find_ps3_ufs2_byte_locations

#!/bin/bash

test "$#" -eq 1 || { cat << __EOF__

  usage:  find_ps3_ufs2_byte_locations GameOS_superblock.img

    The PS3 defaults to setting the UFS2 formatted GameOS partition to 
    have 8% minimum free space and uses the TIME optimization option. This is 
    fine for smaller drives, but this wastes over 100GB on a 1.5TB drive.
    
    The reason they do this is that UFS2 recommends no less than 5% free
    space to reduce fragmentation and increase performance, and TIME
    optimization increases write performance. However, it's possible to
    reduce the minimum free space to allow for more drive usage, which
    should not cause many problems on very large drives. Changing to SPACE
    optimization will also slow down writes, but will lower fragmentation
    which should speed up reads. Since we mainly care about read speed,
    this seems like a resonable tradeoff to get a ton of extra space for games.

    While it's possible to mount a PS3 hard drive and view it's decrypted
    paritions, unfortunately the tunefs.ufs tool doesn't appear to work.
    However, the file command does appear to show the UFS2 filesystem info.

    So instead of using that to change the minimum free space and the 
    optimization type, this script manually scans and tests changes to a 
    parition dump and uses the file command to check for success.

    This would hypothetically work directly on the PS3 drive, but since it
    writes to so many bytes very quickly, and who knows how stable the 
    decryption and mounting software is, it's safer to use a small image
    dump of the head of the partition first, then only write the bytes that
    are needed.

__EOF__
exit
}

FILE=$1
SIZE=$(stat --printf="%s" $FILE)

MIN_LOCATION=0
OPT_LOCATION=0

MIN_ALREADY_SET=0
OPT_ALREADY_SET=0

# Check if the drive has already been reconfigured
test $(file $FILE | grep "minimum percentage of free blocks 1," | wc -l) -ne 1 || MIN_ALREADY_SET=1
test $(file $FILE | grep "SPACE optimization" | wc -l) -ne 1 || OPT_ALREADY_SET=1

# Hide the cursor to prevent flickering
tput civis

# Trap ctrl-c to reset the cursor if the user cancels the operation
trap ctrl_c INT
function ctrl_c() {
    tput cnorm
    exit
}

# Start at 65536 to save time as this is where the superblock starts and the beginning should all be zeros
i=65536

# Loop through the paritition image, setting one byte at a time and checking with file
while [ $i -lt $SIZE ]; do
    # Skip to the end if the drive is already configured
    if [ $MIN_ALREADY_SET -eq 1 ] && [ $OPT_ALREADY_SET -eq 1 ]; then
        break
    fi

    # Save the current byte
    CURRENT=$(xxd -p -l 1 -s $i $FILE)

    printf "\rChecking byte $i... current contents: $CURRENT                           "
    
    # Try writing 0x01 to this location as this will either set the min free space to 1%
    # or it will change the optimization type from TIME to SPACE
    printf '\x01' | dd of=$FILE bs=1 seek=$i count=1 conv=notrunc status=none
    
    # If needed, check to see if this is the minimum space byte location
    if [ $MIN_LOCATION -eq 0 ] && [ $(file $FILE | grep "minimum percentage of free blocks 1," | wc -l) -eq 1 ]; then
        # Found it!
        #printf "Found minimum space location! $i\n"
        MIN_LOCATION=$i
    fi

    # If not found yet, check to see if this is the optimization type byte location
    if [ $OPT_LOCATION -eq 0 ]; [ $(file $FILE | grep "SPACE optimization" | wc -l) -eq 1 ]; then
        # Found it!
        #printf "Found optimization type location! $i\n"
        OPT_LOCATION=$i
    fi

    # Return the file to it's original state
    printf "\x$CURRENT" | dd of=$FILE bs=1 seek=$i count=1 conv=notrunc status=none
    
    # See if we are all done
    if [ $MIN_LOCATION -ne 0 ] && [ $OPT_LOCATION -ne 0 ]; then
        break
    fi
    
    i=$[$i+1]
done

# Clear the output
printf "\r$(tput el)"

# Print the results
if [ $MIN_ALREADY_SET -eq 1 ]; then
    printf "Minimum free space already configured to 1%%\n"
elif [ $MIN_LOCATION -eq 0 ]; then
    printf "Minimum free space byte location not found\n"
else
    printf "Minimum free space byte location: $MIN_LOCATION\n"
fi

if [ $OPT_ALREADY_SET -eq 1 ]; then
    printf "Optimization type already set to SPACE\n"
elif [ $OPT_LOCATION -eq 0 ]; then 
    printf "Optimization type byte location not found\n"
else
    printf "Optimiation type byte location:   $OPT_LOCATION\n"
fi

# Reset the cursor
tput cnorm