feat(core/rust): Add obj_module! macro

[no changelog]

Co-authored-by: Martin Milata <martin@martinmilata.cz>

core/embed/rust/build.rs

@@ -115,7 +115,10 @@ fn generate_micropython_bindings() {
         .allowlist_function("mp_hal_ticks_ms")
         .allowlist_function("mp_hal_delay_ms")
         // typ
-        .allowlist_var("mp_type_type");
+        .allowlist_var("mp_type_type")
+        // module
+        .allowlist_type("mp_obj_module_t")
+        .allowlist_var("mp_type_module");
 
     // `ffi::mp_map_t` type is not allowed to be `Clone` or `Copy` because we tie it
     // to the data lifetimes with the `MapRef` type, see `src/micropython/map.rs`.

core/embed/rust/src/micropython/macros.rs

@@ -1,3 +1,4 @@
+/// Create an object for an exported function taking 1 arg.
 macro_rules! obj_fn_1 {
     ($f:expr) => {{
         #[allow(unused_unsafe)]
@@ -14,6 +15,7 @@ macro_rules! obj_fn_1 {
     }};
 }
 
+/// Create an object for an exported function taking 2 args.
 macro_rules! obj_fn_2 {
     ($f:expr) => {{
         #[allow(unused_unsafe)]
@@ -30,6 +32,7 @@ macro_rules! obj_fn_2 {
     }};
 }
 
+/// Create an object for an exported function taking 3 args.
 macro_rules! obj_fn_3 {
     ($f:expr) => {{
         #[allow(unused_unsafe)]
@@ -46,6 +49,7 @@ macro_rules! obj_fn_3 {
     }};
 }
 
+/// Create an object for an exported function taking a variable number of args.
 macro_rules! obj_fn_var {
     ($min:expr, $max:expr, $f:expr) => {{
         #[allow(unused_unsafe)]
@@ -63,6 +67,7 @@ macro_rules! obj_fn_var {
     }};
 }
 
+/// Create an object for an exported function taking key-value args.
 macro_rules! obj_fn_kw {
     ($min:expr, $f:expr) => {{
         #[allow(unused_unsafe)]
@@ -111,6 +116,7 @@ macro_rules! obj_dict {
     }};
 }
 
+/// Compose a `Type` object definition.
 macro_rules! obj_type {
     (name: $name:expr,
      $(locals: $locals:expr,)?
@@ -134,8 +140,8 @@ macro_rules! obj_type {
             $(call = Some($call_fn);)?
 
             // TODO: This is safe only if we pass in `Dict` with fixed `Map` (created by
-            // `Map::fixed()`), because only then will Micropython treat `locals_dict` as
-            // immutable, and make the mutable cast safe.
+            // `Map::fixed()`, usually through `obj_map!`), because only then will
+            // MicroPython treat `locals_dict` as immutable, and make the mutable cast safe.
             #[allow(unused_mut)]
             #[allow(unused_assignments)]
             let mut locals_dict = ::core::ptr::null_mut();
@@ -164,3 +170,36 @@ macro_rules! obj_type {
         }
     }};
 }
+
+/// Construct an extmod definition.
+macro_rules! obj_module {
+    ($($key:expr => $val:expr),*) => ({
+        #[allow(unused_unsafe)]
+        unsafe {
+            use $crate::micropython::ffi;
+
+            static DICT: ffi::mp_obj_dict_t = ffi::mp_obj_dict_t {
+                base: ffi::mp_obj_base_t {
+                    /// SAFETY: Reasonable to assume the pointer stays valid.
+                    type_: unsafe { &ffi::mp_type_dict },
+                },
+                map: Map::from_fixed_static(&[
+                    $(
+                        Map::at($key, $val),
+                    )*
+                ])
+            };
+            ffi::mp_obj_module_t {
+                base: ffi::mp_obj_base_t {
+                    type_: &ffi::mp_type_module,
+                },
+                // This is safe only because we are passing in a static dict with fixed `Map`
+                // (created by `Map::from_fixed_static()`). Only then will MicroPython treat
+                // `globals` as immutable, making the mutable cast safe.
+                globals: &DICT as *const _ as *mut _,
+            }
+    }});
+    ($($key:expr => $val:expr),* ,) => ({
+        obj_module!($($key => $val),*)
+    });
+}

core/embed/rust/src/micropython/mod.rs

@@ -10,6 +10,7 @@ pub mod gc;
 pub mod iter;
 pub mod list;
 pub mod map;
+pub mod module;
 pub mod obj;
 pub mod qstr;
 pub mod runtime;

core/embed/rust/src/micropython/module.rs

@@ -0,0 +1,6 @@
+use super::ffi;
+
+pub type Module = ffi::mp_obj_module_t;
+
+// SAFETY: We are in a single-threaded environment.
+unsafe impl Sync for Module {}