Strip down bootloader and tweak to load multiple blocks

3 files changed, 170 insertions, 56 deletions

diff --git a/bootloader.asm b/bootloader.asm
index 2993726..cf8ccb4 100644
--- a/bootloader.asm
+++ b/bootloader.asm
@@ -10,21 +10,10 @@ start:
   mov si, HELLO
   call write_str
   call disk_read
-  mov si, VERIFY
+  call verify_read
+  mov si, READ_NERR
   call write_str
-  mov ax, 0x61
-  call cursor_next_line
-  call write_char_default_attr
-  mov ax, 0x62
-  call cursor_next_line
-  call write_char_default_attr
-  mov ax, 0x63
-  call cursor_next_line
-  call write_char_default_attr
-  call write_char_default_attr
-  call write_char_default_attr
-  call cursor_back_one
-  call cursor_backspace
+  jmp 0x7e00
   jmp hang
 
 read_err:
@@ -33,6 +22,21 @@ read_err:
 hang:
   jmp hang
 
+verify_read:
+  mov al, 0x66
+  cmp al, [0x7e00]
+  jne read_err
+  mov al, 0x55
+  cmp al, [0x7e01]
+  jne read_err
+  mov al, 0x66
+  cmp al, [0x7e02]
+  jne read_err
+  mov al, 0x89
+  cmp al, [0x7e03]
+  jne read_err
+  ret
+
 write_str:
   push ax
   push si
@@ -86,14 +90,12 @@ disk_read:
   mov ah, 0x42
   int 0x13
   jc read_err
-  mov si, READ_SUCC
-  call write_str
   ret
 
 READ_ERR:
   db 'Read failed: ', 0
-READ_SUCC:
-  db 'Read didnt fail: ', 0
+READ_NERR:
+  db 'No err reading, continuing: ', 0
 HELLO:
   db 'Bootloader init: ', 0
 CURSOR_LOC:
@@ -103,45 +105,12 @@ CURSOR_LOC:
 LBA_DISK_READ_PACKET:
   db 0x10
   db 0
-  dw 1      ; number of blocks to read, reset to # actually read when done
+  dw 32     ; number of blocks to read, reset to # actually read when done
   dw 0x7e00 ; read destination address
-  dw 0
+  dw 0x0000
   dd 1      ; lba to read from
   dd 0      ; for extended lba adresses (not really used here)
 
