Initial commit

Makefile

@@ -0,0 +1,20 @@
+.PHONY: all clean install
+
+all: kernel
+
+install: kernel
+	mount bootdisk.img /mnt -o loop
+	cp kernel /mnt/kernel
+	umount /mnt
+
+kernel: start.o link.ld main.o vga.o
+	ld -m elf_i386 -T link.ld -o kernel start.o main.o vga.o
+
+%.o: %.c
+	gcc -Wall -m32 -O -fstrength-reduce -fomit-frame-pointer -finline-functions -nostdinc -fno-builtin -I./include -c -o $@ $<
+
+start.o: start.asm
+	nasm -f elf -o start.o start.asm
+
+clean:
+	rm -f *.o kernel

README.md

@@ -0,0 +1,2 @@
+# klange's OS Development Repo #
+I'm writing an OS because I'm bored and want a massive project to suck up the little pieces of my time for the next few years.

include/system.h

@@ -0,0 +1,19 @@
+#ifndef __SYSTEM_H
+#define __SYSTEM_H
+
+/* Kernel Main */
+extern unsigned char *memcpy(unsigned char *dest, const unsigned char *src, int count);
+extern unsigned char *memset(unsigned char *dest, unsigned char val, int count);
+extern unsigned short *memsetw(unsigned short *dest, unsigned short val, int count);
+extern int strlen(const char *str);
+extern unsigned char inportb (unsigned short _port);
+extern void outportb (unsigned short _port, unsigned char _data);
+
+/* VGA driver */
+extern void cls();
+extern void putch(unsigned char c);
+extern void puts(unsigned char *str);
+extern void settextcolor(unsigned char forecolor, unsigned char backcolor);
+extern void init_video();
+
+#endif

link.ld

@@ -0,0 +1,25 @@
+OUTPUT_FORMAT("binary")
+ENTRY(start)
+phys = 0x00100000;
+SECTIONS
+{
+	.text phys : AT(phys) {
+		code = .;
+		*(.text)
+		*(.rodata)
+		. = ALIGN(4096);
+	}
+	.data : AT(phys + (data - code))
+	{
+		data = .;
+		*(.data)
+		. = ALIGN(4096);
+	}
+	.bss : AT(phys + (bss - code))
+	{
+		bss = .;
+		*(.bss)
+		. = ALIGN(4096);
+	}
+	end = .;
+}

main.c

@@ -0,0 +1,108 @@
+#include <system.h>
+
+/*
+ * memcpy
+ * Copy from source to destination. Assumes that
+ * source and destination are not overlapping.
+ */
+unsigned char *
+memcpy(
+		unsigned char *dest,
+		const unsigned char *src,
+		int count
+	  ) {
+	int i;
+	i = 0;
+	for ( ; i < count; ++i ) {
+		dest[i] = src[i];
+		
+	}
+	return dest;
+}
+
+/*
+ * memset
+ * Set `count` bytes to `val`.
+ */
+unsigned char *
+memset(
+		unsigned char *dest,
+		unsigned char val,
+		int count
+	  ) {
+	int i;
+	i = 0;
+	for ( ; i < count; ++i ) {
+		dest[i] = val;
+	}
+	return dest;
+}
+
+/*
+ * memsetw
+ * Set `count` shorts to `val`.
+ */
+unsigned short *
+memsetw(
+		unsigned short *dest,
+		unsigned short val,
+		int count
+	  ) {
+	int i;
+	i = 0;
+	for ( ; i < count; ++i ) {
+		dest[i] = val;
+	}
+	return dest;
+}
+
+/*
+ * strlen
+ * Returns the length of a given `str`.
+ */
+int
+strlen(
+		const char *str
+	  ) {
+	int i = 0;
+	while (str[i] != (char)0) {
+		++i;
+	}
+	return i;
+}
+
+/*
+ * inportb
+ * Read from an I/O port.
+ */
+unsigned char
+inportb(
+		unsigned short _port
+	   ) {
+	unsigned char rv;
+	__asm__ __volatile__ ("inb %1, %0" : "=a" (rv) : "dN" (_port));
+	return rv;
+}
+
+/*
+ * outportb
+ * Write to an I/O port.
+ */
+void
+outportb(
+		unsigned short _port,
+		unsigned char _data
+		) {
+	__asm__ __volatile__ ("outb %1, %0" : : "dN" (_port), "a" (_data));
+}
+
+/*
+ * Kernel Entry Point
+ */
+int
+main() {
+	init_video();
+	puts("Hello world!\n");
+	for (;;);
+	return 0;
+}

