1 /* Fork a Unix child process, and set up to debug it, for GDB.
3 Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000,
4 2001, 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
6 Contributed by Cygnus Support.
8 This file is part of GDB.
10 This program is free software; you can redistribute it and/or modify
11 it under the terms of the GNU General Public License as published by
12 the Free Software Foundation; either version 3 of the License, or
13 (at your option) any later version.
15 This program is distributed in the hope that it will be useful,
16 but WITHOUT ANY WARRANTY; without even the implied warranty of
17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 GNU General Public License for more details.
20 You should have received a copy of the GNU General Public License
21 along with this program. If not, see <http://www.gnu.org/licenses/>. */
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 () */
39 /* This just gets used as a default if we can't find SHELL. */
40 #define SHELL_FILE "/bin/sh"
42 extern char **environ
;
44 static char *exec_wrapper
;
46 /* Break up SCRATCH into an argument vector suitable for passing to
47 execvp and store it in ARGV. E.g., on "run a b c d" this routine
48 would get as input the string "a b c d", and as output it would
49 fill in ARGV with the four arguments "a", "b", "c", "d". */
52 breakup_args (char *scratch
, char **argv
)
58 /* Scan past leading separators */
59 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 /* Null-terminate the vector. */
88 /* When executing a command under the given shell, return non-zero if
89 the '!' character should be escaped when embedded in a quoted
90 command-line argument. */
93 escape_bang_in_quoted_argument (const char *shell_file
)
95 const int shell_file_len
= strlen (shell_file
);
97 /* Bang should be escaped only in C Shells. For now, simply check
98 that the shell name ends with 'csh', which covers at least csh
99 and tcsh. This should be good enough for now. */
101 if (shell_file_len
< 3)
104 if (shell_file
[shell_file_len
- 3] == 'c'
105 && shell_file
[shell_file_len
- 2] == 's'
106 && shell_file
[shell_file_len
- 1] == 'h')
112 /* Start an inferior Unix child process and sets inferior_ptid to its
113 pid. EXEC_FILE is the file to run. ALLARGS is a string containing
114 the arguments to the program. ENV is the environment vector to
115 pass. SHELL_FILE is the shell file, or NULL if we should pick
118 /* This function is NOT reentrant. Some of the variables have been
119 made static to ensure that they survive the vfork call. */
122 fork_inferior (char *exec_file_arg
, char *allargs
, char **env
,
123 void (*traceme_fun
) (void), void (*init_trace_fun
) (int),
124 void (*pre_trace_fun
) (void), char *shell_file_arg
)
128 static char default_shell_file
[] = SHELL_FILE
;
130 /* Set debug_fork then attach to the child while it sleeps, to debug. */
131 static int debug_fork
= 0;
132 /* This is set to the result of setpgrp, which if vforked, will be visible
133 to you in the parent process. It's only used by humans for debugging. */
134 static int debug_setpgrp
= 657473;
135 static char *shell_file
;
136 static char *exec_file
;
140 const char *inferior_io_terminal
= get_inferior_io_terminal ();
142 /* If no exec file handed to us, get it from the exec-file command
143 -- with a good, common error message if none is specified. */
144 exec_file
= exec_file_arg
;
146 exec_file
= get_exec_file (1);
148 /* STARTUP_WITH_SHELL is defined in inferior.h. If 0,e we'll just
149 do a fork/exec, no shell, so don't bother figuring out what
151 shell_file
= shell_file_arg
;
152 if (STARTUP_WITH_SHELL
)
154 /* Figure out what shell to start up the user program under. */
155 if (shell_file
== NULL
)
156 shell_file
= getenv ("SHELL");
157 if (shell_file
== NULL
)
158 shell_file
= default_shell_file
;
162 /* Multiplying the length of exec_file by 4 is to account for the
163 fact that it may expand when quoted; it is a worst-case number
164 based on every character being '. */
165 len
= 5 + 4 * strlen (exec_file
) + 1 + strlen (allargs
) + 1 + /*slop */ 12;
167 len
+= strlen (exec_wrapper
) + 1;
169 shell_command
= (char *) alloca (len
);
170 shell_command
[0] = '\0';
174 /* We're going to call execvp. Create argument vector.
