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# SP_EL0, Stack Pointer (EL0)

The SP_EL0 characteristics are:

## Purpose

Holds the stack pointer associated with EL0. At higher Exception levels, this is used as the current stack pointer when the value of SPSel.SP is 0.

## Configuration

There are no configuration notes.

## Attributes

SP_EL0 is a 64-bit register.

## Field descriptions

63 | 62 | 61 | 60 | 59 | 58 | 57 | 56 | 55 | 54 | 53 | 52 | 51 | 50 | 49 | 48 | 47 | 46 | 45 | 44 | 43 | 42 | 41 | 40 | 39 | 38 | 37 | 36 | 35 | 34 | 33 | 32
31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
Stack pointer
Stack pointer

#### Bits [63:0]

Stack pointer.

The reset behavior of this field is:

- On a Warm reset, this field resets to an architecturally UNKNOWN value.

## Accessing SP_EL0

When the value of PSTATE.SP is 0, this register is accessible at all Exception levels as the current stack pointer.

Accesses to this register use the following encodings in the System register encoding space:

#### MRS <Xt>, SP_EL0

op0 | op1 | CRn | CRm | op2
--- | --- | --- | --- | ---
0b11 | 0b000 | 0b0100 | 0b0001 | 0b000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if PSTATE.SP == '0' then UNDEFINED; else X[t, 64] = SP_EL0; elsif PSTATE.EL == EL2 then if PSTATE.SP == '0' then UNDEFINED; else X[t, 64] = SP_EL0; elsif PSTATE.EL == EL3 then if PSTATE.SP == '0' then UNDEFINED; else X[t, 64] = SP_EL0;

#### MSR SP_EL0, <Xt>

op0 | op1 | CRn | CRm | op2
--- | --- | --- | --- | ---
0b11 | 0b000 | 0b0100 | 0b0001 | 0b000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if PSTATE.SP == '0' then UNDEFINED; else SP_EL0 = X[t, 64]; elsif PSTATE.EL == EL2 then if PSTATE.SP == '0' then UNDEFINED; else SP_EL0 = X[t, 64]; elsif PSTATE.EL == EL3 then if PSTATE.SP == '0' then UNDEFINED; else SP_EL0 = X[t, 64];

AArch32 Registers | AArch64 Registers | AArch32 Instructions | AArch64 Instructions | Index by Encoding | External Registers | External Registers by Offset | Registers by Functional Group | Proprietary Notice

26/03/2024 09:49; 67c0ae5282a7629ba0ea0ba7267b43cd4f7939f6

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