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 #include <sys/uio.h>
  16
  17 #include "para.h"
  18 #include "error.h"
  19 #include "string.h"
  20
  21 /**
  22  * Write a buffer to a file descriptor, re-write on short writes.
  23  *
  24  * \param fd The file descriptor.
  25  * \param buf The buffer to be sent.
  26  * \param len The length of \a buf.
  27  *
  28  * \return Standard. In any case, the number of bytes that have been written is
  29  * stored in \a len.
  30  */
  31 int write_all(int fd, const char *buf, size_t *len)
  32 {
  33         size_t total = *len;
  34
  35         assert(total);
  36         *len = 0;
  37         while (*len < total) {
  38                 int ret = write(fd, buf + *len, total - *len);
  39                 if (ret == -1)
  40                         return -ERRNO_TO_PARA_ERROR(errno);
  41                 *len += ret;
  42         }
  43         return 1;
  44 }
  45
  46 /**
  47  * Write a buffer to a non-blocking file descriptor.
  48  *
  49  * \param fd The file descriptor.
  50  * \param buf the buffer to write.
  51  * \param len the number of bytes of \a buf.
  52  * \param max_bytes_per_write Do not write more than that many bytes at once.
  53  *
  54  * If \a max_bytes_per_write is non-zero, do not send more than that many bytes
  55  * per write().
  56  *
  57  * EAGAIN is not considered an error condition.  For example CCID3 has a
  58  * sending wait queue which fills up and is emptied asynchronously. The EAGAIN
  59  * case means that there is currently no space in the wait queue, but this can
  60  * change at any moment.
  61  *
  62  * \return Negative on errors, number of bytes written else.
  63  */
  64 int write_nonblock(int fd, const char *buf, size_t len,
  65                 size_t max_bytes_per_write)
  66 {
  67         size_t written = 0;
  68         int ret = 0;
  69
  70         while (written < len) {
  71                 size_t num = len - written;
  72
  73                 if (max_bytes_per_write && max_bytes_per_write < num)
  74                         num = max_bytes_per_write;
  75                 ret = write(fd, buf + written, num);
  76                 if (ret < 0 && errno == EAGAIN)
  77                         return written;
  78                 if (ret < 0)
  79                         return -ERRNO_TO_PARA_ERROR(errno);
  80                 written += ret;
  81         }
  82         return written;
  83 }
  84
  85 /**
  86  * Simple wrapper for readv().
  87  *
  88  * \param fd The file descriptor to read from.
  89  * \param iov Scatter/gather array used in readv().
  90  * \param iovcnt Number of elements in \a iov.
  91  *
  92  * \return A negative error code on errors, the return value of the underlying
  93  * call to readv() otherwise.
  94  *
  95  * \sa readv(2).
  96  */
  97 int para_readv(int fd, struct iovec *iov, int iovcnt)
  98 {
  99         int ret = readv(fd, iov, iovcnt);
 100
 101         if (ret < 0)
 102                 return -ERRNO_TO_PARA_ERROR(errno);
 103         return ret;
 104 }
 105
 106 /**
 107  * Check whether a file exists.
 108  *
 109  * \param fn The file name.
 110  *
 111  * \return Non-zero iff file exists.
 112  */
 113 int file_exists(const char *fn)
 114 {
 115         struct stat statbuf;
 116
 117         return !stat(fn, &statbuf);
 118 }
 119
 120 /**
 121  * Paraslash's wrapper for select(2).
 122  *
 123  * It calls select(2) (with no exceptfds) and starts over if select() was
 124  * interrupted by a signal.
 125  *
 126  * \param n The highest-numbered descriptor in any of the two sets, plus 1.
 127  * \param readfds fds that should be checked for readability.
 128  * \param writefds fds that should be checked for writablility.
 129  * \param timeout_tv upper bound on the amount of time elapsed before select()
 130  * returns.
 131  *
 132  * \return The return value of the underlying select() call on success, the
 133  * negative system error code on errors.
 134  *
 135  * All arguments are passed verbatim to select(2).
 136  * \sa select(2) select_tut(2).
 137  */
 138 int para_select(int n, fd_set *readfds, fd_set *writefds,
 139                 struct timeval *timeout_tv)
 140 {
 141         int ret;
 142         do
 143                 ret = select(n, readfds, writefds, NULL, timeout_tv);
 144         while (ret < 0 && errno == EINTR);
 145         if (ret < 0)
 146                 return -ERRNO_TO_PARA_ERROR(errno);
 147         return ret;
 148 }
 149
 150 /**
 151  * Set a file descriptor to blocking mode.
 152  *
 153  * \param fd The file descriptor.
 154  *
 155  * \return Standard.