start.asm

@@ -0,0 +1,44 @@
+[BITS 32]
+global start
+start:
+	mov esp, _sys_stack
+	jmp stublet
+
+ALIGN 4
+mboot:
+	MULTIBOOT_PAGE_ALIGN	equ 1<<0
+	MULTIBOOT_MEMORY_INFO	equ 1<<1
+	MULTIBOOT_AOUT_KLUDGE	equ 1<<16
+	MULTIBOOT_HEADER_MAGIC	equ 0x1BADB002
+	MULTIBOOT_HEADER_FLAGS	equ MULTIBOOT_PAGE_ALIGN | MULTIBOOT_MEMORY_INFO | MULTIBOOT_AOUT_KLUDGE
+	MULTIBOOT_CHECKSUM		equ -(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS)
+	EXTERN code, bss, end
+	; GRUB Multiboot header, boot signature
+	dd MULTIBOOT_HEADER_MAGIC
+	dd MULTIBOOT_HEADER_FLAGS
+	dd MULTIBOOT_CHECKSUM
+	; AOUT kludge (must be physical addresses)
+	; Linker script fills these in
+	dd mboot
+	dd code
+	dd bss
+	dd end
+	dd start
+
+; Main entrypoint
+stublet:
+	extern	main
+	call	main
+	jmp		$
+
+; GDT
+
+; Interrupt Service Routines
+
+; BSS Section
+SECTION .bss
+	resb 8192 ; 8KB of memory reserved
+_sys_stack:
+; This line intentionally left blank
+
+

vga.c

@@ -0,0 +1,140 @@
+#include <system.h>
+
+/*
+ * Text pointer, background, foreground
+ */
+unsigned short * textmemptr;
+int attrib = 0x0F;
+int csr_x = 0, csr_y = 0;
+
+/*
+ * scroll
+ * Scroll the screen
+ */
+void
+scroll() {
+	unsigned blank, temp;
+	blank = 0x20 | (attrib << 8);
+	if (csr_y >= 25) {
+		/*
+		 * Move the current text chunk that makes up the screen
+		 * back in the buffer by one line.
+		 */
+		temp = csr_y - 25 + 1;
+		memcpy(textmemptr, textmemptr + temp * 80, (25 - temp) * 80 * 2);
+		/*
+		 * Set the chunk of memory that occupies
+		 * the last line of text to the blank character
+		 */
+		memsetw(textmemptr + (25 - temp) * 80, blank, 80);
+		csr_y = 25 - 1;
+	}
+}
+
+/*
+ * move_csr
+ * Update the hardware cursor
+ */
+void
+move_csr() {
+	unsigned temp;
+	temp = csr_y * 80 + csr_x;
+	
+	/*
+	 * Write stuff out.
+	 */
+	outportb(0x3D4, 14);
+	outportb(0x3D5, temp >> 8);
+	outportb(0x3D4, 15);
+	outportb(0x3D5, temp);
+}
+
+/*
+ * cls
+ * Clear the screen
+ */
+void
+cls() {
+	unsigned blank;
+	int i;
+	blank = 0x20 | (attrib << 8);
+	for (i = 0; i < 25; ++i) {
+		memsetw(textmemptr + i * 80, blank, 80);
+	}
+	csr_x = 0;
+	csr_y = 0;
+	move_csr();
+}
+
+/*
+ * putch
+ * Puts a character to the screen
+ */
+void
+putch(
+		unsigned char c
+	 ) {
+	unsigned short *where;
+	unsigned att = attrib << 8;
+	if (c == 0x08) {
+		/* Backspace */
+		if (csr_x != 0) csr_x--;
+	} else if (c == 0x09) {
+		/* Tab */
+		csr_x = (csr_x + 8) & ~(8 - 1);
+	} else if (c == '\r') {
+		/* Carriage return */
+		csr_x = 0;
+	} else if (c == '\n') {
+		/* New line */
+		csr_x = 0;
+		csr_y++;
+	} else if (c >= ' ') {
+		where = textmemptr + (csr_y * 80 + csr_x);
+		*where = c | att;
+		csr_x++;
+	}
+
+	if (csr_x >= 80) {
+		csr_x = 0;
+		csr_y++;
+	}
+	scroll();
+	move_csr();
+}
+
+/*
+ * puts
+ * Put string to screen
+ */
+void
+puts(
+		unsigned char * text
+	){ 
+	int i;
+	int len = strlen(text);
+	for (i = 0; i < len; ++i) {
+		putch(text[i]);
+	}
+}
+
+/*
+ * settextcolor
+ * Sets the foreground and background color
+ */
+void
+settextcolor(
+		unsigned char forecolor,
+		unsigned char backcolor
+		) {
+	attrib = (backcolor << 4) | (forecolor & 0x0F);
+}
+
+/*
+ * init_video
+ * Initialize the VGA driver.
+ */
+void init_video() {
+	textmemptr = (unsigned short *)0xB8000;
+	cls();
+}