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authorNathan Chancellor <natechancellor@gmail.com>2019-09-04 01:13:15 +0100
committerRussell King <rmk+kernel@armlinux.org.uk>2019-09-10 15:22:57 +0100
commitb0fe66cf095016e0b238374c10ae366e1f087d11 (patch)
tree14d4d0933a72d71acf2bd02f07f424cd059d9980 /arch/arm/Makefile
parent1d31999cf04c21709f72ceb17e65b54a401330da (diff)
ARM: 8905/1: Emit __gnu_mcount_nc when using Clang 10.0.0 or newer
Currently, multi_v7_defconfig + CONFIG_FUNCTION_TRACER fails to build with clang: arm-linux-gnueabi-ld: kernel/softirq.o: in function `_local_bh_enable': softirq.c:(.text+0x504): undefined reference to `mcount' arm-linux-gnueabi-ld: kernel/softirq.o: in function `__local_bh_enable_ip': softirq.c:(.text+0x58c): undefined reference to `mcount' arm-linux-gnueabi-ld: kernel/softirq.o: in function `do_softirq': softirq.c:(.text+0x6c8): undefined reference to `mcount' arm-linux-gnueabi-ld: kernel/softirq.o: in function `irq_enter': softirq.c:(.text+0x75c): undefined reference to `mcount' arm-linux-gnueabi-ld: kernel/softirq.o: in function `irq_exit': softirq.c:(.text+0x840): undefined reference to `mcount' arm-linux-gnueabi-ld: kernel/softirq.o:softirq.c:(.text+0xa50): more undefined references to `mcount' follow clang can emit a working mcount symbol, __gnu_mcount_nc, when '-meabi gnu' is passed to it. Until r369147 in LLVM, this was broken and caused the kernel not to boot with '-pg' because the calling convention was not correct. Always build with '-meabi gnu' when using clang but ensure that '-pg' (which is added with CONFIG_FUNCTION_TRACER and its prereq CONFIG_HAVE_FUNCTION_TRACER) cannot be added with it unless this is fixed (which means using clang 10.0.0 and newer). Link: https://github.com/ClangBuiltLinux/linux/issues/35 Link: https://bugs.llvm.org/show_bug.cgi?id=33845 Link: https://github.com/llvm/llvm-project/commit/16fa8b09702378bacfa3d07081afe6b353b99e60 Reviewed-by: Matthias Kaehlcke <mka@chromium.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Stefan Agner <stefan@agner.ch> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Diffstat (limited to 'arch/arm/Makefile')
-rw-r--r--arch/arm/Makefile4
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 977f4e66f145..d6273b660629 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -115,6 +115,10 @@ ifeq ($(CONFIG_ARM_UNWIND),y)
CFLAGS_ABI +=-funwind-tables
endif
+ifeq ($(CONFIG_CC_IS_CLANG),y)
+CFLAGS_ABI += -meabi gnu
+endif
+
# Accept old syntax despite ".syntax unified"
AFLAGS_NOWARN :=$(call as-option,-Wa$(comma)-mno-warn-deprecated,-Wa$(comma)-W)