xref: /linux/rust/Makefile (revision d072acda4862f095ec9056979b654cc06a22cc68)
1# SPDX-License-Identifier: GPL-2.0
2
3# Where to place rustdoc generated documentation
4rustdoc_output := $(objtree)/Documentation/output/rust/rustdoc
5
6obj-$(CONFIG_RUST) += core.o compiler_builtins.o ffi.o
7always-$(CONFIG_RUST) += exports_core_generated.h
8
9# Missing prototypes are expected in the helpers since these are exported
10# for Rust only, thus there is no header nor prototypes.
11obj-$(CONFIG_RUST) += helpers/helpers.o
12CFLAGS_REMOVE_helpers/helpers.o = -Wmissing-prototypes -Wmissing-declarations
13
14always-$(CONFIG_RUST) += libmacros.so
15no-clean-files += libmacros.so
16
17always-$(CONFIG_RUST) += bindings/bindings_generated.rs bindings/bindings_helpers_generated.rs
18obj-$(CONFIG_RUST) += bindings.o kernel.o
19always-$(CONFIG_RUST) += exports_helpers_generated.h \
20    exports_bindings_generated.h exports_kernel_generated.h
21
22always-$(CONFIG_RUST) += uapi/uapi_generated.rs
23obj-$(CONFIG_RUST) += uapi.o
24
25ifdef CONFIG_RUST_BUILD_ASSERT_ALLOW
26obj-$(CONFIG_RUST) += build_error.o
27else
28always-$(CONFIG_RUST) += build_error.o
29endif
30
31obj-$(CONFIG_RUST) += exports.o
32
33always-$(CONFIG_RUST_KERNEL_DOCTESTS) += doctests_kernel_generated.rs
34always-$(CONFIG_RUST_KERNEL_DOCTESTS) += doctests_kernel_generated_kunit.c
35
36obj-$(CONFIG_RUST_KERNEL_DOCTESTS) += doctests_kernel_generated.o
37obj-$(CONFIG_RUST_KERNEL_DOCTESTS) += doctests_kernel_generated_kunit.o
38
39# Avoids running `$(RUSTC)` for the sysroot when it may not be available.
40ifdef CONFIG_RUST
41
42# `$(rust_flags)` is passed in case the user added `--sysroot`.
43rustc_sysroot := $(shell MAKEFLAGS= $(RUSTC) $(rust_flags) --print sysroot)
44rustc_host_target := $(shell $(RUSTC) --version --verbose | grep -F 'host: ' | cut -d' ' -f2)
45RUST_LIB_SRC ?= $(rustc_sysroot)/lib/rustlib/src/rust/library
46
47ifneq ($(quiet),)
48rust_test_quiet=-q
49rustdoc_test_quiet=--test-args -q
50rustdoc_test_kernel_quiet=>/dev/null
51endif
52
53core-cfgs = \
54    --cfg no_fp_fmt_parse
55
56quiet_cmd_rustdoc = RUSTDOC $(if $(rustdoc_host),H, ) $<
57      cmd_rustdoc = \
58	OBJTREE=$(abspath $(objtree)) \
59	$(RUSTDOC) $(filter-out $(skip_flags),$(if $(rustdoc_host),$(rust_common_flags),$(rust_flags))) \
60		$(rustc_target_flags) -L$(objtree)/$(obj) \
61		-Zunstable-options --generate-link-to-definition \
62		--output $(rustdoc_output) \
63		--crate-name $(subst rustdoc-,,$@) \
64		$(if $(rustdoc_host),,--sysroot=/dev/null) \
65		@$(objtree)/include/generated/rustc_cfg $<
66
67# The `html_logo_url` and `html_favicon_url` forms of the `doc` attribute
68# can be used to specify a custom logo. However:
69#   - The given value is used as-is, thus it cannot be relative or a local file
70#     (unlike the non-custom case) since the generated docs have subfolders.
71#   - It requires adding it to every crate.
72#   - It requires changing `core` which comes from the sysroot.
73#
74# Using `-Zcrate-attr` would solve the last two points, but not the first.
75# The https://github.com/rust-lang/rfcs/pull/3226 RFC suggests two new
76# command-like flags to solve the issue. Meanwhile, we use the non-custom case
77# and then retouch the generated files.
