/* 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 (int child_pid, int *followed_child)
{
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. Note that the apparent call to vfork()
below *might* actually be a call to fork() due to the fact that
autoconf will ``#define vfork fork'' on certain platforms. */
if (debug_fork)
debugger_pid = fork ();
else
debugger_pid = vfork ();
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_ptid 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_ptid,
because that would allow it to run free. The original
debugger wants to retain control of the process. So, we
just reset inferior_ptid 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]);
}
int
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 = 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;
/* 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;
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;
}
/* 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';
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 **) xmalloc (argc * sizeof (*argv));
argv[0] = exec_file;
breakup_args (allargs, &argv[1]);
}
else
{
/* We're going to call a shell. */
char *p;
int need_to_quote;
const int escape_bang = escape_bang_in_quoted_argument (shell_file);
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;
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) 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 ();
else
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 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>". */
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;
execvp (exec_file, argv);
/* If we get here, it's an error. */
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");
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;
}
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 = 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;
/* 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, we'll just do a fork/exec, no shell, so don't
* bother figuring out what shell.
*/
shell_file = shell_file_arg;
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;
}
/* 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 */
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 ' ':
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 == '!')
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) ();
/* Create the child process. Note that the apparent call to vfork()
below *might* actually be a call to fork() due to the fact that
autoconf will ``#define vfork fork'' on certain platforms. */
if (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;
/* 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;
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_ptid = pid_to_ptid (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 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);
#endif
}