stubdom: fix using minios frontends directly when libc is actived

diff -r 4f7f01de4239 extras/mini-os/blkfront.c
@@ -63,7 +63,8 @@
     struct blkfront_dev *dev = data;
     int fd = dev->fd;
 
-    files[fd].read = 1;
+    if (fd != -1)
+        files[fd].read = 1;
 #endif
     wake_up(&blkfront_queue);
 }

@@ -105,6 +106,9 @@
     dev = malloc(sizeof(*dev));
     memset(dev, 0, sizeof(*dev));
     dev->nodename = strdup(nodename);
+#ifdef HAVE_LIBC
+    dev->fd = -1;
+#endif
 
     snprintf(path, sizeof(path), "%s/backend-id", nodename);
     dev->dom = xenbus_read_integer(path); 

@@ -424,8 +428,10 @@
 
 moretodo:
 #ifdef HAVE_LIBC
-    files[dev->fd].read = 0;
-    mb(); /* Make sure to let the handler set read to 1 before we start looking at the ring */
+    if (dev->fd != -1) {
+        files[dev->fd].read = 0;
+        mb(); /* Make sure to let the handler set read to 1 before we start looking at the ring */
+    }
 #endif
 
     rp = dev->ring.sring->rsp_prod;

diff -r 4f7f01de4239 extras/mini-os/fbfront.c
@@ -44,7 +44,8 @@
     struct kbdfront_dev *dev = data;
     int fd = dev->fd;
 
-    files[fd].read = 1;
+    if (fd != -1)
+        files[fd].read = 1;
 #endif
     wake_up(&kbdfront_queue);
 }

@@ -83,6 +84,9 @@
 
     dev = malloc(sizeof(*dev));
     dev->nodename = strdup(nodename);
+#ifdef HAVE_LIBC
+    dev->fd = -1;
+#endif
 
     snprintf(path, sizeof(path), "%s/backend-id", nodename);
     dev->dom = xenbus_read_integer(path); 

@@ -179,8 +183,10 @@
     int i;
 
 #ifdef HAVE_LIBC
-    files[dev->fd].read = 0;
-    mb(); /* Make sure to let the handler set read to 1 before we start looking at the ring */
+    if (dev->fd != -1) {
+        files[dev->fd].read = 0;
+        mb(); /* Make sure to let the handler set read to 1 before we start looking at the ring */
+    }
 #endif
 
     prod = page->in_prod;

@@ -198,7 +204,7 @@
     notify_remote_via_evtchn(dev->evtchn);
 
 #ifdef HAVE_LIBC
-    if (cons != prod)
+    if (cons != prod && dev->fd != -1)
         /* still some events to read */
         files[dev->fd].read = 1;
 #endif

@@ -290,7 +296,8 @@
     struct fbfront_dev *dev = data;
     int fd = dev->fd;
 
-    files[fd].read = 1;
+    if (fd != -1)
+        files[fd].read = 1;
 #endif
     wake_up(&fbfront_queue);
 }

@@ -316,8 +323,10 @@
     int i;
 
 #ifdef HAVE_LIBC
-    files[dev->fd].read = 0;
-    mb(); /* Make sure to let the handler set read to 1 before we start looking at the ring */
+    if (dev->fd != -1) {
+        files[dev->fd].read = 0;
+        mb(); /* Make sure to let the handler set read to 1 before we start looking at the ring */
+    }
 #endif
 
     prod = page->in_prod;

@@ -335,7 +344,7 @@
     notify_remote_via_evtchn(dev->evtchn);
 
 #ifdef HAVE_LIBC
-    if (cons != prod)
+    if (cons != prod && dev->fd != -1)
         /* still some events to read */
         files[dev->fd].read = 1;
 #endif

@@ -363,6 +372,9 @@
 
     dev = malloc(sizeof(*dev));
     dev->nodename = strdup(nodename);
+#ifdef HAVE_LIBC
+    dev->fd = -1;
+#endif
 
     snprintf(path, sizeof(path), "%s/backend-id", nodename);
     dev->dom = xenbus_read_integer(path); 

diff -r 4f7f01de4239 extras/mini-os/netfront.c
@@ -259,7 +259,8 @@
     network_tx_buf_gc(dev);
     local_irq_restore(flags);
 
-    files[fd].read = 1;
+    if (fd != -1)
+        files[fd].read = 1;
     wake_up(&netfront_queue);
 }
 #endif

@@ -323,6 +324,9 @@
     dev = malloc(sizeof(*dev));
     memset(dev, 0, sizeof(*dev));
     dev->nodename = strdup(nodename);
+#ifdef HAVE_LIBC
+    dev->fd = -1;
+#endif
 
     printk("net TX ring size %d\n", NET_TX_RING_SIZE);
     printk("net RX ring size %d\n", NET_RX_RING_SIZE);

@@ -610,7 +614,7 @@
 
     local_irq_save(flags);
     network_rx(dev);
-    if (!dev->rlen)
+    if (!dev->rlen && fd != -1)
 	/* No data for us, make select stop returning */
 	files[fd].read = 0;
     /* Before re-enabling the interrupts, in case a packet just arrived in the