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bd99dc85 | 1 | /* Event loop machinery for the remote server for GDB. |
4c38e0a4 | 2 | Copyright (C) 1999, 2000, 2001, 2002, 2005, 2006, 2007, 2008, 2010 |
bd99dc85 PA |
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 | ||
e9464885 DE |
37 | #ifdef HAVE_UNISTD_H |
38 | #include <unistd.h> | |
39 | #endif | |
40 | ||
bd99dc85 PA |
41 | typedef struct gdb_event gdb_event; |
42 | typedef void (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 | (*proc) (fd); | |
215 | return 1; | |
216 | } | |
217 | ||
218 | /* This is the case if there are no event on the event queue. */ | |
219 | return 0; | |
220 | } | |
221 | ||
222 | /* Add a file handler/descriptor to the list of descriptors we are | |
223 | interested in. FD is the file descriptor for the file/stream to be | |
224 | listened to. MASK is a combination of READABLE, WRITABLE, | |
225 | EXCEPTION. PROC is the procedure that will be called when an event | |
226 | occurs for FD. CLIENT_DATA is the argument to pass to PROC. */ | |
227 | ||
228 | static void | |
229 | create_file_handler (int fd, int mask, handler_func *proc, | |
230 | gdb_client_data client_data) | |
231 | { | |
232 | file_handler *file_ptr; | |
233 | ||
234 | /* Do we already have a file handler for this file? (We may be | |
235 | changing its associated procedure). */ | |
236 | for (file_ptr = gdb_notifier.first_file_handler; | |
237 | file_ptr != NULL; | |
238 | file_ptr = file_ptr->next_file) | |
239 | if (file_ptr->fd == fd) | |
240 | break; | |
241 | ||
242 | /* It is a new file descriptor. Add it to the list. Otherwise, | |
243 | just change the data associated with it. */ | |
244 | if (file_ptr == NULL) | |
245 | { | |
246 | file_ptr = xmalloc (sizeof (*file_ptr)); | |
247 | file_ptr->fd = fd; | |
248 | file_ptr->ready_mask = 0; | |
249 | file_ptr->next_file = gdb_notifier.first_file_handler; | |
250 | gdb_notifier.first_file_handler = file_ptr; | |
251 | ||
252 | if (mask & GDB_READABLE) | |
253 | FD_SET (fd, &gdb_notifier.check_masks[0]); | |
254 | else | |
255 | FD_CLR (fd, &gdb_notifier.check_masks[0]); | |
256 | ||
257 | if (mask & GDB_WRITABLE) | |
258 | FD_SET (fd, &gdb_notifier.check_masks[1]); | |
259 | else | |
260 | FD_CLR (fd, &gdb_notifier.check_masks[1]); | |
261 | ||
262 | if (mask & GDB_EXCEPTION) | |
263 | FD_SET (fd, &gdb_notifier.check_masks[2]); | |
264 | else | |
265 | FD_CLR (fd, &gdb_notifier.check_masks[2]); | |
266 | ||
267 | if (gdb_notifier.num_fds <= fd) | |
268 | gdb_notifier.num_fds = fd + 1; | |
269 | } | |
270 | ||
271 | file_ptr->proc = proc; | |
272 | file_ptr->client_data = client_data; | |
273 | file_ptr->mask = mask; | |
274 | } | |
275 | ||
276 | /* Wrapper function for create_file_handler. */ | |
277 | ||
278 | void | |
279 | add_file_handler (int fd, handler_func *proc, gdb_client_data client_data) | |
280 | { | |
281 | create_file_handler (fd, GDB_READABLE | GDB_EXCEPTION, proc, client_data); | |
282 | } | |
283 | ||
284 | /* Remove the file descriptor FD from the list of monitored fd's: | |
285 | i.e. we don't care anymore about events on the FD. */ | |
286 | ||
287 | void | |
288 | delete_file_handler (int fd) | |
289 | { | |
290 | file_handler *file_ptr, *prev_ptr = NULL; | |
291 | int i; | |
292 | ||
293 | /* Find the entry for the given file. */ | |
294 | ||
295 | for (file_ptr = gdb_notifier.first_file_handler; | |
296 | file_ptr != NULL; | |
297 | file_ptr = file_ptr->next_file) | |
298 | if (file_ptr->fd == fd) | |
299 | break; | |
300 | ||
301 | if (file_ptr == NULL) | |
302 | return; | |
303 | ||
