Samsung_S7/documentation/source/BootROM_8890/boot_chain.rst

129 lines
3.9 KiB
ReStructuredText
Raw Normal View History

2024-08-05 17:37:13 +00:00
=======
Booting
=======
After exploitation the goal is to fully boot the device.
2024-08-06 22:20:30 +00:00
Current boot chain:
.. figure:: images/boot_chain.drawio.svg
:align: center
Boot chain
2024-08-05 17:37:13 +00:00
debugger
========
Some other information about the debugger and it's current state.
2024-08-06 22:20:30 +00:00
bl1
===
Loads at address ``0x02024000`` and contains some form of header.
There seems to be a samsung header format, where the first 4 bytes define the entry point of the binary.
In this case this entry is ``+0x10`` so we jump to ``0x02024010``.
.. code-block:: python
fwbl1 = open("../S7/bl1.bin", "rb").read()
self.cd.memwrite_region(0x02024000, fwbl1)
def jump_fwbl1():
self.cd.arch_dbg.state.LR = 0x2069000
self.cd.restore_stack_and_jump(0x02024010)
jump_fwbl1()
However, this does not result in a jump back to the debugger.
The reason for this is the following code in bl1:
.. code-block:: c
iVar3 = FUN_02024320();
if (iVar3 == 1) {
(*(code *)(ulong)uRam0000000002020108)(0,1);
}
This code uses a predefined ROM function(I was looking for it) and jumps back to that function when it's done.
This function is at address ``0x020200e8``, looking in our IMEM dump we can see where in the ROM this points to:
.. code-block:: c
DAT_02020108 XREF[2]: FUN_00001708:000018b4(W),
FUN_02021970:02021a40(R)
02020108 90 57 00 00 undefined4 00005790h
Replacing this function with our debugger makes us jump back:
.. code-block:: python
# Overwrite jump back
self.cd.memwrite_region(0x02020108, p32(0x2069000))
self.cd.memwrite_region(0x020200e8, p32(0x2069000))
def jump_bl1():
self.cd.arch_dbg.state.LR = 0x2069000
self.cd.restore_stack_and_jump(0x02024010)
# self.cd.restore_stack_and_jump(0x02021810)
bl1 = open("../S7/bl1.bin", "rb").read()
self.cd.memwrite_region(0x02024000, bl1)
self.usb_write(b"FLSH")
# auth_bl1()
jump_bl1()
assert self.usb_read(0x200) == b"GiAs", "not jumped back to debugger?"
self.cd.arch_dbg.state.print_ctx()
root | DEBUG |
X0 : 0xc00000 | X1 : 0x2069000 | X2 : 0x0 | X3 : 0x2023114 | 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 : 0x20200e8 | X20 : 0x0 |
X21 : 0x80000000 | X22 : 0x0 | X23 : 0x0 | X24 : 0x0 | X25 : 0x0 | X26 : 0x0 | X27 : 0x1 |
X28 : 0x0 | X29 : 0x2020ed8 | LR/X30 : 0x202419c | SP/X31 : 0x2020ec0
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.
purpose
-------
bl1 interacts with several pheriperals, from the DTB these are:
.. code-block:: dtsi
/* FSYS0 */
pinctrl_5: pinctrl@10E60000 {
compatible = "samsung,exynos8890-pinctrl";
reg = <0x0 0x10E60000 0x1000>;
interrupts = <0 212 0>;
};
/* FSYS1 */
pinctrl_6: pinctrl@15690000 {
compatible = "samsung,exynos8890-pinctrl";
reg = <0x0 0x15690000 0x1000>;
interrupts = <0 202 0>;
};
/* PERIC1 */
pinctrl_9: pinctrl@14CC0000 {
compatible = "samsung,exynos8890-pinctrl";
reg = <0x0 0x14CC0000 0x1000>;
interrupts = <0 460 0>;
};
pmu_system_controller: system-controller@105C0000 {
compatible = "samsung,exynos8890-pmu", "syscon";
reg = <0x0 0x105C0000 0x10000>;
};
rtc@10070000 {
compatible = "samsung,s3c6410-rtc";
reg = <0x0 0x10070000 0x100>;
interrupts = <0 73 0>, <0 74 0>;
clocks = <&clock 157>;
clock-names = "gate_rtc";
};
2024-08-05 17:37:13 +00:00
2024-08-06 22:20:30 +00:00
BL31
----
2024-08-05 17:37:13 +00:00
2024-08-06 22:20:30 +00:00
Setups EL3 stuff, probably in preperation of loading trustzone