Bootloader: Split bootloader into multiple files
This cleans up the code since bootloader is starting to near 1k lines
This commit is contained in:
parent
055b1a2a1a
commit
b0b39c56ba
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@ -1,10 +1,3 @@
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# FIXME: don't assume 512 byte sectors
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.set SECTOR_SIZE_SHIFT, 9
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.set SECTOR_SIZE, 1 << SECTOR_SIZE_SHIFT
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.set SCREEN_WIDTH, 80
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.set SCREEN_HEIGHT, 25
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.code16
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#########################################
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@ -18,166 +11,7 @@
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.section .stage1
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stage1_start:
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jmp stage1_main
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# prints character to screen
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# al: ascii character to print
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putc:
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pusha
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movb $0x0E, %ah
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movb $0x00, %bh
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int $0x10
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popa
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ret
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# prints null terminated string to screen
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# ds:si: string address
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puts:
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pushw %si
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pushw %bx
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pushw %ax
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movb $0x0E, %ah
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movb $0x00, %bh
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.puts_loop:
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lodsb
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test %al, %al
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jz .puts_done
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int $0x10
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jmp .puts_loop
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.puts_done:
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popw %ax
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popw %bx
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popw %si
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ret
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# compares memory between addresses
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# si: ptr1
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# di: ptr2
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# cx: bytes count
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# return:
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# al: 1 if equal, 0 otherwise
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memcmp:
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pushw %si
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pushw %di
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cld
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repe cmpsb
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setzb %al
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popw %di
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popw %si
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ret
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# read sectors from disk
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# bx:eax: lba start
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# cx: lba count (has to less than 0x80)
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# dl: drive number
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# ds:di: physical address
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# returns only on success
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read_from_disk:
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push %ax
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push %si
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# prepare disk read packet
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mov $disk_address_packet, %si
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movb $0x10, 0x00(%si) # packet size
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movb $0x00, 0x01(%si) # always 0
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movw %cx, 0x02(%si) # lba count
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movw %di, 0x04(%si) # offset
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movw %ds, 0x06(%si) # segment
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movl %eax, 0x08(%si) # 32 bit lower lba
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movw %bx, 0x0C(%si) # 16 bit upper lba
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movw $0, 0x0E(%si) # zero
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# issue read command
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clc
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mov $0x42, %ah
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int $0x13
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jc .read_failed
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pop %si
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pop %ax
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ret
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# Validates that GPT header is valid and usable
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# doesn't return on invalid header
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validate_gpt_header:
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# confirm header (starts with 'EFI PART')
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cmpl $0x20494645, (gpt_header + 0)
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jne .not_gpt_partition
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cmpl $0x54524150, (gpt_header + 4)
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jne .not_gpt_partition
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ret
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# Find partition entry with type guid
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# si: address of type guid
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# dl: drive number
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# returns:
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# al: non-zero if found
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# di: address of partition entry
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find_gpt_partition_entry:
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# eax := entry_count
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movl (gpt_header + 80), %eax
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test %eax, %eax
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jz .no_gpt_partition_found
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# edx:eax := eax * entry_size
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pushw %dx
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mull (gpt_header + 84)
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test %edx, %edx
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jnz .too_gpt_big_entries
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popw %dx
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# FIXME: read one entry array section at a time
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# sector count := (arr_size + SECTOR_SIZE - 1) / SECTOR_SIZE
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movl %eax, %ecx
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shrl $SECTOR_SIZE_SHIFT, %ecx
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# start lba
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movl (gpt_header + 72), %eax
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movw (gpt_header + 76), %bx
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movw $gpt_entry_data, %di
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call read_from_disk
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# NOTE: 'only' 0xFFFF partitions supported,
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# although read will fail with more than 0x80
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movw (gpt_header + 80), %cx
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.loop_gpt_entries:
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pushw %cx
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movw $16, %cx
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call memcmp
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popw %cx
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testb %al, %al
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jnz .gpt_partition_found
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# add entry size to entry pointer
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addw (gpt_header + 84), %di
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loop .loop_gpt_entries
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.no_gpt_partition_found:
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movb $0, %al
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ret
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.gpt_partition_found:
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movb $1, %al
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ret
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.global stage1_main
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stage1_main:
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# setup segments
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movw $0, %ax
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@ -189,107 +23,17 @@ stage1_main:
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movl $0x7C00, %esp
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# save boot disk number
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movb %dl, (boot_disk_number)
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call read_stage2_into_memory
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# FIXME: validate boot disk (needs size optizations)
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# confirm that int 13h extensions are available
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clc
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movb $0x41, %ah
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movw $0x55AA, %bx
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movb (boot_disk_number), %dl
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int $0x13
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jc .no_int13h_ext
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# read gpt header
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movl $1, %eax
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movw $0, %bx
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movw $1, %cx
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movb (boot_disk_number), %dl
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movw $gpt_header, %di
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call read_from_disk
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call validate_gpt_header
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movw $bios_boot_guid, %si
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movb boot_disk_number, %dl
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call find_gpt_partition_entry
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testb %al, %al
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jz .no_bios_boot_partition
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# BIOS boot partiton found!
