Re: Help Required legacy booting from an EFI

[Rod Smith <rodsmith@rodsbooks.com>]

On 09/20/2016 02:38 PM, Saqib Khan wrote:
> 
> Booting using BBS is my option,i was already looking for this and I have
> attempted to modify EFIBootManagerMenuApp to work with legacy boot used ().
> 
> I have system with CSM support so essentially i will be doing all my work
> on physical system not on virtual machine.
> 
> The detail you provided about BBS device path and then adding it to boot
> menu is abstract for me .if you can detail this procedure a bit it will be
> helpful, if required I can share the code snippet with you

You may want to look at the relevant bits of code in my rEFInd boot manager:

https://sourceforge.net/projects/refind/

In particular, look at the functions in EfiLib/legacy.c and
refind/legacy.c. One big caveat is that rEFInd includes TWO code paths
for launching BIOS-mode boot loaders -- one it inherits from its
predecessor project, rEFIt, and works only on Macs; and the other was
contributed by John Bressler and works only on UEFI-based PCs. Since I
wrote neither, I can't offer a lot of insight into how either one works.
(The Mac side, in particular, is pretty mysterious to me.) There may be
a better way to do it than what rEFInd does, but at least rEFInd's code
does work. Thus, if you need a concrete example, the rEFInd code might
be helpful.

-- 
Rod Smith
rodsmith@rodsbooks.com
http://www.rodsbooks.com