 156  */
 157 __must_check int mark_fd_blocking(int fd)
 158 {
 159         int flags = fcntl(fd, F_GETFL);
 160         if (flags < 0)
 161                 return -ERRNO_TO_PARA_ERROR(errno);
 162         flags = fcntl(fd, F_SETFL, ((long)flags) & ~O_NONBLOCK);
 163         if (flags < 0)
 164                 return -ERRNO_TO_PARA_ERROR(errno);
 165         return 1;
 166 }
 167
 168 /**
 169  * Set a file descriptor to non-blocking mode.
 170  *
 171  * \param fd The file descriptor.
 172  *
 173  * \return Standard.
 174  */
 175 __must_check int mark_fd_nonblocking(int fd)
 176 {
 177         int flags = fcntl(fd, F_GETFL);
 178         if (flags < 0)
 179                 return -ERRNO_TO_PARA_ERROR(errno);
 180         flags = fcntl(fd, F_SETFL, ((long)flags) | O_NONBLOCK);
 181         if (flags < 0)
 182                 return -ERRNO_TO_PARA_ERROR(errno);
 183         return 1;
 184 }
 185
 186 /**
 187  * Set a file descriptor in a fd_set.
 188  *
 189  * \param fd The file descriptor to be set.
 190  * \param fds The file descriptor set.
 191  * \param max_fileno Highest-numbered file descriptor.
 192  *
 193  * This wrapper for FD_SET() passes its first two arguments to \p FD_SET. Upon
 194  * return, \a max_fileno contains the maximum of the old_value and \a fd.
 195  *
 196  * \sa para_select.
 197 */
 198 void para_fd_set(int fd, fd_set *fds, int *max_fileno)
 199 {
 200         assert(fd >= 0 && fd < FD_SETSIZE);
 201 #if 0
 202         {
 203                 int flags = fcntl(fd, F_GETFL);
 204                 if (!(flags & O_NONBLOCK)) {
 205                         PARA_EMERG_LOG("fd %d is a blocking file descriptor\n", fd);
 206                         exit(EXIT_FAILURE);
 207                 }
 208         }
 209 #endif
 210         FD_SET(fd, fds);
 211         *max_fileno = PARA_MAX(*max_fileno, fd);
 212 }
 213
 214 /**
 215  * Paraslash's wrapper for fgets(3).
 216  *
 217  * \param line Pointer to the buffer to store the line.
 218  * \param size The size of the buffer given by \a line.
 219  * \param f The stream to read from.
 220  *
 221  * \return Unlike the standard fgets() function, an integer value
 222  * is returned. On success, this function returns 1. On errors, -E_FGETS
 223  * is returned. A zero return value indicates an end of file condition.
 224  */
 225 __must_check int para_fgets(char *line, int size, FILE *f)
 226 {
 227 again:
 228         if (fgets(line, size, f))
 229                 return 1;
 230         if (feof(f))
 231                 return 0;
 232         if (!ferror(f))
 233                 return -E_FGETS;
 234         if (errno != EINTR) {
 235                 PARA_ERROR_LOG("%s\n", strerror(errno));
 236                 return -E_FGETS;
 237         }
 238         clearerr(f);
 239         goto again;
 240 }
 241
 242 /**
 243  * Paraslash's wrapper for mmap.
 244  *
 245  * \param length Number of bytes to mmap.
 246  * \param prot Either PROT_NONE or the bitwise OR of one or more of
 247  * PROT_EXEC PROT_READ PROT_WRITE.
 248  * \param flags Exactly one of MAP_SHARED and MAP_PRIVATE.
 249  * \param fd The file to mmap from.
 250  * \param offset Mmap start.
 251  * \param map Result pointer.
 252  *
 253  * \return Standard.
 254  *
 255  * \sa mmap(2).
 256  */
 257 int para_mmap(size_t length, int prot, int flags, int fd, off_t offset,
 258                 void *map)
 259 {
 260         void **m = map;
 261
 262         errno = EINVAL;
 263         if (!length)
 264                 goto err;
 265         *m = mmap(NULL, length, prot, flags, fd, offset);
 266         if (*m != MAP_FAILED)
 267                 return 1;
 268 err:
 269         *m = NULL;
 270         return -ERRNO_TO_PARA_ERROR(errno);
 271 }
 272
 273 /**
 274  * Wrapper for the open(2) system call.
 275  *
 276  * \param path The filename.
 277  * \param flags The usual open(2) flags.
 278  * \param mode Specifies the permissions to use.
 279  *
 280  * The mode parameter must be specified when O_CREAT is in the flags, and is
 281  * ignored otherwise.
 282  *
 283  * \return The file descriptor on success, negative on errors.
