1 /* Fork a Unix child process, and set up to debug it, for GDB.
2 Copyright 1990, 91, 92, 93, 94, 1996, 1999 Free Software Foundation, Inc.
3 Contributed by Cygnus Support.
5 This file is part of GDB.
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 2 of the License, or
10 (at your option) any later version.
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.
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
23 #include "gdb_string.h"
24 #include "frame.h" /* required by inferior.h */
30 #include "gdbthread.h"
31 #include "command.h" /* for dont_repeat () */
35 /* This just gets used as a default if we can't find SHELL */
37 #define SHELL_FILE "/bin/sh"
40 extern char **environ
;
42 /* This function breaks up an argument string into an argument
43 * vector suitable for passing to execvp().
44 * E.g., on "run a b c d" this routine would get as input
45 * the string "a b c d", and as output it would fill in argv with
46 * the four arguments "a", "b", "c", "d".
49 breakup_args (char *scratch
, char **argv
)
56 /* Scan past leading separators */
57 while (*cp
== ' ' || *cp
== '\t' || *cp
== '\n')
62 /* Break if at end of string */
69 /* Scan for next arg separator */
70 cp
= strchr (cp
, ' ');
72 cp
= strchr (cp
, '\t');
74 cp
= strchr (cp
, '\n');
76 /* No separators => end of string => break */
80 /* Replace the separator with a terminator */
84 /* execv requires a null-terminated arg vector */
90 /* Start an inferior Unix child process and sets inferior_pid to its pid.
91 EXEC_FILE is the file to run.
92 ALLARGS is a string containing the arguments to the program.
93 ENV is the environment vector to pass. SHELL_FILE is the shell file,
94 or NULL if we should pick one. Errors reported with error(). */
97 fork_inferior (char *exec_file
, char *allargs
, char **env
,
98 void (*traceme_fun
) (void), void (*init_trace_fun
) (int),
99 void (*pre_trace_fun
) (void), char *shell_file
)
103 static char default_shell_file
[] = SHELL_FILE
;
105 /* Set debug_fork then attach to the child while it sleeps, to debug. */
106 static int debug_fork
= 0;
107 /* This is set to the result of setpgrp, which if vforked, will be visible
108 to you in the parent process. It's only used by humans for debugging. */
109 static int debug_setpgrp
= 657473;
114 /* If no exec file handed to us, get it from the exec-file command -- with
115 a good, common error message if none is specified. */
117 exec_file
= get_exec_file (1);
119 /* STARTUP_WITH_SHELL is defined in inferior.h.
120 * If 0, we'll just do a fork/exec, no shell, so don't
121 * bother figuring out what shell.
123 if (STARTUP_WITH_SHELL
)
125 /* Figure out what shell to start up the user program under. */
126 if (shell_file
== NULL
)
127 shell_file
= getenv ("SHELL");
128 if (shell_file
== NULL
)
129 shell_file
= default_shell_file
;
133 /* Multiplying the length of exec_file by 4 is to account for the fact
134 that it may expand when quoted; it is a worst-case number based on
135 every character being '. */
136 len
= 5 + 4 * strlen (exec_file
) + 1 + strlen (allargs
) + 1 + /*slop */ 12;
137 /* If desired, concat something onto the front of ALLARGS.
138 SHELL_COMMAND is the result. */
139 #ifdef SHELL_COMMAND_CONCAT
140 shell_command
= (char *) alloca (strlen (SHELL_COMMAND_CONCAT
) + len
);
141 strcpy (shell_command
, SHELL_COMMAND_CONCAT
);
143 shell_command
= (char *) alloca (len
);
144 shell_command
[0] = '\0';
149 /* We're going to call execvp. Create argv */
150 /* Largest case: every other character is a separate arg */
151 argv
= (char **) xmalloc (((strlen (allargs
) + 1) / (unsigned) 2 + 2) * sizeof (*argv
));
153 breakup_args (allargs
, &argv
[1]);
159 /* We're going to call a shell */
161 /* Now add exec_file, quoting as necessary. */
166 strcat (shell_command
, "exec ");
168 /* Quoting in this style is said to work with all shells. But csh
169 on IRIX 4.0.1 can't deal with it. So we only quote it if we need
203 strcat (shell_command
, "'");
204 for (p
= exec_file
; *p
!= '\0'; ++p
)
207 strcat (shell_command
, "'\\''");
209 strncat (shell_command
, p
, 1);
211 strcat (shell_command
, "'");
214 strcat (shell_command
, exec_file
);
216 strcat (shell_command
, " ");
217 strcat (shell_command
, allargs
);
221 /* exec is said to fail if the executable is open. */
224 /* Retain a copy of our environment variables, since the child will
225 replace the value of environ and if we're vforked, we have to
227 save_our_env
= environ
;
229 /* Tell the terminal handling subsystem what tty we plan to run on;
230 it will just record the information for later. */
232 new_tty_prefork (inferior_io_terminal
);
234 /* It is generally good practice to flush any possible pending stdio
235 output prior to doing a fork, to avoid the possibility of both the
236 parent and child flushing the same data after the fork. */
238 gdb_flush (gdb_stdout
);
239 gdb_flush (gdb_stderr
);
241 /* If there's any initialization of the target layers that must happen
242 to prepare to handle the child we're about fork, do it now...
