Expand description
Sub-VM child guest. CALLed by the parent (Image M) with an
input Cap::Data in slot[0]. Reads the bytes, computes their
wrapping byte-sum, publishes the result as a single-byte
Cap::Data back into slot[0], and HALTs. The kernel’s
HALT-reflect path moves the child’s slot[0] back into the
parent’s slot[0].