Executing code from second section of floppy image

source/mytest2.s

@@ -0,0 +1,226 @@
+#generate 16-bit code
+.code16
+
+#hint the assembler that here is the executable code located
+.text
+.globl _start;
+#boot code entry
+_start:
+  jmp _boot
+start: .asciz "Start.\n\r"
+error: .asciz "Error.\n\r"
+succes: .asciz "Succes.\n\r"
+ffs: .asciz "F.\n\r"
+end: .asciz "End.\n\r"
+derpy2str: .asciz "This is from derpy2.\n\r"
+cookies: .word derpy2
+
+.macro mWriteString str              #macro which calls a function to print a string
+  leaw  \str, %si
+  call .writeStringIn
+.endm
+
+# function to print the string
+.writeStringIn:
+    lodsb
+    orb  %al, %al
+    jz   .writeStringOut
+    movb $0x0e, %ah
+    int  $0x10
+    jmp  .writeStringIn
+  .writeStringOut:
+ret
+  
+
+_boot:
+  mWriteString start
+  
+  movb $0x0e, %ah
+  movb $'X', %al
+  int $0x10
+  
+  movb $'\n', %al
+  int $0x10
+  
+  movb $'\r', %al
+  int $0x10
+  
+  lgdt gdtdesc
+  
+  #movb $42, %bl #NOT 'A'
+  #movb %bl, 0x512
+  
+  #This goes first as to now overwrite %ah and %al.
+  mov $0x00, %ax
+  #mov $0x08, %ax
+  mov %ax, %es #Section to write into
+  
+  mov $0x02, %ah # Read sectors from drive
+  mov $0x01, %al # Number of sectors to read
+  mov $0x00, %ch # Low 8 bits of cylinder
+  mov $0x02, %cl # First sector to read (bits 0-5), upper bits of cylinder (bits 6-7)
+  mov $0x00, %dh # Head number
+  mov $0x00, %dl # Drive number
+#  mov $0x00, %es
+  mov $0x7e00, %bx #Offset into section
+  #mov $0x0, %bx #Offset into section
+  int $0x13 # Low level disk services
+  
+  jnc notcarry
+  #mWriteString error
+  jmp endcarrycheck
+  
+  notcarry:
+  #mWriteString succes
+  
+  #mov $0x7000, %ax
+  #movb (%ax), %bl
+  #movb %bl, ffs
+  #movb 0x7000, %bl
+  #movb %bl, ffs
+  #mWriteString ffs
+  #fallthrough
+  
+  endcarrycheck:
+  
+  #mWriteString mystr-block2_offset
+  #mWriteString 0x513
+  #mWriteString mystr
+  
+  #ljmp $0x0, $derpy
+  #.byte 0, 0, 0, 0, 0, 0, 0, 0
+  #ljmp $0x00, $0x7e00
+  #ljmp $0x00, $derpy2
+  ljmp $0x00, $code
+  
+#  movw $derpy, %ax
+#  
+#  cmp $0x7e00, %ax
+#  je equal
+#  mWriteString error
+#  jmp after
+#  
+#  equal:
+#  mWriteString succes
+#  
+#  after:
+  /*
+  movb $0x0e, %ah
+  
+  movw $derpy, %cx
+  
+  movb 0x0e, %ah
+  movb $'I', %al
+  int $0x10
+  movb 0x0e, %ah
+  movb $'J', %al
+  int $0x10
+  */
+  
+  #movw $0x7E00, %cx
+  movw $derpy2, %cx
+  
+  movb $0x0e, %ah
+  #movb $'Y', %al
+  movb %ch, %al
+  #movb $'H', %al
+  #movb $0x7E, %al
+  int $0x10
+  
+  movb $0x0e, %ah
+  #movb $'Z', %al
+  movb %cl, %al
+  #add $0x7E, %al
+  #sub $0x50, %al
+  #movb $0x3C, %al
+  int $0x10
+  
+  movb $0x0e, %ah
+  movb $'\n', %al
+  int $0x10
+  
+  movb $0x0e, %ah
+  movb $'\r', %al
+  int $0x10
+  
+  
+  #mWriteString mystr
+  
+  #jmp derpy
+  derpyret:
+  
+  mWriteString end
+  
+  #jmp 0x7008
+  #endend:
+  #mWriteString end
+  
+  cli
+  hlt
+  
+  #
+
+derpy:
+  mWriteString ffs
+  ljmp $0x00, $derpyret
+  #jmp derpyret
+
+.p2align	2	/* force 4-byte alignment */
+gdt:
+  .word	0, 0
+  .byte	0, 0, 0, 0
+  
+  /* code segment */
+  .word	0xFFFF, 0
+  .byte	0, 0x9A, 0xCF, 0
+  
+  /* data segment */
+  .word	0xFFFF, 0
+  .byte	0, 0x92, 0xCF, 0
+  
+  /* 16 bit real mode CS */
+  .word	0xFFFF, 0
+  .byte	0, 0x9E, 0, 0
+  
+  /* 16 bit real mode DS */
+  .word	0xFFFF, 0
+  .byte	0, 0x92, 0, 0
+
+/* this is the GDT descriptor */
+gdtdesc:
+  .word	0x27			/* limit */
+  .long	gdt			/* addr */
+
+#move to 510th byte from the start and append boot signature
+. = _start + 510
+.byte 0x55
+.byte 0xaa
+#block2_offset:
+.byte 'A' #Byte 513
+#mystr: .asciz "asdf\n\r"
+
+#derpderp:
+#  mwriteString 0x7001
+#  jmp endend
+
+derpy2:
+  mWriteString derpy2str
+  ljmp $0x00, $derpyret
+
+code:
+  mWriteString derpy2str
+  movb $0x0e, %ah
+  movb $'C', %al
+  int $0x10
+  movb $0x0e, %ah
+  movb $'\n', %al
+  int $0x10
+  movb $0x0e, %ah
+  movb $'\r', %al
+  int $0x10
+  ljmp $0x00, $derpyret
+
+. = _start + 1021
+.byte 0x00
+
+.word derpy2