On Sun, Jul 4, 2021 at 1:28 PM <ojeda@xxxxxxxxxx> wrote: > > From: Miguel Ojeda <ojeda@xxxxxxxxxx> > > 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.gaynor@xxxxxxxxx> > Signed-off-by: Alex Gaynor <alex.gaynor@xxxxxxxxx> > Co-developed-by: Geoffrey Thomas <geofft@xxxxxxxxxxxxx> > Signed-off-by: Geoffrey Thomas <geofft@xxxxxxxxxxxxx> > Co-developed-by: Finn Behrens <me@xxxxxxxxx> > Signed-off-by: Finn Behrens <me@xxxxxxxxx> > Co-developed-by: Adam Bratschi-Kaye <ark.email@xxxxxxxxx> > Signed-off-by: Adam Bratschi-Kaye <ark.email@xxxxxxxxx> > Co-developed-by: Wedson Almeida Filho <wedsonaf@xxxxxxxxxx> > Signed-off-by: Wedson Almeida Filho <wedsonaf@xxxxxxxxxx> > Signed-off-by: Miguel Ojeda <ojeda@xxxxxxxxxx> Patch LGTM; please keep an eye on the series: https://lore.kernel.org/lkml/20210707224310.1403944-2-ndesaulniers@xxxxxxxxxx/ If that lands in kbuild before this, this patch will need to be rebased to avoid a conflict in linux-next. So (tentatively :-P): Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> If the patch needs to be rebased on the series linked above, please drop my reviewed by tag and I will re-review. Perhaps putting me explicitly on Cc: in the commit message will help notify me if there are successive versions? > --- > Makefile | 17 +++++++++++------ > 1 file changed, 11 insertions(+), 6 deletions(-) > > diff --git a/Makefile b/Makefile > index 0565caea036..6e823d8bd64 100644 > --- a/Makefile > +++ b/Makefile > @@ -573,18 +573,23 @@ endif > # and from include/config/auto.conf.cmd to detect the compiler upgrade. > CC_VERSION_TEXT = $(subst $(pound),,$(shell $(CC) --version 2>/dev/null | head -n 1)) > > -ifneq ($(findstring clang,$(CC_VERSION_TEXT)),) > +TENTATIVE_CLANG_FLAGS := -Werror=unknown-warning-option > + > ifneq ($(CROSS_COMPILE),) > -CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) > +TENTATIVE_CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) > endif > ifeq ($(LLVM_IAS),1) > -CLANG_FLAGS += -integrated-as > +TENTATIVE_CLANG_FLAGS += -integrated-as > else > -CLANG_FLAGS += -no-integrated-as > +TENTATIVE_CLANG_FLAGS += -no-integrated-as > 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 $(CROSS_COMPILE)) > endif > -CLANG_FLAGS += -Werror=unknown-warning-option > + > +export TENTATIVE_CLANG_FLAGS > + > +ifneq ($(findstring clang,$(CC_VERSION_TEXT)),) > +CLANG_FLAGS += $(TENTATIVE_CLANG_FLAGS) > KBUILD_CFLAGS += $(CLANG_FLAGS) > KBUILD_AFLAGS += $(CLANG_FLAGS) > export CLANG_FLAGS > -- > 2.32.0 > -- Thanks, ~Nick Desaulniers
