fd.c

   1 /*
   2  * Copyright (C) 2006-2009 Andre Noll <maan@systemlinux.org>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6
   7 /** \file fd.c Helper functions for file descriptor handling. */
   8
   9 #include <regex.h>
  10 #include <sys/types.h>
  11 #include <dirent.h>
  12 #include <sys/mman.h>
  13 #include <fcntl.h>
  14 #include <sys/select.h>
  15
  16 #include "para.h"
  17 #include "error.h"
  18 #include "string.h"
  19
  20 /**
  21  * Write a buffer to a file descriptor, re-write on short writes.
  22  *
  23  * \param fd The file descriptor.
  24  * \param buf The buffer to be sent.
  25  * \param len The length of \a buf.
  26  *
  27  * \return Standard. In any case, the number of bytes that have been written is
  28  * stored in \a len.
  29  */
  30 int write_all(int fd, const char *buf, size_t *len)
  31 {
  32         size_t total = *len;
  33
  34         assert(total);
  35         *len = 0;
  36         while (*len < total) {
  37                 int ret = write(fd, buf + *len, total - *len);
  38                 if (ret == -1)
  39                         return -ERRNO_TO_PARA_ERROR(errno);
  40                 *len += ret;
  41         }
  42         return 1;
  43 }
  44
  45 /**
  46  * Write a buffer to a non-blocking file descriptor.
  47  *
  48  * \param fd The file descriptor.
  49  * \param buf the buffer to write.
  50  * \param len the number of bytes of \a buf.
  51  * \param max_bytes_per_write Do not write more than that many bytes at once.
  52  *
  53  * If \a max_bytes_per_write is non-zero, do not send more than that many bytes
  54  * per write().
  55  *
  56  * EAGAIN is not considered an error condition.  For example CCID3 has a
  57  * sending wait queue which fills up and is emptied asynchronously. The EAGAIN
  58  * case means that there is currently no space in the wait queue, but this can
  59  * change at any moment.
  60  *
  61  * \return Negative on errors, number of bytes written else.
  62  */
  63 int write_nonblock(int fd, const char *buf, size_t len,
  64                 size_t max_bytes_per_write)
  65 {
  66         size_t written = 0;
  67         int ret = 0;
  68
  69         while (written < len) {
  70                 size_t num = len - written;
  71
  72                 if (max_bytes_per_write && max_bytes_per_write < num)
  73                         num = max_bytes_per_write;
  74                 ret = write(fd, buf + written, num);
  75                 if (ret < 0 && errno == EAGAIN)
  76                         return written;
  77                 if (ret < 0)
  78                         return -ERRNO_TO_PARA_ERROR(errno);
  79                 written += ret;
  80         }
  81         return written;
  82 }
  83
  84 /**
  85  * Simple wrapper for readv().
  86  *
  87  * \param fd The file descriptor to read from.
  88  * \param iov Scatter/gather array used in readv().
  89  * \param iovcnt Number of elements in \a iov.
  90  *
  91  * \return A negative error code on errors, the return value of the underlying
  92  * call to readv() otherwise.
  93  *
  94  * \sa readv(2).
  95  */
  96 int para_readv(int fd, struct iovec *iov, int iovcnt)
  97 {
  98         int ret = readv(fd, iov, iovcnt);
  99
 100         if (ret < 0)
 101                 return -ERRNO_TO_PARA_ERROR(errno);
 102         return ret;
 103 }
 104
 105 /**
 106  * Check whether a file exists.
 107  *
 108  * \param fn The file name.
 109  *
 110  * \return Non-zero iff file exists.
 111  */
 112 int file_exists(const char *fn)
 113 {
 114         struct stat statbuf;
 115
 116         return !stat(fn, &statbuf);
 117 }
 118
 119 /**
 120  * Paraslash's wrapper for select(2).
 121  *
 122  * It calls select(2) (with no exceptfds) and starts over if select() was
 123  * interrupted by a signal.
 124  *
 125  * \param n The highest-numbered descriptor in any of the two sets, plus 1.
 126  * \param readfds fds that should be checked for readability.
 127  * \param writefds fds that should be checked for writablility.
 128  * \param timeout_tv upper bound on the amount of time elapsed before select()
 129  * returns.
 130  *
 131  * \return The return value of the underlying select() call on success, the
 132  * negative system error code on errors.
 133  *
 134  * All arguments are passed verbatim to select(2).
 135  * \sa select(2) select_tut(2).
 136  */
 137 int para_select(int n, fd_set *readfds, fd_set *writefds,
 138                 struct timeval *timeout_tv)
 139 {
 140         int ret;
 141         do
 142                 ret = select(n, readfds, writefds, NULL, timeout_tv);
 143         while (ret < 0 && errno == EINTR);
 144         if (ret < 0)
 145                 return -ERRNO_TO_PARA_ERROR(errno);
 146         return ret;
 147 }
 148
 149 /**
 150  * Set a file descriptor to blocking mode.