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# first lba
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movl 32(%di), %eax
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movw $0, %bx
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# count := last lba - first lba + 1
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movl 40(%di), %ecx
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subl %eax, %ecx
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addl $1, %ecx
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# calculate stage2 sector count
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movw $((stage2_end - stage2_start + SECTOR_SIZE - 1) / SECTOR_SIZE), %cx
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movb (boot_disk_number), %dl
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movw $stage2_start, %di
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call read_from_disk
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jmp stage2_main
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.global print_and_halt
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print_and_halt:
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call puts
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halt:
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hlt
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jmp halt
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.no_int13h_ext:
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mov $no_int13_ext_msg, %si
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jmp print_and_halt
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.read_failed:
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mov $read_failed_msg, %si
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jmp print_and_halt
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.not_gpt_partition:
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mov $not_gpt_partition_msg, %si
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jmp print_and_halt
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.no_bios_boot_partition:
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mov $no_bios_boot_partition_msg, %si
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jmp print_and_halt
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.too_gpt_big_entries:
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mov $too_gpt_big_entries_msg, %si
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jmp print_and_halt
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# 21686148-6449-6E6F-744E-656564454649
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bios_boot_guid:
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.long 0x21686148 # little endian
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.word 0x6449 # little endian
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.word 0x6E6F # little endian
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.word 0x4E74 # big endian
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.quad 0x494645646565 # big endian
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no_int13_ext_msg:
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.asciz "no INT 13h ext"
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read_failed_msg:
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.asciz "read error"
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not_gpt_partition_msg:
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.asciz "not GPT"
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no_bios_boot_partition_msg:
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.asciz "no bios boot partition"
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too_gpt_big_entries_msg:
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.asciz "too big GPT array"
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boot_disk_number:
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.skip 1
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#########################################
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#
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@ -299,477 +43,6 @@ boot_disk_number:
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.section .stage2
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stage2_start:
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# read a character from keyboard
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# return:
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# al: ascii
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# ah: bios scan code
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getc:
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movb $0x00, %ah
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int $0x16
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ret
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# prints newline to screen
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print_newline:
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pushw %ax
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movb $'\r', %al
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call putc
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movb $'\n', %al
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call putc
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pop %ax
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ret
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# prints backspace to screen, can go back a line
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print_backspace:
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pusha
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# get cursor position
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movb $0x03, %ah
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movb $0x00, %bh
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int $0x10
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# don't do anyting if on first row
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testb %dh, %dh
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jz .print_backspace_done
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# go one line up if on first column
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test %dl, %dl
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jz .print_backspace_go_line_up
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# otherwise decrease column
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decb %dl
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jmp .print_backspace_do_print
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.print_backspace_go_line_up:
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# decrease row and set column to the last one
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decb %dh
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movb $(SCREEN_WIDTH - 1), %dl
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.print_backspace_do_print:
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# set cursor position
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movb $0x02, %ah
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int $0x10
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# print 'empty' character (space)
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mov $' ', %al
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call putc
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# set cursor position
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movb $0x02, %ah
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int $0x10
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.print_backspace_done:
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popa
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ret
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# print number to screen
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# ax: number to print
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# bx: number base
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# cx: min width (zero pads if shorter)
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printnum:
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pusha
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pushw %cx
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movw $printnum_buffer, %si
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xorw %cx, %cx
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.printnum_fill_loop:
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# fill buffer with all remainders ax % bx
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xorw %dx, %dx
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divw %bx
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movb %dl, (%si)
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incw %si
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incw %cx
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testw %ax, %ax
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jnz .printnum_fill_loop
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# check if zero pad is required
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popw %dx
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cmpw %cx, %dx
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jbe .printnum_print_loop
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xchgw %dx, %cx
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subw %dx, %cx
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movb $'0', %al
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.printnum_pad_zeroes:
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call putc
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loop .printnum_pad_zeroes
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movw %dx, %cx
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.printnum_print_loop:
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decw %si
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movb (%si), %al
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cmpb $10, %al
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jae 1f
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addb $'0', %al
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jmp 2f
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1: addb $('a' - 10), %al
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2: call putc
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loop .printnum_print_loop
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popa
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ret
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# test if character is printable ascii
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# al: character to test
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# sets ZF if is printable
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isprint:
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cmpb $0x20, %al
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jb .isprint_done
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cmpb $0x7E, %al
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ja .isprint_done
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cmpb %al, %al
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.isprint_done:
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ret
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# check if drive exists
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# dl: drive number
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# return:
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# al: 1 if disk is usable, 0 otherwise
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drive_exists:
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pusha
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movb $0x48, %ah
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movw $disk_drive_parameters, %si
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movw $0x1A, (disk_drive_parameters) # set buffer size
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clc
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int $0x13
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jc .drive_exists_nope
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popa
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movb $1, %al
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ret
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.drive_exists_nope:
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popa
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movb $0, %al
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ret
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# fills memory map data structure
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# doesn't return on error
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# NO REGISTERS SAVED
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get_memory_map:
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movl $0, (memory_map_entry_count)
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movl $0x0000E820, %eax
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movl $0x534D4150, %edx
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xorl %ebx, %ebx
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movl $20, %ecx
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movw $memory_map_entries, %di
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clc
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int $0x15
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# If first call returs with CF set, the call failed
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jc .get_memory_map_error
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.get_memory_map_rest:
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cmpl $0x534D4150, %eax
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jne .get_memory_map_error
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# FIXME: don't assume BIOS to always return 20 bytes
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cmpl $20, %ecx
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jne .get_memory_map_error
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# increment entry count
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incl (memory_map_entry_count)
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# increment entry pointer
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addw %cx, %di
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# BIOS can indicate end of list by 0 in ebx
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testl %ebx, %ebx
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jz .get_memory_map_done
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movl $0x0000E820, %eax
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movl $0x534D4150, %edx
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clc
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int $0x15
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# BIOS can indicate end of list by setting CF
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jnc .get_memory_map_rest
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.get_memory_map_done:
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ret
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.get_memory_map_error:
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movw $memory_map_error_msg, %si
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jmp print_and_halt
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# fills command line buffer
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# NO REGISTERS SAVED
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get_command_line:
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movw $command_line_enter_msg, %si
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call puts
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movw $command_line_buffer, %di
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.get_command_line_loop:
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call getc
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cmpb $'\b', %al
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je .get_command_line_backspace
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# Not sure if some BIOSes return '\n' as enter, but check it just in case
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cmpb $'\r', %al
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je .get_command_line_done
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cmpb $'\n', %al
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je .get_command_line_done
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call isprint
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jnz .get_command_line_loop
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# put byte to buffer
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movb %al, (%di)
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incw %di
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# print byte
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call putc
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jmp .get_command_line_loop
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.get_command_line_backspace:
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# don't do anything if at the beginning
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cmpw $command_line_buffer, %di
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je .get_command_line_loop
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# decrement buffer pointer
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decw %di
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# erase byte in display
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call print_backspace
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jmp .get_command_line_loop
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.get_command_line_done:
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# null terminate command line
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movb $0, (%di)
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call print_newline
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ret
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# print memory map from memory_map_entries
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# NO REGISTERS SAVED
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print_memory_map:
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movw $memory_map_msg, %si
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call puts
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call print_newline
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movl (memory_map_entry_count), %edx
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movw $memory_map_entries, %si
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movw $16, %bx
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movw $4, %cx
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.loop_memory_map:
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movb $' ', %al
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call putc
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call putc
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call putc
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call putc
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||||
|
||||
movw 0x06(%si), %ax
|
||||
call printnum
|
||||
movw 0x04(%si), %ax
|
||||
call printnum
|
||||
movw 0x02(%si), %ax
|
||||
call printnum
|
||||
movw 0x00(%si), %ax
|
||||
call printnum
|
||||
|
||||
movb $',', %al
|
||||
call putc
|
||||
movb $' ', %al
|
||||
call putc
|
||||
|
||||
movw 0x0E(%si), %ax
|
||||
call printnum
|
||||
movw 0x0C(%si), %ax
|
||||
call printnum
|
||||
movw 0x0A(%si), %ax
|
||||
call printnum
|
||||
movw 0x08(%si), %ax
|
||||
call printnum
|
||||
|
||||
movb $',', %al
|
||||
call putc
|
||||
movb $' ', %al
|
||||
call putc
|
||||
|
||||
movw 0x12(%si), %ax
|
||||
call printnum
|
||||
movw 0x10(%si), %ax
|
||||
call printnum
|
||||
|
||||
call print_newline
|
||||
|
||||
addw $20, %si
|
||||
|
||||
decl %edx
|
||||
jnz .loop_memory_map
|
||||
|
||||
ret
|
||||
|
||||
|
||||
# find root disk and populate root_disk_drive_number field
|
||||
# NO REGISTERS SAVED
|
||||
find_root_disk:
|
||||
movb $0x80, %dl
|
||||
|
||||
.find_root_disk_loop:
|
||||
call drive_exists
|
||||
testb %al, %al
|
||||
jz .find_root_disk_not_found
|
||||
|
||||
# read GPT header
|
||||
xorw %bx, %bx
|
||||
movl $1, %eax
|
||||
movw $1, %cx
|
||||
movw $gpt_header, %di
|
||||
call read_from_disk
|
||||
|
||||
# confirm header (starts with 'EFI PART')
|
||||
cmpl $0x20494645, (gpt_header + 0)
|
||||
jne .find_root_disk_next_disk
|
||||
cmpl $0x54524150, (gpt_header + 4)
|
||||
jne .find_root_disk_next_disk
|
||||
|
||||
# compare disk GUID
|
||||
movw $root_disk_guid, %si
|
||||
movw $(gpt_header + 56), %di
|
||||
movw $16, %cx
|
||||
call memcmp
|
||||
testb %al, %al
|
||||
jz .find_root_disk_next_disk
|
||||
|
||||
movb %dl, (root_disk_drive_number)
|
||||
ret
|
||||
|
||||
.find_root_disk_next_disk:
|
||||
incb %dl
|
||||
jmp .find_root_disk_loop
|
||||
|
||||
.find_root_disk_not_found:
|
||||
movw $no_root_disk_msg, %si
|
||||
jmp print_and_halt
|
||||
|
||||
|
||||
# finds root partition from root disk
|
||||
# fills root_partition_entry data structure
|
||||
# NOTE: assumes GPT header is in `gpt_header`
|
||||
# NO REGISTERS SAVED
|
||||
find_root_partition:
|
||||
pushl %ebp
|
||||
movl %esp, %ebp
|
||||
subl $16, %esp
|
||||
|
||||
# esp + 0: 8 byte entry array lba
|
||||
movl (gpt_header + 72), %eax
|
||||
movl %eax, 0(%esp)
|
||||
movl (gpt_header + 76), %eax
|
||||
movl %eax, 4(%esp)
|
||||
# FIXME: check that bits 48-63 are zero
|
||||
|
||||
# esp + 8: 4 byte entries per sector
|
||||
xorl %edx, %edx
|
||||
movl $SECTOR_SIZE, %eax
|
||||
divl (gpt_header + 84)
|
||||
movl %eax, 8(%esp)
|
||||
|
||||
# esp + 12: 4 byte entries remaining
|
||||
movl (gpt_header + 80), %eax
|
||||
testl %eax, %eax
|
||||
jz .find_root_partition_not_found
|
||||
movl %eax, 12(%esp)
|
||||
|
||||
.find_root_partition_read_entry_section:
|
||||
movl 0(%esp), %eax
|
||||
movl 4(%esp), %ebx
|
||||
movw $1, %cx
|
||||
movb (root_disk_drive_number), %dl
|
||||
movw $sector_buffer, %di
|
||||
call read_from_disk
|
||||
|
||||
# ecx: min(entries per section, entries remaining)
|
||||
movl 8(%esp), %ecx
|
||||
cmpl 12(%esp), %ecx
|
||||
jae .find_root_partition_got_entry_count
|
||||
movl 12(%esp), %ecx
|
||||
|
||||
.find_root_partition_got_entry_count:
|
||||
# update entries remaining
|
||||
subl %ecx, 12(%esp)
|
||||
|
||||
# si: entry pointer
|
||||
movw $sector_buffer, %si
|
||||
|
||||
.find_root_partition_loop_entries:
|
||||
# temporarily save cx in dx
|
||||
movw %cx, %dx
|
||||
|
||||
# check that entry is used
|
||||
movw $16, %cx
|
||||
movw $zero_guid, %di
|
||||
call memcmp
|
||||
test %al, %al
|
||||
jnz .find_root_partition_next_entry
|
||||
|
||||
# compare entry guid to root guid
|
||||
movw $16, %cx
|
||||
addw $16, %si
|
||||
movw $root_partition_guid, %di
|
||||
call memcmp
|
||||
subw $16, %si
|
||||
|
||||
testb %al, %al
|
||||
jnz .find_root_partition_found
|
||||
|
||||
.find_root_partition_next_entry:
|
||||
|
||||
# restore cx
|
||||
movw %dx, %cx
|
||||
|
||||
# entry pointer += entry size
|
||||
addw (gpt_header + 84), %si
|
||||
loop .find_root_partition_loop_entries
|
||||
|
||||
# entry not found in this sector
|
||||
|
||||
# increment 8 byte entry array lba
|
||||
incl 0(%esp)
|
||||
jno .find_root_partition_no_overflow
|
||||
incl 4(%esp)
|
||||
|
||||
.find_root_partition_no_overflow:
|
||||
# loop to read next section if entries remaining
|
||||
cmpl $0, 12(%esp)
|
||||
jnz .find_root_partition_read_entry_section
|
||||
|
||||
.find_root_partition_not_found:
|
||||
movw $no_root_partition_msg, %si
|
||||
jmp print_and_halt
|
||||
|
||||
.find_root_partition_found:
|
||||
# copy entry to buffer
|
||||
movw $root_partition_entry, %di
|
||||
movw $128, %cx
|
||||
rep movsb
|
||||
|
||||
leavel
|
||||
ret
|
||||
|
||||
|
||||
stage2_main:
|
||||
# clear screen and enter 80x25 text mode
|
||||
movb $0x03, %al
|
||||
|
|
@ -781,7 +54,7 @@ stage2_main:
|
|||
call puts; call print_newline
|
||||
|
||||
call get_memory_map
|
||||
call get_command_line
|
||||
call read_user_command_line
|
||||
|
||||
call print_newline
|
||||
|
||||
|
|
@ -791,101 +64,14 @@ stage2_main:
|
|||
call print_memory_map
|
||||
|
||||
call find_root_disk
|
||||
movw $root_disk_found_msg, %si
|
||||
call puts; call print_newline
|
||||
|
||||
call find_root_partition
|
||||
movw $root_partition_found_msg, %si
|
||||
call puts; call print_newline
|
||||
|
||||
movw $16, %bx
|
||||
movw $2, %cx
|
||||
movw (root_partition_entry + 38), %ax; call printnum
|
||||
movw (root_partition_entry + 36), %ax; call printnum
|
||||
movw (root_partition_entry + 34), %ax; call printnum
|
||||
movw (root_partition_entry + 32), %ax; call printnum
|
||||
|
||||
movb $'-', %al; call putc
|
||||
movb $'>', %al; call putc
|
||||
|
||||
movw (root_partition_entry + 46), %ax; call printnum
|
||||
movw (root_partition_entry + 44), %ax; call printnum
|
||||
movw (root_partition_entry + 42), %ax; call printnum
|
||||
movw (root_partition_entry + 40), %ax; call printnum
|
||||
call print_root_partition_info
|
||||
|
||||
jmp halt
|
||||
|
||||
|
||||
# These will be patched during bootloader installation
|
||||
root_disk_guid:
|
||||
.ascii "root disk guid "
|
||||
root_partition_guid:
|
||||
.ascii "root part guid "
|
||||
zero_guid:
|
||||
.quad 0
|
||||
.quad 0
|
||||
|
||||
hello_msg:
|
||||
.asciz "This is banan-os bootloader"
|
||||
|
||||
command_line_msg:
|
||||
command_line_enter_msg:
|
||||
.asciz "cmdline: "
|
||||
|
||||
memory_map_msg:
|
||||
.asciz "memmap:"
|
||||
|
||||
memory_map_error_msg:
|
||||
.asciz "Failed to get memory map"
|
||||
|
||||
start_kernel_load_msg:
|
||||
.asciz "Starting to load kernel"
|
||||
|
||||
root_disk_found_msg:
|
||||
.asciz "Root disk found!"
