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Message-ID: <450F0180.1040606@us.ibm.com>
Date: Mon, 18 Sep 2006 13:28:48 -0700
From: Vara Prasad <prasadav@...ibm.com>
To: Alan Cox <alan@...rguk.ukuu.org.uk>
CC: "Frank Ch. Eigler" <fche@...hat.com>, Ingo Molnar <mingo@...e.hu>,
Paul Mundt <lethal@...ux-sh.org>,
Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
linux-kernel <linux-kernel@...r.kernel.org>,
Jes Sorensen <jes@....com>, Andrew Morton <akpm@...l.org>,
Tom Zanussi <zanussi@...ibm.com>,
Richard J Moore <richardj_moore@...ibm.com>,
Michel Dagenais <michel.dagenais@...ymtl.ca>,
Christoph Hellwig <hch@...radead.org>,
Greg Kroah-Hartman <gregkh@...e.de>,
Thomas Gleixner <tglx@...utronix.de>,
William Cohen <wcohen@...hat.com>,
"Martin J. Bligh" <mbligh@...igh.org>,
systemtap <systemtap@...rceware.org>
Subject: Re: tracepoint maintainance models
Alan Cox wrote:
>Ar Llu, 2006-09-18 am 12:10 -0700, ysgrifennodd Vara Prasad:
>
>
>>I am not sure i quiet understand your line number part of the proposal.
>>Does this proposal assume we have access to source code while generating
>>dynamic probes?
>>
>>
>
>Its one route - or we dump it into an ELF section in the binary.
>
>
Source code access is not a good solution but ELF section could work.
>
>
>>This still doesn't solve the problem of compiler optimizing such that a
>>variable i would like to read in my probe not being available at the
>>probe point.
>>
>>
>
>Then what we really need by the sound of it is enough gcc smarts to do
>something of the form
>
> .section "debugbits"
>
> .asciiz 'hook_sched'
> .dword l1 # Address to probe
> .word 1 # Argument count
> .dword gcc_magic_whatregister("next"); [ reg num or memory ]
> .dword gcc_magic_whataddress("next"); [ address if exists]
>
>
>Can gcc do any of that for us today ?
>
>
>
No, gcc doesn't do that today.
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