 151  *
 152  * \param fd The file descriptor.
 153  *
 154  * \return Standard.
 155  */
 156 __must_check int mark_fd_blocking(int fd)
 157 {
 158         int flags = fcntl(fd, F_GETFL);
 159         if (flags < 0)
 160                 return -ERRNO_TO_PARA_ERROR(errno);
 161         flags = fcntl(fd, F_SETFL, ((long)flags) & ~O_NONBLOCK);
 162         if (flags < 0)
 163                 return -ERRNO_TO_PARA_ERROR(errno);
 164         return 1;
 165 }
 166
 167 /**
 168  * Set a file descriptor to non-blocking mode.
 169  *
 170  * \param fd The file descriptor.
 171  *
 172  * \return Standard.
 173  */
 174 __must_check int mark_fd_nonblocking(int fd)
 175 {
 176         int flags = fcntl(fd, F_GETFL);
 177         if (flags < 0)
 178                 return -ERRNO_TO_PARA_ERROR(errno);
 179         flags = fcntl(fd, F_SETFL, ((long)flags) | O_NONBLOCK);
 180         if (flags < 0)
 181                 return -ERRNO_TO_PARA_ERROR(errno);
 182         return 1;
 183 }
 184
 185 /**
 186  * Set a file descriptor in a fd_set.
 187  *
 188  * \param fd The file descriptor to be set.
 189  * \param fds The file descriptor set.
 190  * \param max_fileno Highest-numbered file descriptor.
 191  *
 192  * This wrapper for FD_SET() passes its first two arguments to \p FD_SET. Upon
 193  * return, \a max_fileno contains the maximum of the old_value and \a fd.
 194  *
 195  * \sa para_select.
 196 */
 197 void para_fd_set(int fd, fd_set *fds, int *max_fileno)
 198 {
 199         assert(fd >= 0 && fd < FD_SETSIZE);
 200 #if 0
 201         {
 202                 int flags = fcntl(fd, F_GETFL);
 203                 if (!(flags & O_NONBLOCK)) {
 204                         PARA_EMERG_LOG("fd %d is a blocking file descriptor\n", fd);
 205                         exit(EXIT_FAILURE);
 206                 }
 207         }
 208 #endif
 209         FD_SET(fd, fds);
 210         *max_fileno = PARA_MAX(*max_fileno, fd);
 211 }
 212
 213 /**
 214  * Paraslash's wrapper for fgets(3).
 215  *
 216  * \param line Pointer to the buffer to store the line.
 217  * \param size The size of the buffer given by \a line.
 218  * \param f The stream to read from.
 219  *
 220  * \return Unlike the standard fgets() function, an integer value
 221  * is returned. On success, this function returns 1. On errors, -E_FGETS
 222  * is returned. A zero return value indicates an end of file condition.
 223  */
 224 __must_check int para_fgets(char *line, int size, FILE *f)
 225 {
 226 again:
 227         if (fgets(line, size, f))
 228                 return 1;
 229         if (feof(f))
 230                 return 0;
 231         if (!ferror(f))
 232                 return -E_FGETS;
 233         if (errno != EINTR) {
 234                 PARA_ERROR_LOG("%s\n", strerror(errno));
 235                 return -E_FGETS;
 236         }
 237         clearerr(f);
 238         goto again;
 239 }
 240
 241 /**
 242  * Paraslash's wrapper for mmap.
 243  *
 244  * \param length Number of bytes to mmap.
 245  * \param prot Either PROT_NONE or the bitwise OR of one or more of
 246  * PROT_EXEC PROT_READ PROT_WRITE.
 247  * \param flags Exactly one of MAP_SHARED and MAP_PRIVATE.
 248  * \param fd The file to mmap from.
 249  * \param offset Mmap start.
 250  * \param map Result pointer.
 251  *
 252  * \return Standard.
 253  *
 254  * \sa mmap(2).
 255  */
 256 int para_mmap(size_t length, int prot, int flags, int fd, off_t offset,
 257                 void *map)
 258 {
 259         void **m = map;
 260
 261         errno = EINVAL;
 262         if (!length)
 263                 goto err;
 264         *m = mmap(NULL, length, prot, flags, fd, offset);
 265         if (*m != MAP_FAILED)
 266                 return 1;
 267 err:
 268         *m = NULL;
 269         return -ERRNO_TO_PARA_ERROR(errno);
 270 }
 271
 272 /**
 273  * Wrapper for the open(2) system call.
 274  *
 275  * \param path The filename.
 276  * \param flags The usual open(2) flags.
 277  * \param mode Specifies the permissions to use.
