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Re: [PATCH] Linux Kernel Markers
- From: fche at redhat dot com (Frank Ch. Eigler)
- To: Martin Bligh <mbligh at google dot com>
- Cc: 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>, Andrew Morton <akpm at osdl dot org>, 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: 19 Sep 2006 12:49:20 -0400
- Subject: Re: [PATCH] Linux Kernel Markers
- References: <20060918234502.GA197@Krystal> <20060919081124.GA30394@elte.hu> <451008AC.email@example.com> <20060919154612.GU3951@redhat.com> <4510151B.firstname.lastname@example.org>
Martin Bligh <email@example.com> writes:
> [...] "compiled anew from original sources after deployment" seems
> the most practical to do to me. From second hand info on using
> systemtap, you seem to need the same compiler and source tree to
> work from anyway [...]
Not quite. Systemtap does not look at sources, only object code and
its embedded debugging information. (How many distributions keep
around compilable source trees?)
> [...] It seems like all we'd need to do is "list all references to
> function, freeze kernel, update all references, continue", [...]
One additional problem are external references made *by* the function.
Those too would all have to be relocated to the live data.
Live code patching is theoretically useful for all kinds of things,
but I've never heard it described as relatively simple before! :-)