|
||||
no_root_disk_msg:
|
||||
.asciz "Root disk not found"
|
||||
|
||||
root_partition_found_msg:
|
||||
.asciz "Root partition found!"
|
||||
no_root_partition_msg:
|
||||
.asciz "Root partition not found"
|
||||
|
||||
stage2_end:
|
||||
|
||||
|
||||
.section .bss
|
||||
|
||||
.align SECTOR_SIZE
|
||||
gpt_header:
|
||||
.skip SECTOR_SIZE
|
||||
gpt_entry_data:
|
||||
.skip SECTOR_SIZE
|
||||
|
||||
sector_buffer:
|
||||
.skip SECTOR_SIZE
|
||||
|
||||
disk_drive_parameters:
|
||||
.skip 0x1A
|
||||
|
||||
disk_address_packet:
|
||||
.skip 16
|
||||
|
||||
printnum_buffer:
|
||||
.skip 10
|
||||
|
||||
root_disk_drive_number:
|
||||
.skip 1
|
||||
|
||||
root_partition_entry:
|
||||
.skip 128
|
||||
|
||||
memory_map_entry_count:
|
||||
.skip 4
|
||||
# 100 entries should be enough...
|
||||
memory_map_entries:
|
||||
.skip 20 * 100
|
||||
|
||||
# 100 character command line
|
||||
command_line_buffer:
|
||||
.skip 100
|
||||
|
|
|
|||
|
|
@ -0,0 +1,69 @@
|
|||
.code16
|
||||
|
||||
.section .stage2
|
||||
|
||||
# fills command line buffer
|
||||
# NO REGISTERS SAVED
|
||||
.global read_user_command_line
|
||||
read_user_command_line:
|
||||
movw $command_line_enter_msg, %si
|
||||
call puts
|
||||
|
||||
movw $command_line_buffer, %di
|
||||
|
||||
.read_user_command_line_loop:
|
||||
call getc
|
||||
|
||||
cmpb $'\b', %al
|
||||
je .read_user_command_line_backspace
|
||||
|
||||
# Not sure if some BIOSes return '\n' as enter, but check it just in case
|
||||
cmpb $'\r', %al
|
||||
je .read_user_command_line_done
|
||||
cmpb $'\n', %al
|
||||
je .read_user_command_line_done
|
||||
|
||||
call isprint
|
||||
testb %al, %al
|
||||
jnz .read_user_command_line_loop
|
||||
|
||||
# put byte to buffer
|
||||
movb %al, (%di)
|
||||
incw %di
|
||||
|
||||
# print byte
|
||||
call putc
|
||||
|
||||
jmp .read_user_command_line_loop
|
||||
|
||||
.read_user_command_line_backspace:
|
||||
# don't do anything if at the beginning
|
||||
cmpw $command_line_buffer, %di
|
||||
je .read_user_command_line_loop
|
||||
|
||||
# decrement buffer pointer
|
||||
decw %di
|
||||
|
||||
# erase byte in display
|
||||
call print_backspace
|
||||
|
||||
jmp .read_user_command_line_loop
|
||||
|
||||
.read_user_command_line_done:
|
||||
# null terminate command line
|
||||
movb $0, (%di)
|
||||
|
||||
call print_newline
|
||||
|
||||
ret
|
||||
|
||||
|
||||
command_line_enter_msg:
|
||||
.asciz "cmdline: "
|
||||
|
||||
|
||||
.section .bss
|
||||
|
||||
# 100 character command line
|
||||
command_line_buffer:
|
||||
.skip 100
|
||||
|
|
@ -0,0 +1,491 @@
|
|||
# FIXME: don't assume 512 byte sectors
|
||||
.set SECTOR_SIZE_SHIFT, 9
|
||||
.set SECTOR_SIZE, 1 << SECTOR_SIZE_SHIFT
|
||||
|
||||
.code16
|
||||
|
||||
.section .stage1
|
||||
|
||||
.global stage2_start
|
||||
.global stage2_end
|
||||
|
||||
# check that drive has int13 ext
|
||||
# dl: drive number
|
||||
# returns only if drive does have the extension
|
||||
drive_has_int13_ext:
|
||||
pusha
|
||||
|
||||
movb $0x41, %ah
|
||||
movw $0x55AA, %bx
|
||||
int $0x13
|
||||
jc .drive_has_int13_ext_no_int13_ext
|
||||
|
||||
popa
|
||||
ret
|
||||
|
||||
.drive_has_int13_ext_no_int13_ext:
|
||||
mov $no_int13_ext_msg, %si
|
||||
jmp print_and_halt
|
||||
|
||||
|
||||
# read sectors from disk
|
||||
# bx:eax: lba start
|
||||
# cx: lba count (has to less than 0x80)
|
||||
# dl: drive number
|
||||
# ds:di: physical address
|
||||
# returns only on success
|
||||
.global read_from_disk
|
||||
read_from_disk:
|
||||
pusha
|
||||
|
||||
call drive_has_int13_ext
|
||||
|
||||
# prepare disk read packet
|
||||
mov $disk_address_packet, %si
|
||||
movb $0x10, 0x00(%si) # packet size
|
||||
movb $0x00, 0x01(%si) # always 0
|
||||
movw %cx, 0x02(%si) # lba count
|
||||
movw %di, 0x04(%si) # offset
|
||||
movw %ds, 0x06(%si) # segment
|
||||
movl %eax, 0x08(%si) # 32 bit lower lba
|
||||
movw %bx, 0x0C(%si) # 16 bit upper lba
|
||||
movw $0, 0x0E(%si) # zero
|
||||
|
||||
# issue read command
|
||||
mov $0x42, %ah
|
||||
int $0x13
|
||||
jc .read_from_disk_failed
|
||||
|
||||
popa
|
||||
ret
|
||||
|
||||
.read_from_disk_failed:
|
||||
mov $read_from_disk_msg, %si
|
||||
jmp print_and_halt
|
||||
|
||||
|
||||
# Reads GPT header into gpt_header buffer
|
||||
# dl: drive number
|
||||
# return:
|
||||
# ax: 1 if has GPT header, 0 otherwise
|
||||
.global read_gpt_header
|
||||
read_gpt_header:
|
||||
pushw %bx
|
||||
pushw %cx
|
||||
pushw %di
|
||||
|
||||
xorw %bx, %bx
|
||||
movl $1, %eax
|
||||
movw $1, %cx
|
||||
movw $gpt_header, %di
|
||||
call read_from_disk
|
||||
|
||||
xorw %bx, %bx
|
||||
movw $1, %ax
|
||||
|
||||
# check if header starts with 'EFI PART'
|
||||
cmpl $0x20494645, (gpt_header + 0)
|
||||
cmovnew %bx, %ax
|
||||
cmpl $0x54524150, (gpt_header + 4)
|
||||
cmovnew %bx, %ax
|
||||
|
||||
popw %di
|
