linux-kernel - Re: [RFC PATCH v2 6/6] uprobes/x86: Emulate rip-relative conditional "near" jmp's

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Message-ID: <53469358.4060502@redhat.com>
Date:	Thu, 10 Apr 2014 14:49:28 +0200
From:	Denys Vlasenko <dvlasenk@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
CC:	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anton Arapov <aarapov@...hat.com>,
	David Long <dave.long@...aro.org>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	Jim Keniston <jkenisto@...ibm.com>,
	Jonathan Lebon <jlebon@...hat.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 6/6] uprobes/x86: Emulate rip-relative conditional
 "near" jmp's

On 04/09/2014 09:44 PM, Oleg Nesterov wrote:
> +	case 0x0f:
> +		if (insn->opcode.nbytes != 2)
> +			return -ENOSYS;
> +		/*
> +		 * If it is a "near" conditional jmp, OPCODE2() - 0x10 matches
> +		 * OPCODE1() of the "short" jmp which checks the same condition.
> +		 */

I propose:

/*
 * Near conditional jump opcodes: 0f 80..8f
 * Short conditional jump opcodes: 70..7f
 * Convert OPCODE2() to corresponding short jump opcode:
 */

> +		opc1 = OPCODE2(insn) - 0x10;
>  	default:

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