[syslinux] VirtualBox 4.1.x can reproduce bug 45

[Ady]

> Short summary:
> I think bug #45
>  http://bugzilla.syslinux.org/show_bug.cgi?id=45 
> "Regression in Syslinux 6.xx. Doesn't 'hand over' to linux kernel"
> can be reproduced using VirtualBox 4.1.x while trying to boot a 
> relatively-newish Linux kernel.
> 
> Now, for more details...
> 
> Under VBox 4.1.x and using ISOLINUX 4.xx, a newish Linux kernel boots 
> correctly.
> 
> Under VBox 4.1.x and using ISOLINUX 6.xx, the same newish Linux 
> kernel fails to boot. This is the same exact system, except for the 
> version of Syslinux (ISOLINUX) used in the ISO image that is booting 
> the VM.
> 
> As mentioned in bug #45, the VM initially boots to Syslinux 6.xx, but 
> when trying to boot the Linux kernel, it fails to complete the boot 
> process.
> 
> Depending on the specific boot command (specific kernel, initrd...), 
> the screen might show some initial row(s), similar to:
> Loading kernel... OK
> Loading initrd... OK
> 
> and then it just hangs there. Or, it might clear the screen and a 
> cursor might show up at the upper-left area of the screen, and then 
> just hangs.
> 
> Just to be sure, I have waited several minutes before closing the VM. 
> The same kernels are able to complete the boot process using Syslinux 
> 4.xx without problems.
> 
> Although the exact behavior seen on screen might vary, the main 
> behavior is the same: Syslinux 4.xx works, 6.xx fails.
> 
> Now, updating VBox to version 4.2.x, the same VM can successfully 
> boot, whether with Syslinux 4.xx or with 6.xx. This seems to suggest 
> that there is some bug in VBox 4.1.x. But, whichever the bug in VBox 
> 4.1.x, the behavior reflects real systems, as exposed by reports such 
> as those in bug #45.
> 
> For testing this behavior under VBox 4.1.x, I have tried recent 
> releases of Gparted Live, Clonezilla Live, ArchLinux... I used the 
> original ISO images (which are already using ISOLINUX 6.xx), and I 
> also re-built the images with Syslinux (ISOLINUX) 4.xx.
> 
> Perhaps testing Syslinux 6.xx under VBox 4.1.x might help solve bug 
> #45?
> 
> TIA,
> Ady.
 
I followed hpa's instructions (given at #syslinux, on syslinux 
6.03pre3):

1_ Add:
 -DDEBUG=1 
 -DCORE_DEBUG=1
to mk/devel.mk.

2_ Build.
I used 'make bios'

3_ Test with:
debug.c32 -e bios_boot_linux
debug.c32 -e syslinux_do_shuffle
debug.c32 -e syslinux_dump_memmap
debug.c32 -e syslinux_dump_movelist

(I actually used debug.c32 -e <func1> , <func2> , ... I am typing it 
as 4 individual lines here just for clarity.)

4_ Launch the kernel (which fails as described in bug 45).

I am attaching the console output. Hopefully it helps with bug 45.

TIA,
Ady.
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     Date:  28 Feb 2014, 3:21
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