Re: [RFC][PATCH 1/2] x86: Allow breakpoints to emulate call functions

From: Linus Torvalds
Date: Mon May 06 2019 - 16:52:24 EST

On Mon, May 6, 2019 at 1:42 PM Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> What *can* make sense is "Oh, I'm emulating a call, but I know that
> call will be rewritten, so let me emulate the call and then
> short-circuit the emulation immediately".

That made no sense. The end should have been "and then short-circuit
the _rewriting_ immediately" of course.

The "emulate a call" is just to make the "struct pt_regs" state look
like it would have after the call. The "short circuit the rewriting"
part is the thing that then rewrites the actual instruction based on
that pt_regs state.