This is the boot chain of the Motorola Milestone, as far as we know. X-Loader and U-Boot are missing in this diagram because they have been replaced by Motorola's mbmloader, which is calles ISW image, and contain CH table, TOC, PPA and ISW parts. The OMAP architecture permits that the bootstrap code be located in an SD-Card, provided that the NAND Flash is unable to boot and that the SD-Card contains a proper FAT32 filesystem and a .IFT file signed as required by the HS mode. If the processor had been in GP mode, we could've followed these steps to boot from the SD-Card; unfortunately that's not the case. Some innards of similar Boot ROMs are described here and here and here.
|OMAP boot ROM||OMAP core||armv7-a||File:Omap 3430.bin.gz, File:Omap 3630.bin.gz||File:Omap 3430 bootrom.idb.gz|
|mbmloader||OMAP3430 core||armv7-a||none||MBMloader-0.5A reversed|
|mbm||OMAP3430 core||armv7-a||none||MBM-90.72 reversed|
|Wrigley arm boot ROM||Wrigley3G ARM core||arm9||none||none|
|Wrigley dsp boot ROM||Wrigley3G TMS320c55x+||c55x+||File:Wrigley dump.gz((this is partial dump of wrigley3g dsp memory (addressess: 0xF00000-0xFFFFFF). boot rom is only very small part of it.))||none|
|Wrigley3G RTXC OS loader||Wrigley3G ARM core||arm?||none||BPloader reversed|
|Wrigley RTXC OS||Wrigley3G TMS320c55x+||c55x+||none||none|
|Main DSP/IVA boot ROM||TMS320C6454||MIPS (c64x+ edition)||none||none|
|Main DSP/IVA firmware||TMS320C6454||MIPS (c64x+ edition)||File:Baseimage.dof.gz||none|
|WiLink firmware||WiLink 6.0 TPS656905||arm||Wilink 6.0 NVS and Wilink 6.0 firmware||none|
|Power Manager Boot ROM||TWL5030||Vendor Specific (ASIC)||File:Firmware 1 2x.bin.gz||none|
|Touch Panel Controller boot ROM||AVR ATmega324P||AVR 8-bit||none||none|
|Linux kernel||OMAP3430 core||arm||none||none|
All recent IDA databases of bootloaders can be found here Gitorious
(!) the CH table can be signed with CSST along with the Initial Software image. Whether Motorola did include it in the signed image or left it unsigned is unknown (and risky to test!). ((Citation needed))
After kokone has found that the origin mbmloader contained bit errors, the correct mbmloader binary image has been obtained again. That he has been able to validate all the signatures in mbmloader and the CH table is not part of any signed content.
(!!) in fact mbm and mbmbackup are binary identical, so mbmbackup DOES contain certificates. But its certificates are not referenced in the cdt table because it is used directly by the mbmloader (and the mbmloader doesn't use the cdt table, as discovered by yakk). In the Droid mbm and mbmbackup are binary identical, just like in the Milestone (but with a different code version). One Droid user (Orgg) had an incident with his phone in which his mbm partition became corrupt, and the phone wouldn't boot at all after that. This would suggest that the mbmbackup partition is not used for automatic recovery. User [mbm] reports that his Droid originally came with different mbm and mbmbackup, but after an update pushed by Verizon they became identical. In light of this, the mbm_backup_attack was proposed but then found to be flawed and discarded.