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

[Linus Torvalds]

On Mon, May 6, 2019 at 8:22 PM Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
>
> But still, we need to emulate the call, which requires pushing the
> return code back onto the stack. I believe that part is the part we are
> struggling with.

Yes. But I was looking at the ftrace parts because I didn't see the
bug in the low-level x86 side, so...

The x86 int3 faulting code itself looks so *trivially* simple, and it
does work for the trivial test-case too. Which was what made me go
"Hmm, maybe there's timing or something".

But it could obviously also be that the trivial test-case is just too
trivial, and doesn't involve nmi etc etc.

               Linus