/* Fork a Unix child process, and set up to debug it, for GDB. Copyright 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000, 2001, 2004 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 2 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 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 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, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ #include "defs.h" #include "gdb_string.h" #include "frame.h" /* required by inferior.h */ #include "inferior.h" #include "target.h" #include "gdb_wait.h" #include "gdb_vfork.h" #include "gdbcore.h" #include "terminal.h" #include "gdbthread.h" #include "gdbcmd.h" #include "command.h" /* for dont_repeat () */ #include "solib.h" #include <signal.h> char *exec_argv0 = NULL; char *exec_pathname = NULL; /* This just gets used as a default if we can't find SHELL. */ #ifndef SHELL_FILE #define SHELL_FILE "/bin/sh" #endif extern char **environ; /* 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; for (;;) { /* Scan past leading separators */ while (*cp == ' ' || *cp == '\t' || *cp == '\n') cp++; /* Break if at end of string. */ if (*cp == '\0') break; /* Take an arg. */ *argv++ = cp; /* Scan for next arg separator */ while (!(*cp == '\0' || *cp == ' ' || *cp == '\t' || *cp == '\n')) { cp++; } /* No separators => end of string => break */ if (*cp == '\0') break; /* 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. */ /* This function is NOT reentrant. Some of the variables have been made static to ensure that they survive the vfork call. */ void 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) { int pid; char *shell_command; static char default_shell_file[] = SHELL_FILE; int len; /* Set debug_fork then attach to the child while it sleeps, to debug. */ static int debug_fork = 1; /* 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 (); /* 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); /* If 0, we'll just do a fork/exec, no shell, so don't * bother figuring out what shell. */ shell_file = shell_file_arg; if (start_with_shell_flag) { /* 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; } /* 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 desired, concat something onto the front of ALLARGS. SHELL_COMMAND is the result. */ #ifdef SHELL_COMMAND_CONCAT shell_command = (char *) alloca (strlen (SHELL_COMMAND_CONCAT) + len); strcpy (shell_command, SHELL_COMMAND_CONCAT); #else shell_command = (char *) alloca (len); shell_command[0] = '\0'; #endif if (!shell) { unsigned int i; char **argt = NULL; argt = buildargv (allargs); if (argt == NULL) { error ("unable to build argument vector for inferior process (out of memory)"); } if ((allargs == NULL) || (allargs[0] == '\0')) argt[0] = NULL; for (i = 0; argt[i] != NULL; i++); argv = (char **) xmalloc ((i + 1 + 1) * (sizeof *argt)); argv[0] = exec_file; if (exec_argv0[0] != '\0') argv[0] = exec_argv0; memcpy (&argv[1], argt, (i + 1) * sizeof (*argt)); /* freeargv (argt); */ #if 0 /* We're going to call execvp. Create argv */ /* Largest case: every other character is a separate arg */ argv = (char **) xmalloc (((strlen (allargs) + 1) / (unsigned) 2 + 2) * sizeof (*argv)); argv[0] = exec_file; breakup_args (allargs, &argv[1]); #endif } else { /* We're going to call a shell. */ /* We're going to call a shell */ /* Now add exec_file, quoting as necessary. */ char *p; int need_to_quote; const int escape_bang = escape_bang_in_quoted_argument (shell_file); strcat (shell_command, "exec "); /* 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; default: break; } ++p; } 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, "\\!"); else strncat (shell_command, p, 1); } strcat (shell_command, "'"); } else strcat (shell_command, exec_file); strcat (shell_command, " "); strcat (shell_command, allargs); } /* On some systems an exec will fail if the executable is open. */ close_exec_file (); /* 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) shortlty 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 (); else pid = vfork (); if (pid < 0) perror_with_name (("vfork")); if (pid == 0) { if (debug_fork) sleep (debug_fork); /* Run 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; /* APPLE LOCAL: gdb is setgid to give it extra special debuggizer powers; we need to drop those privileges before executing the inferior process. */ setgid (getgid ()); /* 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>". "-f" means "fast startup" to the c-shell, which means don't do .cshrc file. Doing .cshrc may cause fork/exec events which will confuse debugger start-up code. */ if (shell) { execlp (shell_file, shell_file, "-c", shell_command, (char *) 0); /* If we get here, it's an error. */ fprintf_unfiltered (gdb_stderr, "Cannot exec %s: %s.\n", shell_file, safe_strerror (errno)); gdb_flush (gdb_stderr); _exit (0177); } else { /* Otherwise, we directly exec the target program with execvp. */ int i; char *errstring; if (exec_pathname[0] != '\0') execvp (exec_pathname, argv); else execvp (exec_file, argv); /* If we get here, it's an error. */ errstring = safe_strerror (errno); fprintf_unfiltered (gdb_stderr, "Cannot exec %s ", exec_file); i = 1; while (argv[i] != NULL) { if (i != 1) fprintf_unfiltered (gdb_stderr, " "); fprintf_unfiltered (gdb_stderr, "%s", argv[i]); i++; } fprintf_unfiltered (gdb_stderr, ".\n"); #if 0 /* This extra info seems to be useless. */ fprintf_unfiltered (gdb_stderr, "Got error %s.\n", errstring); #endif gdb_flush (gdb_stderr); _exit (0177); } } /* Restore our environment in case a vforked child clob'd it. */ environ = save_our_env; init_thread_list (); /* Needed for wait_for_inferior stuff below. */ inferior_ptid = pid_to_ptid (pid); /* Now that we have a child process, make it our target, and initialize anything target-vector-specific that needs initializing. */ (*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. */ /* Allow target dependent code to play with the new process. This might be used to have target-specific code initialize a variable in the new process prior to executing the first instruction. */ TARGET_CREATE_INFERIOR_HOOK (pid); #ifdef SOLIB_CREATE_INFERIOR_HOOK SOLIB_CREATE_INFERIOR_HOOK (pid); #else solib_create_inferior_hook (); #endif } /* Accept NTRAPS traps from the inferior. */ void startup_inferior (int ntraps) { int pending_execs = ntraps; int terminal_initted = 0; /* 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. */ clear_proceed_status (); init_wait_for_inferior (); /* APPLE LOCAL start with shell */ if (start_with_shell_flag) pending_execs = START_INFERIOR_TRAPS_EXPECTED; else pending_execs = START_INFERIOR_TRAPS_EXPECTED_NOSHELL; inferior_ignoring_startup_exec_events = pending_execs; inferior_ignoring_leading_exec_events = target_reported_exec_events_per_exec_call () - 1; while (1) { /* Make wait_for_inferior be quiet. */ stop_soon = STOP_QUIETLY; wait_for_inferior (); if (stop_signal != TARGET_SIGNAL_TRAP) { /* Let shell child handle its own signals in its own way. FIXME: what if child has exited? Must exit loop somehow. */ if (PIDGET (inferior_ptid) == 0) break; resume (0, stop_signal); } else { /* 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) break; resume (0, TARGET_SIGNAL_0); /* Just make it go on. */ } } stop_soon = NO_STOP_QUIETLY; } /* APPLE LOCAL begin start with shell */ void _initialize_fork_child (void) { exec_pathname = savestring ("", 1); exec_argv0 = savestring ("", 1); add_setshow_string_cmd ("exec-pathname", no_class, &exec_pathname, _("\ Set the pathname to be used to start the target executable."), _("\ Show the pathname to be used to start the target executable."), NULL, NULL, NULL, &setlist, &showlist); add_setshow_string_cmd ("exec-argv0", no_class, &exec_argv0, _("\ Set the value of argv[0] to be passed to the target executable.\n\ This will be used only if 'start-with-shell' is set to 'off'."), _("\ x"), NULL, NULL, NULL, &setlist, &showlist); add_setshow_boolean_cmd ("start-with-shell", class_obscure, &start_with_shell_flag, _("\ Set if GDB should use shell to invoke inferior (performs argument expansion in shell)."), _("\ Show if GDB should use shell to invoke inferior (performs argument expansion in shell)."), NULL, NULL, NULL, &setlist, &showlist); } /* APPLE LOCAL end start with shell */