| 1 | /* Event loop machinery for the remote server for GDB. |
| 2 | Copyright (C) 1999, 2000, 2001, 2002, 2005, 2006, 2007, 2008, 2010 |
| 3 | Free Software Foundation, Inc. |
| 4 | |
| 5 | This file is part of GDB. |
| 6 | |
| 7 | This program is free software; you can redistribute it and/or modify |
| 8 | it under the terms of the GNU General Public License as published by |
| 9 | the Free Software Foundation; either version 3 of the License, or |
| 10 | (at your option) any later version. |
| 11 | |
| 12 | This program is distributed in the hope that it will be useful, |
| 13 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 15 | GNU General Public License for more details. |
| 16 | |
| 17 | You should have received a copy of the GNU General Public License |
| 18 | along with this program. If not, see <http://www.gnu.org/licenses/>. */ |
| 19 | |
| 20 | /* Based on src/gdb/event-loop.c. */ |
| 21 | |
| 22 | #include "server.h" |
| 23 | |
| 24 | #include <sys/types.h> |
| 25 | #include <string.h> |
| 26 | #include <sys/time.h> |
| 27 | |
| 28 | #ifdef USE_WIN32API |
| 29 | #include <windows.h> |
| 30 | #include <io.h> |
| 31 | #endif |
| 32 | |
| 33 | #ifdef HAVE_ERRNO_H |
| 34 | #include <errno.h> |
| 35 | #endif |
| 36 | |
| 37 | #ifdef HAVE_UNISTD_H |
| 38 | #include <unistd.h> |
| 39 | #endif |
| 40 | |
| 41 | typedef struct gdb_event gdb_event; |
| 42 | typedef int (event_handler_func) (int); |
| 43 | |
| 44 | /* Tell create_file_handler what events we are interested in. */ |
| 45 | |
| 46 | #define GDB_READABLE (1<<1) |
| 47 | #define GDB_WRITABLE (1<<2) |
| 48 | #define GDB_EXCEPTION (1<<3) |
| 49 | |
| 50 | /* Events are queued by calling async_queue_event and serviced later |
| 51 | on by do_one_event. An event can be, for instance, a file |
| 52 | descriptor becoming ready to be read. Servicing an event simply |
| 53 | means that the procedure PROC will be called. We have 2 queues, |
| 54 | one for file handlers that we listen to in the event loop, and one |
| 55 | for the file handlers+events that are ready. The procedure PROC |
| 56 | associated with each event is always the same (handle_file_event). |
| 57 | Its duty is to invoke the handler associated with the file |
| 58 | descriptor whose state change generated the event, plus doing other |
| 59 | cleanups and such. */ |
| 60 | |
| 61 | struct gdb_event |
| 62 | { |
| 63 | /* Procedure to call to service this event. */ |
| 64 | event_handler_func *proc; |
| 65 | |
| 66 | /* File descriptor that is ready. */ |
| 67 | int fd; |
| 68 | |
| 69 | /* Next in list of events or NULL. */ |
| 70 | struct gdb_event *next_event; |
| 71 | }; |
| 72 | |
| 73 | /* Information about each file descriptor we register with the event |
| 74 | loop. */ |
| 75 | |
| 76 | typedef struct file_handler |
| 77 | { |
| 78 | /* File descriptor. */ |
| 79 | int fd; |
| 80 | |
| 81 | /* Events we want to monitor. */ |
| 82 | int mask; |
| 83 | |
| 84 | /* Events that have been seen since the last time. */ |
| 85 | int ready_mask; |
| 86 | |
| 87 | /* Procedure to call when fd is ready. */ |
| 88 | handler_func *proc; |
| 89 | |
| 90 | /* Argument to pass to proc. */ |
| 91 | gdb_client_data client_data; |
| 92 | |
| 93 | /* Was an error detected on this fd? */ |
| 94 | int error; |
| 95 | |
| 96 | /* Next registered file descriptor. */ |
| 97 | struct file_handler *next_file; |
| 98 | } |
| 99 | file_handler; |
| 100 | |
| 101 | /* Event queue: |
| 102 | |
| 103 | Events can be inserted at the front of the queue or at the end of |
| 104 | the queue. Events will be extracted from the queue for processing |
| 105 | starting from the head. Therefore, events inserted at the head of |
