Add helper program for running services

We no longer need to keep entire scripts in init program (i.e. saving space)
and reduce the code and complexity of the init program.

The runsvc tool can later be extended to do more complex child setup, such
as configuring namespaces or seccomp without adding complexity or memory
footprint to init.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@tele2.at>

.gitignore

@@ -19,6 +19,7 @@ service
 reboot
 shutdown
 killall5
+runsvc
 
 services/sigkill
 services/sigterm

cmd/Makemodule.am

@@ -10,6 +10,12 @@ reboot_CFLAGS = $(AM_CFLAGS)
 reboot_LDFLAGS = $(AM_LDFLAGS)
 reboot_LDADD = libinit.a
 
+runsvc_SOURCES = cmd/runsvc/runsvc.c cmd/runsvc/env.c cmd/runsvc/runsvc.h
+runsvc_CPPFLAGS = $(AM_CPPFLAGS)
+runsvc_CFLAGS = $(AM_CFLAGS)
+runsvc_LDFLAGS = $(AM_LDFLAGS)
+runsvc_LDADD = libinit.a
+
 killall5_SOURCES = cmd/killall5.c
 killall5_CPPFLAGS = $(AM_CPPFLAGS)
 killall5_CFLAGS = $(AM_CFLAGS)
@@ -29,4 +35,4 @@ service_LDADD = libinit.a
 EXTRA_DIST += $(SRVHEADERS)
 
 sbin_PROGRAMS += service reboot shutdown
-helper_PROGRAMS += killall5
+helper_PROGRAMS += killall5 runsvc

cmd/runsvc/env.c

@@ -15,14 +15,7 @@
  * You should have received a copy of the GNU General Public License
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
-#include <unistd.h>
-#include <string.h>
-#include <stdlib.h>
-#include <stdio.h>
-#include <fcntl.h>
-
-#include "init.h"
-#include "util.h"
+#include "runsvc.h"
 
 struct entry {
 	struct entry *next;

cmd/runsvc/runsvc.c

@@ -15,21 +15,12 @@
  * You should have received a copy of the GNU General Public License
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
-#include <sys/wait.h>
-#include <unistd.h>
-#include <stdlib.h>
-#include <string.h>
-#include <stdio.h>
-#include <fcntl.h>
+#include "runsvc.h"
 
-#include "init.h"
-
-static int child_setup(const char *ctty)
+static int setup_tty(const char *ctty)
 {
 	int fd;
 
-	sigreset();
-
 	if (ctty != NULL) {
 		fd = open(ctty, O_RDWR);
 		if (fd < 0) {
@@ -52,6 +43,8 @@ static int child_setup(const char *ctty)
 	return 0;
 }
 
+/*****************************************************************************/
+
 static NORETURN void argv_exec(exec_t *e)
 {
 	char **argv = alloca(e->argc + 1), *ptr;
@@ -66,7 +59,7 @@ static NORETURN void argv_exec(exec_t *e)
 	exit(EXIT_FAILURE);
 }
 
-int runlst_wait(exec_t *list, const char *ctty)
+static int runlst_wait(exec_t *list)
 {
 	pid_t ret, pid;
 	int status;
@@ -74,11 +67,8 @@ int runlst_wait(exec_t *list, const char *ctty)
 	for (; list != NULL; list = list->next) {
 		pid = fork();
 
-		if (pid == 0) {
-			if (child_setup(ctty))
-				exit(EXIT_FAILURE);
+		if (pid == 0)
 			argv_exec(list);
-		}
 
 		if (pid == -1) {
 			perror("fork");
@@ -99,22 +89,50 @@ int runlst_wait(exec_t *list, const char *ctty)
 	return EXIT_SUCCESS;
 }
 
-pid_t runlst(exec_t *list, const char *ctty)
+/*****************************************************************************/
+
+int main(int argc, char **argv)
 {
-	pid_t pid = fork();
+	int dirfd, ret = EXIT_FAILURE;
+	service_t *svc = NULL;
 
-	if (pid == 0) {
-		if (child_setup(ctty))
-			exit(EXIT_FAILURE);
-
-		if (list->next != NULL)
-			exit(runlst_wait(list, NULL));
-
-		argv_exec(list);
+	if (argc != 3) {
+		fputs("usage: runsvc <directory> <filename>\n", stderr);
+		goto out;
 	}
 
-	if (pid == -1)
-		perror("fork");
+	if (getppid() != 1) {
+		fputs("must be run by init!\n", stderr);
+		goto out;
+	}
 
-	return pid;
+	dirfd = open(argv[1], O_RDONLY | O_DIRECTORY);
+	if (dirfd < 0) {
+		perror(argv[1]);
+		goto out;
+	}
+
+	svc = rdsvc(dirfd, argv[2], RDSVC_NO_FNAME | RDSVC_NO_DEPS);
+	close(dirfd);
+	if (svc == NULL)
+		goto out;
+
+	if (svc->exec == NULL) {
+		ret = EXIT_SUCCESS;
+		goto out;
+	}
+
+	if (initenv())
+		goto out;
+
+	if (setup_tty(svc->ctty))
+		goto out;
+
+	if (svc->exec->next == NULL)
+		argv_exec(svc->exec);
+
+	ret = runlst_wait(svc->exec);
+out:
+	delsvc(svc);
+	return ret;
 }

cmd/runsvc/runsvc.h

@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * Copyright (C) 2018 - David Oberhollenzer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#ifndef RUNSVC_H
+#define RUNSVC_H
+
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <fcntl.h>
+
+#include "service.h"
+#include "util.h"
+
+#define ENVFILE ETCPATH "/initd.env"
+
+int initenv(void);
+
+#endif /* RUNSVC_H */

initd/Makemodule.am

@@ -1,5 +1,5 @@
-init_SOURCES = initd/main.c initd/runlst.c initd/init.h initd/signal_linux.c
-init_SOURCES += initd/status.c initd/mksock.c initd/svclist.c initd/env.c
+init_SOURCES = initd/main.c initd/init.h initd/signal_linux.c initd/runsvc.c
+init_SOURCES += initd/status.c initd/mksock.c initd/svclist.c
 init_CPPFLAGS = $(AM_CPPFLAGS)
 init_CFLAGS = $(AM_CFLAGS)
 init_LDFLAGS = $(AM_LDFLAGS)

initd/init.h

@@ -27,7 +27,7 @@
 #include "telinit.h"
 #include "util.h"
 
-#define ENVFILE ETCPATH "/initd.env"
+#define RUNSVCBIN SCRIPTDIR "/runsvc"
 
 enum {
 	STATUS_OK = 0,
@@ -36,35 +36,20 @@ enum {
 	STATUS_STARTED,
 };
 
-/********** runlst.c **********/
+/********** runsvc.c **********/
 
 /*
-	Plow through an array of strings and execute each one, i.e. do
-	a fork() and exec().
+	Invoke the runsvc command to execute the comands of a service.
 
-	In the parent process, wait() until the child is done before
-	continuing through the list.
-
-	If ctty is not NULL, open it and redirect all I/O of the child
-	process to that file.
-
-	If everyhing works, the function returns EXIT_SUCCESS. If one child
-	does not exit with EXIT_SUCCESS, processing of the list is aborted
-	and the function returns the exit status of the failed process.
+	Returns the pid of the child process containing the runsvc instance.
 */
-int runlst_wait(exec_t *list, const char *ctty);
+pid_t runsvc(service_t *svc);
 
 /*
-	Does basically the same as runlst_wait, but asynchronously.
-
-	A child process is created that calls runlst_wait exits with the
-	result of runlst_wait. In the parent process, the function returns
-	immediately with the PID of the child process.
-
-	Alternatively, if num is 1, the child process directly exec()s the
-	given command.
+	Start a service using runsvc, but wait until the child process
+	terminats and return its exit status.
 */
-pid_t runlst(exec_t *list, const char *ctty);
+int runsvc_wait(service_t *svc);
 
 /********** status.c **********/
 
@@ -111,14 +96,6 @@ void svclist_add(service_t *svc);
 */
 service_t *svclist_remove(pid_t pid);
 
-/********** env.c **********/
-
-/*
-	Read /etc/initd.env (actually ENVFILE defined above)
-	and setup environment variables for init.
-*/
-int initenv(void);
-
 /********** signal_<platform>.c **********/
 
 /*

initd/main.c

@@ -48,7 +48,7 @@ static void handle_exited(service_t *svc)
 			}
 		}
 
-		svc->pid = runlst(svc->exec, svc->ctty);
+		svc->pid = runsvc(svc);
 		if (svc->pid == -1) {
 			print_status(svc->desc, STATUS_FAIL, false);
 			break;
@@ -104,16 +104,10 @@ static void start_runlevel(int level)
 		svc = cfg.targets[level];
 		cfg.targets[level] = svc->next;
 
-		if (svc->exec == NULL) {
-			print_status(svc->desc, STATUS_OK, false);
-			delsvc(svc);
-			continue;
-		}
-
 		if (svc->type == SVC_WAIT) {
 			print_status(svc->desc, STATUS_WAIT, false);
 
-			status = runlst_wait(svc->exec, svc->ctty);
+			status = runsvc_wait(svc);
 
 			print_status(svc->desc,
 				     status == EXIT_SUCCESS ?
@@ -121,7 +115,7 @@ static void start_runlevel(int level)
 				     true);
 			delsvc(svc);
 		} else {
-			svc->pid = runlst(svc->exec, svc->ctty);
+			svc->pid = runsvc(svc);
 			if (svc->pid == -1) {
 				print_status(svc->desc, STATUS_FAIL, false);
 				delsvc(svc);
@@ -193,7 +187,7 @@ int main(void)
 		return EXIT_FAILURE;
 	}
 
-	if (svcscan(SVCDIR, &cfg, 0)) {
+	if (svcscan(SVCDIR, &cfg, RDSVC_NO_EXEC | RDSVC_NO_CTTY)) {
 		fputs("Error reading service list from " SVCDIR "\n"
 			"Trying to continue anyway\n", stderr);
 	}

initd/runsvc.c

@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * Copyright (C) 2018 - David Oberhollenzer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#include "init.h"
+
+pid_t runsvc(service_t *svc)
+{
+	char *argv[4], *envp[1];
+	pid_t pid;
+
+	argv[0] = (char *)RUNSVCBIN;
+	argv[1] = (char *)SVCDIR;
+	argv[2] = svc->fname;
+	argv[3] = NULL;
+
+	envp[0] = NULL;
+
+	pid = fork();
+
+	if (pid == -1)
+		perror("fork");
+
+	if (pid == 0) {
+		sigreset();
+		execve(argv[0], argv, envp);
+		perror(argv[0]);
+		exit(EXIT_FAILURE);
+	}
+
+	return pid;
+}
+
+int runsvc_wait(service_t *svc)
+{
+	pid_t ret, pid = runsvc(svc);
+	int status;
+
+	if (pid == -1)
+		return EXIT_FAILURE;
+
+	do {
+		ret = waitpid(pid, &status, 0);
+	} while (ret != pid);
+
+	return WIFEXITED(status) ? WEXITSTATUS(status) : EXIT_FAILURE;
+}

services/sysinit

@@ -1,3 +1,3 @@
 description basic system initialization
-type once
+type wait
 target boot

services/vfs

@@ -1,3 +1,3 @@
 description VFS setup done
-type once
+type wait
 target boot