78rustdoc: rustdoc-core rustdoc-macros rustdoc-compiler_builtins \
79    rustdoc-kernel
80	$(Q)cp $(srctree)/Documentation/images/logo.svg $(rustdoc_output)/static.files/
81	$(Q)cp $(srctree)/Documentation/images/COPYING-logo $(rustdoc_output)/static.files/
82	$(Q)find $(rustdoc_output) -name '*.html' -type f -print0 | xargs -0 sed -Ei \
83		-e 's:rust-logo-[0-9a-f]+\.svg:logo.svg:g' \
84		-e 's:favicon-[0-9a-f]+\.svg:logo.svg:g' \
85		-e 's:<link rel="alternate icon" type="image/png" href="[/.]+/static\.files/favicon-(16x16|32x32)-[0-9a-f]+\.png">::g' \
86		-e 's:<a href="srctree/([^"]+)">:<a href="$(realpath $(srctree))/\1">:g'
87	$(Q)for f in $(rustdoc_output)/static.files/rustdoc-*.css; do \
88		echo ".logo-container > img { object-fit: contain; }" >> $$f; done
89
90rustdoc-macros: private rustdoc_host = yes
91rustdoc-macros: private rustc_target_flags = --crate-type proc-macro \
92    --extern proc_macro
93rustdoc-macros: $(src)/macros/lib.rs FORCE
94	+$(call if_changed,rustdoc)
95
96# Starting with Rust 1.82.0, skipping `-Wrustdoc::unescaped_backticks` should
97# not be needed -- see https://github.com/rust-lang/rust/pull/128307.
98rustdoc-core: private skip_flags = -Wrustdoc::unescaped_backticks
99rustdoc-core: private rustc_target_flags = $(core-cfgs)
100rustdoc-core: $(RUST_LIB_SRC)/core/src/lib.rs FORCE
101	+$(call if_changed,rustdoc)
102
103rustdoc-compiler_builtins: $(src)/compiler_builtins.rs rustdoc-core FORCE
104	+$(call if_changed,rustdoc)
105
106rustdoc-ffi: $(src)/ffi.rs rustdoc-core FORCE
107	+$(call if_changed,rustdoc)
108
109rustdoc-kernel: private rustc_target_flags = --extern ffi \
110    --extern build_error --extern macros=$(objtree)/$(obj)/libmacros.so \
111    --extern bindings --extern uapi
112rustdoc-kernel: $(src)/kernel/lib.rs rustdoc-core rustdoc-ffi rustdoc-macros \
113    rustdoc-compiler_builtins $(obj)/libmacros.so \
114    $(obj)/bindings.o FORCE
115	+$(call if_changed,rustdoc)
116
117quiet_cmd_rustc_test_library = RUSTC TL $<
118      cmd_rustc_test_library = \
119	OBJTREE=$(abspath $(objtree)) \
120	$(RUSTC) $(rust_common_flags) \
121		@$(objtree)/include/generated/rustc_cfg $(rustc_target_flags) \
122		--crate-type $(if $(rustc_test_library_proc),proc-macro,rlib) \
123		--out-dir $(objtree)/$(obj)/test --cfg testlib \
124		-L$(objtree)/$(obj)/test \
125		--crate-name $(subst rusttest-,,$(subst rusttestlib-,,$@)) $<
126
127rusttestlib-build_error: $(src)/build_error.rs FORCE
128	+$(call if_changed,rustc_test_library)
129
130rusttestlib-ffi: $(src)/ffi.rs FORCE
131	+$(call if_changed,rustc_test_library)
132
133rusttestlib-macros: private rustc_target_flags = --extern proc_macro
134rusttestlib-macros: private rustc_test_library_proc = yes
135rusttestlib-macros: $(src)/macros/lib.rs FORCE
136	+$(call if_changed,rustc_test_library)
137
138rusttestlib-kernel: private rustc_target_flags = --extern ffi \
139    --extern build_error --extern macros \
140    --extern bindings --extern uapi
141rusttestlib-kernel: $(src)/kernel/lib.rs \
142    rusttestlib-bindings rusttestlib-uapi rusttestlib-build_error \
143    $(obj)/libmacros.so $(obj)/bindings.o FORCE
144	+$(call if_changed,rustc_test_library)
145
146rusttestlib-bindings: private rustc_target_flags = --extern ffi
147rusttestlib-bindings: $(src)/bindings/lib.rs rusttestlib-ffi FORCE
