Syslinux - Nov 2013 - Sysinux 6 will not boot ISOs on BIOS (i.e. pre-UEFI) systems

> As stated earlier, the next version of xorriso will have
> sort weight 2 for El Torito boot images by default.
> But it will not harm to explicitely use --sort-weight
> options with old and new versions of xorriso.
 
FWIW,
 mkisofs is supposed to assign a +2 sort weight by default to the 
eltorito boot image and +1 to the boot catalog, at least when no sort 
file is provided.

I don't know about the sort weight assigned to the boot image by 
mkisofs in case there is a sort file specified that does not 
explicitly include the weight for isolinux.bin.

I also don't know the default weights in mkisofs when there is some 
alternative boot image ("-eltorito-alt-boot" and related options) in 
addition to isolinux.bin.

AFAIK, there is no mkisofs parameter to specify the sort weight of 
one specific file, other than using "-sort <sort_file>", but I
could
be wrong.
 
> 
> More complicated weight structures may be defined in a
> file on disk and read by option --sort-weight-list or
> --sort-weight-patterns.
> 
> 
> > Note that if using isolinux.bin from syslinux-4.07 works fine in both
> > cases (under high LBA addreses and low).
> 
> So maybe it is not BIOS but SYSLINUX which does not like
> the high addresses. Or both of them in happy cooperation.
 
I guess that being isolinux.bin 4.07 smaller than 32KiB (24KiB), 
while isolinux.bin 6.02 being bigger (42KiB), and with the addition 
of multiple alternative boot images in the same ISO, the chances of 
isolinux.bin being located on a higher sector in the media seem to be 
higher.

So, perhaps the potential problem was always there, just that the 
chances of actually triggering it were much lower?

Whichever the case, is there anything that Syslinux can do so to at 
least reduce the chances of triggering this problem? If there isn't, 
is changing the sort weight a solution? Is it the only one? Is it the 
best one? HPA? Anyone?

Regards,
Ady

Hi,

Ady wrote:
> I guess that being isolinux.bin 4.07 smaller than 32KiB (24KiB), 
> while isolinux.bin 6.02 being bigger (42KiB), and with the addition 
> of multiple alternative boot images in the same ISO, the chances of 
> isolinux.bin being located on a higher sector in the media seem to be 
> higher.
> 
> So, perhaps the potential problem was always there, just that the 
> chances of actually triggering it were much lower?
If i get Gerardo right, then he can trigger it on 6.02 without
isohybrid and EFI just by the start address of the boot image.
The image size does not change by this.
Further he reports that high addresses do not harm success with
4.07.

On my own test system, a high address (263921) and 6.02 work fine.

So we have some ingredient in the boot firmware, and some other
in a difference between SYSLINUX 6.01 and 4.07.

The reported symptoms differ slightly:

Carl Duff:
> > ISOLINUX 6.02 ETCDisolinux: Disk error 01, AX = 4279, drive FE
Gerardo Exequiel Pozzi:
> > When trying to boot the bad iso, I can see the isolinux welcome
message
> > but not complete "ISOLINUX 6.02 ETCD", then reboot
inmediatelly.

Have a nice day :)

Thomas

On 11/25/2013 08:40 AM, Thomas Schmitt wrote:
> Hi,
> 
> Ady wrote:
>> I guess that being isolinux.bin 4.07 smaller than 32KiB (24KiB), 
>> while isolinux.bin 6.02 being bigger (42KiB), and with the addition 
>> of multiple alternative boot images in the same ISO, the chances of 
>> isolinux.bin being located on a higher sector in the media seem to be 
>> higher.
>>
>> So, perhaps the potential problem was always there, just that the 
>> chances of actually triggering it were much lower?
> 
> If i get Gerardo right, then he can trigger it on 6.02 without
> isohybrid and EFI just by the start address of the boot image.
> The image size does not change by this.
> Further he reports that high addresses do not harm success with
> 4.07.
Exactly, as I described previously, the simple steps to make a broken
iso image on my system. Just an ISO with two files isolinux.bin and a
"garbage" file just to force isolinux.bin go to a high LBA address. (
three files counting boot.cat). No isohybrid-mbr, no eltorito-alt-boot
for EFI.

Looks like there is something beyond LBA 65535 (As Mattias confirmed)
with isolinux.bin from 6.02.

