Did you read the patch? It uses an empirical configure check to discover if the assembler does in fact support ud2.
- [PATCH] x86: Use ud2 assembly mnemonic when available. Roland McGrath
- Re: [PATCH] x86: Use ud2 assembly mnemonic when availa... Andrew Pinski
- Re: [PATCH] x86: Use ud2 assembly mnemonic when av... Andrew Pinski
- Re: [PATCH] x86: Use ud2 assembly mnemonic whe... Roland McGrath
- Re: [PATCH] x86: Use ud2 assembly mnemonic when availa... Uros Bizjak
- Re: [PATCH] x86: Use ud2 assembly mnemonic when av... Roland McGrath
