D273 - A failed descriptor, count or offset answers -1

Status: assumed Date: 2026-09-26

A call whose result the caller uses directly as a descriptor, byte count or file offset answers FAILED_DESCRIPTOR (-1) on failure, not a GuestError placeholder and not a specific errno.

Why: the placeholders stay below the high bit so a trace never mistakes them for firmware values, which makes them small positive integers - exactly what a valid descriptor or count looks like. A caller testing < 0 then reads failure as success. Negative failure is the POSIX convention on a FreeBSD-derived kernel; which errno comes back is left to a hardware probe.

Rejected:

• The placeholder error code: reads as a valid descriptor, count or offset.
• A chosen errno value: nothing measured says which one the hardware returns.