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, 2009, 2010, 2011
5 Free Software Foundation, Inc.
7 Contributed by Cygnus Support.
9 This file is part of GDB.
11 This program is free software; you can redistribute it and/or modify
12 it under the terms of the GNU General Public License as published by
13 the Free Software Foundation; either version 3 of the License, or
14 (at your option) any later version.
16 This program is distributed in the hope that it will be useful,
17 but WITHOUT ANY WARRANTY; without even the implied warranty of
18 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 GNU General Public License for more details.
21 You should have received a copy of the GNU General Public License
22 along with this program. If not, see <http://www.gnu.org/licenses/>. */
25 #include "gdb_string.h"
30 #include "gdb_vfork.h"
33 #include "gdbthread.h"
34 #include "command.h" /* for dont_repeat () */
40 /* This just gets used as a default if we can't find SHELL. */
41 #define SHELL_FILE "/bin/sh"
43 extern char **environ
;
45 static char *exec_wrapper
;
47 /* Break up SCRATCH into an argument vector suitable for passing to
48 execvp and store it in ARGV. E.g., on "run a b c d" this routine
49 would get as input the string "a b c d", and as output it would
50 fill in ARGV with the four arguments "a", "b", "c", "d". */
53 breakup_args (char *scratch
, char **argv
)
55 char *cp
= scratch
, *tmp
;
59 /* Scan past leading separators */
60 while (*cp
== ' ' || *cp
== '\t' || *cp
== '\n')
63 /* Break if at end of string. */
70 /* Scan for next arg separator. */
71 tmp
= strchr (cp
, ' ');
73 tmp
= strchr (cp
, '\t');
75 tmp
= strchr (cp
, '\n');
77 /* No separators => end of string => break. */
82 /* Replace the separator with a terminator. */
86 /* Null-terminate the vector. */
90 /* When executing a command under the given shell, return non-zero if
91 the '!' character should be escaped when embedded in a quoted
92 command-line argument. */
95 escape_bang_in_quoted_argument (const char *shell_file
)
97 const int shell_file_len
= strlen (shell_file
);
99 /* Bang should be escaped only in C Shells. For now, simply check
100 that the shell name ends with 'csh', which covers at least csh
101 and tcsh. This should be good enough for now. */
103 if (shell_file_len
< 3)
106 if (shell_file
[shell_file_len
- 3] == 'c'
107 && shell_file
[shell_file_len
- 2] == 's'
108 && shell_file
[shell_file_len
- 1] == 'h')
114 /* Start an inferior Unix child process and sets inferior_ptid to its
115 pid. EXEC_FILE is the file to run. ALLARGS is a string containing
116 the arguments to the program. ENV is the environment vector to
117 pass. SHELL_FILE is the shell file, or NULL if we should pick
120 /* This function is NOT reentrant. Some of the variables have been
121 made static to ensure that they survive the vfork call. */
124 fork_inferior (char *exec_file_arg
, char *allargs
, char **env
,
125 void (*traceme_fun
) (void), void (*init_trace_fun
) (int),
126 void (*pre_trace_fun
) (void), char *shell_file_arg
)
130 static char default_shell_file
[] = SHELL_FILE
;
132 /* Set debug_fork then attach to the child while it sleeps, to debug. */
133 static int debug_fork
= 0;
134 /* This is set to the result of setpgrp, which if vforked, will be visible
135 to you in the parent process. It's only used by humans for debugging. */
136 static int debug_setpgrp
= 657473;
137 static char *shell_file
;
138 static char *exec_file
;
142 const char *inferior_io_terminal
= get_inferior_io_terminal ();
143 struct inferior
*inf
;
145 /* If no exec file handed to us, get it from the exec-file command
146 -- with a good, common error message if none is specified. */
147 exec_file
= exec_file_arg
;
149 exec_file
= get_exec_file (1);
151 /* STARTUP_WITH_SHELL is defined in inferior.h. If 0,e we'll just
152 do a fork/exec, no shell, so don't bother figuring out what
154 shell_file
= shell_file_arg
;
155 if (STARTUP_WITH_SHELL
)
157 /* Figure out what shell to start up the user program under. */
158 if (shell_file
== NULL
)
159 shell_file
= getenv ("SHELL");
160 if (shell_file
== NULL
)
161 shell_file
= default_shell_file
;
165 /* Multiplying the length of exec_file by 4 is to account for the
166 fact that it may expand when quoted; it is a worst-case number
167 based on every character being '. */
168 len
= 5 + 4 * strlen (exec_file
) + 1 + strlen (allargs
) + 1 + /*slop */ 12;
170 len
+= strlen (exec_wrapper
) + 1;
172 shell_command
= (char *) alloca (len
);
173 shell_command
[0] = '\0';
177 /* We're going to call execvp. Create argument vector.
