Re: arch/x86//kernel/ftrace.c:35:3: error: #error The following combination is not supported: ((compiler missing -mfentry) || (CONFIG_X86_32 and !CONFIG_DYNAMIC_FTRACE)) && CONFIG_FUNCTION_GRAPH_TRACER && CONFIG_CC_OPTIMIZE_FOR_SIZE

From: Andi Kleen
Date: Tue Apr 18 2017 - 14:53:07 EST

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In reply to: Josh Poimboeuf: "Re: arch/x86//kernel/ftrace.c:35:3: error: #error The following combination is not supported: ((compiler missing -mfentry) || (CONFIG_X86_32 and !CONFIG_DYNAMIC_FTRACE)) && CONFIG_FUNCTION_GRAPH_TRACER && CONFIG_CC_OPTIMIZE_FOR_SIZE"
Next in thread: Josh Poimboeuf: "Re: arch/x86//kernel/ftrace.c:35:3: error: #error The following combination is not supported: ((compiler missing -mfentry) || (CONFIG_X86_32 and !CONFIG_DYNAMIC_FTRACE)) && CONFIG_FUNCTION_GRAPH_TRACER && CONFIG_CC_OPTIMIZE_FOR_SIZE"
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Josh Poimboeuf <jpoimboe@xxxxxxxxxx> writes:
>
> The error is working as designed. gcc < 4.6.0 doesn't have -mfentry, so
> it fails the above check on x86. Can you add a skip rule? It should
> skip building the following case:
>
> x86 && ((gcc < 4.6.0) || (CONFIG_X86_32 and !CONFIG_DYNAMIC_FTRACE))
> && CONFIG_FUNCTION_GRAPH_TRACER && CONFIG_CC_OPTIMIZE_FOR_SIZE

This will also break everyone's randconfig builds. The better way
would be to check this in the Makefile and disable one of the options

-Andi