Dynamic djprobe (and summary of Q&A)

[Roland McGrath]

I'm not at all clear on why anything at higher level should think about the
issue.  The insertion of jump trampolines is an optimization over the
insertion of int3 breakpoints.  The smarts should just be merged into
kprobes so that it uses the more efficient style when possible and falls
back when it's hard.  That means, compute the length of the target
instruction and see how much space it allows for what kind of jump instruction.