linux-kernel - Re: [PATCH 2/2 v3] x86: make jump

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Date:	Fri, 12 Jul 2013 14:44:24 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Jason Baron <jbaron@...mai.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Borislav Petkov <bp@...en8.de>, Joe Perches <joe@...ches.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2 v3] x86: make jump_label use int3-based patching

(2013/07/12 5:26), Jiri Kosina wrote:
> Make jump labels use text_poke_bp() for text patching instead of 
> text_poke_smp(), avoiding the need for stop_machine().
> 
> Signed-off-by: Jiri Kosina <jkosina@...e.cz>
> ---
> Changes:
> 
> - unchanged since v1, patch 1/2 is the one being updated
> 
>  arch/x86/kernel/jump_label.c |   16 ++++++++++++++--
>  1 files changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
> index 2889b3d..460f5d9 100644
> --- a/arch/x86/kernel/jump_label.c
> +++ b/arch/x86/kernel/jump_label.c
> @@ -37,7 +37,19 @@ static void __jump_label_transform(struct jump_entry *entry,
>  	} else
>  		memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE);
>  
> -	(*poker)((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE);
> +	/*
> +	 * Make text_poke_bp() a default fallback poker.
> +	 *
> +	 * At the time the change is being done, just ignore whether we
> +	 * are doing nop -> jump or jump -> nop transition, and assume
> +	 * always nop being the 'currently valid' instruction
> +	 *
> +	 */
> +	if (poker)
> +		(*poker)((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE);
> +	else
> +		text_poke_bp((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE,
> +			     (void *)entry->code + JUMP_LABEL_NOP_SIZE);

BTW, if the poker is NULL or text_poke_early, I think it doesn't need to
pass it to __jump_label_transform, does it?

Thank you,
-- 
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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