Commit 414eece9 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'clang-lto-v5.12-rc1-part2' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux 

Pull more clang LTO updates from Kees Cook:
 "Clang LTO x86 enablement.

  Full disclosure: while this has _not_ been in linux-next (since it
  initially looked like the objtool dependencies weren't going to make
  v5.12), it has been under daily build and runtime testing by Sami for
  quite some time. These x86 portions have been discussed on lkml, with
  Peter, Josh, and others helping nail things down.

  The bulk of the changes are to get objtool working happily. The rest
  of the x86 enablement is very small.

  Summary:

   - Generate __mcount_loc in objtool (Peter Zijlstra)

   - Support running objtool against vmlinux.o (Sami Tolvanen)

   - Clang LTO enablement for x86 (Sami Tolvanen)"

Link: https://lore.kernel.org/lkml/20201013003203.4168817-26-samitolvanen@google.com/
Link: https://lore.kernel.org/lkml/cover.1611263461.git.jpoimboe@redhat.com/

* tag 'clang-lto-v5.12-rc1-part2' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  kbuild: lto: force rebuilds when switching CONFIG_LTO
  x86, build: allow LTO to be selected
  x86, cpu: disable LTO for cpu.c
  x86, vdso: disable LTO only for vDSO
  kbuild: lto: postpone objtool
  objtool: Split noinstr validation from --vmlinux
  x86, build: use objtool mcount
  tracing: add support for objtool mcount
  objtool: Don't autodetect vmlinux.o
  objtool: Fix __mcount_loc generation with Clang's assembler
  objtool: Add a pass for generating __mcount_loc
parents 6dd580b9 5e95325f

Makefile

+9 −1
Original line number Diff line number Diff line
@@ -862,6 +862,9 @@ ifdef CONFIG_FTRACE_MCOUNT_USE_CC 
    endif

  endif

endif

ifdef CONFIG_FTRACE_MCOUNT_USE_OBJTOOL

  CC_FLAGS_USING	+= -DCC_USING_NOP_MCOUNT

endif

ifdef CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT

  ifdef CONFIG_HAVE_C_RECORDMCOUNT

    BUILD_C_RECORDMCOUNT := y
@@ -909,7 +912,8 @@ KBUILD_LDFLAGS += -mllvm -import-instr-limit=5 
endif



ifdef CONFIG_LTO

KBUILD_CFLAGS	+= $(CC_FLAGS_LTO)

KBUILD_CFLAGS	+= -fno-lto $(CC_FLAGS_LTO)

KBUILD_AFLAGS	+= -fno-lto

export CC_FLAGS_LTO

endif
@@ -1243,6 +1247,10 @@ uapi-asm-generic: 
PHONY += prepare-objtool prepare-resolve_btfids

prepare-objtool: $(objtool_target)

ifeq ($(SKIP_STACK_VALIDATION),1)

ifdef CONFIG_FTRACE_MCOUNT_USE_OBJTOOL

	@echo "error: Cannot generate __mcount_loc for CONFIG_DYNAMIC_FTRACE=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel" >&2

	@false

endif

ifdef CONFIG_UNWINDER_ORC

	@echo "error: Cannot generate ORC metadata for CONFIG_UNWINDER_ORC=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel" >&2

	@false

arch/x86/Kconfig

+3 −0
Original line number Diff line number Diff line
@@ -97,6 +97,8 @@ 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
@@ -169,6 +171,7 @@ config X86 
	select HAVE_CONTEXT_TRACKING		if X86_64

	select HAVE_CONTEXT_TRACKING_OFFSTACK	if HAVE_CONTEXT_TRACKING

	select HAVE_C_RECORDMCOUNT

	select HAVE_OBJTOOL_MCOUNT		if STACK_VALIDATION

	select HAVE_DEBUG_KMEMLEAK

	select HAVE_DMA_CONTIGUOUS

	select HAVE_DYNAMIC_FTRACE

arch/x86/Makefile

+5 −0
Original line number Diff line number Diff line
@@ -169,6 +169,11 @@ 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

#

arch/x86/entry/vdso/Makefile

+2 −1
Original line number Diff line number Diff line
@@ -91,7 +91,7 @@ ifneq ($(RETPOLINE_VDSO_CFLAGS),) 
endif

endif



$(vobjs): KBUILD_CFLAGS := $(filter-out $(GCC_PLUGINS_CFLAGS) $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)

$(vobjs): KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO) $(GCC_PLUGINS_CFLAGS) $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)



#

# vDSO code runs in userspace and -pg doesn't help with profiling anyway.
@@ -150,6 +150,7 @@ KBUILD_CFLAGS_32 := $(filter-out -fno-pic,$(KBUILD_CFLAGS_32)) 
KBUILD_CFLAGS_32 := $(filter-out -mfentry,$(KBUILD_CFLAGS_32))

KBUILD_CFLAGS_32 := $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS_32))

KBUILD_CFLAGS_32 := $(filter-out $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS_32))

KBUILD_CFLAGS_32 := $(filter-out $(CC_FLAGS_LTO),$(KBUILD_CFLAGS_32))

KBUILD_CFLAGS_32 += -m32 -msoft-float -mregparm=0 -fpic

KBUILD_CFLAGS_32 += -fno-stack-protector

KBUILD_CFLAGS_32 += $(call cc-option, -foptimize-sibling-calls)

arch/x86/power/Makefile

+4 −0
Original line number Diff line number Diff line
@@ -4,5 +4,9 @@ 
# itself be stack-protected

CFLAGS_cpu.o	:= -fno-stack-protector



# Clang may incorrectly inline functions with stack protector enabled into

# __restore_processor_state(): https://bugs.llvm.org/show_bug.cgi?id=47479

CFLAGS_REMOVE_cpu.o := $(CC_FLAGS_LTO)



obj-$(CONFIG_PM_SLEEP)		+= cpu.o

obj-$(CONFIG_HIBERNATION)	+= hibernate_$(BITS).o hibernate_asm_$(BITS).o hibernate.o