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GTI9100GBootloaderFreedom » History » Version 11

Denis 'GNUtoo' Carikli, 03/07/2020 12:09 AM

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h1. I9100GBootloader
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{{toc}}
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h2. How to check if you have a signed bootloader
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h3. How to check from the bootloader interface to install the recovery.
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To do that you need to get into the ODIN MODE that is typically used to install the Replicant recovery:
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# Start the device by holding the following key combination: *Volume down, Select, Power*,
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# Hold the key combination until the device shows a *Warning* message.
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# Confirm that you want to download a custom OS using volume up
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# Make sure the device is in *Downloading* mode
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When this is done, it should show some text:
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<pre>
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ODIN MODE
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PRODUCT NAME: GT-I9100G_CHN_CHN
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</pre>
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Here CHN_CHN probably refers to the Chinese version. And it looks like that version has a signed bootloader: According to "a thread on the XDA developers forum":https://forum.xda-developers.com/galaxy-s2/development/guide-repair-totally-sleep-dead-boot-t1701471 "Means that you own a chinese bootloader locked I9100G. You can't flash any other bootloader than the chinese one."
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h2. How to check with command line utilities
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To get the bootrom to try to boot on USB, you need to do the following:
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* Connect the USB cable to the device but make sure it's not connected on the computer.
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* Power off the device
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* Connect the USB cable
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If we do that, we get the following in the kernel log of your laptop:
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<pre>
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usb 1-1: new high-speed USB device number 24 using ehci-pci
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usb 1-1: unable to get BOS descriptor or descriptor too short
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usb 1-1: New USB device found, idVendor=0451, idProduct=d00f, bcdDevice= 0.00
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usb 1-1: New USB device strings: Mfr=33, Product=37, SerialNumber=0
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usb 1-1: Product: OMAP4430
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usb 1-1: Manufacturer: Texas Instruments
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</pre>
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We can also try to get a bit more infos with omap-usb-boot:
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<pre>
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$ sudo omap-usb-boot -v -w boot invalidbootmedia
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Finding and opening USB device
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Found and opened omap4 USB device: OMAP4430
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ASIC device id: 4430, HS device
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Booting from device invalidbootmedia...
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Booting device invalidbootmedia not found
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Booting from device failed
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</pre>
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Here we know the device is signed because it's a "HS device".
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If it was not signed it would print "GP device" instead.
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h3. Using the Android version or other devices properties?
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"hpagseddy/i9100g_xloader":https://github.com/hpagseddy/i9100g_xloader is based on "ths-backup/i9100g_xloader":https://github.com/ths-backup/i9100g_xloader which has an ics (Icecream Sandwitch, an Android version) branch only.
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It's still unclear if there is some correlation between Android version and signed bootloaders.
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The device that was given to [[People#Denis-GNUtoo-Carikli|GNUtoo]] that has a signed bootloader also has the following characteristics:
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*Software state*: Running the stock OS, unmodified
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*Android version*: Android 2.3.6
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*Baseband version*: IG9100GZCLC2
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*Build number*: GINGERBREAD.ZCLC2
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*Kernel version*: 2.6.35.7 se.infra@SEI-30#2
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At this point it's also still unclear if any of the characteristics above correlate to signed or unsigned bootloaders.
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h2. Source code
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* https://github.com/hpagseddy/i9100g_xloader This got rebuilt and flashed, and it worked on the device it was tested on.
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* https://blog.the-leviathan.ch/?p=408
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h2. TODO
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* Understand how to get unsigned versions (Android version, serial number, etc)
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* Get a device with u-boot and ask samsung for source code
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* Try to boot the xloader nevertheless, as the device could be in some "verify but not enforce mode" for signatures