||||
popw %cx
|
||||
popw %bx
|
||||
ret
|
||||
|
||||
|
||||
# Find bios boot partition from boot drive
|
||||
# returns:
|
||||
# bx:eax: first lba
|
||||
# cx: sector count
|
||||
find_stage2_partition:
|
||||
# read boot disk GPT header
|
||||
movb (boot_disk_number), %dl
|
||||
call read_gpt_header
|
||||
|
||||
testb %al, %al
|
||||
jz .find_stage2_partition_not_gpt
|
||||
|
||||
# eax := entry_count
|
||||
movl (gpt_header + 80), %eax
|
||||
test %eax, %eax
|
||||
jz .find_stage2_partition_not_found
|
||||
|
||||
# edx:eax := eax * entry_size
|
||||
mull (gpt_header + 84)
|
||||
test %edx, %edx
|
||||
jnz .find_stage2_partition_too_big_entries
|
||||
|
||||
# FIXME: read one entry array section at a time
|
||||
|
||||
# sector count := (arr_size + SECTOR_SIZE - 1) / SECTOR_SIZE
|
||||
movl %eax, %ecx
|
||||
shrl $SECTOR_SIZE_SHIFT, %ecx
|
||||
|
||||
# start lba
|
||||
movl (gpt_header + 72), %eax
|
||||
movw (gpt_header + 76), %bx
|
||||
|
||||
movw $gpt_entry_data, %di
|
||||
movw $bios_boot_guid, %si
|
||||
movb (boot_disk_number), %dl
|
||||
|
||||
call read_from_disk
|
||||
|
||||
# NOTE: 'only' 0xFFFF partitions supported,
|
||||
# although read will fail with more than 0x80
|
||||
movw (gpt_header + 80), %cx
|
||||
|
||||
.find_stage2_partition_loop_gpt_entries:
|
||||
pushw %cx
|
||||
movw $16, %cx
|
||||
call memcmp
|
||||
popw %cx
|
||||
|
||||
testb %al, %al
|
||||
jnz .find_stage2_partition_found
|
||||
|
||||
# add entry size to entry pointer
|
||||
addw (gpt_header + 84), %di
|
||||
|
||||
loop .find_stage2_partition_loop_gpt_entries
|
||||
|
||||
# fall through to not found case
|
||||
.find_stage2_partition_not_found:
|
||||
movw $no_bios_boot_partition_msg, %si
|
||||
jmp print_and_halt
|
||||
|
||||
.find_stage2_partition_not_gpt:
|
||||
movw $not_gpt_partition_msg, %si
|
||||
jmp print_and_halt
|
||||
|
||||
.find_stage2_partition_too_big_entries:
|
||||
movw $too_gpt_big_entries_msg, %si
|
||||
jmp print_and_halt
|
||||
|
||||
.find_stage2_partition_found:
|
||||
# first lba
|
||||
movl 32(%di), %eax
|
||||
movw 36(%di), %bx
|
||||
|
||||
# count := last lba - first lba + 1
|
||||
movl 40(%di), %ecx
|
||||
subl %eax, %ecx
|
||||
incl %ecx
|
||||
|
||||
ret
|
||||
|
||||
# reads stage2 into memory
|
||||
# dl: boot drive number
|
||||
# returns only on success
|
||||
.global read_stage2_into_memory
|
||||
read_stage2_into_memory:
|
||||
movb %dl, (boot_disk_number)
|
||||
|
||||
# push stage2 sector count
|
||||
movl $stage2_end, %eax
|
||||
subl $stage2_start, %eax
|
||||
addl $(SECTOR_SIZE - 1), %eax
|
||||
movl $SECTOR_SIZE, %ecx
|
||||
xorl %edx, %edx
|
||||
divl %ecx
|
||||
pushl %eax
|
||||
|
||||
call find_stage2_partition
|
||||
|
||||
movb (boot_disk_number), %dl
|
||||
popl %ecx # FIXME: validate that partition has enough sectors
|
||||
movw $stage2_start, %di
|
||||
call read_from_disk
|
||||
|
||||
ret
|
||||
|
||||
# 21686148-6449-6E6F-744E-656564454649
|
||||
.align 4
|
||||
bios_boot_guid:
|
||||
.long 0x21686148 # little endian
|
||||
.word 0x6449 # little endian
|
||||
.word 0x6E6F # little endian
|
||||
.word 0x4E74 # big endian
|
||||
.quad 0x494645646565 # big endian
|
||||
|
||||
boot_disk_number:
|
||||
.skip 1
|
||||
|
||||
read_from_disk_msg:
|
||||
.asciz "read error"
|
||||
|
||||
no_int13_ext_msg:
|
||||
.asciz "no INT13 ext"
|
||||
|
||||
no_bios_boot_partition_msg:
|
||||
.asciz "no bios boot"
|
||||
|
||||
too_gpt_big_entries_msg:
|
||||
.asciz "too big GPT array"
|
||||
|
||||
not_gpt_partition_msg:
|
||||
.asciz "not GPT"
|
||||
|
||||
|
||||
.section .stage2
|
||||
|
||||
# check if drive exists
|
||||
# dl: drive number
|
||||
# return:
|
||||
# al: 1 if disk is usable, 0 otherwise
|
||||
drive_exists:
|
||||
pusha
|
||||
|
||||
movb $0x48, %ah
|
||||
movw $disk_drive_parameters, %si
|
||||
movw $0x1A, (disk_drive_parameters) # set buffer size
|
||||
|
||||
int $0x13
|
||||
jc .drive_exists_nope
|
||||
|
||||
popa
|
||||
movb $1, %al
|
||||
ret
|
||||
|
||||
.drive_exists_nope:
|
||||
popa
|
||||
movb $0, %al
|
||||
ret
|
||||
|
||||
# find root disk and populate root_disk_drive_number field
|
||||
# NO REGISTERS SAVED
|
||||
.global find_root_disk
|
||||
find_root_disk:
|
||||
movb $0x80, %dl
|
||||
|
||||
.find_root_disk_loop:
|
||||
call drive_exists
|
||||
testb %al, %al
|
||||
jz .find_root_disk_not_found
|
||||
|
||||
# read GPT header
|
||||
xorw %bx, %bx
|
||||
movl $1, %eax
|
||||
movw $1, %cx
|
||||
movw $gpt_header, %di
|
||||
call read_from_disk
|
||||
|
||||
# confirm header (starts with 'EFI PART')
|
||||
cmpl $0x20494645, (gpt_header + 0)
|
||||
jne .find_root_disk_next_disk
|
||||
cmpl $0x54524150, (gpt_header + 4)
|
||||
jne .find_root_disk_next_disk
|
||||
|
||||
# compare disk GUID
|
||||
movw $root_disk_guid, %si
|
||||
movw $(gpt_header + 56), %di
|
||||
movw $16, %cx
|
||||