304 | if (file_ptr->mask & GDB_READABLE) | |
305 | FD_CLR (fd, &gdb_notifier.check_masks[0]); | |
306 | if (file_ptr->mask & GDB_WRITABLE) | |
307 | FD_CLR (fd, &gdb_notifier.check_masks[1]); | |
308 | if (file_ptr->mask & GDB_EXCEPTION) | |
309 | FD_CLR (fd, &gdb_notifier.check_masks[2]); | |
310 | ||
311 | /* Find current max fd. */ | |
312 | ||
313 | if ((fd + 1) == gdb_notifier.num_fds) | |
314 | { | |
315 | gdb_notifier.num_fds--; | |
316 | for (i = gdb_notifier.num_fds; i; i--) | |
317 | { | |
318 | if (FD_ISSET (i - 1, &gdb_notifier.check_masks[0]) | |
319 | || FD_ISSET (i - 1, &gdb_notifier.check_masks[1]) | |
320 | || FD_ISSET (i - 1, &gdb_notifier.check_masks[2])) | |
321 | break; | |
322 | } | |
323 | gdb_notifier.num_fds = i; | |
324 | } | |
325 | ||
326 | /* Deactivate the file descriptor, by clearing its mask, so that it | |
327 | will not fire again. */ | |
328 | ||
329 | file_ptr->mask = 0; | |
330 | ||
331 | /* Get rid of the file handler in the file handler list. */ | |
332 | if (file_ptr == gdb_notifier.first_file_handler) | |
333 | gdb_notifier.first_file_handler = file_ptr->next_file; | |
334 | else | |
335 | { | |
336 | for (prev_ptr = gdb_notifier.first_file_handler; | |
337 | prev_ptr->next_file != file_ptr; | |
338 | prev_ptr = prev_ptr->next_file) | |
339 | ; | |
340 | prev_ptr->next_file = file_ptr->next_file; | |
341 | } | |
342 | free (file_ptr); | |
343 | } | |
344 | ||
345 | /* Handle the given event by calling the procedure associated to the | |
346 | corresponding file handler. Called by process_event indirectly, | |
347 | through event_ptr->proc. EVENT_FILE_DESC is file descriptor of the | |
348 | event in the front of the event queue. */ | |
349 | ||
350 | static void | |
351 | handle_file_event (int event_file_desc) | |
352 | { | |
353 | file_handler *file_ptr; | |
354 | int mask; | |
355 | ||
356 | /* Search the file handler list to find one that matches the fd in | |
357 | the event. */ | |
358 | for (file_ptr = gdb_notifier.first_file_handler; file_ptr != NULL; | |
359 | file_ptr = file_ptr->next_file) | |
360 | { | |
361 | if (file_ptr->fd == event_file_desc) | |
362 | { | |
363 | /* See if the desired events (mask) match the received | |
364 | events (ready_mask). */ | |
365 | ||
366 | if (file_ptr->ready_mask & GDB_EXCEPTION) | |
367 | { | |
368 | fprintf (stderr, "Exception condition detected on fd %d\n", | |
369 | file_ptr->fd); | |
370 | file_ptr->error = 1; | |
371 | } | |
372 | else | |
373 | file_ptr->error = 0; | |
374 | mask = file_ptr->ready_mask & file_ptr->mask; | |
375 | ||
376 | /* Clear the received events for next time around. */ | |
377 | file_ptr->ready_mask = 0; | |
378 | ||
379 | /* If there was a match, then call the handler. */ | |
380 | if (mask != 0) | |
381 | (*file_ptr->proc) (file_ptr->error, file_ptr->client_data); | |
382 | break; | |
383 | } | |
384 | } | |
385 | } | |
386 | ||
387 | /* Create a file event, to be enqueued in the event queue for | |
388 | processing. The procedure associated to this event is always | |
389 | handle_file_event, which will in turn invoke the one that was | |
390 | associated to FD when it was registered with the event loop. */ | |
391 | ||
392 | static gdb_event * | |
393 | create_file_event (int fd) | |
394 | { | |
395 | gdb_event *file_event_ptr; | |
396 | ||
397 | file_event_ptr = xmalloc (sizeof (gdb_event)); | |
398 | file_event_ptr->proc = handle_file_event; | |
399 | file_event_ptr->fd = fd; | |
400 | return file_event_ptr; | |
401 | } | |
402 | ||
403 | /* Called by do_one_event to wait for new events on the monitored file | |
