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

From: H. Peter Anvin
Date: Sun Dec 30 2007 - 02:28:41 EST


Masami Hiramatsu wrote:
> Hi Harvey,
>
> Harvey Harrison wrote:
>> Fold some small ifdefs into a helper function.
>>
>> Signed-off-by: Harvey Harrison <harvey.harrison@xxxxxxxxx>
>> ---
>> Masami, Ingo, I had this left in some unsent kprobes unification
>> work. Depends on your tastes, but does reduce ifdefs and is a bit
>> better about self-documenting the REX prefix on X86_64.
>
> Basically, I think it is good idea.
> 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?

-hpa
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