Rust: Add crates-to-module adapter

makefiles/cargo-settings.inc.mk

@@ -1,9 +1,3 @@
-# Rust's own version of the target triple / quadruple.
-#
-# This does not have a sane default, and needs to be set in the architecture
-# files.
-# RUST_TARGET = ...
-
 # Setting anything other than "debug" or "release" will necessitate additional
 # -Z unstable-options as of 2021-03 nightlies.
 CARGO_PROFILE ?= release

makefiles/cargo-targets.inc.mk

@@ -1,6 +1,16 @@
 CARGO_COMPILE_COMMANDS = $(BINDIR)/cargo-compile-commands.json
 CARGO_COMPILE_COMMANDS_FLAGS = --clang
 
+# When an application crate is built, it has to use rust_riotmodules_standalone itself to
+# pull in any Rust modules that might be enabled through RIOT's module system.
+# (If the application fails to add the rust_riotmodules_standalone dependency, that will
+# go unnoticed and work fine if none of the catchall-dispatched modules are
+# active -- but if one is enabled, this also serves to ensure the application
+# is not silently built without them, as the feature will not be available to
+# Cargo).
+#
+# This list should eventually be autogenerated (but is currently empty)
+
 # This is duplicating the compile-commands rule because unlike in the use case
 # when a $(RIOTBASE)/compile_commands.json is built, we *want* this to be
 # per-board and per-application. (The large mechanisms are shared anyway).
@@ -64,3 +74,6 @@ $(APPLICATION_RUST_MODULE).module: $(CARGO_LIB) FORCE
 # (should they not exist), and also from re-building everything every time
 # because the .cargo inside is as ephemeral as the build container.
 $(shell mkdir -p ~/.cargo/git ~/.cargo/registry)
+
+FORCE:
+.phony: FORCE

makefiles/vars.inc.mk

@@ -132,3 +132,8 @@ export AFL_FLAGS             # Additional command-line flags passed to afl durin
 # LOG_LEVEL                  # Logging level as integer (NONE: 0, ERROR: 1, WARNING: 2, INFO: 3, DEBUG: 4, default: 3)
 # KCONFIG_ADD_CONFIG         # List of .config files to be merged used by Boards and CPUs. See kconfig.mk
 # VERBOSE_ASSERT             # Set to 1 to print the file and line of a failed assert when assertions blow
+
+export RUST_TARGET           # Rust's own version of the target triple / quadruple.
+                             #
+                             # It is set by the architecture (and thus eventually the CPU), and exported to
+                             # be available when building Rust modules.

sys/Kconfig

@@ -79,6 +79,7 @@ rsource "progress_bar/Kconfig"
 rsource "ps/Kconfig"
 rsource "random/Kconfig"
 rsource "rtc_utils/Kconfig"
+rsource "rust_riotmodules/Kconfig"
 rsource "saul_reg/Kconfig"
 rsource "schedstatistics/Kconfig"
 rsource "sema/Kconfig"

sys/Makefile.dep

@@ -956,4 +956,8 @@ ifneq (,$(filter fido2_ctap,$(USEMODULE)))
   USEMODULE += fido2
 endif
 
+ifneq (,$(filter rust_riotmodules,$(USEMODULE)))
+  include $(RIOTBASE)/sys/rust_riotmodules/Makefile.dep
+endif
+
 include $(RIOTBASE)/sys/test_utils/Makefile.dep

sys/Makefile.include

@@ -159,3 +159,7 @@ endif
 ifneq (,$(filter shell_lock,$(USEMODULE)))
   include $(RIOTBASE)/sys/shell_lock/Makefile.include
 endif
+
+ifneq (,$(filter rust_riotmodules,$(USEMODULE)))
+  include $(RIOTBASE)/sys/rust_riotmodules/Makefile.include
+endif

sys/rust_riotmodules/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "rust_riotmodules"
+version = "0.1.0"
+authors = ["Christian Amsüss <chrysn@fsfe.org>"]
+edition = "2021"
+publish = false
+
+
+[dependencies]
+# The list contains all modules available in RIOT, and should eventually be
+# autogenerated (or at least automatically checked for consistency).

