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

[H. Peter Anvin]

On 11/25/2013 06:32 PM, H. Peter Anvin wrote:
> On 11/25/2013 04:12 PM, Gerardo Exequiel Pozzi wrote:
>>
>> I made some more and more experiments beyond LBA 65535
>>
>> Works: * isolinux-4.07.bin (size 24574) * isolinux-5.00.bin (size
>> 34816)
>>
>> Does not work: * isolinux-5.01.bin (size 34816) * isolinux-5.10.bin
>> (size 36864) * isolinux-6.00.bin (size 38912) * isolinux-6.02.bin
>> (size 43008)
>>
>> * I just tested exactly at LBA 65535 (works all versions) and LBA
>> 65536 (fails all versions > 5.00).
>>
> 
> What the heck... there are just about zero plausible differences
> between 5.00 and 5.01.
> 
> I'm wondering if 17a36e2c91706512e6c425222c9a9a451d9db854 could
> plausibly have anything to do with this, since that seems to be the
> only possible patch that might affect isolinux.  Is there any way you
> could try 5.01-pre1 and 5.01-pre2?  If -pre1 works and -pre2 doesn't,
> it is likely that the problem lies in that commit.
> 

If you have the ability to rebuild Syslinux from source, perhaps you
could try the following patch?

	-hpa


-------------- next part --------------
diff --git a/core/isolinux.asm b/core/isolinux.asm
index bd4e9556922d..c4db4133e274 100644
--- a/core/isolinux.asm
+++ b/core/isolinux.asm
@@ -420,7 +420,7 @@ MaxLMA		equ 384*1024		; Reasonable limit (384K)
 		call getlinsec
 		pop eax
 		pop cx
-		mov dx,cx
+		movzx edx,cx
 		pop bp
 		pop bx