1 /* Fork a Unix child process, and set up to debug it, for GDB.
2 Copyright 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000,
3 2001 Free Software Foundation, Inc.
4 Contributed by Cygnus Support.
6 This file is part of GDB.
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.
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.
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. */
24 #include "gdb_string.h"
25 #include "frame.h" /* required by inferior.h */
29 #include "gdb_vfork.h"
32 #include "gdbthread.h"
33 #include "command.h" /* for dont_repeat () */
37 /* This just gets used as a default if we can't find SHELL */
39 #define SHELL_FILE "/bin/sh"
42 extern char **environ
;
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".
51 breakup_args (char *scratch
, char **argv
)
58 /* Scan past leading separators */
59 while (*cp
== ' ' || *cp
== '\t' || *cp
== '\n')
64 /* Break if at end of string */
71 /* Scan for next arg separator */
72 cp
= strchr (cp
, ' ');
74 cp
= strchr (cp
, '\t');
76 cp
= strchr (cp
, '\n');
78 /* No separators => end of string => break */
82 /* Replace the separator with a terminator */
86 /* execv requires a null-terminated arg vector */
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(). */
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
)
105 static char default_shell_file
[] = SHELL_FILE
;
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;
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. */
119 exec_file
= get_exec_file (1);
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.
125 if (STARTUP_WITH_SHELL
)
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
;
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 '. */
138 len
= 5 + 4 * strlen (exec_file
) + 1 + strlen (allargs
) + 1 + /*slop */ 12;
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
);
145 shell_command
= (char *) alloca (len
);
146 shell_command
[0] = '\0';
151 /* We're going to call execvp. Create argv */
152 /* Largest case: every other character is a separate arg */
153 argv
= (char **) xmalloc (((strlen (allargs
) + 1) / (unsigned) 2 + 2) * sizeof (*argv
));
155 breakup_args (allargs
, &argv
[1]);
161 /* We're going to call a shell */
163 /* Now add exec_file, quoting as necessary. */
168 strcat (shell_command
, "exec ");
170 /* Quoting in this style is said to work with all shells. But csh
171 on IRIX 4.0.1 can't deal with it. So we only quote it if we need
205 strcat (shell_command
, "'");
206 for (p
= exec_file
; *p
!= '\0'; ++p
)
209 strcat (shell_command
, "'\\''");
211 strncat (shell_command
, p
, 1);
213 strcat (shell_command
, "'");
216 strcat (shell_command
, exec_file
);
218 strcat (shell_command
, " ");
219 strcat (shell_command
, allargs
);
223 /* exec is said to fail if the executable is open. */
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
229 save_our_env
= environ
;
231 /* Tell the terminal handling subsystem what tty we plan to run on;
232 it will just record the information for later. */
234 new_tty_prefork (inferior_io_terminal
);
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. */
240 gdb_flush (gdb_stdout
);
241 gdb_flush (gdb_stderr
);
243 /* If there's any initialization of the target layers that must happen
244 to prepare to handle the child we're about fork, do it now...
246 if (pre_trace_fun
!= NULL
)
255 perror_with_name ("vfork");
262 /* Run inferior in a separate process group. */
263 debug_setpgrp
= gdb_setpgid ();
264 if (debug_setpgrp
== -1)
265 perror ("setpgrp failed in child");
267 /* Ask the tty subsystem to switch to the one we specified earlier
268 (or to share the current terminal, if none was specified). */
272 /* Changing the signal handlers for the inferior after
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
278 /* "Trace me, Dr. Memory!" */
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!
289 /* There is no execlpe call, so we have to set the environment
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. */
296 /* If we decided above to start up with a 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.
306 execlp (shell_file
, shell_file
, "-c", shell_command
, (char *) 0);
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
);
316 /* Otherwise, we directly exec the target program with execvp. */
320 execvp (exec_file
, argv
);
322 /* If we get here, it's an error */
323 errstring
= safe_strerror (errno
);
324 fprintf_unfiltered (gdb_stderr
, "Cannot exec %s ", exec_file
);
327 while (argv
[i
] != NULL
)
330 fprintf_unfiltered (gdb_stderr
, " ");
331 fprintf_unfiltered (gdb_stderr
, "%s", argv
[i
]);
334 fprintf_unfiltered (gdb_stderr
, ".\n");
335 /* This extra info seems to be useless
336 fprintf_unfiltered (gdb_stderr, "Got error %s.\n", errstring);
338 gdb_flush (gdb_stderr
);
343 /* Restore our environment in case a vforked child clob'd it. */
344 environ
= save_our_env
;
348 inferior_pid
= pid
; /* Needed for wait_for_inferior stuff below */
350 /* Now that we have a child process, make it our target, and
351 initialize anything target-vector-specific that needs initializing. */
353 (*init_trace_fun
) (pid
);
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
359 /* Allow target dependent code to play with the new process. This might be
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
);
364 #ifdef SOLIB_CREATE_INFERIOR_HOOK
365 SOLIB_CREATE_INFERIOR_HOOK (pid
);
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.
