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"
34 /* This just gets used as a default if we can't find SHELL */
36 #define SHELL_FILE "/bin/sh"
39 extern char **environ
;
41 /* This function breaks up an argument string into an argument
42 * vector suitable for passing to execvp().
43 * E.g., on "run a b c d" this routine would get as input
44 * the string "a b c d", and as output it would fill in argv with
45 * the four arguments "a", "b", "c", "d".
59 /* Scan past leading separators */
60 while (*cp
== ' ' || *cp
== '\t' || *cp
== '\n')
65 /* Break if at end of string */
72 /* Scan for next arg separator */
73 cp
= strchr (cp
, ' ');
75 cp
= strchr (cp
, '\t');
77 cp
= strchr (cp
, '\n');
79 /* No separators => end of string => break */
83 /* Replace the separator with a terminator */
87 /* execv requires a null-terminated arg vector */
93 /* Start an inferior Unix child process and sets inferior_pid to its pid.
94 EXEC_FILE is the file to run.
95 ALLARGS is a string containing the arguments to the program.
96 ENV is the environment vector to pass. SHELL_FILE is the shell file,
97 or NULL if we should pick one. Errors reported with error(). */
100 fork_inferior (exec_file
, allargs
, env
, traceme_fun
, init_trace_fun
,
101 pre_trace_fun
, shell_file
)
105 void (*traceme_fun
) PARAMS ((void));
106 void (*init_trace_fun
) PARAMS ((int));
107 void (*pre_trace_fun
) PARAMS ((void));
112 static char default_shell_file
[] = SHELL_FILE
;
114 /* Set debug_fork then attach to the child while it sleeps, to debug. */
115 static int debug_fork
= 0;
116 /* This is set to the result of setpgrp, which if vforked, will be visible
117 to you in the parent process. It's only used by humans for debugging. */
118 static int debug_setpgrp
= 657473;
123 /* If no exec file handed to us, get it from the exec-file command -- with
124 a good, common error message if none is specified. */
126 exec_file
= get_exec_file (1);
128 /* STARTUP_WITH_SHELL is defined in inferior.h.
129 * If 0, we'll just do a fork/exec, no shell, so don't
130 * bother figuring out what shell.
132 if (STARTUP_WITH_SHELL
)
134 /* Figure out what shell to start up the user program under. */
135 if (shell_file
== NULL
)
136 shell_file
= getenv ("SHELL");
137 if (shell_file
== NULL
)
138 shell_file
= default_shell_file
;
142 /* Multiplying the length of exec_file by 4 is to account for the fact
143 that it may expand when quoted; it is a worst-case number based on
144 every character being '. */
145 len
= 5 + 4 * strlen (exec_file
) + 1 + strlen (allargs
) + 1 + /*slop */ 12;
146 /* If desired, concat something onto the front of ALLARGS.
147 SHELL_COMMAND is the result. */
148 #ifdef SHELL_COMMAND_CONCAT
149 shell_command
= (char *) alloca (strlen (SHELL_COMMAND_CONCAT
) + len
);
150 strcpy (shell_command
, SHELL_COMMAND_CONCAT
);
152 shell_command
= (char *) alloca (len
);
153 shell_command
[0] = '\0';
158 /* We're going to call execvp. Create argv */
159 /* Largest case: every other character is a separate arg */
160 argv
= (char **) xmalloc (((strlen (allargs
) + 1) / (unsigned) 2 + 2) * sizeof (*argv
));
162 breakup_args (allargs
, &argv
[1]);
168 /* We're going to call a shell */
170 /* Now add exec_file, quoting as necessary. */
175 strcat (shell_command
, "exec ");
177 /* Quoting in this style is said to work with all shells. But csh
178 on IRIX 4.0.1 can't deal with it. So we only quote it if we need
212 strcat (shell_command
, "'");
213 for (p
= exec_file
; *p
!= '\0'; ++p
)
216 strcat (shell_command
, "'\\''");
218 strncat (shell_command
, p
, 1);
220 strcat (shell_command
, "'");
223 strcat (shell_command
, exec_file
);
225 strcat (shell_command
, " ");
226 strcat (shell_command
, allargs
);
230 /* exec is said to fail if the executable is open. */
233 /* Retain a copy of our environment variables, since the child will
234 replace the value of environ and if we're vforked, we have to
236 save_our_env
= environ
;
238 /* Tell the terminal handling subsystem what tty we plan to run on;
239 it will just record the information for later. */
241 new_tty_prefork (inferior_io_terminal
);
243 /* It is generally good practice to flush any possible pending stdio
244 output prior to doing a fork, to avoid the possibility of both the
245 parent and child flushing the same data after the fork. */
247 gdb_flush (gdb_stdout
);
248 gdb_flush (gdb_stderr
);
250 /* If there's any initialization of the target layers that must happen
251 to prepare to handle the child we're about fork, do it now...
