Re: ARM kernel module supported reloc types

[Matt Thomas <matt%3am-software.com@localhost>]

On Dec 18, 2008, at 10:44 PM, Rafal Boni wrote:

> On Thu, Dec 18, 2008 at 09:35:02PM -0800, Matt Thomas wrote:
> > Yes.  PC24 is not appropriate in dynamic shared library loading but
> > since kernel modules are simple .o files, it is appropriate.
>
> Ok, so the next hole I fall into is symbols being too far for the PC24
> reloc to resolve (printf in the example modules), and a crash related
> to the auto-loading of the compat module.

If the branch is too far, you need to "trampolines" at the end of
the text section which, for each symbol, will do

symbol: ldr pc, . - 4
        .word   <absaddr of symbol>

printf: 0xe51ff004
        <printf addr>

> The second one I haven't dug into very much (it gave me a reason to  
> give
> up for the night), but the first is interesting -- in the old LKM  
> frame-
> work, the lkmtramp.awk scripts generated trampoline code for all  
> targets
> of PC24 relocs... do we have an equivalent for the new modules?   
> Where is
> this supposed to happen in the new world order?

no need, we can have the loader do the above instead.