Bootloader: Add support for ext2 blocks up to 4 KiB
This should work with blocks bigger than that, but my linux system only supports up to 4 KiB, so I cannot test this. This allows getting rid of forced block size in mkfs and let the program select appropriately sized blocks.
This commit is contained in:
parent
7356a83a44
commit
ccaa159a73
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@ -2,9 +2,7 @@
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.set SECTOR_SHIFT, 9
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.set SECTOR_SIZE, 1 << SECTOR_SHIFT
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# FIXME: don't assume 1024 byte blocks
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.set EXT2_BLOCK_SHIFT, 10
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.set EXT2_BLOCK_SIZE, 1 << EXT2_BLOCK_SHIFT
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.set EXT2_MAX_BLOCK_SIZE, 4096
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.set EXT2_SUPERBLOCK_SIZE, 264
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.set EXT2_BGD_SHIFT, 5
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.set EXT2_BGD_SIZE, 1 << EXT2_BGD_SHIFT
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@ -18,6 +16,7 @@
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.set EXT2_S_IFREG, 0x8000
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# superblock offsets
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.set s_first_data_block, 20
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.set s_log_block_size, 24
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.set s_inodes_per_group, 40
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.set s_magic, 56
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@ -66,9 +65,7 @@ has_ext2_filesystem:
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# from byte offset 1024
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addl $(1024 / SECTOR_SIZE), %eax
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jnc .has_ext2_filesystem_no_overflow
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incw %bx
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.has_ext2_filesystem_no_overflow:
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adcw $0, %bx
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# into sector buffer
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movw $ext2_block_buffer, %di
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@ -90,11 +87,16 @@ has_ext2_filesystem:
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movl (ext2_superblock_buffer + s_log_block_size), %ecx
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testl $0xFFFFFF00, %ecx
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jnz .has_ext2_filesystem_unsupported_block_size
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# verify 1024 << s_log_block_size == EXT2_BLOCK_SIZE
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# verify 1024 << s_log_block_size <= EXT2_MAX_BLOCK_SIZE
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movl $1024, %eax
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shll %cl, %eax
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cmpl $EXT2_BLOCK_SIZE, %eax
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jne .has_ext2_filesystem_unsupported_block_size
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cmpl $EXT2_MAX_BLOCK_SIZE, %eax
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ja .has_ext2_filesystem_unsupported_block_size
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# fill block size and shift
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movl %eax, (ext2_block_size)
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addl $10, %ecx
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movl %ecx, (ext2_block_shift)
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# fill inode size
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movl $128, %eax
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@ -130,38 +132,23 @@ has_ext2_filesystem:
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# reads block in to ext2_block_buffer
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# eax: block number
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ext2_read_block:
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pushl %eax
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pushl %ebx
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pushw %cx
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pushl %edx
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pushw %di
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pushal
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# NOTE: this assumes 1024 block size
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# eax := (block * block_size) / sector_size := (eax << EXT2_BLOCK_SHIFT) >> SECTOR_SHIFT
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xorl %edx, %edx
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shll $EXT2_BLOCK_SHIFT, %eax
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shrl $SECTOR_SHIFT, %eax
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# ecx := sectors_per_block := block_size / sector_size
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movl (ext2_block_size), %ecx
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shrl $SECTOR_SHIFT, %ecx
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# ebx:eax := eax + (ext2_partition_first_sector)
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movl (ext2_partition_first_sector + 4), %ebx
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# ebx:eax := block * sectors_per_block + (ext2_partition_first_sector)
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xorl %ebx, %ebx
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mull %ecx
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addl (ext2_partition_first_sector + 0), %eax
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jnc .ext2_read_block_no_carry
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incl %ebx
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.ext2_read_block_no_carry:
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# sectors per block
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movw $(EXT2_BLOCK_SIZE / SECTOR_SIZE), %cx
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adcl (ext2_partition_first_sector + 4), %ebx
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movw $ext2_block_buffer, %di
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movb (ext2_drive_number), %dl
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call read_from_disk
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popw %di
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popl %edx
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popw %cx
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popl %ebx
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popl %eax
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popal
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ret
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@ -170,15 +157,23 @@ ext2_read_block:
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ext2_read_block_group_descriptor:
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pushal
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# eax := bgd_byte_offset := 2048 + EXT2_BGD_SIZE * eax := (eax << EXT2_BGD_SHIFT) + 2048
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shll $EXT2_BGD_SHIFT, %eax
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addl $2048, %eax
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# ebx := bgd_block_byte_offset := (s_first_data_block + 1) * block_size
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# := (s_first_data_block + 1) << ext2_block_shift
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movl (ext2_superblock_buffer + s_first_data_block), %ebx
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incl %ebx
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movb (ext2_block_shift), %cl
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shll %cl, %ebx
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# eax: bgd_block := bgd_byte_offset / EXT2_BLOCK_SIZE
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# ebx: bgd_offset := bgd_byte_offset % EXT2_BLOCK_SIZE
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# eax := bgd_byte_offset := bgd_block_byte_offset + EXT2_BGD_SIZE * block_group;
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# := bgd_block_byte_offset + (block_group << EXT2_BGD_SHIFT)
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movb $EXT2_BGD_SHIFT, %cl
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shll %cl, %eax
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addl %ebx, %eax
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# eax: bgd_block := bgd_byte_offset / block_size
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# ebx: bgd_offset := bgd_byte_offset % block_size
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xorl %edx, %edx
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movl $EXT2_BLOCK_SIZE, %ebx
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divl %ebx
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divl (ext2_block_size)
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movl %edx, %ebx
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call ext2_read_block
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@ -204,23 +199,19 @@ ext2_read_inode:
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# ebx := inode_index = (ino - 1) % s_inodes_per_group
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xorl %edx, %edx
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decl %eax
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movl (ext2_superblock_buffer + s_inodes_per_group), %ebx
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divl %ebx
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divl (ext2_superblock_buffer + s_inodes_per_group)
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movl %edx, %ebx
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call ext2_read_block_group_descriptor
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# eax := inode_table_block := (inode_index * inode_size) / EXT2_BLOCK_SIZE
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# ebx := inode_table_offset := (inode_index * inode_size) % EXT2_BLOCK_SIZE
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xorl %edx, %edx
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# eax := inode_table_block := (inode_index * inode_size) / block_size
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# ebx := inode_table_offset := (inode_index * inode_size) % block_size
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movl %ebx, %eax
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movl (ext2_inode_size), %ebx
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mull %ebx
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movl $EXT2_BLOCK_SIZE, %ebx
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divl %ebx
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mull (ext2_inode_size)
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divl (ext2_block_size)
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movl %edx, %ebx
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# eax := file system block := eax + bg_inode_table
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# eax := filesystem_block := eax + bg_inode_table
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addl (ext2_block_group_descriptor_buffer + bg_inode_table), %eax
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movb (ext2_drive_number), %dl
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@ -255,14 +246,17 @@ ext2_data_block_index:
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pushl %esi
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pushl %edi
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# calculate max data blocks
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movl (ext2_inode_buffer + i_size), %ecx
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addl (ext2_inode_size), %ecx
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decl %ecx
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shll $EXT2_BLOCK_SHIFT, %ecx
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# ebx := max_data_blocks := (file_size + block_size - 1) / block_size
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# := (i_size + ext2_block_size - 1) >> ext2_block_shift
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# cl := ext2_block_shift
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movl (ext2_inode_buffer + i_size), %ebx
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addl (ext2_block_size), %ebx
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decl %ebx
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movb (ext2_block_shift), %cl
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shrl %cl, %ebx
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# verify data block is within bounds
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cmpl %ecx, %eax
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cmpl %ebx, %eax
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jae .ext2_data_block_index_out_of_bounds
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# check if this is direct block access
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@ -270,18 +264,26 @@ ext2_data_block_index:
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jb .ext2_data_block_index_direct
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subl $12, %eax
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# cl := indices_per_block_shift := ext2_block_shift - 2
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# ebx := comp
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subb $2, %cl
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movl $1, %ebx
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shll %cl, %ebx
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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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cmpl %ebx, %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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subl %ebx, %eax
