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Diffstat (limited to 'gdb/fork-child.c')
| -rw-r--r-- | gdb/fork-child.c | 616 |
1 files changed, 616 insertions, 0 deletions
diff --git a/gdb/fork-child.c b/gdb/fork-child.c new file mode 100644 index 00000000000..f3504bc6409 --- /dev/null +++ b/gdb/fork-child.c @@ -0,0 +1,616 @@ +/* Fork a Unix child process, and set up to debug it, for GDB. + Copyright 1990, 1991, 1992, 1993, 1994, 1996 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 "wait.h" +#include "gdbcore.h" +#include "terminal.h" +#include "gdbthread.h" + +#include <signal.h> +#ifdef HAVE_UNISTD_H +#include <unistd.h> +#endif + +#define DEBUGGING 0 + +/* 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; + +/* This function breaks up an argument string into an argument + * vector suitable for passing to execvp(). + * 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 ( + scratch, + argv) + char *scratch; + char **argv; +{ + char *cp = scratch; + +#if DEBUGGING + printf ("breakup_args: input = %s\n", scratch); +#endif + 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 */ + cp = strchr (cp, ' '); + if (cp == NULL) + cp = strchr (cp, '\t'); + if (cp == NULL) + cp = strchr (cp, '\n'); + + /* No separators => end of string => break */ + if (cp == NULL) + break; + + /* Replace the separator with a terminator */ + *cp++ = '\0'; + } + + /* execv requires a null-terminated arg vector */ + *argv = NULL; + +} + + +/* Start an inferior Unix child process and sets inferior_pid 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. Errors reported with error(). */ + +void +fork_inferior (exec_file, allargs, env, traceme_fun, init_trace_fun, + pre_trace_fun, shell_file) + char *exec_file; + char *allargs; + char **env; + void (*traceme_fun) PARAMS ((void)); + void (*init_trace_fun) PARAMS ((int)); + void (*pre_trace_fun) PARAMS ((void)); + char *shell_file; +{ + 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 = 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; + char **save_our_env; + int shell = 0; + char **argv; + char *tryname; + + /* If no exec file handed to us, get it from the exec-file command -- with + a good, common error message if none is specified. */ + if (exec_file == 0) + exec_file = get_exec_file (1); + + /* STARTUP_WITH_SHELL is defined in inferior.h. + * If 0, we'll just do a fork/exec, no shell, so don't + * bother figuring out what shell. + */ + if (STARTUP_WITH_SHELL) + { + /* 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 DEBUGGING + printf ("shell is %s\n", shell_file); +#endif + + /* 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) + { + /* We're going to call execvp. Create argv */ + /* Largest case: every other character is a separate arg */ +#if DEBUGGING + printf ("allocating argv, length = %d\n", + ( + (strlen (allargs) + 1) / (unsigned) 2 + + 2 + ) * sizeof (*argv) + ); +#endif + argv = (char **) xmalloc (((strlen (allargs) + 1) / (unsigned) 2 + 2) * sizeof (*argv)); + argv[0] = exec_file; + breakup_args (allargs, &argv[1]); + + } + else + { + + /* We're going to call a shell */ + + /* Now add exec_file, quoting as necessary. */ + + char *p; + int need_to_quote; + + 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 '\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 + strncat (shell_command, p, 1); + } + strcat (shell_command, "'"); + } + else + strcat (shell_command, exec_file); + + strcat (shell_command, " "); + strcat (shell_command, allargs); + + } + + /* exec is said to 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) (); + +#if defined(USG) && !defined(HAVE_VFORK) + pid = fork (); +#else + if (debug_fork) + pid = fork (); + else + pid = vfork (); +#endif + + 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; + + /* 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) + { +#if 0 + + /* HP change is problematic. The -f option has different meanings + for different shells. It is particularly inappropriate for + bourne shells. */ + execlp (shell_file, shell_file, "-f", "-c", shell_command, (char *) 0); +#else + execlp (shell_file, shell_file, "-c", shell_command, (char *) 0); +#endif + + + /* 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 DEBUGGING + printf ("about to exec target, exec_file = %s\n", exec_file); + i = 0; + while (argv[i] != NULL) + { + printf ("strlen(argv[%d]) is %d\n", i, strlen (argv[i])); + printf ("argv[%d] is %s\n", i, argv[i]); + i++; + } +#endif + 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"); + /* This extra info seems to be useless + fprintf_unfiltered (gdb_stderr, "Got error %s.