# Make variables (CC, etc...)
AS = $(CROSS_COMPILE)as
LD = $(CROSS_COMPILE)ld
+LDGOLD = $(CROSS_COMPILE)ld.gold
CC = $(CROSS_COMPILE)gcc
CPP = $(CC) -E
AR = $(CROSS_COMPILE)ar
ifeq ($(cc-name),clang)
ifneq ($(CROSS_COMPILE),)
-CLANG_TARGET := --target=$(notdir $(CROSS_COMPILE:%-=%))
+CLANG_TRIPLE ?= $(CROSS_COMPILE)
+CLANG_TARGET := --target=$(notdir $(CLANG_TRIPLE:%-=%))
GCC_TOOLCHAIN := $(realpath $(dir $(shell which $(LD)))/..)
endif
ifneq ($(GCC_TOOLCHAIN),)
CFLAGS_KCOV := $(call cc-option,-fsanitize-coverage=trace-pc,)
export CFLAGS_GCOV CFLAGS_KCOV
+# Make toolchain changes before including arch/$(SRCARCH)/Makefile to ensure
+# ar/cc/ld-* macros return correct values.
+ifdef CONFIG_LTO_CLANG
+# use GNU gold with LLVMgold for LTO linking, and LD for vmlinux_link
+LDFINAL_vmlinux := $(LD)
+LD := $(LDGOLD)
+LDFLAGS += -plugin LLVMgold.so
+# use llvm-ar for building symbol tables from IR files, and llvm-dis instead
+# of objdump for processing symbol versions and exports
+LLVM_AR := llvm-ar
+LLVM_DIS := llvm-dis
+export LLVM_AR LLVM_DIS
+endif
+
# The arch Makefile can set ARCH_{CPP,A,C}FLAGS to override the default
# values of the respective KBUILD_* variables
ARCH_CPPFLAGS :=
KBUILD_CFLAGS += $(call cc-disable-warning, format-invalid-specifier)
KBUILD_CFLAGS += $(call cc-disable-warning, gnu)
KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
+KBUILD_CFLAGS += $(call cc-disable-warning, duplicate-decl-specifier)
# Quiet clang warning: comparison of unsigned expression < 0 is always false
KBUILD_CFLAGS += $(call cc-disable-warning, tautological-compare)
# CLANG uses a _MergedGlobals as optimization, but this breaks modpost, as the
KBUILD_CFLAGS += $(call cc-option,-fdata-sections,)
endif
+ifdef CONFIG_LTO_CLANG
+lto-clang-flags := -flto -fvisibility=hidden
+
+# allow disabling only clang LTO where needed
+DISABLE_LTO_CLANG := -fno-lto -fvisibility=default
+export DISABLE_LTO_CLANG
+endif
+
+ifdef CONFIG_LTO
+lto-flags := $(lto-clang-flags)
+KBUILD_CFLAGS += $(lto-flags)
+
+DISABLE_LTO := $(DISABLE_LTO_CLANG)
+export DISABLE_LTO
+
+# LDFINAL_vmlinux and LDFLAGS_FINAL_vmlinux can be set to override
+# the linker and flags for vmlinux_link.
+export LDFINAL_vmlinux LDFLAGS_FINAL_vmlinux
+endif
+
+ifdef CONFIG_CFI_CLANG
+cfi-clang-flags += -fsanitize=cfi
+DISABLE_CFI_CLANG := -fno-sanitize=cfi
+ifdef CONFIG_MODULES
+cfi-clang-flags += -fsanitize-cfi-cross-dso
+DISABLE_CFI_CLANG += -fno-sanitize-cfi-cross-dso
+endif
+ifdef CONFIG_CFI_PERMISSIVE
+cfi-clang-flags += -fsanitize-recover=cfi -fno-sanitize-trap=cfi
+endif
+
+# also disable CFI when LTO is disabled
+DISABLE_LTO_CLANG += $(DISABLE_CFI_CLANG)
+# allow disabling only clang CFI where needed
+export DISABLE_CFI_CLANG
+endif
+
+ifdef CONFIG_CFI
+# cfi-flags are re-tested in prepare-compiler-check
+cfi-flags := $(cfi-clang-flags)
+KBUILD_CFLAGS += $(cfi-flags)
+
+DISABLE_CFI := $(DISABLE_CFI_CLANG)
+DISABLE_LTO += $(DISABLE_CFI)
+export DISABLE_CFI
+endif
+
# arch Makefile may override CC so keep this after arch Makefile is included
NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
CHECKFLAGS += $(NOSTDINC_FLAGS)
# CC_STACKPROTECTOR_STRONG! Why did it build with _REGULAR?!")
PHONY += prepare-compiler-check
prepare-compiler-check: FORCE
+# Make sure we're using a supported toolchain with LTO_CLANG
+ifdef CONFIG_LTO_CLANG
+ ifneq ($(call clang-ifversion, -ge, 0500, y), y)
+ @echo Cannot use CONFIG_LTO_CLANG: requires clang 5.0 or later >&2 && exit 1
+ endif
+ ifneq ($(call gold-ifversion, -ge, 112000000, y), y)
+ @echo Cannot use CONFIG_LTO_CLANG: requires GNU gold 1.12 or later >&2 && exit 1
+ endif
+endif
+# Make sure compiler supports LTO flags
+ifdef lto-flags
+ ifeq ($(call cc-option, $(lto-flags)),)
+ @echo Cannot use CONFIG_LTO: $(lto-flags) not supported by compiler \
+ >&2 && exit 1
+ endif
+endif
# Make sure compiler supports requested stack protector flag.
ifdef stackp-name
ifeq ($(call cc-option, $(stackp-flag)),)
@echo Cannot use CONFIG_CC_STACKPROTECTOR_$(stackp-name): \
$(stackp-flag) available but compiler is broken >&2 && exit 1
endif
+endif
+ifdef cfi-flags
+ ifeq ($(call cc-option, $(cfi-flags)),)
+ @echo Cannot use CONFIG_CFI: $(cfi-flags) not supported by compiler >&2 && exit 1
+ endif
endif
@:
-o -name modules.builtin -o -name '.tmp_*.o.*' \
-o -name '*.c.[012]*.*' \
-o -name '*.ll' \
- -o -name '*.gcno' \) -type f -print | xargs rm -f
+ -o -name '*.gcno' \
+ -o -name '*.*.symversions' \) -type f -print | xargs rm -f
# Generate tags for editors
# ---------------------------------------------------------------------------