 284  *
 285  * \sa open(2).
 286  */
 287 int para_open(const char *path, int flags, mode_t mode)
 288 {
 289         int ret = open(path, flags, mode);
 290
 291         if (ret >= 0)
 292                 return ret;
 293         return -ERRNO_TO_PARA_ERROR(errno);
 294 }
 295
 296 /**
 297  * Wrapper for chdir(2).
 298  *
 299  * \param path The specified directory.
 300  *
 301  * \return Standard.
 302  */
 303 int para_chdir(const char *path)
 304 {
 305         int ret = chdir(path);
 306
 307         if (ret >= 0)
 308                 return 1;
 309         return -ERRNO_TO_PARA_ERROR(errno);
 310 }
 311
 312 /**
 313  * Save the cwd and open a given directory.
 314  *
 315  * \param dirname Path to the directory to open.
 316  * \param dir Result pointer.
 317  * \param cwd File descriptor of the current working directory.
 318  *
 319  * \return Standard.
 320  *
 321  * Opening the current directory (".") and calling fchdir() to return is
 322  * usually faster and more reliable than saving cwd in some buffer and calling
 323  * chdir() afterwards.
 324  *
 325  * If \a cwd is not \p NULL "." is opened and the resulting file descriptor is
 326  * stored in \a cwd. If the function returns success, and \a cwd is not \p
 327  * NULL, the caller must close this file descriptor (probably after calling
 328  * fchdir(*cwd)).
 329  *
 330  * On errors, the function undos everything, so the caller needs neither close
 331  * any files, nor change back to the original working directory.
 332  *
 333  * \sa getcwd(3).
 334  *
 335  */
 336 int para_opendir(const char *dirname, DIR **dir, int *cwd)
 337 {
 338         int ret;
 339
 340         if (cwd) {
 341                 ret = para_open(".", O_RDONLY, 0);
 342                 if (ret < 0)
 343                         return ret;
 344                 *cwd = ret;
 345         }
 346         ret = para_chdir(dirname);
 347         if (ret < 0)
 348                 goto close_cwd;
 349         *dir = opendir(".");
 350         if (*dir)
 351                 return 1;
 352         ret = -ERRNO_TO_PARA_ERROR(errno);
 353         /* Ignore return value of fchdir() and close(). We're busted anyway. */
 354         if (cwd) {
 355                 int __a_unused ret2 = fchdir(*cwd); /* STFU, gcc */
 356         }
 357 close_cwd:
 358         if (cwd)
 359                 close(*cwd);
 360         return ret;
 361 }
 362
 363 /**
 364  * A wrapper for fchdir().
 365  *
 366  * \param fd An open file descriptor.
 367  *
 368  * \return Standard.
 369  */
 370 int para_fchdir(int fd)
 371 {
 372         if (fchdir(fd) < 0)
 373                 return -ERRNO_TO_PARA_ERROR(errno);
 374         return 1;
 375 }
 376
 377 /**
 378  * A wrapper for mkdir(2).
 379  *
 380  * \param path Name of the directory to create.
 381  * \param mode The permissions to use.
 382  *
 383  * \return Standard.
 384  */
 385 int para_mkdir(const char *path, mode_t mode)
 386 {
 387         if (!mkdir(path, mode))
 388                 return 1;
 389         return -ERRNO_TO_PARA_ERROR(errno);
 390 }
 391
 392 /**
 393  * Open a file and map it into memory.
 394  *
 395  * \param path Name of the regular file to map.
 396  * \param open_mode Either \p O_RDONLY or \p O_RDWR.
 397  * \param map On success, the mapping is returned here.
 398  * \param size size of the mapping.
 399  * \param fd_ptr The file descriptor of the mapping.
 400  *
 401  * If \a fd_ptr is \p NULL, the file descriptor resulting from the underlying
 402  * open call is closed after mmap().  Otherwise the file is kept open and the
 403  * file descriptor is returned in \a fd_ptr.
 404  *
 405  * \return Standard.
 406  *
 407  * \sa para_open(), mmap(2).
 408  */
 409 int mmap_full_file(const char *path, int open_mode, void **map,
 410                 size_t *size, int *fd_ptr)
 411 {
 412         int fd, ret, mmap_prot, mmap_flags;
 413         struct stat file_status;
 414
 415         if (open_mode == O_RDONLY) {
 416                 mmap_prot = PROT_READ;
 417                 mmap_flags = MAP_PRIVATE;
 418         } else {
 419                 mmap_prot = PROT_READ | PROT_WRITE;
 420                 mmap_flags = MAP_SHARED;
 421         }
 422         ret = para_open(path, open_mode, 0);
 423         if (ret < 0)
 424                 return ret;
 425         fd = ret;
 426         if (fstat(fd, &file_status) < 0) {
 427                 ret = -ERRNO_TO_PARA_ERROR(errno);
 428                 goto out;
 429         }
 430         *size = file_status.st_size;
 431         ret = para_mmap(*size, mmap_prot, mmap_flags, fd, 0, map);
 432 out:
 433         if (ret < 0 || !fd_ptr)
 434                 close(fd);
 435         else
 436                 *fd_ptr = fd;
 437         return ret;
 438 }
 439
 440 /**
 441  * A wrapper for munmap(2).
