linux-kernel - Re: [PATCH 3/3] powerpc/mm: Implement CONFIG_DEBUG

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Date:   Thu, 20 Apr 2017 00:01:39 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Christophe Leroy <christophe.leroy@....fr>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Scott Wood <oss@...error.net>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 3/3] powerpc/mm: Implement CONFIG_DEBUG_RODATA on PPC32

Christophe Leroy <christophe.leroy@....fr> writes:

> diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
> index 32509de6ce4c..4af81fb23653 100644
> --- a/arch/powerpc/kernel/ftrace.c
> +++ b/arch/powerpc/kernel/ftrace.c
> @@ -526,7 +526,9 @@ void ftrace_replace_code(int enable)
>   */
>  void arch_ftrace_update_code(int command)
>  {
> +	set_kernel_text_rw();
>  	ftrace_modify_all_code(command);
> +	set_kernel_text_ro();
>  }
  
I'm not sure that's the right place for that.

If you look at other arches they hook into ftrace_modify_code(), where
you have the address that's being modified.

cheers