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
)
129 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 ();
141 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
;
167 /* We're going to call execvp. Create argument vector.
168 Calculate an upper bound on the length of the vector by
169 assuming that every other character is a separate
171 int argc
= (strlen (allargs
) + 1) / 2 + 2;
173 argv
= (char **) alloca (argc
* sizeof (*argv
));
175 breakup_args (allargs
, &argv
[1]);
179 /* We're going to call a shell. */
184 const int escape_bang
= escape_bang_in_quoted_argument (shell_file
);
186 /* Multiplying the length of exec_file by 4 is to account for the
187 fact that it may expand when quoted; it is a worst-case number
188 based on every character being '. */
189 len
= 5 + 4 * strlen (exec_file
) + 1 + strlen (allargs
) + 1 + /*slop */ 12;
191 len
+= strlen (exec_wrapper
) + 1;
193 shell_command
= (char *) alloca (len
);
194 shell_command
[0] = '\0';
196 strcat (shell_command
, "exec ");
198 /* Add any exec wrapper. That may be a program name with arguments, so
199 the user must handle quoting. */
202 strcat (shell_command
, exec_wrapper
);
203 strcat (shell_command
, " ");
206 /* Now add exec_file, quoting as necessary. */
208 /* Quoting in this style is said to work with all shells. But
209 csh on IRIX 4.0.1 can't deal with it. So we only quote it if
244 strcat (shell_command
, "'");
245 for (p
= exec_file
; *p
!= '\0'; ++p
)
248 strcat (shell_command
, "'\\''");
249 else if (*p
== '!' && escape_bang
)
250 strcat (shell_command
, "\\!");
252 strncat (shell_command
, p
, 1);
254 strcat (shell_command
, "'");
257 strcat (shell_command
, exec_file
);
259 strcat (shell_command
, " ");
260 strcat (shell_command
, allargs
);
262 /* If we decided above to start up with a shell, we exec the
263 shell, "-c" says to interpret the next arg as a shell command
264 to execute, and this command is "exec <target-program>
266 argv
= (char **) alloca (4 * sizeof (char *));
267 argv
[0] = shell_file
;
269 argv
[2] = shell_command
;
270 argv
[3] = (char *) 0;
273 /* On some systems an exec will fail if the executable is open. */
276 /* Retain a copy of our environment variables, since the child will
277 replace the value of environ and if we're vforked, we have to
279 save_our_env
= environ
;
281 /* Tell the terminal handling subsystem what tty we plan to run on;
282 it will just record the information for later. */
283 new_tty_prefork (inferior_io_terminal
);
285 /* It is generally good practice to flush any possible pending stdio
286 output prior to doing a fork, to avoid the possibility of both
287 the parent and child flushing the same data after the fork. */
288 gdb_flush (gdb_stdout
);
289 gdb_flush (gdb_stderr
);
291 /* If there's any initialization of the target layers that must
292 happen to prepare to handle the child we're about fork, do it
294 if (pre_trace_fun
!= NULL
)
297 /* Create the child process. Since the child process is going to
298 exec(3) shortly afterwards, try to reduce the overhead by
299 calling vfork(2). However, if PRE_TRACE_FUN is non-null, it's
300 likely that this optimization won't work since there's too much
301 work to do between the vfork(2) and the exec(3). This is known
302 to be the case on ttrace(2)-based HP-UX, where some handshaking
303 between parent and child needs to happen between fork(2) and
304 exec(2). However, since the parent is suspended in the vforked
305 state, this doesn't work. Also note that the vfork(2) call might
306 actually be a call to fork(2) due to the fact that autoconf will
307 ``#define vfork fork'' on certain platforms. */
308 if (pre_trace_fun
|| debug_fork
)
314 perror_with_name (("vfork"));
321 /* Create a new session for the inferior process, if necessary.
