Bootloader: Continue work on bootloader
Bootloader can now get the memory map and read cmdline from user. Now 'just' video mode query, ext2 and ELF parsing are needed :D
This commit is contained in:
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c47f6a78bc
commit
a3a287f5ca
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@ -1,10 +1,9 @@
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# FIXME: don't assume 512 byte sectors
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.set SECTOR_SIZE, 512
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.set GPT_HEADER_ADDR, free_memory_start
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.set GPT_ENTRY_ADDR, free_memory_start + SECTOR_SIZE
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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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@ -20,42 +19,49 @@
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.section .stage1
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stage1_start:
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jmp main
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jmp stage1_main
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# al: character to print
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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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mov $0x0E, %ah
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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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# ds:si: null terminated string to print
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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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push %si
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push %ax
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pushw %si
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pushw %bx
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pushw %ax
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1:
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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 2f
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jz .puts_done
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call putc
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jmp 1b
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int $0x10
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jmp .puts_loop
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2:
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mov $'\r', %al
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call putc
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mov $'\n', %al
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call putc
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pop %ax
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pop %si
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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: count
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# return: 1 if equal, 0 otherwise
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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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@ -70,12 +76,10 @@ memcmp:
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# read sectors from disk
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#
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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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#
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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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@ -103,7 +107,78 @@ read_from_disk:
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ret
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main:
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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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stage1_main:
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# setup segments
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movw $0, %ax
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movw %ax, %ds
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@ -129,61 +204,19 @@ main:
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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_ADDR, %di
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movw $gpt_header, %di
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call read_from_disk
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# confirm header (starts with 'EFI PART')
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cmpl $0x20494645, (GPT_HEADER_ADDR + 0)
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jne .not_gpt_partition
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cmpl $0x54524150, (GPT_HEADER_ADDR + 4)
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jne .not_gpt_partition
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call validate_gpt_header
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# eax := entry_count
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movl (GPT_HEADER_ADDR + 80), %eax
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test %eax, %eax
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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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# edx:eax := eax * entry_size
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mull (GPT_HEADER_ADDR + 84)
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test %edx, %edx
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jnz .too_gpt_big_entries
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# BIOS boot partiton found!
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# sector count := (arr_size + SECTOR_SIZE - 1) / SECTOR_SIZE
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pushl %eax
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addl $(SECTOR_SIZE - 1), %eax
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movl $SECTOR_SIZE, %ecx
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divl %ecx
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movl %eax, %ecx
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popl %eax
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# start lba
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movl (GPT_HEADER_ADDR + 72), %eax
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movw (GPT_HEADER_ADDR + 76), %bx
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movb (boot_disk_number), %dl
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movw $GPT_ENTRY_ADDR, %di
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call read_from_disk
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# NOTE: 'only' 0xFFFF partitions supported
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movw (GPT_HEADER_ADDR + 80), %cx
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.loop_entries:
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push %cx
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movw $16, %cx
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movw $bios_boot_guid, %si
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call memcmp
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pop %cx
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testb %al, %al
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jnz .bios_boot_found
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# add entry size to entry pointer
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addw (GPT_HEADER_ADDR + 84), %di
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loop .loop_entries
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jmp .no_bios_boot_partition
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.bios_boot_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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@ -200,7 +233,7 @@ main:
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movw $stage2_start, %di
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call read_from_disk
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jmp stage2_start
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jmp stage2_main
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print_and_halt:
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call puts
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@ -229,7 +262,6 @@ halt:
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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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@ -245,7 +277,7 @@ 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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.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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@ -256,10 +288,6 @@ too_gpt_big_entries_msg:
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boot_disk_number:
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.skip 1
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disk_address_packet:
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.skip 16
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#########################################
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#
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@ -268,7 +296,247 @@ disk_address_packet:
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#########################################
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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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# fills memory map data structure
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# doesn't return on error
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get_memory_map:
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pusha
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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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popa
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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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get_command_line:
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pusha
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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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popa
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ret
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stage2_main:
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# clear screen and enter 80x25 text mode
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movb $0x03, %al
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movb $0x00, %ah
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@ -277,11 +545,123 @@ stage2_start:
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# print hello message
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movw $hello_msg, %si
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call puts
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call print_newline
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call get_memory_map
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call get_command_line
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call print_newline
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movw $start_kernel_load_msg, %si
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call puts
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call print_newline
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movw $command_line_msg, %si
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call puts
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movw $command_line_buffer, %si
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call puts
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call print_newline
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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
|
||||
call putc
|
||||
call putc
|
||||
|
||||
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
|
||||
|
||||
|
||||
jmp halt
|
||||
|
||||
1:
|
||||
jmp 1b
|
||||
|
||||
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"
|
||||
|
||||
stage2_end:
|
||||
|
||||
|
||||
.section .bss
|
||||
|
||||
.align SECTOR_SIZE
|
||||
gpt_header:
|
||||
.skip SECTOR_SIZE
|
||||
gpt_entry_data:
|
||||
.skip SECTOR_SIZE
|
||||
|
||||
disk_address_packet:
|
||||
.skip 16
|
||||
|
||||
printnum_buffer:
|
||||
.skip 10
|
||||
|
||||
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
|
||||
|
|
|
|||
|
|
@ -1,11 +1,11 @@
|
|||
SECTIONS
|
||||
{
|
||||
. = 0x7C00;
|
||||
.stage1 : { *(.stage1*) }
|
||||
.stage1 : { *(.stage1) }
|
||||
|
||||
. = ALIGN(512);
|
||||
.stage2 : { *(.stage2) }
|
||||
|
||||
. = ALIGN(512);
|
||||
free_memory_start = .;
|
||||
.bss : { *(.bss) }
|
||||
}
|
||||
|
|
@ -42,4 +42,4 @@ if [ "$1" == "debug" ] ; then
|
|||
fi
|
||||
|
||||
echo running qemu
|
||||
qemu-system-x86_64 $QEMU_FLAGS --drive format=raw,file=test.img
|
||||
env BANAN_DISK_IMAGE_PATH=${DISK_IMAGE_PATH} BANAN_ARCH=x86_64 ../script/qemu.sh $QEMU_FLAGS
|
||||
|
|
|
|||
Loading…
Reference in New Issue