[PATCH v2 1/3] rust: Introduce HAVE_GENERATE_RUST_TARGET config option

[Jiaxun Yang <jiaxun.yang@flygoat.com>]

scripts/generate_rust_target.rs is used by several architectures
to generate target.json target spec file.

However the enablement of this feature was controlled by target
specific Makefile pieces spreading everywhere.

Introduce HAVE_GENERATE_RUST_TARGET config option as a centralized
switch to control the per-arch usage of generate_rust_target.rs.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
---
v2:
	- Reword Kconfig help
	- Remove x86 specific condition for UM
---
 Makefile             | 3 +++
 arch/Kconfig         | 8 ++++++++
 arch/um/Kconfig      | 1 +
 arch/x86/Makefile    | 1 -
 arch/x86/Makefile.um | 1 -
 rust/Makefile        | 2 +-
 scripts/Makefile     | 4 +---
 7 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/Makefile b/Makefile
index 2c1db7a6f793..b183855c34ea 100644
--- a/Makefile
+++ b/Makefile
@@ -807,6 +807,9 @@ KBUILD_CFLAGS += -Os
 KBUILD_RUSTFLAGS += -Copt-level=s
 endif
 
+ifdef CONFIG_HAVE_GENERATE_RUST_TARGET
+KBUILD_RUSTFLAGS += --target=$(objtree)/scripts/target.json
+endif
 # Always set `debug-assertions` and `overflow-checks` because their default
 # depends on `opt-level` and `debug-assertions`, respectively.
 KBUILD_RUSTFLAGS += -Cdebug-assertions=$(if $(CONFIG_RUST_DEBUG_ASSERTIONS),y,n)
diff --git a/arch/Kconfig b/arch/Kconfig
index 4e2eaba9e305..0865ff4796e7 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -377,6 +377,14 @@ config HAVE_RUST
 	  This symbol should be selected by an architecture if it
 	  supports Rust.
 
+config HAVE_GENERATE_RUST_TARGET
+	bool
+	depends on HAVE_RUST
+	help
+	  This symbol should be selected by an architecture if it
+	  needs generating Rust target.json file with
+	  scripts/generate_rust_target.rs.
+
 config HAVE_FUNCTION_ARG_ACCESS_API
 	bool
 	help
diff --git a/arch/um/Kconfig b/arch/um/Kconfig
index dca84fd6d00a..6b1c8ae2422d 100644
--- a/arch/um/Kconfig
+++ b/arch/um/Kconfig
@@ -32,6 +32,7 @@ config UML
 	select TTY # Needed for line.c
 	select HAVE_ARCH_VMAP_STACK
 	select HAVE_RUST
+	select HAVE_GENERATE_RUST_TARGET
 	select ARCH_HAS_UBSAN
 
 config MMU
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index a1883a30a5d8..cbd707f88a63 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -75,7 +75,6 @@ export BITS
 #    https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53383
 #
 KBUILD_CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx
-KBUILD_RUSTFLAGS += --target=$(objtree)/scripts/target.json
 KBUILD_RUSTFLAGS += -Ctarget-feature=-sse,-sse2,-sse3,-ssse3,-sse4.1,-sse4.2,-avx,-avx2
 
 #
diff --git a/arch/x86/Makefile.um b/arch/x86/Makefile.um
index a46b1397ad01..2106a2bd152b 100644
--- a/arch/x86/Makefile.um
+++ b/arch/x86/Makefile.um
@@ -9,7 +9,6 @@ core-y += arch/x86/crypto/
 #
 ifeq ($(CONFIG_CC_IS_CLANG),y)
 KBUILD_CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx
-KBUILD_RUSTFLAGS += --target=$(objtree)/scripts/target.json
 KBUILD_RUSTFLAGS += -Ctarget-feature=-sse,-sse2,-sse3,-ssse3,-sse4.1,-sse4.2,-avx,-avx2
 endif
 
diff --git a/rust/Makefile b/rust/Makefile
index 99204e33f1dd..fe3640b98011 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -378,7 +378,7 @@ $(obj)/core.o: private rustc_objcopy = $(foreach sym,$(redirect-intrinsics),--re
 $(obj)/core.o: private rustc_target_flags = $(core-cfgs)
 $(obj)/core.o: $(RUST_LIB_SRC)/core/src/lib.rs FORCE
 	+$(call if_changed_rule,rustc_library)
-ifneq ($(or $(CONFIG_X86_64),$(CONFIG_X86_32)),)
+ifdef CONFIG_HAVE_GENERATE_RUST_TARGET
 $(obj)/core.o: scripts/target.json
 endif
 
diff --git a/scripts/Makefile b/scripts/Makefile
index dccef663ca82..33258a856a1a 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -12,13 +12,11 @@ hostprogs-always-$(CONFIG_SYSTEM_EXTRA_CERTIFICATE)	+= insert-sys-cert
 hostprogs-always-$(CONFIG_RUST_KERNEL_DOCTESTS)		+= rustdoc_test_builder
 hostprogs-always-$(CONFIG_RUST_KERNEL_DOCTESTS)		+= rustdoc_test_gen
 
-ifneq ($(or $(CONFIG_X86_64),$(CONFIG_X86_32)),)
-always-$(CONFIG_RUST)					+= target.json
+always-$(CONFIG_HAVE_GENERATE_RUST_TARGET)		+= target.json
 filechk_rust_target = $< < include/config/auto.conf
 
 $(obj)/target.json: scripts/generate_rust_target include/config/auto.conf FORCE
 	$(call filechk,rust_target)
-endif
 
 hostprogs += generate_rust_target
 generate_rust_target-rust := y

-- 
2.46.0