Often times, we find certain aspects of flashing ROMs, kernels, and anything that needs to be installed via recovery a bit of a pain. For instance, on older Samsung Galaxy devices (anything before the Galaxy S3), having a custom recovery involves having a kernel lumped alongside because the recovery and boot partition are stored in the same location. This means that updating the kernel will wipe your custom recovery. Now, most owners work around this limitation by flashing what is known as a repack, which is a stock or tweaked kernel that includes a custom recovery image. The likes of HTC and Motorola don’t do this, albeit they do have a few other issues, which we will not talk about right now. Sony Xperia devices are no different from Samsung in that regard, as they also lump boot and recovery in the same area. However, the Sony Xperia T had a little something that was different than other devices with the same “issue.” Upon taking a closer look, XDA Recognized Developers lilstevie, Dees_Troy, and XDA Elite Recognized Developer Rebellos found a small gift from Sony at the very end of the eMMC memory: unused, unpartitioned 300 MB worth of memory. So, ideas started flying around and the devs got to work.
After several weeks of looking into things, and doing some major trial and error, they took that unused space and turned it into a new home for the recovery image. This is completely separate from the kernel (to a certain extent anyways), which means that flashing a new ROM with a new kernel will not replace the custom recovery image. What has been done was to replace a single stage of the entire boot process known as appsboot, which is patched/replaced by LK. It then loads a new stage (mmcblk0p16) that contains the kernel. From that point, the kernel will listen to commands to call upon recovery, which is located on FOTAKernel. The best part is that even after this, there may be enough free space at the end of the chip to do some more creative things such as the ability to store more kernels—perhaps even space for a multi-boot style menu (thanks XDA Recognized Developer cdesai for the explanation). Other added benefits include the ability to use either Sony .elf files or regular Android boot.img, and the ability to go into recovery from the ROM (reboot into recovery).
You will have to make sure that you are running a 4.1.2 official kernel (no CM or other AOSP variants supported as of yet). Also, ICS is not supported either by this release, mainly due to differences in the 3.0 kernel which will cause the device to not boot. Lastly,please understand that this will modify your partition tables. If you are OK with the inherent risks, make sure that you read and understand the installation instructions and take it for a spin.
Since getting the Xperia T the biggest annoyance is only having one bootable partition. To combat this issue I have spent some time porting the Little Kernel bootloader. This allows booting different kernels for recovery and boot as well as a full implementation fastboot.