linux-kernel - Re: [PATCH 2/2] jump labels/x86: Use etiher 5 byte or 2 byte jumps

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Message-ID: <4F182F81.2020200@zytor.com>
Date:	Thu, 19 Jan 2012 06:58:09 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jason Baron <jbaron@...hat.com>
Subject: Re: [PATCH 2/2] jump labels/x86: Use etiher 5 byte or 2 byte jumps

On 01/19/2012 06:56 AM, Steven Rostedt wrote:
>>
>> Is it possible that the compiler choose a jump that is not 2 or 5-byte ?
>> e.g. a jmp rel16 (e9 opcode) on 32-bit x86, or any of the other
>
> Isn't e9 the 5 byte opcode?
>

I think Mathieu is thinking of 66 e9 rel16 (66 e9 xx xx) which isn't 
used by the compiler since it truncates the result to 16 bits.

	-hpa
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