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SP_EL2, Stack Pointer (EL2)

The SP_EL2 characteristics are:

Purpose

Holds the stack pointer associated with EL2. When executing at EL2, the value of SPSel. SP determines the current stack pointer:

SPSel.SPCurrent stack pointer
0b0SP_EL0
0b1SP_EL2

Configuration

This register has no effect if EL2 is not enabled in the current Security state.

RW fields in this register reset to architecturally UNKNOWN values.

Attributes

SP_EL2 is a 64-bit register.

Field descriptions

The SP_EL2 bit assignments are:

6362616059585756555453525150494847464544434241403938373635343332
Stack pointer
Stack pointer
313029282726252423222120191817161514131211109876543210

Bits [63:0]

Stack pointer.

This field resets to an architecturally UNKNOWN value.

Accessing the SP_EL2

This accessibility information only applies to accesses using the MRS or MSR instructions.

When the value of SPSel.SP is 1, this register is also accessible at EL2 as the current stack pointer.

Note

When the value of SPSel.SP is 0, SP_EL0 is used as the current stack pointer at all Exception levels.

Accesses to this register use the following encodings:

MRS <Xt>, SP_EL2

op0CRnop1op2CRm
0b110b01000b1100b0000b0001
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    UNDEFINED;
elsif PSTATE.EL == EL2 then
    UNDEFINED;
elsif PSTATE.EL == EL3 then
    return SP_EL2;
              

MSR SP_EL2, <Xt>

op0CRnop1op2CRm
0b110b01000b1100b0000b0001
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    UNDEFINED;
elsif PSTATE.EL == EL2 then
    UNDEFINED;
elsif PSTATE.EL == EL3 then
    SP_EL2 = X[t];
              


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