모두의 코드
CLI (Intel x86/64 assembly instruction)

작성일 : 2020-09-01 이 글은 1547 번 읽혔습니다.

CLI

Clear Interrupt Flag

참고 사항

아래 표를 해석하는 방법은 x86-64 명령어 레퍼런스 읽는 법 글을 참조하시기 바랍니다.

Opcode

Instruction

Op/
En

64-bit
Mode

Compat/
Leg Mode

Description

FA

CLI

NP

Valid

Valid

Clear interrupt flag; interrupts disabled when interrupt flag cleared.

Instruction Operand Encoding

Op/En

Operand 1

Operand 2

Operand 3

Operand 4

NP

NA

NA

NA

NA

Description

If protected-mode virtual interrupts are not enabled, CLI clears the IF flag in the EFLAGS register. No other flags are affected. Clearing the IF flag causes the processor to ignore maskable external interrupts. The IF flag and the CLI and STI instruction have no affect on the generation of exceptions and NMI interrupts.

When protected-mode virtual interrupts are enabled, CPL is 3, and IOPL is less than 3; CLI clears the VIF flag in the EFLAGS register, leaving IF unaffected. Table 3-7 indicates the action of the CLI instruction depending on the processor operating mode and the CPL/IOPL of the running program or procedure.

Operation is the same in all modes.

Table 3-7. Decision Table for CLI Results

PE

VM

IOPL

CPL

PVI

VIP

VME

CLI Result

0

X

X

X

X

X

X

IF = 0

1

0

>= CPL

X

X

X

X

IF = 0

1

0

< CPL

3

1

X

X

VIF = 0

1

0

< CPL

< 3

X

X

X

GP Fault

1

0

< CPL

X

0

X

X

GP Fault

1

1

3

X

X

X

X

IF = 0

1

1

< 3

X

X

X

1

VIF = 0

1

1

< 3

X

X

X

0

GP Fault

* X = This setting has no impact

Operation

IF PE = 0
    THEN
          IF <- 0; (* Reset Interrupt Flag *)
    ELSE
          IF VM = 0;
                THEN
                      IF IOPL >= CPL
                            THEN
                                  IF <- 0; (* Reset Interrupt Flag *)
                      ELSE
                            IF ((IOPL < CPL) and (CPL = 3) and (PVI = 1))
                                  THEN
                                        VIF <- 0; (* Reset Virtual Interrupt Flag *)
                                  ELSE
                                        #GP(0);
FI;
                      FI;
                ELSE (* VM = 1 *)
                      IF IOPL = 3
                            THEN
                                  IF <- 0; (* Reset Interrupt Flag *)
                            ELSE 
                                  IF (IOPL < 3) AND (VME = 1)
                                        THEN
                                              VIF <- 0; (* Reset Virtual Interrupt Flag *)
                                        ELSE
                                              #GP(0);
                                  FI;
                      FI;
          FI;
FI;

Flags Affected

If protected-mode virtual interrupts are not enabled, IF is set to 0 if the CPL is equal to or less than the IOPL; other-wise, it is not affected. Other flags are unaffected.

When protected-mode virtual interrupts are enabled, CPL is 3, and IOPL is less than 3; CLI clears the VIF flag in the EFLAGS register, leaving IF unaffected. Other flags are unaffected.

Protected Mode Exceptions

#GP(0)

  • If the CPL is greater (has less privilege) than the IOPL of the current program or procedure.

#UD

  • If the LOCK prefix is used.

Real-Address Mode Exceptions

#UD

  • If the LOCK prefix is used.

Virtual-8086 Mode Exceptions

#GP(0)

  • If the CPL is greater (has less privilege) than the IOPL of the current program or procedure.

#UD

  • If the LOCK prefix is used.

Compatibility Mode Exceptions

Same exceptions as in protected mode.

64-Bit Mode Exceptions

#GP(0)

  • If the CPL is greater (has less privilege) than the IOPL of the current program or procedure.

#UD

  • If the LOCK prefix is used.

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