Re: [PATCH v3 04/22] x86/doublefault: Make memmove() notrace/NOKPROBE

Paul E. McKenney
2020-02-19T16:27:50Z

On Wed, Feb 19, 2020 at 11:12:28AM -0500, Steven Rostedt wrote:
> On Wed, 19 Feb 2020 17:04:42 +0100
> Peter Zijlstra <peterz@infradead.org> wrote:
>
> > > - memmove(&gpregs->ip, (void *)regs->sp, 5*8);
> > > + for (i = 0; i < count; i++) {
> > > + int idx = (dst <= src) ? i : count - i;
> >
> > That's an off-by-one for going backward; 'count - 1 - i' should work
> > better, or I should just stop typing for today ;-)
>
> Or, we could just cut and paste the current memmove and make a notrace
> version too. Then we don't need to worry bout bugs like this.

OK, I will bite...

Can we just make the core be an inline function and make a notrace and
a trace caller? Possibly going one step further and having one call
the other? (Presumably the traceable version invoking the notrace
version, but it has been one good long time since I have looked at
function preambles.)

Thanx, Paul