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SP_EL1, Stack Pointer (EL1)

The SP_EL1 characteristics are:

Purpose

Holds the stack pointer associated with EL1. When executing at EL1, the value of SPSel.SP determines the current stack pointer:

SPSel.SPCurrent stack pointer
0b0SP_EL0
0b1SP_EL1

Configuration

RW fields in this register reset to architecturally UNKNOWN values.

Attributes

SP_EL1 is a 64-bit register.

Field descriptions

The SP_EL1 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_EL1

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 EL1 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_EL1

op0op1CRnCRmop2
0b110b1000b01000b00010b000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && HCR_EL2.<NV2,NV> == '11' then
        return NVMem[0x240];
    elsif EL2Enabled() && HCR_EL2.NV == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    else
        UNDEFINED;
elsif PSTATE.EL == EL2 then
    return SP_EL1;
elsif PSTATE.EL == EL3 then
    return SP_EL1;
              

MSR SP_EL1, <Xt>

op0op1CRnCRmop2
0b110b1000b01000b00010b000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && HCR_EL2.<NV2,NV> == '11' then
        NVMem[0x240] = X[t];
    elsif EL2Enabled() && HCR_EL2.NV == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    else
        UNDEFINED;
elsif PSTATE.EL == EL2 then
    SP_EL1 = X[t];
elsif PSTATE.EL == EL3 then
    SP_EL1 = X[t];
              


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