image/svg+xmlCLAC—Clear AC Flag in EFLAGS RegisterInstruction Operand EncodingDescriptionClears the AC flag bit in EFLAGS register. This disables any alignment checking of user-mode data accesses. If the SMAP bit is set in the CR4 register, this disallows explicit supervisor-mode data accesses to user-mode pages.This instruction's operation is the same in non-64-bit modes and 64-bit mode. Attempts to execute CLAC when CPL> 0 cause #UD.OperationEFLAGS.AC := 0;Flags AffectedAC cleared. Other flags are unaffected.Protected Mode Exceptions#UD If the LOCK prefix is used.If the CPL > 0.If CPUID.(EAX=07H, ECX=0H):EBX.SMAP[bit 20] = 0.Real-Address Mode Exceptions#UD If the LOCK prefix is used.If CPUID.(EAX=07H, ECX=0H):EBX.SMAP[bit 20] = 0.Virtual-8086 Mode Exceptions#UD The CLAC instruction is not recognized in virtual-8086 mode.Compatibility Mode Exceptions#UD If the LOCK prefix is used.If the CPL > 0.If CPUID.(EAX=07H, ECX=0H):EBX.SMAP[bit 20] = 0.64-Bit Mode Exceptions#UD If the LOCK prefix is used.If the CPL > 0.If CPUID.(EAX=07H, ECX=0H):EBX.SMAP[bit 20] = 0.Opcode/InstructionOp / En64/32 bit Mode SupportCPUID Feature FlagDescriptionNP 0F 01 CACLACZOV/VSMAPClear the AC flag in the EFLAGS register.Op/EnOperand 1Operand 2Operand 3Operand 4ZONANANANA

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