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SPSel, Stack Pointer Select
The SPSel characteristics are:
Purpose
Allows the Stack Pointer to be selected between SP_EL0 and SP_ELx.
Configuration
There are no configuration notes.
Attributes
SPSel is a 64-bit register.
Field descriptions
The SPSel 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 |
| RES0 | |||||||||||||||||||||||||||||||
| RES0 | SP | ||||||||||||||||||||||||||||||
| 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 [63:1]
Reserved, RES0.
SP, bit [0]
Stack pointer to use. Possible values of this bit are:
| SP | Meaning |
|---|---|
| 0b0 |
Use SP_EL0 at all Exception levels. |
| 0b1 |
Use SP_ELx for Exception level ELx. |
This field resets to 1.
Accessing the SPSel
Accesses to this register use the following encodings:
MRS <Xt>, SPSel
| op0 | op1 | CRn | CRm | op2 |
|---|---|---|---|---|
| 0b11 | 0b000 | 0b0100 | 0b0010 | 0b000 |
if PSTATE.EL == EL0 then
UNDEFINED;
elsif PSTATE.EL == EL1 then
return Zeros(63):PSTATE.SP;
elsif PSTATE.EL == EL2 then
return Zeros(63):PSTATE.SP;
elsif PSTATE.EL == EL3 then
return Zeros(63):PSTATE.SP;
MSR SPSel, <Xt>
| op0 | op1 | CRn | CRm | op2 |
|---|---|---|---|---|
| 0b11 | 0b000 | 0b0100 | 0b0010 | 0b000 |
if PSTATE.EL == EL0 then
UNDEFINED;
elsif PSTATE.EL == EL1 then
PSTATE.SP = X[t]<0>;
elsif PSTATE.EL == EL2 then
PSTATE.SP = X[t]<0>;
elsif PSTATE.EL == EL3 then
PSTATE.SP = X[t]<0>;
MSR SPSel, #<imm>
| op0 | op1 | CRn | op2 |
|---|---|---|---|
| 0b00 | 0b000 | 0b0100 | 0b101 |