[Xperia SP Q&A, Help & Troubleshooting] :
Since I cannot reply to this thread:

http://xdaforums.com/showthread.php?t=2440375

I created this topic.

My problem is that the older kernel wont flash. Check this log:

12/059/2013 21:59:11 - INFO - <- This level is successfully initialized
12/059/2013 21:59:11 - INFO - Flashtool Version 0.9.11.0 built on 2013-06-04 22:50:00
12/059/2013 21:59:15 - INFO - Device connected with USB debugging on
12/059/2013 21:59:16 - INFO - Connected device : Sony Xperia SP
12/059/2013 21:59:16 - INFO - Installed version of busybox : N/A
12/059/2013 21:59:16 - INFO - Android version : 4.1.2 / kernel version : 3.4.0-perf-g1285c6c-01110-g8395f64 / Build number : 12.0.A.2.254
12/016/2013 22:16:10 - INFO - Selected XperiaSP_C530X / 12.0.A.1.257 / KernelOnly
12/016/2013 22:16:10 - INFO - Preparing files for flashing
12/016/2013 22:16:10 - INFO - Please connect your device into flashmode.
12/016/2013 22:16:21 - INFO - Device disconnected
12/016/2013 22:16:58 - INFO - Device connected in flash mode
12/016/2013 22:16:58 - INFO - Opening device for R/W
12/016/2013 22:16:58 - INFO - Reading device information
12/016/2013 22:16:58 - INFO - Phone ready for flashmode operations.
12/016/2013 22:16:59 - INFO - Current device : C5303 - CB512482RP - 1272-4687_R13A - 1269-3538_12.0.A.1.257 - GLOBAL-LTE_12.0.A.2.254
12/016/2013 22:16:59 - INFO - Start Flashing
12/016/2013 22:16:59 - INFO - Processing loader
12/016/2013 22:16:59 - INFO - Checking header
12/016/2013 22:16:59 - INFO - Flashing data
12/017/2013 22:17:03 - INFO - Loader : S1_Root_7054 - Version : R5G006 / Bootloader status : ROOTABLE
12/017/2013 22:17:04 - INFO - Processing kernel.sin
12/017/2013 22:17:04 - INFO - Checking header
12/017/2013 22:17:04 - INFO - Flashing data
12/017/2013 22:17:06 - INFO - Ending flash session
12/017/2013 22:17:06 - INFO - Flashing finished.
12/017/2013 22:17:06 - INFO - Please unplug and start your phone
12/017/2013 22:17:06 - INFO - For flashtool, Unknown Sources and Debugging must be checked in phone settings
12/017/2013 22:17:06 - INFO - Device connected in flash mode
12/017/2013 22:17:24 - INFO - Log written to C:\Flashtool\flashtool_2013-09-12_09-59-11.log
12/018/2013 22:18:01 - INFO - Device disconnected
12/020/2013 22:20:15 - INFO - Device connected with USB debugging on
12/020/2013 22:20:16 - INFO - Connected device : Sony Xperia SP
12/020/2013 22:20:16 - INFO - Installed version of busybox : N/A
12/020/2013 22:20:16 - INFO - Android version : 4.1.2 / kernel version : 3.4.0-perf-g1285c6c-01110-g8395f64 / Build number : 12.0.A.2.254

I continued to using the DooMLoRD_Easy-Rooting-Toolkit_v18_perf-event-exploit.zip and everything looked like it went well but after the phone rebooted it wasn't rooted and the firmware still said 12.0.A.2.254. SuperSU wont start.

The script log:

---------------------------------------------------------------
Easy Rooting toolkit (v18.0)
created by DooMLoRD
"pref_event exploit"
Credits go to all those involved in making this possible!
---------------------------------------------------------------
Special thanks to: the_laser, Bin4ry, fi01, hiikezoe, [NUT]
and to all those who are contributing to our git tree!
Sources: https://github.com/android-rooting-tools
---------------------------------------------------------------
[*] This script will:
(1) root ur device using the pref_event exploit
(2) install Busybox
(3) install SU files
[*] Before u begin:
(1) make sure u have installed adb drivers for ur device
(2) enable "USB DEBUGGING"
from (Menu\Settings\Developer Options)
(3) enable "UNKNOWN SOURCES"
from (Menu\Settings\Security)
(4) connect USB cable to PHONE and then connect to PC
(5) skip "PC Companion Software" prompt on device
---------------------------------------------------------------
CONFIRM ALL THE ABOVE THEN
Press any key to continue . . .
--- STARTING ----
--- WAITING FOR DEVICE
* daemon not running. starting it now *
* daemon started successfully *
--- creating temporary directory
mkdir failed for tmp, File exists
--- cleaning
--- pushing files
81 KB/s (326 bytes in 0.003s)
394 KB/s (1578 bytes in 0.003s)
2188 KB/s (26268 bytes in 0.011s)
3808 KB/s (853044 bytes in 0.218s)
4673 KB/s (112164 bytes in 0.023s)
5250 KB/s (1953159 bytes in 0.363s)
--- DooMing device!
--- Correcting permissions
--- Running exploit

