[syslinux] Can almost boot on UEFI win8.1 laptop

[Ady]

> I have a success story now. I tested with both 32-bit and 64-bit
> kernels, got the same problem, that is, nothing after "Loading
> vmlinuz... ok".
> 
> I took a punt on something. From the docs, I thought that the kernel
> parameter CONFIG_EFI_STUB is not required. However, I set it:
> 
> CONFIG_EFI_PARTITION=y
> CONFIG_EFI=y
> CONFIG_EFI_STUB=y
> CONFIG_EFI_MIXED=y
> CONFIG_FB_EFI=y
> CONFIG_DMI_SCAN_MACHINE_NON_EFI_FALLBACK=y
> CONFIG_EFI_VARS=m
> # CONFIG_EFIVAR_FS is not set
> CONFIG_EARLY_PRINTK_EFI=y
> 
> For a generic x86-64 kernel, after the "Loading vmlinux... ok", I now
> get kernel logging to the screen. It has a kernel panic as cannot run
> init, but that is another problem.
> 
> The same EFI config with a 32-bit kernel does NOT work.
> 
> Everything is somewhat clearer now, and I will refine the steps. I'll
> post a msg to the mail-list when I have got it all sorted out and
> documented.
> 
> Thanks for your patience.
> 
> Regards,
> Barry
> 

I am not an expert (very much far from it), but I think Syslinux does 
not rely on EFISTUB to boot EFI kernels. And yet, building the kernel 
with appropriate EFISTUB options might be helpful anyway. Syslinux 
might not need EFISTUB to boot the kernel, but perhaps the kernel 
itself needs the relevant EFISTUB options(?).

Since you have not mentioned "CONFIG_RELOCATABLE=y" for the building 
options for your kernel, I wonder whether you have tried it in your 
tests. Testing the results might give you some clues (but I cannot 
assure it will).

There is not much (or almost any) documentation targeted to building 
EFI kernels to be bootable specifically by Syslinux. UEFI is supposed 
to be some kind of (base for) simplification / standardization 
between firmware, bootloader and OS/kernel, so, in theory, most 
procedures were expected to be documented once and they should work 
for (most / all) UEFI bootloaders (except for the specific 
bootloader's configuration and/or features). In practice, this is not 
the case.

I could post links to a lot of different documents / articles / blogs 
/ wiki pages, targeting different levels of readers (developers, 
advance users, "plug and play" users and so on). Only few of them are 
really generic so to be helpful for different bootloaders, including 
Syslinux. Many of them have some skew / bias / particularities 
regarding one bootloader or another, or some type of hardware in 
particular, or some OS in particular.

So, although I have read useful documentation about UEFI, procedures 
and what not, I am slightly reluctant to post specific links to 
existent UEFI documentation.

Perhaps someone with experience in building kernels with UEFI support 
might consider posting in this Syslinux Mailing List; or maybe the 
Syslinux developers (past or present).

Regards,
Ady.