Building the Linux kernel with Clang and LLVM
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From: Nick Desaulniers <ndesaulniers@google.com>
To: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>
Cc: llvm@lists.linux.dev, linux-kernel@vger.kernel.org,
	 linux-arm-kernel@lists.infradead.org,
	 Vincenzo Frascino <vincenzo.frascino@arm.com>,
	Nick Desaulniers <ndesaulniers@google.com>,
	 Masahiro Yamada <masahiroy@kernel.org>,
	Lucas Henneman <henneman@google.com>
Subject: [PATCH 2/3] arm64: vdso32: lazily invoke COMPAT_CC
Date: Tue, 12 Oct 2021 16:46:05 -0700	[thread overview]
Message-ID: <20211012234606.91717-3-ndesaulniers@google.com> (raw)
In-Reply-To: <20211012234606.91717-1-ndesaulniers@google.com>

When running the following command without arm-linux-gnueabi-gcc in
one's $PATH, the following warning is observed:

$ ARCH=arm64 CROSS_COMPILE_COMPAT=arm-linux-gnueabi- make -j72 LLVM=1 mrproper
make[1]: arm-linux-gnueabi-gcc: No such file or directory

This is because KCONFIG is not run for mrproper, so CONFIG_CC_IS_CLANG
is not set, and we end up eagerly evaluating various variables that try
to invoke CC_COMPAT.

This is a similar problem to what was observed in
commit 3ec8a5b33dea ("kbuild: do not export LDFLAGS_vmlinux")

Cc: Masahiro Yamada <masahiroy@kernel.org>
Reported-by: Lucas Henneman <henneman@google.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
 arch/arm64/kernel/vdso32/Makefile | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile
index 89299a26638b..d24b12318f4c 100644
--- a/arch/arm64/kernel/vdso32/Makefile
+++ b/arch/arm64/kernel/vdso32/Makefile
@@ -38,12 +38,12 @@ cc32-disable-warning = $(call try-run,\
 # As a result we set our own flags here.
 
 # KBUILD_CPPFLAGS and NOSTDINC_FLAGS from top-level Makefile
-VDSO_CPPFLAGS := -DBUILD_VDSO -D__KERNEL__ -nostdinc -isystem $(shell $(CC_COMPAT) -print-file-name=include)
+VDSO_CPPFLAGS = -DBUILD_VDSO -D__KERNEL__ -nostdinc -isystem $(shell $(CC_COMPAT) -print-file-name=include)
 VDSO_CPPFLAGS += $(LINUXINCLUDE)
 
 # Common C and assembly flags
 # From top-level Makefile
-VDSO_CAFLAGS := $(VDSO_CPPFLAGS)
+VDSO_CAFLAGS = $(VDSO_CPPFLAGS)
 ifneq ($(shell $(CC_COMPAT) --version 2>&1 | head -n 1 | grep clang),)
 VDSO_CAFLAGS += --target=$(notdir $(CROSS_COMPILE_COMPAT:%-=%))
 endif
@@ -73,7 +73,7 @@ VDSO_CAFLAGS += -DDISABLE_BRANCH_PROFILING
 VDSO_CAFLAGS += $(call cc32-option,-march=armv8-a -D__LINUX_ARM_ARCH__=8,\
                                    -march=armv7-a -D__LINUX_ARM_ARCH__=7)
 
-VDSO_CFLAGS := $(VDSO_CAFLAGS)
+VDSO_CFLAGS = $(VDSO_CAFLAGS)
 VDSO_CFLAGS += -DENABLE_COMPAT_VDSO=1
 # KBUILD_CFLAGS from top-level Makefile
 VDSO_CFLAGS += -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
@@ -108,7 +108,7 @@ else
 VDSO_CFLAGS += -marm
 endif
 
-VDSO_AFLAGS := $(VDSO_CAFLAGS)
+VDSO_AFLAGS = $(VDSO_CAFLAGS)
 VDSO_AFLAGS += -D__ASSEMBLY__
 
 # From arm vDSO Makefile
-- 
2.33.0.882.g93a45727a2-goog


  parent reply	other threads:[~2021-10-12 23:46 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-12 23:46 [PATCH 0/3] compat vdso cleanups Nick Desaulniers
2021-10-12 23:46 ` [PATCH 1/3] arm64: vdso32: drop the test for dmb ishld Nick Desaulniers
2021-10-13  7:55   ` Arnd Bergmann
2021-10-13 17:24   ` Christian Biesinger
2021-10-12 23:46 ` Nick Desaulniers [this message]
2021-10-13  3:02   ` [PATCH 2/3] arm64: vdso32: lazily invoke COMPAT_CC Masahiro Yamada
2021-10-14 20:59     ` Nick Desaulniers
2021-10-16 14:19       ` Masahiro Yamada
2021-10-18 20:34         ` Nick Desaulniers
2021-10-12 23:46 ` [PATCH 3/3] arm64: vdso32: require CROSS_COMPILE_COMPAT for gcc+bfd Nick Desaulniers
2021-10-18 22:58   ` Nathan Chancellor

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