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RNDRRS, Reseeded Random Number

The RNDRRS characteristics are:

Purpose

Reseeded Random Number. Returns a 64-bit random number which is reseeded from the True Random Number source immediately before the read of the 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.

RNDRRS is a read-only register.

Configuration

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

Attributes

RNDRRS is a 64-bit register.

Field descriptions

The RNDRRS bit assignments are:

6362616059585756555453525150494847464544434241403938373635343332
RNDRRS
RNDRRS
313029282726252423222120191817161514131211109876543210

RNDRRS, bits [63:0]

Reseeded Random Number. Returns a 64-bit Random Number which is reseeded from the True Random Number source immediately before this read.

On a Warm reset, this field resets to an architecturally UNKNOWN value.

Accessing the RNDRRS

Accesses to this register use the following encodings:

MRS <Xt>, RNDRRS

op0op1CRnCRmop2
0b110b0110b00100b01000b001
if PSTATE.EL == EL0 then
    return RNDRRS;
elsif PSTATE.EL == EL1 then
    return RNDRRS;
elsif PSTATE.EL == EL2 then
    return RNDRRS;
elsif PSTATE.EL == EL3 then
    return RNDRRS;