Bootloader: Find root partition from GPT header
This commit is contained in:
parent
d2970b5b8d
commit
048bbf874a
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@ -41,7 +41,7 @@ puts:
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movb $0x0E, %ah
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movb $0x00, %bh
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.puts_loop:
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.puts_loop:
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lodsb
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test %al, %al
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@ -50,7 +50,7 @@ puts:
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int $0x10
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jmp .puts_loop
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.puts_done:
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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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@ -155,7 +155,7 @@ find_gpt_partition_entry:
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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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.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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@ -169,11 +169,11 @@ find_gpt_partition_entry:
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loop .loop_gpt_entries
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.no_gpt_partition_found:
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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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.gpt_partition_found:
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movb $1, %al
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ret
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@ -186,11 +186,13 @@ stage1_main:
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# setup stack
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movw %ax, %ss
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movw $0x7C00, %sp
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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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# 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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@ -241,23 +243,23 @@ halt:
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hlt
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jmp halt
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.no_int13h_ext:
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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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.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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.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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.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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.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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@ -341,12 +343,12 @@ print_backspace:
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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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.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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.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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@ -359,7 +361,7 @@ print_backspace:
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movb $0x02, %ah
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int $0x10
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.print_backspace_done:
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.print_backspace_done:
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popa
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ret
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@ -375,7 +377,7 @@ printnum:
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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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.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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@ -393,21 +395,21 @@ printnum:
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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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.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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.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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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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@ -423,15 +425,39 @@ isprint:
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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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.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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pusha
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movl $0, (memory_map_entry_count)
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movl $0x0000E820, %eax
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@ -445,7 +471,7 @@ get_memory_map:
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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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.get_memory_map_rest:
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cmpl $0x534D4150, %eax
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jne .get_memory_map_error
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@ -471,25 +497,23 @@ get_memory_map:
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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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.get_memory_map_done:
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ret
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.get_memory_map_error:
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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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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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.get_command_line_loop:
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call getc
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cmpb $'\b', %al
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@ -513,7 +537,7 @@ get_command_line:
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jmp .get_command_line_loop
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.get_command_line_backspace:
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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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@ -526,42 +550,18 @@ get_command_line:
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jmp .get_command_line_loop
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.get_command_line_done:
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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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int $0x10
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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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# 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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@ -572,7 +572,7 @@ stage2_main:
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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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.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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@ -619,10 +619,212 @@ stage2_main:
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decl %edx
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jnz .loop_memory_map
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ret
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# find root disk and populate root_disk_drive_number field
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# NO REGISTERS SAVED
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find_root_disk:
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movb $0x80, %dl
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.find_root_disk_loop:
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call drive_exists
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testb %al, %al
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jz .find_root_disk_not_found
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# read GPT header
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xorw %bx, %bx
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movl $1, %eax
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movw $1, %cx
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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 + 0)
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jne .find_root_disk_next_disk
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cmpl $0x54524150, (gpt_header + 4)
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jne .find_root_disk_next_disk
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# compare disk GUID
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movw $root_disk_guid, %si
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movw $(gpt_header + 56), %di
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movw $16, %cx
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call memcmp
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testb %al, %al
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jz .find_root_disk_next_disk
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movb %dl, (root_disk_drive_number)
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ret
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.find_root_disk_next_disk:
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incb %dl
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jmp .find_root_disk_loop
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.find_root_disk_not_found:
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movw $no_root_disk_msg, %si
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jmp print_and_halt
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# finds root partition from root disk
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# fills root_partition_entry data structure
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# NOTE: assumes GPT header is in `gpt_header`
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# NO REGISTERS SAVED
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find_root_partition:
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pushl %ebp
