RDSSPD/RDSSPQ - Read Shadow Stack Pointer

Opcode/ Instruction

Op/ En

64/32 bit Mode Support

CPUID Feature Flag

Description

F3 0F 1E /1 (mod=11) RDSSPD r32

R

V/V

CET_SS

Copy low 32 bits of shadow stack pointer (SSP) to r32.

F3 REX.W 0F 1E /1 (mod=11) RDSSPQ r64

R

V/N.E.

CET_SS

Copies shadow stack pointer (SSP) to r64.

Instruction Operand Encoding

Op/En

Operand 1

Operand 2

Operand 3

Operand 4

R

ModRM:r/m (w)

N/A

N/A

N/A

Description

Copies the current shadow stack pointer (SSP) register to the register destination. This opcode is a NOP when CET shadow stacks are not enabled and on processors that do not support CET.

Operation 

IF CPL = 3
   IF CR4.CET & IA32_U_CET.SH_STK_EN
       IF (operand size is 64 bit)
            THEN
                Dest := SSP;
            ELSE
                Dest := SSP[31:0];
       FI;
   FI;
ELSE
   IF CR4.CET & IA32_S_CET.SH_STK_EN
       IF (operand size is 64 bit)
            THEN
                Dest := SSP;
            ELSE
                Dest := SSP[31:0];
       FI;
   FI;
FI;

Flags Affected

None.

C/C++ Compiler Intrinsic Equivalent 

RDSSPD__int32 _rdsspd_i32(void);
RDSSPQ__int64 _rdsspq_i64(void);

Protected Mode Exceptions

None.

Real-Address Mode Exceptions

None.

Virtual-8086 Mode Exceptions

None.

Compatibility Mode Exceptions

None.

64-Bit Mode Exceptions

None.