kbuild: store the objtool command in *.cmd files

objtool_dep includes include/config/{ORC_UNWINDER,STACK_VALIDATION}
so that all the objects are rebuilt when CONFIG_ORC_UNWINDER or
CONFIG_STACK_VALIDATION is toggled.

BTW, the correct option name is not CONFIG_ORC_UNWINDER, but
CONFIG_UNWINDER_ORC. Commit 11af847446ed ("x86/unwind: Rename
unwinder config options to 'CONFIG_UNWINDER_*'") missed to
adjust this part. So, this dependency has been broken for a
long time.

As you can see in 'objtool_args', there are more CONFIG options
that affect the objtool command line.

Adding more and more include/config/* is ugly and unmaintainable.

Another issue is that non-standard objects are needlessly rebuilt.
Objects specified as OBJECT_FILES_NON_STANDARD is not processed by
objtool, but they are rebuilt anyway when CONFIG_STACK_VALIDATION
is toggled. This is not a big deal, but better to fix.

A cleaner and more precise fix is to include the objtool command in
*.cmd files so any command change is naturally detected by if_change.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index e78096cd396b2d09b2f5f4e40263d77d23fcfd93..021ae0146913227c85ee50a93a0697a6a62cc557 100644 (file)
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -155,7 +155,7 @@ $(obj)/%.ll: $(src)/%.c FORCE
 # (See cmd_cc_o_c + relevant part of rule_cc_o_c)
 
 quiet_cmd_cc_o_c = CC $(quiet_modtag)  $@
-      cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<
+      cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $< $(cmd_objtool)
 
 ifdef CONFIG_MODVERSIONS
 # When module versioning is enabled the following steps are executed:
@@ -243,7 +243,7 @@ ifndef CONFIG_LTO_CLANG
 # 'OBJECT_FILES_NON_STANDARD_foo.o := 'n': override directory skip for a file
 cmd_objtool = $(if $(patsubst y%,, \
        $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
-       $(objtool) $(objtool_args) $@)
+       ; $(objtool) $(objtool_args) $@)
 objtool_obj = $(if $(patsubst y%,, \
        $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
        $(objtool))
@@ -251,10 +251,8 @@ objtool_obj = $(if $(patsubst y%,, \
 endif # CONFIG_LTO_CLANG
 endif # CONFIG_STACK_VALIDATION
 
-# Rebuild all objects when objtool changes, or is enabled/disabled.
-objtool_dep = $(objtool_obj)                                   \
-             $(wildcard include/config/ORC_UNWINDER            \
-                        include/config/STACK_VALIDATION)
+# Rebuild all objects when objtool changes
+objtool_dep = $(objtool_obj)
 
 ifdef CONFIG_TRIM_UNUSED_KSYMS
 cmd_gen_ksymdeps = \
@@ -269,7 +267,6 @@ define rule_cc_o_c
        $(call cmd,gen_ksymdeps)
        $(call cmd,checksrc)
        $(call cmd,checkdoc)
-       $(call cmd,objtool)
        $(call cmd,modversions_c)
        $(call cmd,record_mcount)
 endef
@@ -277,7 +274,6 @@ endef
 define rule_as_o_S
        $(call cmd_and_fixdep,as_o_S)
        $(call cmd,gen_ksymdeps)
-       $(call cmd,objtool)
        $(call cmd,modversions_S)
 endef
 
@@ -365,7 +361,7 @@ $(obj)/%.s: $(src)/%.S FORCE
        $(call if_changed_dep,cpp_s_S)
 
 quiet_cmd_as_o_S = AS $(quiet_modtag)  $@
-      cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $<
+      cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $< $(cmd_objtool)
 
 ifdef CONFIG_ASM_MODVERSIONS