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- Remove and simplify a bunch of cc-option and compiler version checks

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in the build machinery now that the minimal version of both compilers
   supports them
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Merge tag 'x86_build_for_v6.18_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 build updates from Borislav Petkov:

 - Remove and simplify a bunch of cc-option and compiler version checks
   in the build machinery now that the minimal version of both compilers
   supports them

* tag 'x86_build_for_v6.18_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/Kconfig: Clean up LLVM version checks in IBT configurations
  x86/build: Remove cc-option from -mskip-rax-setup
  x86/build: Remove cc-option from -mno-fp-ret-in-387
  x86/build: Clean up stack alignment flags in CC_FLAGS_FPU
  x86/build: Remove cc-option from stack alignment flags
  x86/build: Remove cc-option for GCC retpoline flags
This commit is contained in:
Linus Torvalds 2025-09-30 12:17:22 -07:00
commit 163d9c6b33
2 changed files with 8 additions and 25 deletions
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8
arch/x86/Kconfig
View File

@ -1734,11 +1734,7 @@ config X86_UMIP
config CC_HAS_IBT
# GCC >= 9 and binutils >= 2.29
# Retpoline check to work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93654
# Clang/LLVM >= 14
# https://github.com/llvm/llvm-project/commit/e0b89df2e0f0130881bf6c39bf31d7f6aac00e0f
# https://github.com/llvm/llvm-project/commit/dfcf69770bc522b9e411c66454934a37c1f35332
def_bool ((CC_IS_GCC && $(cc-option, -fcf-protection=branch -mindirect-branch-register)) || \
(CC_IS_CLANG && CLANG_VERSION >= 140000)) && \
def_bool ((CC_IS_GCC && $(cc-option, -fcf-protection=branch -mindirect-branch-register)) || CC_IS_CLANG) && \
$(as-instr,endbr64)
config X86_CET
@ -1750,8 +1746,6 @@ config X86_KERNEL_IBT
prompt "Indirect Branch Tracking"
def_bool y
depends on X86_64 && CC_HAS_IBT && HAVE_OBJTOOL
# https://github.com/llvm/llvm-project/commit/9d7001eba9c4cb311e03cd8cdc231f9e579f2d0f
depends on !LD_IS_LLD || LLD_VERSION >= 140000
select OBJTOOL
select X86_CET
help

25
arch/x86/Makefile
View File

@ -13,8 +13,8 @@ else
endif
ifdef CONFIG_CC_IS_GCC
RETPOLINE_CFLAGS := $(call cc-option,-mindirect-branch=thunk-extern -mindirect-branch-register)
RETPOLINE_VDSO_CFLAGS := $(call cc-option,-mindirect-branch=thunk-inline -mindirect-branch-register)
RETPOLINE_CFLAGS := -mindirect-branch=thunk-extern -mindirect-branch-register
RETPOLINE_VDSO_CFLAGS := -mindirect-branch=thunk-inline -mindirect-branch-register
endif
ifdef CONFIG_CC_IS_CLANG
RETPOLINE_CFLAGS := -mretpoline-external-thunk
@ -37,10 +37,11 @@ export RETPOLINE_VDSO_CFLAGS
# For gcc stack alignment is specified with -mpreferred-stack-boundary,
# clang has the option -mstack-alignment for that purpose.
ifneq ($(call cc-option, -mpreferred-stack-boundary=4),)
ifdef CONFIG_CC_IS_GCC
cc_stack_align4 := -mpreferred-stack-boundary=2
cc_stack_align8 := -mpreferred-stack-boundary=3
else ifneq ($(call cc-option, -mstack-alignment=16),)
endif
ifdef CONFIG_CC_IS_CLANG
cc_stack_align4 := -mstack-alignment=4
cc_stack_align8 := -mstack-alignment=8
endif
@ -83,19 +84,7 @@ KBUILD_RUSTFLAGS += -Ctarget-feature=-sse,-sse2,-sse3,-ssse3,-sse4.1,-sse4.2,-av
#
CC_FLAGS_FPU := -msse -msse2
ifdef CONFIG_CC_IS_GCC
# Stack alignment mismatch, proceed with caution.
# GCC < 7.1 cannot compile code using `double` and -mpreferred-stack-boundary=3
# (8B stack alignment).
# See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53383
#
# The "-msse" in the first argument is there so that the
# -mpreferred-stack-boundary=3 build error:
#
# -mpreferred-stack-boundary=3 is not between 4 and 12
#
# can be triggered. Otherwise gcc doesn't complain.
CC_FLAGS_FPU += -mhard-float
CC_FLAGS_FPU += $(call cc-option,-msse -mpreferred-stack-boundary=3,-mpreferred-stack-boundary=4)
endif
ifeq ($(CONFIG_X86_KERNEL_IBT),y)
@ -159,7 +148,7 @@ else
# Don't autogenerate traditional x87 instructions
KBUILD_CFLAGS += -mno-80387
KBUILD_CFLAGS += $(call cc-option,-mno-fp-ret-in-387)
KBUILD_CFLAGS += -mno-fp-ret-in-387
# By default gcc and clang use a stack alignment of 16 bytes for x86.
# However the standard kernel entry on x86-64 leaves the stack on an
@ -171,7 +160,7 @@ else
KBUILD_CFLAGS += $(cc_stack_align8)
# Use -mskip-rax-setup if supported.
KBUILD_CFLAGS += $(call cc-option,-mskip-rax-setup)
KBUILD_CFLAGS += -mskip-rax-setup
ifdef CONFIG_X86_NATIVE_CPU
KBUILD_CFLAGS += -march=native