D400 - Every guest-facing stub carries a syscall entry at a fixed offset

Status: decided Date: 2026-08-30

Every address this project hands a guest as an implementation carries a working syscall dispatch entry reachable by jumping into it partway through its body, at any of several small offsets, rather than only at its start.

Why: An open-toolchain guest resolves an ordinary function and computes its syscall entry point as a fixed offset into that function's own body, expecting to land inside a real instruction on the platform. Every address this project hands out is otherwise a self-contained stub with nothing at that offset, so the guest's own convention needs somewhere real to land regardless of which library build produced the offset it uses.

Rejected:

• Serving the syscall entry only at a stub's starting address: matches a guest that calls normally and nothing about a guest that computes an internal offset.
• Supporting exactly one fixed offset: works for one library build and silently misleads guests built against a different one.