python: Add mechanism to override code compiled into the exectuable

If the user sets the environment variable M5_OVERRIDE_PY_SOURCE to
True, then imports that would normally find python code compiled into
the executable will instead first check in the absolute location where
the code was found during the build of the executable.  This only
works for files in the src (or extras) directories, not automatically
generated files.

This is a developer feature!

4 files changed, 23 insertions, 10 deletions

diff --git a/src/SConscript b/src/SConscript
index 51616701b..5879fbc93 100644
--- a/src/SConscript
+++ b/src/SConscript
@@ -929,12 +929,17 @@ def pythonInit(target, source, env):
     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.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 +958,7 @@ def pythonInit(target, source, env):
             # 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 }"
     print >>dst, "};"
 
 
diff --git a/src/python/importer.py b/src/python/importer.py
index fe099fdb8..4e364873f 100644
--- a/src/python/importer.py
+++ b/src/python/importer.py
@@ -33,11 +33,11 @@ class CodeImporter(object):
     def __init__(self):
         self.modules = {}
 
-    def add_module(self, filename, modpath, code):
+    def add_module(self, filename, abspath, modpath, code):
         if modpath in self.modules:
             raise AttributeError, "%s already found in importer"
 
-        self.modules[modpath] = (filename, code)
+        self.modules[modpath] = (filename, abspath, code)
 
     def find_module(self, fullname, path):
         if fullname in self.modules:
@@ -59,7 +59,13 @@ class CodeImporter(object):
 
         try:
             mod.__loader__ = self
-            srcfile,code = self.modules[fullname]
+            srcfile,abspath,code = self.modules[fullname]
+
+            override = os.environ.get('M5_OVERRIDE_PY_SOURCE', '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 --git a/src/sim/init.cc b/src/sim/init.cc
index 8057c9369..1ec09369d 100644
--- a/src/sim/init.cc
+++ b/src/sim/init.cc
@@ -154,7 +154,8 @@ initM5Python()
     while (pymod->filename) {
         PyObject *code = getCode(pymod);
         PyObject *result = PyObject_CallMethod(module, PyCC("add_module"),
-            PyCC("ssO"), pymod->filename, pymod->modpath, code);
+            PyCC("sssO"), pymod->filename, pymod->abspath, pymod->modpath,
+            code);
         if (!result) {
             PyErr_Print();
             return 1;
diff --git a/src/sim/init.hh b/src/sim/init.hh
index b0f29bf30..76cdcb74e 100644
--- a/src/sim/init.hh
+++ b/src/sim/init.hh
@@ -37,6 +37,7 @@
 struct EmbeddedPyModule
 {
     const char *filename;
+    const char *abspath;
     const char *modpath;
     const char *code;
     const char *code_end;