kernel API for in-kernel single stepping

[Frank Ch. Eigler]

Hi, Paul -


> [...]
> > [...]  With the various kernel debuggers, kprobes, itrace, and
> > maybe others trying to share these
> > [MSR/single-stepping/notify_die] resources do you think it is time
> > to develop some sort of kernel single stepping API?  Frank is
> > requesting this API before changing SystemTap to support single
> > step traps.

Actually, I have asked only about user-space single-stepping, possibly
based on the utrace API.  Broad kernel-space single-stepping is risky
enough not to attempt yet.

> At present kprobes sets the MSR_SE bit in the MSR when it wants to
> single-step, and uses the notify_die infrastructure as the way it
> gets notified when the single-step trap occurs.  [...]  In other
> words the API for single-stepping is just the notify_die stuff.
> [...]

We can attempt this later.

- FChE