Written by [NUT]
Viewed: 91928 times
Published: 23 September 2015
Updated: 25 September 2015
Sony has replaced the Android recovery partition with the FOTA kernel, which is meant to aid the device in rolling out OTA updates, which allow kernel updates without the risk of bricking the device. I hear you scream: "But wait, what about the recovery partition announcement by Sony themselves!?", well the answer is simple: that is meant for unlocked bootloader devices ONLY, as a part of their "Open Devices" program.
What is Flashmode, Flashtool and what are these FTF and SIN files I am reading about?
I'm going to quote @Androxyde here (it's a straight copy of his index page), as he is the maintainer of the tool:
This program was originally made to flash sin files downloaded by SEUS/SUS or PC Companion.
Based on a command line tool written by @Bin4ry (Andreas Makris), I brought a user interface to sin files flashing.
We worked together to add more features to the tool such as rooting methods implementation or TA backup / restore.
Then I took the lead and got some advice and help from him occasionally on some features like rom cleaner or bootloader unlocking.
From time to time, sin files have been bundled into what is now well known FTF (Flash Tool Firmwares) and more features have been implemented.
But flashing firmwares is still the core of Flashtool (that is updated at least to follow Sony improvements around sin files) and the reason of its name.
Flashtool can also easily unlock the bootloader of the phone using the BLU icon as far as the bootloader of your phone is unlockable
The flashing feature as well as bootloader unlock feature are available whatever the phone is recognized or not by the application. What is only mandatory for flashing is to own the FTF file according to the device you want to flash it on.
Why should I use Flashtool?
- Once bootloader unlocked, official sony tools do not work anymore.
- Using official sony tools, you can only upgrade. No downgrade possible.
- Using flashtool, you can choose what to flash and what not to flash. This said, many rooting scenarios are available implying kernel only downgrade to retrieve a patched rooting exploit and then flash back the right kernel.
You said unlocking bootloader?
This process gives you the opportunity to flash custom roms such as CyanogenMod ROMs.
I invite you to visit the FXP Project that brings CM and AOSP to xperia devices.
To complete this explanation, Sony devices know 2 bootloader based flash modes:
- Flashmode (This is the S1 flash protocol @Androxyde wrote about)
- Fastboot (This is the original, unmodified fastboot mode from Google)
In the past there was the Sony-Ericsson Update Software/Service (SEUS, later named SUS because Ericsson got removed from the name) which could update your device to the latest software or recover it from an inoperable state. PC Companion was less of a tool for updating and more of making backups, installing applications and managing the device storage. Sometime the past 3-4 years Sony merged the 2 programs, so if people on XDA or anywhere on the web talk about using PC Companion to restore their device, they are not wrong, they are simply using the latest version ;)
Sony recently released their own package called 'flash tool' (to add to the confusion of noobs in the community), which deep down is a little easier to use and stripped down version of EMMA, which is a tool we mere mortals will probably never use as EMMA is the flash tool for Sony's repair shops and tech support. It's primary function is to allow owners of an unlocked bootloader device (or, 'open device' as Sony named it) to still use Sony firmwares and update their device, because as soon as you unlock the bootloader, the OTA updates will stop.
Things to remember on the files used by these tools:
- An FTF file is basically not more then a ZIP archive containing multiple SIN files, you can open the FTF using 7z/WinZip/WinRar and look inside it.
- A SIN file is a disk/partition image, which is encrypted by Sony. S1 (the bootloader) will check this encryption to make sure the image was not tampered with before it accepts it for flashing.
Fastboot flashing will always fail when the device is still in a locked bootloader state. For some models it is even disabled entirely or non-functional until you unlock the bootloader.
I am reading about the TA, what is it, why should I make a backup?
The TA partition (Trim Area) is a signed partition which holds various things which are unique to your device, like the device's IMEI, DRM keys and bootloader settings and configuration options. This partition can not be exchanged between devices, because it really is unique. If you would flash the TA backup from someone else it will cause a hard-brick rendering your device only useful as a paperweight...
When you unlock your bootloader you will lose all the DRM features on your device, this makes it valuable to have a backup of the unmodified version stowed away somewhere safe. You will need root level access to create that backup before unlocking. There is a tool called Backup TA which is widely used to create and restore backups of the TA partition. TWRP in XZDualRecovery can do the same.
When you restore the backup TA partition you made before unlocking the bootloader you will essentially re-lock the bootloader and restores the DRM keys. This process is (as far as we know up to now) undetectable by Sony's support staff, which makes it easy to restore the phone to stock for warranty driven support issues as unlocking your bootloader will void your warranty on the device (it is subject to local law though). That is why, for a lot of owners of a Sony device at least, it is considered to be the "Holy Grail" and is usually the reason for a lot of users to wait for a root exploit to be found before unlocking their bootloader.
Okay, I get it now. I would like to unlock my bootloader, how to proceed?
I'm not here to rewrite everything other people or Sony themselves can write just as well or even better, so I have a link for you:
Sony Developer World: Unlock your boot loader
Read it, it will teach you just about everything you need to know.