\n", errstring); + */ + gdb_flush (gdb_stderr); + _exit (0177); + } + } + + /* Restore our environment in case a vforked child clob'd it. */ + environ = save_our_env; + + init_thread_list (); + + inferior_pid = pid; /* Needed for wait_for_inferior stuff below */ + + /* 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 dependant 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); +#endif +} + +/* An inferior Unix process CHILD_PID has been created by a call to + fork() (or variants like vfork). It is presently stopped, and waiting + to be resumed. clone_and_follow_inferior will fork the debugger, + and that clone will "follow" (attach to) CHILD_PID. The original copy + of the debugger will not touch CHILD_PID again. + + Also, the original debugger will set FOLLOWED_CHILD FALSE, while the + clone will set it TRUE. + */ +void +clone_and_follow_inferior (child_pid, followed_child) + int child_pid; + int *followed_child; +{ + extern int auto_solib_add; + + int debugger_pid; + int status; + char pid_spelling[100]; /* Arbitrary but sufficient length. */ + + /* This semaphore is used to coordinate the two debuggers' handoff + of CHILD_PID. The original debugger will detach from CHILD_PID, + and then the clone debugger will attach to it. (It must be done + this way because on some targets, only one process at a time can + trace another. Thus, the original debugger must relinquish its + tracing rights before the clone can pick them up.) + */ +#define SEM_TALK (1) +#define SEM_LISTEN (0) + int handoff_semaphore[2]; /* Original "talks" to [1], clone "listens" to [0] */ + int talk_value = 99; + int listen_value; + + /* Set debug_fork then attach to the child while it sleeps, to debug. */ + static int debug_fork = 0; + + /* 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); + + /* Open the semaphore pipes. + */ + status = pipe (handoff_semaphore); + if (status < 0) + error ("error getting pipe for handoff semaphore"); + + /* Clone the debugger. */ +#if defined(USG) && !defined(HAVE_VFORK) + debugger_pid = fork (); +#else + if (debug_fork) + debugger_pid = fork (); + else + debugger_pid = vfork (); +#endif + + if (debugger_pid < 0) + perror_with_name ("fork"); + + /* Are we the original debugger? If so, we must relinquish all claims + to CHILD_PID. */ + if (debugger_pid != 0) + { + char signal_spelling[100];/* Arbitrary but sufficient length */ + + /* Detach from CHILD_PID. Deliver a "stop" signal when we do, though, + so that it remains stopped until the clone debugger can attach + to it. + */ + detach_breakpoints (child_pid); + + sprintf (signal_spelling, "%d", target_signal_to_host (TARGET_SIGNAL_STOP)); + target_require_detach (child_pid, signal_spelling, 1); + + /* Notify the clone debugger that it should attach to CHILD_PID. */ + write (handoff_semaphore[SEM_TALK], &talk_value, sizeof (talk_value)); + + *followed_child = 0; + } + + /* We're the child. */ + else + { + if (debug_fork) + sleep (debug_fork); + + /* The child (i.e., the cloned debugger) must now attach to + CHILD_PID. inferior_pid is presently set to the parent process + of the fork, while CHILD_PID should be the child process of the + fork. + + Wait until the original debugger relinquishes control of CHILD_PID, + though. + */ + read (handoff_semaphore[SEM_LISTEN], &listen_value, sizeof (listen_value)); + + /* Note that we DON'T want to actually detach from inferior_pid, + because that would allow it to run free. The original + debugger wants to retain control of the process. So, we + just reset inferior_pid to CHILD_PID, and then ensure that all + breakpoints are really set in CHILD_PID. + */ + target_mourn_inferior (); + + /* Ask the tty subsystem to switch to the one we specified earlier + (or to share the current terminal, if none was specified). */ + + new_tty (); + + dont_repeat (); + sprintf (pid_spelling, "%d", child_pid); + target_require_attach (pid_spelling, 1); + + /* Perform any necessary cleanup, after attachment. (This form + of attaching can behave differently on some targets than the + standard method, where a process formerly not under debugger + control was suddenly attached to..) + */ + target_post_follow_inferior_by_clone (); + + *followed_child = 1; + } + + /* Discard the handoff sempahore. */ + (void) close (handoff_semaphore[SEM_LISTEN]); + (void) close (handoff_semaphore[SEM_TALK]); +} + +/* Accept NTRAPS traps from the inferior. */ + +void +startup_inferior (ntraps) + int ntraps; +{ + int pending_execs = ntraps; + int terminal_initted; + + /* 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 (); + + terminal_initted = 0; + + if (STARTUP_WITH_SHELL) + inferior_ignoring_startup_exec_events = ntraps; + else + inferior_ignoring_startup_exec_events = 0; + inferior_ignoring_leading_exec_events = + target_reported_exec_events_per_exec_call () - 1; + +#ifdef STARTUP_INFERIOR + STARTUP_INFERIOR (pending_execs); +#else + while (1) + { + stop_soon_quietly = 1; /* Make wait_for_inferior be quiet */ + 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 exit()ed? Must exit loop somehow */ + 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; + } + + pending_execs = pending_execs - 1; + if (0 == pending_execs) + break; + + resume (0, TARGET_SIGNAL_0); /* Just make it go on */ + } + } +#endif /* STARTUP_INFERIOR */ + stop_soon_quietly = 0; +} |