cpuid: Disable FSGSBASE feature for guest workloads - #14487
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Systrap allows apps to modify the GS register to use for their own purposes. However, because it initially reserves the register to use for syscall patching , the sentry must be alerted when the app attempts to set it so that it can unpatch all patched syscall areas before allowing the guest to use the register. Thus, we disable the FSGSBASE feature on Systrap so workloads are informed that they cannot use `wrgsbase` instruction to make a userspace write to the register (which would bypass the sentry). PiperOrigin-RevId: 972832746
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cpuid: Disable
FSGSBASEfeature for guest workloadsSystrap allows apps to modify the GS register to use for their own purposes.
However, because it initially reserves the register to use for syscall
patching , the sentry must be alerted when the app attempts to set it
so that it can unpatch all patched syscall areas before
allowing the guest to use the register.
Thus, we disable the FSGSBASE feature on Systrap so workloads are informed
that they cannot use
wrgsbaseinstruction to make a userspace writeto the register (which would bypass the sentry).