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Date: Thu, 10 Apr 2014 14:49:28 +0200
From: Denys Vlasenko <dvlasenk@redhat.com>
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To: Oleg Nesterov <oleg@redhat.com>, Ingo Molnar <mingo@elte.hu>,
        Srikar Dronamraju <srikar@linux.vnet.ibm.com>
CC: Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
        Anton Arapov <aarapov@redhat.com>, David Long <dave.long@linaro.org>,
        "Frank Ch. Eigler" <fche@redhat.com>,
        Jim Keniston <jkenisto@us.ibm.com>, Jonathan Lebon <jlebon@redhat.com>,
        Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v2 6/6] uprobes/x86: Emulate rip-relative conditional
 "near" jmp's
References: <20140409194442.GA6245@redhat.com>
In-Reply-To: <20140409194442.GA6245@redhat.com>
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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: