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Jonathan Herrewijnen 2024-08-12 16:58:34 +02:00
parent 19d20965db
commit de8395b286
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documentation/source/BootROM_8890/boot_chain.rst
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@ -3,7 +3,7 @@
Booting
=======
After exploitation the goal is to fully boot the device.
After exploitation the goal is to fully boot the device.
Current boot chain:
@ -19,9 +19,63 @@ As done by Frederic, the bootrom can be dumped using his provided scripts, and c
./exynos-usbdl e payloads/Exynos8890_dump_bootrom.bin dumped_sboot.bin
scripts/split-sboot-8890.sh dumped_sboot.bin
This results in the following files:
.. list-table:: bootrom stages
:header-rows: 1
* - File
- Strings output
- Likely boot stage?
* - sboot.bin.1.bin
- Exynos BL1
- BL1
* - sboot.bin.2.bin
- BL31 %s
- BL31
* - sboot.bin.3.bin
- Unsure. Contains strings like: TOP_DIV_ACLK_MFC_600 and APOLLO_DIV_APOLLO_RUN_MONITOR
- BL2?
* - sboot.bin.4.bin
- Contains more textual information, and references to post BL2 boot, and android information
- Kernel boot/BL33?
debugger
========
Some other information about the debugger and it's current state.
After the initial loading of the debugger, the state reported is:
.. code:: bash
root | DEBUG |
X0 : 0x0 | X1 : 0xffffffff | X2 : 0x20215d8 | X3 : 0x2021894 | X4 : 0x4 | X5 : 0x0 | X6 : 0x0 |
X7 : 0x136c0008 | X8 : 0x2069000 | X9 : 0x0 | X10 : 0x2070000 | X11 : 0x0 | X12 : 0x0 | X13 : 0x0 |
X14 : 0xf | X15 : 0x206d000 | X16 : 0x9 | X17 : 0x0 | X18 : 0x1 | X19 : 0x2000 | X20 : 0x2069000 |
X21 : 0x0 | X22 : 0x0 | X23 : 0x0 | X24 : 0x0 | X25 : 0x0 | X26 : 0x0 | X27 : 0x1 |
X28 : 0x0 | X29 : 0x2020f00 | LR/X30 : 0x20219b8 | SP/X31 : 0x2020ef0
With the original bl1
.. code:: bash
root | DEBUG |
X0 : 0x0 | X1 : 0x1 | X2 : 0x20215d8 | X3 : 0x2021894 | X4 : 0x4 | X5 : 0x0 | X6 : 0x0 |
X7 : 0x136c0008 | X8 : 0x2069000 | X9 : 0x0 | X10 : 0x2070000 | X11 : 0x0 | X12 : 0x0 | X13 : 0x0 |
X14 : 0xf | X15 : 0x20c4000 | X16 : 0x9 | X17 : 0x0 | X18 : 0x1 | X19 : 0x2000 | X20 : 0x2069000 |
X21 : 0x0 | X22 : 0x0 | X23 : 0x0 | X24 : 0x0 | X25 : 0x0 | X26 : 0x0 | X27 : 0x1 |
X28 : 0x0 | X29 : 0x2020f00 | LR/X30 : 0x20c0000 | SP/X31 : 0x2020ef0
With a modified bl1
.. code:: bash
root | DEBUG |
X0 : 0x0 | X1 : 0x1 | X2 : 0x20215d8 | X3 : 0x2021894 | X4 : 0x4 | X5 : 0x0 | X6 : 0x0 |
X7 : 0x136c0008 | X8 : 0x2069000 | X9 : 0x0 | X10 : 0x2070000 | X11 : 0x0 | X12 : 0x0 | X13 : 0x0 |
X14 : 0xf | X15 : 0x20c4000 | X16 : 0x9 | X17 : 0x0 | X18 : 0x1 | X19 : 0x2000 | X20 : 0x2069000 |
X21 : 0x0 | X22 : 0x0 | X23 : 0x0 | X24 : 0x0 | X25 : 0x0 | X26 : 0x0 | X27 : 0x1 |
X28 : 0x0 | X29 : 0x2020f00 | LR/X30 : 0x20c0000 | SP/X31 : 0x2020ef0
bl1
===
@ -90,6 +144,13 @@ Replacing this function with our debugger makes us jump back:
However this does not fully run bl1, so we will have to dig a bit deeper to see the puropose and when to jump back to the debugger.
Authentication of BL1 seems to be done at ``0x0012848``. With return value '0' expected when this function is executed, to execute other functions.
.. figure:: images/bl1_auth_references.png
:align: center
BL1 authentication.
purpose
-------
bl1 interacts with several pheriperals, from the DTB these are: