--- /dev/null
+/*
+ * Init-NG
+ *
+ * A minimal, drop-in replacement for SysV init.
+ * This leverages OpenRC to do most of the heavy lifting, and does the minimum
+ * amount that it should--unlike other so-called inits, that have world +
+ * kitchen sink thrown in, seemingly to enlarge the attack surface. ;-)
+ *
+ * by James Hammons
+ * (C) 2017 Underground Software
+ */
+
+#include <unistd.h>
+#include <errno.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/reboot.h>
+#include <sys/syscall.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/un.h>
+#include <sys/wait.h>
+
+static const char fifoPath[] = "/dev/initctl";
+static int shuttingDown = 0;
+static int verbose = 0; /* N.B.: There is no mechanism to set this ATM */
+static struct sigaction action;
+static int freeProcessSlot = 0;
+static pid_t processPID[1024];
+static char * processCmd[1024];
+static char * processName[1024];
+static char * args[256]; /* 256 arguments ought to be enough for anybody ;-) */
+
+
+/*
+ * Find a process in the monitored process list (MPL) by PID. Returns the index
+ * of the entry in the MPL.
+ */
+static int find_monitored_pid(pid_t pid)
+{
+ int i;
+
+ for(i=0; i<freeProcessSlot; i++)
+ {
+ if (processPID[i] == pid)
+ return i;
+ }
+
+ return -1;
+}
+
+
+/*
+ * Remove the given process from the MPL by index
+ */
+static void remove_entry(int entry)
+{
+ free(processCmd[entry]);
+ free(processName[entry]);
+ processPID[entry] = -1;
+
+ if (entry == (freeProcessSlot - 1))
+ freeProcessSlot--;
+}
+
+
+/*
+ * Add a process to the MPL
+ */
+static void add_entry(pid_t pid, const char * name, const char * command)
+{
+ int i;
+
+ for(i=0; i<freeProcessSlot; i++)
+ {
+ if (processPID[i] == -1)
+ break;
+ }
+
+ processPID[i] = pid;
+ processCmd[i] = strdup(command);
+ processName[i] = strdup(name);
+
+ if (i == freeProcessSlot)
+ freeProcessSlot++;
+}
+
+
+/*
+ * Take a given space delimited string and turn it into an array of strings
+ * suitable for execv().
+ */
+static void make_argument_list(const char * s)
+{
+ char buf[4096];
+ char * tokSave;
+ int i;
+ char * token;
+
+ strncpy(buf, s, 4095);
+ buf[4095] = 0;
+ i = 0;
+ token = strtok_r(buf, " ", &tokSave);
+
+ while (token != NULL)
+ {
+ args[i++] = token;
+ token = strtok_r(NULL, " ", &tokSave);
+ }
+
+ /* Argument list *must* end with a NULL entry: */
+ args[i] = NULL;
+}
+
+
+/*
+ * Launch a command from PID 1
+ *
+ * name: The human readable name for the process to launch
+ * command: The command to launch + any parameters it needs
+ * monitor: Tells Launch whether or not this process should be monitored
+ * and respawned if it goes away (0 = no, 1 = yes)
+ */
+static pid_t launch(const char * name, const char * command, int monitor)
+{
+ pid_t pid;
+
+ if (verbose)
+ printf("Starting %s (%smonitored)...\n", name, (monitor ? "" : "un"));
+
+ make_argument_list(command);
+ pid = fork();
+
+ if (pid == 0)
+ {
+ /* Child process gets here (if fork was successful)... */
+ setsid();
+ execv(args[0], args);
+
+ /* We only get here if an error happened with execv()... Need to figure
+ * out how to handle this gracefully...
+ */
+ printf("execv() failed!\n");
+ return 0;
+ }
+ else if (pid < 0)
+ {
+ printf("Fork failed; can't start %s!\n", name);
+ return pid;
+ }
+
+ /* Parent process gets here... So add to monitor list if requested */
+ if (monitor)
+ add_entry(pid, name, command);
+
+ return pid;
+}
+
+
+/*
+ * Here we do some process monitoring
+ * At some point, we'll read inittab instead of recording just our own internal
+ * processes...
