Re: [PATCH -tip 1/2] Kconfig: Bump required compiler version of KASAN and UBSAN

From: Peter Zijlstra
Date: Tue Jun 02 2020 - 15:39:23 EST

On Tue, Jun 02, 2020 at 09:25:47PM +0200, Marco Elver wrote:
> On Tue, 2 Jun 2020 at 21:19, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:

> > Currently x86 only, but I know other arch maintainers are planning to
> > have a hard look at their code based on our findings.
> I've already spotted a bunch of 'noinstr' outside arch/x86 e.g. in
> kernel/{locking,rcu}, and a bunch of these functions use atomic_*, all
> of which are __always_inline. The noinstr uses outside arch/x86 would
> break builds on all architecture with GCC <= 7 when using sanitizers.
> At least that's what led me to conclude we need this for all
> architectures.

True; but !x86 could, probably, get away with not fully respecting
noinstr at this time. But that'd make a mess of things again, so my
preference is as you did, unilaterally raise the min version for *SAN.

That said; noinstr's __no_sanitize combined with atomic_t might be
'interesting', because the regular atomic things have explicit
annotations in them. That should give validation warnings for the right
.config, I'll have to go try -- so far I've made sure to never enable
the *SAN stuff.