x86 EFLAGS: Difference between revisions
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→EFLAGS table: fix bit offsets in the table |
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| Line 7: | Line 7: | ||
! Abbreviation | ! Abbreviation | ||
|- | |- | ||
! | ! 0 | ||
| S | | S | ||
| Carry Flag | | Carry Flag | ||
| <code>CF</code> | | <code>CF</code> | ||
|- | |- | ||
! | ! 1 | ||
| 0 | | 0 | ||
| Always clear | | Always clear | ||
| <code>rsvd_2</code><ref>For reserved flags, name from the code below is shown.</ref> | | <code>rsvd_2</code><ref>For reserved flags, name from the code below is shown.</ref> | ||
|- | |- | ||
! | ! 2 | ||
| S | | S | ||
| Parity Flag | | Parity Flag | ||
| <code>PF</code> | | <code>PF</code> | ||
|- | |- | ||
! | ! 3 | ||
| 1 | | 1 | ||
| Always set | | Always set | ||
| <code>rsvd_4</code> | | <code>rsvd_4</code> | ||
|- | |- | ||
! | ! 4 | ||
| S | | S | ||
| Auxiliary Carry Flag | | Auxiliary Carry Flag | ||
| <code>AF</code> | | <code>AF</code> | ||
|- | |- | ||
! | ! 5 | ||
| 1 | | 1 | ||
| Always set | | Always set | ||
| <code>rsvd_6</code> | | <code>rsvd_6</code> | ||
|- | |- | ||
! | ! 6 | ||
| S | | S | ||
| Zero Flag | | Zero Flag | ||
| <code>ZF</code> | | <code>ZF</code> | ||
|- | |- | ||
! | ! 7 | ||
| S | | S | ||
| Sign Flag | | Sign Flag | ||
| <code>SF</code> | | <code>SF</code> | ||
|- | |- | ||
! | ! 8 | ||
| X | | X | ||
| Trap Flag | | Trap Flag | ||
| <code>TF</code> | | <code>TF</code> | ||
|- | |- | ||
! | ! 9 | ||
| X | | X | ||
| Interrupt Enable Flag | | Interrupt Enable Flag | ||
| <code>IF</code> | | <code>IF</code> | ||
|- | |- | ||
! | ! 10 | ||
| C | | C | ||
| Direction Flag | | Direction Flag | ||
| <code>DF</code> | | <code>DF</code> | ||
|- | |- | ||
! | ! 11 | ||
| S | | S | ||
| Overflow Flag | | Overflow Flag | ||
| <code>OF</code> | | <code>OF</code> | ||
|- | |||
! 12 | |||
|rowspan=2| X | |||
|rowspan=2| I/O Privilege Level | |||
|rowspan=2| <code>IOPL</code> | |||
|- | |- | ||
! 13 | ! 13 | ||
|- | |||
! 14 | |||
| X | |||
|- | | Nested Task | ||
! 14 | |||
| X | |||
| Nested Task | |||
| <code>NT</code> | | <code>NT</code> | ||
|- | |- | ||
! 15 | ! 15 | ||
| 0 | | 0 | ||
| Always clear | | Always clear | ||
| <code>rsvd_15</code> | | <code>rsvd_15</code> | ||
|- | |- | ||
! 16 | ! 16 | ||
| X | | X | ||
| Resume Flag | | Resume Flag | ||
| <code>RF</code> | | <code>RF</code> | ||
|- | |- | ||
! 17 | ! 17 | ||
| X | | X | ||
| Virtual-8086 Mode | | Virtual-8086 Mode | ||
| <code>VM</code> | | <code>VM</code> | ||
|- | |- | ||
! 18 | ! 18 | ||
| X | | X | ||
| Alignment Check / Access Control | | Alignment Check / Access Control | ||
| <code>AC</code> | | <code>AC</code> | ||
|- | |- | ||
! 19 | ! 19 | ||
| X | | X | ||
| Virtual Interrupt Flag | | Virtual Interrupt Flag | ||
| <code>VIF</code> | | <code>VIF</code> | ||
|- | |- | ||
! 20 | ! 20 | ||
| X | | X | ||
| Virtual Interrupt Pending | | Virtual Interrupt Pending | ||
| <code>VIP</code> | | <code>VIP</code> | ||
|- | |- | ||
! 21 | ! 21 | ||
| X | | X | ||
| ID Flag | | ID Flag | ||
| <code>ID</code> | | <code>ID</code> | ||
|} | |} | ||
Latest revision as of 17:21, 22 March 2025
EFLAGS table
| Bit | Type /val.[1] |
Name | Abbreviation |
|---|---|---|---|
| 0 | S | Carry Flag | CF
|
| 1 | 0 | Always clear | rsvd_2[2]
|
| 2 | S | Parity Flag | PF
|
| 3 | 1 | Always set | rsvd_4
|
| 4 | S | Auxiliary Carry Flag | AF
|
| 5 | 1 | Always set | rsvd_6
|
| 6 | S | Zero Flag | ZF
|
| 7 | S | Sign Flag | SF
|
| 8 | X | Trap Flag | TF
|
| 9 | X | Interrupt Enable Flag | IF
|
| 10 | C | Direction Flag | DF
|
| 11 | S | Overflow Flag | OF
|
| 12 | X | I/O Privilege Level | IOPL
|
| 13 | |||
| 14 | X | Nested Task | NT
|
| 15 | 0 | Always clear | rsvd_15
|
| 16 | X | Resume Flag | RF
|
| 17 | X | Virtual-8086 Mode | VM
|
| 18 | X | Alignment Check / Access Control | AC
|
| 19 | X | Virtual Interrupt Flag | VIF
|
| 20 | X | Virtual Interrupt Pending | VIP
|
| 21 | X | ID Flag | ID
|
C macro constants
#define X86_EFLAGS_CF 0 /* Carry Flag [S] */
#define X86_EFLAGS_rsvd_2 1 /* Always clear [0] */
#define X86_EFLAGS_PF 2 /* Parity Flag [S] */
#define X86_EFLAGS_rsvd_4 3 /* Always set [1] */
#define X86_EFLAGS_AF 4 /* Auxiliary Carry Flag [S] */
#define X86_EFLAGS_rsvd_6 5 /* Always set [1] */
#define X86_EFLAGS_ZF 6 /* Zero Flag [S] */
#define X86_EFLAGS_SF 7 /* Sign Flag [S] */
#define X86_EFLAGS_TF 8 /* Trap Flag [X] */
#define X86_EFLAGS_IF 9 /* Interrupt Enable Flag [X] */
#define X86_EFLAGS_DF 10 /* Direction Flag [C] */
#define X86_EFLAGS_OF 11 /* Overflow Flag [S] */
#define X86_EFLAGS_IOPL 12 /* I/O Privilege Level [X] */
#define X86_EFLAGS_IOPL_LO 12 /* I/O Privilege Level low bit [X] */
#define X86_EFLAGS_IOPL_HI 13 /* I/O Privilege Level high bit [X] */
#define X86_EFLAGS_NT 14 /* Nested Task [X] */
#define X86_EFLAGS_rsvd_15 15 /* Always clear [0] */
#define X86_EFLAGS_RF 16 /* Resume Flag [X] */
#define X86_EFLAGS_VM 17 /* Virtual-8086 Mode [X] */
#define X86_EFLAGS_AC 18 /* Alignment Check / Access Control [X] */
#define X86_EFLAGS_VIF 19 /* Virtual Interrupt Flag [X] */
#define X86_EFLAGS_VIP 20 /* Virtual Interrupt Pending [X] */
#define X86_EFLAGS_ID 21 /* ID Flag [X] */