Peter Zijlstra says:

These patches address a number of instrumentation issues that were found after
the x86/entry overhaul. When combined with rcu/urgent and objtool/urgent, these
patches make UBSAN/KASAN/KCSAN happy again.

Part of making this all work is bumping the minimum GCC version for KASAN
builds to gcc-8.3, the reason for this is that the __no_sanitize_address
function attribute is broken in GCC releases before that.

No known GCC version has a working __no_sanitize_undefined, however because the
only noinstr violation that results from this happens when an UB is found, we
treat it like WARN. That is, we allow it to violate the noinstr rules in order
to get the warning out.
-----BEGIN PGP SIGNATURE-----
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=fcu1
-----END PGP SIGNATURE-----