bFLT relocation problems when running busybox/uclibc

[David McCullough]

Jivin Rick Garcia lays it down ...
> David McCullough wrote:
> >Jivin Rick Garcia lays it down ...
> >>    I'm attempting to run busybox compiled against uClibc in bFLT format 
> >>- busybox starts up, the kernel does the relocation, but it appears to 
> >>be incomplete.   During debug, I can observe it performing a few hundred 
> >>relocations, but I can identify more than a few places where it's using 
> >>an invalid non-relocated address, and these all seem to be internal 
> >>uClibc symbols.  As far as I can tell, all the busybox symbols are 
> >>correctly relocated.
> >>    Are there any flags that need to be passed to the uClibc build to 
> >>get it to work with flat binary format?  I'm using the -Wl,-elf2flt when 
> >>building busybox, but I built uClibc without any extra flags - my 
> >>understanding was that they wouldn't be necessary when building a 
> >>library like uClibc - I can't even identify a point in the build where 
> >>they might be used.  Anyone have any ideas what could be causing this?
> >
> >It depends on how you have built your uClibc I guess.  Compare the build
> >lines for each and check for differing "-m..." options.
> 
>     The only -m.. option is -msep_data.

Then both the lib and the app need to be built with that option.

> >What kernel/arch/compilers are you using ?
> 
>     It's an m68k clone - kernel is uClinux 2.4.(30?), and the compiler 
> is 3.4.4
> 
> >Also it's probably better to ask on the uClinux-dev list :-)
> 
>     Will do :)
> 
>     One question - are you aware of any way to verify that elf2flt has 
> relocated all the relevant symbols in an image?  I know there isn't 
> exactly a plethora of utilities for examining the bFLT format right now, 
> but I need to find a way to check this.
>     Right now, the flthdr is telling me that there are 322 relocations 

I think elf2flt has a -v:

	-Wl,-elf2flt=-v

> - the make output logs and some quick checks I slapped into the kernel 
> agree, so I'll concede that that much is working.  But 322 relocations 
> for a program like busybox?  Every example I've seen online has had 
> something on the order of 3000 relocations.  I have a minimal config 
> going, but still... that's not a lot of symbols.

msep-data reduces the number of relocations to just the data segment and
the GOT.  Don't have one to compare at the moment though,

Cheers,
Davidm


-- 
David McCullough,  david_mccullough at securecomputing.com,   Ph:+61 734352815
Secure Computing - SnapGear  http://www.uCdot.org http://www.cyberguard.com