[syslinux] Sysinux 6 will not boot ISOs on BIOS (i.e. pre-UEFI) systems

Gerardo Exequiel Pozzi vmlinuz386 at yahoo.com.ar
Mon Nov 25 13:27:04 PST 2013


On 11/25/2013 04:39 PM, Thomas Schmitt wrote:
> Hi,
> 
> Gerardo Exequiel Pozzi wrote:
>> Looks like there is something beyond LBA 65535 (As Mattias confirmed)
> 
> I wanted to ask him now, whether this was already with
> version 6. 
> But meanwhile he reported that it was 5.
> 
> 
>> I can push isolinux.bin (4.07) to a really high LBA address and boot
>> without any issue. (Load LBA: 2048034 (0x001f4022)) ~4G
> 
> This is riddling, given the statement of hpa that the
> boot images are identical up to the point where Carl's
> boot procedure fails.
> There seems to be some loophole in the identity.
> 
> Another possibility could be that not the whole address
> range above 128 MB is poisonous, but only particular
> intervals.
> Gerardo: did you really try 4.07 with exactly the same boot
> image LBA as 6.02 ?

Yes, same LBA offset for isolinux.bin for 4.07 and 6.02.

Indeed, I made I small modification to set and LBA offset for isolinux.bin

----
#!/bin/sh

# LBA > 33, set LBA for isolinux.bin
LBA=34

mkdir -p /tmp/test/isolinux
cp ~/isolinux-6.02.bin /tmp/test/isolinux/isolinux.bin
#cp ~/isolinux-4.07.bin /tmp/test/isolinux/isolinux.bin
truncate -s $(((LBA-34)*2048)) /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 \
        -output /tmp/test.iso \
        /tmp/test/
dumpet -i /tmp/test.iso
cdrecord -v -dev=5,0,0 -dao /tmp/test.iso
----

> 
> I fail to imagine a way how the boot image size could make
> a high LBA poisonous. But well, if the firmware is mad ...

Firmware has more mysteries than the Universe!

> 
> hpa: How much can we cut off a isolinux.bin so that the
> early boot stage up to the problem still should work ?
> If the first 12 blocks suffice, then Gerardo could make
> a test with the same size as in SYSLINUX 4 (with expected
> failure at some later stage).
> 
> 
> Have a nice day :)
> 
> Thomas
> 
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-- 
Gerardo Exequiel Pozzi
\cos^2\alpha + \sin^2\alpha = 1

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