| 106 | the queue will be processed in a last in first out fashion, while |
| 107 | those inserted at the tail of the queue will be processed in a |
| 108 | first in first out manner. All the fields are NULL if the queue is |
| 109 | empty. */ |
| 110 | |
| 111 | static struct |
| 112 | { |
| 113 | /* The first pending event. */ |
| 114 | gdb_event *first_event; |
| 115 | |
| 116 | /* The last pending event. */ |
| 117 | gdb_event *last_event; |
| 118 | } |
| 119 | event_queue; |
| 120 | |
| 121 | /* Gdb_notifier is just a list of file descriptors gdb is interested |
| 122 | in. These are the input file descriptor, and the target file |
| 123 | descriptor. Each of the elements in the gdb_notifier list is |
| 124 | basically a description of what kind of events gdb is interested |
| 125 | in, for each fd. */ |
| 126 | |
| 127 | static struct |
| 128 | { |
| 129 | /* Ptr to head of file handler list. */ |
| 130 | file_handler *first_file_handler; |
| 131 | |
| 132 | /* Masks to be used in the next call to select. Bits are set in |
| 133 | response to calls to create_file_handler. */ |
| 134 | fd_set check_masks[3]; |
| 135 | |
| 136 | /* What file descriptors were found ready by select. */ |
| 137 | fd_set ready_masks[3]; |
| 138 | |
| 139 | /* Number of valid bits (highest fd value + 1). (for select) */ |
| 140 | int num_fds; |
| 141 | } |
| 142 | gdb_notifier; |
| 143 | |
| 144 | /* Insert an event object into the gdb event queue. |
| 145 | |
| 146 | EVENT_PTR points to the event to be inserted into the queue. The |
| 147 | caller must allocate memory for the event. It is freed after the |
| 148 | event has ben handled. Events in the queue will be processed head |
| 149 | to tail, therefore, events will be processed first in first |
| 150 | out. */ |
| 151 | |
| 152 | static void |
| 153 | async_queue_event (gdb_event *event_ptr) |
| 154 | { |
| 155 | /* The event will become the new last_event. */ |
| 156 | |
| 157 | event_ptr->next_event = NULL; |
| 158 | if (event_queue.first_event == NULL) |
| 159 | event_queue.first_event = event_ptr; |
| 160 | else |
| 161 | event_queue.last_event->next_event = event_ptr; |
| 162 | event_queue.last_event = event_ptr; |
| 163 | } |
| 164 | |
| 165 | /* Process one event. If an event was processed, 1 is returned |
| 166 | otherwise 0 is returned. Scan the queue from head to tail, |
| 167 | processing therefore the high priority events first, by invoking |
| 168 | the associated event handler procedure. */ |
| 169 | |
| 170 | static int |
| 171 | process_event (void) |
| 172 | { |
| 173 | gdb_event *event_ptr, *prev_ptr; |
| 174 | event_handler_func *proc; |
| 175 | int fd; |
| 176 | |
| 177 | /* Look in the event queue to find an event that is ready |
| 178 | to be processed. */ |
| 179 | |
| 180 | for (event_ptr = event_queue.first_event; |
| 181 | event_ptr != NULL; |
| 182 | event_ptr = event_ptr->next_event) |
| 183 | { |
| 184 | /* Call the handler for the event. */ |
| 185 | |
| 186 | proc = event_ptr->proc; |
| 187 | fd = event_ptr->fd; |
| 188 | |
| 189 | /* Let's get rid of the event from the event queue. We need to |
| 190 | do this now because while processing the event, since the |
| 191 | proc function could end up jumping out to the caller of this |
| 192 | function. In that case, we would have on the event queue an |
| 193 | event which has been processed, but not deleted. */ |
| 194 | |
| 195 | if (event_queue.first_event == event_ptr) |
| 196 | { |
| 197 | event_queue.first_event = event_ptr->next_event; |
| 198 | if (event_ptr->next_event == NULL) |
| 199 | event_queue.last_event = NULL; |
| 200 | } |
| 201 | else |
| 202 | { |
