diff -r 1b1f8f32fe86 -r 33a3a5f7c2ea src/SConscript
--- a/src/SConscript	Thu Jun 24 15:34:21 2010 -0400
+++ b/src/SConscript	Mon Jul 05 17:25:01 2010 -0700
@@ -133,14 +133,18 @@
 
         arcpath = path + [ self.basename ]
         abspath = self.snode.abspath
-        if not exists(abspath):
+        if exists(abspath):
+            srcpath = self.snode.path
+        else:
             abspath = self.tnode.abspath
+            srcpath = None
 
         self.package = package
         self.modname = modname
         self.modpath = modpath
         self.arcname = joinpath(*arcpath)
         self.abspath = abspath
+        self.srcpath = srcpath
         self.compiled = File(self.filename + 'c')
         self.assembly = File(self.filename + '.s')
         self.symname = "PyEMB_" + PySource.invalid_sym_char.sub('_', modpath)
@@ -929,12 +933,18 @@
     dst = file(str(target[0]), 'w')
 
     def dump_mod(sym, endchar=','):
+        def c_str(string):
+            if string is None:
+                return "0"
+            return '"%s"' % string
         pysource = PySource.symnames[sym]
-        print >>dst, '    { "%s",' % pysource.arcname
-        print >>dst, '      "%s",' % pysource.modpath
-        print >>dst, '       %s_beg, %s_end,' % (sym, sym)
-        print >>dst, '       %s_end - %s_beg,' % (sym, sym)
-        print >>dst, '       *(int *)%s_end }%s'  % (sym, endchar)
+        print >>dst, '    { %s,' % c_str(pysource.arcname)
+        print >>dst, '      %s,' % c_str(pysource.abspath)
+        print >>dst, '      %s,' % c_str(pysource.srcpath)
+        print >>dst, '      %s,' % c_str(pysource.modpath)
+        print >>dst, '      %s_beg, %s_end,' % (sym, sym)
+        print >>dst, '      %s_end - %s_beg,' % (sym, sym)
+        print >>dst, '      *(int *)%s_end }%s'  % (sym, endchar)
     
     print >>dst, '#include "sim/init.hh"'
 
@@ -953,7 +963,7 @@
             # Skip the importer since we've already exported it
             continue
         dump_mod(sym)
-    print >>dst, "    { 0, 0, 0, 0, 0, 0 }"
+    print >>dst, "    { 0, 0, 0, 0, 0, 0, 0, 0 }"
     print >>dst, "};"
 
 
diff -r 1b1f8f32fe86 -r 33a3a5f7c2ea src/python/importer.py
--- a/src/python/importer.py	Thu Jun 24 15:34:21 2010 -0400
+++ b/src/python/importer.py	Mon Jul 05 17:25:01 2010 -0700
@@ -33,11 +33,11 @@
     def __init__(self):
         self.modules = {}
 
-    def add_module(self, filename, modpath, code):
+    def add_module(self, filename, abspath, srcpath, modpath, code):
         if modpath in self.modules:
             raise AttributeError, "%s already found in importer"
 
-        self.modules[modpath] = (filename, code)
+        self.modules[modpath] = (filename, abspath, srcpath, code)
 
     def find_module(self, fullname, path):
         if fullname in self.modules:
@@ -59,7 +59,13 @@
 
         try:
             mod.__loader__ = self
-            srcfile,code = self.modules[fullname]
+            srcfile,abspath,srcpath,code = self.modules[fullname]
+
+            override = os.environ.get('M5_OVERRIDE', 'false').lower()
+            if override in ('true', 'yes') and  os.path.exists(abspath):
+                src = file(abspath, 'r').read()
+                code = compile(src, abspath, 'exec')
+
             if os.path.basename(srcfile) == '__init__.py':
                 mod.__path__ = fullname.split('.')
             mod.__file__ = srcfile
diff -r 1b1f8f32fe86 -r 33a3a5f7c2ea src/sim/init.hh
--- a/src/sim/init.hh	Thu Jun 24 15:34:21 2010 -0400
+++ b/src/sim/init.hh	Mon Jul 05 17:25:01 2010 -0700
@@ -37,6 +37,8 @@
 struct EmbeddedPyModule
 {
     const char *filename;
+    const char *abspath;
+    const char *srcpath;
     const char *modpath;
     const char *code;
     const char *code_end;
diff -r 1b1f8f32fe86 -r 33a3a5f7c2ea src/sim/init.cc
--- a/src/sim/init.cc	Thu Jun 24 15:34:21 2010 -0400
+++ b/src/sim/init.cc	Mon Jul 05 17:25:01 2010 -0700
@@ -154,7 +154,8 @@
     while (pymod->filename) {
         PyObject *code = getCode(pymod);
         PyObject *result = PyObject_CallMethod(module, PyCC("add_module"),
-            PyCC("ssO"), pymod->filename, pymod->modpath, code);
+            PyCC("ssssO"), pymod->filename, pymod->abspath, pymod->srcpath,
+            pymod->modpath, code);
         if (!result) {
             PyErr_Print();
             return 1;