Okay, so, what is Hummingbird Interceptor Boot Loader (HIBL)?
It allows to load any amount of data (limited by size of RAM block, the biggest one single block available is 256MB) through USB connection with PC under any specified address into memory and then execute it.
It does consist of 2 pieces fused together - BL1_stage1 and BL1_stage2.
Each stage starts from 16bytes (4 ARM WORDs) of secure boot header. In stage1 these are mandatory, in stage2 they can be random (nulled them in my code), so EntryPoint of each stage does start at its 0x10 offset.
BL1_stage1, loaded under 0xD0020000 address, is short code, digitally signed
by Samsung. It has been released to break "Chain of Trust" and alter Secure Boot into Non-Secure Boot process. Literally stage1 just do some compare operations and then jumpout to BL1_stage2. (Yes, I also see no point of releasing hardware secured CPU version together with software which is bypassing it's security)
BL1_stage2, must be placed at 0xD0022000 address (it's fused together with stage1 into HIBL, so it's at 0x2000 offset of HIBL.bin) it is unsigned
because Secure Boot Context, prepared by iROM (BL0) has been already ignored by stage1.
Its FASM_ARM sourcecode:
This is where the code start real work, it does begin with standard ARM core jump vector table (just to keep stick to standard, these aren't used anyway).
1. It does use I9000 BL1_stage2 functions (init_system) which I linked to it, these are used to init DMC controllers, as to this point code is executing in and working with very tiny, 96KB iRAM space, after calling this function it turns all 512MB of RAM available.
2. Make sure DMC is configured properly (write some value to address 0x40~~ memory space, then read it and compare with previously written)
3. Reinit iRAM heap to the BL0 initial state (to convince it USB dload mode haven't been called yet), by storing and restoring UART pointer only (to keep debug output flowing properly)
4. Call iROM usb_downloader function.
5. Read the address where downloaded data has been placed.
6. Jump into this address.
This, properly used provides similiar debug output (similiar, because its outdated testlog)
Uart negotiation Error
Hummingbird Interceptor Boot Loader (HIBL) v1.0
Copyright (C) Rebellos 2011
Calling IBL Stage2
Testing BL3 area
Please prepare USB dltool with BL3
Desired BL3 EP: 0x40244000
Download complete, hold download mode key combination.
//OUTPUT BELOW IS COMING FROM SBL
Set cpu clk. from 400MHz to 800MHz.
IROM e-fused - Non Secure Boot Version.
It opens infinite capabilities. Instead of SBL to unbrick, Uboot can be loaded, or any armlinux kernel. It's all up to you - XDA Developers.