blob: b47019dcc00cfcbb2fb5cd2594e2faaadeef4dd1 [file] [log] [blame]
/* Fork a Unix child process, and set up to debug it, for GDB.
Copyright (C) 1990-1996, 1998-2001, 2004-2012 Free Software
Foundation, Inc.
Contributed by Cygnus Support.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <>. */
#include "defs.h"
#include "gdb_string.h"
#include "inferior.h"
#include "terminal.h"
#include "target.h"
#include "gdb_wait.h"
#include "gdb_vfork.h"
#include "gdbcore.h"
#include "terminal.h"
#include "gdbthread.h"
#include "command.h" /* for dont_repeat () */
#include "gdbcmd.h"
#include "solib.h"
#include <signal.h>
/* This just gets used as a default if we can't find SHELL. */
#define SHELL_FILE "/bin/sh"
extern char **environ;
static char *exec_wrapper;
/* Break up SCRATCH into an argument vector suitable for passing to
execvp and store it in ARGV. E.g., on "run a b c d" this routine
would get as input the string "a b c d", and as output it would
fill in ARGV with the four arguments "a", "b", "c", "d". */
static void
breakup_args (char *scratch, char **argv)
char *cp = scratch, *tmp;
for (;;)
/* Scan past leading separators */
while (*cp == ' ' || *cp == '\t' || *cp == '\n')
/* Break if at end of string. */
if (*cp == '\0')
/* Take an arg. */
*argv++ = cp;
/* Scan for next arg separator. */
tmp = strchr (cp, ' ');
if (tmp == NULL)
tmp = strchr (cp, '\t');
if (tmp == NULL)
tmp = strchr (cp, '\n');
/* No separators => end of string => break. */
if (tmp == NULL)
cp = tmp;
/* Replace the separator with a terminator. */
*cp++ = '\0';
/* Null-terminate the vector. */
*argv = NULL;
/* When executing a command under the given shell, return non-zero if
the '!' character should be escaped when embedded in a quoted
command-line argument. */
static int
escape_bang_in_quoted_argument (const char *shell_file)
const int shell_file_len = strlen (shell_file);
/* Bang should be escaped only in C Shells. For now, simply check
that the shell name ends with 'csh', which covers at least csh
and tcsh. This should be good enough for now. */
if (shell_file_len < 3)
return 0;
if (shell_file[shell_file_len - 3] == 'c'
&& shell_file[shell_file_len - 2] == 's'
&& shell_file[shell_file_len - 1] == 'h')
return 1;
return 0;
/* Start an inferior Unix child process and sets inferior_ptid to its
pid. EXEC_FILE is the file to run. ALLARGS is a string containing
the arguments to the program. ENV is the environment vector to
pass. SHELL_FILE is the shell file, or NULL if we should pick
one. EXEC_FUN is the exec(2) function to use, or NULL for the default
one. */
/* This function is NOT reentrant. Some of the variables have been
made static to ensure that they survive the vfork call. */
fork_inferior (char *exec_file_arg, char *allargs, char **env,
void (*traceme_fun) (void), void (*init_trace_fun) (int),
void (*pre_trace_fun) (void), char *shell_file_arg,
void (*exec_fun)(const char *file, char * const *argv,
char * const *env))
int pid;
static char default_shell_file[] = SHELL_FILE;
/* Set debug_fork then attach to the child while it sleeps, to debug. */
static int debug_fork = 0;
/* This is set to the result of setpgrp, which if vforked, will be visible
to you in the parent process. It's only used by humans for debugging. */
static int debug_setpgrp = 657473;
static char *shell_file;
static char *exec_file;
char **save_our_env;
int shell = 0;
static char **argv;
const char *inferior_io_terminal = get_inferior_io_terminal ();
struct inferior *inf;
int i;
int save_errno;
/* If no exec file handed to us, get it from the exec-file command
-- with a good, common error message if none is specified. */
exec_file = exec_file_arg;
if (exec_file == 0)
exec_file = get_exec_file (1);
/* STARTUP_WITH_SHELL is defined in inferior.h. If 0,e we'll just
do a fork/exec, no shell, so don't bother figuring out what
shell. */
shell_file = shell_file_arg;
/* Figure out what shell to start up the user program under. */
if (shell_file == NULL)
shell_file = getenv ("SHELL");
if (shell_file == NULL)
shell_file = default_shell_file;
shell = 1;
if (!shell)
/* We're going to call execvp. Create argument vector.
