M makefile → makefile

@@ -65,7 +65,7 @@
 $(GLOBAL_BUILD)/fat.img: $(MODULES)
 # > $(LD) 		$(OBJECTS) -r -T link.txt -Map=$(LOG_DIR)/elf_mapfile.txt --oformat elf32-i386 -o $@
 > dd if=/dev/zero of=$@ count=128
-> mkfs.fat $@
+> mkfs.fat -n "cedos" -S 512  $@
 > mkdir -p ./mnt
 > sudo mount $@ ./mnt
 > sudo cp $(LOCAL_BUILD)/kernel.bin ./mnt
@@ -76,6 +76,7 @@ $(GLOBAL_BUILD)/cedos.img: $(GLOBAL_BUILD)/fat.img | $(MODULES)
 > dd if=/dev/zero of=$@ count=144
 > parted $@ mklabel msdos
 > parted $@ mkpart primary FAT32 8s 128s -s
+> parted $@ set 1 boot on
 > dd if=$< of=$@ seek=8 conv=notrunc
 > dd bs=1 if=$(LOCAL_BUILD)/boot.bin of=$@ count=446 conv=notrunc
 > dd if=$(LOCAL_BUILD)/boot.bin of=$@ skip=1 seek=1 count=7 conv=notrunc

M src/boot/drives.s → src/boot/drives.s

@@ -130,11 +130,6 @@ 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:
@@ -142,9 +137,9 @@ push %ax
   push %cx
   push %bx
 
-  movw $load_debug_msg, %si
-  call print
-  call print_hex_int16
+  # movw $load_debug_msg, %si
+  # call print
+  # call print_hex_int16
 
   movw %bx, %di
 
@@ -167,22 +162,22 @@ movb (%si), %dl
 
   movw %di, %bx
   
-  movw $load_debug_arrow, %si
-  call print
+  # movw $load_debug_arrow, %si
+  # call print
 
   movw $0x1000, %ax
-  call print_hex_int16
   movw %ax, %es       # buffer address (segment)
+  # call print_hex_int16
 
-  movw $load_debug_colon, %si
-  call print
-  movw %bx, %ax
-  call print_hex_int16
+  # movw $load_debug_colon, %si
+  # call print
+  # movw %bx, %ax
+  # call print_hex_int16
 
-  movw $load_debug_colon, %si
-  call print
-  movw %cx, %ax
-  call print_hex_int16
+  # movw $load_debug_colon, %si
+  # call print
+  # movw %cx, %ax
+  # call print_hex_int16
 
   movb $0x02, %ah     # function 0x02: read a sector
   movb $0x01, %al     # sectors to read count
@@ -192,12 +187,14 @@ pusha
   int $0x13
   jc load_error
 
-  movw $load_debug_return, %si
-  call print
-  movb %ah, %al
-  xorb %ah, %ah
-  call print_hex_int16
-  movw $newline, %si
+  # movw $load_debug_return, %si
+  # call print
+  # movb %ah, %al
+  # xorb %ah, %ah
+  # call print_hex_int16
+  # movw $newline, %si
+  # call print
+  movw $load_msg_dot, %si
   call print
 
   popa
@@ -261,9 +258,13 @@ .ascii "Resetting bootdrive..."
   .byte 0
 
 load_msg: 
-  .ascii "Loading kernel..."
-  .byte 13
-  .byte 10
+  .ascii "Loading kernel"
+  # .byte 13
+  # .byte 10
+  .byte 0
+
+load_msg_dot:
+  .ascii "."
   .byte 0
 
 load_debug_msg:

M src/boot/entry.s → src/boot/entry.s

@@ -138,6 +138,8 @@ call enable_a20
 
   call reset_drive
 
+  call find_bootable_part
+
   call load_kernel
 
   movw $gdt_msg, %si

M src/boot/link.txt → src/boot/link.txt

@@ -3,6 +3,8 @@ OUTPUT_FORMAT(binary)
 
 PAGE_SIZE = 1 << 12;
 
+PART_TABLE_START = 0x00007DBE;
+
 MEMORY
 {
   BOOT_VMA    :   ORIGIN = 0x00007C00, LENGTH = 0x00001000

A src/boot/mbr.s

@@ -0,0 +1,89 @@
+.code16
+.section .text
+.global find_bootable_part
+find_bootable_part:
+  movw $0x0000, %ax
+  movw %ax, %ds
+
+  movw $0x0000, %cx
+
+find_part_loop:
+  movw $mbr_partition_msg, %si
+  call print
+  movw %cx, %ax
+  call print_hex_int16
+  movw $newline, %si
+  call print
+
+  movw $PART_TABLE_START, %si
+  
+  xor %ax, %ax
+  movb (%si), %al
+
+  cmp $0x80, %al
+  je find_part_loop_end
+
+  # TODO: loop over partitions
+  jmp find_part_loop_fail
+
+find_part_loop_end:
+  movw $mbr_bootable_msg, %si
+  call print
+  movw %cx, %ax
+  call print_hex_int16
+  movw $newline, %si
+  call print
+
+  # load partition size from MBR
+  movw $PART_TABLE_START, %si
+  add $0x0C, %si
+
+  movw (%si), %cx
+
+  movw $mbr_size_msg, %si
+  call print
+  movw %cx, %ax
+  call print_hex_int16
+  movw $newline, %si
+  call print
+
+  # load partition start from MBR
+  movw $PART_TABLE_START, %si
+  add $0x08, %si
+
+  movw (%si), %ax
+
+  movw $mbr_start_msg, %si
+  call print
+  call print_hex_int16
+  movw $newline, %si
+  call print
+
+  add %ax, %cx
+
+  ret
+
+find_part_loop_fail:
+  jmp error
+
+.section .data
+mbr_partition_msg:
+  .ascii "  Checking partition 0x"
+  .byte
+
+mbr_bootable_msg:
+  .ascii "  bootable partition found: 0x"
+  .byte 0
+
+mbr_start_msg:
+  .ascii "  Start sector: 0x"
+  .byte 0
+
+mbr_size_msg:
+  .ascii "  Number of sectors: 0x"
+  .byte 0
+
+newline:
+  .byte 13
+  .byte 10
+  .byte 0