| 203 | prev_ptr = event_queue.first_event; |
| 204 | while (prev_ptr->next_event != event_ptr) |
| 205 | prev_ptr = prev_ptr->next_event; |
| 206 | |
| 207 | prev_ptr->next_event = event_ptr->next_event; |
| 208 | if (event_ptr->next_event == NULL) |
| 209 | event_queue.last_event = prev_ptr; |
| 210 | } |
| 211 | free (event_ptr); |
| 212 | |
| 213 | /* Now call the procedure associated with the event. */ |
| 214 | if ((*proc) (fd)) |
| 215 | return -1; |
| 216 | return 1; |
| 217 | } |
| 218 | |
| 219 | /* This is the case if there are no event on the event queue. */ |
| 220 | return 0; |
| 221 | } |
| 222 | |
| 223 | /* Add a file handler/descriptor to the list of descriptors we are |
| 224 | interested in. FD is the file descriptor for the file/stream to be |
| 225 | listened to. MASK is a combination of READABLE, WRITABLE, |
| 226 | EXCEPTION. PROC is the procedure that will be called when an event |
| 227 | occurs for FD. CLIENT_DATA is the argument to pass to PROC. */ |
| 228 | |
| 229 | static void |
| 230 | create_file_handler (int fd, int mask, handler_func *proc, |
| 231 | gdb_client_data client_data) |
| 232 | { |
| 233 | file_handler *file_ptr; |
| 234 | |
| 235 | /* Do we already have a file handler for this file? (We may be |
| 236 | changing its associated procedure). */ |
| 237 | for (file_ptr = gdb_notifier.first_file_handler; |
| 238 | file_ptr != NULL; |
| 239 | file_ptr = file_ptr->next_file) |
| 240 | if (file_ptr->fd == fd) |
| 241 | break; |
| 242 | |
| 243 | /* It is a new file descriptor. Add it to the list. Otherwise, |
| 244 | just change the data associated with it. */ |
| 245 | if (file_ptr == NULL) |
| 246 | { |
| 247 | file_ptr = xmalloc (sizeof (*file_ptr)); |
| 248 | file_ptr->fd = fd; |
| 249 | file_ptr->ready_mask = 0; |
| 250 | file_ptr->next_file = gdb_notifier.first_file_handler; |
| 251 | gdb_notifier.first_file_handler = file_ptr; |
| 252 | |
| 253 | if (mask & GDB_READABLE) |
| 254 | FD_SET (fd, &gdb_notifier.check_masks[0]); |
| 255 | else |
| 256 | FD_CLR (fd, &gdb_notifier.check_masks[0]); |
| 257 | |
| 258 | if (mask & GDB_WRITABLE) |
| 259 | FD_SET (fd, &gdb_notifier.check_masks[1]); |
| 260 | else |
| 261 | FD_CLR (fd, &gdb_notifier.check_masks[1]); |
| 262 | |
| 263 | if (mask & GDB_EXCEPTION) |
| 264 | FD_SET (fd, &gdb_notifier.check_masks[2]); |
| 265 | else |
| 266 | FD_CLR (fd, &gdb_notifier.check_masks[2]); |
| 267 | |
| 268 | if (gdb_notifier.num_fds <= fd) |
| 269 | gdb_notifier.num_fds = fd + 1; |
| 270 | } |
| 271 | |
| 272 | file_ptr->proc = proc; |
| 273 | file_ptr->client_data = client_data; |
| 274 | file_ptr->mask = mask; |
| 275 | } |
| 276 | |
| 277 | /* Wrapper function for create_file_handler. */ |
| 278 | |
| 279 | void |
| 280 | add_file_handler (int fd, handler_func *proc, gdb_client_data client_data) |
| 281 | { |
| 282 | create_file_handler (fd, GDB_READABLE | GDB_EXCEPTION, proc, client_data); |
| 283 | } |
| 284 | |
| 285 | /* Remove the file descriptor FD from the list of monitored fd's: |
| 286 | i.e. we don't care anymore about events on the FD. */ |
| 287 | |
| 288 | void |
| 289 | delete_file_handler (int fd) |
| 290 | { |
| 291 | file_handler *file_ptr, *prev_ptr = NULL; |
| 292 | int i; |
| 293 | |
| 294 | /* Find the entry for the given file. */ |
| 295 | |
| 296 | for (file_ptr = gdb_notifier.first_file_handler; |
| 297 | file_ptr != NULL; |
| 298 | file_ptr = file_ptr->next_file) |
| 299 | if (file_ptr->fd == fd) |
| 300 | break; |
| 301 | |
| 302 | if (file_ptr == NULL) |
| 303 | return; |
| 304 | |
| 305 | if (file_ptr->mask & GDB_READABLE) |
| 306 | FD_CLR (fd, &gdb_notifier.check_masks[0]); |
| 307 | if (file_ptr->mask & GDB_WRITABLE) |
