모두의 코드
STAC (Intel x86/64 assembly instruction)
STAC
Set AC Flag in EFLAGS Register
참고 사항
아래 표를 해석하는 방법은 x86-64 명령어 레퍼런스 읽는 법 글을 참조하시기 바랍니다.
Opcode/ | Op / | 64/32 bit | CPUID | Description |
|---|---|---|---|---|
| NP | V/V | SMAP | Set the AC flag in the EFLAGS register. |
Instruction Operand Encoding
Op/En | Operand 1 | Operand 2 | Operand 3 | Operand 4 |
|---|---|---|---|---|
NP | NA | NA | NA | NA |
Description
Sets the AC flag bit in EFLAGS register. This may enable alignment checking of user-mode data accesses. This allows explicit supervisor-mode data accesses to user-mode pages even if the SMAP bit is set in the CR4 register.
This instruction's operation is the same in non-64-bit modes and 64-bit mode. Attempts to execute STAC when CPL > 0 cause #UD.
Operation
EFLAGS.AC <- 1;
Flags Affected
AC set. 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 STAC 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.
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