Once your bootloader is unlocked, your device will be much like a Nexus device when it comes to rooting, excluding the recovery partition, so that's why we flash or hotboot a custom kernel with a recovery, by using fastboot. If you are afraid of a terminal and typing commands, you can use a tool like QuickIMG or Flashtool to make your life easier.
Right, now I want root!
Well, if you have an 'open device', this is a lot easier then you think. Just remember that using root exploit kits is unnecessary and in some cases even risky as some packages do funky things or jeopardize your privacy.
Try to find a 'stock based' custom kernel. These are custom kernels built by the community to add features to the kernel but are meant to work with Sony's stock firmwares. I'm the maintainer of XZDualRecovery myself and created the Kernel Builder for the supported devices.
These custom kernels will NOT root your device (unless otherwise stated by the creator), but introduce a recovery to the boot process and with that you will be able to flash SuperSU to root your ROM.
But you just said Sony devices don't have a recovery partition, please... UN-confuse me!!
Yes, I did, and I'm right: there have been bright minds in the community who included a recovery in the boot image (the kernel partition) in the past and that way included a recovery on our Sony devices.
With the current 'open devices' policy from Sony, we now have:
- Recovery stored inside the system partition, which is meant for locked bootloader devices (closed devices) because they can not run custom kernels;
- Recovery stored in the boot image (for open devices);
- Recovery stored on the FOTA partition, but with a trigger from the regular boot image at boot (also for open devices);
- Recovery stored on the FOTA partition -renamed to recovery- together with an updated bootloader (for open devices, of course).
Hmm, okay... it's still confusing, but OK. My service menu says I'm rooted, but none of the root apps work properly, what gives?!
If you open the phone dialer app and on the keys see the letters below the digits, you can spell the word SERVICE. Type *#*#SERVICE#*#* and a service menu will pop up. Tap 'Service Info' and then 'Configuration'. Then you will see one of these lines there almost on the bottom of the list:
- "Rooting status: unknown": it's probably unlocked, but it was unable to verify that;
- "Rooting status: rooted": you have unlocked the bootloader;
- "Unlock bootloader allowed: YES/NO": this tells you if the bootloader is (vendor-) locked or not, if it says NO, you're out of luck.
The rooting status there is not telling your system is rooted, it tells you your bootloader is and will allow custom rom/kernel flashing. Don't confuse these two.
I'm not allowed to unlock my bootloader :( But I still want root, can I?
In some cases you can. It depends on the bugs found in specific firmware versions which allow a root exploit to be developed.
From the 2015 range of Xperia devices Sony started using dm-verity, which causes a bootloop once the system partition is modified. This modification of the system partition will be required to include a SU binary in the system to obtain root, so until a dm-verity defeating option is found, locked bootloader root or recovery will not be possible.
For older models, check the device forums and the cross device development forums to check out the community rootkits available. Usually it will tell you what ROM version it is intended for. Be careful with rootkits/roottools though, some are also found to be introducing malware to your device or sending privacy sensitive data to the creators. Use common sense, if you have no valid use for the root user level, keep it off your phone. If you already have recovery, you can use that to modify or clean your device instead.
I have rooted my phone, but whenever I try to modify something on it it spontaneously reboots or I get a message 'Permission denied" when trying to remount the system partition R/W! Why is that?
Like all manufacturers, Sony tries to make it difficult (or downright impossible) to modify the Android base system they created. Because if you can, anyone or anything which obtains root access can. This is a serious security risk, because if it's malware which puts itself on the system partition and locks up your phone, the only way around this is to wipe your entire device and restore a stock ROM using PC Companion or Flashtool. Of course, they have their own proprietary software to protect as well, but security is the main objective here. The really sensitive bits are stored in the TA partition as I explained earlier.
Sony (-Ericsson) had a service called RIC, which in time moved partially in to a kernel feature. What it does is monitor if system is remounted writeable. This usually is a situation you want to avoid at all costs so RIC will deny you permission, cause a kernel panic OR simply reboots your device to get out of that state.
"Remount-Reboot fix", RICKiller, RICDefeat, and XZDualRecovery all (attempt to) disable this service or stop the kernel from acting on a remount of system.
Hard-bricks, Soft-bricks, bootloops??
They are simple to understand, really:
- Hard-brick, TYPICALLY NOT RECOVERABLE: The bootloader stopped functioning, this can be caused by a bad flash/update or by restoring the wrong TA backup.
- Soft-Brick, ALWAYS RECOVERABLE: the system partition is corrupted or just simply empty, this causes the device to stall at boot. A soft-brick can also make the screen remain off, because of a bad or missing kernel image.
- Bootloops, ALWAYS RECOVERABLE: If the system gets powered up and then reboots during the start. This can be at the kernel splash screen or during the boot animation.
In case of a Soft-brick or Bootloop:
Use the installed recovery (if it still works), PC Companion, QuickIMG or Flashtool to restore your device to working order.
In case of a Hard-brick:
You can never recover from that state without physically opening your device and do some heavy duty engineering (JTagging) on it to flash back the correct bootloader/TA (read that link to see what it would take!). This is way too difficult for 98% of the community, which means that hard-bricking your device is typically the creation of a very expensive paper weight.
Please, be extremely careful when dealing with the TA partition.