SYSCALL

Operation

Raise the SYSTEM_CALL architectural event.

Assembler Syntax

SYSCALL

Privilege

Unprivileged

Raise the explicit synchronous SYSTEM_CALL event (0x00000003), saving the following instruction as UPC and entering the common EPC/ECS/EDS event handler on SSS:SSP without a memory frame.

Execution is valid only in user mode with no active architectural event. It selects the explicit synchronous SYSTEM_CALL event, whose event code is 0x00000003, priority is 4, frame class is BASIC, and saved PC is the following instruction.

On successful entry the common event mechanism atomically saves the user continuation in UPC, USP, UCS, UDS, USS, UCTL, and UINFO; loads CS, DS, and PC from ECS, EDS, and EPC; selects SSS:SSP; and sets STATUS.PM, STATUS.EA, STATUS.EDEPTH=1, and STATUS.UO. Because SYSTEM_CALL has no payload, entry performs no stack-memory access. Return uses ERET. Software restarts the one-byte instruction by subtracting one from UPC before ERET.

2.75in

Encodings

SYSCALL

Format: Instruction format for SYSCALL