forked from Bananymous/banan-os
Bootloader: add support for indirect inode blocks
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b371abade5
commit
3bcbc7c018
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@ -245,7 +245,10 @@ ext2_read_inode:
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# return:
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# eax: block index
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ext2_data_block_index:
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pushl %ebx
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pushl %ecx
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pushl %edx
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pushl %esi
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# calculate max data blocks
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movl (ext2_inode_buffer + i_size), %ecx
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@ -260,13 +263,87 @@ ext2_data_block_index:
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# check if this is direct block access
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cmpl $12, %eax
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jb .ext2_data_block_index_direct
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subl $12, %eax
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jmp .ext2_data_block_index_unsupported
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# check if this is singly indirect block access
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cmpl $(EXT2_BLOCK_SIZE / 4), %eax
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jb .ext2_data_block_index_singly_indirect
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subl $(EXT2_BLOCK_SIZE / 4), %eax
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# check if this is doubly indirect block access
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cmpl $((EXT2_BLOCK_SIZE / 4) * (EXT2_BLOCK_SIZE / 4)), %eax
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jb .ext2_data_block_index_doubly_indirect
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subl $((EXT2_BLOCK_SIZE / 4) * (EXT2_BLOCK_SIZE / 4)), %eax
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# check if this is triply indirect block access
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cmpl $((EXT2_BLOCK_SIZE / 4) * (EXT2_BLOCK_SIZE / 4) * (EXT2_BLOCK_SIZE / 4)), %eax
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jb .ext2_data_block_index_triply_indirect
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# otherwise this is invalid access
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jmp .ext2_data_block_index_invalid
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.ext2_data_block_index_direct:
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movl $(ext2_inode_buffer + i_block), %ecx
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addl %eax, %ecx
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movl (%ecx), %eax
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movl $(ext2_inode_buffer + i_block), %esi
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movl (%esi, %eax, 4), %eax
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jmp .ext2_data_block_index_done
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.ext2_data_block_index_singly_indirect:
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movl %eax, %ebx
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movl (ext2_inode_buffer + i_block + 12 * 4), %eax
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movw $1, %cx
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jmp .ext2_data_block_index_indirect
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.ext2_data_block_index_doubly_indirect:
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movl %eax, %ebx
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movl (ext2_inode_buffer + i_block + 13 * 4), %eax
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movw $2, %cx
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jmp .ext2_data_block_index_indirect
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.ext2_data_block_index_triply_indirect:
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movl %eax, %ebx
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movl (ext2_inode_buffer + i_block + 14 * 4), %eax
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movw $3, %cx
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jmp .ext2_data_block_index_indirect
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# eax := current block
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# ebx := index
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# cx := depth
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.ext2_data_block_index_indirect:
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call ext2_read_block
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# store depth and index
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pushw %cx
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pushl %ebx
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cmpw $1, %cx
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jbe .ext2_data_block_index_no_shift
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# cl := shift
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movb $(EXT2_BLOCK_SHIFT - 2), %al
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decb %cl
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mulb %cl
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movb %al, %cl
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# ebx := ebx >> cl
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shrl %cl, %ebx
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.ext2_data_block_index_no_shift:
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# edx := index of next block
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movl %ebx, %eax
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xorl %edx, %edx
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movl $(EXT2_BLOCK_SIZE / 4), %ebx
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divl %ebx
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# eax := next block
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movl $ext2_block_buffer, %esi
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movl (%esi, %edx, 4), %eax
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# restore depth and index
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popl %ebx
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popw %cx
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loop .ext2_data_block_index_indirect
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jmp .ext2_data_block_index_done
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.ext2_data_block_index_out_of_bounds:
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@ -275,14 +352,17 @@ ext2_data_block_index:
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movl $0, %eax
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jmp .ext2_data_block_index_done
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.ext2_data_block_index_unsupported:
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movw $ext2_data_block_index_unsupported_msg, %si
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.ext2_data_block_index_invalid:
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movw $ext2_data_block_index_invalid_msg, %si
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call puts; call print_newline
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movl $0, %eax
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jmp .ext2_data_block_index_done
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.ext2_data_block_index_done:
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popl %esi
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popl %edx
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popl %ecx
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popl %ebx
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ret
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@ -490,8 +570,8 @@ ext2_kernel_found_msg:
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ext2_data_block_index_out_of_bounds_msg:
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.asciz "data block index out of bounds"
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ext2_data_block_index_unsupported_msg:
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.asciz "unsupported data block index"
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ext2_data_block_index_invalid_msg:
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.asciz "data block index is invalid"
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ext2_looking_for_msg:
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.asciz "looking for "
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