ROOT your Xperia U Method1(For GB)

ROOT your Xperia U

1. dail *#*#7378423#*#* this will bring you back to the service menu
   
2. Service > Service info > Software info >
   
3. Check your software version, most likely it will be one of the following: 6.0.B.1.564 or 6.0.B.3.184 (if it is another version, update your phone first)
   
4. get the matching kernel from the /kernel/ directory in this zip.
   CREDITS
   The 1.564 kernel is made by DoomLord
   The 3.184 kernel is made by KeiranFTW
5. Copy the matching kernel number from the zip to
   C:\Program Files (x86)\android-sdk\platform-tools
   If you install the wrong version your phone will break
   
6. Go into FastBoot Mode again (blue light thingy)
   if you forgot / run into problems > step 6-12 of Unlock Bootloader guide
   
7. open up the CMD again
   to double check the connection type fastboot.exe -i 0x0fce getvar version
   
8. type or paste cd C:\Program Files (x86)\android-sdk\platform-tools
   
9. type fastboot flash boot 222_kernel.elf
   replace 22222 with your specific kernel