[syslinux] syslinux 6.03 does not boot some kernels

[Spike White]

>Date: Sat, 6 Dec 2014 09:12:19 -0500
>From: Gene Cumm <gene.cumm at gmail.com>
>To: Ady <ady-sf at hotmail.com>
>Subject: Re: [syslinux] syslinux 6.03 does not boot some kernels
>
>On Fri, Dec 5, 2014 at 9:51 AM, Ady <ady-sf at hotmail.com> wrote:
>>
>> It sounds as if syslinux.efi 6.03 is only capable of booting a Linux
>> kernel 3.3+ with an adequate config with EFISTUB. Considering that some
>> relevant changes were introduced to the Linux kernel in its 3.3 branch,
>> are these reported behaviors mean that prior kernels (such as the
>> current stable Debian Wheezy with kernel 3.2) are not bootable in UEFI
>> mode by Syslinux 6.03?
>>
>> Is Syslinux adding more conditions than really necessary so to boot
>> Linux kernels in UEFI mode?
>>
>> If I understand correctly, a Linux kernel 3.2 might not be able to
>> follow newer conventions, considering that such conventions /
>> conditions were implemented / refined with kernel 3.3, not before.
>>
>> Following adequate standards, rules and common conventions is fine, but
>> there should be some flexibility (or "fallback") for other cases, such
>> as for kernel 3.2 (which is going to be alive in Debian Wheezy for at
>> least a couple more years).
>>
>> So, can someone please clarify this situation?
>
>In an effort to get things started, I just wrote
>http://www.syslinux.org/wiki/index.php/Common_Problems#Linux_EFI_kernels
>
>I understand the CONFIG_RELOCATABLE issue well enough to write about
>it however Ady seems to have stumbled upon a real key for the
>pre-Linux-3.3 kernels.

If I'm understanding correctly, I think H. Peter Anvin on Tues Nov 18th,
10:24:15 PST 2014 explained this pre-Linux-3.3 kernel problem well.

It was a discussion of grub2 booting the kernel in a "hostile" way -- not
using the built-in kernel EFI bootloader.  And thus, grub2 is able to boot
earlier kernels, while syslinux follows the rules.  And is not able to.

H. Peter referenced https://www.kernel.org/doc/Documentation/efi-stub.txt
for a fuller explanation.

Great job writing up documentation, Gene.  If H. Peter's explanation is
congruent with Ady's Linux pre-3.3 kernel research, would you add a link to
this fuller explanation?

i.e.,
    https://www.kernel.org/doc/Documentation/efi-stub.txt

in the "Linux EFI pre-3.3" section?  That fuller explanation really cemented
it in my mind the strong rationale for following the rules.

Spike