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c906108c | 1 | /* Fork a Unix child process, and set up to debug it, for GDB. |
b6ba6518 KB |
2 | Copyright 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000, |
3 | 2001 Free Software Foundation, Inc. | |
c906108c SS |
4 | Contributed by Cygnus Support. |
5 | ||
c5aa993b | 6 | This file is part of GDB. |
c906108c | 7 | |
c5aa993b JM |
8 | This program is free software; you can redistribute it and/or modify |
9 | it under the terms of the GNU General Public License as published by | |
10 | the Free Software Foundation; either version 2 of the License, or | |
11 | (at your option) any later version. | |
c906108c | 12 | |
c5aa993b JM |
13 | This program is distributed in the hope that it will be useful, |
14 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
16 | GNU General Public License for more details. | |
c906108c | 17 | |
c5aa993b JM |
18 | You should have received a copy of the GNU General Public License |
19 | along with this program; if not, write to the Free Software | |
20 | Foundation, Inc., 59 Temple Place - Suite 330, | |
21 | Boston, MA 02111-1307, USA. */ | |
c906108c SS |
22 | |
23 | #include "defs.h" | |
24 | #include "gdb_string.h" | |
25 | #include "frame.h" /* required by inferior.h */ | |
26 | #include "inferior.h" | |
27 | #include "target.h" | |
03f2053f | 28 | #include "gdb_wait.h" |
74c1b268 | 29 | #include "gdb_vfork.h" |
c906108c SS |
30 | #include "gdbcore.h" |
31 | #include "terminal.h" | |
32 | #include "gdbthread.h" | |
c2d11a7d | 33 | #include "command.h" /* for dont_repeat () */ |
c906108c SS |
34 | |
35 | #include <signal.h> | |
c906108c | 36 | |
c906108c SS |
37 | /* This just gets used as a default if we can't find SHELL */ |
38 | #ifndef SHELL_FILE | |
39 | #define SHELL_FILE "/bin/sh" | |
40 | #endif | |
41 | ||
42 | extern char **environ; | |
43 | ||
44 | /* This function breaks up an argument string into an argument | |
45 | * vector suitable for passing to execvp(). | |
46 | * E.g., on "run a b c d" this routine would get as input | |
47 | * the string "a b c d", and as output it would fill in argv with | |
48 | * the four arguments "a", "b", "c", "d". | |
49 | */ | |
50 | static void | |
fba45db2 | 51 | breakup_args (char *scratch, char **argv) |
c906108c SS |
52 | { |
53 | char *cp = scratch; | |
54 | ||
c906108c SS |
55 | for (;;) |
56 | { | |
57 | ||
58 | /* Scan past leading separators */ | |
59 | while (*cp == ' ' || *cp == '\t' || *cp == '\n') | |
60 | { | |
61 | cp++; | |
62 | } | |
63 | ||
64 | /* Break if at end of string */ | |
65 | if (*cp == '\0') | |
66 | break; | |
67 | ||
68 | /* Take an arg */ | |
69 | *argv++ = cp; | |
70 | ||
71 | /* Scan for next arg separator */ | |
72 | cp = strchr (cp, ' '); | |
73 | if (cp == NULL) | |
74 | cp = strchr (cp, '\t'); | |
75 | if (cp == NULL) | |
76 | cp = strchr (cp, '\n'); | |
77 | ||
78 | /* No separators => end of string => break */ | |
79 | if (cp == NULL) | |
80 | break; | |
81 | ||
82 | /* Replace the separator with a terminator */ | |
83 | *cp++ = '\0'; | |
84 | } | |
85 | ||
86 | /* execv requires a null-terminated arg vector */ | |
87 | *argv = NULL; | |
88 | ||
89 | } | |
90 | ||
91 | ||
92 | /* Start an inferior Unix child process and sets inferior_pid to its pid. | |
93 | EXEC_FILE is the file to run. | |
94 | ALLARGS is a string containing the arguments to the program. | |
95 | ENV is the environment vector to pass. SHELL_FILE is the shell file, | |
96 | or NULL if we should pick one. Errors reported with error(). */ | |
