x86_64 module loader reloc problem

x86_64 module loader reloc problem

[Jason Baietto]

Using test8 I'm only able to load kernel modules on x86_64 systems if I
comment out the overflow check for R_X86_64_32 relocation entries in
arch/x64_64/kernel/module.c.

With the check in place I get errors like this:

   overflow in relocation type 10 val ffffff0000426b88" errors
   `test' likely not compiled with -mcmodel=kernel
   insmod: error inserting 'test.ko': -1 Invalid module format

Yes, I'm using -mcmodel=kernel.  I'm also using module-init-tools
0.9.15-pre2.  Once loaded, the modules appear to be working properly,
but it wouldn't surprise me if a time bomb was lurking there.

What am I doing wrong?  Compiler used for both kernel and modules is gcc
(GCC) 3.2.3 20030502 (Red Hat Linux 3.2.3-20).

Note that in my linked test module, objdump shows 632 R_X86_64_32 reloc
entries and only 18 R_X86_64_64 reloc entries.

Take care,
Jason

Re: x86_64 module loader reloc problem

[Andi Kleen]

Jason Baietto <jason.baietto@ccur.com> writes:

> Note that in my linked test module, objdump shows 632 R_X86_64_32 reloc
> entries and only 18 R_X86_64_64 reloc entries.

X86_64_32 is wrong for -mcmodel=kernel. It should be X86_64_32S.
Either you didn't compile with -mcmodel=kernel or your compiler or binutils 
are buggy.

-Andi