M boot/boot.s → boot/boot.s

@@ -1,4 +1,5 @@
 .section .text
+.code16
 
   # disable interrupts
   cli
@@ -8,52 +9,95 @@ ljmp $0, $start
 start:
 
   # setup segments
-  mov $0x0000, %ax
-  mov %ax, %ss
-  mov %ax, %ds
-  mov %ax, %es
-  mov %ax, %fs
+  movw $0x0000, %ax
+  movw %ax, %ss
+  movw %ax, %ds
+  movw %ax, %es
+  movw %ax, %fs
 
   # setup stack
-  mov $0x9000, %ax
-  mov %ax, %bp
-  mov %ax, %sp
+  movw $0x9000, %sp
+  movw %sp, %bp
 
   # select display page 0
-  mov $0, %al
-  mov $0x05, %ah
+  movb $0, %al
+  movb $0x05, %ah
   int $0x10
 
   # print hello world
-  mov $message, %si
-  mov $0x0000, %bx
-  mov $0x0E, %ah
+  movw $message, %si
+  call print
 
-print_loop:
-  lodsb
-  or %al, %al
-  jz print_end
-  int $0x10
-  jmp print_loop
-print_end:
+  # reset bootdrive
+reset:
+  movb $0x00, %ah
+  int $0x13
+  jc reset
 
-  # TODO:
-  # - load kernel into memory starting at adress 0x10000
+  # load second stage into memory starting at adress 0x10000
   #   (NOTE: this code can only be jumped to after loading the global descriptor table
   #          because it uses absolute adresses larger than 16 bit)
+  #   (NOTE2: this routine only loads 0x48 sectors of the second stage into memory
+  #          and is in general pretty whacky. should be replaced with sth more serious)
+load:
+  movw $0x0000, %bx   # buffer address
+  movw $0x1000, %ax
+  movw %ax, %es       # buffer address (segment)
+  movb $0x02, %ah     # function 0x02: read a sector
+  movb $0x48, %al     # sectors to read count
+  movb $0x00, %ch     # cylinder
+  movb $0x02, %cl     # sector
+  movb $0x00, %dh     # head
+  # dl (drive) keep as is
+  int $0x13
+  jnc load
+
+  # prints out string thats loaded into memory at 0x00010000
+  # remove this test later
+  mov $0x1000, %ax
+  mov %ax, %ds
+  mov $0, %si
+  call print
+  xor %ax, %ax
+  mov %ax, %ds
+  mov %ax, %es
+
+  # TODO:
   # - load global descriptor table and far jump into protected mode
   # - activate A20 gate
-  # - jump to low kernel code
+  # - jump to second stage code
 
-  # loop forever
 
+  # loop forever
 loop:
   jmp loop
 
+
+  # ############################################
+  # print
+  #   prints out a string on the screen
+  #   %si: points to the message to be printed
+  # ############################################
+print:
+  movw $0x0000, %bx
+  movb $0x0E, %ah
+
+print_loop:
+  lodsb
+  or %al, %al
+  jz print_end
+  int $0x10
+  jmp print_loop
+print_end:
+  ret
+
+
   # some data
 message: 
-  .ascii " Hello World!"
-  .byte 0x00
+  .ascii "Hello World!"
+  .byte 13
+  .byte 10
+  .byte 0
 
 end:
   .=510

M link.txt → link.txt

@@ -17,7 +17,7 @@ {
     build/boot.o(.text)
   } >BOOT
 
-  SECOND_STAGE : AT(ADDR(BOOT) + SIZEOF(BOOT))
+  SECOND_STAGE : AT(LOADADDR(BOOT) + SIZEOF(BOOT))
   {
     build/second_stage.o(.text)
     build/second_stage.o(.data)

M second_stage/entry.s → second_stage/entry.s

@@ -1,3 +1,10 @@
+.section .text
 start:
-loop:
-  ljmp $0,$loop
+# loop:
+#   jmp loop
+
+low_kernel_welcome:
+  .ascii "Welcome to the low kernel!"
+  .byte 13
+  .byte 10
+  .byte 0