RNDRRS, Random Number Full Entropy

The RNDRRS characteristics are:

Purpose

Random Number with fresh full entropy. Returns a 64-bit random number from an approved Random Bit Generator, using either a Non-deterministic Random Bit Generator or one where the Deterministic Random Bit Generator is reseeded, where possible, from an approved entropy source before the return of the random number. See 'Properties of the generated random number'.

If the hardware returns a genuine random number, PSTATE.NZCV is set to 0b0000.

If the instruction cannot return a genuine random number in a reasonable period of time, PSTATE.NZCV is set to 0b0100 and the data value returned is 0.

When FEAT_RNG_TRAP is implemented and SCR_EL3.TRNDR is 1, reads of this register are trapped to EL3.

Configuration

This register is present only when FEAT_RNG is implemented or FEAT_RNG_TRAP is implemented. Otherwise, direct accesses to RNDRRS are UNDEFINED.

Attributes

RNDRRS is a 64-bit register.

Field descriptions

6362616059585756555453525150494847464544434241403938373635343332
313029282726252423222120191817161514131211109876543210
RNDRRS
RNDRRS

RNDRRS, bits [63:0]

Random Number with fresh full entropy. Returns a 64-bit random number from an approved Random Bit Generator, using either a Non-deterministic Random Bit Generator or one where the Deterministic Random Bit Generator is reseeded, where possible, from an approved entropy source before the return of the random number. See 'Properties of the generated random number'.

The reset behavior of this field is:

Accessing RNDRRS

Accesses to this register use the following encodings in the System register encoding space:

MRS <Xt>, RNDRRS

op0op1CRnCRmop2
0b110b0110b00100b01000b001

if PSTATE.EL == EL0 then if IsFeatureImplemented(FEAT_RNG_TRAP) && SCR_EL3.TRNDR == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); elsif !IsFeatureImplemented(FEAT_RNG) then UNDEFINED; else X[t, 64] = RNDRRS; elsif PSTATE.EL == EL1 then if IsFeatureImplemented(FEAT_RNG_TRAP) && SCR_EL3.TRNDR == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); elsif !IsFeatureImplemented(FEAT_RNG) then UNDEFINED; else X[t, 64] = RNDRRS; elsif PSTATE.EL == EL2 then if IsFeatureImplemented(FEAT_RNG_TRAP) && SCR_EL3.TRNDR == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); elsif !IsFeatureImplemented(FEAT_RNG) then UNDEFINED; else X[t, 64] = RNDRRS; elsif PSTATE.EL == EL3 then if IsFeatureImplemented(FEAT_RNG_TRAP) && SCR_EL3.TRNDR == '1' then AArch64.SystemAccessTrap(EL3, 0x18); elsif !IsFeatureImplemented(FEAT_RNG) then UNDEFINED; else X[t, 64] = RNDRRS;


26/03/2024 09:49; 67c0ae5282a7629ba0ea0ba7267b43cd4f7939f6

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