| 308 | FD_CLR (fd, &gdb_notifier.check_masks[1]); |
| 309 | if (file_ptr->mask & GDB_EXCEPTION) |
| 310 | FD_CLR (fd, &gdb_notifier.check_masks[2]); |
| 311 | |
| 312 | /* Find current max fd. */ |
| 313 | |
| 314 | if ((fd + 1) == gdb_notifier.num_fds) |
| 315 | { |
| 316 | gdb_notifier.num_fds--; |
| 317 | for (i = gdb_notifier.num_fds; i; i--) |
| 318 | { |
| 319 | if (FD_ISSET (i - 1, &gdb_notifier.check_masks[0]) |
| 320 | || FD_ISSET (i - 1, &gdb_notifier.check_masks[1]) |
| 321 | || FD_ISSET (i - 1, &gdb_notifier.check_masks[2])) |
| 322 | break; |
| 323 | } |
| 324 | gdb_notifier.num_fds = i; |
| 325 | } |
| 326 | |
| 327 | /* Deactivate the file descriptor, by clearing its mask, so that it |
| 328 | will not fire again. */ |
| 329 | |
| 330 | file_ptr->mask = 0; |
| 331 | |
| 332 | /* Get rid of the file handler in the file handler list. */ |
| 333 | if (file_ptr == gdb_notifier.first_file_handler) |
| 334 | gdb_notifier.first_file_handler = file_ptr->next_file; |
| 335 | else |
| 336 | { |
| 337 | for (prev_ptr = gdb_notifier.first_file_handler; |
| 338 | prev_ptr->next_file != file_ptr; |
| 339 | prev_ptr = prev_ptr->next_file) |
| 340 | ; |
| 341 | prev_ptr->next_file = file_ptr->next_file; |
| 342 | } |
| 343 | free (file_ptr); |
| 344 | } |
| 345 | |
| 346 | /* Handle the given event by calling the procedure associated to the |
| 347 | corresponding file handler. Called by process_event indirectly, |
| 348 | through event_ptr->proc. EVENT_FILE_DESC is file descriptor of the |
| 349 | event in the front of the event queue. */ |
| 350 | |
| 351 | static int |
| 352 | handle_file_event (int event_file_desc) |
| 353 | { |
| 354 | file_handler *file_ptr; |
| 355 | int mask; |
| 356 | |
| 357 | /* Search the file handler list to find one that matches the fd in |
| 358 | the event. */ |
| 359 | for (file_ptr = gdb_notifier.first_file_handler; file_ptr != NULL; |
| 360 | file_ptr = file_ptr->next_file) |
| 361 | { |
| 362 | if (file_ptr->fd == event_file_desc) |
| 363 | { |
| 364 | /* See if the desired events (mask) match the received |
| 365 | events (ready_mask). */ |
| 366 | |
| 367 | if (file_ptr->ready_mask & GDB_EXCEPTION) |
| 368 | { |
| 369 | fprintf (stderr, "Exception condition detected on fd %d\n", |
| 370 | file_ptr->fd); |
| 371 | file_ptr->error = 1; |
| 372 | } |
| 373 | else |
| 374 | file_ptr->error = 0; |
| 375 | mask = file_ptr->ready_mask & file_ptr->mask; |
| 376 | |
| 377 | /* Clear the received events for next time around. */ |
| 378 | file_ptr->ready_mask = 0; |
| 379 | |
| 380 | /* If there was a match, then call the handler. */ |
| 381 | if (mask != 0) |
| 382 | { |
| 383 | if ((*file_ptr->proc) (file_ptr->error, |
| 384 | file_ptr->client_data) < 0) |
| 385 | return -1; |
| 386 | } |
| 387 | break; |
| 388 | } |
| 389 | } |
| 390 | |
| 391 | return 0; |
| 392 | } |
| 393 | |
| 394 | /* Create a file event, to be enqueued in the event queue for |
| 395 | processing. The procedure associated to this event is always |
| 396 | handle_file_event, which will in turn invoke the one that was |
| 397 | associated to FD when it was registered with the event loop. */ |
| 398 | |
| 399 | static gdb_event * |
| 400 | create_file_event (int fd) |
| 401 | { |
| 402 | gdb_event *file_event_ptr; |
| 403 | |
| 404 | file_event_ptr = xmalloc (sizeof (gdb_event)); |
| 405 | file_event_ptr->proc = handle_file_event; |
| 406 | file_event_ptr->fd = fd; |
| 407 | return file_event_ptr; |
| 408 | } |
| 409 | |
| 410 | /* Called by do_one_event to wait for new events on the monitored file |
| 411 | descriptors. Queue file events as they are detected by the poll. |
| 412 | If there are no events, this function will block in the call to |
