Re: [PATCH] x86: kprobes change kprobe_handler flow

["Abhishek Sagar" <sagar.abhishek@gmail.com>]

On 1/4/08, Masami Hiramatsu <mhiramat@redhat.com> wrote:
> I could understand what the original code did at last.
> If a kprobe is inserted on a breakpoint which other debugger inserts,
> it single step inline instead of out-of-line.(this is done in prepare_singlestep)
> In this case, (p && kprobe_running() && kcb->kprobe_status==KPROBE_HIT_SS)
> is true and we need pass the control to the debugger.
> And if (*p->ainsn.insn != BREAKPOINT_INSTRUCTION) (or (p != kprobe_running())) in
> that case, there may be some bugs.

Yes, we can only fault while singlestepping for a unique case, which
is when we're singlestepping (in-line) a breakpoint because a probe
was installed on it. All other scenarios are a BUG . That's also
assuming that no exception will preempt singlestepping, whose codepath
has a probe on it.

> Now I think your original suggestion is correct.
> Please fix it in another patch.

Ok.

> --
> Masami Hiramatsu
>
> Software Engineer
> Hitachi Computer Products (America) Inc.
> Software Solutions Division
>
> e-mail: mhiramat@redhat.com, masami.hiramatsu.pt@hitachi.com

Thanks,
Abhishek Sagar