lguest: Reboot support

Reboot Implemented

(Prevent fd leak, fix style and fix documentation --RR)

Signed-off-by: Balaji Rao <balajirrao@gmail.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 30 insertions, 2 deletions

diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c
index 9b0e322118b5..86cac3e622ab 100644
--- a/Documentation/lguest/lguest.c
+++ b/Documentation/lguest/lguest.c
@@ -153,6 +153,9 @@ struct virtqueue
         void (*handle_output)(int fd, struct virtqueue *me);
 };
 
+/* Remember the arguments to the program so we can "reboot" */
+static char **main_args;
+
 /* Since guest is UP and we don't run at the same time, we don't need barriers.
  * But I include them in the code in case others copy it. */
 #define wmb()
@@ -1489,7 +1492,9 @@ static void setup_block_file(const char *filename)
 
         /* Create stack for thread and run it */
         stack = malloc(32768);
-        if (clone(io_thread, stack + 32768, CLONE_VM, dev) == -1)
+        /* SIGCHLD - We dont "wait" for our cloned thread, so prevent it from
+         * becoming a zombie. */
+        if (clone(io_thread, stack + 32768,  CLONE_VM | SIGCHLD, dev) == -1)
                 err(1, "Creating clone");
 
         /* We don't need to keep the I/O thread's end of the pipes open. */
@@ -1499,7 +1504,21 @@ static void setup_block_file(const char *filename)
         verbose("device %u: virtblock %llu sectors\n",
                 devices.device_num, cap);
 }
-/* That's the end of device setup. */
+/* That's the end of device setup. :*/
+
+/* Reboot */
+static void __attribute__((noreturn)) restart_guest(void)
+{
+        unsigned int i;
+
+        /* Closing pipes causes the waker thread and io_threads to die, and
+         * closing /dev/lguest cleans up the Guest.  Since we don't track all
+         * open fds, we simply close everything beyond stderr. */
+        for (i = 3; i < FD_SETSIZE; i++)
+                close(i);
+        execv(main_args[0], main_args);
+        err(1, "Could not exec %s", main_args[0]);
+}
 
 /*L:220 Finally we reach the core of the Launcher, which runs the Guest, serves
  * its input and output, and finally, lays it to rest. */
@@ -1523,6 +1542,9 @@ static void __attribute__((noreturn)) run_guest(int lguest_fd)
                         char reason[1024] = { 0 };
                         read(lguest_fd, reason, sizeof(reason)-1);
                         errx(1, "%s", reason);
+                /* ERESTART means that we need to reboot the guest */
+                } else if (errno == ERESTART) {
+                        restart_guest();
                 /* EAGAIN means the Waker wanted us to look at some input.
                  * Anything else means a bug or incompatible change. */
                 } else if (errno != EAGAIN)
@@ -1571,6 +1593,12 @@ int main(int argc, char *argv[])
         /* If they specify an initrd file to load. */
         const char *initrd_name = NULL;
 
+        /* Save the args: we "reboot" by execing ourselves again. */
+        main_args = argv;
+        /* We don't "wait" for the children, so prevent them from becoming
+         * zombies. */
+        signal(SIGCHLD, SIG_IGN);
+
         /* First we initialize the device list.  Since console and network
          * device receive input from a file descriptor, we keep an fdset
          * (infds) and the maximum fd number (max_infd) with the head of the