| 1 | /* Low-level file-handling. |
| 2 | Copyright (C) 2012-2016 Free Software Foundation, Inc. |
| 3 | |
| 4 | This file is part of GDB. |
| 5 | |
| 6 | This program is free software; you can redistribute it and/or modify |
| 7 | it under the terms of the GNU General Public License as published by |
| 8 | the Free Software Foundation; either version 3 of the License, or |
| 9 | (at your option) any later version. |
| 10 | |
| 11 | This program is distributed in the hope that it will be useful, |
| 12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 14 | GNU General Public License for more details. |
| 15 | |
| 16 | You should have received a copy of the GNU General Public License |
| 17 | along with this program. If not, see <http://www.gnu.org/licenses/>. */ |
| 18 | |
| 19 | #include "common-defs.h" |
| 20 | #include "filestuff.h" |
| 21 | #include "gdb_vecs.h" |
| 22 | #include <fcntl.h> |
| 23 | #include <unistd.h> |
| 24 | #include <sys/types.h> |
| 25 | #include <sys/stat.h> |
| 26 | |
| 27 | #ifdef USE_WIN32API |
| 28 | #include <winsock2.h> |
| 29 | #include <windows.h> |
| 30 | #define HAVE_SOCKETS 1 |
| 31 | #elif defined HAVE_SYS_SOCKET_H |
| 32 | #include <sys/socket.h> |
| 33 | /* Define HAVE_F_GETFD if we plan to use F_GETFD. */ |
| 34 | #define HAVE_F_GETFD F_GETFD |
| 35 | #define HAVE_SOCKETS 1 |
| 36 | #endif |
| 37 | |
| 38 | #ifdef HAVE_SYS_RESOURCE_H |
| 39 | #include <sys/resource.h> |
| 40 | #endif /* HAVE_SYS_RESOURCE_H */ |
| 41 | |
| 42 | #ifndef O_CLOEXEC |
| 43 | #define O_CLOEXEC 0 |
| 44 | #endif |
| 45 | |
| 46 | #ifndef SOCK_CLOEXEC |
| 47 | #define SOCK_CLOEXEC 0 |
| 48 | #endif |
| 49 | |
| 50 | \f |
| 51 | |
| 52 | #ifndef HAVE_FDWALK |
| 53 | |
| 54 | #include <dirent.h> |
| 55 | |
| 56 | /* Replacement for fdwalk, if the system doesn't define it. Walks all |
| 57 | open file descriptors (though this implementation may walk closed |
| 58 | ones as well, depending on the host platform's capabilities) and |
| 59 | call FUNC with ARG. If FUNC returns non-zero, stops immediately |
| 60 | and returns the same value. Otherwise, returns zero when |
| 61 | finished. */ |
| 62 | |
| 63 | static int |
| 64 | fdwalk (int (*func) (void *, int), void *arg) |
| 65 | { |
| 66 | /* Checking __linux__ isn't great but it isn't clear what would be |
| 67 | better. There doesn't seem to be a good way to check for this in |
| 68 | configure. */ |
| 69 | #ifdef __linux__ |
| 70 | DIR *dir; |
| 71 | |
| 72 | dir = opendir ("/proc/self/fd"); |
| 73 | if (dir != NULL) |
| 74 | { |
| 75 | struct dirent *entry; |
| 76 | int result = 0; |
| 77 | |
| 78 | for (entry = readdir (dir); entry != NULL; entry = readdir (dir)) |
| 79 | { |
| 80 | long fd; |
| 81 | char *tail; |
| 82 | int result; |
| 83 | |
| 84 | errno = 0; |
| 85 | fd = strtol (entry->d_name, &tail, 10); |
| 86 | if (*tail != '\0' || errno != 0) |
| 87 | continue; |
| 88 | if ((int) fd != fd) |
| 89 | { |
| 90 | /* What can we do here really? */ |
| 91 | continue; |
| 92 | } |
