linux-kernel - Re: [PATCH v2 2/5] x86/uprobes: implement x86 specific arch_uprobe_*

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Date:	Mon, 13 Aug 2012 15:24:43 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Roland McGrath <roland@...hat.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	stan_shebs@...tor.com
Subject: Re: [PATCH v2 2/5] x86/uprobes: implement x86 specific
	arch_uprobe_*_step

On 08/09, Sebastian Andrzej Siewior wrote:
>
> v1..v2: re-use auprobe->fixups for fixups

Yes, but

> @@ -46,6 +46,8 @@ struct arch_uprobe_task {
>  #ifdef CONFIG_X86_64
>  	unsigned long			saved_scratch_register;
>  #endif
> +#define UPROBE_CLEAR_TF			(1 << 0)
> +	unsigned int			restore_flags;
>  };

this patch still adds restore_flags into arch_uprobe_task.

>  static void prepare_fixups(struct arch_uprobe *auprobe, struct insn *insn)
>  {
> -	bool fix_ip = true, fix_call = false;	/* defaults */
> +	bool fix_ip = true, fix_call = false, fix_tf = false;	/* defaults */
>  	int reg;
>  
>  	insn_get_opcode(insn);	/* should be a nop */
>  
>  	switch (OPCODE1(insn)) {
> +	case 0x9d:
> +		/* popf */
> +		fix_tf = true;
> +		break;
>  	case 0xc3:		/* ret/lret */
>  	case 0xcb:
>  	case 0xc2:
> @@ -277,6 +284,8 @@ static void prepare_fixups(struct arch_uprobe *auprobe, struct insn *insn)
>  		auprobe->fixups |= UPROBE_FIX_IP;
>  	if (fix_call)
>  		auprobe->fixups |= UPROBE_FIX_CALL;
> +	if (fix_tf)
> +		auprobe->fixups |= UPROBE_TF_CHANGES;
>  }

I won't insist, but do we really need fix_tf? "case 0x9d" could simply
add UPROBE_TF_CHANGES.

Oleg.

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