From 07c91e3584ffcfccfefb8c16587df8f41dd208a9 Mon Sep 17 00:00:00 2001
From: Jackson Taylor <jtaylormuffins@gmail.com>
Date: Thu, 5 Nov 2020 20:47:53 -0500
Subject: Inital work

---
 boot.s    |  29 ++++++++++++++++++
 grub.cfg  |   3 ++
 kernel.c  | 100 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 linker.ld |  28 ++++++++++++++++++
 makefile  |  13 ++++++++
 5 files changed, 173 insertions(+)
 create mode 100644 boot.s
 create mode 100644 grub.cfg
 create mode 100644 kernel.c
 create mode 100644 linker.ld
 create mode 100644 makefile

diff --git a/boot.s b/boot.s
new file mode 100644
index 0000000..2278755
--- /dev/null
+++ b/boot.s
@@ -0,0 +1,29 @@
+.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/grub.cfg b/grub.cfg
new file mode 100644
index 0000000..3d5ba5b
--- /dev/null
+++ b/grub.cfg
@@ -0,0 +1,3 @@
+menuentry "myos" {
+    multiboot /boot/myos.bin
+}
diff --git a/kernel.c b/kernel.c
new file mode 100644
index 0000000..3e75c7a
--- /dev/null
+++ b/kernel.c
@@ -0,0 +1,100 @@
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#if defined(__linux__)
+#error "Not your cross compiler stupid!"
+#endif
+
+
+#if !defined(__i386__)
+#error "not ix86-elf"
+#endif
+
+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) {
+    return fg | bg << 4;
+}
+
+static inline uint16_t vga_entry(unsigned char uc, uint8_t color) {
+    return (uint16_t) uc | (uint16_t) color << 8;
+}
+
+size_t strlen(const char* str) {
+    size_t len = 0;
+    while(str[len])
+        len++;
+    return len;
+}
+
+static const size_t VGA_WIDTH = 80;
+static const size_t VGA_HEIGHT = 25;
+
+size_t terminal_row;
+size_t terminal_column;
+uint8_t terminal_color;
+uint16_t* terminal_buffer;
+
+void terminal_initialize(void) {
+    terminal_row = 0;
+    terminal_column = 0;
+    terminal_color = vga_entry_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLUE);
+    terminal_buffer = (uint16_t*) 0xB80000;
+    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);
+        }
+    }
+}
+
+void terminal_setcolor(uint8_t color) {
+    terminal_color = color;
+}
+
+void 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 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 terminal_write(const char* data, size_t size) {
+    for (size_t i = 0; i < size; i++)
+        terminal_putchar(data[i]);
+}
+
+void terminal_writestring(const char* data) {
+    terminal_write(data, strlen(data));
+}
+
+void kernel_main(void) {
+    terminal_initialize();
+    terminal_writestring("Hello, kernel World!\n");
+}
+
diff --git a/linker.ld b/linker.ld
new file mode 100644
index 0000000..a2529b3
--- /dev/null
+++ b/linker.ld
@@ -0,0 +1,28 @@
+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/makefile b/makefile
new file mode 100644
index 0000000..f6d082c
--- /dev/null
+++ b/makefile
@@ -0,0 +1,13 @@
+ASM="/home/jackson/opt/cross/bin/i686-elf-as"
+CC="/home/jackson/opt/cross/bin/i686-elf-gcc"
+
+all: boot.s kernel.c linker.ld
+	$(ASM) boot.s -o boot.o
+	$(CC) -c kernel.c -o kernel.o -std=gnu99 -ffreestanding -O2 -Wall -Wextra
+	$(CC) -T linker.ld -o myos.bin -ffreestanding -O2 -nostdlib boot.o kernel.o -lgcc
+iso: all
+	cp myos.bin isodir/boot/
+	grub-mkrescue -o myos.iso isodir/
+clean:
+	rm *.o *.bin *.iso
+
-- 
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