int grab_pid(pid_t pid, struct ptrace_child *child, child_addr_t *scratch) {
int err;
if (ptrace_attach_child(child, pid)) {
err = child->error;
goto out;
}
if (ptrace_advance_to_state(child, ptrace_at_syscall)) {
err = child->error;
goto out;
}
if (ptrace_save_regs(child)) {
err = child->error;
goto out;
}
if ((err = mmap_scratch(child, scratch)))
goto out_restore_regs;
return 0;
out_restore_regs:
ptrace_restore_regs(child);
out:
ptrace_detach_child(child);
return err;
}
int attach_child(pid_t pid, const char *pty, int force_stdio) {
struct ptrace_child child;
unsigned long scratch_page = -1;
int *child_tty_fds = NULL, n_fds, child_fd, statfd;
int i;
int err = 0;
long page_size = sysconf(_SC_PAGE_SIZE);
char stat_path[PATH_MAX];
long mmap_syscall;
if ((err = copy_tty_state(pid, pty))) {
if (err == ENOTTY && !force_stdio) {
error("Target is not connected to a terminal.\n"
" Use -s to force attaching anyways.");
return err;
}
}
snprintf(stat_path, sizeof stat_path, "/proc/%d/stat", pid);
statfd = open(stat_path, O_RDONLY);
if (statfd < 0) {
error("Unable to open %s: %s", stat_path, strerror(errno));
return -statfd;
}
kill(pid, SIGTSTP);
wait_for_stop(pid, statfd);
if (ptrace_attach_child(&child, pid)) {
err = child.error;
goto out_cont;
}
if (ptrace_advance_to_state(&child, ptrace_at_syscall)) {
err = child.error;
goto out_detach;
}
if (ptrace_save_regs(&child)) {
err = child.error;
goto out_detach;
}
mmap_syscall = ptrace_syscall_numbers(&child)->nr_mmap2;
if (mmap_syscall == -1)
mmap_syscall = ptrace_syscall_numbers(&child)->nr_mmap;
scratch_page = ptrace_remote_syscall(&child, mmap_syscall, 0,
page_size, PROT_READ|PROT_WRITE,
MAP_ANONYMOUS|MAP_PRIVATE, 0, 0);
if (scratch_page > (unsigned long)-1000) {
err = -(signed long)scratch_page;
goto out_unmap;
}
debug("Allocated scratch page: %lx", scratch_page);
if (force_stdio) {
child_tty_fds = malloc(3 * sizeof(int));
if (!child_tty_fds) {
err = ENOMEM;
goto out_unmap;
}
n_fds = 3;
child_tty_fds[0] = 0;
child_tty_fds[1] = 1;
child_tty_fds[2] = 2;
} else {
child_tty_fds = get_child_tty_fds(&child, statfd, &n_fds);
if (!child_tty_fds) {
err = child.error;
goto out_unmap;
}
}
if (ptrace_memcpy_to_child(&child, scratch_page, pty, strlen(pty)+1)) {
err = child.error;
error("Unable to memcpy the pty path to child.");
goto out_free_fds;
}
child_fd = do_syscall(&child, open,
scratch_page, O_RDWR|O_NOCTTY,
0, 0, 0, 0);
if (child_fd < 0) {
err = child_fd;
error("Unable to open the tty in the child.");
goto out_free_fds;
}
debug("Opened the new tty in the child: %d", child_fd);
err = ignore_hup(&child, scratch_page);
if (err < 0)
goto out_close;
err = do_syscall(&child, getsid, 0, 0, 0, 0, 0, 0);
if (err != child.pid) {
debug("Target is not a session leader, attempting to setsid.");
err = do_setsid(&child);
} else {
do_syscall(&child, ioctl, child_tty_fds[0], TIOCNOTTY, 0, 0, 0, 0);
}
if (err < 0)
goto out_close;
err = do_syscall(&child, ioctl, child_fd, TIOCSCTTY, 0, 0, 0, 0);
if (err < 0) {
error("Unable to set controlling terminal.");
goto out_close;
}
debug("Set the controlling tty");
for (i = 0; i < n_fds; i++)
do_syscall(&child, dup2, child_fd, child_tty_fds[i], 0, 0, 0, 0);
err = 0;
out_close:
do_syscall(&child, close, child_fd, 0, 0, 0, 0, 0);
out_free_fds:
free(child_tty_fds);
out_unmap:
do_unmap(&child, scratch_page, page_size);
ptrace_restore_regs(&child);
out_detach:
ptrace_detach_child(&child);
if (err == 0) {
kill(child.pid, SIGSTOP);
wait_for_stop(child.pid, statfd);
}
kill(child.pid, SIGWINCH);
out_cont:
kill(child.pid, SIGCONT);
close(statfd);
return err < 0 ? -err : err;
}