Calculate an upper bound on the length of the vector by
assuming that every other character is a separate
argument. */
int argc = (strlen (allargs) + 1) / 2 + 2;
argv = (char **) alloca (argc * sizeof (*argv));
argv[0] = exec_file;
breakup_args (allargs, &argv[1]);
/* We're going to call a shell. */
char *shell_command;
int len;
char *p;
int need_to_quote;
const int escape_bang = escape_bang_in_quoted_argument (shell_file);
/* Multiplying the length of exec_file by 4 is to account for the
fact that it may expand when quoted; it is a worst-case number
based on every character being '. */
len = 5 + 4 * strlen (exec_file) + 1 + strlen (allargs) + 1 + /*slop */ 12;
if (exec_wrapper)
len += strlen (exec_wrapper) + 1;
shell_command = (char *) alloca (len);
shell_command[0] = '\0';
strcat (shell_command, "exec ");
/* Add any exec wrapper. That may be a program name with arguments, so
the user must handle quoting. */
if (exec_wrapper)
strcat (shell_command, exec_wrapper);
strcat (shell_command, " ");
/* Now add exec_file, quoting as necessary. */
/* Quoting in this style is said to work with all shells. But
csh on IRIX 4.0.1 can't deal with it. So we only quote it if
we need to. */
p = exec_file;
while (1)
switch (*p)
case '\'':
case '!':
case '"':
case '(':
case ')':
case '$':
case '&':
case ';':
case '<':
case '>':
case ' ':
case '\n':
case '\t':
need_to_quote = 1;
goto end_scan;
case '\0':
need_to_quote = 0;
goto end_scan;
if (need_to_quote)
strcat (shell_command, "'");
for (p = exec_file; *p != '\0'; ++p)
if (*p == '\'')
strcat (shell_command, "'\\''");
else if (*p == '!' && escape_bang)
strcat (shell_command, "\\!");
strncat (shell_command, p, 1);
strcat (shell_command, "'");
strcat (shell_command, exec_file);
strcat (shell_command, " ");
strcat (shell_command, allargs);
/* If we decided above to start up with a shell, we exec the
shell, "-c" says to interpret the next arg as a shell command
to execute, and this command is "exec <target-program>
<args>". */
argv = (char **) alloca (4 * sizeof (char *));
argv[0] = shell_file;
argv[1] = "-c";
argv[2] = shell_command;
argv[3] = (char *) 0;
/* Retain a copy of our environment variables, since the child will
replace the value of environ and if we're vforked, we have to
restore it. */
save_our_env = environ;
/* Tell the terminal handling subsystem what tty we plan to run on;
it will just record the information for later. */
new_tty_prefork (inferior_io_terminal);
/* It is generally good practice to flush any possible pending stdio
output prior to doing a fork, to avoid the possibility of both
the parent and child flushing the same data after the fork. */
gdb_flush (gdb_stdout);
gdb_flush (gdb_stderr);
/* If there's any initialization of the target layers that must
happen to prepare to handle the child we're about fork, do it
now... */
if (pre_trace_fun != NULL)
(*pre_trace_fun) ();
/* Create the child process. Since the child process is going to
exec(3) shortly afterwards, try to reduce the overhead by
calling vfork(2). However, if PRE_TRACE_FUN is non-null, it's
likely that this optimization won't work since there's too much
work to do between the vfork(2) and the exec(3). This is known
to be the case on ttrace(2)-based HP-UX, where some handshaking
between parent and child needs to happen between fork(2) and
exec(2). However, since the parent is suspended in the vforked
state, this doesn't work. Also note that the vfork(2) call might
actually be a call to fork(2) due to the fact that autoconf will
``#define vfork fork'' on certain platforms. */
if (pre_trace_fun || debug_fork)
pid = fork ();
pid = vfork ();
if (pid < 0)
perror_with_name (("vfork"));
if (pid == 0)
if (debug_fork)
sleep (debug_fork);
/* Create a new session for the inferior process, if necessary.
