Indy
November 8th, 2009, 04:50
Intel® 64 and IA-32 Architectures Software Developer’s Manual Volume 3A System Programming Guide, 7.1.2.2:
Quote:
To explicitly force the LOCK semantics, software can use the LOCK prefix with the
following instructions when they are used to modify a memory location. An invalid-
opcode exception (#UD) is generated when the LOCK prefix is used with any other
instruction or when no write operation is made to memory (that is, when the destina-
tion operand is in a register).
• The bit test and modify instructions (BTS, BTR, and BTC).
• The exchange instructions (XADD, CMPXCHG, and CMPXCHG8B).
• The LOCK prefix is automatically assumed for XCHG instruction.
• The following single-operand arithmetic and logical instructions: INC, DEC, NOT,
and NEG.
• The following two-operand arithmetic and logical instructions: ADD, ADC, SUB,
SBB, AND, OR, and XOR. |
If you perform branching with the prefix
PREFIX_LOCK(0xF0), CPU generates a
# UD, then ISR
KiTrap06 process it and return code
STATUS_INVALID_LOCK_SEQUENCE.
Set a breakpoint to Olly on
ntdll!KiUserExceptionDispatcher, you'll have a reason for the error and the full context of the flow.
