linux-kernel - [PATCH 1/2] kbuild: include scripts/Makefile.* only when relevant CONFIG is enabled

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Message-Id: <20200801150050.767038-1-masahiroy@kernel.org>
Date:   Sun,  2 Aug 2020 00:00:49 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     linux-kbuild@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        kasan-dev@...glegroups.com
Subject: [PATCH 1/2] kbuild: include scripts/Makefile.* only when relevant CONFIG is enabled

Currently, the top Makefile includes all of scripts/Makefile.<feature>
even if the associated CONFIG option is disabled.

Do not include unneeded Makefiles in order to slightly optimize the
parse stage.

Include $(include-y), and ignore $(include-).

Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
---

 Makefile               | 16 +++++++++-------
 scripts/Makefile.kcov  |  4 ----
 scripts/Makefile.kcsan |  4 ----
 scripts/Makefile.ubsan |  3 ---
 4 files changed, 9 insertions(+), 18 deletions(-)

diff --git a/Makefile b/Makefile
index ebf4d3ce492c..483456d5dd3e 100644
--- a/Makefile
+++ b/Makefile
@@ -745,9 +745,6 @@ endif
 KBUILD_CFLAGS	+= $(call cc-option,--param=allow-store-data-races=0)
 KBUILD_CFLAGS	+= $(call cc-option,-fno-allow-store-data-races)
 
-include scripts/Makefile.kcov
-include scripts/Makefile.gcc-plugins
-
 ifdef CONFIG_READABLE_ASM
 # Disable optimizations that make assembler listings hard to read.
 # reorder blocks reorders the control in the function
@@ -948,10 +945,15 @@ ifdef CONFIG_RETPOLINE
 KBUILD_CFLAGS += $(call cc-option,-fcf-protection=none)
 endif
 
-include scripts/Makefile.kasan
-include scripts/Makefile.extrawarn
-include scripts/Makefile.ubsan
-include scripts/Makefile.kcsan
+# include additional Makefiles when needed
+include-y			:= scripts/Makefile.extrawarn
+include-$(CONFIG_KASAN)		+= scripts/Makefile.kasan
+include-$(CONFIG_KCSAN)		+= scripts/Makefile.kcsan
+include-$(CONFIG_UBSAN)		+= scripts/Makefile.ubsan
+include-$(CONFIG_KCOV)		+= scripts/Makefile.kcov
+include-$(CONFIG_GCC_PLUGINS)	+= scripts/Makefile.gcc-plugins
+
+include $(addprefix $(srctree)/, $(include-y))
 
 # Add user supplied CPPFLAGS, AFLAGS and CFLAGS as the last assignments
 KBUILD_CPPFLAGS += $(KCPPFLAGS)
diff --git a/scripts/Makefile.kcov b/scripts/Makefile.kcov
index 52b113302443..67e8cfe3474b 100644
--- a/scripts/Makefile.kcov
+++ b/scripts/Makefile.kcov
@@ -1,10 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0-only
-ifdef CONFIG_KCOV
-
 kcov-flags-$(CONFIG_CC_HAS_SANCOV_TRACE_PC)	+= -fsanitize-coverage=trace-pc
 kcov-flags-$(CONFIG_KCOV_ENABLE_COMPARISONS)	+= -fsanitize-coverage=trace-cmp
 kcov-flags-$(CONFIG_GCC_PLUGIN_SANCOV)		+= -fplugin=$(objtree)/scripts/gcc-plugins/sancov_plugin.so
 
 export CFLAGS_KCOV := $(kcov-flags-y)
-
-endif
diff --git a/scripts/Makefile.kcsan b/scripts/Makefile.kcsan
index bd4da1af5953..2b0743e6566e 100644
--- a/scripts/Makefile.kcsan
+++ b/scripts/Makefile.kcsan
@@ -1,6 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0
-ifdef CONFIG_KCSAN
-
 # GCC and Clang accept backend options differently. Do not wrap in cc-option,
 # because Clang accepts "--param" even if it is unused.
 ifdef CONFIG_CC_IS_CLANG
@@ -15,5 +13,3 @@ CFLAGS_KCSAN := -fsanitize=thread \
 	$(call cc-option,$(call cc-param,tsan-instrument-func-entry-exit=0) -fno-optimize-sibling-calls) \
 	$(call cc-option,$(call cc-param,tsan-instrument-read-before-write=1)) \
 	$(call cc-param,tsan-distinguish-volatile=1)
-
-endif # CONFIG_KCSAN
diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan
index 5b15bc425ec9..27348029b2b8 100644
--- a/scripts/Makefile.ubsan
+++ b/scripts/Makefile.ubsan
@@ -1,6 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0
-ifdef CONFIG_UBSAN
-
 ifdef CONFIG_UBSAN_ALIGNMENT
       CFLAGS_UBSAN += $(call cc-option, -fsanitize=alignment)
 endif
@@ -26,4 +24,3 @@ endif
       # -fsanitize=* options makes GCC less smart than usual and
       # increase number of 'maybe-uninitialized false-positives
       CFLAGS_UBSAN += $(call cc-option, -Wno-maybe-uninitialized)
-endif
-- 
2.25.1