244 if (pre_trace_fun
!= NULL
)
247 #if defined(USG) && !defined(HAVE_VFORK)
257 perror_with_name ("vfork");
264 /* Run inferior in a separate process group. */
265 debug_setpgrp
= gdb_setpgid ();
266 if (debug_setpgrp
== -1)
267 perror ("setpgrp failed in child");
269 /* Ask the tty subsystem to switch to the one we specified earlier
270 (or to share the current terminal, if none was specified). */
274 /* Changing the signal handlers for the inferior after
275 a vfork can also change them for the superior, so we don't mess
276 with signals here. See comments in
277 initialize_signals for how we get the right signal handlers
280 /* "Trace me, Dr. Memory!" */
282 /* The call above set this process (the "child") as debuggable
283 * by the original gdb process (the "parent"). Since processes
284 * (unlike people) can have only one parent, if you are
285 * debugging gdb itself (and your debugger is thus _already_ the
286 * controller/parent for this child), code from here on out
287 * is undebuggable. Indeed, you probably got an error message
288 * saying "not parent". Sorry--you'll have to use print statements!
291 /* There is no execlpe call, so we have to set the environment
292 for our child in the global variable. If we've vforked, this
293 clobbers the parent, but environ is restored a few lines down
294 in the parent. By the way, yes we do need to look down the
295 path to find $SHELL. Rich Pixley says so, and I agree. */
298 /* If we decided above to start up with a shell,
300 * "-c" says to interpret the next arg as a shell command
301 * to execute, and this command is "exec <target-program> <args>".
302 * "-f" means "fast startup" to the c-shell, which means
303 * don't do .cshrc file. Doing .cshrc may cause fork/exec
304 * events which will confuse debugger start-up code.
308 execlp (shell_file
, shell_file
, "-c", shell_command
, (char *) 0);
310 /* If we get here, it's an error */
311 fprintf_unfiltered (gdb_stderr
, "Cannot exec %s: %s.\n", shell_file
,
312 safe_strerror (errno
));
313 gdb_flush (gdb_stderr
);
318 /* Otherwise, we directly exec the target program with execvp. */
322 execvp (exec_file
, argv
);
324 /* If we get here, it's an error */
325 errstring
= safe_strerror (errno
);
326 fprintf_unfiltered (gdb_stderr
, "Cannot exec %s ", exec_file
);
329 while (argv
[i
] != NULL
)
332 fprintf_unfiltered (gdb_stderr
, " ");
333 fprintf_unfiltered (gdb_stderr
, "%s", argv
[i
]);
336 fprintf_unfiltered (gdb_stderr
, ".\n");
337 /* This extra info seems to be useless
338 fprintf_unfiltered (gdb_stderr, "Got error %s.\n", errstring);
340 gdb_flush (gdb_stderr
);
345 /* Restore our environment in case a vforked child clob'd it. */
346 environ
= save_our_env
;
350 inferior_pid
= pid
; /* Needed for wait_for_inferior stuff below */
352 /* Now that we have a child process, make it our target, and
353 initialize anything target-vector-specific that needs initializing. */
355 (*init_trace_fun
) (pid
);
357 /* We are now in the child process of interest, having exec'd the
358 correct program, and are poised at the first instruction of the
361 /* Allow target dependant code to play with the new process. This might be
362 used to have target-specific code initialize a variable in the new process
363 prior to executing the first instruction. */
364 TARGET_CREATE_INFERIOR_HOOK (pid
);
366 #ifdef SOLIB_CREATE_INFERIOR_HOOK
367 SOLIB_CREATE_INFERIOR_HOOK (pid
);
371 /* An inferior Unix process CHILD_PID has been created by a call to
372 fork() (or variants like vfork). It is presently stopped, and waiting
373 to be resumed. clone_and_follow_inferior will fork the debugger,
374 and that clone will "follow" (attach to) CHILD_PID. The original copy
375 of the debugger will not touch CHILD_PID again.
377 Also, the original debugger will set FOLLOWED_CHILD FALSE, while the
378 clone will set it TRUE.
381 clone_and_follow_inferior (int child_pid
, int *followed_child
)
383 extern int auto_solib_add
;
387 char pid_spelling
[100]; /* Arbitrary but sufficient length. */
389 /* This semaphore is used to coordinate the two debuggers' handoff
390 of CHILD_PID. The original debugger will detach from CHILD_PID,
391 and then the clone debugger will attach to it. (It must be done
392 this way because on some targets, only one process at a time can
393 trace another. Thus, the original debugger must relinquish its
394 tracing rights before the clone can pick them up.)
