From: Miguel Ojeda <[email protected]>
To support Rust under GCC-built kernels, we need to save the flags that
would have been passed if the kernel was being compiled with Clang.
The reason is that bindgen -- the tool we use to generate Rust bindings
to the C side of the kernel -- relies on libclang to parse C. Ideally:
- bindgen would support a GCC backend (requested at [1]),
- or the Clang driver would be perfectly compatible with GCC,
including plugins. Unlikely, of course, but perhaps a big
subset of configs may be possible to guarantee to be kept
compatible nevertheless.
This is also the reason why GCC builds are very experimental and some
configurations may not work (e.g. GCC_PLUGIN_RANDSTRUCT). However,
we keep GCC builds working (for some example configs) in the CI
to avoid diverging/regressing further, so that we are better prepared
for the future when a solution might become available.
[1] https://github.com/rust-lang/rust-bindgen/issues/1949
Link: https://github.com/Rust-for-Linux/linux/issues/167
Co-developed-by: Alex Gaynor <[email protected]>
Signed-off-by: Alex Gaynor <[email protected]>
Co-developed-by: Geoffrey Thomas <[email protected]>
Signed-off-by: Geoffrey Thomas <[email protected]>
Co-developed-by: Finn Behrens <[email protected]>
Signed-off-by: Finn Behrens <[email protected]>
Co-developed-by: Adam Bratschi-Kaye <[email protected]>
Signed-off-by: Adam Bratschi-Kaye <[email protected]>
Co-developed-by: Wedson Almeida Filho <[email protected]>
Signed-off-by: Wedson Almeida Filho <[email protected]>
Signed-off-by: Miguel Ojeda <[email protected]>
---
Makefile | 27 ++++++++++++++++-----------
1 file changed, 16 insertions(+), 11 deletions(-)
diff --git a/Makefile b/Makefile
index d4784d181123..9c75354324ed 100644
--- a/Makefile
+++ b/Makefile
@@ -559,26 +559,31 @@ ifdef building_out_of_srctree
{ echo "# this is build directory, ignore it"; echo "*"; } > .gitignore
endif
-# The expansion should be delayed until arch/$(SRCARCH)/Makefile is included.
-# Some architectures define CROSS_COMPILE in arch/$(SRCARCH)/Makefile.
-# CC_VERSION_TEXT is referenced from Kconfig (so it needs export),
-# and from include/config/auto.conf.cmd to detect the compiler upgrade.
-CC_VERSION_TEXT = $(shell $(CC) --version 2>/dev/null | head -n 1 | sed
's/\#//g')
+TENTATIVE_CLANG_FLAGS := -Werror=unknown-warning-option
-ifneq ($(findstring clang,$(CC_VERSION_TEXT)),)
ifneq ($(CROSS_COMPILE),)
-CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%))
+TENTATIVE_CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%))
GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit))
-CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE))
+TENTATIVE_CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir
$(CROSS_COMPILE))
GCC_TOOLCHAIN := $(realpath $(GCC_TOOLCHAIN_DIR)/..)
endif
ifneq ($(GCC_TOOLCHAIN),)
-CLANG_FLAGS += --gcc-toolchain=$(GCC_TOOLCHAIN)
+TENTATIVE_CLANG_FLAGS += --gcc-toolchain=$(GCC_TOOLCHAIN)
endif
ifneq ($(LLVM_IAS),1)
-CLANG_FLAGS += -no-integrated-as
+TENTATIVE_CLANG_FLAGS += -no-integrated-as
endif
-CLANG_FLAGS += -Werror=unknown-warning-option
+
+export TENTATIVE_CLANG_FLAGS
+
+# The expansion should be delayed until arch/$(SRCARCH)/Makefile is included.
+# Some architectures define CROSS_COMPILE in arch/$(SRCARCH)/Makefile.
+# CC_VERSION_TEXT is referenced from Kconfig (so it needs export),
+# and from include/config/auto.conf.cmd to detect the compiler upgrade.
+CC_VERSION_TEXT = $(shell $(CC) --version 2>/dev/null | head -n 1 | sed
's/\#//g')
+
+ifneq ($(findstring clang,$(CC_VERSION_TEXT)),)
+CLANG_FLAGS += $(TENTATIVE_CLANG_FLAGS)
KBUILD_CFLAGS += $(CLANG_FLAGS)
KBUILD_AFLAGS += $(CLANG_FLAGS)
export CLANG_FLAGS
--
2.17.1
