ud2

Undefined Instruction

UD2

Generates an invalid opcode exception.

Pseudocode Operation

raise InvalidOpcodeException()

Encoding

Binary Layout

0F

+0

0B

+1

 

Format Legacy

Opcode 0F 0B

Extension Base

Operands

Related

More in Base

Reference

View in Intel® 64 and IA-32 Architectures SDM ↗ Intel® SDM

Instruction Forms

Opcode	Instruction	Op/En	64/32-bit Mode	CPUID	Description
0F FF /r	UD01 r32, r/m32	RM	Valid Valid		Raise invalid opcode exception.
0F B9 /r	UD1 r32, r/m32	RM	Valid Valid		Raise invalid opcode exception.
0F 0B	UD2	ZO	Valid Valid		Raise invalid opcode exception.
D6	UDB		Valid N.E.	Z0	Raise invalid opcode exception.

Description

Generates an invalid opcode exception. This instruction is provided for software testing to explicitly generate an invalid opcode exception. The opcodes for this instruction are reserved for this purpose. Other than raising the invalid opcode exception, this instruction has no effect on processor state or memory. Even though it is the execution of the UD instruction that causes the invalid opcode exception, the instruction pointer saved by delivery of the exception references the UD instruction (and not the following instruction). This instruction’s operation is the same in non-64-bit modes and 64-bit mode.

Operation

#UD (* Generates invalid opcode exception *);

Flags Affected

None. Exceptions (All Operating Modes) #UD Raises an invalid opcode exception in all operating modes. (UDB does so only in 64-bit mode.) UD-Undefined Instruction Vol. 2B 4-736