RNDR

Random Number. Returns a 64-bit random number which is reseeded from the True Random Number source at an IMPLEMENTATION DEFINED rate.

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.

Configuration

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

Attributes

Field descriptions

RNDR, bits [63:0]

Random Number. Returns a 64-bit Random Number which is reseeded from the True Random Number source at an IMPLEMENTATION DEFINED rate.

The reset behavior of this field is:

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

Accessing RNDR

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

MRS <Xt>, RNDR

op0	op1	CRn	CRm	op2
0b11	0b011	0b0010	0b0100	0b000

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

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
RNDR
RNDR