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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.SP | Current stack pointer |
|---|---|
| 0b0 | SP_EL0 |
| 0b1 | SP_EL1 |
Configuration
There are no configuration notes.
Attributes
SP_EL1 is a 64-bit register.
Field descriptions
The SP_EL1 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_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
| op0 | op1 | CRn | CRm | op2 |
|---|---|---|---|---|
| 0b11 | 0b100 | 0b0100 | 0b0001 | 0b000 |
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>
| op0 | op1 | CRn | CRm | op2 |
|---|---|---|---|---|
| 0b11 | 0b100 | 0b0100 | 0b0001 | 0b000 |
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];