Some basic questions from a userland jerk about kernel binary format

Hi all,=20

I hope my topic is appropriate for this list, if not please point me=20
in the right direction.=20

I know the thing I want to achieve is strange as I could do the same=20
better by using the dynamic module loader.  Unfortunately I've got to=20
port an application from another OS and I'm currently not able to=20
change the inner workings too much.=20

What I want to achieve is to dynamically access arbitrary variables in=20
my kernel module by determining the offset of the variable's address=20
offline as an offest regarding a common base address within my=20
module.  To achieve that I need to know the following:=20

1. How many segments does a kernel module binary usually have? Is it=20
   the same as in userland, i.e. .bss, .data and .text? Or are there=20
   others or only a single one?=20

2. (How) can I instruct the linker to put a certain variable 'near'=20
   the beginning of each segment? This would become my base address,=20
   one for each segment.  I would use the dynamic loader to access=20
   this base address at runtime.  The most important prerequisite=20
   would be that this base address needs to be 'in front of' every=20
   application variable.=20

3. I want to use binutils/nm to compute the offset of my application=20
   variables in terms of their distance to the relevant base address.=20
   This can obviously change from revision to revision of my my=20
   module, which is ok.  Is that viable (I don't know the dynamic=20
   linker of the kernel)?=20

4. At runtime I want to compute my application variable's address by:=20

   real_adr =3D base address + offset=20

   Is that also ok?=20


TIA,=20

Andreas Ames=20

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