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Bootloader: add support for indirect inode blocks

This commit is contained in:
Bananymous 2023-11-16 13:32:21 +02:00
parent b371abade5
commit 3bcbc7c018
1 changed files with 90 additions and 10 deletions
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100
bootloader/ext2.S
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@ -245,7 +245,10 @@ ext2_read_inode:
# return:
# eax: block index
ext2_data_block_index:
pushl %ebx
pushl %ecx
pushl %edx
pushl %esi
# calculate max data blocks
movl (ext2_inode_buffer + i_size), %ecx
@ -260,13 +263,87 @@ ext2_data_block_index:
# check if this is direct block access
cmpl $12, %eax
jb .ext2_data_block_index_direct
subl $12, %eax
jmp .ext2_data_block_index_unsupported
# check if this is singly indirect block access
cmpl $(EXT2_BLOCK_SIZE / 4), %eax
jb .ext2_data_block_index_singly_indirect
subl $(EXT2_BLOCK_SIZE / 4), %eax
# check if this is doubly indirect block access
cmpl $((EXT2_BLOCK_SIZE / 4) * (EXT2_BLOCK_SIZE / 4)), %eax
jb .ext2_data_block_index_doubly_indirect
subl $((EXT2_BLOCK_SIZE / 4) * (EXT2_BLOCK_SIZE / 4)), %eax
# check if this is triply indirect block access
cmpl $((EXT2_BLOCK_SIZE / 4) * (EXT2_BLOCK_SIZE / 4) * (EXT2_BLOCK_SIZE / 4)), %eax
jb .ext2_data_block_index_triply_indirect
# otherwise this is invalid access
jmp .ext2_data_block_index_invalid
.ext2_data_block_index_direct:
movl $(ext2_inode_buffer + i_block), %ecx
addl %eax, %ecx
movl (%ecx), %eax
movl $(ext2_inode_buffer + i_block), %esi
movl (%esi, %eax, 4), %eax
jmp .ext2_data_block_index_done
.ext2_data_block_index_singly_indirect:
movl %eax, %ebx
movl (ext2_inode_buffer + i_block + 12 * 4), %eax
movw $1, %cx
jmp .ext2_data_block_index_indirect
.ext2_data_block_index_doubly_indirect:
movl %eax, %ebx
movl (ext2_inode_buffer + i_block + 13 * 4), %eax
movw $2, %cx
jmp .ext2_data_block_index_indirect
.ext2_data_block_index_triply_indirect:
movl %eax, %ebx
movl (ext2_inode_buffer + i_block + 14 * 4), %eax
movw $3, %cx
jmp .ext2_data_block_index_indirect
# eax := current block
# ebx := index
# cx := depth
.ext2_data_block_index_indirect:
call ext2_read_block
# store depth and index
pushw %cx
pushl %ebx
cmpw $1, %cx
jbe .ext2_data_block_index_no_shift
# cl := shift
movb $(EXT2_BLOCK_SHIFT - 2), %al
decb %cl
mulb %cl
movb %al, %cl
# ebx := ebx >> cl
shrl %cl, %ebx
.ext2_data_block_index_no_shift:
# edx := index of next block
movl %ebx, %eax
xorl %edx, %edx
movl $(EXT2_BLOCK_SIZE / 4), %ebx
divl %ebx
# eax := next block
movl $ext2_block_buffer, %esi
movl (%esi, %edx, 4), %eax
# restore depth and index
popl %ebx
popw %cx
loop .ext2_data_block_index_indirect
jmp .ext2_data_block_index_done
.ext2_data_block_index_out_of_bounds:
@ -275,14 +352,17 @@ ext2_data_block_index:
movl $0, %eax
jmp .ext2_data_block_index_done
.ext2_data_block_index_unsupported:
movw $ext2_data_block_index_unsupported_msg, %si
.ext2_data_block_index_invalid:
movw $ext2_data_block_index_invalid_msg, %si
call puts; call print_newline
movl $0, %eax
jmp .ext2_data_block_index_done
.ext2_data_block_index_done:
popl %esi
popl %edx
popl %ecx
popl %ebx
ret
@ -332,7 +412,7 @@ ext2_directory_find_inode:
# read current block
call ext2_read_block
# dx := current entry pointer
movw $ext2_block_buffer, %si
@ -422,7 +502,7 @@ ext2_find_kernel:
call puts
popw %si
call puts; call print_newline
# search current directory for this file
call ext2_directory_find_inode
testl %eax, %eax
@ -490,8 +570,8 @@ ext2_kernel_found_msg:
ext2_data_block_index_out_of_bounds_msg:
.asciz "data block index out of bounds"
ext2_data_block_index_unsupported_msg:
.asciz "unsupported data block index"
ext2_data_block_index_invalid_msg:
.asciz "data block index is invalid"
ext2_looking_for_msg:
.asciz "looking for "