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Subject: Re: [RFC] [PATCH 2.6.37-rc5-tip 5/20]  5: Uprobes:
 register/unregister probes.
From: Peter Zijlstra <peterz@infradead.org>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>,
        Linux-mm <linux-mm@kvack.org>,
        Arnaldo Carvalho de Melo <acme@infradead.org>,
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        Oleg Nesterov <oleg@redhat.com>,
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Date: Thu, 27 Jan 2011 11:23:37 +0100
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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.