On Fri, Nov 1, 2019 at 6:50 AM Sergey Senozhatsky
<sergey.senozhatsky.work@xxxxxxxxx> wrote:
>
> On (19/10/30 15:22), glider@xxxxxxxxxx wrote:
> > Clang may replace stackdepot_memcmp() with a call to instrumented bcmp(),
> > which is exactly what we wanted to avoid creating stackdepot_memcmp().
> > Add a compiler barrier() to prevent optimizations.
>
> [..]
>
> > @@ -163,6 +163,11 @@ int stackdepot_memcmp(const unsigned long *u1, const unsigned long *u2,
> > unsigned int n)
> > {
> > for ( ; n-- ; u1++, u2++) {
> > + /*
> > + * Prevent Clang from replacing this function with a bcmp()
> > + * call.
> > + */
> > + barrier();
> > if (*u1 != *u2)
> > return 1;
> > }
>
> Would 'volatile' do the trick?
It does. I can replace the barrier with a volatile if you think that's better.
However this'll add a checkpatch warning, as volatiles are discouraged
for synchronization (although in this case there's no synchronization)
>
> -ss
--
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