[syslinux] Support for 4kb disks

H. Peter Anvin hpa at zytor.com
Mon Jul 30 07:17:22 PDT 2012

Partition tables are invalid when moving disk sizes anyway.  As far as removing legacy int13 support that is a non-option, although it probably is not necessary for those to work with larger sector sizes.

Frediano Ziglio <frediano.ziglio at citrix.com> wrote:

>On Wed, 2012-07-18 at 18:59 -0700, H. Peter Anvin wrote:
>> On 07/17/2012 01:37 AM, Frediano Ziglio wrote:
>> >
>> > 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
>> > 4kb.
>> >
>> Support for non-512-byte logical sectors is sparse since such support
>> actual systems is scant to nonexistent.  Most of the pieces are there
>> but as you have noticed there are bits still missing.
>> 	-hpa
>I finally got a repro using Qemu and patched SeaBIOS (just changed the
>check in src/blockcmd.c for DISK_SECTOR_SIZE adding 4096).
>After some though I think there are 2 way to make it work:
>1- patch extlinux installer in order to detect and use sector > 512
>2- make extlinux code assume that sectors specified are 512 but handle
>case where BIOS use bigger sizes
>1 make simpler extlinux code (probably code is already there) but it
>could be a problem if a user wants to switch the disk from 512 to 4096
>(this can happen changing jumpers on disk or firmware on some disk
>2 however require more code on extlinux (it's hard to make it works
>using 512 bytes).
>I'd vote for 2 and I think there are some options to avoid the 512
>- as sectors are bigger mbr code load more code, ext2/3/4 let us 1024
>bytes so we can use entire 1kb, just check on first 512 bytes we can
>entire kb
>- remove old floppy and no int13x code and use only int13x.
>In this case I would vote for first.
>Any suggestion?
>  Frediano

Sent from my mobile phone. Please excuse brevity and lack of formatting.

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