97 | ||
98 | void | |
073063d7 KB |
99 | fork_inferior (char *exec_file, char *allargs, char **env, |
100 | void (*traceme_fun) (void), void (*init_trace_fun) (int), | |
101 | void (*pre_trace_fun) (void), char *shell_file) | |
c906108c SS |
102 | { |
103 | int pid; | |
104 | char *shell_command; | |
105 | static char default_shell_file[] = SHELL_FILE; | |
106 | int len; | |
107 | /* Set debug_fork then attach to the child while it sleeps, to debug. */ | |
108 | static int debug_fork = 0; | |
109 | /* This is set to the result of setpgrp, which if vforked, will be visible | |
110 | to you in the parent process. It's only used by humans for debugging. */ | |
111 | static int debug_setpgrp = 657473; | |
112 | char **save_our_env; | |
113 | int shell = 0; | |
114 | char **argv; | |
c906108c SS |
115 | |
116 | /* If no exec file handed to us, get it from the exec-file command -- with | |
117 | a good, common error message if none is specified. */ | |
118 | if (exec_file == 0) | |
119 | exec_file = get_exec_file (1); | |
120 | ||
121 | /* STARTUP_WITH_SHELL is defined in inferior.h. | |
122 | * If 0, we'll just do a fork/exec, no shell, so don't | |
123 | * bother figuring out what shell. | |
124 | */ | |
125 | if (STARTUP_WITH_SHELL) | |
126 | { | |
127 | /* Figure out what shell to start up the user program under. */ | |
128 | if (shell_file == NULL) | |
129 | shell_file = getenv ("SHELL"); | |
130 | if (shell_file == NULL) | |
131 | shell_file = default_shell_file; | |
132 | shell = 1; | |
133 | } | |
134 | ||
c906108c SS |
135 | /* Multiplying the length of exec_file by 4 is to account for the fact |
136 | that it may expand when quoted; it is a worst-case number based on | |
137 | every character being '. */ | |
c5aa993b | 138 | len = 5 + 4 * strlen (exec_file) + 1 + strlen (allargs) + 1 + /*slop */ 12; |
c906108c SS |
139 | /* If desired, concat something onto the front of ALLARGS. |
140 | SHELL_COMMAND is the result. */ | |
141 | #ifdef SHELL_COMMAND_CONCAT | |
142 | shell_command = (char *) alloca (strlen (SHELL_COMMAND_CONCAT) + len); | |
143 | strcpy (shell_command, SHELL_COMMAND_CONCAT); | |
144 | #else | |
145 | shell_command = (char *) alloca (len); | |
146 | shell_command[0] = '\0'; | |
147 | #endif | |
148 | ||
149 | if (!shell) | |
150 | { | |
151 | /* We're going to call execvp. Create argv */ | |
152 | /* Largest case: every other character is a separate arg */ | |
c906108c SS |
153 | argv = (char **) xmalloc (((strlen (allargs) + 1) / (unsigned) 2 + 2) * sizeof (*argv)); |
154 | argv[0] = exec_file; | |
155 | breakup_args (allargs, &argv[1]); | |
156 | ||
157 | } | |
158 | else | |
159 | { | |
160 | ||
161 | /* We're going to call a shell */ | |
162 | ||
163 | /* Now add exec_file, quoting as necessary. */ | |
164 | ||
165 | char *p; | |
166 | int need_to_quote; | |
167 | ||
168 | strcat (shell_command, "exec "); | |
169 | ||
170 | /* Quoting in this style is said to work with all shells. But csh | |
c5aa993b JM |
171 | on IRIX 4.0.1 can't deal with it. So we only quote it if we need |
172 | to. */ | |
c906108c SS |
173 | p = exec_file; |
174 | while (1) | |
175 | { | |
176 | switch (*p) | |
177 | { | |
178 | case '\'': | |
179 | case '"': | |
180 | case '(': | |
181 | case ')': | |
182 | case '$': | |
183 | case '&': | |
184 | case ';': | |
185 | case '<': | |
186 | case '>': | |
187 | case ' ': | |
188 | case '\n': | |
189 | case '\t': | |
190 | need_to_quote = 1; | |
191 | goto end_scan; | |
192 | ||
193 | case '\0': | |
194 | need_to_quote = 0; | |
195 | goto end_scan; | |