397 #define SEM_LISTEN (0)
398 int handoff_semaphore
[2]; /* Original "talks" to [1], clone "listens" to [0] */
402 /* Set debug_fork then attach to the child while it sleeps, to debug. */
403 static int debug_fork
= 0;
405 /* It is generally good practice to flush any possible pending stdio
406 output prior to doing a fork, to avoid the possibility of both the
407 parent and child flushing the same data after the fork. */
409 gdb_flush (gdb_stdout
);
410 gdb_flush (gdb_stderr
);
412 /* Open the semaphore pipes.
414 status
= pipe (handoff_semaphore
);
416 error ("error getting pipe for handoff semaphore");
418 /* Clone the debugger. */
419 #if defined(USG) && !defined(HAVE_VFORK)
420 debugger_pid
= fork ();
423 debugger_pid
= fork ();
425 debugger_pid
= vfork ();
428 if (debugger_pid
< 0)
429 perror_with_name ("fork");
431 /* Are we the original debugger? If so, we must relinquish all claims
433 if (debugger_pid
!= 0)
435 char signal_spelling
[100]; /* Arbitrary but sufficient length */
437 /* Detach from CHILD_PID. Deliver a "stop" signal when we do, though,
438 so that it remains stopped until the clone debugger can attach
441 detach_breakpoints (child_pid
);
443 sprintf (signal_spelling
, "%d", target_signal_to_host (TARGET_SIGNAL_STOP
));
444 target_require_detach (child_pid
, signal_spelling
, 1);
446 /* Notify the clone debugger that it should attach to CHILD_PID. */
447 write (handoff_semaphore
[SEM_TALK
], &talk_value
, sizeof (talk_value
));
452 /* We're the child. */
458 /* The child (i.e., the cloned debugger) must now attach to
459 CHILD_PID. inferior_pid is presently set to the parent process
460 of the fork, while CHILD_PID should be the child process of the
463 Wait until the original debugger relinquishes control of CHILD_PID,
466 read (handoff_semaphore
[SEM_LISTEN
], &listen_value
, sizeof (listen_value
));
468 /* Note that we DON'T want to actually detach from inferior_pid,
469 because that would allow it to run free. The original
470 debugger wants to retain control of the process. So, we
471 just reset inferior_pid to CHILD_PID, and then ensure that all
472 breakpoints are really set in CHILD_PID.
474 target_mourn_inferior ();
476 /* Ask the tty subsystem to switch to the one we specified earlier
477 (or to share the current terminal, if none was specified). */
482 sprintf (pid_spelling
, "%d", child_pid
);
483 target_require_attach (pid_spelling
, 1);
485 /* Perform any necessary cleanup, after attachment. (This form
486 of attaching can behave differently on some targets than the
487 standard method, where a process formerly not under debugger
488 control was suddenly attached to..)
490 target_post_follow_inferior_by_clone ();
495 /* Discard the handoff sempahore. */
496 (void) close (handoff_semaphore
[SEM_LISTEN
]);
497 (void) close (handoff_semaphore
[SEM_TALK
]);
500 /* Accept NTRAPS traps from the inferior. */
503 startup_inferior (int ntraps
)
505 int pending_execs
= ntraps
;
506 int terminal_initted
;
508 /* The process was started by the fork that created it,
509 but it will have stopped one instruction after execing the shell.
510 Here we must get it up to actual execution of the real program. */
512 clear_proceed_status ();
514 init_wait_for_inferior ();
516 terminal_initted
= 0;
518 if (STARTUP_WITH_SHELL
)
519 inferior_ignoring_startup_exec_events
= ntraps
;
521 inferior_ignoring_startup_exec_events
= 0;
522 inferior_ignoring_leading_exec_events
=
523 target_reported_exec_events_per_exec_call () - 1;
525 #ifdef STARTUP_INFERIOR
526 STARTUP_INFERIOR (pending_execs
);
530 stop_soon_quietly
= 1; /* Make wait_for_inferior be quiet */
531 wait_for_inferior ();
532 if (stop_signal
!= TARGET_SIGNAL_TRAP
)
534 /* Let shell child handle its own signals in its own way */
535 /* FIXME, what if child has exit()ed? Must exit loop somehow */
536 resume (0, stop_signal
);
540 /* We handle SIGTRAP, however; it means child did an exec. */
541 if (!terminal_initted
)
543 /* Now that the child has exec'd we know it has already set its
544 process group. On POSIX systems, tcsetpgrp will fail with
545 EPERM if we try it before the child's setpgid. */
547 /* Set up the "saved terminal modes" of the inferior
548 based on what modes we are starting it with. */
549 target_terminal_init ();
551 /* Install inferior's terminal modes. */
552 target_terminal_inferior ();
554 terminal_initted
= 1;
557 pending_execs
= pending_execs
- 1;
558 if (0 == pending_execs
)
561 resume (0, TARGET_SIGNAL_0
); /* Just make it go on */
564 #endif /* STARTUP_INFERIOR */
565 stop_soon_quietly
= 0;