SYSCALL — System Call

Instruction Word

Slot
Inst
6
3
6
2
6
1
6
0
5
9
5
8
5
7
5
6
5
5
5
4
5
3
5
2
5
1
5
0
4
9
4
8
4
7
4
6
4
5
4
4
4
3
4
2
4
1
4
0
3
9
3
8
3
7
3
6
3
5
3
4
3
3
3
2
3
1
3
0
2
9
2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
1
9
1
8
1
7
1
6
1
5
1
4
1
3
1
2
1
1
1
0
9876543210
Format x24 - 24 bit(s) 0
SYSCALL 000000000101000000000000

Assembler Syntax

SYSCALL

C Syntax

#include <xtensa/tie/xt_exceptions.h>

extern void XT_SYSCALL(void);

Description

(please consult the Xtensa ® Instruction Set Architecture Reference Manual for any cross references and additional information)

When executed, the SYSCALL instruction raises a system-call exception, redirecting execution to an exception vector . Therefore, SYSCALL instructions never complete. EPC[1] contains the address of the SYSCALL and ICOUNT is not incremented. The system call handler should add 3 to EPC[1] before returning from the exception to continue execution.

The program may pass parameters to the system-call handler in the registers. There are no bits in SYSCALL instruction reserved for this purpose. See System Calls for a description of software conventions for system call parameters.

Operation

Exception (SyscallCause)

Exceptions

EveryInst Group (see EveryInst Group:)GenExcep(SyscallCause) if Exception Option

Protos that use SYSCALL

proto SYSCALL { }{}{
SYSCALL;
}