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System Calls

System calls (syscalls) are a type of KPC. They allow a process to ask Nova to perform a task.

Overview​

Syscalls are performed using CPU interruptions to notify Nova.

System calls always return two numbers: a 8-bit errcode and 8 bytes return value. If the errcode is not null, then an error occured during the syscall. Certain error codes indicate certain errors:

  • 0x00: cannot read syscall's code or arguments
  • 0x01: syscall does not exists
  • 0x02: at least one argument is invalid (e.g. providing a pointer to the 0 address)
  • 0x03: unmapped memory pointer
  • 0x04: memory permission error
  • 0x10 - 0x1F: invalid argument(s) provided
  • 0x20 - 0x2F: provided arguments are not valid in the current context (in relation with other arguments)
  • 0x30 - 0x3F: provided arguments are not valid (after resources checking)
  • 0x40 - 0x4F: resource access error
  • 0x50 - 0x5F: hardware errors
  • 0x60 - 0x6F: other types of errors

The codes of system calls are also categorized as follows:

  • 0x00 - 0x0F: signal handling
  • 0x10 - 0x1F: process management
  • 0x20 - 0x2F: pipes
  • 0x30 - 0x3F: memory management
  • 0x40 - 0x4F: process management
  • 0x50 - 0x5F: hardware interaction
  • TODO...

List of System Calls​

TODO