Test-case kernel

#include <stddef.h>
#include <stdint.h>

// kernel.cpp

char *vidptr = (char*)0xb8000; 	//video mem begins here.
unsigned int current_loc = 0;

void print(const char* str)
{
	unsigned int j = 0;

	/* this loop writes the string to video memory */
	while(str[j] != '\0') {
		/* the character's ascii */
		vidptr[current_loc] = str[j];
		/* attribute-byte: give character black bg and light grey fg */
		vidptr[current_loc+1] = 0x07;
		++j;
		current_loc += 2;
	}
}

void port_out8(uint16_t _port, uint8_t _value)
{
	asm volatile ("outb %0, %1" : : "a"(_value), "Nd"(_port));
}

void port_out16(uint16_t _port, uint16_t _value)
{
	asm volatile ("outw %0, %1" : : "a"(_value), "Nd"(_port));
}

void port_out32(uint16_t _port, uint32_t _value)
{
	asm volatile ("outl %0, %1" : : "a"(_value), "Nd"(_port));
}

uint8_t port_in8(uint16_t _port)
{
	uint8_t ret;
	asm volatile ("inb %1, %0" : "=a"(ret) : "Nd"(_port));
	return ret;
}

uint16_t port_in16(uint16_t _port)
{
	uint16_t ret;
	asm volatile ("inw %1, %0" : "=a"(ret) : "Nd"(_port));
	return ret;
}

uint32_t port_in32(uint16_t _port)
{
	uint32_t ret;
	asm volatile ("inl %1, %0" : "=a"(ret) : "Nd"(_port));
	return ret;
}

#define write_port port_out8
#define read_port port_in8

void kb_init(void)
{
	/* 0xFD is 11111101 - enables only IRQ1 (keyboard)*/
	write_port(0x21 , 0xFD);
	print("Keyboard enabled");
}


struct IDT_entry
{
	unsigned short int offset_lowerbits;
	unsigned short int selector;
	unsigned char zero;
	unsigned char type_attr;
	unsigned short int offset_higherbits;
};

#define IDT_SIZE 256
IDT_entry IDT[IDT_SIZE];

extern "C" void keyboard_handler();

asm volatile("keyboard_handler: \n call keyboard_handler_main \n iret");

unsigned long idt_ptr[2];

void idt_init(void)
{
	unsigned long keyboard_address;
	unsigned long idt_address;

	/* populate IDT entry of keyboard's interrupt */
	keyboard_address = (unsigned long)keyboard_handler;
	IDT[0x21].offset_lowerbits = keyboard_address & 0xffff;
	IDT[0x21].selector = 0x08; /* KERNEL_CODE_SEGMENT_OFFSET */
	IDT[0x21].zero = 0;
	IDT[0x21].type_attr = 0x8e; /* INTERRUPT_GATE */
	IDT[0x21].offset_higherbits = (keyboard_address & 0xffff0000) >> 16;


	/*     Ports
	*	 PIC1	PIC2
	*Command 0x20	0xA0
	*Data	 0x21	0xA1
	*/

	/* ICW1 - begin initialization */
	write_port(0x20 , 0x11);
	write_port(0xA0 , 0x11);

	/* ICW2 - remap offset address of IDT */
	/*
	* In x86 protected mode, we have to remap the PICs beyond 0x20 because
	* Intel have designated the first 32 interrupts as "reserved" for cpu exceptions
	*/
	write_port(0x21 , 0x20);
	write_port(0xA1 , 0x28);

	/* ICW3 - setup cascading */
	write_port(0x21 , 0x00);
	write_port(0xA1 , 0x00);

	/* ICW4 - environment info */
	write_port(0x21 , 0x01);
	write_port(0xA1 , 0x01);
	/* Initialization finished */

	/* mask interrupts */
	write_port(0x21 , 0xff);
	write_port(0xA1 , 0xff);

	/* fill the IDT descriptor */
	idt_address = (unsigned long)IDT ;
	idt_ptr[0] = (sizeof (struct IDT_entry) * IDT_SIZE) + ((idt_address & 0xffff) << 16);
	idt_ptr[1] = idt_address >> 16 ;

	//load_idt(idt_ptr);
	asm volatile ("lidt ((idt_ptr)) \n sti");
	print("Initiated IDT");
}

extern "C" void kmain(void)
{
	const char *str = "Welcome to Luna!";

	/* this loops clears the screen
	* there are 25 lines each of 80 columns; each element takes 2 bytes */
	int j = 0;
	while(j < 80 * 25 * 2) {
		/* blank character */
		vidptr[j] = ' ';
		/* attribute-byte - light grey on black screen */
		vidptr[j+1] = 0x07;
		j = j + 2;
	}

	print(str);

	idt_init();
	kb_init();

	while (true) { asm volatile ("hlt"); }

	return;
}


extern "C" void keyboard_handler_main(void) {
	unsigned char status;
	char keycode;

	/* write EOI */
	write_port(0x20, 0x20);

	//print("K");

	status = read_port(0x60);//KEYBOARD_STATUS_PORT);
	/* Lowest bit of status will be set if buffer is not empty */
	if (status & 0x01 || true) {
		keycode = read_port(0x60);//KEYBOARD_DATA_PORT);
		if(keycode < 0)
			return;
		vidptr[current_loc++] = "!!1234567890-=!!qwertyuiop[]!!asdfghjkl;'#!\\zxcvbnm,./!!! !FFFFFFFFFF!"[keycode];//'a';// + keycode;//keyboard_map[keycode];
		vidptr[current_loc++] = 0x07;
	}
}