Originally Posted by shangrila500
I realize that is how to keep your root when updating via OTA to 4.2.2, what I was talking about is if you are on 4.2.2 without root could one of the other Xperia root methods work for that without having to go back to 4.1.2.
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The root method presently used for the Xperia Z (which will also likely be adopted/adapted to other Xperia devices) is presented by DooMLoRD here: http://forum.xda-developers.com/show....php?t=2386405
This is the essentially the approach I took for my SGP311.
Using flashtool you flash an old, rootable kernel from ftf. (This is an ~8 mb file, you are only flashing the kernel, not the entire device)
Use DooMLoRD's Easy-Rooting-Toolkit_v18_perf-event-exploit
Verify that the device is rooted by checking for SuperSU app
Install SuperSU to system, enable OTA protection
Install and set up Voodoo OTA Rootkeeper for good measure (This is when I install busybox)
Flash the latest kernel from an ftf using flashtool (The updated kernel, like its predecessor, is only ~8mb)
Verify version, kernel, and root access
The fact that you're flashing less than 20mb total during the whole procedure saves an incredible amount of time compared to if you were to downgrade to say, 1.0.1.c.370, root, etc and then apply an OTA to get to 1.3.C.0.136 (and 4.2.2).
The issue right now is that so far as I've seen, the necessary kernel only FTF files haven't been prepared. You can open FTFs with 7zip and remove the files that aren't needed but I wasn't able to flash and successfully boot the downgrade to 1.0.1.c.370
I'll try to fiddle with it a bit more, but its nice knowing that a method exists to get root on 4.2.2. The fact that the method involves downgrading the kernel doesn't really matter much considering how effective and widespread the perf event method has been. If anything, it just shows how resourceful DooMLoRD et al. have been.