screeck · JTEpic · May 25, 2025
diff --git a/How_to_write_a_bootloader/Part_3/bootloader/Makefile b/How_to_write_a_bootloader/Part_3/bootloader/Makefile
@@ -12,6 +12,11 @@ all:
 	dd if=./bin/kernel.bin >> ./bin/os.bin
 	dd if=/dev/zero bs=512 count=8 >> ./bin/os.bin
 
+qemu:
+	# Use 32 bit qemu when using debugger on this 32 bit OS
+	qemu-system-x86_64 -hda ./bin/os.bin
+	#qemu-system-i386 -hda ./bin/os.bin
+
 clean:
 	rm -f ./bin/boot.bin
 	rm -f ./bin/kernel.bin

diff --git a/How_to_write_a_bootloader/Part_3/bootloader/bin/boot.bin b/How_to_write_a_bootloader/Part_3/bootloader/bin/boot.bin
diff --git a/How_to_write_a_bootloader/Part_3/bootloader/bin/kernel.bin b/How_to_write_a_bootloader/Part_3/bootloader/bin/kernel.bin
diff --git a/How_to_write_a_bootloader/Part_3/bootloader/bin/os.bin b/How_to_write_a_bootloader/Part_3/bootloader/bin/os.bin
diff --git a/How_to_write_a_bootloader/Part_3/bootloader/build/completeKernel.o b/How_to_write_a_bootloader/Part_3/bootloader/build/completeKernel.o
diff --git a/How_to_write_a_bootloader/Part_3/bootloader/build/kernel.asm.o b/How_to_write_a_bootloader/Part_3/bootloader/build/kernel.asm.o
diff --git a/How_to_write_a_bootloader/Part_3/bootloader/build/kernel.o b/How_to_write_a_bootloader/Part_3/bootloader/build/kernel.o
diff --git a/How_to_write_a_bootloader/Part_3/bootloader/src/boot.asm b/How_to_write_a_bootloader/Part_3/bootloader/src/boot.asm
@@ -18,10 +18,17 @@ start:
     mov ss, ax    ; Set stack segment (SS) to 0x00
     mov sp, 0x7c00; Set stack pointer (SP) to 0x7c00, top of the bootloader segment
     sti           ; Enable interrupts, allowing them to occur again
+
+    ; set video mode, al 03h is a text mode, this also clears the screen
+    mov AH, 00h
+    mov AL, 03h
+    int 0x10
 
 
 ;Load kernel
-mov bx, KERNEL_LOAD_SEG
+mov bx, KERNEL_LOAD_SEG ; Load segment
+mov es, bx
+mov bx, 0x0000 ; Load offset (SEG*16 + OFFSET)
 mov dh, 0x00
 mov dl, 0x80
 mov cl, 0x02
@@ -89,6 +96,13 @@ PModeMain:
     or al, 2
     out 0x92, al
 
+    ; Copy kernel from 0x10000 to 0x100000, where we jump to, as protected mode can access past 1MB now
+    mov esi, 0x10000  ; Source
+    mov edi, KERNEL_START_ADDR ; Destination
+    mov ecx, 4096     ; num sectors * 512 bytes
+    cld
+    rep movsb
+
     jmp CODE_OFFSET:KERNEL_START_ADDR
 
 

diff --git a/How_to_write_a_bootloader/Part_3/bootloader/src/kernel.asm b/How_to_write_a_bootloader/Part_3/bootloader/src/kernel.asm
@@ -5,6 +5,6 @@ extern kernel_main
 
 _start:
     call kernel_main
-    jmp$
+    jmp $
 
-times 512-($ - $$) db 0
+times 510-($ - $$) db 0
diff --git a/How_to_write_a_bootloader/Part_3/bootloader/src/kernel.c b/How_to_write_a_bootloader/Part_3/bootloader/src/kernel.c
@@ -1,5 +1,9 @@
 #include "kernel.h"
 
+#define VIDEO_MEMORY 0xb8000
+
 void kernel_main(){
-
+    unsigned char *video = (unsigned char *)VIDEO_MEMORY;
+    video[0] = 'H';
+    video[2] = 'i';
 }
diff --git a/How_to_write_a_bootloader/Part_3/bootloader/src/kernel.h b/How_to_write_a_bootloader/Part_3/bootloader/src/kernel.h
@@ -1,5 +1,5 @@
-#ifndef KENREL_H
-#define KENREL_H
+#ifndef KERNEL_H
+#define KERNEL_H
 
 void kernel_main();
 

diff --git a/How_to_write_a_bootloader/Part_3/bootloader/src/linkerScript.ld b/How_to_write_a_bootloader/Part_3/bootloader/src/linkerScript.ld
@@ -3,22 +3,22 @@ OUTPUT_FORMAT(binary)
 SECTIONS
 {
     . = 0x0100000;
-    .text : ALIGN(4096)
+    .text : ALIGN(16)
     {
         *(.text)
     }
 
-    .rodata : ALIGN(4096)
+    .rodata : ALIGN(16)
     {
         *(.rodata)
     }
 
-    .data : ALIGN(4096)
+    .data : ALIGN(16)
     {
         *(.data)
     }
 
-    .bss : ALIGN(4096)
+    .bss : ALIGN(16)
     {
         *(COMMON)
         *(.bss)