From 659245acc7dcc28e345b8dfa50571102f4f07728 Mon Sep 17 00:00:00 2001
From: sfan5 <sfan5@live.de>
Date: Wed, 8 Apr 2020 20:14:08 +0200
Subject: Work around LuaJIT issues on aarch64 (#9614)

- Move the text segment below the 47-bit limit, needed for script_exception_wrapper which must be lightuserdata
- Replace CUSTOM_RIDX_SCRIPTAPI with full userdata
---
 src/script/common/c_internal.h    | 9 +++++++++
 src/script/cpp_api/s_base.cpp     | 4 ++++
 src/script/cpp_api/s_security.cpp | 7 ++++++-
 src/script/lua_api/l_base.cpp     | 7 ++++++-
 4 files changed, 25 insertions(+), 2 deletions(-)

(limited to 'src/script')

diff --git a/src/script/common/c_internal.h b/src/script/common/c_internal.h
index d8cf3fe76..747400769 100644
--- a/src/script/common/c_internal.h
+++ b/src/script/common/c_internal.h
@@ -54,6 +54,15 @@ extern "C" {
 #define CUSTOM_RIDX_CURRENT_MOD_NAME    (CUSTOM_RIDX_BASE + 2)
 #define CUSTOM_RIDX_BACKTRACE           (CUSTOM_RIDX_BASE + 3)
 
+// Determine if CUSTOM_RIDX_SCRIPTAPI will hold a light or full userdata
+#if defined(__aarch64__) && USE_LUAJIT
+/* LuaJIT has a 47-bit limit for lightuserdata on this platform and we cannot
+ * assume that the ScriptApi class was allocated at a fitting address. */
+#define INDIRECT_SCRIPTAPI_RIDX 1
+#else
+#define INDIRECT_SCRIPTAPI_RIDX 0
+#endif
+
 // Pushes the error handler onto the stack and returns its index
 #define PUSH_ERROR_HANDLER(L) \
 	(lua_rawgeti((L), LUA_REGISTRYINDEX, CUSTOM_RIDX_BACKTRACE), lua_gettop((L)))
diff --git a/src/script/cpp_api/s_base.cpp b/src/script/cpp_api/s_base.cpp
index ecb1ba39b..f234a15d4 100644
--- a/src/script/cpp_api/s_base.cpp
+++ b/src/script/cpp_api/s_base.cpp
@@ -90,7 +90,11 @@ ScriptApiBase::ScriptApiBase(ScriptingType type):
 		luaL_openlibs(m_luastack);
 
 	// Make the ScriptApiBase* accessible to ModApiBase
+#if INDIRECT_SCRIPTAPI_RIDX
+	*(void **)(lua_newuserdata(m_luastack, sizeof(void *))) = this;
+#else
 	lua_pushlightuserdata(m_luastack, this);
+#endif
 	lua_rawseti(m_luastack, LUA_REGISTRYINDEX, CUSTOM_RIDX_SCRIPTAPI);
 
 	// Add and save an error handler
diff --git a/src/script/cpp_api/s_security.cpp b/src/script/cpp_api/s_security.cpp
index b5abcfb5d..2afa3a191 100644
--- a/src/script/cpp_api/s_security.cpp
+++ b/src/script/cpp_api/s_security.cpp
@@ -499,7 +499,12 @@ bool ScriptApiSecurity::checkPath(lua_State *L, const char *path,
 
 	// Get server from registry
 	lua_rawgeti(L, LUA_REGISTRYINDEX, CUSTOM_RIDX_SCRIPTAPI);
-	ScriptApiBase *script = (ScriptApiBase *) lua_touserdata(L, -1);
+	ScriptApiBase *script;
+#if INDIRECT_SCRIPTAPI_RIDX
+	script = (ScriptApiBase *) *(void**)(lua_touserdata(L, -1));
+#else
+	script = (ScriptApiBase *) lua_touserdata(L, -1);
+#endif
 	lua_pop(L, 1);
 	const IGameDef *gamedef = script->getGameDef();
 	if (!gamedef)
diff --git a/src/script/lua_api/l_base.cpp b/src/script/lua_api/l_base.cpp
index 8486fc7bc..c980bba39 100644
--- a/src/script/lua_api/l_base.cpp
+++ b/src/script/lua_api/l_base.cpp
@@ -30,7 +30,12 @@ ScriptApiBase *ModApiBase::getScriptApiBase(lua_State *L)
 {
 	// Get server from registry
 	lua_rawgeti(L, LUA_REGISTRYINDEX, CUSTOM_RIDX_SCRIPTAPI);
-	ScriptApiBase *sapi_ptr = (ScriptApiBase*) lua_touserdata(L, -1);
+	ScriptApiBase *sapi_ptr;
+#if INDIRECT_SCRIPTAPI_RIDX
+	sapi_ptr = (ScriptApiBase*) *(void**)(lua_touserdata(L, -1));
+#else
+	sapi_ptr = (ScriptApiBase*) lua_touserdata(L, -1);
+#endif
 	lua_pop(L, 1);
 	return sapi_ptr;
 }
-- 
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