1 /* Fork a Unix child process, and set up to debug it, for GDB.
2 Copyright 1990, 1991, 1992, 1993, 1994, 1996 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, Boston, MA 02111-1307, USA. */
22 #include "gdb_string.h"
23 #include "frame.h" /* required by inferior.h */
29 #include "gdbthread.h"
38 /* This just gets used as a default if we can't find SHELL */
40 #define SHELL_FILE "/bin/sh"
43 extern char **environ
;
45 /* This function breaks up an argument string into an argument
46 * vector suitable for passing to execvp().
47 * E.g., on "run a b c d" this routine would get as input
48 * the string "a b c d", and as output it would fill in argv with
49 * the four arguments "a", "b", "c", "d".
61 printf("breakup_args: input = %s\n", scratch
);
65 /* Scan past leading separators */
66 while (*cp
== ' ' || *cp
== '\t' || *cp
== '\n') {
70 /* Break if at end of string */
71 if (*cp
== '\0') break;
76 /* Scan for next arg separator */
77 cp
= strchr (cp
, ' ');
79 cp
= strchr (cp
, '\t');
81 cp
= strchr (cp
, '\n');
83 /* No separators => end of string => break */
87 /* Replace the separator with a terminator */
91 /* execv requires a null-terminated arg vector */
97 /* Start an inferior Unix child process and sets inferior_pid to its pid.
98 EXEC_FILE is the file to run.
99 ALLARGS is a string containing the arguments to the program.
100 ENV is the environment vector to pass. SHELL_FILE is the shell file,
101 or NULL if we should pick one. Errors reported with error(). */
104 fork_inferior (exec_file
, allargs
, env
, traceme_fun
, init_trace_fun
,
105 pre_trace_fun
, shell_file
)
109 void (*traceme_fun
) PARAMS ((void));
110 void (*init_trace_fun
) PARAMS ((int));
111 void (*pre_trace_fun
) PARAMS ((void));
116 static char default_shell_file
[] = SHELL_FILE
;
118 /* Set debug_fork then attach to the child while it sleeps, to debug. */
119 static int debug_fork
= 0;
120 /* This is set to the result of setpgrp, which if vforked, will be visible
121 to you in the parent process. It's only used by humans for debugging. */
122 static int debug_setpgrp
= 657473;
128 /* If no exec file handed to us, get it from the exec-file command -- with
129 a good, common error message if none is specified. */
131 exec_file
= get_exec_file(1);
133 /* STARTUP_WITH_SHELL is defined in inferior.h.
134 * If 0, we'll just do a fork/exec, no shell, so don't
135 * bother figuring out what shell.
137 if (STARTUP_WITH_SHELL
) {
138 /* Figure out what shell to start up the user program under. */
139 if (shell_file
== NULL
)
140 shell_file
= getenv ("SHELL");
141 if (shell_file
== NULL
)
142 shell_file
= default_shell_file
;
147 printf("shell is %s\n", shell_file
);
150 /* Multiplying the length of exec_file by 4 is to account for the fact
151 that it may expand when quoted; it is a worst-case number based on
152 every character being '. */
153 len
= 5 + 4 * strlen (exec_file
) + 1 + strlen (allargs
) + 1 + /*slop*/ 12;
154 /* If desired, concat something onto the front of ALLARGS.
