From 4bd3f510b9373c2ecac6596fc6b8e8ce61d5c7ff Mon Sep 17 00:00:00 2001 From: Nathan Chancellor Date: Wed, 4 Dec 2019 14:50:28 -0800 Subject: [PATCH] BACKPORT: ARM: 8905/1: Emit __gnu_mcount_nc when using Clang 10.0.0 or newer commit b0fe66cf095016e0b238374c10ae366e1f087d11 upstream. 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 Reviewed-by: Nick Desaulniers Reviewed-by: Stefan Agner Signed-off-by: Nathan Chancellor Signed-off-by: Russell King Bug: 145525910 [nd: Kconfig change differs due to missing f00790aaf2e2] Change-Id: I280bd7c0422c68284ed31e2134ccef8997832737 Signed-off-by: Nick Desaulniers --- arch/arm/Kconfig | 2 +- arch/arm/Makefile | 4 ++++ 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 185e552f1461..2c41a9417ec6 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -69,7 +69,7 @@ config ARM select HAVE_EXIT_THREAD select HAVE_FTRACE_MCOUNT_RECORD if (!XIP_KERNEL) select HAVE_FUNCTION_GRAPH_TRACER if (!THUMB2_KERNEL) - select HAVE_FUNCTION_TRACER if (!XIP_KERNEL) + select HAVE_FUNCTION_TRACER if (!XIP_KERNEL) && (CC_IS_GCC || CLANG_VERSION >= 100000) select HAVE_GCC_PLUGINS select HAVE_GENERIC_DMA_COHERENT select HAVE_HW_BREAKPOINT if (PERF_EVENTS && (CPU_V6 || CPU_V6K || CPU_V7)) diff --git a/arch/arm/Makefile b/arch/arm/Makefile index de3405045edb..62c789dc2222 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)