148	+$(call if_changed,rustc_test_library)
149
150rusttestlib-uapi: private rustc_target_flags = --extern ffi
151rusttestlib-uapi: $(src)/uapi/lib.rs rusttestlib-ffi FORCE
152	+$(call if_changed,rustc_test_library)
153
154quiet_cmd_rustdoc_test = RUSTDOC T $<
155      cmd_rustdoc_test = \
156	RUST_MODFILE=test.rs \
157	OBJTREE=$(abspath $(objtree)) \
158	$(RUSTDOC) --test $(rust_common_flags) \
159		@$(objtree)/include/generated/rustc_cfg \
160		$(rustc_target_flags) $(rustdoc_test_target_flags) \
161		$(rustdoc_test_quiet) \
162		-L$(objtree)/$(obj)/test --output $(rustdoc_output) \
163		--crate-name $(subst rusttest-,,$@) $<
164
165quiet_cmd_rustdoc_test_kernel = RUSTDOC TK $<
166      cmd_rustdoc_test_kernel = \
167	rm -rf $(objtree)/$(obj)/test/doctests/kernel; \
168	mkdir -p $(objtree)/$(obj)/test/doctests/kernel; \
169	OBJTREE=$(abspath $(objtree)) \
170	$(RUSTDOC) --test $(rust_flags) \
171		-L$(objtree)/$(obj) --extern ffi --extern kernel \
172		--extern build_error --extern macros \
173		--extern bindings --extern uapi \
174		--no-run --crate-name kernel -Zunstable-options \
175		--sysroot=/dev/null \
176		--test-builder $(objtree)/scripts/rustdoc_test_builder \
177		$< $(rustdoc_test_kernel_quiet); \
178	$(objtree)/scripts/rustdoc_test_gen
179
180%/doctests_kernel_generated.rs %/doctests_kernel_generated_kunit.c: \
181    $(src)/kernel/lib.rs $(obj)/kernel.o \
182    $(objtree)/scripts/rustdoc_test_builder \
183    $(objtree)/scripts/rustdoc_test_gen FORCE
184	+$(call if_changed,rustdoc_test_kernel)
185
186# We cannot use `-Zpanic-abort-tests` because some tests are dynamic,
187# so for the moment we skip `-Cpanic=abort`.
188quiet_cmd_rustc_test = RUSTC T  $<
189      cmd_rustc_test = \
190	OBJTREE=$(abspath $(objtree)) \
191	$(RUSTC) --test $(rust_common_flags) \
192		@$(objtree)/include/generated/rustc_cfg \
193		$(rustc_target_flags) --out-dir $(objtree)/$(obj)/test \
194		-L$(objtree)/$(obj)/test \
195		--crate-name $(subst rusttest-,,$@) $<; \
196	$(objtree)/$(obj)/test/$(subst rusttest-,,$@) $(rust_test_quiet) \
197		$(rustc_test_run_flags)
198
199rusttest: rusttest-macros rusttest-kernel
200
201rusttest-macros: private rustc_target_flags = --extern proc_macro \
202	--extern macros --extern kernel
203rusttest-macros: private rustdoc_test_target_flags = --crate-type proc-macro
204rusttest-macros: $(src)/macros/lib.rs \
205    rusttestlib-macros rusttestlib-kernel FORCE
206	+$(call if_changed,rustc_test)
207	+$(call if_changed,rustdoc_test)
208
209rusttest-kernel: private rustc_target_flags = --extern ffi \
210    --extern build_error --extern macros --extern bindings --extern uapi
211rusttest-kernel: $(src)/kernel/lib.rs rusttestlib-ffi rusttestlib-kernel \
212    rusttestlib-build_error rusttestlib-macros rusttestlib-bindings \
213    rusttestlib-uapi FORCE
214	+$(call if_changed,rustc_test)
215
216ifdef CONFIG_CC_IS_CLANG
217bindgen_c_flags = $(c_flags)
218else
219# bindgen relies on libclang to parse C. Ideally, bindgen would support a GCC
220# plugin backend and/or the Clang driver would be perfectly compatible with GCC.
221#
222# For the moment, here we are tweaking the flags on the fly. This is a hack,
223# and some kernel configurations may not work (e.g. `GCC_PLUGIN_RANDSTRUCT`
224# if we end up using one of those structs).
