If you cant wait for Android 4.1.2 update come to your Xperia S smartphone, the easiest way to get this latest update is to root Sony Xperia S. This tutorial will show you which steps you need to perform on your Xperia S device in order to root it. SO let get started!
Xperia S with a lower firmware to 6.1.A.2.55 (up 6.1.A.2.55)
Unlock the bootloader – Unlock the bootloader of your Xperia smartphone
Keep in mind that before proceeding to below steps you will need to backup all data from your Sony Xperia S device because all data from it will be removed.
Root Aony Xperia S
Step 1: Download the V18 file found above.
Step 2: Unpack it in a folder named Root Xperia S for example.
Step 3: Open the Root folder (or whatever name you gave it) file.
Step 4: Put your Sony Xperia S in USB debug mode (Settings > Developer options > USB debugging).
Step 5: Now from your computer, and folder which you created in Step 2, Start RunMe file.
Step 6: When command prompt window opens up, type 1 and press Enter on your keyboard.
Step 7: Connect Xperia S to your PC via USB cable.
Step 8: On your smartphone, press restore.
Step 9: After two minutes, the smartphone restarts.
Step 10: Check for the SuperSu application that was just installed on your Sony Xperia S.