The last hole in the substrate: a caller could write a class through the syscall
but not read one back. `CUBE_OP_GET` now fills `args.flags` from the same index
entry the address came from, so learning what a record *is* costs nothing beyond
a read that was going to happen.
One field for both directions, because it is one thing — the class of this
record. A write states it, a read learns it, and neither is a special case of the
other. `find` hands the mask back with the address for the same reason: it is in
the same stride the binary search already read, so wanting both does not mean
searching twice. A read that finds nothing leaves 0 rather than a stale class for
the caller to believe.
The size of `cube_args` does not change, which matters because `size` is what
says which argument block arrived.
surface-camera-build
1081b5f1e2