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Re: [PATCH] Linux Kernel Markers
- From: Ingo Molnar <mingo at elte dot hu>
- To: Martin Bligh <mbligh at google dot com>
- Cc: Andrew Morton <akpm at osdl dot org>, "Frank Ch. Eigler" <fche at redhat dot com>, 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: Tue, 19 Sep 2006 18:36:56 +0200
- Subject: Re: [PATCH] Linux Kernel Markers
- References: <20060918234502.GA197@Krystal> <20060919081124.GA30394@elte.hu> <451008AC.6030006@google.com> <20060919154612.GU3951@redhat.com> <4510151B.5070304@google.com> <20060919093935.4ddcefc3.akpm@osdl.org> <45101DBA.7000901@google.com>
* Martin Bligh <mbligh@google.com> wrote:
> Andrew Morton wrote:
> >On Tue, 19 Sep 2006 09:04:43 -0700
> >Martin Bligh <mbligh@google.com> wrote:
> >
> >
> >>It seems like all we'd need to do
> >>is "list all references to function, freeze kernel, update all
> >>references, continue"
> >
> >
> >"overwrite first 5 bytes of old function with `jmp new_function'".
>
> Yes, that's simple. but slower, as you have a double jump. Probably a
> damned sight faster than int3 though.
modern CPUs will probably even optimize that intermediate jump away in
their BTB-ish caches. But in any case this would solve the function
pointer problem too.
Ingo