How to debug BTX loader?

[John Baldwin]

On Monday, November 29, 2010 1:01:27 pm Darmawan Salihun wrote:
> Hi guys, 
> 
> I'm currently working on a BIOS for a custom Single Board Computer (SBC). 
> I have the required BIOS source code and tools at hand. 
> However, the boot process always stuck in the BTX loader 
> (the infamous "ACPI autoload failed") when I booted out of USB stick 
> (with the FreeBSD 8.1 USB stick image). 
> 
> I could get the system to boot into FreeBSD 8.1 
> (by keeping the CDROM tray open and close it when the board looks for 
> boot device, otherwise BTX will reboot instantly). 

Are you getting an actual BTX error message or a freeze?  BTX is just a 
minikernel written all in assembly.  It doesn't handle loading the kernel, 
etc.  All that work is done by the /boot/loader program (which is written in 
C).  You can find all the source to the boot code in src/sys/boot.  The BTX 
kernel is in src/sys/boot/i386/btx/btx/.

However, to debug this further we would need more info such as what exactly 
you are seeing (a hang, a BTX fault with a register dump, etc.).

-- 
John Baldwin