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/* SPDX-License-Identifier: LGPL-2.1+ */
/***
This file is part of systemd.
Copyright 2016 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <sys/reboot.h>
#include <sys/wait.h>
#include <sys/prctl.h>
#include <unistd.h>
#include "fd-util.h"
#include "log.h"
#include "missing.h"
#include "nspawn-stub-pid1.h"
#include "process-util.h"
#include "signal-util.h"
#include "time-util.h"
#include "def.h"
static int reset_environ(const char *new_environment, size_t length) {
unsigned long start, end;
start = (unsigned long) new_environment;
end = start + length;
if (prctl(PR_SET_MM, PR_SET_MM_ENV_START, start, 0, 0) < 0)
return -errno;
if (prctl(PR_SET_MM, PR_SET_MM_ENV_END, end, 0, 0) < 0)
return -errno;
return 0;
}
int stub_pid1(sd_id128_t uuid) {
enum {
STATE_RUNNING,
STATE_REBOOT,
STATE_POWEROFF,
} state = STATE_RUNNING;
sigset_t fullmask, oldmask, waitmask;
usec_t quit_usec = USEC_INFINITY;
pid_t pid;
int r;
/* The new environment we set up, on the stack. */
char new_environment[] =
"container=systemd-nspawn\0"
"container_uuid=XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX";
/* Implements a stub PID 1, that reaps all processes and processes a couple of standard signals. This is useful
* for allowing arbitrary processes run in a container, and still have all zombies reaped. */
assert_se(sigfillset(&fullmask) >= 0);
assert_se(sigprocmask(SIG_BLOCK, &fullmask, &oldmask) >= 0);
pid = fork();
if (pid < 0)
return log_error_errno(errno, "Failed to fork child pid: %m");
if (pid == 0) {
/* Return in the child */
assert_se(sigprocmask(SIG_SETMASK, &oldmask, NULL) >= 0);
setsid();
return 0;
}
reset_all_signal_handlers();
log_close();
close_all_fds(NULL, 0);
log_open();
/* Flush out /proc/self/environ, so that we don't leak the environment from the host into the container. Also,
* set $container= and $container_uuid= so that clients in the container that query it from /proc/1/environ
* find them set. */
sd_id128_to_string(uuid, new_environment + sizeof(new_environment) - SD_ID128_STRING_MAX);
reset_environ(new_environment, sizeof(new_environment));
(void) rename_process("(sd-stubinit)");
assert_se(sigemptyset(&waitmask) >= 0);
assert_se(sigset_add_many(&waitmask,
SIGCHLD, /* posix: process died */
SIGINT, /* sysv: ctrl-alt-del */
SIGRTMIN+3, /* systemd: halt */
SIGRTMIN+4, /* systemd: poweroff */
SIGRTMIN+5, /* systemd: reboot */
SIGRTMIN+6, /* systemd: kexec */
SIGRTMIN+13, /* systemd: halt */
SIGRTMIN+14, /* systemd: poweroff */
SIGRTMIN+15, /* systemd: reboot */
SIGRTMIN+16, /* systemd: kexec */
-1) >= 0);
/* Note that we ignore SIGTERM (sysv's reexec), SIGHUP (reload), and all other signals here, since we don't
* support reexec/reloading in this stub process. */
for (;;) {
siginfo_t si;
usec_t current_usec;
si.si_pid = 0;
r = waitid(P_ALL, 0, &si, WEXITED|WNOHANG);
if (r < 0) {
r = log_error_errno(errno, "Failed to reap children: %m");
goto finish;
}
current_usec = now(CLOCK_MONOTONIC);
if (si.si_pid == pid || current_usec >= quit_usec) {
/* The child we started ourselves died or we reached a timeout. */
if (state == STATE_REBOOT) { /* dispatch a queued reboot */
(void) reboot(RB_AUTOBOOT);
r = log_error_errno(errno, "Failed to reboot: %m");
goto finish;
} else if (state == STATE_POWEROFF)
(void) reboot(RB_POWER_OFF); /* if this fails, fall back to normal exit. */
if (si.si_pid == pid && si.si_code == CLD_EXITED)
r = si.si_status; /* pass on exit code */
else
r = 255; /* signal, coredump, timeout, … */
goto finish;
}
if (si.si_pid != 0)
/* We reaped something. Retry until there's nothing more to reap. */
continue;
if (quit_usec == USEC_INFINITY)
r = sigwaitinfo(&waitmask, &si);
else {
struct timespec ts;
r = sigtimedwait(&waitmask, &si, timespec_store(&ts, quit_usec - current_usec));
}
if (r < 0) {
if (errno == EINTR) /* strace -p attach can result in EINTR, let's handle this nicely. */
continue;
if (errno == EAGAIN) /* timeout reached */
continue;
r = log_error_errno(errno, "Failed to wait for signal: %m");
goto finish;
}
if (si.si_signo == SIGCHLD)
continue; /* Let's reap this */
if (state != STATE_RUNNING)
continue;
/* Would love to use a switch() statement here, but SIGRTMIN is actually a function call, not a
* constant… */
if (si.si_signo == SIGRTMIN+3 ||
si.si_signo == SIGRTMIN+4 ||
si.si_signo == SIGRTMIN+13 ||
si.si_signo == SIGRTMIN+14)
state = STATE_POWEROFF;
else if (si.si_signo == SIGINT ||
si.si_signo == SIGRTMIN+5 ||
si.si_signo == SIGRTMIN+6 ||
si.si_signo == SIGRTMIN+15 ||
si.si_signo == SIGRTMIN+16)
state = STATE_REBOOT;
else
assert_not_reached("Got unexpected signal");
r = kill_and_sigcont(pid, SIGTERM);
/* Let's send a SIGHUP after the SIGTERM, as shells tend to ignore SIGTERM but do react to SIGHUP. We
* do it strictly in this order, so that the SIGTERM is dispatched first, and SIGHUP second for those
* processes which handle both. That's because services tend to bind configuration reload or something
* else to SIGHUP. */
if (r != -ESRCH)
(void) kill(pid, SIGHUP);
quit_usec = now(CLOCK_MONOTONIC) + DEFAULT_TIMEOUT_USEC;
}
finish:
_exit(r < 0 ? EXIT_FAILURE : r);
}
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