178 Calculate an upper bound on the length of the vector by
179 assuming that every other character is a separate
181 int argc
= (strlen (allargs
) + 1) / 2 + 2;
183 argv
= (char **) xmalloc (argc
* sizeof (*argv
));
185 breakup_args (allargs
, &argv
[1]);
189 /* We're going to call a shell. */
193 const int escape_bang
= escape_bang_in_quoted_argument (shell_file
);
195 strcat (shell_command
, "exec ");
197 /* Add any exec wrapper. That may be a program name with arguments, so
198 the user must handle quoting. */
201 strcat (shell_command
, exec_wrapper
);
202 strcat (shell_command
, " ");
205 /* Now add exec_file, quoting as necessary. */
207 /* Quoting in this style is said to work with all shells. But
208 csh on IRIX 4.0.1 can't deal with it. So we only quote it if
243 strcat (shell_command
, "'");
244 for (p
= exec_file
; *p
!= '\0'; ++p
)
247 strcat (shell_command
, "'\\''");
248 else if (*p
== '!' && escape_bang
)
249 strcat (shell_command
, "\\!");
251 strncat (shell_command
, p
, 1);
253 strcat (shell_command
, "'");
256 strcat (shell_command
, exec_file
);
258 strcat (shell_command
, " ");
259 strcat (shell_command
, allargs
);
262 /* On some systems an exec will fail if the executable is open. */
265 /* Retain a copy of our environment variables, since the child will
266 replace the value of environ and if we're vforked, we have to
268 save_our_env
= environ
;
270 /* Tell the terminal handling subsystem what tty we plan to run on;
271 it will just record the information for later. */
272 new_tty_prefork (inferior_io_terminal
);
274 /* It is generally good practice to flush any possible pending stdio
275 output prior to doing a fork, to avoid the possibility of both
276 the parent and child flushing the same data after the fork. */
277 gdb_flush (gdb_stdout
);
278 gdb_flush (gdb_stderr
);
280 /* If there's any initialization of the target layers that must
281 happen to prepare to handle the child we're about fork, do it
283 if (pre_trace_fun
!= NULL
)
286 /* Create the child process. Since the child process is going to
287 exec(3) shortly afterwards, try to reduce the overhead by
288 calling vfork(2). However, if PRE_TRACE_FUN is non-null, it's
289 likely that this optimization won't work since there's too much
290 work to do between the vfork(2) and the exec(3). This is known
291 to be the case on ttrace(2)-based HP-UX, where some handshaking
292 between parent and child needs to happen between fork(2) and
293 exec(2). However, since the parent is suspended in the vforked
294 state, this doesn't work. Also note that the vfork(2) call might
295 actually be a call to fork(2) due to the fact that autoconf will
296 ``#define vfork fork'' on certain platforms. */
297 if (pre_trace_fun
|| debug_fork
)
303 perror_with_name (("vfork"));
310 /* Create a new session for the inferior process, if necessary.
311 It will also place the inferior in a separate process group. */
312 if (create_tty_session () <= 0)
314 /* No session was created, but we still want to run the inferior
315 in a separate process group. */
316 debug_setpgrp
= gdb_setpgid ();
317 if (debug_setpgrp
== -1)
318 perror (_("setpgrp failed in child"));
321 /* Ask the tty subsystem to switch to the one we specified
322 earlier (or to share the current terminal, if none was
326 /* Changing the signal handlers for the inferior after
327 a vfork can also change them for the superior, so we don't mess
328 with signals here. See comments in
329 initialize_signals for how we get the right signal handlers
332 /* "Trace me, Dr. Memory!" */
335 /* The call above set this process (the "child") as debuggable
336 by the original gdb process (the "parent"). Since processes
337 (unlike people) can have only one parent, if you are debugging
338 gdb itself (and your debugger is thus _already_ the
339 controller/parent for this child), code from here on out is
340 undebuggable. Indeed, you probably got an error message
341 saying "not parent". Sorry; you'll have to use print
344 /* There is no execlpe call, so we have to set the environment
345 for our child in the global variable. If we've vforked, this
346 clobbers the parent, but environ is restored a few lines down
347 in the parent. By the way, yes we do need to look down the
348 path to find $SHELL. Rich Pixley says so, and I agree. */
351 /* If we decided above to start up with a shell, we exec the
352 shell, "-c" says to interpret the next arg as a shell command
353 to execute, and this command is "exec <target-program>
357 execlp (shell_file
, shell_file
, "-c", shell_command
, (char *) 0);
359 /* If we get here, it's an error. */
360 fprintf_unfiltered (gdb_stderr
, "Cannot exec %s: %s.\n", shell_file
,
361 safe_strerror (errno
));
362 gdb_flush (gdb_stderr
);
367 /* Otherwise, we directly exec the target program with
371 execvp (exec_file
, argv
);
373 /* If we get here, it's an error. */
374 safe_strerror (errno
);
375 fprintf_unfiltered (gdb_stderr
, "Cannot exec %s ", exec_file
);
378 while (argv
[i
] != NULL
)
381 fprintf_unfiltered (gdb_stderr
, " ");
382 fprintf_unfiltered (gdb_stderr
, "%s", argv
[i
]);
385 fprintf_unfiltered (gdb_stderr
, ".\n");
386 gdb_flush (gdb_stderr
);
391 /* Restore our environment in case a vforked child clob'd it. */
392 environ
= save_our_env
;
394 if (!have_inferiors ())
397 inf
= current_inferior ();
399 inferior_appeared (inf
, pid
);
401 /* Needed for wait_for_inferior stuff below. */
402 inferior_ptid
= pid_to_ptid (pid
);
406 /* We have something that executes now. We'll be running through
407 the shell at this point, but the pid shouldn't change. Targets
408 supporting MT should fill this task's ptid with more data as soon
410 add_thread_silent (inferior_ptid
);
412 /* Now that we have a child process, make it our target, and
413 initialize anything target-vector-specific that needs
416 (*init_trace_fun
) (pid
);
418 /* We are now in the child process of interest, having exec'd the
419 correct program, and are poised at the first instruction of the
424 /* Accept NTRAPS traps from the inferior. */
427 startup_inferior (int ntraps
)
429 int pending_execs
= ntraps
;
430 int terminal_initted
= 0;
433 if (target_supports_multi_process ())
434 resume_ptid
= pid_to_ptid (ptid_get_pid (inferior_ptid
));
436 resume_ptid
= minus_one_ptid
;
438 /* The process was started by the fork that created it, but it will
439 have stopped one instruction after execing the shell. Here we
440 must get it up to actual execution of the real program. */
447 enum target_signal resume_signal
= TARGET_SIGNAL_0
;
450 struct target_waitstatus ws
;
451 memset (&ws
, 0, sizeof (ws
));
452 event_ptid
= target_wait (resume_ptid
, &ws
, 0);
454 if (ws
.kind
== TARGET_WAITKIND_IGNORE
)
455 /* The inferior didn't really stop, keep waiting. */
460 case TARGET_WAITKIND_SPURIOUS
:
461 case TARGET_WAITKIND_LOADED
:
462 case TARGET_WAITKIND_FORKED
:
463 case TARGET_WAITKIND_VFORKED
:
464 case TARGET_WAITKIND_SYSCALL_ENTRY
:
465 case TARGET_WAITKIND_SYSCALL_RETURN
:
466 /* Ignore gracefully during startup of the inferior. */
467 switch_to_thread (event_ptid
);
470 case TARGET_WAITKIND_SIGNALLED
:
471 target_terminal_ours ();
472 target_mourn_inferior ();
473 error (_("During startup program terminated with signal %s, %s."),
474 target_signal_to_name (ws
.value
.sig
),
475 target_signal_to_string (ws
.value
.sig
));
478 case TARGET_WAITKIND_EXITED
:
479 target_terminal_ours ();
480 target_mourn_inferior ();
481 if (ws
.value
.integer
)
482 error (_("During startup program exited with code %d."),
485 error (_("During startup program exited normally."));
488 case TARGET_WAITKIND_EXECD
:
489 /* Handle EXEC signals as if they were SIGTRAP signals. */
490 xfree (ws
.value
.execd_pathname
);
491 resume_signal
= TARGET_SIGNAL_TRAP
;
492 switch_to_thread (event_ptid
);
495 case TARGET_WAITKIND_STOPPED
:
496 resume_signal
= ws
.value
.sig
;
497 switch_to_thread (event_ptid
);
501 if (resume_signal
!= TARGET_SIGNAL_TRAP
)
503 /* Let shell child handle its own signals in its own way. */
504 target_resume (resume_ptid
, 0, resume_signal
);
508 /* We handle SIGTRAP, however; it means child did an exec. */
509 if (!terminal_initted
)
511 /* Now that the child has exec'd we know it has already
512 set its process group. On POSIX systems, tcsetpgrp
513 will fail with EPERM if we try it before the child's
516 /* Set up the "saved terminal modes" of the inferior
517 based on what modes we are starting it with. */
518 target_terminal_init ();
520 /* Install inferior's terminal modes. */
521 target_terminal_inferior ();
523 terminal_initted
= 1;
526 if (--pending_execs
== 0)
529 /* Just make it go on. */
530 target_resume (resume_ptid
, 0, TARGET_SIGNAL_0
);
534 /* Mark all threads non-executing. */
535 set_executing (resume_ptid
, 0);
538 /* Implement the "unset exec-wrapper" command. */
541 unset_exec_wrapper_command (char *args
, int from_tty
)
543 xfree (exec_wrapper
);
547 /* Provide a prototype to silence -Wmissing-prototypes. */
548 extern initialize_file_ftype _initialize_fork_child
;
551 _initialize_fork_child (void)
553 add_setshow_filename_cmd ("exec-wrapper", class_run
, &exec_wrapper
, _("\
554 Set a wrapper for running programs.\n\
555 The wrapper prepares the system and environment for the new program."),
557 Show the wrapper for running programs."), NULL
,
559 &setlist
, &showlist
);
561 add_cmd ("exec-wrapper", class_run
, unset_exec_wrapper_command
,
562 _("Disable use of an execution wrapper."),