Read current options from a shadow file rather than the config file

The list of current options needs to be up-to-date, so we can't just use
historical data.

Users may edit the default config file (`include/tf-psa-crypto/crypto_config.h`
or `include/mbedtls/mbedtls_config.h`). One of the reasons we use the list of
config options is to prevent users from defining internal macros in their
config file (in code generated by `generated_config_checks.py`). An internal
macro is one that isn't listed in the official config file. So we need to
know what macros are listed in the official config file, regardless of edits
to the current config file.

Hence we read a "shadow file" which contains the official list of options,
rather than the "live" config file. This file will need to be kept
up-to-date during development, but is not user-editable.

Signed-off-by: Gilles Peskine <[email protected]>

scripts/mbedtls_framework/config_macros.py

@@ -26,10 +26,19 @@ class ConfigMacros:
         """The set of internal option-like macros in this product."""
         return self._internal
 
+    @staticmethod
+    def _load_file(filename: str) -> FrozenSet[str]:
+        """Load macro names from the given file."""
+        with open(filename, encoding='ascii') as input_:
+            return frozenset(line.strip()
+                             for line in input_)
+
 
 class Current(ConfigMacros):
     """Information about config-like macros parsed from the source code."""
 
+    _SHADOW_FILE = 'scripts/data_files/config-options-current.txt'
+
     _PUBLIC_CONFIG_HEADERS = [
         'include/mbedtls/mbedtls_config.h',
         'include/psa/crypto_config.h',
@@ -63,6 +72,10 @@ class Current(ConfigMacros):
                          for filename in self._list_files(patterns)
                          for element in self._search_file(filename))
 
+    def shadow_file_path(self) -> str:
+        """The path to the option list shadow file."""
+        return os.path.join(self._root, self._submodule, self._SHADOW_FILE)
+
     def __init__(self, submodule: str = '') -> None:
         """Look for macros defined in the given submodule's source tree.
 
@@ -70,7 +83,8 @@ class Current(ConfigMacros):
         """
         self._root = build_tree.guess_project_root()
         self._submodule = submodule
-        public = self._search_files(self._PUBLIC_CONFIG_HEADERS)
+        shadow_file = self.shadow_file_path()
+        public = self._load_file(shadow_file)
         adjusted = self._search_files(self._ADJUST_CONFIG_HEADERS)
         super().__init__(public, adjusted)
 
@@ -81,12 +95,10 @@ class History(ConfigMacros):
     Load files created by ``framework/scripts/save_config_history.sh``.
     """
 
-    def _load_file(self, basename: str) -> FrozenSet[str]:
+    def _load_history_file(self, basename: str) -> FrozenSet[str]:
         """Load macro names from the given file in the history directory."""
         filename = os.path.join(self._history_dir, basename)
-        with open(filename, encoding='ascii') as input_:
-            return frozenset(line.strip()
-                             for line in input_)
+        return self._load_file(filename)
 
     def __init__(self, project: str, version: str) -> None:
         """Read information about the given project at the given version.
@@ -94,6 +106,6 @@ class History(ConfigMacros):
         The information must be present in history files in the framework.
         """
         self._history_dir = os.path.join(build_tree.framework_root(), 'history')
-        public = self._load_file(f'config-options-{project}-{version}.txt')
-        adjusted = self._load_file(f'config-adjust-{project}-{version}.txt')
+        public = self._load_history_file(f'config-options-{project}-{version}.txt')
+        adjusted = self._load_history_file(f'config-adjust-{project}-{version}.txt')
         super().__init__(public, adjusted)