   times 510-($-$$) db 0
   db 0x55
   db 0xAA
-
-cursor_next_line:
-  mov di, [CURSOR_LOC]
-  add di, 160
-  mov [CURSOR_LOC], di
-  ret
-
-cursor_prev_line:
-  mov di, [CURSOR_LOC]
-  sub di, 160
-  mov [CURSOR_LOC], di
-  ret
-
-cursor_backspace:
-  push ax
-  call cursor_back_one
-  mov ax, 0x00
-  call write_char_default_attr
-  call cursor_back_one
-  pop ax
-  ret
-
-cursor_back_one:
-  mov di, [CURSOR_LOC]
-  dec di
-  dec di
-  mov [CURSOR_LOC], di
-  ret
-
-VERIFY:
-  db '[x] read next block: ', 0
-
-  times 1024-($-$$) db 0
diff --git a/excessive.asm b/excessive.asm
new file mode 100644
index 0000000..2993726
--- /dev/null
+++ b/excessive.asm
@@ -0,0 +1,147 @@
+[BITS 16]
+[ORG 7c00h]
+
+init:
+  mov cx, 0xB800
+  mov gs, cx
+
+start:
+  call clr_vga
+  mov si, HELLO
+  call write_str
+  call disk_read
+  mov si, VERIFY
+  call write_str
+  mov ax, 0x61
+  call cursor_next_line
+  call write_char_default_attr
+  mov ax, 0x62
+  call cursor_next_line
+  call write_char_default_attr
+  mov ax, 0x63
+  call cursor_next_line
+  call write_char_default_attr
+  call write_char_default_attr
+  call write_char_default_attr
+  call cursor_back_one
+  call cursor_backspace
+  jmp hang
+
+read_err:
+  mov si, READ_ERR
+  call write_str
+hang:
+  jmp hang
+
+write_str:
+  push ax
+  push si
+  xor ax, ax
+write_str_each_char:
+  mov al, byte [si]
+  cmp al, 0
+  je write_str_done
+  inc si
+  call write_char_default_attr
+  jmp write_str_each_char
+write_str_done:
+  pop si
+  pop ax
+  ret
+
+write_char_default_attr:
+  push bx
+  mov bl, 0x07
+  jmp write_char_inner
+write_char:
+  push bx
+write_char_inner:
+  push di
+  mov di, [CURSOR_LOC]
+  mov byte [gs:di], al
+  inc di
+  mov byte [gs:di], bl
+  inc di
+  mov [CURSOR_LOC], di
+  pop di
+  pop bx
+  ret
+
+clr_vga:
+  mov di, 4000
+clr_vga_loop:
+  dec di
+  mov byte [gs:di], 0x00
+  cmp di, 0
+  jne clr_vga_loop
+  mov word [CURSOR_LOC], 0
+  ret
+
+disk_read:
+  ; ax = disk number to read from
+  ; reference: http://www.delorie.com/djgpp/doc/rbinter/id/14/7.html
+  mov dx, 0x80
+  or ax, dx
+  mov si, LBA_DISK_READ_PACKET
+  mov ah, 0x42
+  int 0x13
+  jc read_err
+  mov si, READ_SUCC
+  call write_str
+  ret
+
+READ_ERR:
+  db 'Read failed: ', 0
+READ_SUCC:
+  db 'Read didnt fail: ', 0
+HELLO:
+  db 'Bootloader init: ', 0
+CURSOR_LOC:
+  dw 0
+
+ ; reference: http://www.delorie.com/djgpp/doc/rbinter/it/72/2.html
+LBA_DISK_READ_PACKET:
+  db 0x10
+  db 0
+  dw 1      ; number of blocks to read, reset to # actually read when done
+  dw 0x7e00 ; read destination address
+  dw 0
+  dd 1      ; lba to read from
+  dd 0      ; for extended lba adresses (not really used here)
+
+  times 510-($-$$) db 0
+  db 0x55
+  db 0xAA
+
+cursor_next_line:
+  mov di, [CURSOR_LOC]
+  add di, 160
+  mov [CURSOR_LOC], di
+  ret
+
+cursor_prev_line:
+  mov di, [CURSOR_LOC]
+  sub di, 160
+  mov [CURSOR_LOC], di
+  ret
+
+cursor_backspace:
+  push ax
+  call cursor_back_one
+  mov ax, 0x00
+  call write_char_default_attr
+  call cursor_back_one
+  pop ax
+  ret
+
+cursor_back_one:
+  mov di, [CURSOR_LOC]
+  dec di
+  dec di
+  mov [CURSOR_LOC], di
+  ret
+
+VERIFY:
+  db '[x] read next block: ', 0
+
+  times 1024-($-$$) db 0
diff --git a/linker.ld b/linker.ld
index 1b34e93..7486136 100644
--- a/linker.ld
+++ b/linker.ld
@@ -8,14 +8,13 @@ SECTIONS
 {
   /* Begin putting sections at 1 MiB, a conventional place for kernels to be
      loaded at by the bootloader. */
-  . = 1M;
+  . = 10K;
 
   /* First put the multiboot header, as it is required to be put very early
      early in the image or the bootloader won't recognize the file format.
      Next we'll put the .text section. */
   .text BLOCK(4K) : ALIGN(4K)
   {
-    *(.multiboot)
     *(.text)
   }
 
@@ -34,7 +33,6 @@ SECTIONS
   /* Read-write data (uninitialized) and stack */
   .bss BLOCK(4K) : ALIGN(4K)
   {
-    *(COMMON)
     *(.bss)
     *(.bootstrap_stack)
   }