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Re: [RFC] [PATCH 2.6.37-rc5-tip 5/20] 5: Uprobes: register/unregister probes.
- From: Peter Zijlstra <peterz at infradead dot org>
- To: Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>
- Cc: Ingo Molnar <mingo at elte dot hu>, Steven Rostedt <rostedt at goodmis dot org>, Linux-mm <linux-mm at kvack dot org>, Arnaldo Carvalho de Melo <acme at infradead dot org>, Linus Torvalds <torvalds at linux-foundation dot org>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Christoph Hellwig <hch at infradead dot org>, Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>, 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>, Andi Kleen <andi at firstfloor dot org>, LKML <linux-kernel at vger dot kernel dot org>, "Paul E. McKenney" <paulmck at linux dot vnet dot ibm dot com>
- Date: Thu, 27 Jan 2011 11:23:37 +0100
- Subject: Re: [RFC] [PATCH 2.6.37-rc5-tip 5/20] 5: Uprobes: register/unregister probes.
- References: <20101216095714.23751.52601.sendpatchset@localhost6.localdomain6> <20101216095817.23751.76989.sendpatchset@localhost6.localdomain6> <1295957744.28776.722.camel@laptop> <20110126075558.GB19725@linux.vnet.ibm.com> <1296036708.28776.1138.camel@laptop> <20110126153036.GN19725@linux.vnet.ibm.com> <1296056756.28776.1247.camel@laptop> <20110126165645.GP19725@linux.vnet.ibm.com> <1296061949.28776.1343.camel@laptop> <20110127100157.GS19725@linux.vnet.ibm.com>
On Thu, 2011-01-27 at 15:31 +0530, Srikar Dronamraju wrote:
> > > > - validate that the vma is indeed a map of the right inode
> > >
> > > We can add a check in write_opcode( we need to pass the inode to
> > > write_opcode).
> >
> > sure..
> >
> > > > - validate that the offset of the probe corresponds with the stored
> > > > address
> > >
> > > I am not clear on this. We would have derived the address from the
> > > offset. So is that we check for
> > > (vaddr == vma->vm_start + uprobe->offset)
> >
> > Sure, but the vma might have changed since you computed the offset -)
>
> If the vma has changed then it would fail the 2nd validation i.e vma
> corresponds to the uprobe inode right. If the vma was unmapped and
> mapped back at the same place, then I guess we are okay to probe.
It can be unmapped and mapped back slightly different. A map of the same
file doesn't need to mean its in the exact same location or has the
exact same pgoffset.