The GCR_EL1 characteristics are:
Tag Control Register.
This register is present only when ARMv8.5-MemTag is implemented. Otherwise, direct accesses to GCR_EL1 are UNDEFINED.
RW fields in this register reset to architecturally UNKNOWN values.
GCR_EL1 is a 64-bit register.
The GCR_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 |
RES0 | |||||||||||||||||||||||||||||||
RES0 | RRND | Exclude | |||||||||||||||||||||||||||||
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 |
Reserved, RES0.
Controls whether RandomTag() generates a deterministic value solely based on the contents of RGSR_EL1, or a non-deterministic value.
RRND | Meaning |
---|---|
0b0 |
Generate a deterministic value based on RGSR_EL1. |
0b1 |
Generate an IMPLEMENTATION DEFINED non-deterministic value. |
When the value of GCR_EL1.RRND is 1, the value generated does not need to be cryptographically random.
A similar algorithm to that used when RRND=0 but with free running clock is sufficient.
This field resets to an architecturally UNKNOWN value.
Allocation Tag values excluded from selection by ChooseNonExcludedTag().
This field resets to an architecturally UNKNOWN value.
Accesses to this register use the following encodings:
op0 | op1 | CRn | CRm | op2 |
---|---|---|---|---|
0b11 | 0b000 | 0b0001 | 0b0000 | 0b110 |
if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.ATA == '0' then AArch64.SystemAccessTrap(EL2, 0x18); elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && SCR_EL3.ATA == '0' then AArch64.SystemAccessTrap(EL3, 0x18); else return GCR_EL1; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && !ELUsingAArch32(EL3) && SCR_EL3.ATA == '0' then AArch64.SystemAccessTrap(EL3, 0x18); else return GCR_EL1; elsif PSTATE.EL == EL3 then return GCR_EL1;
op0 | op1 | CRn | CRm | op2 |
---|---|---|---|---|
0b11 | 0b000 | 0b0001 | 0b0000 | 0b110 |
if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.ATA == '0' then AArch64.SystemAccessTrap(EL2, 0x18); elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && SCR_EL3.ATA == '0' then AArch64.SystemAccessTrap(EL3, 0x18); else GCR_EL1 = X[t]; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && !ELUsingAArch32(EL3) && SCR_EL3.ATA == '0' then AArch64.SystemAccessTrap(EL3, 0x18); else GCR_EL1 = X[t]; elsif PSTATE.EL == EL3 then GCR_EL1 = X[t];
27/03/2019 21:59; e5e4db499bf9867a4b93324c4dbac985d3da9376
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