sys/rust_riotmodules/Kconfig

@@ -0,0 +1,23 @@
+# Copyright (c) 2022 HAW Hamburg
+#
+# This file is subject to the terms and conditions of the GNU Lesser
+# General Public License v2.1. See the file LICENSE in the top level
+# directory for more details.
+#
+
+menuconfig MODULE_RUST_RIOTMODULES
+    bool "RUST RIOT modules"
+    depends on TEST_KCONFIG
+    depends on HAS_RUST_TARGET
+    help
+        This module is used when some module asks to have its code built
+        through rust_riotmodules.
+
+config MODULE_RUST_RIOTMODULES_STANDALONE
+    bool "RUST RIOT modules are standalone"
+    default y
+    depends on MODULE_RUST_RIOTMODULES
+    help
+        This module is used when rust_riotmodules is selected, and the main
+        application does not already contain Rust code through which the
+        rust_riotmodules are built.

sys/rust_riotmodules/Makefile.dep

@@ -0,0 +1,10 @@
+# No check for the presence of any of any dependencies (were there none, this
+# wouldn't have been pulled in), but only pull in building this in if the
+# application does not already provide a crate -- in which case the
+# CARGO_OPTIONS added depending on the pseudomodules are enabled in the regular
+# cargo-targets.
+ifeq (,${APPLICATION_RUST_MODULE})
+  USEMODULE += rust_riotmodules_standalone
+endif
+
+FEATURES_REQUIRED += rust_target

sys/rust_riotmodules/Makefile.include

@@ -0,0 +1,6 @@
+## This module is used when some module asking to have its code built
+# through rust_riotmodules. Whether that happens through actually enabling the
+# rust_riotmodules_standalone module or by the application's crate was decided
+# in ./Makefile.dep depending on whether a Rust application module is present
+# or not.
+PSEUDOMODULES += rust_riotmodules

sys/rust_riotmodules/src/lib.rs

@@ -0,0 +1,7 @@
+#![no_std]
+
+// As we're pulling all crates in only for their side effects of having symbols (be that to place
+// them in XFA symbols or to make them available for C) all these crates have to be extern-crate'd
+// to be pulled in because they are not used on the laguage level.
+
+// This list should be as auto-generated / -maintained as the one in Cargo.toml

sys/rust_riotmodules_standalone/Cargo.toml

@@ -0,0 +1,21 @@
+[package]
+name = "rust_riotmodules_standalone"
+version = "0.1.0"
+authors = ["Christian Amsüss <chrysn@fsfe.org>"]
+edition = "2021"
+publish = false
+
+[lib]
+crate-type = [ "staticlib" ]
+
+[profile.release]
+lto = true
+opt-level = "s"
+debug = true
+panic = "abort"
+codegen-units = 1
+
+[dependencies]
+riot-wrappers = { version = "0.7", default-features = false, features = [ "set_panic_handler" ] }
+
+rust_riotmodules = { path = "../rust_riotmodules" }

sys/rust_riotmodules_standalone/Makefile

@@ -0,0 +1,12 @@
+include $(RIOTBASE)/Makefile.base
+
+include $(RIOTMAKE)/cargo-settings.inc.mk
+
+APPLICATION_RUST_MODULE = rust_riotmodules_standalone
+
+# No need to set the Cargo features enabled through the general pseudomodules:
+# They're added to the crate in cargo-targets.inc.mk no matter whether it's
+# building the rust_riotmodules_standalone top level crate or an application
+# crate.
+
+include $(RIOTMAKE)/cargo-targets.inc.mk

sys/rust_riotmodules_standalone/src/lib.rs

@@ -0,0 +1,9 @@
+#![no_std]
+
+// As we're pulling all crates in only for their side effects of having symbols (they are required
+// on the Rust side like riot_wrappers' panic_handler, and rust_riotmodules does that on its own
+// too) all these crates have to be extern-crate'd to be pulled in because they are not used on the
+// language level.
+
+extern crate riot_wrappers;
+extern crate rust_riotmodules;