WRPKRU

WRPKRU — Write Data to User Page Key Register

Opcode*	Instruction	Op/ En	64/32bit Mode Support	CPUID Feature Flag	Description
NP 0F 01 EF	WRPKRU	ZO	V/V	OSPKE	Writes EAX into PKRU.

Instruction Operand Encoding

Op/En	Operand 1	Operand 2	Operand 3	Operand 4
ZO	NA	NA	NA	NA

Description

Writes the value of EAX into PKRU. ECX and EDX must be 0 when WRPKRU is executed; otherwise, a general- protection exception (#GP) occurs.

WRPKRU can be executed only if CR4.PKE = 1; otherwise, an invalid-opcode exception (#UD) occurs. Software can discover the value of CR4.PKE by examining CPUID.(EAX=07H,ECX=0H):ECX.OSPKE [bit 4].

On processors that support the Intel 64 Architecture, the high-order 32-bits of RCX, RDX and RAX are ignored.

Operation

IF (ECX = 0 AND EDX = 0) 
    THEN PKRU ← EAX;
    ELSE #GP(0); 
FI;

Flags Affected

None.

C/C++ Compiler Intrinsic Equivalent

WRPKRU:
void _wrpkru(uint32_t);

Protected Mode Exceptions

If ECX ≠ 0.

#GP(0) If EDX ≠ 0.

#UD If the LOCK prefix is used. If CR4.PKE = 0.

Real-Address Mode Exceptions

Same exceptions as in protected mode.

Virtual-8086 Mode Exceptions

Same exceptions as in protected mode.

Compatibility Mode Exceptions

Same exceptions as in protected mode.

64-Bit Mode Exceptions

Same exceptions as in protected mode.

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Source: Intel® Architecture Software Developer's Manual (May 2018)
Generated: 5-6-2018