[PATCH 3/9] Add a minimalist init program

[Justus Winter]

---
 init/Makefile |   24 +++++++++
 init/init.c   |  152 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 176 insertions(+)
 create mode 100644 init/Makefile
 create mode 100644 init/init.c

diff --git a/init/Makefile b/init/Makefile
new file mode 100644
index 0000000..07b8026
--- /dev/null
+++ b/init/Makefile
@@ -0,0 +1,24 @@
+#
+#   Copyright (C) 2013 Free Software Foundation, Inc.
+#
+#   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 2, 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 <http://www.gnu.org/licenses/>.
+
+dir := init
+makemode := server
+
+SRCS = init.c
+OBJS = $(SRCS:.c=.o)
+target = init
+
+include ../Makeconf
diff --git a/init/init.c b/init/init.c
new file mode 100644
index 0000000..92199c4
--- /dev/null
+++ b/init/init.c
@@ -0,0 +1,152 @@
+/* A minimalist init for the Hurd
+
+   Copyright (C) 2013 Free Software Foundation, Inc.
+   This file is part of the GNU Hurd.
+
+   The GNU Hurd 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 2, or (at your option)
+   any later version.
+
+   The GNU Hurd 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 the Hurd.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <argp.h>
+#include <error.h>
+#include <hurd.h>
+#include <signal.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <version.h>
+
+const char *argp_program_version = STANDARD_HURD_VERSION (init);
+static pid_t child_pid;
+static int single;
+
+static struct argp_option
+options[] =
+{
+  /* XXX */
+  {"single-user", 's', NULL, 0, "Startup system in single-user mode"},
+  {NULL, 'a', NULL, 0, "Ignored for compatibility with sysvinit"},
+  {0}
+};
+
+static char doc[] = "A minimalist init for the Hurd";
+
+static error_t
+parse_opt (int key, char *arg, struct argp_state *state)
+{
+  switch (key)
+    {
+    case 's':
+      single = 1;
+      break;
+
+    case 'a':
+      /* Ignored.  */
+      break;
+
+    default:
+      return ARGP_ERR_UNKNOWN;
+    }
+
+  return 0;
+}
+
+void
+sigchld_handler(int signal)
+{
+  /* A child died.  Find its status.  */
+  int status;
+  pid_t pid;
+
+  while (1)
+    {
+      pid = waitpid (WAIT_ANY, &status, WNOHANG | WUNTRACED);
+      if (pid <= 0)
+       break;          /* No more children.  */
+
+      error (0, 0, "child %i died", pid);
+
+      /* Since we are init, orphaned processes get reparented to us and
+        alas, all our adopted children eventually die.  Woe is us.  We
+        just need to reap the zombies to relieve the proc server of
+        its burden, and then we can forget about the little varmints.  */
+
+      if (pid == child_pid)
+       {
+         /* The big magilla bit the dust.  */
+         child_pid = -1;
+
+         char *desc = NULL;
+         if (WIFSIGNALED (status))
+           asprintf (&desc, "terminated abnormally (%s)",
+                     strsignal (WTERMSIG (status)));
+         else if (WIFSTOPPED (status))
+           asprintf (&desc, "stopped abnormally (%s)",
+                     strsignal (WTERMSIG (status)));
+         else if (WEXITSTATUS (status) == 0)
+           desc = strdup ("finished");
+         else
+           asprintf (&desc, "exited with status %d",
+                     WEXITSTATUS (status));
+
+         error (0, 0, "child %s", desc);
+         free (desc);
+
+         /* XXX: launch emergency shell.  */
+         error (23, 0, "panic!!");
+       }
+    }
+}
+
+int
+main (int argc, char **argv)
+{
+  struct argp argp = { options, parse_opt, 0, doc };
+  argp_parse (&argp, argc, argv, 0, 0, 0);
+
+  if (getpid () != 1)
+    error (1, 0, "can only be run as PID 1");
+
+  struct sigaction sa;
+  sa.sa_handler = SIG_IGN;
+  sa.sa_flags = 0;
+  sigemptyset (&sa.sa_mask);
+
+  sigaction (SIGHUP, &sa, NULL);
+  sigaction (SIGINT, &sa, NULL);
+  sigaction (SIGQUIT, &sa, NULL);
+  sigaction (SIGTERM, &sa, NULL);
+  sigaction (SIGUSR1, &sa, NULL);
+  sigaction (SIGUSR2, &sa, NULL);
+  sigaction (SIGTSTP, &sa, NULL);
+
+  sa.sa_handler = sigchld_handler;
+  sa.sa_flags |= SA_RESTART;
+  sigaction (SIGCHLD, &sa, NULL);
+
+  char *args[] = { "/etc/hurd/runsystem.hurd", NULL };
+
+  switch (child_pid = fork ())
+    {
+    case -1:
+      error (1, errno, "failed to fork");
+    case 0:
+      execv (args[0], args);
+      error (2, errno, "failed to execv child");
+    }
+
+  select (0, NULL, NULL, NULL, NULL);
+  /* not reached.  */
+  return 0;
+}
-- 
1.7.10.4