| 93 | |
| 94 | if (fd == dirfd (dir)) |
| 95 | continue; |
| 96 | |
| 97 | result = func (arg, fd); |
| 98 | if (result != 0) |
| 99 | break; |
| 100 | } |
| 101 | |
| 102 | closedir (dir); |
| 103 | return result; |
| 104 | } |
| 105 | /* We may fall through to the next case. */ |
| 106 | #endif |
| 107 | |
| 108 | { |
| 109 | int max, fd; |
| 110 | |
| 111 | #if defined(HAVE_GETRLIMIT) && defined(RLIMIT_NOFILE) |
| 112 | struct rlimit rlim; |
| 113 | |
| 114 | if (getrlimit (RLIMIT_NOFILE, &rlim) == 0 && rlim.rlim_max != RLIM_INFINITY) |
| 115 | max = rlim.rlim_max; |
| 116 | else |
| 117 | #endif |
| 118 | { |
| 119 | #ifdef _SC_OPEN_MAX |
| 120 | max = sysconf (_SC_OPEN_MAX); |
| 121 | #else |
| 122 | /* Whoops. */ |
| 123 | return 0; |
| 124 | #endif /* _SC_OPEN_MAX */ |
| 125 | } |
| 126 | |
| 127 | for (fd = 0; fd < max; ++fd) |
| 128 | { |
| 129 | struct stat sb; |
| 130 | int result; |
| 131 | |
| 132 | /* Only call FUNC for open fds. */ |
| 133 | if (fstat (fd, &sb) == -1) |
| 134 | continue; |
| 135 | |
| 136 | result = func (arg, fd); |
| 137 | if (result != 0) |
| 138 | return result; |
| 139 | } |
| 140 | |
| 141 | return 0; |
| 142 | } |
| 143 | } |
| 144 | |
| 145 | #endif /* HAVE_FDWALK */ |
| 146 | |
| 147 | \f |
| 148 | |
| 149 | /* A VEC holding all the fds open when notice_open_fds was called. We |
| 150 | don't use a hashtab because libiberty isn't linked into gdbserver; |
| 151 | and anyway we don't expect there to be many open fds. */ |
| 152 | |
| 153 | static VEC (int) *open_fds; |
| 154 | |
| 155 | /* An fdwalk callback function used by notice_open_fds. It puts the |
| 156 | given file descriptor into the vec. */ |
| 157 | |
| 158 | static int |
| 159 | do_mark_open_fd (void *ignore, int fd) |
| 160 | { |
| 161 | VEC_safe_push (int, open_fds, fd); |
| 162 | return 0; |
| 163 | } |
| 164 | |
| 165 | /* See filestuff.h. */ |
| 166 | |
| 167 | void |
| 168 | notice_open_fds (void) |
| 169 | { |
| 170 | fdwalk (do_mark_open_fd, NULL); |
| 171 | } |
| 172 | |
| 173 | /* See filestuff.h. */ |
| 174 | |
| 175 | void |
| 176 | mark_fd_no_cloexec (int fd) |
| 177 | { |
| 178 | do_mark_open_fd (NULL, fd); |
| 179 | } |
| 180 | |
| 181 | /* See filestuff.h. */ |
| 182 | |
| 183 | void |
| 184 | unmark_fd_no_cloexec (int fd) |
| 185 | { |
| 186 | int i, val; |
| 187 | |
| 188 | for (i = 0; VEC_iterate (int, open_fds, i, val); ++i) |
| 189 | { |
| 190 | if (fd == val) |
| 191 | { |
| 192 | VEC_unordered_remove (int, open_fds, i); |
| 193 | return; |
| 194 | } |
| 195 | } |
| 196 | |
| 197 | gdb_assert_not_reached (_("fd not found in open_fds")); |
| 198 | } |
| 199 | |
| 200 | /* Helper function for close_most_fds that closes the file descriptor |
| 201 | if appropriate. */ |
| 202 | |
| 203 | static int |
| 204 | do_close (void *ignore, int fd) |
| 205 | { |
| 206 | int i, val; |
| 207 | |
| 208 | for (i = 0; VEC_iterate (int, open_fds, i, val); ++i) |
| 209 | { |
| 210 | if (fd == val) |
| 211 | { |
| 212 | /* Keep this one open. */ |