 278  *
 279  * The mode parameter must be specified when O_CREAT is in the flags, and is
 280  * ignored otherwise.
 281  *
 282  * \return The file descriptor on success, negative on errors.
 283  *
 284  * \sa open(2).
 285  */
 286 int para_open(const char *path, int flags, mode_t mode)
 287 {
 288         int ret = open(path, flags, mode);
 289
 290         if (ret >= 0)
 291                 return ret;
 292         return -ERRNO_TO_PARA_ERROR(errno);
 293 }
 294
 295 /**
 296  * Wrapper for chdir(2).
 297  *
 298  * \param path The specified directory.
 299  *
 300  * \return Standard.
 301  */
 302 int para_chdir(const char *path)
 303 {
 304         int ret = chdir(path);
 305
 306         if (ret >= 0)
 307                 return 1;
 308         return -ERRNO_TO_PARA_ERROR(errno);
 309 }
 310
 311 /**
 312  * Save the cwd and open a given directory.
 313  *
 314  * \param dirname Path to the directory to open.
 315  * \param dir Result pointer.
 316  * \param cwd File descriptor of the current working directory.
 317  *
 318  * \return Standard.
 319  *
 320  * Opening the current directory (".") and calling fchdir() to return is
 321  * usually faster and more reliable than saving cwd in some buffer and calling
 322  * chdir() afterwards.
 323  *
 324  * If \a cwd is not \p NULL "." is opened and the resulting file descriptor is
 325  * stored in \a cwd. If the function returns success, and \a cwd is not \p
 326  * NULL, the caller must close this file descriptor (probably after calling
 327  * fchdir(*cwd)).
 328  *
 329  * On errors, the function undos everything, so the caller needs neither close
 330  * any files, nor change back to the original working directory.
 331  *
 332  * \sa getcwd(3).
 333  *
 334  */
 335 int para_opendir(const char *dirname, DIR **dir, int *cwd)
 336 {
 337         int ret;
 338
 339         if (cwd) {
 340                 ret = para_open(".", O_RDONLY, 0);
 341                 if (ret < 0)
 342                         return ret;
 343                 *cwd = ret;
 344         }
 345         ret = para_chdir(dirname);
 346         if (ret < 0)
 347                 goto close_cwd;
 348         *dir = opendir(".");
 349         if (*dir)
 350                 return 1;
 351         ret = -ERRNO_TO_PARA_ERROR(errno);
 352         /* Ignore return value of fchdir() and close(). We're busted anyway. */
 353         if (cwd) {
 354                 int __a_unused ret2 = fchdir(*cwd); /* STFU, gcc */
 355         }
 356 close_cwd:
 357         if (cwd)
 358                 close(*cwd);
 359         return ret;
 360 }
 361
 362 /**
 363  * A wrapper for fchdir().
 364  *
 365  * \param fd An open file descriptor.
 366  *
 367  * \return Standard.
 368  */
 369 int para_fchdir(int fd)
 370 {
 371         if (fchdir(fd) < 0)
 372                 return -ERRNO_TO_PARA_ERROR(errno);
 373         return 1;
 374 }
 375
 376 /**
 377  * A wrapper for mkdir(2).
 378  *
 379  * \param path Name of the directory to create.
 380  * \param mode The permissions to use.
 381  *
 382  * \return Standard.
 383  */
 384 int para_mkdir(const char *path, mode_t mode)
 385 {
 386         if (!mkdir(path, mode))
 387                 return 1;
 388         return -ERRNO_TO_PARA_ERROR(errno);
 389 }
 390
 391 /**
 392  * Open a file and map it into memory.
 393  *
 394  * \param path Name of the regular file to map.
 395  * \param open_mode Either \p O_RDONLY or \p O_RDWR.
 396  * \param map On success, the mapping is returned here.
 397  * \param size size of the mapping.
 398  * \param fd_ptr The file descriptor of the mapping.
 399  *
 400  * If \a fd_ptr is \p NULL, the file descriptor resulting from the underlying
 401  * open call is closed after mmap().  Otherwise the file is kept open and the
 402  * file descriptor is returned in \a fd_ptr.
 403  *
 404  * \return Standard.
 405  *
 406  * \sa para_open(), mmap(2).