+ */
+static void handle_sigchld(int signum)
+{
+ pid_t pid;
+ int entry;
+
+ while (1)
+ {
+ /* Get PID of exiting child process(es), if any */
+ pid = waitpid(-1, NULL, WNOHANG);
+
+ /* Check for exit conditions... */
+ if (pid == 0)
+ break;
+ else if (pid == -1)
+ {
+ if (errno == ECHILD)
+ break;
+
+ perror("waitpid");
+ continue;
+ }
+
+ /* If we're shutting down, we don't do any more process monitoring */
+ if (shuttingDown)
+ continue;
+
+ entry = find_monitored_pid(pid);
+
+ if (entry != -1)
+ {
+ /* We remove the old entry last, because it frees the name & cmd */
+ launch(processName[entry], processCmd[entry], 1);
+ remove_entry(entry);
+ }
+ }
+}
+
+
+/*
+ * Start up the system, using the awesome power of OpenRC
+ */
+static void init(void)
+{
+ pid_t pid;
+
+ printf("*** init-ng v1.0.1 starting...\n");
+
+ pid = launch("openrc", "/sbin/rc sysinit", 0);
+ waitpid(pid, NULL, 0);
+
+ pid = launch("openrc", "/sbin/rc boot", 0);
+ waitpid(pid, NULL, 0);
+
+ pid = launch("openrc", "/sbin/rc default", 0);
+ waitpid(pid, NULL, 0);
+}
+
+
+static void shut_down(int cmd)
+{
+ pid_t pid;
+
+ shuttingDown = 1;
+ pid = launch("openrc", "/sbin/rc reboot", 0);
+
+ /* We do this because our custom signal handler will repeatedly abort this
+ * call. We probably should do a bit more checking than this, but it seems
+ * to work without any problem as is.
+ */
+ while (waitpid(pid, NULL, 0) != pid);
+
+ sync();
+ reboot(cmd);
+}
+
+
+/*
+ * Connect to PID 1's FIFO to send a command
+ */
+static void do_cmd(char * cmd)
+{
+ FILE * file;
+ size_t ignored;
+
+ file = fopen(fifoPath, "w");
+
+ if (file == NULL)
+ {
+ perror("do_cmd: fopen");
+ return;
+ }
+
+ ignored = fwrite(cmd, 1, strlen(cmd), file);
+ fclose(file);
+}
+
+
+int main(int argc, char * argv[])
+{
+ char buf[2048], buf2[2048];
+ pid_t pid;
+ int i;
+ FILE * file;
+ size_t read;
+
+ pid = getpid();
+
+ /* If we're not PID 1, then we're (possibly) being asked to run a command */
+ if (pid != 1)
+ {
+ if (argc > 1)
+ {
+ if ((strcmp(argv[1], "poweroff") == 0)
+ || (strcmp(argv[1], "restart") == 0)
+ || (strcmp(argv[1], "halt") == 0)
+ || (strcmp(argv[1], "status") == 0))
+ {
+ do_cmd(argv[1]);
+ }
+ else if (strcmp(argv[1], "test") == 0)
+ {
+ shut_down(RB_POWER_OFF);
+ }
+ else
+ printf("Invalid command\n");
+ }
+ else
+ printf("Usage: poweroff, restart, halt, status, test\n");
+
+ return 1;
+ }
+
+ /* We are PID EINS, so start the system using OpenRC... */
+ init();
+
+ /* Launch TTYs...
+ * N.B.: To be a drop in replacement for SysV init, we really should read
+ * and parse the entries in /etc/inittab; at least the c entries...
+ */
+ for(i=1; i<=6; i++)
+ {
+ sprintf(buf, "agetty%i", i);
+ sprintf(buf2, "/sbin/agetty tty%i --noclear", i);
+ launch(buf, buf2, 1);
+ }
+
+ /* Install SIGCHLD signal handler to do process monitoring */
+ memset(&action, 0, sizeof(action));
+ action.sa_handler = handle_sigchld;
+ action.sa_flags = SA_SIGINFO;
+ sigaction(SIGCHLD, &action, NULL);
+
+ /* Create a named pipe to listen on for commands */
+ if (mkfifo(fifoPath, 0600) == -1)
+ {
+ /* This is bad... If this happens, we have no comms */
+ perror("mkfifo");
+ }
+
+ /* Main loop for PID 1. All commands are received and acted upon from here. */
+ while (1)
+ {
+ /* This will block until a command is sent down the pipe... */
+ file = fopen(fifoPath, "r");
+
+ if (file == NULL)
+ {
+ /* Check to see if the signal handler blew things up on us */
+ if (errno == EINTR)
+ continue;
+
+ perror("fopen");
+ continue;
+ }
+
+ /* Grab whatever was shoved into the FIFO */
+ read = fread(buf, 1, 2047, file);
+ buf[read] = 0;
+ fclose(file);
+
+ if (verbose)
+ printf("PID1: Received \"%s\" from FIFO...\n", buf);
+
+ /* Now do something with it... */
+ if (strcmp(buf, "poweroff") == 0)
+ {
+ shut_down(RB_POWER_OFF);
+ }
+ else if (strcmp(buf, "restart") == 0)
+ {
+ shut_down(RB_AUTOBOOT);
+ }
+ else if (strcmp(buf, "halt") == 0)
+ {
+ shut_down(RB_HALT_SYSTEM);
+ }
+ else if (strcmp(buf, "status") == 0)
+ {
+ printf("[Status placeholder]\n");
+ }
+ }
+
+ /* We should never get here... */
+ return 0;
+}
+
projects / init-ng / commitdiff