linux-kernel - Re: Immediate values

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Message-ID: <4ABB7F58.5030508@zytor.com>
Date:	Thu, 24 Sep 2009 07:16:56 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jason Baron <jbaron@...hat.com>
CC:	Ingo Molnar <mingo@...e.hu>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>, Andi Kleen <ak@...e.de>,
	linux-kernel@...r.kernel.org
Subject: Re: Immediate values

Jason Baron wrote:
> 
> http://marc.info/?l=linux-kernel&m=125200966226921&w=2
> 
> The basic idea is that gcc, 4.5 will have support for an 'asm goto'
> construct which can refer to c code labels. Thus, we can replace a nop
> in the code stream with a 'jmp' instruction to various branch targets.
> 

Looking at the above, I'm a bit unclear for the need for a NOP5.  We 
obviously need a *total* of 5 bytes, but at least I don't seem to 
understand why we need 7 bytes per tracepoint.

	-hpa

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