225bindgen_skip_c_flags := -mno-fp-ret-in-387 -mpreferred-stack-boundary=% \
226	-mskip-rax-setup -mgeneral-regs-only -msign-return-address=% \
227	-mindirect-branch=thunk-extern -mindirect-branch-register \
228	-mfunction-return=thunk-extern -mrecord-mcount -mabi=lp64 \
229	-mindirect-branch-cs-prefix -mstack-protector-guard% -mtraceback=no \
230	-mno-pointers-to-nested-functions -mno-string \
231	-mno-strict-align -mstrict-align \
232	-fconserve-stack -falign-jumps=% -falign-loops=% \
233	-femit-struct-debug-baseonly -fno-ipa-cp-clone -fno-ipa-sra \
234	-fno-partial-inlining -fplugin-arg-arm_ssp_per_task_plugin-% \
235	-fno-reorder-blocks -fno-allow-store-data-races -fasan-shadow-offset=% \
236	-fzero-call-used-regs=% -fno-stack-clash-protection \
237	-fno-inline-functions-called-once -fsanitize=bounds-strict \
238	-fstrict-flex-arrays=% -fmin-function-alignment=% \
239	--param=% --param asan-%
240
241# Derived from `scripts/Makefile.clang`.
242BINDGEN_TARGET_x86	:= x86_64-linux-gnu
243BINDGEN_TARGET_arm64	:= aarch64-linux-gnu
244BINDGEN_TARGET		:= $(BINDGEN_TARGET_$(SRCARCH))
245
246# All warnings are inhibited since GCC builds are very experimental,
247# many GCC warnings are not supported by Clang, they may only appear in
248# some configurations, with new GCC versions, etc.
249bindgen_extra_c_flags = -w --target=$(BINDGEN_TARGET)
250
251# Auto variable zero-initialization requires an additional special option with
252# clang that is going to be removed sometime in the future (likely in
253# clang-18), so make sure to pass this option only if clang supports it
254# (libclang major version < 16).
255#
256# https://github.com/llvm/llvm-project/issues/44842
257# https://github.com/llvm/llvm-project/blob/llvmorg-16.0.0-rc2/clang/docs/ReleaseNotes.rst#deprecated-compiler-flags
258ifdef CONFIG_INIT_STACK_ALL_ZERO
259libclang_maj_ver=$(shell $(BINDGEN) $(srctree)/scripts/rust_is_available_bindgen_libclang.h 2>&1 | sed -ne 's/.*clang version \([0-9]*\).*/\1/p')
260ifeq ($(shell expr $(libclang_maj_ver) \< 16), 1)
261bindgen_extra_c_flags += -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
262endif
263endif
264
265bindgen_c_flags = $(filter-out $(bindgen_skip_c_flags), $(c_flags)) \
266	$(bindgen_extra_c_flags)
267endif
268
269ifdef CONFIG_LTO
270bindgen_c_flags_lto = $(filter-out $(CC_FLAGS_LTO), $(bindgen_c_flags))
271else
272bindgen_c_flags_lto = $(bindgen_c_flags)
273endif
274
275# `-fno-builtin` is passed to avoid `bindgen` from using `clang` builtin
276# prototypes for functions like `memcpy` -- if this flag is not passed,
277# `bindgen`-generated prototypes use `c_ulong` or `c_uint` depending on
278# architecture instead of generating `usize`.
279bindgen_c_flags_final = $(bindgen_c_flags_lto) -fno-builtin -D__BINDGEN__
280
281quiet_cmd_bindgen = BINDGEN $@
282      cmd_bindgen = \
283	$(BINDGEN) $< $(bindgen_target_flags) \
284		--use-core --with-derive-default --ctypes-prefix ffi --no-layout-tests \
285		--no-debug '.*' --enable-function-attribute-detection \
286		-o $@ -- $(bindgen_c_flags_final) -DMODULE \
287		$(bindgen_target_cflags) $(bindgen_target_extra)
288
289$(obj)/bindings/bindings_generated.rs: private bindgen_target_flags = \
290    $(shell grep -Ev '^#|^$$' $(src)/bindgen_parameters)
291$(obj)/bindings/bindings_generated.rs: private bindgen_target_extra = ; \
292    sed -Ei 's/pub const RUST_CONST_HELPER_([a-zA-Z0-9_]*)/pub const \1/g' $@
293$(obj)/bindings/bindings_generated.rs: $(src)/bindings/bindings_helper.h \
294    $(src)/bindgen_parameters FORCE
295	$(call if_changed_dep,bindgen)
296
297$(obj)/uapi/uapi_generated.rs: private bindgen_target_flags = \
298    $(shell grep -Ev '^#|^$$' $(src)/bindgen_parameters)
299$(obj)/uapi/uapi_generated.rs: $(src)/uapi/uapi_helper.h \
300    $(src)/bindgen_parameters FORCE
301	$(call if_changed_dep,bindgen)
302
303# See `CFLAGS_REMOVE_helpers.o` above. In addition, Clang on C does not warn
304# with `-Wmissing-declarations` (unlike GCC), so it is not strictly needed here
305# given it is `libclang`; but for consistency, future Clang changes and/or
306# a potential future GCC backend for `bindgen`, we disable it too.
