init

.gitignore

+*.img
+*.o
+*.bin
+

Makefile

+
+build:
+	cc -c boot.c -o boot.o -m32
+	ld -o boot.img -Ttext 0x0 --oformat binary boot.o -m elf_i386
+	# objcopy -O binary boot.o boot.img
+	# [[ $$(stat boot.img --printf='%s') -lt 510 ]]
+	truncate --size=510 boot.img
+	printf '\x55\xAA' >> boot.img
+
+run: build
+	qemu-system-x86_64 boot.img
+
+
+clean:
+	rm *.o
+

NOTE

+dd if=/dev/zero of=out.img bs=512K count=16
+VBoxManage convertfromraw out.img out.vdi --format vdi

asm/test.asm

+;
+; A simple boot sector program that loops forever.
+;
+[org 0x7c00]
+
+mov bx, str
+call println_bios
+
+println_bios:
+    ; Arg0: addr in register bx
+    ; while true:
+    ;     if [bx] != NULL:
+    ;         print [bx]; ++bx
+    mov ah, 0x0e
+_loop_begin:
+    mov al, [bx]
+    cmp al, 0x0
+    je _loop_exit
+    int 0x10
+    inc bx
+    jmp _loop_begin
+_loop_exit:
+    ret
+    
+println_vga:
+    ; Arg0: addr in register eax
+
+str:
+    db 'This is Recolic!', 0x0
+
+jmp $
+times 510-($-$$) db 0
+dw 0xaa55
+
+

asm/x16.asm

+[bits 16]
+[org 0x7c00]
+
+jmp _enter_prot_mode
+
+gdt_begin:
+
+gdt_entry_0:
+    dd 0x0, 0x0
+
+gdt_entry_1:
+    ; code
+    dw 0xffff ; limit[16:0]
+    dw 0x0 ; base[16:0]
+    db 0x0 ; base[24:16]
+    db 10011010b ; flags
+    db 11001111b ; flags : limit[]
+    db 0x0 ; base[32:24]
+    
+gdt_entry_2:
+    ; data
+    dw 0xffff ; limit[16:0]
+    dw 0x0 ; base[16:0]
+    db 0x0 ; base[24:16]
+    db 10010010b ; flags
+    db 11001111b ; flags : limit[]
+    db 0x0 ; base[32:24]
+
+gdt_end: 
+
+gdt_desc:
+    dw gdt_end - gdt_begin - 1
+    dd gdt_begin
+
+; Segment register values.
+CODE_SEG_OFFSET equ gdt_entry_1 - gdt_begin
+DATA_SEG_OFFSET equ gdt_entry_2 - gdt_begin
+
+_enter_prot_mode:
+    cli
+    lgdt [gdt_desc]
+    mov eax, cr0
+    or eax, 0x1
+    mov cr0, eax
+    ; We're almost in 32bit protected mode now. Flush the pipeline by far jump. 
+    jmp CODE_SEG_OFFSET:_prot_begin
+
+[bits 32]
+_prot_begin:
+    mov ax, DATA_SEG_OFFSET
+    mov ds, ax
+    mov ss, ax
+    mov es, ax
+    mov fs, ax
+    mov gs, ax
+
+    mov ebp, 0x90000 ; 600KB free space here, until 0x7c00 + 0x200 byte (MBR sector 0)
+    mov esp, ebp
+
+    
+    
+
+

boot.backup.c

+
+asm ("jmp 0x14");
+
+//void print_char(char to_print) {
+//    asm inline (
+//            "mov $0x0e, %%ah\n\t"
+//            "mov %0, %%al\n\t"
+//            "int $0x10"
+//            : 
+//            : "Ir" (to_print)
+//            : "ax"
+//            );
+//}
+//
+//void println(char *s) {
+//    while(*s != 0) {
+//        print_char(*s);
+//    }
+//}
+    
+
+
+void main() {
+_start_p:
+    asm (
+            "mov $0x0e, %ah\n\t"
+            "mov $0x55, %al\n\t"
+            "int $0x10"
+            );
+    //print_char('X');
+    //println("Hello world!");
+    //println("Recolic Booting OS HERE...");
+}
+
+asm (
+"jmp 0x-2\n\t"
+);
+
+

boot.c

+
+void main();
+void __entry() {
+    main();
+}
+
+void print_char(char to_print) {
+    asm inline (
+            "mov $0x0e, %%ah\n\t"
+            "mov %0, %%al\n\t"
+            "int $0x10"
+            : 
+            : "Ir" (to_print)
+            : "ax"
+            );
+}
+
+void println(char *s) {
+    while(*s != 0) {
+        print_char(*s);
+    }
+}
+    
+
+
+void main() {
+    asm (
+            "mov $0x0e, %ah\n\t"
+            "mov $0x55, %al\n\t"
+            "int $0x10"
+            );
+    //print_char('X');
+    //println("Hello world!");
+    //println("Recolic Booting OS HERE...");
+
+    asm (
+    "jmp 0x-2\n\t"
+    );
+}
+
+