253 if (pre_trace_fun
!= NULL
)
256 #if defined(USG) && !defined(HAVE_VFORK)
266 perror_with_name ("vfork");
273 /* Run inferior in a separate process group. */
274 debug_setpgrp
= gdb_setpgid ();
275 if (debug_setpgrp
== -1)
276 perror ("setpgrp failed in child");
278 /* Ask the tty subsystem to switch to the one we specified earlier
279 (or to share the current terminal, if none was specified). */
283 /* Changing the signal handlers for the inferior after
284 a vfork can also change them for the superior, so we don't mess
285 with signals here. See comments in
286 initialize_signals for how we get the right signal handlers
289 /* "Trace me, Dr. Memory!" */
291 /* The call above set this process (the "child") as debuggable
292 * by the original gdb process (the "parent"). Since processes
293 * (unlike people) can have only one parent, if you are
294 * debugging gdb itself (and your debugger is thus _already_ the
295 * controller/parent for this child), code from here on out
296 * is undebuggable. Indeed, you probably got an error message
297 * saying "not parent". Sorry--you'll have to use print statements!
300 /* There is no execlpe call, so we have to set the environment
301 for our child in the global variable. If we've vforked, this
302 clobbers the parent, but environ is restored a few lines down
303 in the parent. By the way, yes we do need to look down the
304 path to find $SHELL. Rich Pixley says so, and I agree. */
307 /* If we decided above to start up with a shell,
309 * "-c" says to interpret the next arg as a shell command
310 * to execute, and this command is "exec <target-program> <args>".
311 * "-f" means "fast startup" to the c-shell, which means
312 * don't do .cshrc file. Doing .cshrc may cause fork/exec
313 * events which will confuse debugger start-up code.
317 execlp (shell_file
, shell_file
, "-c", shell_command
, (char *) 0);
319 /* If we get here, it's an error */
320 fprintf_unfiltered (gdb_stderr
, "Cannot exec %s: %s.\n", shell_file
,
321 safe_strerror (errno
));
322 gdb_flush (gdb_stderr
);
327 /* Otherwise, we directly exec the target program with execvp. */
331 execvp (exec_file
, argv
);
333 /* If we get here, it's an error */
334 errstring
= safe_strerror (errno
);
335 fprintf_unfiltered (gdb_stderr
, "Cannot exec %s ", exec_file
);
338 while (argv
[i
] != NULL
)
341 fprintf_unfiltered (gdb_stderr
, " ");
342 fprintf_unfiltered (gdb_stderr
, "%s", argv
[i
]);
345 fprintf_unfiltered (gdb_stderr
, ".\n");
346 /* This extra info seems to be useless
347 fprintf_unfiltered (gdb_stderr, "Got error %s.\n", errstring);
349 gdb_flush (gdb_stderr
);
354 /* Restore our environment in case a vforked child clob'd it. */
355 environ
= save_our_env
;
359 inferior_pid
= pid
; /* Needed for wait_for_inferior stuff below */
361 /* Now that we have a child process, make it our target, and
362 initialize anything target-vector-specific that needs initializing. */
364 (*init_trace_fun
) (pid
);
366 /* We are now in the child process of interest, having exec'd the
367 correct program, and are poised at the first instruction of the
370 /* Allow target dependant code to play with the new process. This might be
371 used to have target-specific code initialize a variable in the new process
372 prior to executing the first instruction. */
373 TARGET_CREATE_INFERIOR_HOOK (pid
);
375 #ifdef SOLIB_CREATE_INFERIOR_HOOK
376 SOLIB_CREATE_INFERIOR_HOOK (pid
);
380 /* An inferior Unix process CHILD_PID has been created by a call to
381 fork() (or variants like vfork). It is presently stopped, and waiting
382 to be resumed. clone_and_follow_inferior will fork the debugger,
383 and that clone will "follow" (attach to) CHILD_PID. The original copy
384 of the debugger will not touch CHILD_PID again.
386 Also, the original debugger will set FOLLOWED_CHILD FALSE, while the
387 clone will set it TRUE.
390 clone_and_follow_inferior (child_pid
, followed_child
)
394 extern int auto_solib_add
;
398 char pid_spelling
[100]; /* Arbitrary but sufficient length. */
400 /* This semaphore is used to coordinate the two debuggers' handoff
401 of CHILD_PID. The original debugger will detach from CHILD_PID,
402 and then the clone debugger will attach to it. (It must be done
403 this way because on some targets, only one process at a time can
404 trace another. Thus, the original debugger must relinquish its
405 tracing rights before the clone can pick them up.)
