Re: xorriso and EFI boot images

["Vladimir 'φ-coder/phcoder' Serbinenko" <phcoder@gmail.com>]

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Thomas Schmitt wrote:
> Hi,
>
> the fresh development upload of xorriso-0.5.5
> with timestamp 2010.04.22.160615 implements the
> wish about --efi-boot :
>
>   
I've tested xorriso version   :  0.5.5 Version timestamp : 
2010.04.22.221241 and it worked fine.

> Vladimir Serbinenko wrote 17 Apr 2010:
>   
>> I would like to have efi+bios cd with 2 eltorito
>> entries: one with platformid=0 and another one with platformid=0xef.
>> [...]
>> I would like that on hybrid BIOS always come in
>> default entry to avoid hitting BIOS bugs
>> In case of just EFI the Section header entry and Section entry become
>> Validation entry and default entry.
>>     
>
> So now xorriso -as mkisofs has this provisory
> behavior:
>
> -b is for 80x86 BIOS images, platform ID 0.
> Options -boot-load-size, -no-emul-boot,
> -boot-info-table affect this -b boot image.
>
> --efi-boot is for EFI images, platform id 0xef.
> Hardcoded are: no emulation, no boot info table.
> The load size is obtained from the size of the
> EFI image file and rounded up to full 512 byte
> blocks.
>
> Prone to change is the current rule that the
> EFI image always is second if a BIOS image is
> present. I will probably make this depending on
> the sequence of options in future.
> Please take care in grub-mkrescue to express
> your desired sorting by giving -b before
> --efi-boot.
>
>   
It's already so.
> ------------------------------------------------
>
>
> Quote from El Torito 1.0 paragraph 2.3
> "The section header has an identification string.
>  If the BIOS understands the ID, string it may
>  choose to boot the system using one of these
>  entries in place of the INITIAL/DEFAULT entry."
>
>   
> What does that mean: "the BIOS understands" ?
> Do we have to write something particular in
> there for EFI ?
> Any idea what one would have to write in case of
> a 80x86-BIOS image ?
>   
It looks like ISOs I had under the hand with multiple boot images just
zero-fill this field.

> The Validation Entry has an ID too.
> But that is defined as quite meaningless:
> "This is intended to identify the
>  manufacturer/developer of the CD-ROM."
>
>   
Actualy it seems like it can be an arbitrary string and BIOS doesn't
care about it. Just setting it to all zeros is ok. Looking at few isos I
had under the hand:
FreeBSD ISOs: "The FreeBSD Project.  h"
NetBSD: ""
DEbian GNU/Hurd: ""


>   
> ------------------------------------------------
>
>
> Currently libisofs is able to write and read up
> to 32 boot images. It writes each image entry
> into an own section, but i plan to allow sections
> of more than one image entry and user provided
> ID strings.
>
> xorriso on the other hand got only a primitive
> extension efi_path, which lives beneath bin_path.
> This is not flexible. So i plan for improvements.
> Nevertheless, the option sequence
>   -b ... --efi-boot ...
> is promised to always lead to Vladimir's intended
> boot catalog structure.
>
> ------------------------------------------------
>
>
> I tested with dummy boot images.
> The boot catalog entries seem to be ok.
> Now i am curious whether i misunderstood the
> specs somewhere or whether it really would boot.
>
>
> Have a nice day :)
>
> Thomas
>
>
>
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>
>   


-- 
Regards
Vladimir 'φ-coder/phcoder' Serbinenko



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