On Wed, 19 Feb 2020 at 01:09, Sami Tolvanen <samitolvanen@xxxxxxxxxx> wrote: > > Disable SCS for the EFI stub and allow x18 to be used. > > Suggested-by: James Morse <james.morse@xxxxxxx> > Signed-off-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx> > --- > drivers/firmware/efi/libstub/Makefile | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile > index 98a81576213d..dff9fa5a3f1c 100644 > --- a/drivers/firmware/efi/libstub/Makefile > +++ b/drivers/firmware/efi/libstub/Makefile > @@ -30,6 +30,9 @@ KBUILD_CFLAGS := $(cflags-y) -DDISABLE_BRANCH_PROFILING \ > $(call cc-option,-fno-stack-protector) \ > -D__DISABLE_EXPORTS > > +# remove SCS flags from all objects in this directory > +KBUILD_CFLAGS := $(filter-out -ffixed-x18 $(CC_FLAGS_SCS), $(KBUILD_CFLAGS)) > + I don't see why you'd need to remove -ffixed-x18 again here. Not using x18 anywhere in the kernel is a much more maintainable approach. In fact, now that I think of it, the EFI AArch64 platform binding forbids the use of x18, so it would be better to add the -ffixed-x18 unconditionally for arm64 (even though the reason it forbids it is to ensure compatibility with an OS using it as a platform register, and so nothing is actually broken atm). > GCOV_PROFILE := n > KASAN_SANITIZE := n > UBSAN_SANITIZE := n > -- > 2.25.0.265.gbab2e86ba0-goog >
