rust: use custom FFI integer types

Currently FFI integer types are defined in libcore. This commit creates
the `ffi` crate and asks bindgen to use that crate for FFI integer types
instead of `core::ffi`.

This commit is preparatory and no type changes are made in this commit
yet.

Signed-off-by: Gary Guo <gary@garyguo.net>
Link: https://lore.kernel.org/r/20240913213041.395655-4-gary@garyguo.net
[ Added `rustdoc`, `rusttest` and KUnit tests support. Rebased on top of
  `rust-next` (e.g. migrated more `core::ffi` cases). Reworded crate
  docs slightly and formatted. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 26 insertions, 13 deletions

diff --git a/rust/Makefile b/rust/Makefile
index fcec0e1d9762..f349e7b067ea 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -3,7 +3,7 @@
 # Where to place rustdoc generated documentation
 rustdoc_output := $(objtree)/Documentation/output/rust/rustdoc
 
-obj-$(CONFIG_RUST) += core.o compiler_builtins.o
+obj-$(CONFIG_RUST) += core.o compiler_builtins.o ffi.o
 always-$(CONFIG_RUST) += exports_core_generated.h
 
 # Missing prototypes are expected in the helpers since these are exported
@@ -103,10 +103,13 @@ rustdoc-core: $(RUST_LIB_SRC)/core/src/lib.rs FORCE
 rustdoc-compiler_builtins: $(src)/compiler_builtins.rs rustdoc-core FORCE
 	+$(call if_changed,rustdoc)
 
-rustdoc-kernel: private rustc_target_flags = \
+rustdoc-ffi: $(src)/ffi.rs rustdoc-core FORCE
+	+$(call if_changed,rustdoc)
+
+rustdoc-kernel: private rustc_target_flags = --extern ffi \
     --extern build_error --extern macros=$(objtree)/$(obj)/libmacros.so \
     --extern bindings --extern uapi
-rustdoc-kernel: $(src)/kernel/lib.rs rustdoc-core rustdoc-macros \
+rustdoc-kernel: $(src)/kernel/lib.rs rustdoc-core rustdoc-ffi rustdoc-macros \
     rustdoc-compiler_builtins $(obj)/libmacros.so \
     $(obj)/bindings.o FORCE
 	+$(call if_changed,rustdoc)
@@ -124,12 +127,15 @@ quiet_cmd_rustc_test_library = RUSTC TL $<
 rusttestlib-build_error: $(src)/build_error.rs FORCE
 	+$(call if_changed,rustc_test_library)
 
+rusttestlib-ffi: $(src)/ffi.rs FORCE
+	+$(call if_changed,rustc_test_library)
+
 rusttestlib-macros: private rustc_target_flags = --extern proc_macro
 rusttestlib-macros: private rustc_test_library_proc = yes
 rusttestlib-macros: $(src)/macros/lib.rs FORCE
 	+$(call if_changed,rustc_test_library)
 
-rusttestlib-kernel: private rustc_target_flags = \
+rusttestlib-kernel: private rustc_target_flags = --extern ffi \
     --extern build_error --extern macros \
     --extern bindings --extern uapi
 rusttestlib-kernel: $(src)/kernel/lib.rs \
@@ -137,10 +143,12 @@ rusttestlib-kernel: $(src)/kernel/lib.rs \
     $(obj)/libmacros.so $(obj)/bindings.o FORCE
 	+$(call if_changed,rustc_test_library)
 
-rusttestlib-bindings: $(src)/bindings/lib.rs FORCE
+rusttestlib-bindings: private rustc_target_flags = --extern ffi
+rusttestlib-bindings: $(src)/bindings/lib.rs rusttestlib-ffi FORCE
 	+$(call if_changed,rustc_test_library)
 
-rusttestlib-uapi: $(src)/uapi/lib.rs FORCE
+rusttestlib-uapi: private rustc_target_flags = --extern ffi
+rusttestlib-uapi: $(src)/uapi/lib.rs rusttestlib-ffi FORCE
 	+$(call if_changed,rustc_test_library)
 
 quiet_cmd_rustdoc_test = RUSTDOC T $<
@@ -160,7 +168,7 @@ quiet_cmd_rustdoc_test_kernel = RUSTDOC TK $<
 	mkdir -p $(objtree)/$(obj)/test/doctests/kernel; \
 	OBJTREE=$(abspath $(objtree)) \
 	$(RUSTDOC) --test $(rust_flags) \
-		-L$(objtree)/$(obj) --extern kernel \
+		-L$(objtree)/$(obj) --extern ffi --extern kernel \
 		--extern build_error --extern macros \
 		--extern bindings --extern uapi \
 		--no-run --crate-name kernel -Zunstable-options \
@@ -198,9 +206,9 @@ rusttest-macros: $(src)/macros/lib.rs \
 	+$(call if_changed,rustc_test)
 	+$(call if_changed,rustdoc_test)
 
-rusttest-kernel: private rustc_target_flags = \
+rusttest-kernel: private rustc_target_flags = --extern ffi \
     --extern build_error --extern macros --extern bindings --extern uapi
-rusttest-kernel: $(src)/kernel/lib.rs rusttestlib-kernel \
+rusttest-kernel: $(src)/kernel/lib.rs rusttestlib-ffi rusttestlib-kernel \
     rusttestlib-build_error rusttestlib-macros rusttestlib-bindings \
     rusttestlib-uapi FORCE
 	+$(call if_changed,rustc_test)
@@ -273,7 +281,7 @@ bindgen_c_flags_final = $(bindgen_c_flags_lto) -fno-builtin -D__BINDGEN__
 quiet_cmd_bindgen = BINDGEN $@
       cmd_bindgen = \
 	$(BINDGEN) $< $(bindgen_target_flags) \
-		--use-core --with-derive-default --ctypes-prefix core::ffi --no-layout-tests \
+		--use-core --with-derive-default --ctypes-prefix ffi --no-layout-tests \
 		--no-debug '.*' --enable-function-attribute-detection \
 		-o $@ -- $(bindgen_c_flags_final) -DMODULE \
 		$(bindgen_target_cflags) $(bindgen_target_extra)
@@ -401,18 +409,23 @@ $(obj)/compiler_builtins.o: $(src)/compiler_builtins.rs $(obj)/core.o FORCE
 $(obj)/build_error.o: $(src)/build_error.rs $(obj)/compiler_builtins.o FORCE
 	+$(call if_changed_rule,rustc_library)
 
+$(obj)/ffi.o: $(src)/ffi.rs $(obj)/compiler_builtins.o FORCE
+	+$(call if_changed_rule,rustc_library)
+
+$(obj)/bindings.o: private rustc_target_flags = --extern ffi
 $(obj)/bindings.o: $(src)/bindings/lib.rs \
-    $(obj)/compiler_builtins.o \
+    $(obj)/ffi.o \
     $(obj)/bindings/bindings_generated.rs \
     $(obj)/bindings/bindings_helpers_generated.rs FORCE
 	+$(call if_changed_rule,rustc_library)
 
+$(obj)/uapi.o: private rustc_target_flags = --extern ffi
 $(obj)/uapi.o: $(src)/uapi/lib.rs \
-    $(obj)/compiler_builtins.o \
+    $(obj)/ffi.o \
     $(obj)/uapi/uapi_generated.rs FORCE
 	+$(call if_changed_rule,rustc_library)
 
-$(obj)/kernel.o: private rustc_target_flags = \
+$(obj)/kernel.o: private rustc_target_flags = --extern ffi \
     --extern build_error --extern macros --extern bindings --extern uapi
 $(obj)/kernel.o: $(src)/kernel/lib.rs $(obj)/build_error.o \
     $(obj)/libmacros.so $(obj)/bindings.o $(obj)/uapi.o FORCE