196 | ||
197 | default: | |
198 | break; | |
199 | } | |
200 | ++p; | |
201 | } | |
202 | end_scan: | |
203 | if (need_to_quote) | |
204 | { | |
205 | strcat (shell_command, "'"); | |
206 | for (p = exec_file; *p != '\0'; ++p) | |
207 | { | |
208 | if (*p == '\'') | |
209 | strcat (shell_command, "'\\''"); | |
210 | else | |
211 | strncat (shell_command, p, 1); | |
212 | } | |
213 | strcat (shell_command, "'"); | |
214 | } | |
215 | else | |
216 | strcat (shell_command, exec_file); | |
217 | ||
218 | strcat (shell_command, " "); | |
219 | strcat (shell_command, allargs); | |
220 | ||
221 | } | |
222 | ||
223 | /* exec is said to fail if the executable is open. */ | |
224 | close_exec_file (); | |
225 | ||
226 | /* Retain a copy of our environment variables, since the child will | |
227 | replace the value of environ and if we're vforked, we have to | |
228 | restore it. */ | |
229 | save_our_env = environ; | |
230 | ||
231 | /* Tell the terminal handling subsystem what tty we plan to run on; | |
232 | it will just record the information for later. */ | |
233 | ||
234 | new_tty_prefork (inferior_io_terminal); | |
235 | ||
236 | /* It is generally good practice to flush any possible pending stdio | |
237 | output prior to doing a fork, to avoid the possibility of both the | |
238 | parent and child flushing the same data after the fork. */ | |
239 | ||
240 | gdb_flush (gdb_stdout); | |
241 | gdb_flush (gdb_stderr); | |
242 | ||
243 | /* If there's any initialization of the target layers that must happen | |
c5aa993b | 244 | to prepare to handle the child we're about fork, do it now... |
c906108c SS |
245 | */ |
246 | if (pre_trace_fun != NULL) | |
247 | (*pre_trace_fun) (); | |
248 | ||
c906108c SS |
249 | if (debug_fork) |
250 | pid = fork (); | |
251 | else | |
252 | pid = vfork (); | |
c906108c SS |
253 | |
254 | if (pid < 0) | |
255 | perror_with_name ("vfork"); | |
256 | ||
257 | if (pid == 0) | |
258 | { | |
259 | if (debug_fork) | |
260 | sleep (debug_fork); | |
261 | ||
262 | /* Run inferior in a separate process group. */ | |
263 | debug_setpgrp = gdb_setpgid (); | |
264 | if (debug_setpgrp == -1) | |
265 | perror ("setpgrp failed in child"); | |
266 | ||
267 | /* Ask the tty subsystem to switch to the one we specified earlier | |
c5aa993b | 268 | (or to share the current terminal, if none was specified). */ |
c906108c SS |
269 | |
270 | new_tty (); | |
271 | ||
272 | /* Changing the signal handlers for the inferior after | |
c5aa993b JM |
273 | a vfork can also change them for the superior, so we don't mess |
274 | with signals here. See comments in | |
275 | initialize_signals for how we get the right signal handlers | |
276 | for the inferior. */ | |
c906108c SS |
277 | |
278 | /* "Trace me, Dr. Memory!" */ | |
279 | (*traceme_fun) (); | |
280 | /* The call above set this process (the "child") as debuggable | |
281 | * by the original gdb process (the "parent"). Since processes | |
282 | * (unlike people) can have only one parent, if you are | |
283 | * debugging gdb itself (and your debugger is thus _already_ the | |
284 | * controller/parent for this child), code from here on out | |
285 | * is undebuggable. Indeed, you probably got an error message | |
286 | * saying "not parent". Sorry--you'll have to use print statements! | |
287 | */ | |
288 | ||
289 | /* There is no execlpe call, so we have to set the environment | |
c5aa993b JM |
290 | for our child in the global variable. If we've vforked, this |
291 | clobbers the parent, but environ is restored a few lines down | |