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shll %cl, %ebx
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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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cmpl %ebx, %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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subl %ebx, %eax
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shll %cl, %ebx
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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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cmpl %ebx, %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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@ -314,9 +316,12 @@ ext2_data_block_index:
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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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# calculate cache index ((index & 0xFF) | depth)
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movl %ebx, %edx
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andl $(~(EXT2_BLOCK_SIZE / 4 - 1)), %edx
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# edx := cache index := (index & ~(block_size / 4 - 1)) | depth
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# := (index & -(block_size >> 2)) | depth
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movl (ext2_block_size), %edx
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shrl $2, %edx
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negl %edx
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andl %ebx, %edx
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orw %cx, %dx
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# check whether this block is already cached
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@ -343,20 +348,21 @@ ext2_data_block_index:
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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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movb (ext2_block_shift), %al
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subb $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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# ebx := ebx >> shift
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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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# edx := index of next block (ebx & (block_size / 4 - 1))
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movl (ext2_block_size), %edx
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shrl $2, %edx
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decl %edx
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andl %ebx, %edx
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# eax := next block
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movl $ext2_block_buffer, %esi
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@ -371,7 +377,7 @@ ext2_data_block_index:
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# cache last read block
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movw $ext2_block_buffer, %si
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movw $ext2_inode_indirect_buffer, %di
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movw $EXT2_BLOCK_SIZE, %cx
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movw (ext2_block_size), %cx
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rep movsb
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jmp .ext2_data_block_index_done
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@ -390,7 +396,10 @@ ext2_data_block_index:
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.ext2_data_block_index_indirect_cached:
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movl $ext2_inode_indirect_buffer, %esi
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andl $(EXT2_BLOCK_SIZE / 4 - 1), %ebx
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movl (ext2_block_size), %edx
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shrl $2, %edx
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decl %edx
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andl %edx, %ebx
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movl (%esi, %ebx, 4), %eax
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.ext2_data_block_index_done:
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@ -410,6 +419,7 @@ ext2_data_block_index:
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.global ext2_inode_read_bytes
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ext2_inode_read_bytes:
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pushal
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pushl %ebp
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movl %esp, %ebp
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subl $8, %esp
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@ -418,11 +428,11 @@ ext2_inode_read_bytes:
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movl %eax, 0(%esp)
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movl %ecx, 4(%esp)
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# check if eax % EXT2_BLOCK_SIZE != 0,
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# then we need to read a partial block starting from an offset
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# eax := first_byte / block_size
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# edx := first_byte % block_size
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# when edx == 0, no partial read needed
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xorl %edx, %edx
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movl $EXT2_BLOCK_SIZE, %ebx
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divl %ebx
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divl (ext2_block_size)
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testl %edx, %edx
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jz .ext2_inode_read_bytes_no_partial_start
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@ -431,7 +441,7 @@ ext2_inode_read_bytes:
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call ext2_read_block
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# ecx := byte count (min(block_size - edx, remaining_bytes))
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movl $EXT2_BLOCK_SIZE, %ecx
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movl (ext2_block_size), %ecx
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subl %edx, %ecx
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cmpl %ecx, 4(%esp)
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cmovbl 4(%esp), %ecx
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@ -445,7 +455,7 @@ ext2_inode_read_bytes:
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addl %edx, %esi
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# very dumb memcpy with 32 bit addresses
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movl $0, %ebx
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xorl %ebx, %ebx
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.ext2_inode_read_bytes_memcpy_partial:
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movb (%esi, %ebx), %al