 407  */
 408 int mmap_full_file(const char *path, int open_mode, void **map,
 409                 size_t *size, int *fd_ptr)
 410 {
 411         int fd, ret, mmap_prot, mmap_flags;
 412         struct stat file_status;
 413
 414         if (open_mode == O_RDONLY) {
 415                 mmap_prot = PROT_READ;
 416                 mmap_flags = MAP_PRIVATE;
 417         } else {
 418                 mmap_prot = PROT_READ | PROT_WRITE;
 419                 mmap_flags = MAP_SHARED;
 420         }
 421         ret = para_open(path, open_mode, 0);
 422         if (ret < 0)
 423                 return ret;
 424         fd = ret;
 425         if (fstat(fd, &file_status) < 0) {
 426                 ret = -ERRNO_TO_PARA_ERROR(errno);
 427                 goto out;
 428         }
 429         *size = file_status.st_size;
 430         ret = para_mmap(*size, mmap_prot, mmap_flags, fd, 0, map);
 431 out:
 432         if (ret < 0 || !fd_ptr)
 433                 close(fd);
 434         else
 435                 *fd_ptr = fd;
 436         return ret;
 437 }
 438
 439 /**
 440  * A wrapper for munmap(2).
 441  *
 442  * \param start The start address of the memory mapping.
 443  * \param length The size of the mapping.
 444  *
 445  * \return Standard.
 446  *
 447  * \sa munmap(2), mmap_full_file().
 448  */
 449 int para_munmap(void *start, size_t length)
 450 {
 451         int err;
 452         if (munmap(start, length) >= 0)
 453                 return 1;
 454         err = errno;
 455         PARA_ERROR_LOG("munmap (%p/%zu) failed: %s\n", start, length,
 456                 strerror(err));
 457         return -ERRNO_TO_PARA_ERROR(err);
 458 }
 459
 460 /**
 461  * Check a file descriptor for writability.
 462  *
 463  * \param fd The file descriptor.
 464  *
 465  * \return positive if fd is ready for writing, zero if it isn't, negative if
 466  * an error occurred.
 467  */
 468
 469 int write_ok(int fd)
 470 {
 471         struct timeval tv;
 472         fd_set wfds;
 473
 474         FD_ZERO(&wfds);
 475         FD_SET(fd, &wfds);
 476         tv.tv_sec = 0;
 477         tv.tv_usec = 0;
 478         return para_select(fd + 1, NULL, &wfds, &tv);
 479 }
 480
 481 /**
 482  * Ensure that file descriptors 0, 1, and 2 are valid.
 483  *
 484  * Common approach that opens /dev/null until it gets a file descriptor greater
 485  * than two.
 486  *
 487  * \sa okir's Black Hats Manual.
 488  */
 489 void valid_fd_012(void)
 490 {
 491         while (1) {
 492                 int fd = open("/dev/null", O_RDWR);
 493                 if (fd < 0)
 494                         exit(EXIT_FAILURE);
 495                 if (fd > 2) {
 496                         close(fd);
 497                         break;
 498                 }
 499         }
 500 }
 501
 502 /**
 503  * Traverse the given directory recursively.
 504  *
 505  * \param dirname The directory to traverse.
 506  * \param func The function to call for each entry.
 507  * \param private_data Pointer to an arbitrary data structure.
 508  *
 509  * For each regular file under \a dirname, the supplied function \a func is
 510  * called.  The full path of the regular file and the \a private_data pointer
 511  * are passed to \a func. Directories for which the calling process has no
 512  * permissions to change to are silently ignored.
 513  *
 514  * \return Standard.
 515  */
 516 int for_each_file_in_dir(const char *dirname,
 517                 int (*func)(const char *, void *), void *private_data)
 518 {
 519         DIR *dir;
 520         struct dirent *entry;
 521         int cwd_fd, ret2, ret = para_opendir(dirname, &dir, &cwd_fd);
 522
 523         if (ret < 0)
 524                 return ret == -ERRNO_TO_PARA_ERROR(EACCES)? 1 : ret;
 525         /* scan cwd recursively */
 526         while ((entry = readdir(dir))) {
 527                 mode_t m;
 528                 char *tmp;
 529                 struct stat s;
 530
 531                 if (!strcmp(entry->d_name, "."))
 532                         continue;
 533                 if (!strcmp(entry->d_name, ".."))
 534                         continue;
 535                 if (lstat(entry->d_name, &s) == -1)
 536                         continue;
 537                 m = s.st_mode;
 538                 if (!S_ISREG(m) && !S_ISDIR(m))
 539                         continue;
 540                 tmp = make_message("%s/%s", dirname, entry->d_name);
 541                 if (!S_ISDIR(m)) {
 542                         ret = func(tmp, private_data);
 543                         free(tmp);
 544                         if (ret < 0)
 545                                 goto out;
 546                         continue;
 547                 }
 548                 /* directory */
 549                 ret = for_each_file_in_dir(tmp, func, private_data);
 550                 free(tmp);
 551                 if (ret < 0)
 552                         goto out;
 553         }
 554         ret = 1;
 555 out:
 556         closedir(dir);
 557         ret2 = para_fchdir(cwd_fd);
 558         if (ret2 < 0 && ret >= 0)
 559                 ret = ret2;
 560         close(cwd_fd);
 561         return ret;
 562 }