commit 7caa808d2a4d0445f97db3fc4e2af1ba8f1cbe9d
Author: Mika Westphal <westphal@univention.de>
Date:   Thu Jan 19 19:35:53 2023 +0100

    Init

diff --git a/.gdb_history b/.gdb_history
new file mode 100644
index 0000000..89a021a
--- /dev/null
+++ b/.gdb_history
@@ -0,0 +1,27 @@
+remote localhost:1234
+target remote localhost:1234
+kill
+target remote localhost:1234
+symbol-file build/kernel
+symbol-file build/kernel.elf 
+d main
+disassemble main
+list
+p VGA
+p *(VGA)
+b _ZN3VGA20terminal_writestringEPKc
+n
+line
+list
+n
+list
+c
+list
+b VGA::linebreak
+c
+c
+c
+d VGA::linebreak
+disassemble VGA::linebreak
+list
+list VGA::linebreak
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..d3bf705
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,38 @@
+LINKFILE=linker.ld
+QEMU=qemu-system-i386
+BUILDPATH=build
+SOURCEPATH=src
+CC=i686-elf-g++
+CFLAGS=-m32 -c -Wmultichar -ffreestanding -O2 -Wall -Wextra -fno-exceptions -fno-rtti -Wwrite-strings -fpermissive -g
+#OBJ=$(BUILDPATH)/boot.o $(BUILDPATH)/kernel.o $(BUILDPATH)/kernel/vga.o $(BUILDPATH)/kernel/keyboard.o $(BUILDPATH)/kernel/idt.o
+OBJ=$(BUILDPATH)/boot.o $(BUILDPATH)/kernel.o $(BUILDPATH)/kernel/vga.o
+ASMC=i686-elf-as
+LD=ld
+LDFLAGS=-m elf_i386 -T $(LINKFILE) -z muldefs -g
+
+all: $(BUILDPATH)/kernel.elf
+	$(QEMU) -kernel $(BUILDPATH)/kernel.elf
+
+debug: $(BUILDPATH)/kernel.elf
+	$(QEMU) -s -S -kernel $(BUILDPATH)/kernel.elf
+
+$(BUILDPATH)/boot.o: $(SOURCEPATH)/boot.asm
+	$(ASMC) $(SOURCEPATH)/boot.asm -o $(BUILDPATH)/boot.o
+
+$(BUILDPATH)/kernel.o: $(SOURCEPATH)/kernel.*
+	$(CC) $(CFLAGS) $(SOURCEPATH)/kernel.cpp -o $(BUILDPATH)/kernel.o
+
+$(BUILDPATH)/kernel/vga.o: $(SOURCEPATH)/kernel/vga.*
+	$(CC) $(CFLAGS) $(SOURCEPATH)/kernel/vga.cpp -o $(BUILDPATH)/kernel/vga.o
+
+$(BUILDPATH)/kernel/keyboard.o: $(SOURCEPATH)/kernel/keyboard.* $(BUILDPATH)/boot.o
+	$(CC) $(CFLAGS) $(SOURCEPATH)/kernel/keyboard.cpp -o $(BUILDPATH)/kernel/keyboard.o
+
+$(BUILDPATH)/kernel/idt.o: $(SOURCEPATH)/kernel/idt.* $(BUILDPATH)/boot.o
+	$(CC) $(CFLAGS) $(SOURCEPATH)/kernel/idt.cpp -o $(BUILDPATH)/kernel/idt.o
+
+$(BUILDPATH)/kernel.elf: $(OBJ)
+	$(LD) $(LDFLAGS) -o $(BUILDPATH)/kernel.elf $(OBJ)
+
+clean:
+	rm $(OBJ)
diff --git a/build/boot.o b/build/boot.o
new file mode 100644
index 0000000..3fd271c
Binary files /dev/null and b/build/boot.o differ
diff --git a/build/kernel.elf b/build/kernel.elf
new file mode 100755
index 0000000..dc420cd
Binary files /dev/null and b/build/kernel.elf differ
diff --git a/build/kernel.o b/build/kernel.o
new file mode 100644
index 0000000..008c1c6
Binary files /dev/null and b/build/kernel.o differ
diff --git a/build/kernel/vga.o b/build/kernel/vga.o
new file mode 100644
index 0000000..35f3947
Binary files /dev/null and b/build/kernel/vga.o differ
diff --git a/linker.ld b/linker.ld
new file mode 100644
index 0000000..53f4129
--- /dev/null
+++ b/linker.ld
@@ -0,0 +1,26 @@
+ENTRY(_start)
+SECTIONS
+{
+	. = 1M;
+	.text BLOCK(4K) : ALIGN(4K)
+	{
+		*(.multiboot)
+		*(.text)
+	}
+ 
+	.rodata BLOCK(4K) : ALIGN(4K)
+	{
+		*(.rodata)
+	}
+ 
+	.data BLOCK(4K) : ALIGN(4K)
+	{
+		*(.data)
+	}
+ 
+	.bss BLOCK(4K) : ALIGN(4K)
+	{
+		*(COMMON)
+		*(.bss)
+	}
+}
diff --git a/src/boot.asm b/src/boot.asm
new file mode 100644
index 0000000..90916ed
--- /dev/null
+++ b/src/boot.asm
@@ -0,0 +1,28 @@
+.set ALIGN, 1<<0
+.set MEMINFO, 1<<1
+.set FLAGS, ALIGN | MEMINFO
+.set MAGIC, 0x1BADB002
+.set CHECKSUM, -(MAGIC + FLAGS)
+
+.section .multiboot
+.align 4
+.long MAGIC
+.long FLAGS
+.long CHECKSUM
+
+.section .bss
+.align 16
+stack_bottom:
+.skip 16384
+stack_top:
+
+.section .text
+.global _start
+.type _start, @function
+_start:
+	mov $stack_top, %esp
+	call kernel_main
+	cli
+1:	hlt
+	jmp 1b
