AP_Scripting: reference script environment directly

Referencing the original function to run is of questionable value and
the only user uses it to grab the script environent from the upvalues.

Instead, use a reference to the script environment table directly.

libraries/AP_Scripting/AP_Scripting.h

@@ -122,8 +122,8 @@ public:
     // PWMSource storage
     uint8_t num_pwm_source;
     AP_HAL::PWMSource *_pwm_source[SCRIPTING_MAX_NUM_PWM_SOURCE];
-    int get_current_ref() { return current_ref; }
-    void set_current_ref(int ref) { current_ref = ref; }
+    int get_current_env_ref() { return current_env_ref; }
+    void set_current_env_ref(int ref) { current_env_ref = ref; }
 
 #if AP_NETWORKING_ENABLED
     // SocketAPM storage
@@ -193,7 +193,7 @@ private:
     bool _stop; // true if scripts should be stopped
 
     static AP_Scripting *_singleton;
-    int current_ref;
+    int current_env_ref;
 };
 
 namespace AP {

libraries/AP_Scripting/lua/src/loadlib.c

@@ -622,26 +622,25 @@ static void findloader (lua_State *L, const char *name) {
 static int ll_require (lua_State *L) {
   const char *name = luaL_checkstring(L, 1);
   lua_settop(L, 1);
-  lua_rawgeti(L, LUA_REGISTRYINDEX, lua_get_current_ref()); /* get the current script */
-  lua_getupvalue(L, 2, 1); /* get the environment of the script */
-  lua_getfield(L, 3, LUA_LOADED_TABLE); /* get _LOADED */
-  lua_getfield(L, 4, name);  /* LOADED[name] */
+  lua_rawgeti(L, LUA_REGISTRYINDEX, lua_get_current_env_ref()); /* get the environment of the current script */
+  lua_getfield(L, 2, LUA_LOADED_TABLE); /* get _LOADED */
+  lua_getfield(L, 3, name);  /* LOADED[name] */
   if (lua_toboolean(L, -1))  /* is it there? */
     return 1;  /* package is already loaded */
   /* else must load package */
   lua_pop(L, 1);  /* remove 'getfield' result */
   findloader(L, name);
-  lua_pushvalue(L, 3); /* push current script's environment */
+  lua_pushvalue(L, 2); /* push current script's environment */
   lua_setupvalue(L, -3, 1); /* set the environment of the module */
   lua_pushstring(L, name);  /* pass name as argument to module loader */
   lua_insert(L, -2);  /* name is 1st argument (before search data) */
   lua_call(L, 2, 1);  /* run loader to load module */
   if (!lua_isnil(L, -1))  /* non-nil return? */
-    lua_setfield(L, 4, name);  /* LOADED[name] = returned value */
-  if (lua_getfield(L, 4, name) == LUA_TNIL) {   /* module set no value? */
+    lua_setfield(L, 3, name);  /* LOADED[name] = returned value */
+  if (lua_getfield(L, 3, name) == LUA_TNIL) {   /* module set no value? */
     lua_pushboolean(L, 1);  /* use true as result */
     lua_pushvalue(L, -1);  /* extra copy to be returned */
-    lua_setfield(L, 4, name);  /* LOADED[name] = true */
+    lua_setfield(L, 3, name);  /* LOADED[name] = true */
   }
   return 1;
 }

libraries/AP_Scripting/lua_bindings.cpp

@@ -1040,10 +1040,10 @@ int SocketAPM_accept(lua_State *L) {
 #endif // AP_NETWORKING_ENABLED
 
 
-int lua_get_current_ref()
+int lua_get_current_env_ref()
 {
     auto *scripting = AP::scripting();
-    return scripting->get_current_ref();
+    return scripting->get_current_env_ref();
 }
 
 // This is used when loading modules with require, lua must only look in enabled directory's

libraries/AP_Scripting/lua_common_defs.h

@@ -10,7 +10,7 @@
   #endif //HAL_OS_FATFS_IO
 #endif // SCRIPTING_DIRECTORY
 
-int lua_get_current_ref();
+int lua_get_current_env_ref();
 const char* lua_get_modules_path();
 void lua_abort(void) __attribute__((noreturn));
 

libraries/AP_Scripting/lua_scripts.cpp

@@ -191,7 +191,8 @@ lua_scripts::script_info *lua_scripts::load_script(lua_State *L, char *filename)
 
 
     create_sandbox(L);
-    lua_setupvalue(L, -2, 1);
+    lua_pushvalue(L, -1); // duplicate environment for reference below
+    lua_setupvalue(L, -3, 1);
 
     const uint32_t loadEnd = AP_HAL::micros();
     const int endMem = lua_gc(L, LUA_GCCOUNT, 0) * 1024 + lua_gc(L, LUA_GCCOUNTB, 0);
@@ -199,8 +200,7 @@ lua_scripts::script_info *lua_scripts::load_script(lua_State *L, char *filename)
     update_stats(filename, loadEnd-loadStart, endMem, loadMem);
 
     new_script->name = filename;
-    lua_pushvalue(L, -1);
-    new_script->lua_ref = luaL_ref(L, LUA_REGISTRYINDEX); // store reference to object for environment purposes
+    new_script->env_ref = luaL_ref(L, LUA_REGISTRYINDEX); // store reference to script's environment
     new_script->run_ref = luaL_ref(L, LUA_REGISTRYINDEX); // store reference to function to run
     new_script->next_run_ms = AP_HAL::millis64() - 1; // force the script to be stale
 
@@ -328,8 +328,8 @@ void lua_scripts::run_next_script(lua_State *L) {
 
     // pop the function to the top of the stack
     lua_rawgeti(L, LUA_REGISTRYINDEX, script->run_ref);
-    // set object for environment purposes
-    AP::scripting()->set_current_ref(script->lua_ref);
+    // set current environment for other users
+    AP::scripting()->set_current_env_ref(script->env_ref);
 
     if(lua_pcall(L, 0, LUA_MULTRET, 0)) {
         if (overtime) {
@@ -412,7 +412,7 @@ void lua_scripts::remove_script(lua_State *L, script_info *script) {
     
     if (L != nullptr) {
         // state could be null if we are force killing all scripts
-        luaL_unref(L, LUA_REGISTRYINDEX, script->lua_ref);
+        luaL_unref(L, LUA_REGISTRYINDEX, script->env_ref);
         luaL_unref(L, LUA_REGISTRYINDEX, script->run_ref);
     }
     _heap.deallocate(script->name);

libraries/AP_Scripting/lua_scripts.h

@@ -62,7 +62,7 @@ private:
     void create_sandbox(lua_State *L);
 
     typedef struct script_info {
-       int lua_ref;          // reference to the loaded script object
+       int env_ref;          // reference to the script's environment table
        int run_ref;          // reference to the function to run
        uint64_t next_run_ms; // time (in milliseconds) the script should next be run at
        uint32_t crc;         // crc32 checksum
@@ -111,7 +111,6 @@ private:
     static HAL_Semaphore error_msg_buf_sem;
     static uint8_t print_error_count;
     static uint32_t last_print_ms;
-    int current_ref;
 
     // XOR of crc32 of running scripts
     static uint32_t loaded_checksum;