On Wed, 23 Oct 2019 09:59:09 -0700 Sami Tolvanen <samitolvanen@xxxxxxxxxx> wrote: > On Tue, Oct 22, 2019 at 9:28 AM Mark Rutland <mark.rutland@xxxxxxx> wrote: > > I think it would be preferable to follow the example of CC_FLAGS_FTRACE > > so that this can be filtered out, e.g. > > > > ifdef CONFIG_SHADOW_CALL_STACK > > CFLAGS_SCS := -fsanitize=shadow-call-stack > > KBUILD_CFLAGS += $(CFLAGS_SCS) > > export CC_FLAGS_SCS > > endif > > > > ... with removal being: > > > > CFLAGS_REMOVE := $(CC_FLAGS_SCS) > > > > ... or: > > > > CFLAGS_REMOVE_obj.o := $(CC_FLAGS_SCS) > > > > That way you only need to define the flags once, so the enable and > > disable falgs remain in sync by construction. > > CFLAGS_REMOVE appears to be only implemented for objects, which means > there's no convenient way to filter out flags for everything in > arch/arm64/kvm/hyp, for example. I could add a CFLAGS_REMOVE > separately for each object file, or we could add something like > ccflags-remove-y to complement ccflags-y, which should be relatively > simple. Masahiro, do you have any suggestions? > You can remove a CFLAGS for a whole directory. lib, kernel/trace and others do this. Look at kernel/trace/Makefile, we have: ORIG_CFLAGS := $(KBUILD_CFLAGS) KBUILD_CFLAGS = $(subst $(CC_FLAGS_FTRACE),,$(ORIG_CFLAGS)) Where it removes CC_FLAGS_FTRACE from CFLAGS for all objects in the directory. -- Steve
