On Wed, Dec 20, 2017 at 09:52:05PM +0100, Arnd Bergmann wrote: > diff --git a/crypto/aes_generic.c b/crypto/aes_generic.c > index ca554d57d01e..35f973ba9878 100644 > --- a/crypto/aes_generic.c > +++ b/crypto/aes_generic.c > @@ -1331,6 +1331,20 @@ EXPORT_SYMBOL_GPL(crypto_aes_set_key); > f_rl(bo, bi, 3, k); \ > } while (0) > > +#if __GNUC__ >= 7 > +/* > + * Newer compilers try to optimize integer arithmetic more aggressively, > + * which generally improves code quality a lot, but in this specific case > + * ends up hurting more than it helps, in some configurations drastically > + * so. This turns off two optimization steps that have been shown to > + * lead to rather badly optimized code with gcc-7. > + * > + * See also https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83356 > + */ > +#pragma GCC optimize("-fno-tree-pre") > +#pragma GCC optimize("-fno-tree-sra") So do it only when UBSAN is enabled? GCC doesn't have a particular predefined macro for those (only for asan and tsan), but either the kernel does have something already, or could have something added in the corresponding Makefile. Jakub