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movb %al, (%edi, %ebx)
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@ -461,14 +471,15 @@ ext2_inode_read_bytes:
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.ext2_inode_read_bytes_no_partial_start:
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# eax := data block index (byte_start / block_size)
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movl 0(%esp), %eax
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shrl $(EXT2_BLOCK_SHIFT), %eax
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movb (ext2_block_shift), %cl
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shrl %cl, %eax
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# get data block index and read block
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call ext2_data_block_index
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call ext2_read_block
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# calculate bytes to copy (min(block_size, remaining_bytes))
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movl $EXT2_BLOCK_SIZE, %ecx
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movl (ext2_block_size), %ecx
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cmpl %ecx, 4(%esp)
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cmovbl 4(%esp), %ecx
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@ -524,11 +535,12 @@ ext2_directory_find_inode:
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cmpw $0xFF, %cx
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ja .ext2_directory_find_inode_not_found
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# ebx := max data blocks: ceil(i_size / EXT2_BLOCK_SIZE)
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# ebx := max data blocks: ceil(i_size / block_size)
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movl (ext2_inode_buffer + i_size), %ebx
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addl $EXT2_BLOCK_SHIFT, %ebx
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addl (ext2_block_size), %ebx
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decl %ebx
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shrl $EXT2_BLOCK_SHIFT, %ebx
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movb (ext2_block_shift), %cl
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shrl %cl, %ebx
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jz .ext2_directory_find_inode_not_found
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# 4(%esp) := current block
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@ -575,7 +587,9 @@ ext2_directory_find_inode:
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# go to next entry if this block contains one
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addw 4(%si), %si
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cmpw $(ext2_block_buffer + EXT2_BLOCK_SIZE), %si
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movw $ext2_block_buffer, %di
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addw (ext2_block_size), %di
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cmpw %di, %si
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jb .ext2_directory_find_inode_loop_entries
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.ext2_directory_find_inode_next_block:
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@ -584,7 +598,7 @@ ext2_directory_find_inode:
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jb .ext2_directory_find_inode_block_read_loop
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.ext2_directory_find_inode_not_found:
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movb $0, %al
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xorb %al, %al
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jmp .ext2_directory_find_inode_done
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.ext2_directory_find_inode_found:
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@ -696,7 +710,7 @@ root_partition_does_not_fit_ext2_filesystem_msg:
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root_partition_has_invalid_ext2_magic_msg:
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.asciz "Root partition doesn't contain ext2 magic number"
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root_partition_has_unsupported_ext2_block_size_msg:
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.asciz "Root partition has unsupported ext2 block size (only 1024 supported)"
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.asciz "Root partition has unsupported ext2 block size (1 KiB, 2 KiB and 4 KiB are supported)"
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ext2_part_not_dir_msg:
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.asciz "inode in root path is not directory"
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@ -717,12 +731,12 @@ ext2_looking_for_msg:
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.section .bss
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.align EXT2_BLOCK_SIZE
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.align SECTOR_SIZE
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ext2_block_buffer:
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.skip EXT2_BLOCK_SIZE
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.skip EXT2_MAX_BLOCK_SIZE
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ext2_inode_indirect_buffer:
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.skip EXT2_BLOCK_SIZE
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.skip EXT2_MAX_BLOCK_SIZE
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ext2_inode_indirect_number:
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.skip 4
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@ -736,6 +750,10 @@ ext2_drive_number:
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# NOTE: fits in 2 bytes
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ext2_inode_size:
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.skip 4
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ext2_block_size:
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.skip 4
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ext2_block_shift:
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.skip 4
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ext2_superblock_buffer:
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.skip EXT2_SUPERBLOCK_SIZE
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@ -87,7 +87,7 @@ sudo partprobe $LOOP_DEV
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PARTITION1=${LOOP_DEV}p1
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PARTITION2=${LOOP_DEV}p2
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sudo mkfs.ext2 -q -b 1024 $PARTITION2
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sudo mkfs.ext2 -q $PARTITION2
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sudo mkdir -p $MOUNT_DIR || { echo "Failed to create banan mount dir."; exit 1; }
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||||
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||||
|
|
|
|||
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Reference in New Issue