155 SHELL_COMMAND is the result. */
156 #ifdef SHELL_COMMAND_CONCAT
157 shell_command
= (char *) alloca (strlen (SHELL_COMMAND_CONCAT
) + len
);
158 strcpy (shell_command
, SHELL_COMMAND_CONCAT
);
160 shell_command
= (char *) alloca (len
);
161 shell_command
[0] = '\0';
165 /* We're going to call execvp. Create argv */
166 /* Largest case: every other character is a separate arg */
168 printf("allocating argv, length = %d\n",
170 (strlen (allargs
) + 1) / (unsigned) 2
175 argv
= (char **) xmalloc(((strlen (allargs
) + 1) / (unsigned) 2 + 2) * sizeof (*argv
));
177 breakup_args(allargs
, &argv
[1]);
181 /* We're going to call a shell */
183 /* Now add exec_file, quoting as necessary. */
188 strcat (shell_command
, "exec ");
190 /* Quoting in this style is said to work with all shells. But csh
191 on IRIX 4.0.1 can't deal with it. So we only quote it if we need
225 strcat (shell_command
, "'");
226 for (p
= exec_file
; *p
!= '\0'; ++p
)
229 strcat (shell_command
, "'\\''");
231 strncat (shell_command
, p
, 1);
233 strcat (shell_command
, "'");
236 strcat (shell_command
, exec_file
);
238 strcat (shell_command
, " ");
239 strcat (shell_command
, allargs
);
243 /* exec is said to fail if the executable is open. */
246 /* Retain a copy of our environment variables, since the child will
247 replace the value of environ and if we're vforked, we have to
249 save_our_env
= environ
;
251 /* Tell the terminal handling subsystem what tty we plan to run on;
252 it will just record the information for later. */
254 new_tty_prefork (inferior_io_terminal
);
256 /* It is generally good practice to flush any possible pending stdio
257 output prior to doing a fork, to avoid the possibility of both the
258 parent and child flushing the same data after the fork. */
260 gdb_flush (gdb_stdout
);
261 gdb_flush (gdb_stderr
);
263 /* If there's any initialization of the target layers that must happen
264 to prepare to handle the child we're about fork, do it now...
266 if (pre_trace_fun
!= NULL
)
269 #if defined(USG) && !defined(HAVE_VFORK)
279 perror_with_name ("vfork");
286 /* Run inferior in a separate process group. */
287 debug_setpgrp
= gdb_setpgid ();
288 if (debug_setpgrp
== -1)
289 perror("setpgrp failed in child");
291 /* Ask the tty subsystem to switch to the one we specified earlier
292 (or to share the current terminal, if none was specified). */
296 /* Changing the signal handlers for the inferior after
297 a vfork can also change them for the superior, so we don't mess
298 with signals here. See comments in
299 initialize_signals for how we get the right signal handlers
302 /* "Trace me, Dr. Memory!" */
304 /* The call above set this process (the "child") as debuggable
305 * by the original gdb process (the "parent"). Since processes
306 * (unlike people) can have only one parent, if you are
307 * debugging gdb itself (and your debugger is thus _already_ the
308 * controller/parent for this child), code from here on out
309 * is undebuggable. Indeed, you probably got an error message
310 * saying "not parent". Sorry--you'll have to use print statements!
313 /* There is no execlpe call, so we have to set the environment
314 for our child in the global variable. If we've vforked, this
315 clobbers the parent, but environ is restored a few lines down
316 in the parent. By the way, yes we do need to look down the
317 path to find $SHELL. Rich Pixley says so, and I agree. */
320 /* If we decided above to start up with a shell,
322 * "-c" says to interpret the next arg as a shell command
323 * to execute, and this command is "exec <target-program> <args>".
324 * "-f" means "fast startup" to the c-shell, which means
325 * don't do .cshrc file. Doing .cshrc may cause fork/exec
326 * events which will confuse debugger start-up code.
