Syslinux - Dec 2004 - Good, bad and ugly

Okay, after looking at the USB stuff it's getting pretty clear that the 
few BIOS vendors that are left is going straight to hell, and that with 
any new media they introduce they are going to find new ways to screw up 
20-year-old interfaces.  It seems pretty necessary to go and support 
EBIOS at this time.

The problem is that it takes a *very* space-constrained boot sector and 
adds over 100 bytes of code; over a 25% space increase.  Clearly not 
possible.  Thus, I'm looking at what options there are.

Clearly, discontinuing CBIOS support is not an option either (as much as 
I'd like to), so that's right out.  Nor is it possible to decide at 
install time, since you might be booting in another machine.

The one thing that seems possible to go is the automatic search for 
LDLINUX.SYS.  The boot sector can hard-code the location of this file, 
or perhaps only the beginning of it.  This means the file cannot be 
moved, but it's already standard that a file with the System attribute 
set shouldn't be moved.  It also means it's no longer "just a
file"; it
will not be possible to copy it or write it with anything other than the 
syslinux installer, to the extent it ever was.

This might be complex to do in the Win32 installer, but there is always 
raw filesystem access to fall back upon.

So, that's the bad, and the ugly.  The good news is that this should 
make FAT32 support fall in quite naturally, which it most certainly 
isn't at the moment (because FAT32 changes the way the root directory 
works.)

So, anyway, I wanted everyone's opinion before I set out on what is a 
significant recoding project.  I do NOT expect to do this for 2.12, 
because I want to get those changes out there, but more likely I'll call 
that version 2.20.

	-hpa

H. Peter Anvin wrote:
>
> The one thing that seems possible to go is the automatic search for 
> LDLINUX.SYS.  The boot sector can hard-code the location of this file, 
> or perhaps only the beginning of it.  This means the file cannot be 
> moved, but it's already standard that a file with the System attribute 
> set shouldn't be moved.  It also means it's no longer "just a
file";
> it will not be possible to copy it or write it with anything other 
> than the syslinux installer, to the extent it ever was.

Is this not what grub does currently?  The address for the next piece of 
code is in the mbr and uses it to load the second stage loader - am I 
correct?

I believe MS/PC-DOS does the same thing - it looks for IO.SYS/IBMBIO.COM 
in the fat table, loads it, then executes it.

I'll vote for the last method - very similiar to the way DOS loads - and 
your right - many defragmentation programs don't move files that have 
the system bit on them.

Quinn