GCSSS2 -- A64

GCSSS2

Guarded Control Stack switch stack 2

This instruction validates that the most recent entry of the Guarded Control Stack being switched to contains an In-progress GCS cap record, stores a Valid GCS cap record to the Guarded Control Stack that is being switched from, and sets Xt to the Guarded Control Stack pointer that is being switched from.

For more information, see GCSSS2, Guarded Control Stack Switch Stack 2.

This is an alias of SYSL. This means:

The encodings in this description are named to match the encodings of SYSL.
The description of SYSL gives the operational pseudocode, any constrained unpredictable behavior, and any operational information for this instruction.

System
(FEAT_GCS)

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
1	1	0	1	0	1	0	1	0	0	1	0	1	0	1	1	0	1	1	1	0	1	1	1	0	1	1	Rt
										L			op1			CRn				CRm				op2

Encoding

GCSSS2 <Xt>

is equivalent to

SYSL <Xt>, #3, C7, C7, #3

and is always the preferred disassembly.

Assembler Symbols

<Xt>	Is the 64-bit name of the general-purpose destination register, encoded in the "Rt" field.

Operation

The description of SYSL gives the operational pseudocode for this instruction.

2026-03_rel 2026-03-26 20:48:11

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
1	1	0	1	0	1	0	1	0	0	1	0	1	0	1	1	0	1	1	1	0	1	1	1	0	1	1	Rt
										L			op1			CRn				CRm				op2

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
1	1	0	1	0	1	0	1	0	0	1	0	1	0	1	1	0	1	1	1	0	1	1	1	0	1	1	Rt
										L			op1			CRn				CRm				op2

GCSSS2

System(FEAT_GCS)

Encoding

Assembler Symbols

Operation

System
(FEAT_GCS)

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
1	1	0	1	0	1	0	1	0	0	1	0	1	0	1	1	0	1	1	1	0	1	1	1	0	1	1	Rt
										L			op1			CRn				CRm				op2