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_ptid 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(). */
98 /* This function is NOT-REENTRANT. Some of the variables have been
99 made static to ensure that they survive the vfork() call. */
102 fork_inferior (char *exec_file_arg, char *allargs, char **env,
103 void (*traceme_fun) (void), void (*init_trace_fun) (int),
104 void (*pre_trace_fun) (void), char *shell_file_arg)
108 static char default_shell_file[] = SHELL_FILE;
110 /* Set debug_fork then attach to the child while it sleeps, to debug. */
111 static int debug_fork = 0;
112 /* This is set to the result of setpgrp, which if vforked, will be visible
113 to you in the parent process. It's only used by humans for debugging. */
114 static int debug_setpgrp = 657473;
115 static char *shell_file;
116 static char *exec_file;
121 /* If no exec file handed to us, get it from the exec-file command -- with
122 a good, common error message if none is specified. */
123 exec_file = exec_file_arg;
125 exec_file = get_exec_file (1);
127 /* STARTUP_WITH_SHELL is defined in inferior.h.
128 * If 0, we'll just do a fork/exec, no shell, so don't
129 * bother figuring out what shell.
131 shell_file = shell_file_arg;
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
213 strcat (shell_command, "'");
214 for (p = exec_file; *p != '\0'; ++p)
217 strcat (shell_command, "'\\''");
219 strcat (shell_command, "\\!");
221 strncat (shell_command, p, 1);
223 strcat (shell_command, "'");
226 strcat (shell_command, exec_file);
228 strcat (shell_command, " ");
229 strcat (shell_command, allargs);
233 /* exec is said to fail if the executable is open. */
236 /* Retain a copy of our environment variables, since the child will
237 replace the value of environ and if we're vforked, we have to
239 save_our_env = environ;
241 /* Tell the terminal handling subsystem what tty we plan to run on;
242 it will just record the information for later. */
244 new_tty_prefork (inferior_io_terminal);
246 /* It is generally good practice to flush any possible pending stdio
247 output prior to doing a fork, to avoid the possibility of both the
248 parent and child flushing the same data after the fork. */
250 gdb_flush (gdb_stdout);
251 gdb_flush (gdb_stderr);
253 /* If there's any initialization of the target layers that must happen
254 to prepare to handle the child we're about fork, do it now...
256 if (pre_trace_fun != NULL)
259 /* Create the child process. Note that the apparent call to vfork()
260 below *might* actually be a call to fork() due to the fact that
261 autoconf will ``#define vfork fork'' on certain platforms. */
268 perror_with_name ("vfork");
275 /* Run inferior in a separate process group. */
276 debug_setpgrp = gdb_setpgid ();
277 if (debug_setpgrp == -1)
278 perror ("setpgrp failed in child");
280 /* Ask the tty subsystem to switch to the one we specified earlier
281 (or to share the current terminal, if none was specified). */
285 /* Changing the signal handlers for the inferior after
286 a vfork can also change them for the superior, so we don't mess
287 with signals here. See comments in
288 initialize_signals for how we get the right signal handlers
291 /* "Trace me, Dr. Memory!" */
293 /* The call above set this process (the "child") as debuggable
294 * by the original gdb process (the "parent"). Since processes
295 * (unlike people) can have only one parent, if you are
296 * debugging gdb itself (and your debugger is thus _already_ the
297 * controller/parent for this child), code from here on out
298 * is undebuggable. Indeed, you probably got an error message
299 * saying "not parent". Sorry--you'll have to use print statements!
302 /* There is no execlpe call, so we have to set the environment
303 for our child in the global variable. If we've vforked, this
304 clobbers the parent, but environ is restored a few lines down
305 in the parent. By the way, yes we do need to look down the
306 path to find $SHELL. Rich Pixley says so, and I agree. */
309 /* If we decided above to start up with a shell,
311 * "-c" says to interpret the next arg as a shell command
312 * to execute, and this command is "exec <target-program> <args>".