408 #define SEM_LISTEN (0)
409 int handoff_semaphore
[2]; /* Original "talks" to [1], clone "listens" to [0] */
413 /* Set debug_fork then attach to the child while it sleeps, to debug. */
414 static int debug_fork
= 0;
416 /* It is generally good practice to flush any possible pending stdio
417 output prior to doing a fork, to avoid the possibility of both the
418 parent and child flushing the same data after the fork. */
420 gdb_flush (gdb_stdout
);
421 gdb_flush (gdb_stderr
);
423 /* Open the semaphore pipes.
425 status
= pipe (handoff_semaphore
);
427 error ("error getting pipe for handoff semaphore");
429 /* Clone the debugger. */
430 #if defined(USG) && !defined(HAVE_VFORK)
431 debugger_pid
= fork ();
434 debugger_pid
= fork ();
436 debugger_pid
= vfork ();
439 if (debugger_pid
< 0)
440 perror_with_name ("fork");
442 /* Are we the original debugger? If so, we must relinquish all claims
444 if (debugger_pid
!= 0)
446 char signal_spelling
[100]; /* Arbitrary but sufficient length */
448 /* Detach from CHILD_PID. Deliver a "stop" signal when we do, though,
449 so that it remains stopped until the clone debugger can attach
452 detach_breakpoints (child_pid
);
454 sprintf (signal_spelling
, "%d", target_signal_to_host (TARGET_SIGNAL_STOP
));
455 target_require_detach (child_pid
, signal_spelling
, 1);
457 /* Notify the clone debugger that it should attach to CHILD_PID. */
458 write (handoff_semaphore
[SEM_TALK
], &talk_value
, sizeof (talk_value
));
463 /* We're the child. */
469 /* The child (i.e., the cloned debugger) must now attach to
470 CHILD_PID. inferior_pid is presently set to the parent process
471 of the fork, while CHILD_PID should be the child process of the
474 Wait until the original debugger relinquishes control of CHILD_PID,
477 read (handoff_semaphore
[SEM_LISTEN
], &listen_value
, sizeof (listen_value
));
479 /* Note that we DON'T want to actually detach from inferior_pid,
480 because that would allow it to run free. The original
481 debugger wants to retain control of the process. So, we
482 just reset inferior_pid to CHILD_PID, and then ensure that all
483 breakpoints are really set in CHILD_PID.
485 target_mourn_inferior ();
487 /* Ask the tty subsystem to switch to the one we specified earlier
488 (or to share the current terminal, if none was specified). */
493 sprintf (pid_spelling
, "%d", child_pid
);
494 target_require_attach (pid_spelling
, 1);
496 /* Perform any necessary cleanup, after attachment. (This form
497 of attaching can behave differently on some targets than the
498 standard method, where a process formerly not under debugger
499 control was suddenly attached to..)
501 target_post_follow_inferior_by_clone ();
506 /* Discard the handoff sempahore. */
507 (void) close (handoff_semaphore
[SEM_LISTEN
]);
508 (void) close (handoff_semaphore
[SEM_TALK
]);
511 /* Accept NTRAPS traps from the inferior. */
514 startup_inferior (ntraps
)
517 int pending_execs
= ntraps
;
518 int terminal_initted
;
520 /* The process was started by the fork that created it,
521 but it will have stopped one instruction after execing the shell.
522 Here we must get it up to actual execution of the real program. */
524 clear_proceed_status ();
526 init_wait_for_inferior ();
528 terminal_initted
= 0;
530 if (STARTUP_WITH_SHELL
)
531 inferior_ignoring_startup_exec_events
= ntraps
;
533 inferior_ignoring_startup_exec_events
= 0;
534 inferior_ignoring_leading_exec_events
=
535 target_reported_exec_events_per_exec_call () - 1;
537 #ifdef STARTUP_INFERIOR
538 STARTUP_INFERIOR (pending_execs
);
542 stop_soon_quietly
= 1; /* Make wait_for_inferior be quiet */
543 wait_for_inferior ();
544 if (stop_signal
!= TARGET_SIGNAL_TRAP
)
546 /* Let shell child handle its own signals in its own way */
547 /* FIXME, what if child has exit()ed? Must exit loop somehow */
548 resume (0, stop_signal
);
552 /* We handle SIGTRAP, however; it means child did an exec. */
553 if (!terminal_initted
)
555 /* Now that the child has exec'd we know it has already set its
556 process group. On POSIX systems, tcsetpgrp will fail with
557 EPERM if we try it before the child's setpgid. */
559 /* Set up the "saved terminal modes" of the inferior
560 based on what modes we are starting it with. */
561 target_terminal_init ();
563 /* Install inferior's terminal modes. */
564 target_terminal_inferior ();
566 terminal_initted
= 1;
569 pending_execs
= pending_execs
- 1;
570 if (0 == pending_execs
)
573 resume (0, TARGET_SIGNAL_0
); /* Just make it go on */
576 #endif /* STARTUP_INFERIOR */
577 stop_soon_quietly
= 0;