It will also place the inferior in a separate process group. */
if (create_tty_session () <= 0)
/* No session was created, but we still want to run the inferior
in a separate process group. */
debug_setpgrp = gdb_setpgid ();
if (debug_setpgrp == -1)
perror (_("setpgrp failed in child"));
/* Ask the tty subsystem to switch to the one we specified
earlier (or to share the current terminal, if none was
specified). */
new_tty ();
/* Changing the signal handlers for the inferior after
a vfork can also change them for the superior, so we don't mess
with signals here. See comments in
initialize_signals for how we get the right signal handlers
for the inferior. */
/* "Trace me, Dr. Memory!" */
(*traceme_fun) ();
/* The call above set this process (the "child") as debuggable
by the original gdb process (the "parent"). Since processes
(unlike people) can have only one parent, if you are debugging
gdb itself (and your debugger is thus _already_ the
controller/parent for this child), code from here on out is
undebuggable. Indeed, you probably got an error message
saying "not parent". Sorry; you'll have to use print
statements! */
/* There is no execlpe call, so we have to set the environment
for our child in the global variable. If we've vforked, this
clobbers the parent, but environ is restored a few lines down
in the parent. By the way, yes we do need to look down the
path to find $SHELL. Rich Pixley says so, and I agree. */
environ = env;
if (exec_fun != NULL)
(*exec_fun) (argv[0], argv, env);
execvp (argv[0], argv);
/* If we get here, it's an error. */
save_errno = errno;
fprintf_unfiltered (gdb_stderr, "Cannot exec %s", exec_file);
for (i = 1; argv[i] != NULL; i++)
fprintf_unfiltered (gdb_stderr, " %s", argv[i]);
fprintf_unfiltered (gdb_stderr, ".\n");
fprintf_unfiltered (gdb_stderr, "Error: %s\n",
safe_strerror (save_errno));
gdb_flush (gdb_stderr);
_exit (0177);
/* Restore our environment in case a vforked child clob'd it. */
environ = save_our_env;
if (!have_inferiors ())
init_thread_list ();
inf = current_inferior ();
inferior_appeared (inf, pid);
/* Needed for wait_for_inferior stuff below. */
inferior_ptid = pid_to_ptid (pid);
new_tty_postfork ();
/* We have something that executes now. We'll be running through
the shell at this point, but the pid shouldn't change. Targets
supporting MT should fill this task's ptid with more data as soon
as they can. */
add_thread_silent (inferior_ptid);
/* Now that we have a child process, make it our target, and
initialize anything target-vector-specific that needs
initializing. */
if (init_trace_fun)
(*init_trace_fun) (pid);
/* We are now in the child process of interest, having exec'd the
correct program, and are poised at the first instruction of the
new program. */
return pid;
/* Accept NTRAPS traps from the inferior. */
startup_inferior (int ntraps)
int pending_execs = ntraps;
int terminal_initted = 0;
ptid_t resume_ptid;
if (target_supports_multi_process ())
resume_ptid = pid_to_ptid (ptid_get_pid (inferior_ptid));
resume_ptid = minus_one_ptid;
/* The process was started by the fork that created it, but it will
have stopped one instruction after execing the shell. Here we
must get it up to actual execution of the real program. */
if (exec_wrapper)
while (1)
enum gdb_signal resume_signal = GDB_SIGNAL_0;
ptid_t event_ptid;
struct target_waitstatus ws;
memset (&ws, 0, sizeof (ws));
event_ptid = target_wait (resume_ptid, &ws, 0);
/* The inferior didn't really stop, keep waiting. */
switch (ws.kind)
/* Ignore gracefully during startup of the inferior. */
switch_to_thread (event_ptid);
target_terminal_ours ();
target_mourn_inferior ();
error (_("During startup program terminated with signal %s, %s."),
gdb_signal_to_name (ws.value.sig),
gdb_signal_to_string (ws.value.sig));
target_terminal_ours ();
target_mourn_inferior ();
if (ws.value.integer)
error (_("During startup program exited with code %d."),
error (_("During startup program exited normally."));
/* Handle EXEC signals as if they were SIGTRAP signals. */
xfree (ws.value.execd_pathname);
resume_signal = GDB_SIGNAL_TRAP;
switch_to_thread (event_ptid);
resume_signal = ws.value.sig;
switch_to_thread (event_ptid);
if (resume_signal != GDB_SIGNAL_TRAP)
/* Let shell child handle its own signals in its own way. */
target_resume (resume_ptid, 0, resume_signal);
/* We handle SIGTRAP, however; it means child did an exec. */
if (!terminal_initted)
/* Now that the child has exec'd we know it has already
set its process group. On POSIX systems, tcsetpgrp
will fail with EPERM if we try it before the child's
setpgid. */
/* Set up the "saved terminal modes" of the inferior
based on what modes we are starting it with. */
target_terminal_init ();
/* Install inferior's terminal modes. */
target_terminal_inferior ();
terminal_initted = 1;
if (--pending_execs == 0)
/* Just make it go on. */
target_resume (resume_ptid, 0, GDB_SIGNAL_0);
/* Mark all threads non-executing. */
set_executing (resume_ptid, 0);
/* Implement the "unset exec-wrapper" command. */
static void
unset_exec_wrapper_command (char *args, int from_tty)
xfree (exec_wrapper);
exec_wrapper = NULL;
/* Provide a prototype to silence -Wmissing-prototypes. */
extern initialize_file_ftype _initialize_fork_child;
_initialize_fork_child (void)
add_setshow_filename_cmd ("exec-wrapper", class_run, &exec_wrapper, _("\
Set a wrapper for running programs.\n\
The wrapper prepares the system and environment for the new program."),
Show the wrapper for running programs."), NULL,
&setlist, &showlist);
add_cmd ("exec-wrapper", class_run, unset_exec_wrapper_command,
_("Disable use of an execution wrapper."),