[syslinux] Syslinux Mem= greater than 4096M

[Paul Bolle]

On Sun, 2012-02-05 at 23:41 -0800, H. Peter Anvin wrote:
> On 02/04/2012 04:32 AM, Gene Cumm wrote:
> > 
> > LABEL less
> >     MENU LABEL Up to 64 GB System RAM
> >     COM32 /boot/linux.c32
> >     APPEND /boot/vmlinuz-3.1.10-b1 pci=nommconf vga=773 mem=4352M
> > initrd=/boot/initrd-3.1.10-b1.img
> > 
> > I'd guess this will give similar results but if you used mem=4097M it
> > will likely succeed.
> > 
> 
> This is probably a 32-bit wraparound problem in the Syslinux core.

0) When I had to look at what could cause this in syslinux I found this:
- core/runkernel.inc:657:         cmd_opt "mem=", opt_mem

- core/runkernel.inc:158:opt_mem:
                    :159:                call parseint_esdi

- core/getc.inc:407:parseint_esdi:
               [...]
               :412:              call parseint

- core/getc.inc:254:parseint:
               [...]
               :319:.isg:         shl ebx,10              ; * 2^30
               :320:.ism:         shl ebx,10              ; * 2^20
               :321:.isk:         shl ebx,10              ; * 2^10

1) So there should be a wraparound for (in this case) options of "4096M"
and higher.

2) Not sure if this can explain all effects mentioned in this thread so
far, though.


Paul Bolle