[syslinux] Support for 4kb disks

Frediano Ziglio frediano.ziglio at citrix.com
Tue Jul 17 01:37:16 PDT 2012

On Mon, 2012-07-16 at 18:29 -0400, Gene Cumm wrote:
> On Mon, Jul 16, 2012 at 6:11 AM, Frediano Ziglio
> <frediano.ziglio at citrix.com> wrote:
> > Hi,
> >   I'm trying to get syslinux (extlinux actually) work with 4kb disks.
> You were right.  SYSLINUX.  extlinux is just the installer (as of
> v4.00).  Could you be more precise on what version and the source of
> the binaries (ie, did you use the ones in the binary/source archive
> without building)?  4.05 might support this.

I tried 4.05 and 4.02 but both fails to boot. Looking at disk dumps GPT
structure is correct (at sector 1, so at 4kb start gpt with 4b sectors
pointer, gtpmbr can load boot sector although I think I was just lucky
cause gtpmbr assume sectors are 512 bytes but finding boot partition on
first sector part is not a problem).

Using hexdump/disassemble I noted that sector size in boot sector is 512
and first sector to load is outside the ext partition (probably it
should be divided by 8).

> > I got a bios with 4kb support but seems that extlinux does not work at
> > all. In extlinux/main.c SECTOR_SIZE and SECTOR_SHIFT are constants to
> > 512 bytes and also there are a lot of checks in different places (like
> > in syslinux_check_bootsect).
> >
> > Currently I'm trying it to work using GPT and an ext3 partition.
> >
> > Anybody is working on similar issue or has some advice?
> >
> > Is there a way to emulate 4kb bios using any virtual environment?
> Do you mean using a VM of sorts or something else?

It's a physical machine with a beta firmware on it. I wrote a small
program to read/write two sectors and I can confirm that each sector is


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