From: Masahiro Yamada <yamada.masahiro@socionext.com>
To: linux-kbuild@vger.kernel.org
Cc: Nicholas Piggin <npiggin@gmail.com>,
Masahiro Yamada <yamada.masahiro@socionext.com>,
Michal Marek <michal.lkml@markovi.net>,
linux-kernel@vger.kernel.org
Subject: [PATCH] kbuild: test dead code/data elimination support in Kconfig
Date: Wed, 22 Aug 2018 22:51:09 +0900 [thread overview]
Message-ID: <1534945869-17117-1-git-send-email-yamada.masahiro@socionext.com> (raw)
This config option should be enabled only when both the compiler and
the linker support necessary flags. Add proper dependencies to Kconfig.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---
Makefile | 8 ++------
init/Kconfig | 2 ++
2 files changed, 4 insertions(+), 6 deletions(-)
diff --git a/Makefile b/Makefile
index 1289a01..2e2b009 100644
--- a/Makefile
+++ b/Makefile
@@ -790,8 +790,8 @@ KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once)
endif
ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
-KBUILD_CFLAGS_KERNEL += $(call cc-option,-ffunction-sections,)
-KBUILD_CFLAGS_KERNEL += $(call cc-option,-fdata-sections,)
+KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections
+LDFLAGS_vmlinux += --gc-sections
endif
# arch Makefile may override CC so keep this after arch Makefile is included
@@ -857,10 +857,6 @@ LDFLAGS_BUILD_ID := $(call ld-option, --build-id)
KBUILD_LDFLAGS_MODULE += $(LDFLAGS_BUILD_ID)
LDFLAGS_vmlinux += $(LDFLAGS_BUILD_ID)
-ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
-LDFLAGS_vmlinux += $(call ld-option, --gc-sections,)
-endif
-
ifeq ($(CONFIG_STRIP_ASM_SYMS),y)
LDFLAGS_vmlinux += $(call ld-option, -X,)
endif
diff --git a/init/Kconfig b/init/Kconfig
index 9bd50ba..21b8559 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1085,6 +1085,8 @@ config LD_DEAD_CODE_DATA_ELIMINATION
bool "Dead code and data elimination (EXPERIMENTAL)"
depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
depends on EXPERT
+ depends on $(cc-option,-ffunction-sections -fdata-sections)
+ depends on $(ld-option,--gc-sections)
help
Enable this if you want to do dead code and data elimination with
the linker by compiling with -ffunction-sections -fdata-sections,
--
2.7.4
reply other threads:[~2018-08-22 13:51 UTC|newest]
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