D384 - The dispatch boundary does not assume the guest's stack alignment

Status: decided Date: 2026-08-30

Code entered from a guest-held function pointer (a gadget, or any call site this project does not control) establishes its own aligned stack frame and restores the guest's original stack pointer before returning, instead of assuming the caller's stack already met the calling convention's alignment.

Why: Every ordinary import is reached through a call site a compiler wrote, which the ABI guarantees is aligned; a gadget is reached however the guest's own code happens to call it, with no compiler-enforced guarantee. Vectorized code that assumes alignment raises a fault on a stack that is off by a few bytes, which nothing about the instruction set requires this project's own code to assume.

Rejected:

• Trusting the guest to call with an aligned stack: true for a call site a compiler wrote, false for a raw gadget, and a boundary this project controls one side of must not assume the other side's convention.