linux-kernel - [PATCH 2/3] arm64: vdso32: lazily invoke COMPAT

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Date:   Tue, 12 Oct 2021 16:46:05 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
Cc:     llvm@...ts.linux.dev, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Lucas Henneman <henneman@...gle.com>
Subject: [PATCH 2/3] arm64: vdso32: lazily invoke COMPAT_CC

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@...nel.org>
Reported-by: Lucas Henneman <henneman@...gle.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.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