331 /* HP change is problematic. The -f option has different meanings
332 for different shells. It is particularly inappropriate for
334 execlp (shell_file
, shell_file
, "-f", "-c", shell_command
, (char *)0);
336 execlp (shell_file
, shell_file
, "-c", shell_command
, (char *)0);
340 /* If we get here, it's an error */
341 fprintf_unfiltered (gdb_stderr
, "Cannot exec %s: %s.\n", shell_file
,
342 safe_strerror (errno
));
343 gdb_flush (gdb_stderr
);
346 /* Otherwise, we directly exec the target program with execvp. */
350 printf("about to exec target, exec_file = %s\n", exec_file
);
352 while (argv
[i
] != NULL
) {
353 printf("strlen(argv[%d]) is %d\n", i
, strlen(argv
[i
]));
354 printf("argv[%d] is %s\n", i
, argv
[i
]);
358 execvp (exec_file
, argv
);
360 /* If we get here, it's an error */
361 errstring
= safe_strerror (errno
);
362 fprintf_unfiltered (gdb_stderr
, "Cannot exec %s ", exec_file
);
365 while (argv
[i
] != NULL
) {
367 fprintf_unfiltered (gdb_stderr
, " ");
368 fprintf_unfiltered (gdb_stderr
, "%s", argv
[i
]);
371 fprintf_unfiltered (gdb_stderr
, ".\n");
372 /* This extra info seems to be useless
373 fprintf_unfiltered (gdb_stderr, "Got error %s.\n", errstring);
375 gdb_flush (gdb_stderr
);
380 /* Restore our environment in case a vforked child clob'd it. */
381 environ
= save_our_env
;
385 inferior_pid
= pid
; /* Needed for wait_for_inferior stuff below */
387 /* Now that we have a child process, make it our target, and
388 initialize anything target-vector-specific that needs initializing. */
390 (*init_trace_fun
)(pid
);
392 /* We are now in the child process of interest, having exec'd the
393 correct program, and are poised at the first instruction of the
396 /* Allow target dependant code to play with the new process. This might be
397 used to have target-specific code initialize a variable in the new process
398 prior to executing the first instruction. */
399 TARGET_CREATE_INFERIOR_HOOK (pid
);
401 #ifdef SOLIB_CREATE_INFERIOR_HOOK
402 SOLIB_CREATE_INFERIOR_HOOK (pid
);
406 /* An inferior Unix process CHILD_PID has been created by a call to
407 fork() (or variants like vfork). It is presently stopped, and waiting
408 to be resumed. clone_and_follow_inferior will fork the debugger,
409 and that clone will "follow" (attach to) CHILD_PID. The original copy
410 of the debugger will not touch CHILD_PID again.
412 Also, the original debugger will set FOLLOWED_CHILD FALSE, while the
413 clone will set it TRUE.
416 clone_and_follow_inferior (child_pid
, followed_child
)
420 extern int auto_solib_add
;
424 char pid_spelling
[100]; /* Arbitrary but sufficient length. */
426 /* This semaphore is used to coordinate the two debuggers' handoff
427 of CHILD_PID. The original debugger will detach from CHILD_PID,
428 and then the clone debugger will attach to it. (It must be done
429 this way because on some targets, only one process at a time can
430 trace another. Thus, the original debugger must relinquish its
431 tracing rights before the clone can pick them up.)
434 #define SEM_LISTEN (0)
435 int handoff_semaphore
[2]; /* Original "talks" to [1], clone "listens" to [0] */
439 /* Set debug_fork then attach to the child while it sleeps, to debug. */
440 static int debug_fork
= 0;
442 /* It is generally good practice to flush any possible pending stdio
443 output prior to doing a fork, to avoid the possibility of both the
444 parent and child flushing the same data after the fork. */
446 gdb_flush (gdb_stdout
);
447 gdb_flush (gdb_stderr
);
449 /* Open the semaphore pipes.