| 213 | return 0; |
| 214 | } |
| 215 | } |
| 216 | |
| 217 | close (fd); |
| 218 | return 0; |
| 219 | } |
| 220 | |
| 221 | /* See filestuff.h. */ |
| 222 | |
| 223 | void |
| 224 | close_most_fds (void) |
| 225 | { |
| 226 | fdwalk (do_close, NULL); |
| 227 | } |
| 228 | |
| 229 | \f |
| 230 | |
| 231 | /* This is a tri-state flag. When zero it means we haven't yet tried |
| 232 | O_CLOEXEC. When positive it means that O_CLOEXEC works on this |
| 233 | host. When negative, it means that O_CLOEXEC doesn't work. We |
| 234 | track this state because, while gdb might have been compiled |
| 235 | against a libc that supplies O_CLOEXEC, there is no guarantee that |
| 236 | the kernel supports it. */ |
| 237 | |
| 238 | static int trust_o_cloexec; |
| 239 | |
| 240 | /* Mark FD as close-on-exec, ignoring errors. Update |
| 241 | TRUST_O_CLOEXEC. */ |
| 242 | |
| 243 | static void |
| 244 | mark_cloexec (int fd) |
| 245 | { |
| 246 | #ifdef HAVE_F_GETFD |
| 247 | int old = fcntl (fd, F_GETFD, 0); |
| 248 | |
| 249 | if (old != -1) |
| 250 | { |
| 251 | fcntl (fd, F_SETFD, old | FD_CLOEXEC); |
| 252 | |
| 253 | if (trust_o_cloexec == 0) |
| 254 | { |
| 255 | if ((old & FD_CLOEXEC) != 0) |
| 256 | trust_o_cloexec = 1; |
| 257 | else |
| 258 | trust_o_cloexec = -1; |
| 259 | } |
| 260 | } |
| 261 | #endif /* HAVE_F_GETFD */ |
| 262 | } |
| 263 | |
| 264 | /* Depending on TRUST_O_CLOEXEC, mark FD as close-on-exec. */ |
| 265 | |
| 266 | static void |
| 267 | maybe_mark_cloexec (int fd) |
| 268 | { |
| 269 | if (trust_o_cloexec <= 0) |
| 270 | mark_cloexec (fd); |
| 271 | } |
| 272 | |
| 273 | #ifdef HAVE_SOCKETS |
| 274 | |
| 275 | /* Like maybe_mark_cloexec, but for callers that use SOCK_CLOEXEC. */ |
| 276 | |
| 277 | static void |
| 278 | socket_mark_cloexec (int fd) |
| 279 | { |
| 280 | if (SOCK_CLOEXEC == 0 || trust_o_cloexec <= 0) |
| 281 | mark_cloexec (fd); |
| 282 | } |
| 283 | |
| 284 | #endif |
| 285 | |
| 286 | \f |
| 287 | |
| 288 | /* See filestuff.h. */ |
| 289 | |
| 290 | int |
| 291 | gdb_open_cloexec (const char *filename, int flags, unsigned long mode) |
| 292 | { |
| 293 | int fd = open (filename, flags | O_CLOEXEC, mode); |
| 294 | |
| 295 | if (fd >= 0) |
| 296 | maybe_mark_cloexec (fd); |
| 297 | |
| 298 | return fd; |
| 299 | } |
| 300 | |
| 301 | /* See filestuff.h. */ |
| 302 | |
| 303 | FILE * |
| 304 | gdb_fopen_cloexec (const char *filename, const char *opentype) |
| 305 | { |
| 306 | FILE *result; |
| 307 | /* Probe for "e" support once. But, if we can tell the operating |
| 308 | system doesn't know about close on exec mode "e" without probing, |
| 309 | skip it. E.g., the Windows runtime issues an "Invalid parameter |
| 310 | passed to C runtime function" OutputDebugString warning for |
| 311 | unknown modes. Assume that if O_CLOEXEC is zero, then "e" isn't |
| 312 | supported. */ |
| 313 | static int fopen_e_ever_failed_einval = O_CLOEXEC == 0; |
| 314 | |
| 315 | if (!fopen_e_ever_failed_einval) |
| 316 | { |
| 317 | char *copy; |
