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

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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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 ?

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

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

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
> 
> _______________________________________________
> Syslinux mailing list
> Submissions to Syslinux at zytor.com
> Unsubscribe or set options at:
> http://www.zytor.com/mailman/listinfo/syslinux
> Please do not send private replies to mailing list traffic.
> 
> 

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

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