qemu.py: redirect qemu outputs on --log

This allows to redirect qemu log output based on recent QemuNyx changes.

When building QemuNyx in debug mode, additional output can be produced via
the 'nyx' log facility. Enable this by default when --log is given.

kafl_fuzzer/worker/qemu.py

@@ -110,10 +110,10 @@ def __init__(self, pid, config, debug_mode=False, notifiers=True, resume=False):
 
         self.cmd.extend(["-m", str(config.qemu_memory)])
 
-        if self.debug_mode and self.config.log:
-            #self.cmd.extend("-trace", "events=/tmp/events"])
-            #self.cmd.extend("-d", "kafl", "-D", "self.qemu_trace_log"])
-            pass
+        if self.config.log:
+            self.cmd.extend(["-d", "nyx", "-D", self.qemu_trace_log])
+            #self.cmd.extend(["-d", "kafl,trace:kvm*"])
+            #self.cmd.extend(["-trace", "events=/tmp/events"])
 
         if self.config.gdbserver:
             self.cmd.extend(["-s", "-S"])