 442  *
 443  * \param start The start address of the memory mapping.
 444  * \param length The size of the mapping.
 445  *
 446  * \return Standard.
 447  *
 448  * \sa munmap(2), mmap_full_file().
 449  */
 450 int para_munmap(void *start, size_t length)
 451 {
 452         int err;
 453         if (munmap(start, length) >= 0)
 454                 return 1;
 455         err = errno;
 456         PARA_ERROR_LOG("munmap (%p/%zu) failed: %s\n", start, length,
 457                 strerror(err));
 458         return -ERRNO_TO_PARA_ERROR(err);
 459 }
 460
 461 /**
 462  * Check a file descriptor for writability.
 463  *
 464  * \param fd The file descriptor.
 465  *
 466  * \return positive if fd is ready for writing, zero if it isn't, negative if
 467  * an error occurred.
 468  */
 469
 470 int write_ok(int fd)
 471 {
 472         struct timeval tv;
 473         fd_set wfds;
 474
 475         FD_ZERO(&wfds);
 476         FD_SET(fd, &wfds);
 477         tv.tv_sec = 0;
 478         tv.tv_usec = 0;
 479         return para_select(fd + 1, NULL, &wfds, &tv);
 480 }
 481
 482 /**
 483  * Ensure that file descriptors 0, 1, and 2 are valid.
 484  *
 485  * Common approach that opens /dev/null until it gets a file descriptor greater
 486  * than two.
 487  *
 488  * \sa okir's Black Hats Manual.
 489  */
 490 void valid_fd_012(void)
 491 {
 492         while (1) {
 493                 int fd = open("/dev/null", O_RDWR);
 494                 if (fd < 0)
 495                         exit(EXIT_FAILURE);
 496                 if (fd > 2) {
 497                         close(fd);
 498                         break;
 499                 }
 500         }
 501 }
 502
 503 /**
 504  * Traverse the given directory recursively.
 505  *
 506  * \param dirname The directory to traverse.
 507  * \param func The function to call for each entry.
 508  * \param private_data Pointer to an arbitrary data structure.
 509  *
 510  * For each regular file under \a dirname, the supplied function \a func is
 511  * called.  The full path of the regular file and the \a private_data pointer
 512  * are passed to \a func. Directories for which the calling process has no
 513  * permissions to change to are silently ignored.
 514  *
 515  * \return Standard.
 516  */
 517 int for_each_file_in_dir(const char *dirname,
 518                 int (*func)(const char *, void *), void *private_data)
 519 {
 520         DIR *dir;
 521         struct dirent *entry;
 522         int cwd_fd, ret2, ret = para_opendir(dirname, &dir, &cwd_fd);
 523
 524         if (ret < 0)
 525                 return ret == -ERRNO_TO_PARA_ERROR(EACCES)? 1 : ret;
 526         /* scan cwd recursively */
 527         while ((entry = readdir(dir))) {
 528                 mode_t m;
 529                 char *tmp;
 530                 struct stat s;
 531
 532                 if (!strcmp(entry->d_name, "."))
 533                         continue;
 534                 if (!strcmp(entry->d_name, ".."))
 535                         continue;
 536                 if (lstat(entry->d_name, &s) == -1)
 537                         continue;
 538                 m = s.st_mode;
 539                 if (!S_ISREG(m) && !S_ISDIR(m))
 540                         continue;
 541                 tmp = make_message("%s/%s", dirname, entry->d_name);
 542                 if (!S_ISDIR(m)) {
 543                         ret = func(tmp, private_data);
 544                         free(tmp);
 545                         if (ret < 0)
 546                                 goto out;
 547                         continue;
 548                 }
 549                 /* directory */
 550                 ret = for_each_file_in_dir(tmp, func, private_data);
 551                 free(tmp);
 552                 if (ret < 0)
 553                         goto out;
 554         }
 555         ret = 1;
 556 out:
 557         closedir(dir);
 558         ret2 = para_fchdir(cwd_fd);
 559         if (ret2 < 0 && ret >= 0)
 560                 ret = ret2;
 561         close(cwd_fd);
 562         return ret;
 563 }