forked from Bananymous/banan-os
Bootloader: Find root partition from GPT header
This commit is contained in:
parent
d2970b5b8d
commit
048bbf874a
|
|
@ -186,11 +186,13 @@ stage1_main:
|
|||
|
||||
# setup stack
|
||||
movw %ax, %ss
|
||||
movw $0x7C00, %sp
|
||||
movl $0x7C00, %esp
|
||||
|
||||
# save boot disk number
|
||||
movb %dl, (boot_disk_number)
|
||||
|
||||
# FIXME: validate boot disk (needs size optizations)
|
||||
|
||||
# confirm that int 13h extensions are available
|
||||
clc
|
||||
movb $0x41, %ah
|
||||
|
|
@ -427,11 +429,35 @@ isprint:
|
|||
ret
|
||||
|
||||
|
||||
# fills memory map data structure
|
||||
# doesn't return on error
|
||||
get_memory_map:
|
||||
# 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
|
||||
|
||||
clc
|
||||
int $0x13
|
||||
jc .drive_exists_nope
|
||||
|
||||
popa
|
||||
movb $1, %al
|
||||
ret
|
||||
|
||||
.drive_exists_nope:
|
||||
popa
|
||||
movb $0, %al
|
||||
ret
|
||||
|
||||
|
||||
# fills memory map data structure
|
||||
# doesn't return on error
|
||||
# NO REGISTERS SAVED
|
||||
get_memory_map:
|
||||
movl $0, (memory_map_entry_count)
|
||||
|
||||
movl $0x0000E820, %eax
|
||||
|
|
@ -472,7 +498,6 @@ get_memory_map:
|
|||
jnc .get_memory_map_rest
|
||||
|
||||
.get_memory_map_done:
|
||||
popa
|
||||
ret
|
||||
|
||||
.get_memory_map_error:
|
||||
|
|
@ -481,9 +506,8 @@ get_memory_map:
|
|||
|
||||
|
||||
# fills command line buffer
|
||||
# NO REGISTERS SAVED
|
||||
get_command_line:
|
||||
pusha
|
||||
|
||||
movw $command_line_enter_msg, %si
|
||||
call puts
|
||||
|
||||
|
|
@ -532,36 +556,12 @@ get_command_line:
|
|||
|
||||
call print_newline
|
||||
|
||||
popa
|
||||
ret
|
||||
|
||||
|
||||
stage2_main:
|
||||
# clear screen and enter 80x25 text mode
|
||||
movb $0x03, %al
|
||||
movb $0x00, %ah
|
||||
int $0x10
|
||||
|
||||
# print hello message
|
||||
movw $hello_msg, %si
|
||||
call puts
|
||||
call print_newline
|
||||
|
||||
call get_memory_map
|
||||
call get_command_line
|
||||
|
||||
call print_newline
|
||||
|
||||
movw $start_kernel_load_msg, %si
|
||||
call puts
|
||||
call print_newline
|
||||
|
||||
movw $command_line_msg, %si
|
||||
call puts
|
||||
movw $command_line_buffer, %si
|
||||
call puts
|
||||
call print_newline
|
||||
|
||||
# print memory map from memory_map_entries
|
||||
# NO REGISTERS SAVED
|
||||
print_memory_map:
|
||||
movw $memory_map_msg, %si
|
||||
call puts
|
||||
call print_newline
|
||||
|
|
@ -619,10 +619,212 @@ stage2_main:
|
|||
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
|
||||
movb $0x00, %ah
|
||||
int $0x10
|
||||
|
||||
# print hello message
|
||||
movw $hello_msg, %si
|
||||
call puts; call print_newline
|
||||
|
||||
call get_memory_map
|
||||
call get_command_line
|
||||
|
||||
call print_newline
|
||||
|
||||
movw $start_kernel_load_msg, %si
|
||||
call puts; call print_newline
|
||||
|
||||
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
|
||||
|
||||
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"
|
||||
|
||||
|
|
@ -639,6 +841,16 @@ memory_map_error_msg:
|
|||
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:
|
||||
|
||||
|
||||
|
|
@ -650,12 +862,24 @@ gpt_header:
|
|||
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...
|
||||
|
|
|
|||
Loading…
Reference in New Issue