Comment rooter un Sony Xperia :

It is only possible to unlock the bootloader for certain releases. To check if it is possible to unlock the bootloader of your device, follow these steps:

1. In your device, open the dialer and enter ##7378423## to access the service menu.
2. Tap Service info > Configuration > Rooting Status. If Bootloader unlock allowed says Yes, then you can continue with the next step. If it says No, or if the status is missing, your device cannot be unlocked.

Bravo à Sony qui fourni l'info sur son site !