| 318 | |
| 319 | copy = (char *) alloca (strlen (opentype) + 2); |
| 320 | strcpy (copy, opentype); |
| 321 | /* This is a glibc extension but we try it unconditionally on |
| 322 | this path. */ |
| 323 | strcat (copy, "e"); |
| 324 | result = fopen (filename, copy); |
| 325 | |
| 326 | if (result == NULL && errno == EINVAL) |
| 327 | { |
| 328 | result = fopen (filename, opentype); |
| 329 | if (result != NULL) |
| 330 | fopen_e_ever_failed_einval = 1; |
| 331 | } |
| 332 | } |
| 333 | else |
| 334 | result = fopen (filename, opentype); |
| 335 | |
| 336 | if (result != NULL) |
| 337 | maybe_mark_cloexec (fileno (result)); |
| 338 | |
| 339 | return result; |
| 340 | } |
| 341 | |
| 342 | #ifdef HAVE_SOCKETS |
| 343 | /* See filestuff.h. */ |
| 344 | |
| 345 | int |
| 346 | gdb_socketpair_cloexec (int domain, int style, int protocol, |
| 347 | int filedes[2]) |
| 348 | { |
| 349 | #ifdef HAVE_SOCKETPAIR |
| 350 | int result = socketpair (domain, style | SOCK_CLOEXEC, protocol, filedes); |
| 351 | |
| 352 | if (result != -1) |
| 353 | { |
| 354 | socket_mark_cloexec (filedes[0]); |
| 355 | socket_mark_cloexec (filedes[1]); |
| 356 | } |
| 357 | |
| 358 | return result; |
| 359 | #else |
| 360 | gdb_assert_not_reached (_("socketpair not available on this host")); |
| 361 | #endif |
| 362 | } |
| 363 | |
| 364 | /* See filestuff.h. */ |
| 365 | |
| 366 | int |
| 367 | gdb_socket_cloexec (int domain, int style, int protocol) |
| 368 | { |
| 369 | int result = socket (domain, style | SOCK_CLOEXEC, protocol); |
| 370 | |
| 371 | if (result != -1) |
| 372 | socket_mark_cloexec (result); |
| 373 | |
| 374 | return result; |
| 375 | } |
| 376 | #endif |
| 377 | |
| 378 | /* See filestuff.h. */ |
| 379 | |
| 380 | int |
| 381 | gdb_pipe_cloexec (int filedes[2]) |
| 382 | { |
| 383 | int result; |
| 384 | |
| 385 | #ifdef HAVE_PIPE2 |
| 386 | result = pipe2 (filedes, O_CLOEXEC); |
| 387 | if (result != -1) |
| 388 | { |
| 389 | maybe_mark_cloexec (filedes[0]); |
| 390 | maybe_mark_cloexec (filedes[1]); |
| 391 | } |
| 392 | #else |
| 393 | #ifdef HAVE_PIPE |
| 394 | result = pipe (filedes); |
| 395 | if (result != -1) |
| 396 | { |
| 397 | mark_cloexec (filedes[0]); |
| 398 | mark_cloexec (filedes[1]); |
| 399 | } |
| 400 | #else /* HAVE_PIPE */ |
| 401 | gdb_assert_not_reached (_("pipe not available on this host")); |
| 402 | #endif /* HAVE_PIPE */ |
| 403 | #endif /* HAVE_PIPE2 */ |
| 404 | |
| 405 | return result; |
| 406 | } |
| 407 | |
| 408 | /* Helper function which does the work for make_cleanup_close. */ |
| 409 | |
| 410 | static void |
| 411 | do_close_cleanup (void *arg) |
| 412 | { |
| 413 | int *fd = (int *) arg; |
| 414 | |
| 415 | close (*fd); |
| 416 | } |
| 417 | |
| 418 | /* See filestuff.h. */ |
| 419 | |
| 420 | struct cleanup * |
| 421 | make_cleanup_close (int fd) |
| 422 | { |
| 423 | int *saved_fd = XNEW (int); |
| 424 | |
| 425 | *saved_fd = fd; |
| 426 | return make_cleanup_dtor (do_close_cleanup, saved_fd, xfree); |
| 427 | } |