Generating Syscalls

While not common, there are situations where you might need to regenerate syscalls. Fortunately, Apple provides a convenient perl script called The script is located in [XNU]/libsyscall/xcodescripts/.

Understanding's Arugments

When you try to run the command, without any arguments, you will get the following prompt:

Usage: syscalls.master custom-directory platforms-directory platform-name out-directory

Unfortunately, the prompt does not give a lot of helpful information. Below is a breakdown of what the script is requesting.

  • syscalls.master - Point to the syscalls.master file. ex: [XNU]/bsd/kern/syscalls.master
  • custom-directory - Point to a directory that contains a SYS.h, custom.s, and a list of __ files. These files can be found in a folder called custom. ex:[XNU]/libsyscall/custom/
  • platforms-directory- Point to a directory that contains the files. Ex:[XNU]/libsyscall/Platforms/
  • platform-name - One of the platform names that are in the platform directory. ex: MacOSX

In addition, you will need to define the list of ARCHS that the tool should generate.

export ARCHS="arm64 i386 x86_64"


export ARCHS="arm64 i386 x86_64"
mkdir ~/Desktop/generated_syscalls
./ $XNU/bsd/kern/syscalls.master $XNU/libsyscall/custom/ $XNU/libsyscall/Platforms/ MacOSX ~/Desktop/generated_syscalls