292 | in the parent. By the way, yes we do need to look down the | |
293 | path to find $SHELL. Rich Pixley says so, and I agree. */ | |
c906108c SS |
294 | environ = env; |
295 | ||
296 | /* If we decided above to start up with a shell, | |
297 | * we exec the shell, | |
298 | * "-c" says to interpret the next arg as a shell command | |
299 | * to execute, and this command is "exec <target-program> <args>". | |
300 | * "-f" means "fast startup" to the c-shell, which means | |
301 | * don't do .cshrc file. Doing .cshrc may cause fork/exec | |
302 | * events which will confuse debugger start-up code. | |
303 | */ | |
304 | if (shell) | |
305 | { | |
c906108c | 306 | execlp (shell_file, shell_file, "-c", shell_command, (char *) 0); |
c906108c SS |
307 | |
308 | /* If we get here, it's an error */ | |
309 | fprintf_unfiltered (gdb_stderr, "Cannot exec %s: %s.\n", shell_file, | |
310 | safe_strerror (errno)); | |
311 | gdb_flush (gdb_stderr); | |
312 | _exit (0177); | |
313 | } | |
314 | else | |
315 | { | |
316 | /* Otherwise, we directly exec the target program with execvp. */ | |
317 | int i; | |
318 | char *errstring; | |
cce74817 | 319 | |
c906108c SS |
320 | execvp (exec_file, argv); |
321 | ||
322 | /* If we get here, it's an error */ | |
323 | errstring = safe_strerror (errno); | |
324 | fprintf_unfiltered (gdb_stderr, "Cannot exec %s ", exec_file); | |
325 | ||
326 | i = 1; | |
327 | while (argv[i] != NULL) | |
328 | { | |
329 | if (i != 1) | |
330 | fprintf_unfiltered (gdb_stderr, " "); | |
331 | fprintf_unfiltered (gdb_stderr, "%s", argv[i]); | |
332 | i++; | |
333 | } | |
334 | fprintf_unfiltered (gdb_stderr, ".\n"); | |
335 | /* This extra info seems to be useless | |
c5aa993b JM |
336 | fprintf_unfiltered (gdb_stderr, "Got error %s.\n", errstring); |
337 | */ | |
c906108c SS |
338 | gdb_flush (gdb_stderr); |
339 | _exit (0177); | |
340 | } | |
341 | } | |
342 | ||
343 | /* Restore our environment in case a vforked child clob'd it. */ | |
344 | environ = save_our_env; | |
345 | ||
346 | init_thread_list (); | |
347 | ||
348 | inferior_pid = pid; /* Needed for wait_for_inferior stuff below */ | |
349 | ||
350 | /* Now that we have a child process, make it our target, and | |
351 | initialize anything target-vector-specific that needs initializing. */ | |
352 | ||
353 | (*init_trace_fun) (pid); | |
354 | ||
355 | /* We are now in the child process of interest, having exec'd the | |
356 | correct program, and are poised at the first instruction of the | |
357 | new program. */ | |
358 | ||
b7d6b182 | 359 | /* Allow target dependent code to play with the new process. This might be |
c906108c SS |
360 | used to have target-specific code initialize a variable in the new process |
361 | prior to executing the first instruction. */ | |
362 | TARGET_CREATE_INFERIOR_HOOK (pid); | |
363 | ||
364 | #ifdef SOLIB_CREATE_INFERIOR_HOOK | |
365 | SOLIB_CREATE_INFERIOR_HOOK (pid); | |
366 | #endif | |
367 | } | |
368 | ||
369 | /* An inferior Unix process CHILD_PID has been created by a call to | |
370 | fork() (or variants like vfork). It is presently stopped, and waiting | |
371 | to be resumed. clone_and_follow_inferior will fork the debugger, | |
372 | and that clone will "follow" (attach to) CHILD_PID. The original copy | |
373 | of the debugger will not touch CHILD_PID again. | |
374 | ||
375 | Also, the original debugger will set FOLLOWED_CHILD FALSE, while the | |
376 | clone will set it TRUE. | |
c5aa993b | 377 | */ |
c906108c | 378 | void |
fba45db2 | 379 | clone_and_follow_inferior (int child_pid, int *followed_child) |