375 Also, the original debugger will set FOLLOWED_CHILD FALSE, while the
376 clone will set it TRUE.
379 clone_and_follow_inferior (int child_pid
, int *followed_child
)
381 extern int auto_solib_add
;
385 char pid_spelling
[100]; /* Arbitrary but sufficient length. */
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.)
395 #define SEM_LISTEN (0)
396 int handoff_semaphore
[2]; /* Original "talks" to [1], clone "listens" to [0] */
400 /* Set debug_fork then attach to the child while it sleeps, to debug. */
401 static int debug_fork
= 0;
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. */
407 gdb_flush (gdb_stdout
);
408 gdb_flush (gdb_stderr
);
410 /* Open the semaphore pipes.
412 status
= pipe (handoff_semaphore
);
414 error ("error getting pipe for handoff semaphore");
416 /* Clone the debugger. */
419 debugger_pid
= fork ();
421 debugger_pid
= vfork ();
423 debugger_pid
= fork ();
426 if (debugger_pid
< 0)
427 perror_with_name ("fork");
429 /* Are we the original debugger? If so, we must relinquish all claims
431 if (debugger_pid
!= 0)
433 char signal_spelling
[100]; /* Arbitrary but sufficient length */
435 /* Detach from CHILD_PID. Deliver a "stop" signal when we do, though,
436 so that it remains stopped until the clone debugger can attach
439 detach_breakpoints (child_pid
);
441 sprintf (signal_spelling
, "%d", target_signal_to_host (TARGET_SIGNAL_STOP
));
442 target_require_detach (child_pid
, signal_spelling
, 1);
444 /* Notify the clone debugger that it should attach to CHILD_PID. */
445 write (handoff_semaphore
[SEM_TALK
], &talk_value
, sizeof (talk_value
));
450 /* We're the child. */
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
461 Wait until the original debugger relinquishes control of CHILD_PID,
464 read (handoff_semaphore
[SEM_LISTEN
], &listen_value
, sizeof (listen_value
));
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.
472 target_mourn_inferior ();
474 /* Ask the tty subsystem to switch to the one we specified earlier
475 (or to share the current terminal, if none was specified). */
480 sprintf (pid_spelling
, "%d", child_pid
);
481 target_require_attach (pid_spelling
, 1);
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..)
488 target_post_follow_inferior_by_clone ();
493 /* Discard the handoff sempahore. */
494 (void) close (handoff_semaphore
[SEM_LISTEN
]);
495 (void) close (handoff_semaphore
[SEM_TALK
]);
498 /* Accept NTRAPS traps from the inferior. */
501 startup_inferior (int ntraps
)
503 int pending_execs
= ntraps
;
504 int terminal_initted
;
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. */
510 clear_proceed_status ();
512 init_wait_for_inferior ();
514 terminal_initted
= 0;
516 if (STARTUP_WITH_SHELL
)
517 inferior_ignoring_startup_exec_events
= ntraps
;
519 inferior_ignoring_startup_exec_events
= 0;
520 inferior_ignoring_leading_exec_events
=
521 target_reported_exec_events_per_exec_call () - 1;
523 #ifdef STARTUP_INFERIOR
524 STARTUP_INFERIOR (pending_execs
);
528 stop_soon_quietly
= 1; /* Make wait_for_inferior be quiet */
529 wait_for_inferior ();
530 if (stop_signal
!= TARGET_SIGNAL_TRAP
)
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
);
538 /* We handle SIGTRAP, however; it means child did an exec. */
539 if (!terminal_initted
)
541 /* Now that the child has exec'd we know it has already set its
542 process group. On POSIX systems, tcsetpgrp will fail with
543 EPERM if we try it before the child's setpgid. */
545 /* Set up the "saved terminal modes" of the inferior
546 based on what modes we are starting it with. */
547 target_terminal_init ();
549 /* Install inferior's terminal modes. */
550 target_terminal_inferior ();
552 terminal_initted
= 1;
555 pending_execs
= pending_execs
- 1;
556 if (0 == pending_execs
)
559 resume (0, TARGET_SIGNAL_0
); /* Just make it go on */
562 #endif /* STARTUP_INFERIOR */
563 stop_soon_quietly
= 0;