From 695bd777515288ab6bf498e60605660b899163e7 Mon Sep 17 00:00:00 2001
From: Garritt McCune <glmccune@gmail.com>
Date: Sat, 9 May 2020 21:55:51 -0500
Subject: [PATCH] Fixed a bug that caused the kernel image to lose it multiboot
 signature. Added code to test printing a string to the screen.

---
 build_numbers.c        |  2 +-
 includes/kernel.h      |  8 ++++++++
 includes/screen.h      |  5 +++++
 kernel/kmain.c         | 38 ++++++++++++++++++++++++++++++++------
 kernel/loader.s        |  8 +++-----
 support_files/boch.txt |  2 +-
 6 files changed, 50 insertions(+), 13 deletions(-)
 create mode 100644 includes/kernel.h
 create mode 100644 includes/screen.h

diff --git a/build_numbers.c b/build_numbers.c
index 21a2a3b..1749ab0 100644
--- a/build_numbers.c
+++ b/build_numbers.c
@@ -1,3 +1,3 @@
 #ifndef KERNEL_VERSION_NUMBER
-#define KERNEL_VERSION_NUMBER "1.4.10-8"
+#define KERNEL_VERSION_NUMBER "0.0.1-47"
 #endif
diff --git a/includes/kernel.h b/includes/kernel.h
new file mode 100644
index 0000000..9690b40
--- /dev/null
+++ b/includes/kernel.h
@@ -0,0 +1,8 @@
+#ifndef KERNEL_H
+#define KERNEL_H
+
+void write_screen(unsigned int, char, unsigned char, unsigned char);
+void move(unsigned short);
+void draw_s(char*, unsigned char, unsigned char);
+int strlen(char*);
+#endif
diff --git a/includes/screen.h b/includes/screen.h
new file mode 100644
index 0000000..85d5009
--- /dev/null
+++ b/includes/screen.h
@@ -0,0 +1,5 @@
+#ifndef SCREEN_H
+#define SCREEN_H
+void draw_string(char*, unsigned char, unsigned char);
+int strlen(char*);
+#endif
diff --git a/kernel/kmain.c b/kernel/kmain.c
index 9161adb..addd9db 100644
--- a/kernel/kmain.c
+++ b/kernel/kmain.c
@@ -1,13 +1,20 @@
 #include "../includes/io.h"
+#include "../includes/kernel.h"
 
-void write_screen(unsigned int, char, unsigned char, unsigned char);
-void move(unsigned short);
+//char* msg = "Hello, World!";
 
-extern void kmain()
+void kmain()
 {
-	write_screen(0, 'A', 2, 8);
-	move(80);
-	//asm("hlt");
+	draw_s("Hello, World!", 2, 9);/*
+	write_screen(0, "k", 2, 9);
+	write_screen(2, 'e', 2, 9);
+	write_screen(4, 'r', 2, 9);
+	write_screen(6, 'n', 2, 9);
+	write_screen(8, 'e', 2, 9);
+	write_screen(10, 'l', 2, 9);
+	write_screen(12, ' ', 2, 9);
+	write_screen(14, '3', 2, 9);
+	//asm("hlt");*/
 }
 
 void write_screen(unsigned int i, char c, unsigned char fg, unsigned char bg)
@@ -24,3 +31,22 @@ void move(unsigned short pos)
 	outb(0x3D4, 15);
 	outb(0x3D5, pos & 0x00FF);
 }
+
+void draw_s(char* string, unsigned char fg, unsigned char bg)
+{
+	char *video_buffer = 0x000B8000;
+	for(int i = 0; i < strlen(string); i++)
+	{
+		video_buffer[i] = string[i];
+		video_buffer[i+1] = ((fg & 0x0f) << 4) | (bg & 0x0F);
+	}
+}
+
+int strlen(char* string)
+{
+	int len = 0;
+	
+	for(int i = 0; string[i] != '\0'; i++) len++;
+	
+	return len;
+}
diff --git a/kernel/loader.s b/kernel/loader.s
index aa9869a..b2c0a76 100644
--- a/kernel/loader.s
+++ b/kernel/loader.s
@@ -1,25 +1,23 @@
 global loader
 
+align 4
 MAGIC_NUMBER equ 0x1BADB002
 FLAGS equ 0x0
 CHECKSUM equ -MAGIC_NUMBER
-KERNEL_STACK_SIZE equ 4096							; size of stack in bytes
+KERNEL_STACK_SIZE equ 4096						; size of stack in bytes
 
-section .text:
-	align 4
 	dd MAGIC_NUMBER
 	dd FLAGS
 	dd CHECKSUM
 
 loader:
+	mov esp, kernel_stack; + KERNEL_STACK_SIZE 	; ont ESP to the start of the stack (end of memory area)
 	extern kmain
 	call kmain
 	;mov eax, 0xCAFEBABE
-	;mov esp, kernel_stack + KERNEL_STACK_SIZE	; piont ESP to the start of the stack (end of memory area)
 .loop:
 	jmp .loop
 
 section .bss
-	alignb 4
 	resb KERNEL_STACK_SIZE						; reserve stack for kernel
 	kernel_stack:
diff --git a/support_files/boch.txt b/support_files/boch.txt
index 25888cf..e36be6f 100644
--- a/support_files/boch.txt
+++ b/support_files/boch.txt
@@ -1,5 +1,5 @@
 megs: 32
-display_library: x
+display_library: x, options = "gui_debug"
 romimage: file=/usr/share/bochs/BIOS-bochs-latest
 vgaromimage: file=/usr/share/bochs/VGABIOS-lgpl-latest
 ata0-master: type=cdrom, path=kernel.iso, status=inserted