call memcmp
|
||||
testb %al, %al
|
||||
jz .find_root_disk_next_disk
|
||||
|
||||
movw $root_disk_found_msg, %si
|
||||
call puts; call print_newline
|
||||
|
||||
movb %dl, (root_disk_drive_number)
|
||||
ret
|
||||
|
||||
.find_root_disk_next_disk:
|
||||
incb %dl
|
||||
jmp .find_root_disk_loop
|
||||
|
||||
.find_root_disk_not_found:
|
||||
movw $root_disk_not_found_msg, %si
|
||||
jmp print_and_halt
|
||||
|
||||
|
||||
# finds root partition from root disk
|
||||
# fills root_partition_entry data structure
|
||||
# NOTE: assumes GPT header is in `gpt_header`
|
||||
# NO REGISTERS SAVED
|
||||
.global find_root_partition
|
||||
find_root_partition:
|
||||
pushl %ebp
|
||||
movl %esp, %ebp
|
||||
subl $16, %esp
|
||||
|
||||
# esp + 0: 8 byte entry array lba
|
||||
movl (gpt_header + 72), %eax
|
||||
movl %eax, 0(%esp)
|
||||
movl (gpt_header + 76), %eax
|
||||
movl %eax, 4(%esp)
|
||||
# FIXME: check that bits 48-63 are zero
|
||||
|
||||
# esp + 8: 4 byte entries per sector
|
||||
xorl %edx, %edx
|
||||
movl $SECTOR_SIZE, %eax
|
||||
divl (gpt_header + 84)
|
||||
movl %eax, 8(%esp)
|
||||
|
||||
# esp + 12: 4 byte entries remaining
|
||||
movl (gpt_header + 80), %eax
|
||||
testl %eax, %eax
|
||||
jz .find_root_partition_not_found
|
||||
movl %eax, 12(%esp)
|
||||
|
||||
.find_root_partition_read_entry_section:
|
||||
movl 0(%esp), %eax
|
||||
movl 4(%esp), %ebx
|
||||
movw $1, %cx
|
||||
movb (root_disk_drive_number), %dl
|
||||
movw $sector_buffer, %di
|
||||
call read_from_disk
|
||||
|
||||
# ecx: min(entries per section, entries remaining)
|
||||
movl 8(%esp), %ecx
|
||||
cmpl 12(%esp), %ecx
|
||||
jae .find_root_partition_got_entry_count
|
||||
movl 12(%esp), %ecx
|
||||
|
||||
.find_root_partition_got_entry_count:
|
||||
# update entries remaining
|
||||
subl %ecx, 12(%esp)
|
||||
|
||||
# si: entry pointer
|
||||
movw $sector_buffer, %si
|
||||
|
||||
.find_root_partition_loop_entries:
|
||||
# temporarily save cx in dx
|
||||
movw %cx, %dx
|
||||
|
||||
# check that entry is used
|
||||
movw $16, %cx
|
||||
movw $zero_guid, %di
|
||||
call memcmp
|
||||
test %al, %al
|
||||
jnz .find_root_partition_next_entry
|
||||
|
||||
# compare entry guid to root guid
|
||||
movw $16, %cx
|
||||
addw $16, %si
|
||||
movw $root_partition_guid, %di
|
||||
call memcmp
|
||||
subw $16, %si
|
||||
|
||||
testb %al, %al
|
||||
jnz .find_root_partition_found
|
||||
|
||||
.find_root_partition_next_entry:
|
||||
|
||||
# restore cx
|
||||
movw %dx, %cx
|
||||
|
||||
# entry pointer += entry size
|
||||
addw (gpt_header + 84), %si
|
||||
loop .find_root_partition_loop_entries
|
||||
|
||||
# entry not found in this sector
|
||||
|
||||
# increment 8 byte entry array lba
|
||||
incl 0(%esp)
|
||||
jno .find_root_partition_no_overflow
|
||||
incl 4(%esp)
|
||||
|
||||
.find_root_partition_no_overflow:
|
||||
# loop to read next section if entries remaining
|
||||
cmpl $0, 12(%esp)
|
||||
jnz .find_root_partition_read_entry_section
|
||||
|
||||
.find_root_partition_not_found:
|
||||
movw $root_partition_not_found_msg, %si
|
||||
jmp print_and_halt
|
||||
|
||||
.find_root_partition_found:
|
||||
# copy entry to buffer
|
||||
movw $root_partition_entry, %di
|
||||
movw $128, %cx
|
||||
rep movsb
|
||||
|
||||
movw $root_partition_found_msg, %si
|
||||
call puts; call print_newline
|
||||
|
||||
leavel
|
||||
ret
|
||||
|
||||
|
||||
# print information about root partition
|
||||
.global print_root_partition_info
|
||||
print_root_partition_info:
|
||||
pushw %ax
|
||||
pushw %bx
|
||||
pushw %cx
|
||||
pushw %si
|
||||
|
||||
movw $root_partition_info_start_msg, %si
|
||||
call puts;
|
||||
|
||||
movw $16, %bx
|
||||
movw $2, %cx
|
||||
movw (root_partition_entry + 38), %ax; call print_number
|
||||
movw (root_partition_entry + 36), %ax; call print_number
|
||||
movw (root_partition_entry + 34), %ax; call print_number
|
||||
movw (root_partition_entry + 32), %ax; call print_number
|
||||
|
||||
movb $'-', %al; call putc
|
||||
movb $'>', %al; call putc
|
||||
|
||||
movw (root_partition_entry + 46), %ax; call print_number
|
||||
movw (root_partition_entry + 44), %ax; call print_number
|
||||
movw (root_partition_entry + 42), %ax; call print_number
|
||||
movw (root_partition_entry + 40), %ax; call print_number
|
||||
|
||||
call print_newline
|
||||
|
||||
popw %si
|
||||
popw %cx
|
||||
popw %bx
|
||||
popw %ax
|
||||
ret
|
||||
|
||||
|
||||
# These will be patched during bootloader installation
|
||||
root_disk_guid:
|
||||
.ascii "root disk guid "
|
||||
root_partition_guid:
|
||||
.ascii "root part guid "
|
||||
zero_guid:
|
||||
.skip 16, 0
|
||||
|
||||
root_disk_found_msg:
|
||||
.asciz "Root disk found!"
|
||||
root_disk_not_found_msg:
|
||||
.asciz "Root disk not found"
|
||||
|
||||
root_partition_found_msg:
|
||||
.asciz "Root partition found!"
