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arm64: Use FEAT_SSBS as a Spectre-V4 workaround
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Authored by andrew on Sep 12 2023, 3:28 PM.
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Details

Reviewers
manu
Group Reviewers
arm64
Summary

FEAT_SSBS adds a flag to that allows the hardware to load or store
speculatively in a way that could lead to a cache timing side channel.
We have been implicitly supporting this flag in the kernel by clearing
it on boot, but should allow the user to set it in the same way as the
existing workaround.

Sponsored by: Arm Ltd

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rG FreeBSD src repository
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Buildable 53551
Build 50442: arc lint + arc unit