Messages in this thread | | | From | Sami Tolvanen <> | Date | Wed, 19 Oct 2022 08:22:17 -0700 | Subject | Re: [PATCH] x86/ibt: Implement FineIBT |
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On Wed, Oct 19, 2022 at 5:03 AM Peter Zijlstra <peterz@infradead.org> wrote: > > On Tue, Oct 18, 2022 at 10:05:26PM -0700, Kees Cook wrote: > > > > The one glitch here is that the resulting hash needs to not contain > > an endbr... > > Oh right,.. duh. How about something like: > > static u32 cfi_rehash(u32 hash) > { > hash ^= cfi_hash; > while (unlikely(is_endbr(hash))) { > bool lsb = hash & 1; > hash >>= 1; > if (lsb) > hash ^= 0x80200003; > } > return hash; > } > > Which seems properly over-engineered :-)
Also, -hash can't be endbr with KCFI since we use that in the check itself.
Sami
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