[syslinux] Modify memdisk to mask/overlay start of hard drive

[Erik Jensen]

I have a somewhat unique problem I am trying to solve that requires me
to temporarily replace the first 63s of the main hard drive and boot
the result. Basically, I am hoping it is possible to modify memdisk to
serve requests for the first 63 sectors from a ram disk and pass other
requests through to the hard drive. There will never be a read
spanning the two, so I don't need it to be able to handle that
complexity. Also, it will alway be masking the first 63s of the first
hard drive, so it doesn't need to be configurable.

How complicated would it be to modify memdisk to support this? Any
advice on where to make the change? I do have some programming
experience, but none in assembly.

Thanks.