[RFC PATCH 1/2] kbuild: rust: register "klint" as a tool

[Gary Guo <gary@kernel.org>]

From: Gary Guo <gary@garyguo.net>

Register "klint" as a tool so that rustc understands that `#[klint::attr]`
is a tool attribute and `klint::lint` is a tool lint.

This makes use of the `register_tool` feature which has been implemented as
a nightly feature for long time and has an active RFC. The feature does not
change any functionality, simply make it possible for Rust to recognize
extra tools in addition to the built-in hardcoded ones (clippy & rustdoc).

Link: https://github.com/rust-lang/rfcs/pull/3808
Signed-off-by: Gary Guo <gary@garyguo.net>
---
 rust/Makefile          | 5 ++++-
 scripts/Makefile.build | 6 ++++--
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/rust/Makefile b/rust/Makefile
index 63464bd2c1e9..db3dd17f780b 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -320,7 +320,9 @@ quiet_cmd_rustdoc_test_kernel = RUSTDOC TK $<
 	mkdir -p $(objtree)/$(obj)/test/doctests/kernel; \
 	OBJTREE=$(abspath $(objtree)) \
 	$(RUSTDOC) --test $(filter-out --remap-path-prefix=%,$(rust_flags)) \
-		-L$(objtree)/$(obj) --extern ffi --extern pin_init \
+		-L$(objtree)/$(obj) \
+		-Zcrate-attr='feature(register_tool)' -Zcrate-attr='register_tool(klint)' \
+		--extern ffi --extern pin_init \
 		--extern kernel --extern build_error --extern macros \
 		--extern bindings --extern uapi \
 		--no-run --crate-name kernel -Zunstable-options \
@@ -562,6 +564,7 @@ quiet_cmd_rustc_library = $(if $(skip_clippy),RUSTC,$(RUSTC_OR_CLIPPY_QUIET)) L
 	$(if $(skip_clippy),$(RUSTC),$(RUSTC_OR_CLIPPY)) \
 		$(filter-out $(skip_flags),$(rust_flags)) $(rustc_target_flags) \
 		--emit=dep-info=$(depfile) --emit=obj=$@ \
+		-Zcrate-attr='feature(register_tool)' -Zcrate-attr='register_tool(klint)' \
 		--emit=metadata=$(dir $@)$(patsubst %.o,lib%.rmeta,$(notdir $@)) \
 		--crate-type rlib -L$(objtree)/$(obj) \
 		--crate-name $(patsubst %.o,%,$(notdir $@)) $< \
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 0c838c467c76..d951d553c82f 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -312,12 +312,13 @@ $(obj)/%.lst: $(obj)/%.c FORCE
 #   - Stable since Rust 1.82.0: `feature(asm_const)`,
 #     `feature(offset_of_nested)`, `feature(raw_ref_op)`.
 #   - Stable since Rust 1.87.0: `feature(asm_goto)`.
-#   - Expected to become stable: `feature(arbitrary_self_types)`.
+#   - Expected to become stable: `feature(arbitrary_self_types)`,
+#     `feature(register_tool)`.
 #   - To be determined: `feature(used_with_arg)`.
 #
 # Please see https://github.com/Rust-for-Linux/linux/issues/2 for details on
 # the unstable features in use.
-rust_allowed_features := asm_const,asm_goto,arbitrary_self_types,lint_reasons,offset_of_nested,raw_ref_op,used_with_arg
+rust_allowed_features := asm_const,asm_goto,arbitrary_self_types,lint_reasons,offset_of_nested,raw_ref_op,register_tool,used_with_arg
 
 # `--out-dir` is required to avoid temporaries being created by `rustc` in the
 # current working directory, which may be not accessible in the out-of-tree
@@ -328,6 +329,7 @@ rust_common_cmd = \
 	-Zallow-features=$(rust_allowed_features) \
 	-Zcrate-attr=no_std \
 	-Zcrate-attr='feature($(rust_allowed_features))' \
+	-Zcrate-attr='register_tool(klint)' \
 	-Zunstable-options --extern pin_init --extern kernel \
 	--crate-type rlib -L $(objtree)/rust/ \
 	--crate-name $(basename $(notdir $@)) \
-- 
2.51.2