From: Masahiro Yamada <yamada.masahiro@socionext.com>
To: linux-kbuild@vger.kernel.org
Cc: Stephen Boyd <swboyd@chromium.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Nathan Chancellor <natechancellor@gmail.com>,
Masahiro Yamada <yamada.masahiro@socionext.com>,
stable@vger.kernel.org, Michal Marek <michal.lkml@markovi.net>,
clang-built-linux@googlegroups.com, linux-kernel@vger.kernel.org
Subject: [PATCH] kbuild: initialize CLANG_FLAGS correctly in the top Makefile
Date: Mon, 29 Jul 2019 18:15:17 +0900 [thread overview]
Message-ID: <20190729091517.5334-1-yamada.masahiro@socionext.com> (raw)
CLANG_FLAGS is initialized by the following line:
CLANG_FLAGS := --target=$(notdir $(CROSS_COMPILE:%-=%))
..., which is run only when CROSS_COMPILE is set.
Some build targets (bindeb-pkg etc.) recurse to the top Makefile.
When you build the kernel with Clang but without CROSS_COMPILE,
the same compiler flags such as -no-integrated-as are accumulated
into CLANG_FLAGS.
If you run 'make CC=clang' and then 'make CC=clang bindeb-pkg',
Kbuild will recompile everything needlessly due to the build command
change.
Fix this by correctly initializing CLANG_FLAGS.
Fixes: 238bcbc4e07f ("kbuild: consolidate Clang compiler flags")
Cc: <stable@vger.kernel.org> # v4.20+
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---
Makefile | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/Makefile b/Makefile
index fa0fbe7851ea..5ee6f6889869 100644
--- a/Makefile
+++ b/Makefile
@@ -472,6 +472,7 @@ KBUILD_CFLAGS_MODULE := -DMODULE
KBUILD_LDFLAGS_MODULE := -T $(srctree)/scripts/module-common.lds
KBUILD_LDFLAGS :=
GCC_PLUGINS_CFLAGS :=
+CLANG_FLAGS :=
export ARCH SRCARCH CONFIG_SHELL HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE AS LD CC
export CPP AR NM STRIP OBJCOPY OBJDUMP PAHOLE KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS
@@ -519,7 +520,7 @@ endif
ifneq ($(shell $(CC) --version 2>&1 | head -n 1 | grep clang),)
ifneq ($(CROSS_COMPILE),)
-CLANG_FLAGS := --target=$(notdir $(CROSS_COMPILE:%-=%))
+CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%))
GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit))
CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)
GCC_TOOLCHAIN := $(realpath $(GCC_TOOLCHAIN_DIR)/..)
--
2.17.1
next reply other threads:[~2019-07-29 9:16 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-29 9:15 Masahiro Yamada [this message]
2019-07-29 9:38 ` [PATCH] kbuild: initialize CLANG_FLAGS correctly in the top Makefile Masahiro Yamada
2019-07-29 16:04 ` Nathan Chancellor
2019-07-29 16:21 ` Nick Desaulniers
2019-07-30 16:45 ` Masahiro Yamada
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