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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.SP | Current stack pointer |
|---|---|
| 0b0 | SP_EL0 |
| 0b1 | SP_EL2 |
Configuration
This register has no effect if EL2 is not enabled in the current Security state.
Attributes
SP_EL2 is a 64-bit register.
Field descriptions
The SP_EL2 bit assignments are:
| 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 |
| Stack pointer | |||||||||||||||||||||||||||||||
| Stack pointer | |||||||||||||||||||||||||||||||
| 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 |
Bits [63:0]
Stack pointer.
On a Warm reset, 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
| op0 | op1 | CRn | CRm | op2 |
|---|---|---|---|---|
| 0b11 | 0b110 | 0b0100 | 0b0001 | 0b000 |
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>
| op0 | op1 | CRn | CRm | op2 |
|---|---|---|---|---|
| 0b11 | 0b110 | 0b0100 | 0b0001 | 0b000 |
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];