---
name: schunix-linux-abi-decision
description: Decided 2026-08-01 — Schunix drops its native syscall ABI and keeps only the Linux one
metadata: 
  node_type: memory
  type: project
  originSessionId: d1a1ea76-f919-411c-b0ef-0e1bc5064563
  modified: 2026-08-01T17:16:39.021Z
---

Decided 2026-08-01: **Schunix will use the Linux syscall ABI as its only ABI.**
The native Schunix numbering gets deleted. Not yet implemented as of that date.

**Why:** the kernel currently carries two ABIs — 185 native entries in
`kernel/sys/table.inc` and 157 Linux numbers mapped in `kernel/sys/linux_abi.c`
— with a `proc->syscall_map` indirection on every syscall to pick between them.
100% of the shipping userland (musl, mksh, toybox) is Linux-ABI. Exactly one
program used the native ABI (`cmd/init/main.c`), and `exec.c` chose the ABI by
*guessing from the ELF entry address* (`>= 0x100000`).

**How to apply:** rebuild init against musl like every other program, then
delete `lib/usys.S`, `sys_enable_linux_abi`, the `syscall_map` indirection, the
entry-address heuristic in `exec.c`, and the duplicate native `struct stat`
path (`stati_linux` vs native). Roughly −500 lines.

The user was uneasy that this makes Schunix "not a real UNIX" — it does not.
FreeBSD (linuxulator), illumos (lx zones), and WSL1 all implement the Linux
ABI. The ABI is a calling convention, not the OS.

See [[schunix-rewrite-priorities]], [[schunix-build-environment]].