ARM branch predictor hardening
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Cover letter [PATCH 0/3] ARM branch predictor hardening
Quoted 17 lines · Marc Zyngier
Hi Tony,
Quoted 14 lines · Tony Lindgren
Quoted 12 lines · Marc Zyngier
This small series implements some basic BP hardening by invalidating the BTB on CPUs that are known to be susceptible to aliasing attacks.
These patches are closely modelled against what we do on arm64, although simpler as we can rely on an architected instruction to perform the invalidation.
The first patch reuses the Cortex-A8 BTB invalidation in
switch_mmand generalises it to be used on all affected CPUs. The second perform the same invalidation on fatal signal delivery. The last one nukes it on guest exit, and results in some major surgery (kudos to Dimitris Papastamos who came up with the magic vector decoding sequence).
Quoted 4 lines
Quoted 2 lines
So if a Cortex-A8 has bootloder set the IBE bit, and kernel has
ARM_ERRATA_430973enabled, is Cortex-A8 already hardened then?Almost. See the extra BTB invalidation in
fault.c.
OK thanks. So for Cortex-A8, only patch "[PATCH 2/3] arm: Invalidate BTB on fatal signal for Cortex A8, A9, A12, A15 and A17" is needed if I read that right.
Regards,
Tony