|
||||
root_partition_not_found_msg:
|
||||
.asciz "Root partition not found"
|
||||
|
||||
root_partition_info_start_msg:
|
||||
.asciz "Root partition: "
|
||||
|
||||
.section .bss
|
||||
|
||||
.align SECTOR_SIZE
|
||||
gpt_header:
|
||||
.skip SECTOR_SIZE
|
||||
gpt_entry_data:
|
||||
.skip SECTOR_SIZE
|
||||
sector_buffer:
|
||||
.skip SECTOR_SIZE
|
||||
|
||||
disk_address_packet:
|
||||
.skip 16
|
||||
|
||||
disk_drive_parameters:
|
||||
.skip 0x1A
|
||||
.skip 2 # padding
|
||||
|
||||
root_disk_drive_number:
|
||||
.skip 1
|
||||
.skip 3 # padding
|
||||
|
||||
root_partition_entry:
|
||||
.skip 128
|
||||
|
|
@ -30,10 +30,14 @@ make
|
|||
mkdir -p $BUILD_DIR
|
||||
|
||||
echo compiling bootloader
|
||||
x86_64-banan_os-as $CURRENT_DIR/boot.S -o $BUILD_DIR/bootloader.o
|
||||
x86_64-banan_os-as $CURRENT_DIR/boot.S -o $BUILD_DIR/boot.o
|
||||
x86_64-banan_os-as $CURRENT_DIR/command_line.S -o $BUILD_DIR/command_line.o
|
||||
x86_64-banan_os-as $CURRENT_DIR/disk.S -o $BUILD_DIR/disk.o
|
||||
x86_64-banan_os-as $CURRENT_DIR/memory_map.S -o $BUILD_DIR/memory_map.o
|
||||
x86_64-banan_os-as $CURRENT_DIR/utils.S -o $BUILD_DIR/utils.o
|
||||
|
||||
echo linking bootloader
|
||||
x86_64-banan_os-ld -nostdlib -T $CURRENT_DIR/linker.ld $BUILD_DIR/bootloader.o -o $BUILD_DIR/bootloader
|
||||
x86_64-banan_os-ld -nostdlib -T $CURRENT_DIR/linker.ld $BUILD_DIR/boot.o $BUILD_DIR/command_line.o $BUILD_DIR/disk.o $BUILD_DIR/memory_map.o $BUILD_DIR/utils.o -o $BUILD_DIR/bootloader
|
||||
|
||||
echo installing bootloader to
|
||||
$INSTALLER_BUILD_DIR/x86_64-banan_os-bootloader-installer $BUILD_DIR/bootloader $BANAN_DISK_IMAGE_PATH $ROOT_PARTITION_GUID
|
||||
|
|
|
|||
|
|
@ -1,10 +1,14 @@
|
|||
ENTRY(stage1_main)
|
||||
|
||||
SECTIONS
|
||||
{
|
||||
. = 0x7C00;
|
||||
.stage1 : { *(.stage1) }
|
||||
|
||||
. = ALIGN(512);
|
||||
stage2_start = .;
|
||||
.stage2 : { *(.stage2) }
|
||||
stage2_end = .;
|
||||
|
||||
. = ALIGN(512);
|
||||
.bss : { *(.bss) }
|
||||
|
|
|
|||
|
|
@ -0,0 +1,129 @@
|
|||
.code16
|
||||
|
||||
.section .stage2
|
||||
|
||||
# fills memory map data structure
|
||||
# doesn't return on error
|
||||
# NO REGISTERS SAVED
|
||||
.global get_memory_map
|
||||
get_memory_map:
|
||||
movl $0, (memory_map_entry_count)
|
||||
|
||||
movl $0x0000E820, %eax
|
||||
movl $0x534D4150, %edx
|
||||
xorl %ebx, %ebx
|
||||
movl $20, %ecx
|
||||
movw $memory_map_entries, %di
|
||||
|
||||
clc
|
||||
int $0x15
|
||||
# If first call returs with CF set, the call failed
|
||||
jc .get_memory_map_error
|
||||
|
||||
.get_memory_map_rest:
|
||||
cmpl $0x534D4150, %eax
|
||||
jne .get_memory_map_error
|
||||
|
||||
# FIXME: don't assume BIOS to always return 20 bytes
|
||||
cmpl $20, %ecx
|
||||
jne .get_memory_map_error
|
||||
|
||||
# increment entry count
|
||||
incl (memory_map_entry_count)
|
||||
|
||||
# increment entry pointer
|
||||
addw %cx, %di
|
||||
|
||||
# BIOS can indicate end of list by 0 in ebx
|
||||
testl %ebx, %ebx
|
||||
jz .get_memory_map_done
|
||||
|
||||
movl $0x0000E820, %eax
|
||||
movl $0x534D4150, %edx
|
||||
|
||||
clc
|
||||
int $0x15
|
||||
# BIOS can indicate end of list by setting CF
|
||||
jnc .get_memory_map_rest
|
||||
|
||||
.get_memory_map_done:
|
||||
ret
|
||||
|
||||
.get_memory_map_error:
|
||||
movw $memory_map_error_msg, %si
|
||||
jmp print_and_halt
|
||||
|
||||
|
||||
# print memory map from memory_map_entries
|
||||
# NO REGISTERS SAVED
|
||||
.global print_memory_map
|
||||
print_memory_map:
|
||||
movw $memory_map_msg, %si
|
||||
call puts
|
||||
call print_newline
|
||||
|
||||
movl (memory_map_entry_count), %edx
|
||||
movw $memory_map_entries, %si
|
||||
|
||||
movw $16, %bx
|
||||
movw $4, %cx
|
||||
|
||||
.loop_memory_map:
|
||||
movb $' ', %al
|
||||
call putc; call putc; call putc; call putc
|
||||
|
||||
movw 0x06(%si), %ax
|
||||
call print_number
|
||||
movw 0x04(%si), %ax
|
||||
call print_number
|
||||
movw 0x02(%si), %ax
|
||||
call print_number
|
||||
movw 0x00(%si), %ax
|
||||
call print_number
|
||||
|
||||
movb $',', %al
|
||||
call putc
|
||||
movb $' ', %al
|
||||
call putc
|
||||
|
||||
movw 0x0E(%si), %ax
|
||||
call print_number
|
||||
movw 0x0C(%si), %ax
|
||||
call print_number
|
||||
movw 0x0A(%si), %ax
|
||||
call print_number
|
||||
movw 0x08(%si), %ax
|
||||
call print_number
|
||||
|
||||
movb $',', %al
|
||||
call putc
|
||||
movb $' ', %al
|
||||
call putc
|
||||
|
||||
movw 0x12(%si), %ax
|
||||
call print_number
|
||||
movw 0x10(%si), %ax
|
||||
call print_number
|
||||
|
||||
call print_newline
|
||||
|
||||
addw $20, %si
|
||||
|
||||
decl %edx
|
||||
jnz .loop_memory_map
|
||||
|
||||
ret
|
||||
|
||||
|
||||
memory_map_msg:
|
||||
.asciz "memmap:"
|
||||
memory_map_error_msg:
|
||||
.asciz "Failed to get memory map"
|
||||
|
||||
.section .bss
|
||||
|
||||
memory_map_entry_count:
|
||||
.skip 4
|
||||
# 100 entries should be enough...
|
||||
memory_map_entries:
|
||||
.skip 20 * 100
|
||||
|
|
@ -0,0 +1,218 @@
|
|||
.set SCREEN_WIDTH, 80
|
||||
.set SCREEN_HEIGHT, 25
|
||||
|
||||
.code16
|
||||
|
||||
.section .stage1
|
||||
|
||||
# prints character to screen
|
||||
# al: ascii character to print
|
||||
.global putc
|
||||
putc:
|
||||
pushw %ax
|
||||
pushw %bx
|
||||
movb $0x0E, %ah
|
||||
xorb %bh, %bh
|
||||
int $0x10
|
||||
popw %bx
|
||||
popw %ax
|
||||
ret
|
||||
|
||||
# prints null terminated string to screen
|
||||
# ds:si: string address
|
||||
.global puts
|
||||
puts:
|
||||
pushw %si
|
||||
pushw %bx
|
||||
pushw %ax
|
||||
|
||||
movb $0x0E, %ah
|
||||
xorb %bh, %bh
|
||||
|
||||
.puts_loop:
|
||||
lodsb
|
||||
|
||||
test %al, %al
|
||||
jz .puts_done
|
||||
|
||||
int $0x10
|
||||
jmp .puts_loop
|
||||
|
||||
.puts_done:
|
||||
popw %ax
|
||||
popw %bx
|
||||
popw %si
|
||||
ret
|
||||
|
||||
# compares memory between addresses
|
||||
# si: ptr1
|
||||
# di: ptr2
|
||||
# cx: bytes count
|
||||
# return:
|
||||
# al: 1 if equal, 0 otherwise
|
||||
.global memcmp
|
||||
memcmp:
|
||||
# NOTE: using pusha + popa to save space
|
||||
pusha
|
||||
cld
|
||||
repe cmpsb
|
||||
popa
|
||||
setzb %al
|
||||
ret
|
||||
|
||||
|
||||
.section .stage2
|
||||
|
||||
# read a character from keyboard
|
||||
# return:
|
||||
# al: ascii
|
||||
# ah: bios scan code
|
||||
.global getc
|
||||
getc:
|
||||
movb $0x00, %ah
|
||||
int $0x16
|
||||
ret
|
||||
|
||||
# prints newline to screen
|
||||
.global print_newline
|
||||
print_newline:
|
||||
pushw %ax
|
||||
movb $'\r', %al
|
||||
call putc
|
||||
movb $'\n', %al
|
||||
call putc
|
||||
pop %ax
|
||||
ret
|
||||
|
||||
# prints backspace to screen, can go back a line
|
||||
.global print_backspace
|
||||
print_backspace:
|
||||
pushw %ax
|
||||
pushw %bx
|
||||
pushw %cx
|
||||
pushw %dx
|
||||
|
||||
# get cursor position
|
||||
movb $0x03, %ah
|
||||
movb $0x00, %bh
|
||||
int $0x10
|
||||
|
||||
# don't do anyting if on first row
|
||||
testb %dh, %dh
|
||||
jz .print_backspace_done
|
||||
|
||||
# go one line up if on first column
|
||||
test %dl, %dl
|
||||
jz .print_backspace_go_line_up
|
||||
|
||||
# otherwise decrease column
|
||||
decb %dl
|
||||
jmp .print_backspace_do_print
|
||||
|
||||
.print_backspace_go_line_up:
|
||||
# decrease row and set column to the last one
|
||||
decb %dh
|
||||
movb $(SCREEN_WIDTH - 1), %dl
|
||||
|
||||
.print_backspace_do_print:
|
||||
# set cursor position
|
||||
movb $0x02, %ah
|
||||
int $0x10
|
||||
|
||||
# print 'empty' character (space)
|
||||
mov $' ', %al
|
||||
call putc
|
||||
|
||||
# set cursor position
|
||||
movb $0x02, %ah
|
||||
int $0x10
|
||||
|
||||
.print_backspace_done:
|
||||
popw %dx
|
||||
popw %cx
|
||||
popw %bx
|
||||
popw %ax
|
||||
ret
|
||||
|
||||
# print number to screen
|
||||
# ax: number to print
|
||||
# bx: number base
|
||||
# cx: min width (zero pads if shorter)
|
||||
.global print_number
|
||||
print_number:
|
||||
pusha
|
||||
pushl %ebp
|
||||
movl %esp, %ebp
|
||||
|
||||
# save min width
|
||||
subl $4, %esp
|
||||
movw %cx, (%esp)
|
||||
|
||||
movw $print_number_buffer, %si
|
||||
xorw %cx, %cx
|
||||
|
||||
.print_number_fill_loop:
|
||||
# fill buffer with all remainders ax % bx
|
||||
xorw %dx, %dx
|
||||
divw %bx
|
||||
movb %dl, (%si)
|
||||
incw %si
|
||||
incw %cx
|
||||
testw %ax, %ax
|
||||
jnz .print_number_fill_loop
|
||||
|
||||
# check if zero pad is required
|
||||
cmpw (%esp), %cx
|
||||
jae .print_number_print_loop
|
||||
|
||||
# dx: saved number count
|
||||
# cx: zero pad count
|
||||
movw %cx, %dx
|
||||
movw (%esp), %cx
|
||||
subw %dx, %cx
|
||||
movb $'0', %al
|
||||
|
||||
.print_number_pad_zeroes:
|
||||
call putc
|
||||
loop .print_number_pad_zeroes
|
||||
|
||||
# restore number count
|
||||
movw %dx, %cx
|
||||
|
||||
.print_number_print_loop:
|
||||
decw %si
|
||||
movb (%si), %al
|
||||
cmpb $10, %al
|
||||
jae .print_number_hex
|
||||
addb $'0', %al
|
||||
jmp .print_number_do_print
|
||||
.print_number_hex:
|
||||
addb $('a' - 10), %al
|
||||
.print_number_do_print:
|
||||
call putc
|
||||
loop .print_number_print_loop
|
||||
|
||||
leavel
|
||||
popa
|
||||
ret
|
||||
|
||||
# test if character is printable ascii
|
||||
# al: character to test
|
||||
# return:
|
||||
# al: 1 if is printable, 0 otherwise
|
||||
.global isprint
|
||||
isprint:
|
||||
subb $0x20, %al
|
||||
cmpb $(0x7E - 0x20), %al
|
||||
ja .isprint_not_printable
|
||||
movb $1, %al
|
||||
ret
|
||||
.isprint_not_printable:
|
||||
movb $0, %al
|
||||
ret
|
||||
|
||||
.section .bss
|
||||
|
||||
# enough for base 2 printing
|
||||
print_number_buffer:
|
||||
.skip 16
|
||||
Loading…
Reference in New Issue