322 It will also place the inferior in a separate process group. */
323 if (create_tty_session () <= 0)
325 /* No session was created, but we still want to run the inferior
326 in a separate process group. */
327 debug_setpgrp
= gdb_setpgid ();
328 if (debug_setpgrp
== -1)
329 perror (_("setpgrp failed in child"));
332 /* Ask the tty subsystem to switch to the one we specified
333 earlier (or to share the current terminal, if none was
337 /* Changing the signal handlers for the inferior after
338 a vfork can also change them for the superior, so we don't mess
339 with signals here. See comments in
340 initialize_signals for how we get the right signal handlers
343 /* "Trace me, Dr. Memory!" */
346 /* The call above set this process (the "child") as debuggable
347 by the original gdb process (the "parent"). Since processes
348 (unlike people) can have only one parent, if you are debugging
349 gdb itself (and your debugger is thus _already_ the
350 controller/parent for this child), code from here on out is
351 undebuggable. Indeed, you probably got an error message
352 saying "not parent". Sorry; you'll have to use print
355 /* There is no execlpe call, so we have to set the environment
356 for our child in the global variable. If we've vforked, this
357 clobbers the parent, but environ is restored a few lines down
358 in the parent. By the way, yes we do need to look down the
359 path to find $SHELL. Rich Pixley says so, and I agree. */
362 execvp (argv
[0], argv
);
364 /* If we get here, it's an error. */
366 fprintf_unfiltered (gdb_stderr
, "Cannot exec %s", exec_file
);
367 for (i
= 1; argv
[i
] != NULL
; i
++)
368 fprintf_unfiltered (gdb_stderr
, " %s", argv
[i
]);
369 fprintf_unfiltered (gdb_stderr
, ".\n");
370 fprintf_unfiltered (gdb_stderr
, "Error: %s\n",
371 safe_strerror (save_errno
));
372 gdb_flush (gdb_stderr
);
376 /* Restore our environment in case a vforked child clob'd it. */
377 environ
= save_our_env
;
379 if (!have_inferiors ())
382 inf
= current_inferior ();
384 inferior_appeared (inf
, pid
);
386 /* Needed for wait_for_inferior stuff below. */
387 inferior_ptid
= pid_to_ptid (pid
);
391 /* We have something that executes now. We'll be running through
392 the shell at this point, but the pid shouldn't change. Targets
393 supporting MT should fill this task's ptid with more data as soon
395 add_thread_silent (inferior_ptid
);
397 /* Now that we have a child process, make it our target, and
398 initialize anything target-vector-specific that needs
401 (*init_trace_fun
) (pid
);
403 /* We are now in the child process of interest, having exec'd the
404 correct program, and are poised at the first instruction of the
409 /* Accept NTRAPS traps from the inferior. */
412 startup_inferior (int ntraps
)
414 int pending_execs
= ntraps
;
415 int terminal_initted
= 0;
418 if (target_supports_multi_process ())
419 resume_ptid
= pid_to_ptid (ptid_get_pid (inferior_ptid
));
421 resume_ptid
= minus_one_ptid
;
423 /* The process was started by the fork that created it, but it will
424 have stopped one instruction after execing the shell. Here we
425 must get it up to actual execution of the real program. */
432 enum target_signal resume_signal
= TARGET_SIGNAL_0
;
435 struct target_waitstatus ws
;
436 memset (&ws
, 0, sizeof (ws
));
437 event_ptid
= target_wait (resume_ptid
, &ws
, 0);
439 if (ws
.kind
== TARGET_WAITKIND_IGNORE
)
440 /* The inferior didn't really stop, keep waiting. */
445 case TARGET_WAITKIND_SPURIOUS
:
446 case TARGET_WAITKIND_LOADED
:
447 case TARGET_WAITKIND_FORKED
:
448 case TARGET_WAITKIND_VFORKED
:
449 case TARGET_WAITKIND_SYSCALL_ENTRY
:
450 case TARGET_WAITKIND_SYSCALL_RETURN
:
451 /* Ignore gracefully during startup of the inferior. */
452 switch_to_thread (event_ptid
);
455 case TARGET_WAITKIND_SIGNALLED
:
456 target_terminal_ours ();
457 target_mourn_inferior ();
458 error (_("During startup program terminated with signal %s, %s."),
459 target_signal_to_name (ws
.value
.sig
),
460 target_signal_to_string (ws
.value
.sig
));
463 case TARGET_WAITKIND_EXITED
:
464 target_terminal_ours ();
465 target_mourn_inferior ();
466 if (ws
.value
.integer
)
467 error (_("During startup program exited with code %d."),
470 error (_("During startup program exited normally."));
473 case TARGET_WAITKIND_EXECD
:
474 /* Handle EXEC signals as if they were SIGTRAP signals. */
475 xfree (ws
.value
.execd_pathname
);
476 resume_signal
= TARGET_SIGNAL_TRAP
;
477 switch_to_thread (event_ptid
);
480 case TARGET_WAITKIND_STOPPED
:
481 resume_signal
= ws
.value
.sig
;
482 switch_to_thread (event_ptid
);
486 if (resume_signal
!= TARGET_SIGNAL_TRAP
)
488 /* Let shell child handle its own signals in its own way. */
489 target_resume (resume_ptid
, 0, resume_signal
);
493 /* We handle SIGTRAP, however; it means child did an exec. */
494 if (!terminal_initted
)
496 /* Now that the child has exec'd we know it has already
497 set its process group. On POSIX systems, tcsetpgrp
498 will fail with EPERM if we try it before the child's
501 /* Set up the "saved terminal modes" of the inferior
502 based on what modes we are starting it with. */
503 target_terminal_init ();
505 /* Install inferior's terminal modes. */
506 target_terminal_inferior ();
508 terminal_initted
= 1;
511 if (--pending_execs
== 0)
514 /* Just make it go on. */
515 target_resume (resume_ptid
, 0, TARGET_SIGNAL_0
);
519 /* Mark all threads non-executing. */
520 set_executing (resume_ptid
, 0);
523 /* Implement the "unset exec-wrapper" command. */
526 unset_exec_wrapper_command (char *args
, int from_tty
)
528 xfree (exec_wrapper
);
532 /* Provide a prototype to silence -Wmissing-prototypes. */
533 extern initialize_file_ftype _initialize_fork_child
;
536 _initialize_fork_child (void)
538 add_setshow_filename_cmd ("exec-wrapper", class_run
, &exec_wrapper
, _("\
539 Set a wrapper for running programs.\n\
540 The wrapper prepares the system and environment for the new program."),
542 Show the wrapper for running programs."), NULL
,
544 &setlist
, &showlist
);
546 add_cmd ("exec-wrapper", class_run
, unset_exec_wrapper_command
,
547 _("Disable use of an execution wrapper."),