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Re: [RFC] [PATCH 2.6.37-rc5-tip 13/20] 13: x86: x86 specific probe handling
- From: Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>
- To: Roland McGrath <roland at redhat dot com>
- Cc: Peter Zijlstra <peterz at infradead dot org>, Ingo Molnar <mingo at elte dot hu>, Steven Rostedt <rostedt at goodmis dot org>, Arnaldo Carvalho de Melo <acme at infradead dot org>, Linus Torvalds <torvalds at linux-foundation dot org>, Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>, Christoph Hellwig <hch at infradead dot org>, Andi Kleen <andi at firstfloor dot org>, Oleg Nesterov <oleg at redhat dot com>, Andrew Morton <akpm at linux-foundation dot org>, SystemTap <systemtap at sources dot redhat dot com>, Jim Keniston <jkenisto at linux dot vnet dot ibm dot com>, Frederic Weisbecker <fweisbec at gmail dot com>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, LKML <linux-kernel at vger dot kernel dot org>, "Paul E. McKenney" <paulmck at linux dot vnet dot ibm dot com>
- Date: Fri, 28 Jan 2011 10:27:21 +0530
- Subject: Re: [RFC] [PATCH 2.6.37-rc5-tip 13/20] 13: x86: x86 specific probe handling
- References: <20101216095714.23751.52601.sendpatchset@localhost6.localdomain6> <20101216095947.23751.75003.sendpatchset@localhost6.localdomain6> <1295963783.28776.1061.camel@laptop> <20110127094041.GR19725@linux.vnet.ibm.com> <1296123733.15234.53.camel@laptop> <20110127191146.DB22F180999@magilla.sf.frob.com>
- Reply-to: Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>
Hi Roland,
> > But I'll leave this to the x86 people who actually know the intricacies
> > of the single step cruft, I was just wondering why you weren't using (or
> > extending) the existing code.
>
> The hairy aspects of the step.c code are hairy (and not usable at interrupt
> level) because they do some instruction analysis. Since uprobes already
> does its own instruction analysis, reusing step.c's separate hacks makes
> less sense to me than integrating knowledge of the single-step vs
> pushf/popf issues into the uprobes instruction analysis.
>
> That said, there is further nontriviality just to do with the block-step
> support and with not clobbering user-visible usage of TF in eflags, which
> uprobes needs to handle as well. It makes sense to share that code rather
> than repeating it, even if that entails changes to the step.c code.
>
Uprobes doesn't request/handle block-step for now. So can we postpone
your suggested changes till uprobes needs to handle block-step?
--
Thanks and Regards
Srikar