| 413 | select. Return -1 if there are no files descriptors to monitor, |
| 414 | otherwise return 0. */ |
| 415 | |
| 416 | static int |
| 417 | wait_for_event (void) |
| 418 | { |
| 419 | file_handler *file_ptr; |
| 420 | gdb_event *file_event_ptr; |
| 421 | int num_found = 0; |
| 422 | |
| 423 | /* Make sure all output is done before getting another event. */ |
| 424 | fflush (stdout); |
| 425 | fflush (stderr); |
| 426 | |
| 427 | if (gdb_notifier.num_fds == 0) |
| 428 | return -1; |
| 429 | |
| 430 | gdb_notifier.ready_masks[0] = gdb_notifier.check_masks[0]; |
| 431 | gdb_notifier.ready_masks[1] = gdb_notifier.check_masks[1]; |
| 432 | gdb_notifier.ready_masks[2] = gdb_notifier.check_masks[2]; |
| 433 | num_found = select (gdb_notifier.num_fds, |
| 434 | &gdb_notifier.ready_masks[0], |
| 435 | &gdb_notifier.ready_masks[1], |
| 436 | &gdb_notifier.ready_masks[2], |
| 437 | NULL); |
| 438 | |
| 439 | /* Clear the masks after an error from select. */ |
| 440 | if (num_found == -1) |
| 441 | { |
| 442 | FD_ZERO (&gdb_notifier.ready_masks[0]); |
| 443 | FD_ZERO (&gdb_notifier.ready_masks[1]); |
| 444 | FD_ZERO (&gdb_notifier.ready_masks[2]); |
| 445 | #ifdef EINTR |
| 446 | /* Dont print anything if we got a signal, let gdb handle |
| 447 | it. */ |
| 448 | if (errno != EINTR) |
| 449 | perror_with_name ("select"); |
| 450 | #endif |
| 451 | } |
| 452 | |
| 453 | /* Enqueue all detected file events. */ |
| 454 | |
| 455 | for (file_ptr = gdb_notifier.first_file_handler; |
| 456 | file_ptr != NULL && num_found > 0; |
| 457 | file_ptr = file_ptr->next_file) |
| 458 | { |
| 459 | int mask = 0; |
| 460 | |
| 461 | if (FD_ISSET (file_ptr->fd, &gdb_notifier.ready_masks[0])) |
| 462 | mask |= GDB_READABLE; |
| 463 | if (FD_ISSET (file_ptr->fd, &gdb_notifier.ready_masks[1])) |
| 464 | mask |= GDB_WRITABLE; |
| 465 | if (FD_ISSET (file_ptr->fd, &gdb_notifier.ready_masks[2])) |
| 466 | mask |= GDB_EXCEPTION; |
| 467 | |
| 468 | if (!mask) |
| 469 | continue; |
| 470 | else |
| 471 | num_found--; |
| 472 | |
| 473 | /* Enqueue an event only if this is still a new event for this |
| 474 | fd. */ |
| 475 | |
| 476 | if (file_ptr->ready_mask == 0) |
| 477 | { |
| 478 | file_event_ptr = create_file_event (file_ptr->fd); |
| 479 | async_queue_event (file_event_ptr); |
| 480 | } |
| 481 | file_ptr->ready_mask = mask; |
| 482 | } |
| 483 | |
| 484 | return 0; |
| 485 | } |
| 486 | |
| 487 | /* Start up the event loop. This is the entry point to the event |
| 488 | loop. */ |
| 489 | |
| 490 | void |
| 491 | start_event_loop (void) |
| 492 | { |
| 493 | /* Loop until there is nothing to do. This is the entry point to |
| 494 | the event loop engine. If nothing is ready at this time, wait |
| 495 | for something to happen (via wait_for_event), then process it. |
| 496 | Return when there are no longer event sources to wait for. */ |
| 497 | |
| 498 | while (1) |
| 499 | { |
| 500 | /* Any events already waiting in the queue? */ |
| 501 | int res = process_event (); |
| 502 | |
| 503 | /* Did the event handler want the event loop to stop? */ |
| 504 | if (res == -1) |
| 505 | return; |
| 506 | |
| 507 | if (res) |
| 508 | continue; |
| 509 | |
| 510 | /* Wait for a new event. If wait_for_event returns -1, we |
| 511 | should get out because this means that there are no event |
| 512 | sources left. This will make the event loop stop, and the |
| 513 | application exit. */ |
| 514 | |
| 515 | if (wait_for_event () < 0) |
| 516 | return; |
| 517 | } |
| 518 | |
| 519 | /* We are done with the event loop. There are no more event sources |
| 520 | to listen to. So we exit gdbserver. */ |
| 521 | } |