175 Calculate an upper bound on the length of the vector by
176 assuming that every other character is a separate
178 int argc
= (strlen (allargs
) + 1) / 2 + 2;
179 argv
= (char **) xmalloc (argc
* sizeof (*argv
));
181 breakup_args (allargs
, &argv
[1]);
185 /* We're going to call a shell. */
189 const int escape_bang
= escape_bang_in_quoted_argument (shell_file
);
191 strcat (shell_command
, "exec ");
193 /* Add any exec wrapper. That may be a program name with arguments, so
194 the user must handle quoting. */
197 strcat (shell_command
, exec_wrapper
);
198 strcat (shell_command
, " ");
201 /* Now add exec_file, quoting as necessary. */
203 /* Quoting in this style is said to work with all shells. But
204 csh on IRIX 4.0.1 can't deal with it. So we only quote it if
239 strcat (shell_command
, "'");
240 for (p
= exec_file
; *p
!= '\0'; ++p
)
243 strcat (shell_command
, "'\\''");
244 else if (*p
== '!' && escape_bang
)
245 strcat (shell_command
, "\\!");
247 strncat (shell_command
, p
, 1);
249 strcat (shell_command
, "'");
252 strcat (shell_command
, exec_file
);
254 strcat (shell_command
, " ");
255 strcat (shell_command
, allargs
);
258 /* On some systems an exec will fail if the executable is open. */
261 /* Retain a copy of our environment variables, since the child will
262 replace the value of environ and if we're vforked, we have to
264 save_our_env
= environ
;
266 /* Tell the terminal handling subsystem what tty we plan to run on;
267 it will just record the information for later. */
268 new_tty_prefork (inferior_io_terminal
);
270 /* It is generally good practice to flush any possible pending stdio
271 output prior to doing a fork, to avoid the possibility of both
272 the parent and child flushing the same data after the fork. */
273 gdb_flush (gdb_stdout
);
274 gdb_flush (gdb_stderr
);
276 /* If there's any initialization of the target layers that must
277 happen to prepare to handle the child we're about fork, do it
279 if (pre_trace_fun
!= NULL
)
282 /* Create the child process. Since the child process is going to
283 exec(3) shortly afterwards, try to reduce the overhead by
284 calling vfork(2). However, if PRE_TRACE_FUN is non-null, it's
285 likely that this optimization won't work since there's too much
286 work to do between the vfork(2) and the exec(3). This is known
287 to be the case on ttrace(2)-based HP-UX, where some handshaking
288 between parent and child needs to happen between fork(2) and
289 exec(2). However, since the parent is suspended in the vforked
290 state, this doesn't work. Also note that the vfork(2) call might
291 actually be a call to fork(2) due to the fact that autoconf will
292 ``#define vfork fork'' on certain platforms. */
293 if (pre_trace_fun
|| debug_fork
)
299 perror_with_name (("vfork"));
306 /* Run inferior in a separate process group. */
307 debug_setpgrp
= gdb_setpgid ();
308 if (debug_setpgrp
== -1)
309 perror ("setpgrp failed in child");
311 /* Ask the tty subsystem to switch to the one we specified
312 earlier (or to share the current terminal, if none was
316 /* Changing the signal handlers for the inferior after
317 a vfork can also change them for the superior, so we don't mess
318 with signals here. See comments in
319 initialize_signals for how we get the right signal handlers
322 /* "Trace me, Dr. Memory!" */
325 /* The call above set this process (the "child") as debuggable
326 by the original gdb process (the "parent"). Since processes
327 (unlike people) can have only one parent, if you are debugging
328 gdb itself (and your debugger is thus _already_ the
329 controller/parent for this child), code from here on out is
330 undebuggable. Indeed, you probably got an error message
331 saying "not parent". Sorry; you'll have to use print
