use static data provided by the kernel. This avoids the need for a ring transition and so is more lightweight than a syscall. The function gettimeofday can be provided this way.

Hypervisor mode

Recent CPUs from Intel and AMD offer x86 virtualization instructions for a hypervisor to control Ring 0 hardware access. Although they are mutually incompatible, both Intel VT-x (codenamed "Vanderpool") and AMD-V

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