kbuild: lto: postpone objtool
With LTO, LLVM bitcode won't be compiled into native code until modpost_link, or modfinal for modules. This change postpones calls to objtool until after these steps, and moves objtool_args to Makefile.lib, so the arguments can be reused in Makefile.modfinal. As we didn't have objects to process earlier, we use --duplicate when processing vmlinux.o. This change also disables unreachable instruction warnings with LTO to avoid warnings about the int3 padding between functions. Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Sami Tolvanen
Kees Cook
parent
41425ebe20
commit
b1a1a1a09b
@ -218,30 +218,11 @@ cmd_record_mcount = $(if $(findstring $(strip $(CC_FLAGS_FTRACE)),$(_c_flags)),
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endif # CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
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ifdef CONFIG_STACK_VALIDATION
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ifndef CONFIG_LTO_CLANG
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ifneq ($(SKIP_STACK_VALIDATION),1)
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__objtool_obj := $(objtree)/tools/objtool/objtool
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objtool_args = $(if $(CONFIG_UNWINDER_ORC),orc generate,check)
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objtool_args += $(if $(part-of-module), --module,)
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ifndef CONFIG_FRAME_POINTER
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objtool_args += --no-fp
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endif
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ifdef CONFIG_GCOV_KERNEL
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objtool_args += --no-unreachable
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endif
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ifdef CONFIG_RETPOLINE
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objtool_args += --retpoline
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endif
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ifdef CONFIG_X86_SMAP
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objtool_args += --uaccess
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endif
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ifdef CONFIG_FTRACE_MCOUNT_USE_OBJTOOL
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objtool_args += --mcount
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endif
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# 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
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# 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file
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# 'OBJECT_FILES_NON_STANDARD_foo.o := 'n': override directory skip for a file
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@ -253,6 +234,7 @@ objtool_obj = $(if $(patsubst y%,, \
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$(__objtool_obj))
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endif # SKIP_STACK_VALIDATION
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endif # CONFIG_LTO_CLANG
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endif # CONFIG_STACK_VALIDATION
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# Rebuild all objects when objtool changes, or is enabled/disabled.
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@ -220,6 +220,18 @@ dtc_cpp_flags = -Wp,-MMD,$(depfile).pre.tmp -nostdinc \
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$(addprefix -I,$(DTC_INCLUDE)) \
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-undef -D__DTS__
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# Objtool arguments are also needed for modfinal with LTO, so we define
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# then here to avoid duplication.
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objtool_args = \
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$(if $(CONFIG_UNWINDER_ORC),orc generate,check) \
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$(if $(part-of-module), --module,) \
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$(if $(CONFIG_FRAME_POINTER),, --no-fp) \
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$(if $(or $(CONFIG_GCOV_KERNEL),$(CONFIG_LTO_CLANG)), \
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--no-unreachable,) \
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$(if $(CONFIG_RETPOLINE), --retpoline,) \
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$(if $(CONFIG_X86_SMAP), --uaccess,) \
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$(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount,)
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# Useful for describing the dependency of composite objects
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# Usage:
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# $(call multi_depend, multi_used_targets, suffix_to_remove, suffix_to_add)
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@ -9,7 +9,7 @@ __modfinal:
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include include/config/auto.conf
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include $(srctree)/scripts/Kbuild.include
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# for c_flags
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# for c_flags and objtool_args
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include $(srctree)/scripts/Makefile.lib
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# find all modules listed in modules.order
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@ -34,10 +34,23 @@ ifdef CONFIG_LTO_CLANG
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# With CONFIG_LTO_CLANG, reuse the object file we compiled for modpost to
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# avoid a second slow LTO link
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prelink-ext := .lto
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endif
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# ELF processing was skipped earlier because we didn't have native code,
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# so let's now process the prelinked binary before we link the module.
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ifdef CONFIG_STACK_VALIDATION
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ifneq ($(SKIP_STACK_VALIDATION),1)
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cmd_ld_ko_o += \
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$(objtree)/tools/objtool/objtool $(objtool_args) \
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$(@:.ko=$(prelink-ext).o);
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endif # SKIP_STACK_VALIDATION
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endif # CONFIG_STACK_VALIDATION
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endif # CONFIG_LTO_CLANG
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quiet_cmd_ld_ko_o = LD [M] $@
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cmd_ld_ko_o = \
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cmd_ld_ko_o += \
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$(LD) -r $(KBUILD_LDFLAGS) \
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$(KBUILD_LDFLAGS_MODULE) $(LDFLAGS_MODULE) \
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-T scripts/module.lds -o $@ $(filter %.o, $^); \
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@ -103,14 +103,36 @@ modpost_link()
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objtool_link()
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{
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local objtoolcmd;
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local objtoolopt;
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if [ "${CONFIG_LTO_CLANG} ${CONFIG_STACK_VALIDATION}" = "y y" ]; then
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# Don't perform vmlinux validation unless explicitly requested,
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# but run objtool on vmlinux.o now that we have an object file.
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if [ -n "${CONFIG_UNWINDER_ORC}" ]; then
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objtoolcmd="orc generate"
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fi
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objtoolopt="${objtoolopt} --duplicate"
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if [ -n "${CONFIG_FTRACE_MCOUNT_USE_OBJTOOL}" ]; then
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objtoolopt="${objtoolopt} --mcount"
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fi
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fi
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if [ -n "${CONFIG_VMLINUX_VALIDATION}" ]; then
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objtoolopt="check --vmlinux --noinstr"
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objtoolopt="${objtoolopt} --noinstr"
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fi
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if [ -n "${objtoolopt}" ]; then
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if [ -z "${objtoolcmd}" ]; then
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objtoolcmd="check"
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fi
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objtoolopt="${objtoolopt} --vmlinux"
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if [ -z "${CONFIG_FRAME_POINTER}" ]; then
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objtoolopt="${objtoolopt} --no-fp"
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fi
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if [ -n "${CONFIG_GCOV_KERNEL}" ]; then
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if [ -n "${CONFIG_GCOV_KERNEL}" ] || [ -n "${CONFIG_LTO_CLANG}" ]; then
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objtoolopt="${objtoolopt} --no-unreachable"
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fi
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if [ -n "${CONFIG_RETPOLINE}" ]; then
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@ -120,7 +142,7 @@ objtool_link()
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objtoolopt="${objtoolopt} --uaccess"
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fi
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info OBJTOOL ${1}
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tools/objtool/objtool ${objtoolopt} ${1}
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tools/objtool/objtool ${objtoolcmd} ${objtoolopt} ${1}
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fi
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}
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