307$(obj)/bindings/bindings_helpers_generated.rs: private bindgen_target_flags = \
308    --blocklist-type '.*' --allowlist-var '' \
309    --allowlist-function 'rust_helper_.*'
310$(obj)/bindings/bindings_helpers_generated.rs: private bindgen_target_cflags = \
311    -I$(objtree)/$(obj) -Wno-missing-prototypes -Wno-missing-declarations
312$(obj)/bindings/bindings_helpers_generated.rs: private bindgen_target_extra = ; \
313    sed -Ei 's/pub fn rust_helper_([a-zA-Z0-9_]*)/#[link_name="rust_helper_\1"]\n    pub fn \1/g' $@
314$(obj)/bindings/bindings_helpers_generated.rs: $(src)/helpers/helpers.c FORCE
315	$(call if_changed_dep,bindgen)
316
317quiet_cmd_exports = EXPORTS $@
318      cmd_exports = \
319	$(NM) -p --defined-only $< \
320		| awk '$$2~/(T|R|D|B)/ && $$3!~/__cfi/ {printf "EXPORT_SYMBOL_RUST_GPL(%s);\n",$$3}' > $@
321
322$(obj)/exports_core_generated.h: $(obj)/core.o FORCE
323	$(call if_changed,exports)
324
325# Even though Rust kernel modules should never use the bindings directly,
326# symbols from the `bindings` crate and the C helpers need to be exported
327# because Rust generics and inlined functions may not get their code generated
328# in the crate where they are defined. Other helpers, called from non-inline
329# functions, may not be exported, in principle. However, in general, the Rust
330# compiler does not guarantee codegen will be performed for a non-inline
331# function either. Therefore, we export all symbols from helpers and bindings.
332# In the future, this may be revisited to reduce the number of exports after
333# the compiler is informed about the places codegen is required.
334$(obj)/exports_helpers_generated.h: $(obj)/helpers/helpers.o FORCE
335	$(call if_changed,exports)
336
337$(obj)/exports_bindings_generated.h: $(obj)/bindings.o FORCE
338	$(call if_changed,exports)
339
340$(obj)/exports_kernel_generated.h: $(obj)/kernel.o FORCE
341	$(call if_changed,exports)
342
343quiet_cmd_rustc_procmacro = $(RUSTC_OR_CLIPPY_QUIET) P $@
344      cmd_rustc_procmacro = \
345	$(RUSTC_OR_CLIPPY) $(rust_common_flags) \
346		-Clinker-flavor=gcc -Clinker=$(HOSTCC) \
347		-Clink-args='$(call escsq,$(KBUILD_HOSTLDFLAGS))' \
348		--emit=dep-info=$(depfile) --emit=link=$@ --extern proc_macro \
349		--crate-type proc-macro \
350		--crate-name $(patsubst lib%.so,%,$(notdir $@)) $<
351
352# Procedural macros can only be used with the `rustc` that compiled it.
