On Fri, May 08, 2020 at 01:58:30PM +0200, Thomas Gleixner wrote:
> Peter Zijlstra <pet...@infradead.org> writes:
> >> > +static __always_inline void debug_enter(unsigned long *dr6, unsigned
> >> > long *dr7)
> >> > +{
> >> > + /*
> >> > + * Disable breakpoints during exception handling; recursive
> >> > exceptions
> >> > + * are exceedingly 'fun'.
> >> > + *
> >> > + * Since this function is NOKPROBE, and that also applies to
> >> > + * HW_BREAKPOINT_X, we can't hit a breakpoint before this (XXX
> >> > except a
> >> > + * HW_BREAKPOINT_W on our stack)
> >> > + *
> >> > + * Entry text is excluded for HW_BP_X and cpu_entry_area, which
> >> > + * includes the entry stack is excluded for everything.
> >> > + */
> >> > + get_debugreg(*dr7, 6);
> >>
> >> Do you mean get_debugreg(*dr7, 7); ?
> >
> > Shees, I have to go buy a new stack of brown paper bags at this rate,
> > don't I :/
>
> Not only you, but it's also amazing that the selftests didn't catch
> that.
I don't think the selftests try and set hardware breakpoints in the
kernel.
