Subject: Re: [RFC] [PATCH 4/7] Uprobes Implementation
From: Jim Keniston <jkenisto@us.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: maneesh@in.ibm.com, Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
        Ingo Molnar <mingo@elte.hu>,
        Arnaldo Carvalho de Melo <acme@infradead.org>,
        Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
        utrace-devel <utrace-devel@redhat.com>, Mark Wielaard <mjw@redhat.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Masami Hiramatsu <mhiramat@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>
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Date: Fri, 15 Jan 2010 15:44:45 -0800
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On Fri, 2010-01-15 at 12:12 +0100, Peter Zijlstra wrote:
...
> 
> Adding the probe uses the fact that (most) executable mappings are
> MAP_PRIVATE and CoWs a private copy of the page with the modified ins,
> right?
> 
> What does it do for MAP_SHARED|MAP_EXECUTABLE sections -- simply fail to
> add the probe?

If the vma containing the instruction to be probed has the VM_EXEC flag
set (and it's not in the XOL area) we go ahead and try to probe it.  I'm
not familar with the implications of MAP_SHARED|MAP_EXECUTABLE -- how
you would get such a combo, or what access_process_vm() would do with
it.

Jim 

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