From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 25503 invoked by alias); 29 Jul 2005 00:18:51 -0000 Mailing-List: contact systemtap-help@sources.redhat.com; run by ezmlm Precedence: bulk List-Subscribe: List-Post: List-Help: , Sender: systemtap-owner@sources.redhat.com Received: (qmail 25025 invoked by uid 22791); 29 Jul 2005 00:18:33 -0000 X-MimeOLE: Produced By Microsoft Exchange V6.5.7226.0 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Subject: RE: Hitachi djprobe mechanism Date: Fri, 29 Jul 2005 00:18:00 -0000 Message-ID: <44BDAFB888F59F408FAE3CC35AB4704101E98465@orsmsx409> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: Hitachi djprobe mechanism Thread-Index: AcWTz4l9psipWAdORBq7V5MhlnEVCwAAUQmA From: "Keshavamurthy, Anil S" To: "Richard J Moore" Cc: "Mathieu Desnoyers" , "Masami Hiramatsu" , "Karim Yaghmour" , "Masami Hiramatsu" , , "Roland McGrath" , "Satoshi Oshima" , , X-OriginalArrivalTime: 29 Jul 2005 00:17:26.0023 (UTC) FILETIME=[E5F2B170:01C593D2] X-Scanned-By: MIMEDefang 2.44 X-SW-Source: 2005-q3/txt/msg00152.txt.bz2 =20 > >There are more efficient ways of implementing a jmp type hook - see the >kernel hooks package, where we evloved past this string of 5 no-ops >implementation Here we moved an immediate value - 1 byte -=20 >into a reg and >jumped on the reg being non-zero. To spring the hook we stored the one >immediate byte in the mov instruction. This technique works=20 >quite well on >IA64 where one can use a predicate register for the same purpose. Yup, I agree with you and this seems to the correct way to support djprobe=20 with having to worry about all the other issues which we have discussed earlier.=20 The only _limitations_ here is that djprobe can only be placed if there is a static hook as mentioned above. -thanks, Anil