blkdebug: Add events and rules

Block drivers can trigger a blkdebug event whenever they reach a place where it
could be useful to inject an error for testing/debugging purposes.

Rules are read from a blkdebug config file and describe which action is taken
when an event is triggered. For now this is only injecting an error (with a few
options) or changing the state (which is an integer). Rules can be declared to
be active only in a specific state; this way later rules can distiguish on
which path we came to trigger their event.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block.c

@@ -1535,6 +1535,18 @@ int bdrv_load_vmstate(BlockDriverState *bs, uint8_t *buf,
     return drv->bdrv_load_vmstate(bs, buf, pos, size);
 }
 
+void bdrv_debug_event(BlockDriverState *bs, BlkDebugEvent event)
+{
+    BlockDriver *drv = bs->drv;
+
+    if (!drv || !drv->bdrv_debug_event) {
+        return;
+    }
+
+    return drv->bdrv_debug_event(bs, event);
+
+}
+
 /**************************************************************/
 /* handling of snapshots */