run_root_shell v7.0 (20130731)
Based on pref_event exploit

Modified for auto-rooting by DooMLoRD
Part of Easy Rooting Toolkit

Devices Supported:
Xperia Z (C6602/3) - 10.3.A.0.423
Xperia Z (C6606) - 10.1.1.B.0.166
Xperia Z (C6602/3) - 10.1.1.A.1.253/307
Xperia ZL (C6502/3/6) - 10.3.A.0.423
Tablet Z (SGP321) - 10.1.1.A.1.307
Tablet Z (SGP311/2) - 10.1.C.0.370
Xperia ZR (C5502/3/M36h) - 10.1.1.A.1.310
Xperia SP (C5302/3/6) - 12.0.A.1.211/257/284
Xperia L (C2104/5) - 15.0.A.1.31/36
Xperia T (LT30p) - 9.1.A.1.141/142/145
Xperia TX (LT29i) - 9.1.B.1.67
Xperia V (LT25i) - 9.1.A.1.140/142/145
Xperia S (LT26i) - 6.2.B.0.200/211
Xperia SL (LT26ii) - 6.2.B.0.211
Xperia Acro S (LT26w) - 6.2.B.0.200/211
Xperia Ion (LT28h/i) - 6.2.B.0.211
Xperia P (LT22i) - 6.2.A.1.100
Xperia Go (ST27i/a) - 6.2.A.1.100
Xperia J (ST26i/a) - 11.2.A.0.21/31
Xperia AX (SO-01E) - 10.1.D.0.343
Tablet Z (SO-03E) - 10.1.E.0.265/269
Xperia GX (SO-04D) - 7.0.D.1.137
Xperia A (SO-04E) - 10.1.1.D.0.179
Xperia A (SO-04E) - 10.1.1.D.2.26
Xperia SX (SO-05D) - 7.0.D.1.137
Xperia SX (SO-05D) - 9.1.C.0.475
Xperia VL (SOL21) - 9.0.F.0.226
Xperia VL (SOL21) - 9.1.D.0.395/401
Xperia UL (SOL22) - 10.2.F.3.43

Changelog is posted here: http://bit.ly/ert_log

Device detected: C5303 (12.0.A.1.257)

Attempt perf_swevent exploit...
writing address is 8e49
Launching auto-root script!
---------------------------------------------------------------
Launching final rooting process...
---------------------------------------------------------------
--- Rooting!
--- Remounting rootfs
--- Killing RIC service (specific for new Xperia devices)
Unable to chmod /sbin/ric: No such file or directory
--- Installing busybox
--- Remounting /system
--- copying busybox to /system/xbin/
1666+1 records in
1666+1 records out
853044 bytes transferred in 0.037 secs (23055243 bytes/sec)
--- correcting ownership
--- correcting permissions
--- installing busybox
--- pushing SU binary
rm failed for /system/xbin/su, No such file or directory
219+1 records in
219+1 records out
112164 bytes transferred in 0.005 secs (22432800 bytes/sec)
--- correcting ownership
--- correcting permissions
--- correcting symlinks
rm failed for /system/bin/su, No such file or directory
--- pushing Superuser app
3814+1 records in
3814+1 records out
1953159 bytes transferred in 0.092 secs (21229989 bytes/sec)
--- correcting permissions
--- DONE!
Exiting..
--- cleaning
--- Please wait device is now rebooting
ALL DONE!!!
Press any key to continue . . .

Strange since the script says "Device detected: C5303 (12.0.A.1.257)"

I have a locked bootloader since I read that it shouldn't be a problem

EDIT: Even more strange. Now after the second time doing this my phone seem to be rooted. Will try to flash 2.254