CptS Lab1

1
CptS Lab1

• Jiong Wang

2
Program logic

• Clear screen and home cursor
• Prompt for a file name to boot, and read in the
  filename (e.g. /boot/mtx)
• Locate the file's inode, hence its disk blocks
• Load the file's blocks to the segment 0x1000
• return 0 if no error, else return 1

3
How to load blocks into memory

• Write a function in C
• getBlock(b_no, buf)
• In your function, do following steps
• Convert a blocks logic address (b_no) to its
  physical address (cyl, head, sector)
• Call function diskr(cyl, head, sector, buf)
• Reminder
• cyl, head, and sector all start from 0
• Make sure ES is correct before calling getBlock()

4
Convert b_no to CHS

• Define CYLSIZE 36
• Define trackSIZE 16
• startSector 2blk
• cyl startSector/CYLSIZE
• head (startSector CYLSIZE) / trackSIZE
• sector (startSector CYLSIZE) trackSIZE

5
How to find /boot/mtx

• Call getBlock(5, buf), the second inode in buf is
  root
• In roots inode, find roots first data block
  (i_block0)
• Call getBlock(i_block0, buf)
• Search for boot directory, return boots inode
  no.
• Find the blk_no of boots inode and the position
  of boots inode in that blk (inode starts from 1)
• Call getBlock(blk_no, buf), locate boots inode
  in the buf
• Repeat the same steps to find MTXs inode

6
Load os to memery

• You obtained MTXs innode in buf1
• Load indirect block into buf2
• Load first double indirect block into buf3
• Set ES to 0x1000
• getBlock(blk, 0)
• inces()
• Repeat until MTX has been loaded into memory
  completely