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Re: [PATCH] Linux Kernel Markers
- From: Martin Bligh <mbligh at google dot com>
- To: "Frank Ch. Eigler" <fche at redhat dot com>
- Cc: Karim Yaghmour <karim at opersys dot com>, Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>, prasanna at in dot ibm dot com, Andrew Morton <akpm at osdl dot org>, Ingo Molnar <mingo at elte dot hu>, Mathieu Desnoyers <mathieu dot desnoyers at polymtl dot ca>, Paul Mundt <lethal at linux-sh dot org>, linux-kernel <linux-kernel at vger dot kernel dot org>, Jes Sorensen <jes at sgi dot com>, Tom Zanussi <zanussi at us dot ibm dot com>, Richard J Moore <richardj_moore at uk dot ibm dot com>, Michel Dagenais <michel dot dagenais at polymtl dot ca>, Christoph Hellwig <hch at infradead dot org>, Greg Kroah-Hartman <gregkh at suse dot de>, Thomas Gleixner <tglx at linutronix dot de>, William Cohen <wcohen at redhat dot com>, ltt-dev at shafik dot org, systemtap at sources dot redhat dot com, Alan Cox <alan at lxorguk dot ukuu dot org dot uk>
- Date: Wed, 20 Sep 2006 11:22:42 -0700
- Subject: Re: [PATCH] Linux Kernel Markers
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Frank Ch. Eigler wrote:
Hi -
On Wed, Sep 20, 2006 at 01:21:52PM -0400, Karim Yaghmour wrote:
[...] IOW, we should be able to do what Martin suggests fairly
easily (if we agree on a 5-byte "null" jump at the entry of
functions of interest). Right? [...]
My interpretation of Martin's Monday proposal is that, if implemented,
we wouldn't need any of this nop/int3 stuff. If function being
instrumented were recompiled on-the-fly, then it could sport plain &
direct C-level calls to the instrumentation handlers.
It's looking to me like it might still need djprobes to implement, in
order to get the atomic and safe switchover from the original function
into the traced one. All rather sad, but seems to be true from all the
CPU errata, etc. If anyone can see a way round that, I'd love to hear
it.
What it would give you above and beyond djprobes is an easier and more
flexible way to actually do the instrumentation itself.
M.