c906108c SS |
380 | { |
381 | extern int auto_solib_add; | |
382 | ||
383 | int debugger_pid; | |
384 | int status; | |
385 | char pid_spelling[100]; /* Arbitrary but sufficient length. */ | |
386 | ||
387 | /* This semaphore is used to coordinate the two debuggers' handoff | |
388 | of CHILD_PID. The original debugger will detach from CHILD_PID, | |
389 | and then the clone debugger will attach to it. (It must be done | |
390 | this way because on some targets, only one process at a time can | |
391 | trace another. Thus, the original debugger must relinquish its | |
392 | tracing rights before the clone can pick them up.) | |
c5aa993b | 393 | */ |
c906108c SS |
394 | #define SEM_TALK (1) |
395 | #define SEM_LISTEN (0) | |
396 | int handoff_semaphore[2]; /* Original "talks" to [1], clone "listens" to [0] */ | |
397 | int talk_value = 99; | |
398 | int listen_value; | |
399 | ||
400 | /* Set debug_fork then attach to the child while it sleeps, to debug. */ | |
401 | static int debug_fork = 0; | |
402 | ||
403 | /* It is generally good practice to flush any possible pending stdio | |
404 | output prior to doing a fork, to avoid the possibility of both the | |
405 | parent and child flushing the same data after the fork. */ | |
406 | ||
407 | gdb_flush (gdb_stdout); | |
408 | gdb_flush (gdb_stderr); | |
409 | ||
410 | /* Open the semaphore pipes. | |
c5aa993b | 411 | */ |
c906108c SS |
412 | status = pipe (handoff_semaphore); |
413 | if (status < 0) | |
414 | error ("error getting pipe for handoff semaphore"); | |
415 | ||
416 | /* Clone the debugger. */ | |
818fa2bf | 417 | #ifdef HAVE_VFORK |
c906108c SS |
418 | if (debug_fork) |
419 | debugger_pid = fork (); | |
420 | else | |
421 | debugger_pid = vfork (); | |
818fa2bf AC |
422 | #else |
423 | debugger_pid = fork (); | |
c906108c SS |
424 | #endif |
425 | ||
426 | if (debugger_pid < 0) | |
427 | perror_with_name ("fork"); | |
428 | ||
429 | /* Are we the original debugger? If so, we must relinquish all claims | |
c5aa993b | 430 | to CHILD_PID. */ |
c906108c SS |
431 | if (debugger_pid != 0) |
432 | { | |
c5aa993b | 433 | char signal_spelling[100]; /* Arbitrary but sufficient length */ |
c906108c SS |
434 | |
435 | /* Detach from CHILD_PID. Deliver a "stop" signal when we do, though, | |
c5aa993b JM |
436 | so that it remains stopped until the clone debugger can attach |
437 | to it. | |
c906108c SS |
438 | */ |
439 | detach_breakpoints (child_pid); | |
440 | ||
441 | sprintf (signal_spelling, "%d", target_signal_to_host (TARGET_SIGNAL_STOP)); | |
442 | target_require_detach (child_pid, signal_spelling, 1); | |
443 | ||
444 | /* Notify the clone debugger that it should attach to CHILD_PID. */ | |
445 | write (handoff_semaphore[SEM_TALK], &talk_value, sizeof (talk_value)); | |
446 | ||
447 | *followed_child = 0; | |
448 | } | |
449 | ||
450 | /* We're the child. */ | |
451 | else | |
452 | { | |
453 | if (debug_fork) | |
454 | sleep (debug_fork); | |
455 | ||
456 | /* The child (i.e., the cloned debugger) must now attach to | |
457 | CHILD_PID. inferior_pid is presently set to the parent process | |
458 | of the fork, while CHILD_PID should be the child process of the | |
459 | fork. | |
460 | ||
461 | Wait until the original debugger relinquishes control of CHILD_PID, | |
462 | though. | |
c5aa993b | 463 | */ |
c906108c SS |
464 | read (handoff_semaphore[SEM_LISTEN], &listen_value, sizeof (listen_value)); |
465 | ||
466 | /* Note that we DON'T want to actually detach from inferior_pid, | |