353$(obj)/libmacros.so: $(src)/macros/lib.rs FORCE
354	+$(call if_changed_dep,rustc_procmacro)
355
356quiet_cmd_rustc_library = $(if $(skip_clippy),RUSTC,$(RUSTC_OR_CLIPPY_QUIET)) L $@
357      cmd_rustc_library = \
358	OBJTREE=$(abspath $(objtree)) \
359	$(if $(skip_clippy),$(RUSTC),$(RUSTC_OR_CLIPPY)) \
360		$(filter-out $(skip_flags),$(rust_flags) $(rustc_target_flags)) \
361		--emit=dep-info=$(depfile) --emit=obj=$@ \
362		--emit=metadata=$(dir $@)$(patsubst %.o,lib%.rmeta,$(notdir $@)) \
363		--crate-type rlib -L$(objtree)/$(obj) \
364		--crate-name $(patsubst %.o,%,$(notdir $@)) $< \
365		--sysroot=/dev/null \
366	$(if $(rustc_objcopy),;$(OBJCOPY) $(rustc_objcopy) $@) \
367	$(cmd_objtool)
368
369rust-analyzer:
370	$(Q)$(srctree)/scripts/generate_rust_analyzer.py \
371		--cfgs='core=$(core-cfgs)' \
372		$(realpath $(srctree)) $(realpath $(objtree)) \
373		$(rustc_sysroot) $(RUST_LIB_SRC) $(KBUILD_EXTMOD) > \
374		$(if $(KBUILD_EXTMOD),$(extmod_prefix),$(objtree))/rust-project.json
375
376redirect-intrinsics = \
377	__addsf3 __eqsf2 __extendsfdf2 __gesf2 __lesf2 __ltsf2 __mulsf3 __nesf2 __truncdfsf2 __unordsf2 \
378	__adddf3 __eqdf2 __ledf2 __ltdf2 __muldf3 __unorddf2 \
379	__muloti4 __multi3 \
380	__udivmodti4 __udivti3 __umodti3
381
382ifneq ($(or $(CONFIG_ARM64),$(and $(CONFIG_RISCV),$(CONFIG_64BIT))),)
383	# These intrinsics are defined for ARM64 and RISCV64
384	redirect-intrinsics += \
385		__ashrti3 \
386		__ashlti3 __lshrti3
387endif
388
389define rule_rustc_library
390	$(call cmd_and_fixdep,rustc_library)
391	$(call cmd,gen_objtooldep)
392endef
393
394$(obj)/core.o: private skip_clippy = 1
395$(obj)/core.o: private skip_flags = -Wunreachable_pub
396$(obj)/core.o: private rustc_objcopy = $(foreach sym,$(redirect-intrinsics),--redefine-sym $(sym)=__rust$(sym))
397$(obj)/core.o: private rustc_target_flags = $(core-cfgs)
398$(obj)/core.o: $(RUST_LIB_SRC)/core/src/lib.rs \
399    $(wildcard $(objtree)/include/config/RUSTC_VERSION_TEXT) FORCE
400	+$(call if_changed_rule,rustc_library)
401ifneq ($(or $(CONFIG_X86_64),$(CONFIG_X86_32)),)
402$(obj)/core.o: scripts/target.json
403endif
404
405$(obj)/compiler_builtins.o: private rustc_objcopy = -w -W '__*'
406$(obj)/compiler_builtins.o: $(src)/compiler_builtins.rs $(obj)/core.o FORCE
407	+$(call if_changed_rule,rustc_library)
408
409$(obj)/build_error.o: $(src)/build_error.rs $(obj)/compiler_builtins.o FORCE
410	+$(call if_changed_rule,rustc_library)
411
412$(obj)/ffi.o: $(src)/ffi.rs $(obj)/compiler_builtins.o FORCE
413	+$(call if_changed_rule,rustc_library)
414
415$(obj)/bindings.o: private rustc_target_flags = --extern ffi
416$(obj)/bindings.o: $(src)/bindings/lib.rs \
417    $(obj)/ffi.o \
418    $(obj)/bindings/bindings_generated.rs \
419    $(obj)/bindings/bindings_helpers_generated.rs FORCE
420	+$(call if_changed_rule,rustc_library)
421
422$(obj)/uapi.o: private rustc_target_flags = --extern ffi
423$(obj)/uapi.o: $(src)/uapi/lib.rs \
424    $(obj)/ffi.o \
425    $(obj)/uapi/uapi_generated.rs FORCE
426	+$(call if_changed_rule,rustc_library)
427
428$(obj)/kernel.o: private rustc_target_flags = --extern ffi \
429    --extern build_error --extern macros --extern bindings --extern uapi
430$(obj)/kernel.o: $(src)/kernel/lib.rs $(obj)/build_error.o \
431    $(obj)/libmacros.so $(obj)/bindings.o $(obj)/uapi.o FORCE
432	+$(call if_changed_rule,rustc_library)
433
434endif # CONFIG_RUST
435