A src/boot/a20.s

@@ -0,0 +1,149 @@
+.section .text
+.code16
+  # check if A20 gate is enabled
+.global enable_a20
+enable_a20:
+  mov $a20_check_msg, %si
+  call print
+  call checkA20
+  je enabled
+
+  # A20 is disabled, we need to enable it
+  mov $disabled_msg, %si
+  call print
+
+  mov $a20_enable_msg, %si
+  call print
+
+  # A20 BIOS method
+a20_bios:
+  mov $a20_enable_bios_msg, %si
+  call print
+
+  movw $0x2401, %ax
+  int $0x15
+
+  mov $0x0001, %cx
+  call delay
+
+  call checkA20
+  je enabled
+
+  mov $fail_msg, %si
+  call print
+
+  # A20 keyboard controller method
+a20_keyboard:
+  mov $a20_enable_kb_msg, %si
+  call print
+
+  # TODO: implement
+
+  mov $0x0001, %cx
+  call delay
+
+  call checkA20
+  je enabled
+
+  mov $fail_msg, %si
+  call print
+
+  # fast A20 method
+a20_fasta20:
+  mov $a20_enable_fasta20_msg, %si
+  call print
+
+  inb $0x92, %al
+  orb $0x02, %al
+  andb $0xFE, %al
+  outb %al, $0x92
+
+  mov $0x1000, %cx
+  call delay
+
+  call checkA20
+  je enabled
+
+  mov $fail_msg, %si
+  call print
+
+  mov $a20_fail, %si
+  call print
+
+  jmp error
+
+
+enabled:
+  mov $enabled_msg, %si
+  call print
+
+  ret
+
+
+  # ############################################
+  # checkA20
+  #   checks if A20 line is enabled
+  #   equal flag: * clear, if A20 is enabled
+  #               * set, if A20 is disabled
+  # ############################################
+checkA20:
+  push %ds
+  push %es
+  push %si
+  push %di
+
+  mov $0x0000, %ax
+  mov %ax, %ds
+  mov $0xFFFF, %ax
+  mov %ax, %es
+
+  mov $0x0500, %si
+  mov $0x0510, %di
+
+  movw %ds:(%si), %cx
+  movw %es:(%di), %dx
+  cmp %cx, %dx
+
+  pop %di
+  pop %si
+  pop %es
+  pop %ds
+  ret
+
+
+  # delays for at least a given number of cycles.
+  # CX: number of cycles to delay
+delay:
+  nop
+  loop delay
+  ret
+
+
+.section .data
+a20_check_msg:
+  .ascii "Checking A20..."
+  .byte 0
+
+a20_enable_msg:
+  .ascii "Enabling A20 (BIOS)..."
+  .byte 13
+  .byte 10
+  .byte 0
+
+a20_fail:
+  .ascii "Could not enable A20 gate. HALT"
+  .byte 13
+  .byte 10
+  .byte 0
+
+a20_enable_bios_msg:
+  .ascii " BIOS: "
+  .byte 0
+
+a20_enable_kb_msg:
+  .ascii " keyboard controller: "
+  .byte 0
+
+a20_enable_fasta20_msg:
+  .ascii " fast A20 method: "
+  .byte 0

