linux-kernel - [PATCH v2 4/9] kbuild: refactor modversions build rules

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Message-Id: <1542675930-21114-5-git-send-email-yamada.masahiro@socionext.com>
Date:   Tue, 20 Nov 2018 10:05:25 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     linux-kbuild@...r.kernel.org
Cc:     Sam Ravnborg <sam@...nborg.org>,
        Nicolas Pitre <nicolas.pitre@...aro.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 4/9] kbuild: refactor modversions build rules

Let $(CC) compile objects into normal files *.o instead of .tmp_*.o
whether CONFIG_MODVERSIONS is enabled or not. With this, the input
file for objtool is always *.o so objtool_o can go away.

I guess the reason of using .tmp_*.o for intermediate objects was
to avoid leaving incomplete *.o file (, whose timestamp says it is
up-to-date) when the genksyms tool failed for some reasons.

It no longer matters because any targets are deleted on errors since
commit 9c2af1c7377a ("kbuild: add .DELETE_ON_ERROR special target").

Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
---

Changes in v2:
 - Clarify the benefit of this patch
   It is nice to delete objtool_o and ease the following commits

 scripts/Makefile.build | 54 ++++++++++++++++----------------------------------
 1 file changed, 17 insertions(+), 37 deletions(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 032ca24..4f94579 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -154,35 +154,30 @@ $(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 $@ $<
 
-ifndef CONFIG_MODVERSIONS
-cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<
-
-else
+ifdef CONFIG_MODVERSIONS
 # When module versioning is enabled the following steps are executed:
-# o compile a .tmp_<file>.o from <file>.c
-# o if .tmp_<file>.o doesn't contain a __ksymtab version, i.e. does
-#   not export symbols, we just rename .tmp_<file>.o to <file>.o and
-#   are done.
+# o compile a <file>.o from <file>.c
+# o if <file>.o doesn't contain a __ksymtab version, i.e. does
+#   not export symbols, it's done.
 # o otherwise, we calculate symbol versions using the good old
 #   genksyms on the preprocessed source and postprocess them in a way
 #   that they are usable as a linker script
-# o generate <file>.o from .tmp_<file>.o using the linker to
+# o generate .tmp_<file>.o from <file>.o using the linker to
 #   replace the unresolved symbols __crc_exported_symbol with
 #   the actual value of the checksum generated by genksyms
-
-cmd_cc_o_c = $(CC) $(c_flags) -c -o $(@D)/.tmp_$(@F) $<
+# o remove .tmp_<file>.o to <file>.o
 
 cmd_modversions_c =								\
-	if $(OBJDUMP) -h $(@D)/.tmp_$(@F) | grep -q __ksymtab; then		\
+	if $(OBJDUMP) -h $@ | grep -q __ksymtab; then				\
 		$(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))	\
 		    > $(@D)/.tmp_$(@F:.o=.ver);					\
 										\
-		$(LD) $(KBUILD_LDFLAGS) -r -o $@ $(@D)/.tmp_$(@F) 		\
+		$(LD) $(KBUILD_LDFLAGS) -r -o $(@D)/.tmp_$(@F) $@ 		\
 			-T $(@D)/.tmp_$(@F:.o=.ver);				\
-		rm -f $(@D)/.tmp_$(@F) $(@D)/.tmp_$(@F:.o=.ver);		\
-	else									\
 		mv -f $(@D)/.tmp_$(@F) $@;					\
+		rm -f $(@D)/.tmp_$(@F:.o=.ver);					\
 	fi;
 endif
 
@@ -241,19 +236,12 @@ ifneq ($(RETPOLINE_CFLAGS),)
 endif
 endif
 
-
-ifdef CONFIG_MODVERSIONS
-objtool_o = $(@D)/.tmp_$(@F)
-else
-objtool_o = $(@)
-endif
-
 # 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
 # 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file
 # '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_obj) $(objtool_args) "$(objtool_o)";)
+	$(__objtool_obj) $(objtool_args) $@;)
 objtool_obj = $(if $(patsubst y%,, \
 	$(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
 	$(__objtool_obj))
@@ -357,34 +345,26 @@ $(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 $@ $<
 
-ifndef CONFIG_MODVERSIONS
-cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $<
-
-else
+ifdef CONFIG_MODVERSIONS
 
 ASM_PROTOTYPES := $(wildcard $(srctree)/arch/$(SRCARCH)/include/asm/asm-prototypes.h)
 
-ifeq ($(ASM_PROTOTYPES),)
-cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $<
-
-else
+ifneq ($(ASM_PROTOTYPES),)
 
 # versioning matches the C process described above, with difference that
 # we parse asm-prototypes.h C header to get function definitions.
 
-cmd_as_o_S = $(CC) $(a_flags) -c -o $(@D)/.tmp_$(@F) $<
-
 cmd_modversions_S =								\
-	if $(OBJDUMP) -h $(@D)/.tmp_$(@F) | grep -q __ksymtab; then		\
+	if $(OBJDUMP) -h $@ | grep -q __ksymtab; then				\
 		$(call cmd_gensymtypes_S,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))	\
 		    > $(@D)/.tmp_$(@F:.o=.ver);					\
 										\
-		$(LD) $(KBUILD_LDFLAGS) -r -o $@ $(@D)/.tmp_$(@F) 		\
+		$(LD) $(KBUILD_LDFLAGS) -r -o $(@D)/.tmp_$(@F) $@ 		\
 			-T $(@D)/.tmp_$(@F:.o=.ver);				\
-		rm -f $(@D)/.tmp_$(@F) $(@D)/.tmp_$(@F:.o=.ver);		\
-	else									\
 		mv -f $(@D)/.tmp_$(@F) $@;					\
+		rm -f $(@D)/.tmp_$(@F:.o=.ver);					\
 	fi;
 endif
 endif
-- 
2.7.4