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Re: kprobes trampoline_p registration
- From: Masami Hiramatsu <hiramatu at sdl dot hitachi dot co dot jp>
- To: systemtap at sources dot redhat dot com
- Date: Tue, 13 Jun 2006 16:38:35 +0900
- Subject: Re: kprobes trampoline_p registration
- References: <20060612093007.GA29431@localhost.localdomain>
Hi,
That change is to reduce the overhead of kretprobe. The original
implementation of the kretprobe uses 2 kprobes. On i386 arch,
2nd kprobe can be replaced by assembly code which works much faster
than kprobe.
You can see how it works in detail here:
http://sources.redhat.com/ml/systemtap/2006-q1/msg00342.html
And our team is currently porting this kind of improvements to
IA64 and x86-64.
Best regards,
Mike Grundy wrote:
> Hi - I noticed in 2.6.17-rc6 in the i386 kprobes.c the registration of the
> trampoline probe in arch_init_kprobes was removed. It looks like that pile of
> assembly in kretprobe_trampoline_holder does the clean up instead of using the
> regular mechanisms. Any particular reason for this? Should the other arches
> consider a similar mechanism?
--
Masami HIRAMATSU
2nd Research Dept.
Hitachi, Ltd., Systems Development Laboratory
E-mail: hiramatu@sdl.hitachi.co.jp