A src/boot/drives.s

@@ -0,0 +1,174 @@
+.section .text
+.code16
+# read hard drive parameters
+.global read_drive_params
+read_drive_params:
+  mov $drive_params_msg, %si
+  call print
+
+  movw $0x0000, %ax
+  movw %ax, %es
+  movw $0x0000, %di
+
+  movb $0x08, %ah
+  lea bootdriv_id, %si
+  movb (%si), %dl
+  int $0x13
+
+  xor %ax, %ax
+  movb %dl, %al
+  lea num_drives, %si
+  movb %al, (%si)
+
+  xor %ax, %ax
+  movb %dh, %al
+  inc %ax
+  lea num_heads, %si
+  movw %ax, (%si)
+
+  xor %ax, %ax
+  movb %cl, %al
+  shl $2, %ax
+  movb %ch, %al
+  inc %ax
+  lea num_cylinders, %si
+  movw %ax, (%si)
+
+  xor %ax, %ax
+  movb %cl, %al
+  and $0x003F, %ax
+  lea num_sectors, %si
+  movw %ax, (%si)
+
+  mov $done_msg, %si
+  call print
+
+  ret
+
+
+  # reset bootdrive
+.global reset_drive
+reset_drive:
+  mov $10, %cx
+reset_drive_loop:
+  push %cx
+  movw $reset_msg, %si
+  call print
+
+  movb $0x00, %ah
+  int $0x13
+  pop %cx
+  jnc reset_end
+  loop reset_drive_loop
+  jc error
+reset_end:
+
+  movw $done_msg, %si
+  call print
+
+  ret
+
+
+  # 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)
+
+# arguments:
+# - ax: first sector (LBA)
+# - cx: last sector (LBA)
+# - bx: address offset
+.global load_kernel
+load_kernel:
+  movw $load_msg, %si
+  call print
+
+  movw $0x0000, %ax
+  movw %ax, %ds
+
+  movw $0x0008, %ax
+  movw $0x0088, %cx
+  movw $0x0000, %bx
+
+load_sectors_loop:
+  push %ax
+  push %cx
+  push %bx
+
+  movw %bx, %di
+
+  lea num_sectors, %si
+  movw (%si), %bx
+  inc %ax
+  divb %bl
+  movb %ah, %cl
+
+  xor %ah, %ah
+  lea num_heads, %si
+  movw (%si), %bx
+  divb %bl
+  movb %ah, %dh
+  movb %al, %ch
+
+  lea bootdriv_id, %si
+  movb (%si), %dl
+
+  movw %di, %bx
+  # movw $0x0000, %bx   # buffer address
+  movw $0x1000, %ax
+  movw %ax, %es       # buffer address (segment)
+
+  movb $0x02, %ah     # function 0x02: read a sector
+  movb $0x01, %al     # sectors to read count
+  # dl (drive) keep as is
+  int $0x13
+  # jc error
+
+  pop %bx
+  pop %cx
+  pop %ax
+  inc %ax
+  add $0x200, %bx
+  cmp %ax, %cx
+  jne load_sectors_loop
+
+load_end:
+  movw $0x0000, %si   # buffer address
+  movw $0x1000, %ax
+  movw %ax, %es
+  call print
+
+  movw $done_msg, %si
+  call print
+
+
+.section .data 
+drive_params_msg:
+  .ascii "Reading drive parameters..."
+  .byte 0
+
+reset_msg: 
+  .ascii "Resetting bootdrive..."
+  .byte 0
+
+load_msg: 
+  .ascii "Loading kernel..."
+  .byte 0
+
+.section .bss
+.global bootdriv_id
+bootdriv_id:
+  .byte 0
+
+num_drives:
+  .byte 0
+
+num_sectors:
+  .word 0
+
+num_cylinders:
+  .word 0
+
+num_heads:
+  .word 0

M src/boot/entry.s → src/boot/entry.s

@@ -47,6 +47,7 @@ int $0x13
   jnc bl_loaded
 
   # auxiliary functions
+.global error
 error:
   movw $fail_msg, %si
   call print
@@ -59,6 +60,7 @@ # print
   #   prints out a string on the screen
   #   %si: points to the message to be printed
   # ############################################
+.global print
 print:
   movw $0x0000, %bx
   movb $0x0E, %ah
@@ -92,208 +94,13 @@ bl_loaded:
   mov $done_msg, %si
   call print
 
-  # read hard drive parameters
-  movw $0x0000, %ax
-  movw %ax, %es
-  movw $0x0000, %di
-
-  movb $0x08, %ah
-  lea bootdriv_id, %si
-  movb (%si), %dl
-  int $0x13
-
-  xor %ax, %ax
-  movb %dl, %al
-  lea num_drives, %si
-  movb %al, (%si)
-
-  xor %ax, %ax
-  movb %dh, %al
-  inc %ax
-  lea num_heads, %si
-  movw %ax, (%si)
-
-  xor %ax, %ax
-  movb %cl, %al
-  shl $2, %ax
-  movb %ch, %al
-  inc %ax
-  lea num_cylinders, %si
-  movw %ax, (%si)
-
-  xor %ax, %ax
-  movb %cl, %al
-  and $0x003F, %ax
-  lea num_sectors, %si
-  movw %ax, (%si)
-
-
-  # check if A20 gate is enabled
-  mov $a20_check_msg, %si
-  call print
-  call checkA20
-  je enabled
-
-  # A20 is disabled, we need to enable it
-  mov $disabled_msg, %si
-  call print
-
-  mov $a20_enable_msg, %si
-  call print
-
-  # A20 BIOS method
-a20_bios:
-  mov $a20_enable_bios_msg, %si
-  call print
-
-  movw $0x2401, %ax
-  int $0x15
-
-  mov $0x0001, %cx
-  call delay
-
-  call checkA20
-  je enabled
-
-  mov $fail_msg, %si
-  call print
-
-  # A20 keyboard controller method
-a20_keyboard:
-  mov $a20_enable_kb_msg, %si
-  call print
-
-  # TODO: implement
-
-  mov $0x0001, %cx
-  call delay
-
-  call checkA20
-  je enabled
-
-  mov $fail_msg, %si
-  call print
+  call read_drive_params
 
-  # fast A20 method
-a20_fasta20:
-  mov $a20_enable_fasta20_msg, %si
-  call print
+  call enable_a20
 
-  inb $0x92, %al
-  orb $0x02, %al
-  andb $0xFE, %al
-  outb %al, $0x92
+  call reset_drive
 
