int libxl__openptys(libxl__openpty_state *op,
struct termios *termp,
struct winsize *winp) {
/*
* This is completely crazy. openpty calls grantpt which the spec
* says may fork, and may not be called with a SIGCHLD handler.
* Now our application may have a SIGCHLD handler so that's bad.
* We could perhaps block it but we'd need to block it on all
* threads. This is just Too Hard.
*
* So instead, we run openpty in a child process. That child
* process then of course has only our own thread and our own
* signal handlers. We pass the fds back.
*
* Since our only current caller actually wants two ptys, we
* support calling openpty multiple times for a single fork.
*/
STATE_AO_GC(op->ao);
int count = op->count;
int r, i, rc, sockets[2], ptyfds[count][2];
libxl__carefd *for_child = 0;
pid_t pid = -1;
for (i=0; i<count; i++) {
ptyfds[i][0] = ptyfds[i][1] = -1;
libxl__openpty_result *res = &op->results[i];
assert(!res->master);
assert(!res->slave);
}
sockets[0] = sockets[1] = -1; /* 0 is for us, 1 for our child */
libxl__carefd_begin();
r = socketpair(AF_UNIX, SOCK_STREAM, 0, sockets);
if (r) { sockets[0] = sockets[1] = -1; }
for_child = libxl__carefd_opened(CTX, sockets[1]);
if (r) { LOGE(ERROR,"socketpair failed"); rc = ERROR_FAIL; goto out; }
pid = libxl__ev_child_fork(gc, &op->child, openpty_exited);
if (pid == -1) {
rc = ERROR_FAIL;
goto out;
}
if (!pid) {
/* child */
close(sockets[0]);
signal(SIGCHLD, SIG_DFL);
for (i=0; i<count; i++) {
r = openpty(&ptyfds[i][0], &ptyfds[i][1], NULL, termp, winp);
if (r) { LOGE(ERROR,"openpty failed"); _exit(-1); }
}
rc = libxl__sendmsg_fds(gc, sockets[1], "",1,
2*count, &ptyfds[0][0], "ptys");
if (rc) { LOGE(ERROR,"sendmsg to parent failed"); _exit(-1); }
_exit(0);
}
libxl__carefd_close(for_child);
for_child = 0;
/* this should be fast so do it synchronously */
libxl__carefd_begin();
char buf[1];
rc = libxl__recvmsg_fds(gc, sockets[0], buf,1,
2*count, &ptyfds[0][0], "ptys");
if (!rc) {
for (i=0; i<count; i++) {
libxl__openpty_result *res = &op->results[i];
res->master = libxl__carefd_record(CTX, ptyfds[i][0]);
res->slave = libxl__carefd_record(CTX, ptyfds[i][1]);
}
}
/* now the pty fds are in the carefds, if they were ever open */
libxl__carefd_unlock();
if (rc)
goto out;
rc = 0;
out:
if (sockets[0] >= 0) close(sockets[0]);
libxl__carefd_close(for_child);
if (libxl__ev_child_inuse(&op->child)) {
op->rc = rc;
/* we will get a callback when the child dies */
return 0;
}
assert(rc);
openpty_cleanup(op);
return rc;
}
static void run_helper(libxl__egc *egc, libxl__save_helper_state *shs,
const char *mode_arg, int stream_fd,
const int *preserve_fds, int num_preserve_fds,
const unsigned long *argnums, int num_argnums)
{
STATE_AO_GC(shs->ao);
const char *args[4 + num_argnums];
const char **arg = args;
int i, rc;
/* Resources we must free */
libxl__carefd *childs_pipes[2] = { 0,0 };
/* Convenience aliases */
const uint32_t domid = shs->domid;
shs->rc = 0;
shs->completed = 0;
shs->pipes[0] = shs->pipes[1] = 0;
libxl__ev_fd_init(&shs->readable);
libxl__ev_child_init(&shs->child);
shs->stdin_what = GCSPRINTF("domain %"PRIu32" save/restore helper"
" stdin pipe", domid);
shs->stdout_what = GCSPRINTF("domain %"PRIu32" save/restore helper"
" stdout pipe", domid);
*arg++ = getenv("LIBXL_SAVE_HELPER") ?: PRIVATE_BINDIR "/" "libxl-save-helper";
*arg++ = mode_arg;
const char **stream_fd_arg = arg++;
for (i=0; i<num_argnums; i++)
*arg++ = GCSPRINTF("%lu", argnums[i]);
*arg++ = 0;
assert(arg == args + ARRAY_SIZE(args));
libxl__carefd_begin();
int childfd;
for (childfd=0; childfd<2; childfd++) {
/* Setting up the pipe for the child's fd childfd */
int fds[2];
if (libxl_pipe(CTX,fds)) {
rc = ERROR_FAIL;
libxl__carefd_unlock();
goto out;
}
int childs_end = childfd==0 ? 0 /*read*/ : 1 /*write*/;
int our_end = childfd==0 ? 1 /*write*/ : 0 /*read*/;
childs_pipes[childfd] = libxl__carefd_record(CTX, fds[childs_end]);
shs->pipes[childfd] = libxl__carefd_record(CTX, fds[our_end]);
}
libxl__carefd_unlock();
pid_t pid = libxl__ev_child_fork(gc, &shs->child, helper_exited);
if (!pid) {
if (stream_fd <= 2) {
stream_fd = dup(stream_fd);
if (stream_fd < 0) {
LOGE(ERROR,"dup migration stream fd");
exit(-1);
}
}
libxl_fd_set_cloexec(CTX, stream_fd, 0);
*stream_fd_arg = GCSPRINTF("%d", stream_fd);
for (i=0; i<num_preserve_fds; i++)
if (preserve_fds[i] >= 0) {
assert(preserve_fds[i] > 2);
libxl_fd_set_cloexec(CTX, preserve_fds[i], 0);
}
libxl__exec(gc,
libxl__carefd_fd(childs_pipes[0]),
libxl__carefd_fd(childs_pipes[1]),
-1,
args[0], (char**)args, 0);
}
libxl__carefd_close(childs_pipes[0]);
libxl__carefd_close(childs_pipes[1]);
rc = libxl__ev_fd_register(gc, &shs->readable, helper_stdout_readable,
libxl__carefd_fd(shs->pipes[1]), POLLIN|POLLPRI);
if (rc) goto out;
return;
out:
libxl__carefd_close(childs_pipes[0]);
libxl__carefd_close(childs_pipes[1]);
helper_failed(egc, shs, rc);;
}