+.size _start, . - _start
diff --git a/src/kernel.cpp b/src/kernel.cpp
new file mode 100644
index 0000000..a6a7bb7
--- /dev/null
+++ b/src/kernel.cpp
@@ -0,0 +1,13 @@
+#include "kernel/vga.h"
+
+void main() {
+	VGA vga = VGA();
+	vga.terminal_init();
+	vga.terminal_writestring("Hello from kernel main\nTest\n");
+	for(int i = 0; i < 80; i++)
+		vga.terminal_writestring("YEET\n");
+}
+
+extern "C" void kernel_main(void) {
+	main();
+}
diff --git a/src/kernel/vga.cpp b/src/kernel/vga.cpp
new file mode 100644
index 0000000..06a478a
--- /dev/null
+++ b/src/kernel/vga.cpp
@@ -0,0 +1,73 @@
+#include "vga.h"
+
+inline uint8_t VGA::vga_entry_color(enum vga_color fg, enum vga_color bg) {
+	return fg | bg << 4;
+}
+
+inline uint16_t VGA::vga_entry(unsigned char uc, uint8_t color) {
+	return (uint16_t) uc | (uint16_t) color << 8;
+}
+
+size_t VGA::strlen(const char* str) {
+	size_t len = 0;
+	while (str[len])
+		len++;
+	return len;
+}
+
+void VGA::linebreak() {
+	if(terminal_row == VGA_HEIGHT) {
+		for(size_t row = 1; row < VGA_HEIGHT; row++) {
+			terminal_buffer[row - 1] = terminal_buffer[row];
+		}
+	}else {
+		terminal_row++;
+	}
+
+	terminal_column = 0;
+}
+
+void VGA::terminal_setcolor(uint8_t color) {
+	terminal_color = color;
+}
+
+void VGA::terminal_putentryat(char c, uint8_t color, size_t x, size_t y) {
+	const size_t index = y * VGA_WIDTH + x;
+	terminal_buffer[index] = vga_entry(c, color);
+}
+
+void VGA::terminal_putchar(char c) {
+	terminal_putentryat(c, terminal_color, terminal_column, terminal_row);
+	if(++terminal_column == VGA_WIDTH) {
+		terminal_column = 0;
+		if(++terminal_row == VGA_HEIGHT)
+			terminal_row = 0;
+	}
+}
+
+void VGA::terminal_write(const char* data, size_t size) {
+	for(size_t i = 0; i < size; i++) {
+		if(data[i] == '\n') {
+			linebreak();
+			continue;
+		}
+		terminal_putchar(data[i]);
+	}
+}
+
+void VGA::terminal_writestring(const char* data) {
+	terminal_write(data, strlen(data));
+}
+
+void VGA::terminal_init(void) {
+	terminal_row = 0;
+	terminal_column = 0;
+	terminal_color = vga_entry_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK);
+	terminal_buffer = (uint16_t*) 0xB8000;
+	for (size_t y = 0; y < VGA_HEIGHT; y++) {
+		for(size_t x = 0; x < VGA_WIDTH; x++) {
+			const size_t index = y * VGA_WIDTH + x;
+			terminal_buffer[index] = vga_entry(' ', terminal_color);
+		}
+	}
+}
diff --git a/src/kernel/vga.h b/src/kernel/vga.h
new file mode 100644
index 0000000..8727863
--- /dev/null
+++ b/src/kernel/vga.h
@@ -0,0 +1,46 @@
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+class VGA {
+protected:
+	static const size_t VGA_WIDTH = 80;
+	static const size_t VGA_HEIGHT = 80;
+	
+	size_t terminal_row;
+	size_t terminal_column;
+	uint8_t terminal_color;
+	uint16_t* terminal_buffer;
+
+	void terminal_putentryat(char c, uint8_t color, size_t x, size_t y);
+	void terminal_putchar(char c);
+	void linebreak();
+
+public:	
+	enum vga_color {
+		VGA_COLOR_BLACK = 0,
+		VGA_COLOR_BLUE = 1,
+		VGA_COLOR_GREEN = 2,
+		VGA_COLOR_CYAN = 3,
+		VGA_COLOR_RED = 4,
+		VGA_COLOR_MAGENTA = 5,
+		VGA_COLOR_BROWN = 6,
+		VGA_COLOR_LIGHT_GREY = 7,
+		VGA_COLOR_DARK_GREY = 8,
+		VGA_COLOR_LIGHT_BLUE = 9,
+		VGA_COLOR_LIGHT_GREEN = 10,
+		VGA_COLOR_LIGHT_CYAN = 11,
+		VGA_COLOR_LIGHT_RED = 12,
+		VGA_COLOR_LIGHT_MAGENTA = 13,
+		VGA_COLOR_LIGHT_BROWN = 14,
+		VGA_COLOR_WHITE = 15,
+	};
+
+	static inline uint8_t vga_entry_color(enum vga_color fg, enum vga_color bg);
+	static inline uint16_t vga_entry(unsigned char uc, uint8_t color);
+	size_t strlen(const char* str);
+	void terminal_setcolor(uint8_t color);
+	void terminal_write(const char* data, size_t size);
+	void terminal_writestring(const char* data);
+	void terminal_init(void);
+};