User Access Override
Allows access to the User Access Override bit.
This register is present only when FEAT_UAO is implemented and FEAT_AA64 is implemented. Otherwise, direct accesses to UAO are UNDEFINED.
UAO 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 | UAO | RES0 | |||||||||||||||||||||||||||||
Reserved, RES0.
User Access Override.
| UAO | Meaning |
|---|---|
| 0b0 |
The behavior of LDTR* and STTR* instructions is as defined in the base Armv8 architecture. |
| 0b1 | When executed at the following Exception levels, LDTR* and STTR* instructions behave as the equivalent LDR* and STR* instructions:
|
When executed at EL3, or at EL2 when the Effective value of HCR_EL2.{E2H, TGE} is not {1, 1}, the LDTR* and STTR* instructions behave as the equivalent LDR* and STR* instructions, regardless of the setting of the PSTATE.UAO bit.
Reserved, RES0.
For more information about the operation of the MSR (immediate) accessor, see 'MSR (immediate)'.
Accesses to this register use the following encodings in the System register encoding space:
MRS <Xt>, UAO
(op0 = 0b11, op1 = 0b000, CRn = 0b0100, CRm = 0b0010, op2 = 0b100)
if !(IsFeatureImplemented(FEAT_UAO) && IsFeatureImplemented(FEAT_AA64)) then UNDEFINED; elsif PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then X[t, 64] = Zeros(40):PSTATE.UAO:Zeros(23); elsif PSTATE.EL == EL2 then X[t, 64] = Zeros(40):PSTATE.UAO:Zeros(23); elsif PSTATE.EL == EL3 then X[t, 64] = Zeros(40):PSTATE.UAO:Zeros(23);
MSR UAO, <Xt>
(op0 = 0b11, op1 = 0b000, CRn = 0b0100, CRm = 0b0010, op2 = 0b100)
if !(IsFeatureImplemented(FEAT_UAO) && IsFeatureImplemented(FEAT_AA64)) then UNDEFINED; elsif PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then PSTATE.UAO = X[t, 64]<23>; elsif PSTATE.EL == EL2 then PSTATE.UAO = X[t, 64]<23>; elsif PSTATE.EL == EL3 then PSTATE.UAO = X[t, 64]<23>;
MSR UAO, #<imm>
(op0 = 0b00, op1 = 0b000, CRn = 0b0100, op2 = 0b011)
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