 280         path_release(&nd);
 281 out:
 282         return error;
 283 }
 284
 285 /*
 286  * access() needs to use the real uid/gid, not the effective uid/gid.
 287  * We do this by temporarily clearing all FS-related capabilities and
 288  * switching the fsuid/fsgid around to the real ones.
 289  */
 290 asmlinkage long sys_access(const char * filename, int mode)
 291 {
 292         struct nameidata nd;
 293         int old_fsuid, old_fsgid;
 294         kernel_cap_t old_cap;
 295         int res;
 296
 297         if (mode & ~S_IRWXO)    /* where's F_OK, X_OK, W_OK, R_OK? */
 298                 return -EINVAL;
 299
 300         old_fsuid = current->fsuid;
 301         old_fsgid = current->fsgid;
 302         old_cap = current->cap_effective;
 303
 304         current->fsuid = current->uid;
 305         current->fsgid = current->gid;
 306
 307         /* Clear the capabilities if we switch to a non-root user */
 308         if (current->uid)
 309                 cap_clear(current->cap_effective);
 310         else
 311                 current->cap_effective = current->cap_permitted;
 312
 313         res = user_path_walk(filename, &nd);
 314         if (!res) {
 315                 res = permission(nd.dentry->d_inode, mode);
 316                 /* SuS v2 requires we report a read only fs too */
 317                 if(!res && (mode & S_IWOTH) && IS_RDONLY(nd.dentry->d_inode))
 318                         res = -EROFS;
 319                 path_release(&nd);
 320         }
 321
 322         current->fsuid = old_fsuid;
 323         current->fsgid = old_fsgid;
 324         current->cap_effective = old_cap;
 325
 326         return res;
 327 }
 328
 329 asmlinkage long sys_chdir(const char * filename)
 330 {
 331         int error;
 332         struct nameidata nd;
 333         char *name;
 334
 335         name = getname(filename);
 336         error = PTR_ERR(name);
 337         if (IS_ERR(name))
 338                 goto out;
 339
 340         error = 0;
 341         if (path_init(name,LOOKUP_POSITIVE|LOOKUP_FOLLOW|LOOKUP_DIRECTORY,&nd))
 342                 error = path_walk(name, &nd);
 343         putname(name);
 344         if (error)
 345                 goto out;
 346
 347         error = permission(nd.dentry->d_inode,MAY_EXEC);
 348         if (error)
 349                 goto dput_and_out;
 350
 351         set_fs_pwd(current->fs, nd.mnt, nd.dentry);
 352
 353 dput_and_out:
 354         path_release(&nd);
 355 out:
 356         return error;
 357 }
 358
 359 asmlinkage long sys_fchdir(unsigned int fd)
 360 {
 361         struct file *file;
 362         struct dentry *dentry;
 363         struct inode *inode;
 364         struct vfsmount *mnt;
 365         int error;
 366
 367         error = -EBADF;
 368         file = fget(fd);
 369         if (!file)
 370                 goto out;
 371
 372         dentry = file->f_dentry;
 373         mnt = file->f_vfsmnt;
 374         inode = dentry->d_inode;
 375
 376         error = -ENOTDIR;
 377         if (!S_ISDIR(inode->i_mode))
 378                 goto out_putf;
 379
 380         error = permission(inode, MAY_EXEC);
 381         if (!error)
 382                 set_fs_pwd(current->fs, mnt, dentry);
 383 out_putf:
 384         fput(file);
 385 out:
 386         return error;
 387 }
 388
 389 asmlinkage long sys_chroot(const char * filename)
 390 {
 391         int error;
 392         struct nameidata nd;
 393         char *name;
 394
 395         name = getname(filename);
 396         error = PTR_ERR(name);
 397         if (IS_ERR(name))
 398                 goto out;
 399
 400         path_init(name, LOOKUP_POSITIVE | LOOKUP_FOLLOW |
 401                       LOOKUP_DIRECTORY | LOOKUP_NOALT, &nd);
 402         error = path_walk(name, &nd);
 403         putname(name);
 404         if (error)
 405                 goto out;
 406
 407         error = permission(nd.dentry->d_inode,MAY_EXEC);
 408         if (error)
 409                 goto dput_and_out;
 410
 411         error = -EPERM;
 412         if (!capable(CAP_SYS_CHROOT))
 413                 goto dput_and_out;
 414
 415         set_fs_root(current->fs, nd.mnt, nd.dentry);
 416         set_fs_altroot();
 417         error = 0;
 418 dput_and_out:
 419         path_release(&nd);
 420 out:
 421         return error;
 422 }
 423
 424 asmlinkage long sys_fchmod(unsigned int fd, mode_t mode)
 425 {
 426         struct inode * inode;
 427         struct dentry * dentry;
 428         struct file * file;
 429         int err = -EBADF;
 430         struct iattr newattrs;
 431
 432         file = fget(fd);
 433         if (!file)
 434                 goto out;
 435
 436         dentry = file->f_dentry;
 437         inode = dentry->d_inode;
 438
 439         err = -EROFS;
 440         if (IS_RDONLY(inode))
 441                 goto out_putf;
 442         err = -EPERM;
 443         if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
 444                 goto out_putf;
 445         if (mode == (mode_t) -1)
 446                 mode = inode->i_mode;
 447         newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
 448         newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
 449         err = notify_change(dentry, &newattrs);
 450
 451 out_putf:
 452         fput(file);
 453 out:
 454         return err;
 455 }
 456
 457 asmlinkage long sys_chmod(const char * filename, mode_t mode)
 458 {
 459         struct nameidata nd;
 460         struct inode * inode;
 461         int error;
 462         struct iattr newattrs;
 463
 464         error = user_path_walk(filename, &nd);
 465         if (error)
 466                 goto out;
 467         inode = nd.dentry->d_inode;
 468
 469         error = -EROFS;
 470         if (IS_RDONLY(inode))
 471                 goto dput_and_out;
 472
 473         error = -EPERM;
 474         if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
 475                 goto dput_and_out;
 476
 477         if (mode == (mode_t) -1)
 478                 mode = inode->i_mode;
 479         newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
 480         newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
 481         error = notify_change(nd.dentry, &newattrs);
 482
 483 dput_and_out:
 484         path_release(&nd);
 485 out:
 486         return error;
 487 }
 488
 489 static int chown_common(struct dentry * dentry, uid_t user, gid_t group)
 490 {
 491         struct inode * inode;
 492         int error;
 493         struct iattr newattrs;
 494
 495         error = -ENOENT;
 496         if (!(inode = dentry->d_inode)) {
 497                 printk("chown_common: NULL inode\n");
 498                 goto out;
 499         }
 500         error = -EROFS;
 501         if (IS_RDONLY(inode))
 502                 goto out;
 503         error = -EPERM;
 504         if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
 505                 goto out;
 506         if (user == (uid_t) -1)
 507                 user = inode->i_uid;
 508         if (group == (gid_t) -1)
 509                 group = inode->i_gid;
 510         newattrs.ia_mode = inode->i_mode;
 511         newattrs.ia_uid = user;
 512         newattrs.ia_gid = group;
 513         newattrs.ia_valid =  ATTR_UID | ATTR_GID | ATTR_CTIME;
 514         /*
 515          * If the user or group of a non-directory has been changed by a
 516          * non-root user, remove the setuid bit.
 517          * 19981026     David C Niemi <niemi@tux.org>
 518          *
 519          * Changed this to apply to all users, including root, to avoid
 520          * some races. This is the behavior we had in 2.0. The check for
 521          * non-root was definitely wrong for 2.2 anyway, as it should
 522          * have been using CAP_FSETID rather than fsuid -- 19990830 SD.
 523          */
 524         if ((inode->i_mode & S_ISUID) == S_ISUID &&
 525                 !S_ISDIR(inode->i_mode))
 526         {
 527                 newattrs.ia_mode &= ~S_ISUID;
 528                 newattrs.ia_valid |= ATTR_MODE;
 529         }
 530         /*
 531          * Likewise, if the user or group of a non-directory has been changed
 532          * by a non-root user, remove the setgid bit UNLESS there is no group
 533          * execute bit (this would be a file marked for mandatory locking).
 534          * 19981026     David C Niemi <niemi@tux.org>
 535          *
 536          * Removed the fsuid check (see the comment above) -- 19990830 SD.