-----
#!/bin/sh

mkdir -p /tmp/test/isolinux
cp ~/isolinux-6.02.bin /tmp/test/isolinux/isolinux.bin

## Push isolinux.bin at LBA 65570 (0x00010022)
truncate -s 128M /tmp/test/coco

## Push isolinux.bin at LBA 65058 (0x0000fe22)
# truncate -s 127M /tmp/test/coco

xorriso -as mkisofs \
        -eltorito-boot isolinux/isolinux.bin \
        -eltorito-catalog isolinux/boot.cat \
        -no-emul-boot -boot-load-size 4 -boot-info-table \
        --sort-weight -1 isolinux/isolinux.bin \
        --sort-weight +1 coco \
        -output /tmp/test.iso \
        /tmp/test/
dumpet -i /tmp/test.iso
cdrecord -v -dev=5,0,0 -dao /tmp/test.iso
-----

I can push isolinux.bin (4.07) to a really high LBA address and boot
without any issue. (Load LBA: 2048034 (0x001f4022)) ~4G


> 
> On my own test system, a high address (263921) and 6.02 work fine.
> 
> So we have some ingredient in the boot firmware, and some other
> in a difference between SYSLINUX 6.01 and 4.07.
> 
> The reported symptoms differ slightly:
> 
> Carl Duff:
>>> ISOLINUX 6.02 ETCDisolinux: Disk error 01, AX = 4279, drive FE
> 
> Gerardo Exequiel Pozzi:
>>> When trying to boot the bad iso, I can see the isolinux welcome
message
>>> but not complete "ISOLINUX 6.02 ETCD", then reboot
inmediatelly.
> 
> 
> Have a nice day :)
> 
PS: You are welcome Thomas (was: Thank you, too, for flying xorriso) hehe ;)
> Thomas
> 
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> 

-- 
Gerardo Exequiel Pozzi
\cos^2\alpha + \sin^2\alpha = 1

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Am 25.11.2013 12:40, schrieb Thomas Schmitt:
>
> On my own test system, a high address (263921) and 6.02 work fine.
>
> So we have some ingredient in the boot firmware, and some other
> in a difference between SYSLINUX 6.01 and 4.07.
>
> The reported symptoms differ slightly:
In September Thomas and I discussed this topic off the list regarding 
Isolinux 5.0x after some colleagues signalled trouble booting the merged 
image of a rescue CD with further DVD content (the issue: I prepared a 
rescue CD that worked fine everywhere, when merging this CD with a few 
thousand files and re-named boot files to a DVD, it stopped booting on 
some machines). On all of my test systems everything worked even with 
high LBAs while the troubles my colleages had were as described: ETCD 
disk error plus halt, reboot or just hanging systems. After comparing 
the images of the rescue system alone with the merged DVD we noticed the 
different LBAs of isolinux.bin. When everything booted fine on every 
machine after moving isolinux.bin well within the LBA 65.535 limit we 
stopped investigating and moved on. Since the problem just occured on 
some BIOSes and was fixed after moving isolinux.bin to low LBA we 
thought the sole problem was the BIOSes.

If someone is suspecting a strange interaction between changes in 
Isolinux from 4.0x to 5.0x and buggy BIOSes we might however try to 
narrow down the factor Isolinux. On December 11th I will be at the 
Springer offices in Hamburg again where I can test some prepared images 
on affected hardware and document BIOS vendors and versions (we 
identified four out of twenty machines in the test pool, built between 
2005 to 2010) to be affected. I am however not very keen to do so, 
because: With a few hundred thousand bootable ISOs on computer magazines 
in Europe and Southern America that I prepare every year we run into the 
weirdest BIOS and UEFI issues. Sometimes after releasing a DVD I get 
three complaints of the same boot failures the first day. I then assume 
to have run into a widespread problem, assume 50 times more people 
affected, create a workaround and ... end up with seven downloads even 
after widely propagating the fix.

So my opinion is: Leave this strange interaction uninvestigated, remind 
users to force a sort order that moves all isolinux related files to low 
LBAs when building ISOs and move on, it is not worth the time. I will 
gladly write a section on the issue for the xorriso man pages (and the 
syslinux wiki) but we should not go any further as long as the problem 
does not occur with boot images located lower than 65535.

Regards,
Mattias

PS: Thomas, might I call you during the next days? POTS style?

-- 
Mattias Schlenker - Redaktion + EDV-Beratung + Linux-CD/DVD-Konzepte
August-Bebel-Str. 74 - 04275 LEIPZIG - GERMANY

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