[PATCH] ARM: MMUless Core: Fix insmod error - module relocation out of range

[Russell King - ARM Linux]

On Wed, Oct 03, 2012 at 10:25:09AM +0100, Catalin Marinas wrote:
> On 3 October 2012 04:43, Pratyush Anand <pratyush.anand at st.com> wrote:
> > From: Neha MAKHIJA <neha.makhija-ext at st.com>
> >
> > ARM supports 32Mb jump. Hence branch instruction has a limited range.
> >
> > For MMU systems, the module area is located just before the kernel memory
> > because this allows function calls to be linked directly without any indirect
> > branches.
> >
> > In case of MMU-less system, Module area is given whole of the DDR address
> > space.  Since, module_alloc() calls vmalloc(), the module area goes outside the
> > allowed jump range. Due to this insmod will not be able to load the modules
> > giving out of range relocation errors.
> >
> > Solution - Add the mlong-calls flags while compiling the modules. This tells
> > the compiler to perform function calls by first loading the address of the
> > function and then performing a subroutine function call on this register.
> 
> Do we need the module loader to handle additional relocations or they
> are all already handled?

I have explained this extensively when the 2.6 module loader came into
being.  It's not about additional relocations, it's about the addressible
range of the 'b' instruction.

Please search the archives for the explanation.