Hi Miguel, On Wed, Apr 14, 2021 at 08:45:54PM +0200, oj...@kernel.org wrote: > From: Miguel Ojeda <oj...@kernel.org> > > 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 <alex.gay...@gmail.com> > Signed-off-by: Alex Gaynor <alex.gay...@gmail.com> > Co-developed-by: Geoffrey Thomas <geo...@ldpreload.com> > Signed-off-by: Geoffrey Thomas <geo...@ldpreload.com> > Co-developed-by: Finn Behrens <m...@kloenk.de> > Signed-off-by: Finn Behrens <m...@kloenk.de> > Co-developed-by: Adam Bratschi-Kaye <ark.em...@gmail.com> > Signed-off-by: Adam Bratschi-Kaye <ark.em...@gmail.com> > Co-developed-by: Wedson Almeida Filho <wedso...@google.com> > Signed-off-by: Wedson Almeida Filho <wedso...@google.com> > Signed-off-by: Miguel Ojeda <oj...@kernel.org> > --- > 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 $(CROSS_COMPILE)elfedit))
Shuffling this around will cause this issue (I never saw you CC'd on the thread). https://lore.kernel.org/r/f6218ac526a04fa4d4406f935bcc4eb4a7df65c4.1617917438.git.msucha...@suse.de/ Perhaps that patch should be added to this series? > -CLANG_FLAGS += --prefix=$(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 >