313 * "-f" means "fast startup" to the c-shell, which means
314 * don't do .cshrc file. Doing .cshrc may cause fork/exec
315 * events which will confuse debugger start-up code.
319 execlp (shell_file, shell_file, "-c", shell_command, (char *) 0);
321 /* If we get here, it's an error */
322 fprintf_unfiltered (gdb_stderr, "Cannot exec %s: %s.\n", shell_file,
323 safe_strerror (errno));
324 gdb_flush (gdb_stderr);
329 /* Otherwise, we directly exec the target program with execvp. */
333 execvp (exec_file, argv);
335 /* If we get here, it's an error */
336 errstring = safe_strerror (errno);
337 fprintf_unfiltered (gdb_stderr, "Cannot exec %s ", exec_file);
340 while (argv[i] != NULL)
343 fprintf_unfiltered (gdb_stderr, " ");
344 fprintf_unfiltered (gdb_stderr, "%s", argv[i]);
347 fprintf_unfiltered (gdb_stderr, ".\n");
348 /* This extra info seems to be useless
349 fprintf_unfiltered (gdb_stderr, "Got error %s.\n", errstring);
351 gdb_flush (gdb_stderr);
356 /* Restore our environment in case a vforked child clob'd it. */
357 environ = save_our_env;
361 inferior_ptid = pid_to_ptid (pid); /* Needed for wait_for_inferior stuff below */
363 /* Now that we have a child process, make it our target, and
364 initialize anything target-vector-specific that needs initializing. */
366 (*init_trace_fun) (pid);
368 /* We are now in the child process of interest, having exec'd the
369 correct program, and are poised at the first instruction of the
372 /* Allow target dependent code to play with the new process. This might be
373 used to have target-specific code initialize a variable in the new process
374 prior to executing the first instruction. */
375 TARGET_CREATE_INFERIOR_HOOK (pid);
377 #ifdef SOLIB_CREATE_INFERIOR_HOOK
378 SOLIB_CREATE_INFERIOR_HOOK (pid);
382 /* Accept NTRAPS traps from the inferior. */
385 startup_inferior (int ntraps)
387 int pending_execs = ntraps;
388 int terminal_initted;
390 /* The process was started by the fork that created it,
391 but it will have stopped one instruction after execing the shell.
392 Here we must get it up to actual execution of the real program. */
394 clear_proceed_status ();
396 init_wait_for_inferior ();
398 terminal_initted = 0;
400 if (STARTUP_WITH_SHELL)
401 inferior_ignoring_startup_exec_events = ntraps;
403 inferior_ignoring_startup_exec_events = 0;
404 inferior_ignoring_leading_exec_events =
405 target_reported_exec_events_per_exec_call () - 1;
407 #ifdef STARTUP_INFERIOR
408 STARTUP_INFERIOR (pending_execs);
412 /* Make wait_for_inferior be quiet */
413 stop_soon_quietly = STOP_QUIETLY;
414 wait_for_inferior ();
415 if (stop_signal != TARGET_SIGNAL_TRAP)
417 /* Let shell child handle its own signals in its own way */
418 /* FIXME, what if child has exit()ed? Must exit loop somehow */
419 resume (0, stop_signal);
423 /* We handle SIGTRAP, however; it means child did an exec. */
424 if (!terminal_initted)
426 /* Now that the child has exec'd we know it has already set its
427 process group. On POSIX systems, tcsetpgrp will fail with
428 EPERM if we try it before the child's setpgid. */
430 /* Set up the "saved terminal modes" of the inferior
431 based on what modes we are starting it with. */
432 target_terminal_init ();
434 /* Install inferior's terminal modes. */
435 target_terminal_inferior ();
437 terminal_initted = 1;
440 pending_execs = pending_execs - 1;
441 if (0 == pending_execs)
444 resume (0, TARGET_SIGNAL_0); /* Just make it go on */
447 #endif /* STARTUP_INFERIOR */
448 stop_soon_quietly = NO_STOP_QUIETLY;