 537          */
 538         if (((inode->i_mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
 539                 && !S_ISDIR(inode->i_mode))
 540         {
 541                 newattrs.ia_mode &= ~S_ISGID;
 542                 newattrs.ia_valid |= ATTR_MODE;
 543         }
 544         error = DQUOT_TRANSFER(dentry, &newattrs);
 545 out:
 546         return error;
 547 }
 548
 549 asmlinkage long sys_chown(const char * filename, uid_t user, gid_t group)
 550 {
 551         struct nameidata nd;
 552         int error;
 553
 554         error = user_path_walk(filename, &nd);
 555         if (!error) {
 556                 error = chown_common(nd.dentry, user, group);
 557                 path_release(&nd);
 558         }
 559         return error;
 560 }
 561
 562 asmlinkage long sys_lchown(const char * filename, uid_t user, gid_t group)
 563 {
 564         struct nameidata nd;
 565         int error;
 566
 567         error = user_path_walk_link(filename, &nd);
 568         if (!error) {
 569                 error = chown_common(nd.dentry, user, group);
 570                 path_release(&nd);
 571         }
 572         return error;
 573 }
 574
 575
 576 asmlinkage long sys_fchown(unsigned int fd, uid_t user, gid_t group)
 577 {
 578         struct file * file;
 579         int error = -EBADF;
 580
 581         file = fget(fd);
 582         if (file) {
 583                 error = chown_common(file->f_dentry, user, group);
 584                 fput(file);
 585         }
 586         return error;
 587 }
 588
 589 /*
 590  * Note that while the flag value (low two bits) for sys_open means:
 591  *      00 - read-only
 592  *      01 - write-only
 593  *      10 - read-write
 594  *      11 - special
 595  * it is changed into
 596  *      00 - no permissions needed
 597  *      01 - read-permission
 598  *      10 - write-permission
 599  *      11 - read-write
 600  * for the internal routines (ie open_namei()/follow_link() etc). 00 is
 601  * used by symlinks.
 602  */
 603 struct file *filp_open(const char * filename, int flags, int mode)
 604 {
 605         int namei_flags, error;
 606         struct nameidata nd;
 607
 608         namei_flags = flags;
 609         if ((namei_flags+1) & O_ACCMODE)
 610                 namei_flags++;
 611         if (namei_flags & O_TRUNC)
 612                 namei_flags |= 2;
 613
 614         error = open_namei(filename, namei_flags, mode, &nd);
 615         if (!error)
 616                 return dentry_open(nd.dentry, nd.mnt, flags);
 617
 618         return ERR_PTR(error);
 619 }
 620
 621 struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags)
 622 {
 623         struct file * f;
 624         struct inode *inode;
 625         int error;
 626
 627         error = -ENFILE;
 628         f = get_empty_filp();
 629         if (!f)
 630                 goto cleanup_dentry;
 631         f->f_flags = flags;
 632         f->f_mode = (flags+1) & O_ACCMODE;
 633         inode = dentry->d_inode;
 634         if (f->f_mode & FMODE_WRITE) {
 635                 error = get_write_access(inode);
 636                 if (error)
 637                         goto cleanup_file;
 638         }
 639
 640         f->f_dentry = dentry;
 641         f->f_vfsmnt = mnt;
 642         f->f_pos = 0;
 643         f->f_reada = 0;
 644         f->f_op = fops_get(inode->i_fop);
 645         if (inode->i_sb)
 646                 file_move(f, &inode->i_sb->s_files);
 647         if (f->f_op && f->f_op->open) {
 648                 error = f->f_op->open(inode,f);
 649                 if (error)
 650                         goto cleanup_all;
 651         }
 652         f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 653
 654         return f;
 655
 656 cleanup_all:
 657         fops_put(f->f_op);
 658         if (f->f_mode & FMODE_WRITE)
 659                 put_write_access(inode);
 660         f->f_dentry = NULL;
 661         f->f_vfsmnt = NULL;
 662 cleanup_file:
 663         put_filp(f);
 664 cleanup_dentry:
 665         dput(dentry);
 666         mntput(mnt);
 667         return ERR_PTR(error);
 668 }
 669
 670 /*
 671  * Find an empty file descriptor entry, and mark it busy.
 672  */
 673 int get_unused_fd(void)
 674 {
 675         struct files_struct * files = current->files;
 676         int fd, error;
 677
 678         error = -EMFILE;
 679         write_lock(&files->file_lock);
 680
 681 repeat:
 682         fd = find_next_zero_bit(files->open_fds,
 683                                 files->max_fdset,
 684                                 files->next_fd);
 685
 686         /*
 687          * N.B. For clone tasks sharing a files structure, this test
 688          * will limit the total number of files that can be opened.
