[Etherboot-developers] Re: Dynamic relocation....

[Jeremy J. <je...@co...>]

I'd like to learn how you are doing this... perhaps I can have a
peek at your program?

It's just a test case, a Linux usermode program, to be using brk()?

Have you also considered using segment registers on Intel?

Jeremy

----- Original Message -----
From: "Eric W. Biederman" <ebi...@ln...>
To: "LinuxBIOS" <lin...@la...>; "Etherboot Developers"
<eth...@li...>
Sent: Saturday, April 13, 2002 1:41 AM
Subject: Dynamic relocation....


>
> In removing address conflicts in the process of booting, I keep
> wanting to copy the bootloader around, or relocate it in other ways.
>
> So today I sat down and played with the techniques ld.so uses
> to make itself position indpendent.  I took the necessary bits
> out of ld.so stripped them down and came up with a binary with a 2308
> byte footprint (bss included).
>
> All the 2308 byte binary does is call brk to get some more memory
> and then copy itself there, and then it restarts itself.
>
> And the code isn't to painful to write or maintain.  For another 300
> bytes I can add in printf so I can see what I'm doing.
>
> Holler if you want my test program, but generating a shared object
> that can relocate it self definitely works.
>
> I will probably figure out how to deploy this first in memtest86
> as it will cut the program size in half (because it won't have to
> double compile it's code), and make it more flexible.
>
> Oh yeah, and the active code size is for the relocate is just under
> 300 lines of code.  So this is small stuff that is fairly easy to deal
> with.
>
> A linker that does symbol lookup is still spooky but for relocation
> I'm pretty much convinced this is the way to go.
>
> Eric
>