Bootloader: implement reading from inode

This commit is contained in:
Bananymous 2023-11-16 20:35:12 +02:00
parent 6f9b3ab5de
commit 8b4f169d0f
1 changed files with 93 additions and 4 deletions

View File

@ -232,8 +232,8 @@ ext2_read_inode:
addl $ext2_block_buffer, %esi
# edi := ext2_inode_buffer
movl $ext2_inode_buffer, %edi
# cx := inode_size
movw (ext2_inode_size), %cx
# ecx := inode_size
movl (ext2_inode_size), %ecx
rep movsb
popal
@ -366,6 +366,87 @@ ext2_data_block_index:
ret
# read bytes from inode (implements read callback)
# eax: first byte
# ecx: byte count
# edi: buffer
# returns only on success
.global ext2_inode_read_bytes
ext2_inode_read_bytes:
pushal
pushl %ebp
movl %esp, %ebp
subl $8, %esp
# save read info
movl %eax, 0(%esp)
movl %ecx, 4(%esp)
# check if eax % EXT2_BLOCK_SIZE != 0,
# then we need to read a partial block starting from an offset
xorl %edx, %edx
movl $EXT2_BLOCK_SIZE, %ebx
divl %ebx
testl %edx, %edx
jz .ext2_inode_read_bytes_no_partial_start
# get data block index and read block
call ext2_data_block_index
call ext2_read_block
# ecx := byte count (min(block_size - edx, remaining_bytes))
movl $EXT2_BLOCK_SIZE, %ecx
subl %edx, %ecx
cmpl %ecx, 4(%esp)
cmovbl 4(%esp), %ecx
# update remaining read info
addl %ecx, 0(%esp)
subl %ecx, 4(%esp)
# esi := start sector data (block_buffer + index * SECTOR_SIZE)
movl $ext2_block_buffer, %esi
addl %edx, %esi
# copy partial block to destination buffer
rep movsb # not sure if this uses (si or esi) and (di or edi)
# check if all sectors are read
cmpl $0, 4(%esp)
je .ext2_inode_read_bytes_done
.ext2_inode_read_bytes_no_partial_start:
# eax := data block index (byte_start / block_size)
movl 0(%esp), %eax
shrl $(EXT2_BLOCK_SHIFT), %eax
# get data block index and read block
call ext2_data_block_index
call ext2_read_block
# calculate bytes to copy (min(block_size, remaining_bytes))
movl $EXT2_BLOCK_SIZE, %ecx
cmpl %ecx, 4(%esp)
cmovbl 4(%esp), %ecx
# update remaining read info
addl %ecx, 0(%esp)
subl %ecx, 4(%esp)
# copy bytes from block into destination
movl $ext2_block_buffer, %esi
rep movsb # not sure if this uses (si or esi) and (di or edi)
# read next block if more sectors remaining
cmpl $0, 4(%esp)
jnz .ext2_inode_read_bytes_no_partial_start
.ext2_inode_read_bytes_done:
leavel
popal
ret
# find inode in inside directory inode stored in ext2_inode_buffer
# store the found inode in ext2_inode_buffer
# si: name string
@ -473,8 +554,14 @@ ext2_directory_find_inode:
# search for kernel file from filesystem
# returns only on success
.global ext2_find_kernel
ext2_find_kernel:
pushl %eax
pushw %cx
pushw %di
pushw %si
movl $EXT2_ROOT_INO, %eax
call ext2_read_inode
@ -523,8 +610,10 @@ ext2_find_kernel:
movw $ext2_kernel_found_msg, %si
call puts; call print_newline
1: jmp 1b
popw %si
popw %di
popw %cx
popl %eax
ret
.ext2_find_kernel_part_not_dir: