printing the instruction pointer under x86-64

[Roland McGrath]

> While strace is not prepared to do a full backtrace - could it
> recognize the vDSO and do a single frame?  It should be pretty simple
> to recognize a canned code sequence and take a single action.

There are several different vDSO code sequences seen in different
configurations, different hardware, different kernel versions.  Moreover,
one frame to the vDSO's caller is rarely going to be very useful.  It's not
real edifying to see that a 'read' syscall came from the libc 'read'
function.  You need full unwinding capability to get beyond that.
So I don't see any motivation for such half-measures.


Thanks,
Roland