Dr. Brian Callahan discusses his recently accepted IEEE paper evaluating OpenBSD's -fret-clean mitigation, introduced in OpenBSD 7.6. The flag instructs LLVM to insert a zeroing movq instruction after every call on amd64, clearing the return address from the stack as a security countermeasure.
Background
OpenBSD is known for its security-first approach, regularly implementing novel mitigations against side-channel and control-flow attacks. The -fret-clean flag is one of their newer approaches to hardening the amd64 execution environment.
- Source
- Lobsters
- Published
- Aug 11, 2026 at 10:44 PM
- Score
- 6.0 / 10