x86, build: allow LTO to be selected

Pass code model and stack alignment to the linker as these are not stored in LLVM bitcode, and allow CONFIG_LTO_CLANG* to be enabled. Signed-off-by: Sami Tolvanen <[email protected]> Reviewed-by: Kees Cook <[email protected]>
vieko · Feb 23, 2021 · b33fff0 · b33fff0
1 parent d2dcd3e
commit b33fff0
Show file tree

Hide file tree

Showing 2 changed files with 7 additions and 0 deletions.
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
@@ -95,6 +95,8 @@ config X86
 	select ARCH_SUPPORTS_DEBUG_PAGEALLOC
 	select ARCH_SUPPORTS_NUMA_BALANCING	if X86_64
 	select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP	if NR_CPUS <= 4096
+	select ARCH_SUPPORTS_LTO_CLANG		if X86_64
+	select ARCH_SUPPORTS_LTO_CLANG_THIN	if X86_64
 	select ARCH_USE_BUILTIN_BSWAP
 	select ARCH_USE_QUEUED_RWLOCKS
 	select ARCH_USE_QUEUED_SPINLOCKS

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
@@ -166,6 +166,11 @@ ifeq ($(ACCUMULATE_OUTGOING_ARGS), 1)
 	KBUILD_CFLAGS += $(call cc-option,-maccumulate-outgoing-args,)
 endif
 
+ifdef CONFIG_LTO_CLANG
+KBUILD_LDFLAGS	+= -plugin-opt=-code-model=kernel \
+		   -plugin-opt=-stack-alignment=$(if $(CONFIG_X86_32),4,8)
+endif
+
 # Workaround for a gcc prelease that unfortunately was shipped in a suse release
 KBUILD_CFLAGS += -Wno-sign-compare
 #