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authorNathan Chancellor <natechancellor@gmail.com>2019-09-04 01:13:15 +0100
committerRussell King <rmk+kernel@armlinux.org.uk>2019-09-06 17:18:58 +0100
commit7b3948597372e5a6b314208ac320362c204b7f0f (patch)
tree14d4d0933a72d71acf2bd02f07f424cd059d9980
parent2505b9ba9c37605954c25ae581c15565c8546d86 (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>
-rw-r--r--arch/arm/Kconfig2
-rw-r--r--arch/arm/Makefile4
2 files changed, 5 insertions, 1 deletions
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index eae53c69a177..859b49d0d077 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -78,7 +78,7 @@ config ARM
select HAVE_FAST_GUP if ARM_LPAE
select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
select HAVE_FUNCTION_GRAPH_TRACER if !THUMB2_KERNEL && !CC_IS_CLANG
- 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_HW_BREAKPOINT if PERF_EVENTS && (CPU_V6 || CPU_V6K || CPU_V7)
select HAVE_IDE if PCI || ISA || PCMCIA
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)