MTGos Syscalls

MTGos Syscalls is the method of requesting system resources under MTGos.

Basics

It is based around C++ Objects and a set of Syscalls can be expressed as one Object.

List of Objects

Name	Object ID	Description
ScreenOut	0	interface to various screen-based output functions
Keyboard	1	interface to both raw and translated Keyboard input
Serial	2	i/o interface for a serial interface
Disk	3	Raw disk i/o interface. Dangerous.
MM	4	interface to request memory from the system

More objects may be added as MTGos evolves

ScreenOut

class ScreenOut {
    public:
        ScreenOut(bool err);
        auto operator <<(string) -> Screen &; // puts(char *)
        auto clrscr() -> Screen &;
        auto setColor(BGColor, FGColor) -> Screen &;
        ~ScreenOut();
};

Notes: The output function is not ANSI-Escape-Sequence compatible.

Keyboard

class Keyboard {
    public:
        Keyboard();
        auto operator >>(char &) -> Screen &; // getc()
        auto operator >>(string &) -> Screen &; // gets an entire line
        auto getKeyCode() -> uint32_t; // gets a RAW keycode
        ~Keyboard();
};

Note: RAW keycodes might be different per-model and per-architecture.

Serial

class Serial {
    public:
        Serial();
        auto operator <<(string) -> Screen &; // puts(char *)
        auto operator >>(char &) -> Screen &; // getc()
        auto operator >>(string &) -> Screen &; // gets an entire line
        ~Serial();
};

Note: The serial connection might silently fail. If no new character is got after 500 attempts, '\0' is returned.

Disk

class Disk {
    public:
        Disk(char * diskName);
        auto readSector(uint64_t sectorNum, uint8_t buf[512]) -> Disk &;
        auto writeSector(uint64_t sectorNum, uint8_t buf[512]) -> Disk &;
        ~Disk();
};

Note: A sector is 512 bytes in size.

MM

class MM {
    public:
        MM();
        auto getPage() -> void *;
        auto freePage(void*) -> void;
        ~MM();
};

Note: A page is 4KiB in size.

Calling Convention

The first register is the syscall number. The syscall number is an at least 32-bit big register built the following way:

OOOO OOOO OOOO OOOO SSSS SSSS SSSS SSSS

where O is the object number and S the subnumber.

The subnumber is the function number in the given object. The constructor is always 0x0000 and the deconstructor always 0xFFFF.

All arguments are pushed onto the stack.
All return values replace the value of the first register.
The second register contains the "Handle" returned from the constructor syscall.
The constructor syscall ignores the Handle register and will not change it.

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