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Re: Hitachi djprobe mechanism
- From: Masami Hiramatsu <hiramatu at sdl dot hitachi dot co dot jp>
- To: Roland McGrath <roland at redhat dot com>
- Cc: Richard J Moore <richardj_moore at uk dot ibm dot com>,SystemTAP <systemtap at sources dot redhat dot com>, sugita at sdl dot hitachi dot co dot jp,Satoshi Oshima <soshima at redhat dot com>
- Date: Wed, 27 Jul 2005 22:01:54 +0900
- Subject: Re: Hitachi djprobe mechanism
- References: <20050726075346.F2D811809B2@magilla.sf.frob.com>
Hi, Roland
Roland McGrath wrote:
I think Kerninst is similar in effect to djprobe. both of them copy
original code to a buffer and jump to the buffer.
However I think that the most unique feature of djprobe is use of
"bypass" route to safely insert code on SMP.
I cannot find SMP safety mechanism like "bypass" in kerninst papers
yet.
If by this you mean inserting an int3 while writing the rest of the jmp
instruction and then overwriting the first byte when the rest is in place,
I recall reading about that in some kerninst paper to be sure.
Thanks a lot.
Finally, I found it in page.9 of the OSDI paper:
"Fine-Grained Dynamic Instrumentation of Commodity Operating System Kernels",
Ariel Tamches and Barton P. Miller, OSDI, Feb 1999.
Actually, it seems to describe a similar thing.
--
Masami HIRAMATSU
2nd Research Dept.
Hitachi, Ltd., Systems Development Laboratory
E-mail: hiramatu@sdl.hitachi.co.jp