OSLSR_EL1

AArch64 System register OSLSR_EL1 bits [31:0] are architecturally mapped to AArch32 System register DBGOSLSR[31:0].

Attributes

Field descriptions

Bits [63:4]

OSLM, bits [3, 0]

OS Lock model implemented. Identifies the form of OS save and restore mechanism implemented.

The value of this field is an IMPLEMENTATION DEFINED choice of:

OSLM	Meaning
0b00	OS Lock not implemented.
0b10	OS Lock implemented.

All other values are reserved. In an Armv8 implementation the value 0b00 is not permitted.

The OSLM field is split as follows:

OSLM[1] is OSLSR_EL1[3].
OSLM[0] is OSLSR_EL1[0].

Access to this field is RO.

nTT, bit [2]

Not 32-bit access. This bit is always RAZ. It indicates that a 32-bit access is needed to write the key to the OS Lock Access Register.

This field has an IMPLEMENTATION DEFINED value.

Access to this field is RO.

OSLK, bit [1]

OS Lock Status.

OSLK	Meaning
0b0	OS Lock unlocked.
0b1	OS Lock locked.

The OS Lock is locked and unlocked by writing to the OS Lock Access Register.

The reset behavior of this field is:

On a Cold reset, this field resets to 1.

Accessing OSLSR_EL1

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

MRS <Xt>, OSLSR_EL1

op0	op1	CRn	CRm	op2
0b10	0b000	0b0001	0b0001	0b100

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if HaveEL(EL3) && EL3SDDUndefPriority() && MDCR_EL3.TDOSA == '1' then UNDEFINED; elsif EL2Enabled() && IsFeatureImplemented(FEAT_FGT) && (!HaveEL(EL3) || SCR_EL3.FGTEn == '1') && HDFGRTR_EL2.OSLSR_EL1 == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif EL2Enabled() && MDCR_EL2.<TDE,TDOSA> != '00' then AArch64.SystemAccessTrap(EL2, 0x18); elsif HaveEL(EL3) && MDCR_EL3.TDOSA == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); else X[t, 64] = OSLSR_EL1; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && MDCR_EL3.TDOSA == '1' then UNDEFINED; elsif HaveEL(EL3) && MDCR_EL3.TDOSA == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); else X[t, 64] = OSLSR_EL1; elsif PSTATE.EL == EL3 then X[t, 64] = OSLSR_EL1;

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																												OSLM[1]	nTT	OSLK	OSLM[0]

OSLSR_EL1, OS Lock Status Register

Purpose

Configuration