[PATCH 02/27] kbuild: Add CONFIG_OBJTOOL_DEFERRED

[Josh Poimboeuf]

For LTO, IBT, and KLP builds, the running of objtool is deferred to
vmlinux.o rather than individual translation units.  In preparation for
deferring it in more cases, add a new config option.

No functional change.

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
 arch/x86/boot/startup/Makefile |  2 +-
 lib/Kconfig.debug              |  7 +++++++
 scripts/Makefile.build         |  4 ++--
 scripts/Makefile.lib           |  4 +---
 scripts/Makefile.vmlinux_o     | 13 +++++++------
 scripts/link-vmlinux.sh        |  3 +--
 6 files changed, 19 insertions(+), 14 deletions(-)

diff --git a/arch/x86/boot/startup/Makefile b/arch/x86/boot/startup/Makefile
index 5e499cfb29b5c..ab6e9970d4f4e 100644
--- a/arch/x86/boot/startup/Makefile
+++ b/arch/x86/boot/startup/Makefile
@@ -36,7 +36,7 @@ $(patsubst %.o,$(obj)/%.o,$(lib-y)): OBJECT_FILES_NON_STANDARD := y
 # relocations, even if other objtool actions are being deferred.
 #
 $(pi-objs): objtool-enabled	= 1
-$(pi-objs): objtool-args	= $(if $(delay-objtool),--dry-run,$(objtool-args-y)) --noabs
+$(pi-objs): objtool-args	= $(if $(CONFIG_OBJTOOL_DEFERRED),--dry-run,$(objtool-args-y)) --noabs
 
 #
 # Confine the startup code by prefixing all symbols with __pi_ (for position
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 1244dcac2294a..9ca9b2519d604 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -588,6 +588,13 @@ config NOINSTR_VALIDATION
 	select OBJTOOL
 	default y
 
+# For when objtool defers its work to the linked image (vmlinux.o or module.o)
+# rather than running on individual translation units.
+config OBJTOOL_DEFERRED
+	def_bool y
+	depends on OBJTOOL
+	depends on LTO_CLANG || X86_KERNEL_IBT || KLP_BUILD
+
 config VMLINUX_MAP
 	bool "Generate vmlinux.map file when linking"
 	depends on EXPERT
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 9117457432463..84ef12f784330 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -277,7 +277,7 @@ endif # CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
 is-standard-object = $(if $(filter-out y%, $(OBJECT_FILES_NON_STANDARD_$(target-stem).o)$(OBJECT_FILES_NON_STANDARD)n),$(is-kernel-object))
 
 ifdef CONFIG_OBJTOOL
-$(obj)/%.o: private objtool-enabled = $(if $(is-standard-object),$(if $(delay-objtool),$(is-single-obj-m),y))
+$(obj)/%.o: private objtool-enabled = $(if $(is-standard-object),$(if $(CONFIG_OBJTOOL_DEFERRED),$(is-single-obj-m),y))
 endif
 
 ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),)
@@ -502,7 +502,7 @@ define rule_ld_multi_m
 	$(call cmd,gen_objtooldep)
 endef
 
-$(multi-obj-m): private objtool-enabled := $(delay-objtool)
+$(multi-obj-m): private objtool-enabled := $(CONFIG_OBJTOOL_DEFERRED)
 $(multi-obj-m): private part-of-module := y
 $(multi-obj-m): %.o: %.mod FORCE
 	$(call if_changed_rule,ld_multi_m)
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 0a4fdd8bd975d..3622237e41d2e 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -210,11 +210,9 @@ objtool-args-$(or $(CONFIG_GCOV_KERNEL),$(CONFIG_KCOV))	+= --no-unreachable
 objtool-args-$(CONFIG_OBJTOOL_WERROR)			+= --werror
 
 objtool-args = $(objtool-args-y)					\
-	$(if $(delay-objtool), --link)					\
+	$(if $(CONFIG_OBJTOOL_DEFERRED), --link)			\
 	$(if $(part-of-module), --module)
 
-delay-objtool := $(or $(CONFIG_LTO_CLANG),$(CONFIG_X86_KERNEL_IBT),$(CONFIG_KLP_BUILD))
-
 cmd_objtool = $(if $(objtool-enabled), ; $(objtool) $(objtool-args) $@)
 cmd_gen_objtooldep = $(if $(objtool-enabled), { echo ; echo '$@: $$(wildcard $(objtool))' ; } >> $(dot-target).cmd)
 
diff --git a/scripts/Makefile.vmlinux_o b/scripts/Makefile.vmlinux_o
index 24a3a4fd271c2..9bac917e8b819 100644
--- a/scripts/Makefile.vmlinux_o
+++ b/scripts/Makefile.vmlinux_o
@@ -30,15 +30,16 @@ endif
 # objtool for vmlinux.o
 # ---------------------------------------------------------------------------
 #
-# For delay-objtool (IBT or LTO), objtool doesn't run on individual translation
-# units.  Instead it runs on vmlinux.o.
+# For CONFIG_OBJTOOL_DEFERRED (IBT or LTO), objtool doesn't run on individual
+# translation units.  Instead it runs on vmlinux.o.
 #
-# For !delay-objtool + CONFIG_NOINSTR_VALIDATION, it runs on both translation
-# units and vmlinux.o, with the latter only used for noinstr/unret validation.
+# For !CONFIG_OBJTOOL_DEFERRED + CONFIG_NOINSTR_VALIDATION, it runs on both
+# translation units and vmlinux.o, with the latter only used for noinstr/unret
+# validation.
 
-objtool-enabled := $(or $(delay-objtool),$(CONFIG_NOINSTR_VALIDATION))
+objtool-enabled := $(or $(CONFIG_OBJTOOL_DEFERRED),$(CONFIG_NOINSTR_VALIDATION))
 
-ifeq ($(delay-objtool),y)
+ifeq ($(CONFIG_OBJTOOL_DEFERRED),y)
 vmlinux-objtool-args-y					+= $(objtool-args-y)
 else
 vmlinux-objtool-args-$(CONFIG_OBJTOOL_WERROR)		+= --werror
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index f99e196abeea4..aa10867a04de2 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -60,8 +60,7 @@ vmlinux_link()
 	# skip output file argument
 	shift
 
-	if is_enabled CONFIG_LTO_CLANG || is_enabled CONFIG_X86_KERNEL_IBT ||
-	   is_enabled CONFIG_KLP_BUILD; then
+	if is_enabled CONFIG_OBJTOOL_DEFERRED || is_enabled CONFIG_LTO_CLANG; then
 		# Use vmlinux.o instead of performing the slow LTO link again.
 		objs=vmlinux.o
 		libs=
-- 
2.55.0