Bootable unsigned HV/kernel in the works...

via xboxscene

Since we have an exploit in the hypervisor (kernel 4532 and 4548) and recently found a way to downgrade to these kernels, some hackers over at the XBH forums are working on a way to boot homebrew code on the Xbox360. Linux was already done via the linux bootloader, but for homebrew we'll need another bootloader obviously that will allow to boot 'unsigned' xbox 360 code.

From Arnezami on XBH:

For the last 4-5 weeks I have been working very hard to reboot the xbox into an unsigned kernel/hv. And I've been making quite some progress. Smiley

I am now capable (using the KK exploit as starting point) to reboot from the moment the CB section starts the CD section up to POST 0x6C (!) in the boot process. Meaning that all three cores are running in an unsigned kernel/hv at that point.

What I'm doing is loading the CD section back into memory (where it would normally be during boot) and restart it. This CD section is changed to contain a kernel/hv patcher (which I now use to debug the kernel startup). So in fact I can already change the kernel/hv at will ;)

The difficulty has been (and still is) to restore the xbox into a state it was during boot. Most of the cpu/mmu related stuff have been restored now and thats why it already goes that deeply into the boot process. But some problems still remain (possibly interrupt/southbridge related). I'm still working on those. I'm also thinking of modifying what I've created into a more replicatable and managable form so others can take a look at some of these issues too (to speed up the progress).

Anyway. If we are successful in re-booting into a (patched) kernel it should also be possible to re-boot into any kernel (including the new ones). If we can do that we can (for example) avoid the whole fuse-burning dilemma (essentially by faking it). For that we would probably also need a second NAND (or some other storage device like a memory card) to store the new kernel/dash/kv/settings etc but thats something to discuss later on.
Back to work...