linux-kernel - Re: [PATCH] x86: Introduce REX prefix helper for kprobes

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Date:	Sun, 30 Dec 2007 03:01:38 -0500
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Harvey Harrison <harvey.harrison@...il.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jim Keniston <jkenisto@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86: Introduce REX prefix helper for kprobes

Hi,

H. Peter Anvin wrote:
>> Could you use a macro same as the stack_addr() macro, like as below?
>>
>> #defile is_REX_prefix(insn) ((insn & 0xf0) == 0x40))
>>
>> This is just a bit checker, so I think a macro is better to do that.
>>
> 
> Why is a macro better than an inline, and why the odd mIXed case?

I thought we can use macro because it just check a bit mask.
And if we use this as a macro, it will be defined in #ifdef block at
the top of kprobes.c. It is simple in this case.
I know the inline is better than the macro, it can check the type of
arguments.
If you would like to use inline, how about this?

---
(in case of CONFIG_X86_64)
static inline int is_rex_prefix(int op)
{
	return ((op & 0xf0) == 0x40);
}

(in case of CONFIG_X86_32)
#define is_rex_prefix(op) (0)
---

About the name, I just used the previous inline function name.

Thank you,

> 
> 	-hpa

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@...hat.com, masami.hiramatsu.pt@...achi.com

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