sulogin-shell: switch from shell implementation to a C implementation (#6698)

src/sulogin-shell/meson.build

@@ -1,7 +1,8 @@
-gen = configure_file(
-        input : 'systemd-sulogin-shell.in',
-        output : 'systemd-sulogin-shell',
-        configuration : substs)
-
-install_data(gen,
-             install_dir : rootlibexecdir)
+executable('systemd-sulogin-shell',
+           ['sulogin-shell.c'],
+           include_directories : includes,
+           link_with : [libshared],
+           dependencies : [],
+           install_rpath : rootlibexecdir,
+           install : true,
+           install_dir : rootlibexecdir)

src/sulogin-shell/sulogin-shell.c

@@ -0,0 +1,105 @@
+/***
+  This file is part of systemd.
+
+  Copyright 2017 Felipe Sateler
+
+  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 <errno.h>
+#include <sys/prctl.h>
+
+#include "bus-util.h"
+#include "bus-error.h"
+#include "log.h"
+#include "process-util.h"
+#include "sd-bus.h"
+#include "signal-util.h"
+
+static int start_default_target(void) {
+        _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
+        _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
+        int r;
+
+        r = bus_connect_system_systemd(&bus);
+        if (r < 0) {
+                log_error_errno(r, "Failed to get D-Bus connection: %m");
+                return false;
+        }
+
+        log_info("Starting default target");
+
+        /* Start these units only if we can replace base.target with it */
+        r = sd_bus_call_method(bus,
+                               "org.freedesktop.systemd1",
+                               "/org/freedesktop/systemd1",
+                               "org.freedesktop.systemd1.Manager",
+                               "StartUnit",
+                               &error,
+                               NULL,
+                               "ss", "default.target", "isolate");
+
+        if (r < 0)
+                log_error("Failed to start default target: %s", bus_error_message(&error, r));
+
+        return r;
+}
+
+static void fork_wait(const char* const cmdline[]) {
+        pid_t pid;
+
+        pid = fork();
+        if (pid < 0) {
+                log_error_errno(errno, "fork(): %m");
+                return;
+        }
+        if (pid == 0) {
+
+                /* Child */
+
+                (void) reset_all_signal_handlers();
+                (void) reset_signal_mask();
+                assert_se(prctl(PR_SET_PDEATHSIG, SIGTERM) == 0);
+
+                execv(cmdline[0], (char**) cmdline);
+                log_error_errno(errno, "Failed to execute %s: %m", cmdline[0]);
+                _exit(EXIT_FAILURE); /* Operational error */
+        }
+
+        wait_for_terminate_and_warn(cmdline[0], pid, false);
+}
+
+static void print_mode(const char* mode) {
+        printf("You are in %s mode. After logging in, type \"journalctl -xb\" to view\n"
+                "system logs, \"systemctl reboot\" to reboot, \"systemctl default\" or ^D to boot\n"
+                "into default mode.\n", mode);
+        fflush(stdout);
+}
+
+int main(int argc, char *argv[]) {
+        static const char* const sulogin_cmdline[] = {SULOGIN, NULL};
+        int r;
+
+        log_set_target(LOG_TARGET_AUTO);
+        log_parse_environment();
+        log_open();
+
+        print_mode(argc > 1 ? argv[1] : "");
+
+        fork_wait(sulogin_cmdline);
+
+        r = start_default_target();
+
+        return r >= 0 ? EXIT_SUCCESS : EXIT_FAILURE;
+}

src/sulogin-shell/systemd-sulogin-shell.in

@@ -1,12 +0,0 @@
-#!/bin/sh
-
-if [ -x /bin/plymouth ]; then
-    /bin/plymouth --wait quit
-fi
-
-echo "You are in $1 mode. After logging in, type \"journalctl -xb\" to view"
-echo "system logs, \"systemctl reboot\" to reboot, \"systemctl default\" or ^D to boot"
-echo "into default mode."
-
-@SULOGIN@
-@SYSTEMCTL@ --no-block default

units/emergency.service.in

@@ -17,6 +17,7 @@ Before=shutdown.target
 [Service]
 Environment=HOME=/root
 WorkingDirectory=-/root
+ExecStartPre=-/bin/plymouth --wait quit
 ExecStart=-@rootlibexecdir@/systemd-sulogin-shell emergency
 Type=idle
 StandardInput=tty-force

units/rescue.service.in

@@ -16,6 +16,7 @@ Before=shutdown.target
 [Service]
 Environment=HOME=/root
 WorkingDirectory=-/root
+ExecStartPre=-/bin/plymouth --wait quit
 ExecStart=-@rootlibexecdir@/systemd-sulogin-shell rescue
 Type=idle
 StandardInput=tty-force