[syslinux] [PATCH] new *br: Show handoff data

[Michal Soltys]

On 10-11-26 19:23, Gene Cumm wrote:
> git://git.zytor.com/users/genec/syslinux.git
>
> Branch handoff-mbr-for-hpa
>
> This is a piece of code that can be used in place of a MBR or VBR/PBR
> (master boot record; volume/partition) in order to examine the data
> handed to the respective boot code.  AX, SS, and SP are destroyed
> before examining anything.  I set an internal restriction that limits
> it to 420 bytes such that it could be used with a FAT32 file system.
>
> HPA: Should this be renamed?  I have intentionally skipped adding it
> to the Makefile (for now) for this reason.
>

I did something similar when I was testing my chain module. It dumps 
registers (none are destroyed), bpb info and dos + gpt handover data. It 
can be booted as a file= / sect=, it can chain from itself as well 
(depending on seg= / sect=). After everything is done/dumped, it reloads 
disk 80h.

Code/data takes 4 sectors though (3 remaining ones are loaded using 
handover information, unless it was loaded as a file=) - couldn't really 
stuff it all in just 400ish bytes :) 1.5 sectors is roughly unused 
though. Overall - it doesn't care about filesystem at all, it does 
respect most of the important bpb fields though.

I needed something like that to test the functionality, including 
effects of more dangerous options (mbrchs, un/hideall, setbpb/bpb 
autodetection among other things).

Could be potentially useful, so just tell if you want to use it.