334 /* There is no execlpe call, so we have to set the environment
335 for our child in the global variable. If we've vforked, this
336 clobbers the parent, but environ is restored a few lines down
337 in the parent. By the way, yes we do need to look down the
338 path to find $SHELL. Rich Pixley says so, and I agree. */
341 /* If we decided above to start up with a shell, we exec the
342 shell, "-c" says to interpret the next arg as a shell command
343 to execute, and this command is "exec <target-program>
347 execlp (shell_file
, shell_file
, "-c", shell_command
, (char *) 0);
349 /* If we get here, it's an error. */
350 fprintf_unfiltered (gdb_stderr
, "Cannot exec %s: %s.\n", shell_file
,
351 safe_strerror (errno
));
352 gdb_flush (gdb_stderr
);
357 /* Otherwise, we directly exec the target program with
362 execvp (exec_file
, argv
);
364 /* If we get here, it's an error. */
365 errstring
= safe_strerror (errno
);
366 fprintf_unfiltered (gdb_stderr
, "Cannot exec %s ", exec_file
);
369 while (argv
[i
] != NULL
)
372 fprintf_unfiltered (gdb_stderr
, " ");
373 fprintf_unfiltered (gdb_stderr
, "%s", argv
[i
]);
376 fprintf_unfiltered (gdb_stderr
, ".\n");
378 /* This extra info seems to be useless. */
379 fprintf_unfiltered (gdb_stderr
, "Got error %s.\n", errstring
);
381 gdb_flush (gdb_stderr
);
386 /* Restore our environment in case a vforked child clob'd it. */
387 environ
= save_our_env
;
391 /* Needed for wait_for_inferior stuff below. */
392 inferior_ptid
= pid_to_ptid (pid
);
394 /* Now that we have a child process, make it our target, and
395 initialize anything target-vector-specific that needs
397 (*init_trace_fun
) (pid
);
399 /* We are now in the child process of interest, having exec'd the
400 correct program, and are poised at the first instruction of the
404 /* Accept NTRAPS traps from the inferior. */
407 startup_inferior (int ntraps
)
409 int pending_execs
= ntraps
;
410 int terminal_initted
= 0;
412 /* The process was started by the fork that created it, but it will
413 have stopped one instruction after execing the shell. Here we
414 must get it up to actual execution of the real program. */
419 clear_proceed_status ();
421 init_wait_for_inferior ();
423 inferior_ignoring_leading_exec_events
=
424 target_reported_exec_events_per_exec_call () - 1;
428 /* Make wait_for_inferior be quiet. */
429 stop_soon
= STOP_QUIETLY
;
430 wait_for_inferior (1);
431 if (stop_signal
!= TARGET_SIGNAL_TRAP
)
433 /* Let shell child handle its own signals in its own way.
434 FIXME: what if child has exited? Must exit loop
436 resume (0, stop_signal
);
440 /* We handle SIGTRAP, however; it means child did an exec. */
441 if (!terminal_initted
)
443 /* Now that the child has exec'd we know it has already
444 set its process group. On POSIX systems, tcsetpgrp
445 will fail with EPERM if we try it before the child's
448 /* Set up the "saved terminal modes" of the inferior
449 based on what modes we are starting it with. */
450 target_terminal_init ();
452 /* Install inferior's terminal modes. */
453 target_terminal_inferior ();
455 terminal_initted
= 1;
458 if (--pending_execs
== 0)
461 resume (0, TARGET_SIGNAL_0
); /* Just make it go on. */
464 stop_soon
= NO_STOP_QUIETLY
;
467 /* Implement the "unset exec-wrapper" command. */
470 unset_exec_wrapper_command (char *args
, int from_tty
)
472 xfree (exec_wrapper
);
477 _initialize_fork_child (void)
479 add_setshow_filename_cmd ("exec-wrapper", class_run
, &exec_wrapper
, _("\
480 Set a wrapper for running programs.\n\
481 The wrapper prepares the system and environment for the new program."),
483 Show the wrapper for running programs."), NULL
,
485 &setlist
, &showlist
);
487 add_cmd ("exec-wrapper", class_run
, unset_exec_wrapper_command
,
488 _("Disable use of an execution wrapper."),