linux-kernel - Re: [PATCH] riscv/ftrace: Export _mcount when FUNCTION_GRAPH

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Date:   Tue, 5 Jun 2018 09:12:29 +0800
From:   Alan Kao <alankao@...estech.com>
To:     Palmer Dabbelt <palmer@...ive.com>
CC:     <linux-riscv@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        Greentime Hu <greentime@...estech.com>,
        Zong Li <zong@...estech.com>
Subject: Re: [PATCH] riscv/ftrace: Export _mcount when FUNCTION_GRAPH_TRACER
 isn't set

Hi Palmer,

Thanks for the refining work! But a small correction here:

On Mon, Jun 04, 2018 at 01:30:28PM -0700, Palmer Dabbelt wrote:
> From: Alan Kao <alankao@...estech.com>
> 
> The EXPORT_SYMBOL(_mcount) for RISC-V ended up inside a
> CONFIG_FUNCTION_GRAPH_TRACER ifdef.  If you enable modules without
> enabling CONFIG_FUNCTION_GRAPH_TRACER then you'll get a build error
> without this patch because the modules won't be able to find _mcount.

the export was inside a CONFIG_DYNAMIC_FTRACE section instead of
CONFIG_FUNCTION_GRAPH_TRACER.

> The new behavior is to export _mcount whenever CONFIG_FUNCTION_TRACER is
> defined.  This matches what every other architecture is doing.

Also, this patch is just a workaround and there are still issues in bringing
up ftrace for modules.  For details, please check previous emails between
Steve and me.

Thanks again for this better commit message.
Alan Kao

> 
> Signed-off-by: Alan Kao <alankao@...estech.com>
> Cc: Greentime Hu <greentime@...estech.com>
> Cc: Zong Li <zong@...estech.com>
> Signed-off-by: Palmer Dabbelt <palmer@...ive.com>
> ---
>  arch/riscv/kernel/mcount.S | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/kernel/mcount.S b/arch/riscv/kernel/mcount.S
> index ce9bdc57a2a1..5721624886a1 100644
> --- a/arch/riscv/kernel/mcount.S
> +++ b/arch/riscv/kernel/mcount.S
> @@ -126,5 +126,5 @@ do_trace:
>  	RESTORE_ABI_STATE
>  	ret
>  ENDPROC(_mcount)
> -EXPORT_SYMBOL(_mcount)
>  #endif
> +EXPORT_SYMBOL(_mcount)
> -- 
> 2.16.4
>