On Fri, Jan 15, 2010 at 10:50:14AM +0100, Peter Zijlstra wrote: > On Fri, 2010-01-15 at 15:08 +0530, Ananth N Mavinakayanahalli wrote: > > On Fri, Jan 15, 2010 at 10:03:48AM +0100, Peter Zijlstra wrote: > > > On Thu, 2010-01-14 at 11:46 -0800, Jim Keniston wrote: > > > > > > > > discussed elsewhere. > > > > > > Thanks for the pointer... > > > > :-) > > > > Peter, > > I think Jim was referring to > > http://sources.redhat.com/ml/systemtap/2007-q1/msg00571.html > > That's a 2007 email from some obscure list... that's hardly something > that can be referenced to without link. > > As previously stated, I think poking at a process's address space is an > utter no-go.
In which case we'll need to find a different solution to it. The gdb style of 'breakpoint hit' -> 'put original instruction back in place' -> single-step -> 'put back the breakpoint' would be a big limiter, especially for multithreaded cases. The design here is to have a small vma sufficiently high enough in memory a-la vDSO that most apps won't reach, though there is still no ironclad guarantee. Ideally, we will need to single-step on a copy of the instruction, in the user address space of the traced process. Ideas? Ananth
