On Thu, 2016-02-25 at 10:39 +1100, Balbir Singh wrote: > On 25/02/16 01:28, Michael Ellerman wrote: > > is_early_mcount_callsite() needs to detect either the two instruction or > > the three instruction versions of the _mcount() sequence. > > > > But if we're running a kernel with the two instruction sequence, we need > > to be careful not to read instruction - 2, otherwise we might fall off > > the front of a page and cause an oops. > > > > While we're here convert to bool to make the return semantics clear. > > > > Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> > > > Do we even need to do this anymore? Yes. Otherwise the code in apply_relocate_add() will see a far call with no nop slot after it to do the toc restore, and it considers that a bug (which it usually is, except mcount is special). As we discussed today I'm hoping we can clean this code up a bit more in the medium term, but this works for now. cheers -- To unsubscribe from this list: send the line "unsubscribe live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