-  mov $0x1000, %cx
-  call delay
-
-  call checkA20
-  je enabled
-
-  mov $fail_msg, %si
-  call print
-
-  mov $a20_fail, %si
-  call print
-
-  jmp error_loop
-
-
-enabled:
-  mov $enabled_msg, %si
-  call print
-
-  # reset bootdrive
-  mov $10, %cx
-reset:
-  push %cx
-  movw $reset_msg, %si
-  call print
-  movw $bootdrive_msg, %si
-  call print
-
-  movb $0x00, %ah
-  int $0x13
-  pop %cx
-  jnc reset_end
-  loop reset
-  jc error
-reset_end:
-
-  movw $done_msg, %si
-  call print
-
-  # 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)
-
-# arguments:
-# - ax: first sector (LBA)
-# - cx: last sector (LBA)
-# - bx: address offset
-load_sectors:
-  movw $load_msg, %si
-  call print
-
-  movw $0x0000, %ax
-  movw %ax, %ds
-
-  movw $0x0008, %ax
-  movw $0x0088, %cx
-  movw $0x0000, %bx
-
-load_sectors_loop:
-  push %ax
-  push %cx
-  push %bx
-
-  movw %bx, %di
-
-  lea num_sectors, %si
-  movw (%si), %bx
-  inc %ax
-  divb %bl
-  movb %ah, %cl
-
-  xor %ah, %ah
-  lea num_heads, %si
-  movw (%si), %bx
-  divb %bl
-  movb %ah, %dh
-  movb %al, %ch
-
-  lea bootdriv_id, %si
-  movb (%si), %dl
-
-  movw %di, %bx
-  # movw $0x0000, %bx   # buffer address
-  movw $0x1000, %ax
-  movw %ax, %es       # buffer address (segment)
-
-  movb $0x02, %ah     # function 0x02: read a sector
-  movb $0x01, %al     # sectors to read count
-  # dl (drive) keep as is
-  int $0x13
-  # jc error
-
-  pop %bx
-  pop %cx
-  pop %ax
-  inc %ax
-  add $0x200, %bx
-  cmp %ax, %cx
-  jne load_sectors_loop
-
-load_end:
-  movw $0x0000, %si   # buffer address
-  movw $0x1000, %ax
-  movw %ax, %es
-  call print
-
-  movw $done_msg, %si
-  call print
+  call load_kernel
 
   movw $gdt_msg, %si
   call print
@@ -307,49 +114,12 @@
   lidt (IDT_DESCRIPTOR)
 
   mov %cr0, %eax
-  or $1, %eax
+  or $0x00000001, %eax
   mov %eax, %cr0
 
-  # jmp error_loop
-
+  # perform long jump to set code segment
   ljmp $0x8, $protected
 
-  # ############################################
-  # checkA20
-  #   checks if A20 line is enabled
-  #   equal flag: * clear, if A20 is enabled
-  #               * set, if A20 is disabled
-  # ############################################
-checkA20:
-  push %ds
-  push %es
-  push %si
-  push %di
-
-  mov $0x0000, %ax
-  mov %ax, %ds
-  mov $0xFFFF, %ax
-  mov %ax, %es
-
-  mov $0x0500, %si
-  mov $0x0510, %di
-
-  movw %ds:(%si), %cx
-  movw %es:(%di), %dx
-  cmp %cx, %dx
-
-  pop %di
-  pop %si
-  pop %es
-  pop %ds
-  ret
-
-  # delays for at least a given number of cycles.
-  # CX: number of cycles to delay
-delay:
-  nop
-  loop delay
-  ret
 
 .code32
 protected:
@@ -384,67 +154,32 @@ jmp loop
  
 
 .section .data 
-a20_check_msg:
-  .ascii "Checking A20..."
-  .byte 0
-
-a20_enable_msg:
-  .ascii "Enabling A20 (BIOS)..."
-  .byte 13
-  .byte 10
-  .byte 0
-
-a20_fail:
-  .ascii "Could not enable A20 gate. HALT"
-  .byte 13
-  .byte 10
-  .byte 0
-
-a20_enable_bios_msg:
-  .ascii " BIOS: "
-  .byte 0
-
-a20_enable_kb_msg:
-  .ascii " keyboard controller: "
-  .byte 0
-
-a20_enable_fasta20_msg:
-  .ascii " fast A20 method: "
-  .byte 0
-
-reset_msg: 
-  .ascii "Resett"
-  .byte 0
-
-load_msg: 
-  .ascii "Load"
-
-bootdrive_msg:
-  .ascii "ing bootdrive..."
-  .byte 0
-
 gdt_msg:
   .ascii "Setting GDT..."
   .byte 0
 
+.global done_msg
 done_msg:
   .ascii "done"
   .byte 13
   .byte 10
   .byte 0
 
+.global fail_msg
 fail_msg:
   .ascii "fail"
   .byte 13
   .byte 10
   .byte 0
 
+.global enabled_msg
 enabled_msg:
   .ascii "enabled"
   .byte 13
   .byte 10
   .byte 0
 
+.global disabled_msg
 disabled_msg:
   .ascii "disabled"
   .byte 13
@@ -457,20 +192,4 @@ .int GDT
 
 IDT_DESCRIPTOR:
   .word 0
-  .int 0
-
-.section .bss
-bootdriv_id:
-  .byte 0
-
-num_drives:
-  .byte 0
-
-num_sectors:
-  .word 0
-
-num_cylinders:
-  .word 0
-
-num_heads:
-  .word 0+  .int 0