cfi-sections := $(call as-instr,.cfi_sections .debug_frame,-DCONFIG_AS_CFI_SECTIONS=1)
# does binutils support specific instructions?
-asinstr := $(call as-instr,fxsaveq (%rax),-DCONFIG_AS_FXSAVEQ=1)
asinstr += $(call as-instr,pshufb %xmm0$(comma)%xmm0,-DCONFIG_AS_SSSE3=1)
avx_instr := $(call as-instr,vxorps %ymm0$(comma)%ymm1$(comma)%ymm2,-DCONFIG_AS_AVX=1)
avx2_instr :=$(call as-instr,vpbroadcastb %xmm0$(comma)%ymm1,-DCONFIG_AS_AVX2=1)
# Avoid indirect branches in kernel to deal with Spectre
ifdef CONFIG_RETPOLINE
KBUILD_CFLAGS += $(RETPOLINE_CFLAGS)
+ # Additionally, avoid generating expensive indirect jumps which
+ # are subject to retpolines for small number of switch cases.
+ # clang turns off jump table generation by default when under
+ # retpoline builds, however, gcc does not for x86. This has
+ # only been fixed starting from gcc stable version 8.4.0 and
+ # onwards, but not for older ones. See gcc bug #86952.
+ ifndef CONFIG_CC_IS_CLANG
+ KBUILD_CFLAGS += $(call cc-option,-fno-jump-tables)
+ endif
endif
archscripts: scripts_basic