IFSR32_EL2, Instruction Fault Status Register (EL2)

The IFSR32_EL2 characteristics are:

Purpose

Allows access to the AArch32 IFSR register from AArch64 state only. Its value has no effect on execution in AArch64 state.

Configuration

AArch64 System register IFSR32_EL2 bits [31:0] are architecturally mapped to AArch32 System register IFSR[31:0] .

If EL1 is AArch64 only, this register is UNDEFINED.

If EL2 is not implemented but EL3 is implemented, and EL1 is capable of using AArch32, then this register is not RES0.

This register has no effect if EL2 is not enabled in the current Security state.

RW fields in this register reset to architecturally UNKNOWN values.

Attributes

IFSR32_EL2 is a 64-bit register.

Field descriptions

The IFSR32_EL2 bit assignments are:

When TTBCR.EAE == 0:

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
RES0
RES0															FnV	RES0			ExT	RES0	FS[4]	LPAE	RES0					FS[3:0]

Bits [63:17]

Reserved, RES0.

FnV, bit [16]

FAR not Valid, for a synchronous External abort other than a synchronous External abort on a translation table walk.

This field is only valid for a synchronous External abort other than a synchronous External abort on a translation table walk. It is RES0 for all other Prefetch Abort exceptions.

This field resets to an architecturally UNKNOWN value.

Bits [15:13]

Reserved, RES0.

ExT, bit [12]

External abort type. This bit can be used to provide an IMPLEMENTATION DEFINED classification of External aborts.

In an implementation that does not provide any classification of External aborts, this bit is RES0.

For aborts other than External aborts this bit always returns 0.

This field resets to an architecturally UNKNOWN value.

Bit [11]

Reserved, RES0.

FS[4], bit [10]

This field is bit[4] of FS[4:0].

Fault Status bits. Bits [10] and [3:0] are interpreted together.

All other values are reserved.

When the RAS Extension is implemented, 0b11001, 0b11100, and 0b11110 are reserved.

The FS field is split as follows:

• FS[4] is IFSR32_EL2[10].
• FS[3:0] is IFSR32_EL2[3:0].

This field resets to an architecturally UNKNOWN value.

LPAE, bit [9]

On taking a Data Abort exception, this bit is set as follows:

Hardware does not interpret this bit to determine the behavior of the memory system, and therefore software can set this bit to 0 or 1 without affecting operation.

This field resets to an architecturally UNKNOWN value.

Bits [8:4]

Reserved, RES0.

FS[3:0], bits [3:0]

This field is bits[3:0] of FS[4:0].

See FS[4] for the field description.

When TTBCR.EAE == 1:

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
RES0
RES0															FnV	RES0			ExT	RES0		LPAE	RES0			STATUS
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
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

Bits [63:17]

Reserved, RES0.

FnV, bit [16]

FAR not Valid, for a synchronous External abort other than a synchronous External abort on a translation table walk.

This field is only valid for a synchronous External abort other than a synchronous External abort on a translation table walk. It is RES0 for all other Prefetch Abort exceptions.

This field resets to an architecturally UNKNOWN value.

Bits [15:13]

Reserved, RES0.

ExT, bit [12]

External abort type. This bit can be used to provide an IMPLEMENTATION DEFINED classification of External aborts.

In an implementation that does not provide any classification of External aborts, this bit is RES0.

For aborts other than External aborts this bit always returns 0.

This field resets to an architecturally UNKNOWN value.

Bits [11:10]

Reserved, RES0.

LPAE, bit [9]

On taking a Data Abort exception, this bit is set as follows:

Hardware does not interpret this bit to determine the behavior of the memory system, and therefore software can set this bit to 0 or 1 without affecting operation.

This field resets to an architecturally UNKNOWN value.

Bits [8:6]

Reserved, RES0.

STATUS, bits [5:0]

Fault status bits. All encodings not shown below are reserved:

All other values are reserved.

When the RAS Extension is implemented, 0b011000, 0b011101, 0b011110, and 0b011111, are reserved.

The lookup level associated with a fault is:

• For a fault generated on a translation table walk, the lookup level of the walk being performed.
• For a Translation fault, the lookup level of the translation table that gave the fault. If a fault occurs because a stage of address translation is disabled, or because the input address is outside the range specified by the appropriate base address register or registers, the fault is reported as a fault at level 1.
• For an Access flag fault, the lookup level of the translation table that gave the fault.
• For a Permission fault, including a Permission fault caused by hierarchical permissions, the lookup level of the final level of translation table accessed for the translation. That is, the lookup level of the translation table that returned a Block or Page descriptor.

This field resets to an architecturally UNKNOWN value.

if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && HCR_EL2.NV == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    else
        UNDEFINED;
elsif PSTATE.EL == EL2 then
    return IFSR32_EL2;
elsif PSTATE.EL == EL3 then
    return IFSR32_EL2;
              

if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && HCR_EL2.NV == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    else
        UNDEFINED;
elsif PSTATE.EL == EL2 then
    IFSR32_EL2 = X[t];
elsif PSTATE.EL == EL3 then
    IFSR32_EL2 = X[t];