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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
The SP_EL0 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_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:
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
return SP_EL0;
elsif PSTATE.EL == EL2 then
if PSTATE.SP == '0' then
UNDEFINED;
else
return SP_EL0;
elsif PSTATE.EL == EL3 then
if PSTATE.SP == '0' then
UNDEFINED;
else
return 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];
elsif PSTATE.EL == EL2 then
if PSTATE.SP == '0' then
UNDEFINED;
else
SP_EL0 = X[t];
elsif PSTATE.EL == EL3 then
if PSTATE.SP == '0' then
UNDEFINED;
else
SP_EL0 = X[t];