From 53cb351673ba99cbefec968760e9f6f702722c58 Mon Sep 17 00:00:00 2001
From: Chris Jones <cmsj@tenshu.net>
Date: Mon, 16 Apr 2018 21:17:50 +0100
Subject: [PATCH] Add initial work on a script that uses libclang to statically
 analyse extension code for potential _lua_stackguard usage

---
 scripts/lua_stackguard_enforcer.py | 115 +++++++++++++++++++++++++++++
 1 file changed, 115 insertions(+)
 create mode 100755 scripts/lua_stackguard_enforcer.py

diff --git a/scripts/lua_stackguard_enforcer.py b/scripts/lua_stackguard_enforcer.py
new file mode 100755
index 000000000..684ecde82
--- /dev/null
+++ b/scripts/lua_stackguard_enforcer.py
@@ -0,0 +1,115 @@
+#!/usr/bin/env python
+"""
+Enforce the usage of Hammerspoon's Lua stack guarding macros
+"""
+
+from __future__ import print_function
+import sys
+
+from clang.cindex import Config
+from clang.cindex import Index
+from clang.cindex import CursorKind
+from clang.cindex import TypeKind
+
+FILENAME = "Unknown"
+
+
+def is_function(node):
+    """Is the given node a C function or an ObjC method?"""
+    return node.kind in [CursorKind.FUNCTION_DECL,
+                         CursorKind.OBJC_INSTANCE_METHOD_DECL,
+                         CursorKind.OBJC_CLASS_METHOD_DECL]
+
+
+def is_implementation(node):
+    """Is the given node an ObjC @implementation?"""
+    return node.kind == CursorKind.OBJC_IMPLEMENTATION_DECL
+
+
+def is_luastate_param(node):
+    """Is the given node a lua_State parameter?"""
+    # We need the underlying text tokens to detect the typedef 'lua_State'
+    tokens = [x.spelling for x in node.get_tokens()]
+    try:
+        return node.type.kind == TypeKind.POINTER and \
+            tokens[0] == 'lua_State'
+    except IndexError:
+        return False
+
+
+def is_lua_call(node):
+    """Is the given node a Lua->C call?"""
+    params = [x for x in node.get_children() if x.kind == CursorKind.PARM_DECL]
+    return node.result_type.kind == TypeKind.INT and len(params) == 1 and \
+        is_luastate_param(params[0])
+
+
+def build_tree(node, recurse=True):
+    """Build a tree below a node"""
+    if recurse:
+        children = [build_tree(c) for c in node.get_children()]
+    else:
+        children = ['skipped']
+    return {'node': node,
+            'kind': node.kind,
+            'spelling': node.spelling,
+            'tokens': ' '.join([x.spelling for x in node.get_tokens()]),
+            'children': children}
+
+
+def contains_lua_calls(item):
+    """Check if a node contains any Lua API calls"""
+    if 'lua_' in item['tokens']:
+        return True
+    if 'luaL_' in item['tokens']:
+        return True
+    if 'LuaSkin' in item['tokens']:
+        return True
+    return False
+
+
+def main(filename):
+    """Main function"""
+    functions = []
+    tree = []
+    Config.set_library_file(
+        "/Library/Developer/CommandLineTools/usr/lib/libclang.dylib")
+
+    index = Index.create()
+    ast = index.parse(None, [filename])
+    if not ast:
+        print("Unable to parse file")
+        sys.exit(1)
+
+    # Step 1: Find all the C/ObjC functions
+    functions = [x for x in ast.cursor.get_children() if is_function(x)]
+
+    # Step 1a: Add in ObjC class methods
+    for item in ast.cursor.get_children():
+        if is_implementation(item):
+            functions += [x for x in item.get_children() if is_function(x)]
+
+    # Step 2: Filter out all of the functions that are Lua->C calls
+    functions = [x for x in functions if not is_lua_call(x)]
+
+    # Step 3: Recursively walk the remaining functions
+    tree = [build_tree(x, False) for x in functions]
+
+    # Step 4: Filter the functions down to those which contain Lua calls
+    tree = [x for x in tree if contains_lua_calls(x)]
+
+    for thing in tree:
+        stacktxt = "NO STACKGUARD"
+        hasstackentry = "_lua_stackguard_entry" in thing['tokens']
+        hasstackexit = "_lua_stackguard_exit" in thing['tokens']
+        if hasstackentry and hasstackexit:
+            continue
+        if hasstackentry and not hasstackexit:
+            stacktxt = "STACK ENTRY, BUT NO EXIT"
+        if hasstackexit and not hasstackentry:
+            stacktxt = "STACK EXIT, BUT NO ENTRY (THIS IS A CRASH)"
+        print(u"%s :: %s :: %s" % (filename, thing['spelling'], stacktxt))
+
+
+if __name__ == '__main__':
+    main(sys.argv[1])