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RE: Hitachi djprobe mechanism
- From: "Keshavamurthy, Anil S" <anil dot s dot keshavamurthy at intel dot com>
- To: "Richard J Moore" <richardj_moore at uk dot ibm dot com>
- Cc: "Mathieu Desnoyers" <compudj at krystal dot dyndns dot org>, "Masami Hiramatsu" <hiramatu at sdl dot hitachi dot co dot jp>, "Karim Yaghmour" <karim at opersys dot com>, "Masami Hiramatsu" <masami dot hiramatsu at gmail dot com>, <michel dot dagenais at polymtl dot ca>, "Roland McGrath" <roland at redhat dot com>, "Satoshi Oshima" <soshima at redhat dot com>, <sugita at sdl dot hitachi dot co dot jp>, <systemtap at sources dot redhat dot com>
- Date: Thu, 28 Jul 2005 17:17:24 -0700
- Subject: RE: Hitachi djprobe mechanism
>
>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 -
>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
>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
with having to worry about all the other issues which we have discussed
earlier.
The only _limitations_ here is that djprobe can only be placed if there
is a static hook as mentioned above.
-thanks,
Anil