467 | because that would allow it to run free. The original | |
468 | debugger wants to retain control of the process. So, we | |
469 | just reset inferior_pid to CHILD_PID, and then ensure that all | |
470 | breakpoints are really set in CHILD_PID. | |
c5aa993b | 471 | */ |
c906108c SS |
472 | target_mourn_inferior (); |
473 | ||
474 | /* Ask the tty subsystem to switch to the one we specified earlier | |
475 | (or to share the current terminal, if none was specified). */ | |
476 | ||
477 | new_tty (); | |
478 | ||
479 | dont_repeat (); | |
480 | sprintf (pid_spelling, "%d", child_pid); | |
481 | target_require_attach (pid_spelling, 1); | |
482 | ||
483 | /* Perform any necessary cleanup, after attachment. (This form | |
484 | of attaching can behave differently on some targets than the | |
485 | standard method, where a process formerly not under debugger | |
486 | control was suddenly attached to..) | |
c5aa993b | 487 | */ |
c906108c SS |
488 | target_post_follow_inferior_by_clone (); |
489 | ||
490 | *followed_child = 1; | |
491 | } | |
492 | ||
493 | /* Discard the handoff sempahore. */ | |
494 | (void) close (handoff_semaphore[SEM_LISTEN]); | |
495 | (void) close (handoff_semaphore[SEM_TALK]); | |
496 | } | |
497 | ||
498 | /* Accept NTRAPS traps from the inferior. */ | |
499 | ||
500 | void | |
fba45db2 | 501 | startup_inferior (int ntraps) |
c906108c SS |
502 | { |
503 | int pending_execs = ntraps; | |
504 | int terminal_initted; | |
505 | ||
506 | /* The process was started by the fork that created it, | |
507 | but it will have stopped one instruction after execing the shell. | |
508 | Here we must get it up to actual execution of the real program. */ | |
509 | ||
510 | clear_proceed_status (); | |
511 | ||
512 | init_wait_for_inferior (); | |
513 | ||
514 | terminal_initted = 0; | |
515 | ||
516 | if (STARTUP_WITH_SHELL) | |
517 | inferior_ignoring_startup_exec_events = ntraps; | |
518 | else | |
519 | inferior_ignoring_startup_exec_events = 0; | |
520 | inferior_ignoring_leading_exec_events = | |
521 | target_reported_exec_events_per_exec_call () - 1; | |
522 | ||
523 | #ifdef STARTUP_INFERIOR | |
524 | STARTUP_INFERIOR (pending_execs); | |
525 | #else | |
526 | while (1) | |
527 | { | |
528 | stop_soon_quietly = 1; /* Make wait_for_inferior be quiet */ | |
529 | wait_for_inferior (); | |
530 | if (stop_signal != TARGET_SIGNAL_TRAP) | |
531 | { | |
532 | /* Let shell child handle its own signals in its own way */ | |
533 | /* FIXME, what if child has exit()ed? Must exit loop somehow */ | |
534 | resume (0, stop_signal); | |
535 | } | |
536 | else | |
537 | { | |
538 | /* We handle SIGTRAP, however; it means child did an exec. */ | |
539 | if (!terminal_initted) | |
540 | { | |
541 | /* Now that the child has exec'd we know it has already set its | |
c5aa993b JM |
542 | process group. On POSIX systems, tcsetpgrp will fail with |
543 | EPERM if we try it before the child's setpgid. */ | |
c906108c SS |
544 | |
545 | /* Set up the "saved terminal modes" of the inferior | |
c5aa993b | 546 | based on what modes we are starting it with. */ |
c906108c SS |
547 | target_terminal_init (); |
548 | ||
549 | /* Install inferior's terminal modes. */ | |
550 | target_terminal_inferior (); | |
551 | ||
552 | terminal_initted = 1; | |
553 | } | |
554 | ||
555 | pending_execs = pending_execs - 1; | |
556 | if (0 == pending_execs) | |
557 | break; | |
558 | ||
559 | resume (0, TARGET_SIGNAL_0); /* Just make it go on */ | |
560 | } | |
561 | } | |
562 | #endif /* STARTUP_INFERIOR */ | |
563 | stop_soon_quietly = 0; | |
564 | } |