404 | descriptors. Queue file events as they are detected by the poll. | |
405 | If there are no events, this function will block in the call to | |
406 | select. Return -1 if there are no files descriptors to monitor, | |
407 | otherwise return 0. */ | |
408 | ||
409 | static int | |
410 | wait_for_event (void) | |
411 | { | |
412 | file_handler *file_ptr; | |
413 | gdb_event *file_event_ptr; | |
414 | int num_found = 0; | |
415 | ||
416 | /* Make sure all output is done before getting another event. */ | |
417 | fflush (stdout); | |
418 | fflush (stderr); | |
419 | ||
420 | if (gdb_notifier.num_fds == 0) | |
421 | return -1; | |
422 | ||
423 | gdb_notifier.ready_masks[0] = gdb_notifier.check_masks[0]; | |
424 | gdb_notifier.ready_masks[1] = gdb_notifier.check_masks[1]; | |
425 | gdb_notifier.ready_masks[2] = gdb_notifier.check_masks[2]; | |
426 | num_found = select (gdb_notifier.num_fds, | |
427 | &gdb_notifier.ready_masks[0], | |
428 | &gdb_notifier.ready_masks[1], | |
429 | &gdb_notifier.ready_masks[2], | |
430 | NULL); | |
431 | ||
432 | /* Clear the masks after an error from select. */ | |
433 | if (num_found == -1) | |
434 | { | |
435 | FD_ZERO (&gdb_notifier.ready_masks[0]); | |
436 | FD_ZERO (&gdb_notifier.ready_masks[1]); | |
437 | FD_ZERO (&gdb_notifier.ready_masks[2]); | |
438 | #ifdef EINTR | |
439 | /* Dont print anything if we got a signal, let gdb handle | |
440 | it. */ | |
441 | if (errno != EINTR) | |
442 | perror_with_name ("select"); | |
443 | #endif | |
444 | } | |
445 | ||
446 | /* Enqueue all detected file events. */ | |
447 | ||
448 | for (file_ptr = gdb_notifier.first_file_handler; | |
449 | file_ptr != NULL && num_found > 0; | |
450 | file_ptr = file_ptr->next_file) | |
451 | { | |
452 | int mask = 0; | |
453 | ||
454 | if (FD_ISSET (file_ptr->fd, &gdb_notifier.ready_masks[0])) | |
455 | mask |= GDB_READABLE; | |
456 | if (FD_ISSET (file_ptr->fd, &gdb_notifier.ready_masks[1])) | |
457 | mask |= GDB_WRITABLE; | |
458 | if (FD_ISSET (file_ptr->fd, &gdb_notifier.ready_masks[2])) | |
459 | mask |= GDB_EXCEPTION; | |
460 | ||
461 | if (!mask) | |
462 | continue; | |
463 | else | |
464 | num_found--; | |
465 | ||
466 | /* Enqueue an event only if this is still a new event for this | |
467 | fd. */ | |
468 | ||
469 | if (file_ptr->ready_mask == 0) | |
470 | { | |
471 | file_event_ptr = create_file_event (file_ptr->fd); | |
472 | async_queue_event (file_event_ptr); | |
473 | } | |
474 | file_ptr->ready_mask = mask; | |
475 | } | |
476 | ||
477 | return 0; | |
478 | } | |
479 | ||
480 | /* Start up the event loop. This is the entry point to the event | |
481 | loop. */ | |
482 | ||
483 | void | |
484 | start_event_loop (void) | |
485 | { | |
486 | /* Loop until there is nothing to do. This is the entry point to | |
487 | the event loop engine. If nothing is ready at this time, wait | |
488 | for something to happen (via wait_for_event), then process it. | |
489 | Return when there are no longer event sources to wait for. */ | |
490 | ||
491 | while (1) | |
492 | { | |
493 | /* Any events already waiting in the queue? */ | |
494 | if (process_event ()) | |
495 | continue; | |
496 | ||
497 | /* Wait for a new event. If wait_for_event returns -1, we | |
498 | should get out because this means that there are no event | |
499 | sources left. This will make the event loop stop, and the | |
500 | application exit. */ | |
501 | ||
502 | if (wait_for_event () < 0) | |
503 | return; | |
504 | } | |
505 | ||
506 | /* We are done with the event loop. There are no more event sources | |
507 | to listen to. So we exit gdbserver. */ | |
508 | } |