SP_EL2, Stack Pointer (EL2)

The SP_EL2 characteristics are:

Purpose

Holds the capability stack pointer associated with EL2 and Executive state. When executing at EL2, the values of SPSel.SP and the Executive bit of PCC determine the current capability stack pointer:

SPSel.SPExecutive bit of PCCCurrent stack pointer
0bx0b0RSP_EL0
0b00b1SP_EL0
0b10b1SP_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 129-bit register.

Field descriptions

The SP_EL2 bit assignments are:

When Morello is implemented:

Bits [128:0]

Stack pointer

This field resets to an architecturally UNKNOWN value.

When Morello is not implemented:

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

op0op1CRnCRmop2
0b110b1100b01000b00010b000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then UNDEFINED; elsif PSTATE.EL == EL2 then UNDEFINED; elsif PSTATE.EL == EL3 then if IsFeatureImplemented("Morello") && IsInRestricted() && !Halted() then UNDEFINED; else return SP_EL2<63:0>;

MSR SP_EL2, <Xt>

op0op1CRnCRmop2
0b110b1100b01000b00010b000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then UNDEFINED; elsif PSTATE.EL == EL2 then UNDEFINED; elsif PSTATE.EL == EL3 then if IsFeatureImplemented("Morello") && IsInRestricted() && !Halted() then UNDEFINED; else SP_EL2 = ZeroExtend(X[t]);

MRS <Ct>, CSP_EL2

op0op1CRnCRmop2
0b110b1100b01000b00010b000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then UNDEFINED; elsif PSTATE.EL == EL2 then UNDEFINED; elsif PSTATE.EL == EL3 then if IsFeatureImplemented("Morello") && IsInRestricted() && !Halted() then UNDEFINED; elsif CPTR_EL3.EC == '0' then AArch64.SystemAccessTrap(EL3, 0x29); else return SP_EL2;

MSR CSP_EL2, <Ct>

op0op1CRnCRmop2
0b110b1100b01000b00010b000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then UNDEFINED; elsif PSTATE.EL == EL2 then UNDEFINED; elsif PSTATE.EL == EL3 then if IsFeatureImplemented("Morello") && IsInRestricted() && !Halted() then UNDEFINED; elsif CPTR_EL3.EC == '0' then AArch64.SystemAccessTrap(EL3, 0x29); else SP_EL2 = C[t];




12/01/2022 09:56; 05a4944b4b04e7ab50def8c126b479d22136f35b

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