[syslinux] where to swap

Martin Str|mberg
Mon, 27 Mar 2017 06:21:58 -0000

On Sun, Mar 26, 2017 at 10:13:28PM +0200, Thomas Schmitt via Syslinux
wrote:
> Do all six fixed isohdp*.bin variations still fit into 432 bytes ?
>
> mbr/Makefile builds among other MBRs:
>   isohdpfx.bin isohdppx.bin isohdpfx_c.bin isohdppx_c.bin
>   isohdpfx_f.bin isohdppx_f.bin

Yes. I make my changes in my syslinux git clone. All of the above is
build from isohdpfx.S with different #defines active. Building them
runs a check with checksize.pl that fails if they go beyond what's
defined in checksize.pl.

That does not fail for me.


Thomas, if you're interested in the resulting assembly and/or
encodings (as you seems to analyse and change the binary code in the
resulting .bin files I assume you are) you should really clone the git
repo and build it. It's not very hard.

Then you can look at the resulting .lst files to see what values the
instructions turned into (except for values that are determined at
link time). Also you should immediately see the offset that you want
to patch instead of needing to search.

Another good command is "objdump -D -b binary -m i8086 -M
data16,addr16 isohdpfx.bin" if you want to see the assembly code of
something compiled for barebones 16-bit x86.


--
MartinS