[syslinux] chainloading syslinux from an EFI partition to an ext4

[Ady]

 (snip) 
 
> > As per the intended setup, it is not possible. There are several
> > reasons for such impossibility.
> 
> Could you elaborate a bit more? What are the impediments?
 
 (snip) 
 
> -- 
> igor
 
Posting an explanation for every current impediment (as of v.6.03) and, 
optionally, potential future improvements, would take (me) some (long) 
time, it would be boring to read, and it would not actually bring you 
to a realistic working solution of your attempted setup.

The most basic problem with your attempted setup, IMHO, is that 
initially you want to boot with a UEFI bootloader (syslinux.efi) in 
UEFI mode - that's fine - but then you want to chain to a BIOS 
bootloader (EXTLINUX, ldlinux.sys).

As of version 6.03, Syslinux in UEFI systems lacks many 
potentially-useful features (e.g. chainloading another EFI tool). I 
would tend to think that chainloading from one (U)EFI firmware 
architecture to a BIOS-based bootloader would probably be a low 
priority for developers (if it would be ever possible).

Regarding the alternative, loading kernels located in other partitions 
(and using different file systems), there have been some attempts to 
add such feature to Syslinux (this is not as an easy task as some 
people might think). I guess that the suggested patches might be 
evaluated at some point, but I am going to assume (as an educated 
guess) that it will take more time than you are willing to wait.

Throughout this email thread, there have been some comments about the 
possibility to boot Windows and Linux, both being located in the same 
physical device, and (for some unknown reason) not willing to use the 
ESP for kernels. These conditions might add complexity; whether 
unnecessarily or not, I don't know.

Since I was asked to expand on my prior reply, I should modify my 
initial qualification from "impossible" (which I used as an exaggerated 
short description so to convey the very low probability to be 
successful in your attempted setup and conditions while using Syslinux 
v.6.03) to some other qualifier. How about: "hopefully it will be 
possible in some future version, using some alternative method"?

Regards,
Ady.
 
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