Open Source Summit India 2026

FRED (Flexible Return and Event Delivery) represents a modernization of x86 processor event handling, replacing the decades-old IDT (Interrupt Descriptor Table) mechanism and eliminating its inherent design flaws. This advancement introduces new low-latency ring transitions that establish complete supervisor or user context. FRED uses stack-based event delivery with integrated event data and introduces dedicated ERETU and ERETS return instructions.

These enhancements resolve longstanding issues related to atomicity, consistency, and nested exception handling in x86 architecture. This results in faster, more reliable and robust event processing through simplified system software and reduced attack surface.

The talk will start with a look at traditional IDT event delivery and the issues it creates. Then, we’ll dive into the FRED overview, covering briefly its terminology, design, and core mechanisms. To wrap up, we’ll touch advanced topics like virtualization and GS segment handling, highlighting why FRED is a major leap forward for modern x86 architecture.