linux-kernel - Re: [PATCH v9 3.2 1/9] uprobes: Install and remove breakpoints.

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Date:	Thu, 26 Jan 2012 22:45:37 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-mm <linux-mm@...ck.org>, Andi Kleen <andi@...stfloor.org>,
	Christoph Hellwig <hch@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Roland McGrath <roland@...k.frob.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Anton Arapov <anton@...hat.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: [PATCH v9 3.2 1/9] uprobes: Install and remove breakpoints.

(2012/01/10 20:48), Srikar Dronamraju wrote:
> +static void handle_riprel_insn(struct mm_struct *mm, struct uprobe *uprobe,
> +							struct insn *insn)
> +{
> +	u8 *cursor;
> +	u8 reg;
> +
> +	if (mm->context.ia32_compat)
> +		return;
> +
> +	uprobe->arch_info.rip_rela_target_address = 0x0;
> +	if (!insn_rip_relative(insn))
> +		return;
> +
> +	/*
> +	 * Point cursor at the modrm byte.  The next 4 bytes are the
> +	 * displacement.  Beyond the displacement, for some instructions,
> +	 * is the immediate operand.
> +	 */
> +	cursor = uprobe->insn + insn->prefixes.nbytes
> +			+ insn->rex_prefix.nbytes + insn->opcode.nbytes;

FYI, insn.h already provide a macro for this purpose.
You can write this as below;

	cursor = uprobe->insn + insn_offset_modrm(insn);

Thank you,

-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com
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