Controls the Guarded Control Stack at EL2.
This register is present only when FEAT_GCS is implemented. Otherwise, direct accesses to GCSCR_EL2 are UNDEFINED.
If EL2 is not implemented, this register is RES0 from EL3.
GCSCR_EL2 is a 64-bit register.
| 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 |
| RES0 | |||||||||||||||||||||||||||||||
| RES0 | STREn | PUSHMEn | RES0 | EXLOCKEN | RVCHKEN | RES0 | PCRSEL | ||||||||||||||||||||||||
Reserved, RES0.
Execution of the following instructions are trapped:
| STREn | Meaning |
|---|---|
| 0b0 |
Execution of any of the specified instructions at EL2 cause a GCS exception. |
| 0b1 |
This control does not cause any instructions to be trapped. |
The reset behavior of this field is:
Trap GCSPUSHM instruction.
| PUSHMEn | Meaning |
|---|---|
| 0b0 |
Execution of a GCSPUSHM instruction at EL2 causes a Trap exception. |
| 0b1 |
This control does not cause any instructions to be trapped. |
The reset behavior of this field is:
Reserved, RES0.
Exception state lock.
Prevents MSR instructions from writing to ELR_EL2 or SPSR_EL2.
| EXLOCKEN | Meaning |
|---|---|
| 0b0 |
EL2 exception state locking disabled. |
| 0b1 |
EL2 exception state locking enabled. |
The reset behavior of this field is:
Return value check enable.
| RVCHKEN | Meaning |
|---|---|
| 0b0 |
Return value checking disabled at EL2. |
| 0b1 |
Return value checking enabled at EL2. |
The reset behavior of this field is:
Reserved, RES0.
Guarded Control Stack procedure call return enable selection.
| PCRSEL | Meaning |
|---|---|
| 0b0 |
Guarded Control Stack at EL2 is not PCR Selected. |
| 0b1 |
Guarded Control Stack at EL2 is PCR Selected. |
The reset behavior of this field is:
When the Effective value of HCR_EL2.E2H is 1, without explicit synchronization, accesses from EL2 using the register name GCSCR_EL2 or GCSCR_EL1 are not guaranteed to be ordered with respect to accesses using the other register name.
Accesses to this register use the following encodings in the System register encoding space:
MRS <Xt>, GCSCR_EL2
| op0 | op1 | CRn | CRm | op2 |
|---|---|---|---|---|
| 0b11 | 0b100 | 0b0010 | 0b0101 | 0b000 |
if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() IN {'xx1'} then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && SCR_EL3.GCSEn == '0' then UNDEFINED; elsif HaveEL(EL3) && SCR_EL3.GCSEn == '0' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); else X[t, 64] = GCSCR_EL2; elsif PSTATE.EL == EL3 then X[t, 64] = GCSCR_EL2;
MSR GCSCR_EL2, <Xt>
| op0 | op1 | CRn | CRm | op2 |
|---|---|---|---|---|
| 0b11 | 0b100 | 0b0010 | 0b0101 | 0b000 |
if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EffectiveHCR_EL2_NVx() IN {'xx1'} then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && SCR_EL3.GCSEn == '0' then UNDEFINED; elsif HaveEL(EL3) && SCR_EL3.GCSEn == '0' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); else GCSCR_EL2 = X[t, 64]; elsif PSTATE.EL == EL3 then GCSCR_EL2 = X[t, 64];
MRS <Xt>, GCSCR_EL1
| op0 | op1 | CRn | CRm | op2 |
|---|---|---|---|---|
| 0b11 | 0b000 | 0b0010 | 0b0101 | 0b000 |
if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if HaveEL(EL3) && EL3SDDUndefPriority() && SCR_EL3.GCSEn == '0' then UNDEFINED; elsif EL2Enabled() && IsFeatureImplemented(FEAT_FGT) && (!HaveEL(EL3) || SCR_EL3.FGTEn == '1') && HFGRTR_EL2.nGCS_EL1 == '0' then AArch64.SystemAccessTrap(EL2, 0x18); elsif HaveEL(EL3) && SCR_EL3.GCSEn == '0' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); elsif EffectiveHCR_EL2_NVx() == '111' then X[t, 64] = NVMem[0x8D0]; else X[t, 64] = GCSCR_EL1; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && SCR_EL3.GCSEn == '0' then UNDEFINED; elsif HaveEL(EL3) && SCR_EL3.GCSEn == '0' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); elsif ELIsInHost(EL2) then X[t, 64] = GCSCR_EL2; else X[t, 64] = GCSCR_EL1; elsif PSTATE.EL == EL3 then X[t, 64] = GCSCR_EL1;
MSR GCSCR_EL1, <Xt>
| op0 | op1 | CRn | CRm | op2 |
|---|---|---|---|---|
| 0b11 | 0b000 | 0b0010 | 0b0101 | 0b000 |
if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if HaveEL(EL3) && EL3SDDUndefPriority() && SCR_EL3.GCSEn == '0' then UNDEFINED; elsif EL2Enabled() && IsFeatureImplemented(FEAT_FGT) && (!HaveEL(EL3) || SCR_EL3.FGTEn == '1') && HFGWTR_EL2.nGCS_EL1 == '0' then AArch64.SystemAccessTrap(EL2, 0x18); elsif HaveEL(EL3) && SCR_EL3.GCSEn == '0' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); elsif EffectiveHCR_EL2_NVx() == '111' then NVMem[0x8D0] = X[t, 64]; else GCSCR_EL1 = X[t, 64]; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && SCR_EL3.GCSEn == '0' then UNDEFINED; elsif HaveEL(EL3) && SCR_EL3.GCSEn == '0' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); elsif ELIsInHost(EL2) then GCSCR_EL2 = X[t, 64]; else GCSCR_EL1 = X[t, 64]; elsif PSTATE.EL == EL3 then GCSCR_EL1 = X[t, 64];