← Wednesday, October 21, 2026Performance & OSDeep dive

The x86 UD2 instruction faults where INT 6 traps

devblogs.microsoft.com Editor score 7/10

UD2 reports the address of the invalid instruction, while INT 6 reports the address after the interrupt because a fault and a trap have different semantics. Understanding that distinction helps when reasoning about exception handling and low-level control flow.

What

The x86 UD2 instruction raises an invalid-opcode fault; an explicit INT 6 raises a trap instead.

How

A fault reports the address of its own instruction, while INT 6 reports the address of the following instruction; user mode cannot invoke INT 6 on operating systems described.

Why it matters

The distinction matters to kernel exception handlers, which may inspect or emulate the faulting instruction and expect its address in the fault frame.

Read on devblogs.microsoft.com → Lobsters

Headline, summary, brief and diagram are written by a model from the source's own text; the link, byline and numbers come from the source. Read the original before relying on a claim.