add rust-analyzer make target

This target creates ${objtree}/rust-project.json which can be read by
rust-analyzer to help with autocompletion for the kernel crate.

The raw bindings do not work yet, as rust-analyzer seems to have a
problem with the include macro.

Signed-off-by: Finn Behrens <me@kloenk.de>

Documentation/rust/quick-start.rst

@@ -155,11 +155,8 @@ definition, and other features.
 ``rust-analyzer`` will need to be
 `configured <https://rust-analyzer.github.io/manual.html#non-cargo-based-projects>`_
 to work with the kernel by adding a ``rust-project.json`` file in the root folder.
-The example ``Documentation/rust/rust-project.json`` can
-be used after updating ``sysroot_src`` and including the relevant modules.
-The path to ``sysroot_src`` is given by::
-
-    $(rustc --print sysroot)/lib/rustlib/src/rust/library
+A ``rust-project.json`` can be generated by building the Make target ``rust-analyzer``,
+which will create a ``rust-project.json`` in the root of the output directory.
 
 
 Configuration

Makefile

@@ -1738,6 +1738,8 @@ help:
 	@echo  '		    is formatted, printing a diff otherwise.'
 	@echo  '  rustdoc	  - Generate Rust documentation'
 	@echo  '		    (requires kernel .config)'
+	@echo  '  rust-analyzer	  - Generate rust-project.json rust-analyzer support file'
+	@echo  '		    (requires kernel .config)'
 	@echo  ''
 	@$(if $(dtstree), \
 		echo 'Devicetree:'; \
@@ -1830,6 +1832,10 @@ rustfmt:
 rustfmtcheck:
 	find -name '*.rs' | xargs $(RUSTFMT) --check
 
+# IDE support targets
+PHONY += rust-analyzer
+rust-analyzer: prepare0
+	$(Q)$(MAKE) $(build)=rust $@
 
 # Misc
 # ---------------------------------------------------------------------------

rust/Makefile

@@ -150,3 +150,6 @@ $(objtree)/rust/kernel.o: private rustc_target_flags = --extern alloc \
 $(objtree)/rust/kernel.o: $(srctree)/rust/kernel/lib.rs $(objtree)/rust/alloc.o \
     $(objtree)/rust/libmodule.so $(objtree)/rust/bindings_generated.rs FORCE
 	$(call if_changed_dep,rustc_library)
+
+rust-analyzer:
+	$(Q)$(srctree)/scripts/generate_rust_analyzer.sh $(srctree) $(objtree) $(RUST_LIB_SRC) $(abspath $(objtree)/rust/bindings_generated.rs) > $(objtree)/rust-project.json

scripts/generate_rust_analyzer.sh

@@ -0,0 +1,97 @@
+#!/usr/bin/env bash
+
+srctree=$1
+objtree=$2
+lib_src=$3
+bindgen_file=$4
+
+
+# TODO: create issue at RA to accept @arg file
+function generate_cfgs() {
+    echo '['
+    cfgs=$(cat $objtree/include/generated/rustc_cfg | sed 's/--cfg=//' | sed 's/"/\\"/g' | sed 's/$/",/' | sed 's/^/"/')
+    echo ${cfgs::-1}
+    echo ']'
+}
+
+function generate_crate() {
+    name=$1
+    module=$2
+    member=${3:-"true"}
+    cfg=${4:-$(generate_cfgs)}
+    deps=${5:-'[{"crate":0,"name":"core"},{"crate":2,"name":"alloc"},{"crate":4,"name":"kernel"}]'}
+    extra=${CRATE_EXTRA:-""}
+
+    echo "{
+        \"display_name\":\"$name\",
+        \"root_module\":\"$module\",
+        \"edition\":\"2018\",
+        \"deps\":$deps,
+        \"is_workspace_member\": $member,
+        \"cfg\": $cfg,
+        \"env\": {
+            \"RUST_BINDINGS_FILE\": \"$bindgen_file\",
+            \"RUST_MODFILE\": \"This is only for rust-analyzer\"
+        }
+        $extra
+    }"
+}
+
+function generate_kernel() {
+    generate_crate "core" "${lib_src}/core/src/lib.rs" "false" "[]" "[]"
+    echo ","
+    generate_crate "compiler_builtins" "${srctree}/rust/compiler_builtins.rs" "true" "[]" "[]"
+    echo ","
+    generate_crate "alloc" "${lib_src}/alloc/src/lib.rs" "false" "[]" \
+        '[{"crate":0,"name":"core"},{"crate":1,"name":"compiler_builtins"}]'
+    echo ","
+    echo '{
+        "display_name":"module",
+        "root_module":"'${srctree}'/rust/module.rs",
+        "edition":"2018",
+        "is_workspace_member":true,
+        "deps": [],
+        "proc_macro_dylib_path": "rust/libmodule.so",
+        "cfg": []
+    },'
+    generate_crate "kernel" "${srctree}/rust/kernel/lib.rs" "true" "$(generate_cfgs)" \
+        '[{"crate":0,"name":"core"},{"crate":2,"name":"alloc"},{"crate":3,"name":"module"}]'
+    echo ","
+}
+
+function check_and_generate() {
+    filepath=$1
+    file=$(basename $filepath)
+    makefile=$(dirname $filepath)/Makefile
+    name=${file%.rs}
+    objname=${name}.o
+    echo "checking $filepath" >&2
+    if grep -q $objname $makefile; then
+        echo "building crate $name" >&2
+        echo $(generate_crate "$name" "$filepath")
+        echo ","
+    fi
+}
+
+function generate_drivers() {
+    drivers=$(find "$srctree/drivers" -name '*.rs')
+    for x in $drivers; do
+        check_and_generate $x
+    done
+    echo ""
+}
+
+function generate_samples() {
+    samples=$(find "$srctree/samples/rust" -name '*.rs')
+    for x in $samples; do
+        check_and_generate $x
+    done
+}
+
+echo '{"crates":['
+generate_kernel
+generate_drivers
+samples=$(generate_samples)
+echo ${samples::-1}
+echo '],
+"sysroot_src": "'${lib_src}'"}'