 689          */
 690         if (fd >= current->rlim[RLIMIT_NOFILE].rlim_cur)
 691                 goto out;
 692
 693         /* Do we need to expand the fdset array? */
 694         if (fd >= files->max_fdset) {
 695                 error = expand_fdset(files, fd);
 696                 if (!error) {
 697                         error = -EMFILE;
 698                         goto repeat;
 699                 }
 700                 goto out;
 701         }
 702
 703         /*
 704          * Check whether we need to expand the fd array.
 705          */
 706         if (fd >= files->max_fds) {
 707                 error = expand_fd_array(files, fd);
 708                 if (!error) {
 709                         error = -EMFILE;
 710                         goto repeat;
 711                 }
 712                 goto out;
 713         }
 714
 715         FD_SET(fd, files->open_fds);
 716         FD_CLR(fd, files->close_on_exec);
 717         files->next_fd = fd + 1;
 718 #if 1
 719         /* Sanity check */
 720         if (files->fd[fd] != NULL) {
 721                 printk("get_unused_fd: slot %d not NULL!\n", fd);
 722                 files->fd[fd] = NULL;
 723         }
 724 #endif
 725         error = fd;
 726
 727 out:
 728         write_unlock(&files->file_lock);
 729         return error;
 730 }
 731
 732 asmlinkage long sys_open(const char * filename, int flags, int mode)
 733 {
 734         char * tmp;
 735         int fd, error;
 736
 737 #if BITS_PER_LONG != 32
 738         flags |= O_LARGEFILE;
 739 #endif
 740         tmp = getname(filename);
 741         fd = PTR_ERR(tmp);
 742         if (!IS_ERR(tmp)) {
 743                 fd = get_unused_fd();
 744                 if (fd >= 0) {
 745                         struct file *f = filp_open(tmp, flags, mode);
 746                         error = PTR_ERR(f);
 747                         if (IS_ERR(f))
 748                                 goto out_error;
 749                         fd_install(fd, f);
 750                 }
 751 out:
 752                 putname(tmp);
 753         }
 754         return fd;
 755
 756 out_error:
 757         put_unused_fd(fd);
 758         fd = error;
 759         goto out;
 760 }
 761
 762 #ifndef __alpha__
 763
 764 /*
 765  * For backward compatibility?  Maybe this should be moved
 766  * into arch/i386 instead?
 767  */
 768 asmlinkage long sys_creat(const char * pathname, int mode)
 769 {
 770         return sys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
 771 }
 772
 773 #endif
 774
 775 /*
 776  * "id" is the POSIX thread ID. We use the
 777  * files pointer for this..
 778  */
 779 int filp_close(struct file *filp, fl_owner_t id)
 780 {
 781         int retval;
 782
 783         if (!file_count(filp)) {
 784                 printk("VFS: Close: file count is 0\n");
 785                 return 0;
 786         }
 787         retval = 0;
 788         if (filp->f_op && filp->f_op->flush) {
 789                 lock_kernel();
 790                 retval = filp->f_op->flush(filp);
 791                 unlock_kernel();
 792         }
 793         locks_remove_posix(filp, id);
 794         fput(filp);
 795         return retval;
 796 }
 797
 798 /*
 799  * Careful here! We test whether the file pointer is NULL before
 800  * releasing the fd. This ensures that one clone task can't release
 801  * an fd while another clone is opening it.
 802  */
 803 asmlinkage long sys_close(unsigned int fd)
 804 {
 805         struct file * filp;
 806         struct files_struct *files = current->files;
 807
 808         write_lock(&files->file_lock);
 809         if (fd >= files->max_fds)
 810                 goto out_unlock;
 811         filp = files->fd[fd];
 812         if (!filp)
 813                 goto out_unlock;
 814         files->fd[fd] = NULL;
 815         FD_CLR(fd, files->close_on_exec);
 816         __put_unused_fd(files, fd);
 817         write_unlock(&files->file_lock);
 818         return filp_close(filp, files);
 819
 820 out_unlock:
 821         write_unlock(&files->file_lock);
 822         return -EBADF;
 823 }
 824
 825 /*
 826  * This routine simulates a hangup on the tty, to arrange that users
 827  * are given clean terminals at login time.
 828  */
 829 asmlinkage long sys_vhangup(void)
 830 {
 831         if (capable(CAP_SYS_TTY_CONFIG)) {
 832                 tty_vhangup(current->tty);
 833                 return 0;
 834         }
 835         return -EPERM;
 836 }