--- title: "_drsys_sysnum_t Struct Reference" layout: default permalink: /struct__drsys__sysnum__t.html ---

Dr. Memory

Data Fields
_drsys_sysnum_t Struct Reference

`#include <drsyscall.h>`

## Data Fields
int | number
int | secondary

## Detailed Description

Representation of a system call number.

## Field Documentation

## ◆ number

int _drsys_sysnum_t::number

Either the sole system call number by itself (in which case `secondary` will be zero), or the primary component of a two-part system call number `number.secondary`.

For MacOS, whether 32-bit or 64-bit, we normalize the system call number to a positive integer with the top 8 bits set to 0x1 for a Mach system call, 0x3 for Machdep, and 0x0 for BSD (allowing the direct use of SYS_ constants). Access the raw eax register in the pre-syscall event to view the unmodified number, whose encoding varies depending on the bitwidth and interrupt vector used.

## ◆ secondary

int _drsys_sysnum_t::secondary

Secondary component of `number.secondary`, or zero.

The documentation for this struct was generated from the following file:

- drsyscall.h