linux-kernel - Re: [PATCH -tip 3/6 V4.1] x86: instruction decorder API

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Date:	Thu, 23 Apr 2009 23:53:28 -0400
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Jim Keniston <jkenisto@...ibm.com>
CC:	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Andi Kleen <andi@...stfloor.org>, kvm@...r.kernel.org,
	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	systemtap-ml <systemtap@...rces.redhat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Vegard Nossum <vegard.nossum@...il.com>,
	Avi Kivity <avi@...hat.com>, Roland McGrath <roland@...hat.com>
Subject: Re: [PATCH -tip 3/6 V4.1] x86: instruction decorder API

Jim Keniston wrote:
> On Thu, 2009-04-23 at 13:29 -0400, Masami Hiramatsu wrote:
> ...
>> Hmm, maybe, parser can handle "(extra_info)" as a solid keyword.
>> so let's define actual format.
>>
>> <opcode maps>
>> Table: table-name
>> Referrer: escamed-name
>> opcode: mnemonic|Grp [operand1[,operand2...]] [(extra1)[,(extra2)...] [| 2nd-mnemonic ...]

This should be:
opcode: mnemonic|GrpXXX ...

>> opcode: ESC # escaped-name

This should be
opcode: escape # escaped-name
because distinguishing from x87 ESC ops.

>>
>> <group maps>
>> reg: mnemonic ...
> 
> For some instruction groups -- e.g., Groups 12, 13, 14 -- the
> instruction prefix (66, f2, f3) and the reg field both affect the
> instruction type.  And for some x87 instructions, the value of the modrm
> byte's rm field also affects the instruction type.  (For others, rm just
> selects among the st(0)..st(7) registers, as one might expect.)

Sure, I updated the format. There are some special cases,

(1) instructions which are switched by 64bit mode
40: INC eAX (i64) | REX (o64)

(2) instructions which are switched by the last prefix
13: movlps Mq,Vq | movlpd Mq,Vq (66)

(3) group instructions which are switched by modr/m
0: SGDT Ms | VMCALL (11B),(001) | VMLAUNCH (11B),(010) | VMRESUME (11B),(011) | VMXOFF (11B),(100)


> 
> Of course, that's all about floating-point instructions, which are of
> more interest to uprobes than kprobes. 

Hmm, x87 instructions may need to have some special format...

Thank you,

-- 
Masami Hiramatsu

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

e-mail: mhiramat@...hat.com

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