Clang needs "-meabi gnu" flag to emit calls to "__gnu_mcount_nc". Otherwise, it inserts calls to undefined "mcount".
kernel/softirq.o: In function `_local_bh_enable': ... undefined reference to `mcount' "-meabi gnu" resolves link failures. However, Clang does not implement calls to "__gnu_mcount_nc" correctly. It does not save the link register on the stack, which corrupts the stack. The resulting kernel does not boot. Disable FUNCTION_TRACER support when building with Clang. Link: https://github.com/ClangBuiltLinux/linux/issues/35 Suggested-by: Stefan Agner <ste...@agner.ch> Signed-off-by: Tri Vo <tr...@android.com> --- arch/arm/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 8869742a85df..7a1804392795 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -75,7 +75,7 @@ config ARM select HAVE_EXIT_THREAD 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_CLANG select HAVE_GCC_PLUGINS select HAVE_HW_BREAKPOINT if PERF_EVENTS && (CPU_V6 || CPU_V6K || CPU_V7) select HAVE_IDE if PCI || ISA || PCMCIA -- 2.21.0.1020.gf2820cf01a-goog
