x86

Why do we need ud2 when int 6 is right there?

Raymond Chen explains why x86 has a dedicated ud2 undefined instruction rather than programs issuing int 6: the invalid-opcode exception is a fault that reports the faulting instruction's address, while a software interrupt is a trap reporting the next instruction, and operating systems deny user mode permission to issue int 6 anyway.

Blog post · x86 · Operating Systems · Low-Level Programming