451 status
= pipe (handoff_semaphore
);
453 error ("error getting pipe for handoff semaphore");
455 /* Clone the debugger. */
456 #if defined(USG) && !defined(HAVE_VFORK)
457 debugger_pid
= fork ();
460 debugger_pid
= fork ();
462 debugger_pid
= vfork ();
465 if (debugger_pid
< 0)
466 perror_with_name ("fork");
468 /* Are we the original debugger? If so, we must relinquish all claims
470 if (debugger_pid
!= 0)
472 char signal_spelling
[100]; /* Arbitrary but sufficient length */
474 /* Detach from CHILD_PID. Deliver a "stop" signal when we do, though,
475 so that it remains stopped until the clone debugger can attach
478 detach_breakpoints (child_pid
);
480 sprintf (signal_spelling
, "%d", target_signal_to_host (TARGET_SIGNAL_STOP
));
481 target_require_detach (child_pid
, signal_spelling
, 1);
483 /* Notify the clone debugger that it should attach to CHILD_PID. */
484 write (handoff_semaphore
[SEM_TALK
], &talk_value
, sizeof (talk_value
));
489 /* We're the child. */
495 /* The child (i.e., the cloned debugger) must now attach to
496 CHILD_PID. inferior_pid is presently set to the parent process
497 of the fork, while CHILD_PID should be the child process of the
500 Wait until the original debugger relinquishes control of CHILD_PID,
503 read (handoff_semaphore
[SEM_LISTEN
], &listen_value
, sizeof (listen_value
));
505 /* Note that we DON'T want to actually detach from inferior_pid,
506 because that would allow it to run free. The original
507 debugger wants to retain control of the process. So, we
508 just reset inferior_pid to CHILD_PID, and then ensure that all
509 breakpoints are really set in CHILD_PID.
511 target_mourn_inferior ();
513 /* Ask the tty subsystem to switch to the one we specified earlier
514 (or to share the current terminal, if none was specified). */
519 sprintf(pid_spelling
, "%d", child_pid
);
520 target_require_attach (pid_spelling
, 1);
522 /* Perform any necessary cleanup, after attachment. (This form
523 of attaching can behave differently on some targets than the
524 standard method, where a process formerly not under debugger
525 control was suddenly attached to..)
527 target_post_follow_inferior_by_clone ();
532 /* Discard the handoff sempahore. */
533 (void) close (handoff_semaphore
[SEM_LISTEN
]);
534 (void) close (handoff_semaphore
[SEM_TALK
]);
537 /* Accept NTRAPS traps from the inferior. */
540 startup_inferior (ntraps
)
543 int pending_execs
= ntraps
;
544 int terminal_initted
;
546 /* The process was started by the fork that created it,
547 but it will have stopped one instruction after execing the shell.
548 Here we must get it up to actual execution of the real program. */
550 clear_proceed_status ();
552 init_wait_for_inferior ();
554 terminal_initted
= 0;
556 if (STARTUP_WITH_SHELL
)
557 inferior_ignoring_startup_exec_events
= ntraps
;
559 inferior_ignoring_startup_exec_events
= 0;
560 inferior_ignoring_leading_exec_events
=
561 target_reported_exec_events_per_exec_call () - 1;
563 #ifdef STARTUP_INFERIOR
564 STARTUP_INFERIOR (pending_execs
);
568 stop_soon_quietly
= 1; /* Make wait_for_inferior be quiet */
569 wait_for_inferior ();
570 if (stop_signal
!= TARGET_SIGNAL_TRAP
)
572 /* Let shell child handle its own signals in its own way */
573 /* FIXME, what if child has exit()ed? Must exit loop somehow */
574 resume (0, stop_signal
);
578 /* We handle SIGTRAP, however; it means child did an exec. */
579 if (!terminal_initted
)
581 /* Now that the child has exec'd we know it has already set its
582 process group. On POSIX systems, tcsetpgrp will fail with
583 EPERM if we try it before the child's setpgid. */
585 /* Set up the "saved terminal modes" of the inferior
586 based on what modes we are starting it with. */
587 target_terminal_init ();
589 /* Install inferior's terminal modes. */
590 target_terminal_inferior ();
592 terminal_initted
= 1;
595 pending_execs
= pending_execs
- 1;
596 if (0 == pending_execs
)
599 resume (0, TARGET_SIGNAL_0
); /* Just make it go on */
602 #endif /* STARTUP_INFERIOR */
603 stop_soon_quietly
= 0;