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movl %esp, %ebp
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subl $16, %esp
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# esp + 0: 8 byte entry array lba
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movl (gpt_header + 72), %eax
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movl %eax, 0(%esp)
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movl (gpt_header + 76), %eax
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movl %eax, 4(%esp)
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# FIXME: check that bits 48-63 are zero
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# esp + 8: 4 byte entries per sector
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xorl %edx, %edx
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movl $SECTOR_SIZE, %eax
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divl (gpt_header + 84)
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movl %eax, 8(%esp)
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# esp + 12: 4 byte entries remaining
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movl (gpt_header + 80), %eax
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testl %eax, %eax
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jz .find_root_partition_not_found
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movl %eax, 12(%esp)
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.find_root_partition_read_entry_section:
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movl 0(%esp), %eax
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movl 4(%esp), %ebx
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movw $1, %cx
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movb (root_disk_drive_number), %dl
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movw $sector_buffer, %di
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call read_from_disk
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# ecx: min(entries per section, entries remaining)
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movl 8(%esp), %ecx
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cmpl 12(%esp), %ecx
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jae .find_root_partition_got_entry_count
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movl 12(%esp), %ecx
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.find_root_partition_got_entry_count:
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# update entries remaining
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subl %ecx, 12(%esp)
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# si: entry pointer
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movw $sector_buffer, %si
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.find_root_partition_loop_entries:
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# temporarily save cx in dx
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movw %cx, %dx
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# check that entry is used
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movw $16, %cx
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movw $zero_guid, %di
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call memcmp
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test %al, %al
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jnz .find_root_partition_next_entry
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# compare entry guid to root guid
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movw $16, %cx
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addw $16, %si
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movw $root_partition_guid, %di
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call memcmp
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subw $16, %si
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testb %al, %al
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jnz .find_root_partition_found
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.find_root_partition_next_entry:
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# restore cx
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movw %dx, %cx
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# entry pointer += entry size
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addw (gpt_header + 84), %si
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loop .find_root_partition_loop_entries
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# entry not found in this sector
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# increment 8 byte entry array lba
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incl 0(%esp)
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jno .find_root_partition_no_overflow
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incl 4(%esp)
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.find_root_partition_no_overflow:
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# loop to read next section if entries remaining
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cmpl $0, 12(%esp)
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jnz .find_root_partition_read_entry_section
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.find_root_partition_not_found:
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movw $no_root_partition_msg, %si
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jmp print_and_halt
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.find_root_partition_found:
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# copy entry to buffer
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movw $root_partition_entry, %di
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movw $128, %cx
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rep movsb
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leavel
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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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int $0x10
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# print hello message
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movw $hello_msg, %si
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call puts; 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; call print_newline
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call print_memory_map
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call find_root_disk
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movw $root_disk_found_msg, %si
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call puts; call print_newline
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call find_root_partition
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movw $root_partition_found_msg, %si
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call puts; call print_newline
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movw $16, %bx
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movw $2, %cx
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movw (root_partition_entry + 38), %ax; call printnum
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movw (root_partition_entry + 36), %ax; call printnum
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movw (root_partition_entry + 34), %ax; call printnum
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movw (root_partition_entry + 32), %ax; call printnum
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movb $'-', %al; call putc
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movb $'>', %al; call putc
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movw (root_partition_entry + 46), %ax; call printnum
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movw (root_partition_entry + 44), %ax; call printnum
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movw (root_partition_entry + 42), %ax; call printnum
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movw (root_partition_entry + 40), %ax; call printnum
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jmp halt
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# These will be patched during bootloader installation
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root_disk_guid:
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.ascii "root disk guid "
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root_partition_guid:
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.ascii "root part guid "
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zero_guid:
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.quad 0
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.quad 0
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hello_msg:
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.asciz "This is banan-os bootloader"
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@ -639,6 +841,16 @@ memory_map_error_msg:
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start_kernel_load_msg:
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.asciz "Starting to load kernel"
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root_disk_found_msg:
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.asciz "Root disk found!"
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no_root_disk_msg:
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.asciz "Root disk not found"
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root_partition_found_msg:
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.asciz "Root partition found!"
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no_root_partition_msg:
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.asciz "Root partition not found"
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stage2_end:
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@ -650,12 +862,24 @@ gpt_header:
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gpt_entry_data:
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.skip SECTOR_SIZE
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sector_buffer:
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.skip SECTOR_SIZE
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disk_drive_parameters:
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.skip 0x1A
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disk_address_packet:
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.skip 16
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printnum_buffer:
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.skip 10
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root_disk_drive_number:
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.skip 1
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|
||||
root_partition_entry:
|
||||
.skip 128
|
||||
|
||||
memory_map_entry_count:
|
||||
.skip 4
|
||||
# 100 entries should be enough...
|
||||
|
|
|
|||
Loading…
Reference in New Issue