s390/tools: handle rela R_390_GOTPCDBL/R_390_GOTOFF64

lkp test robot reported unhandled relocation type: R_390_GOTPCDBL, when
kernel is built with -fno-PIE. relocs tool reads vmlinux and handles
absolute relocations. PC relative relocs doesn't need adjustment.

Also, the R_390_GOTPCDBL/R_390_GOTOFF64 relocations are present
currently only when KASAN is enabled.

The following program can create a R_390_GOTPCDBL/R_390_GOTOFF64 reloc
(with fPIE/fPIC).

void funcb(int *b) {
*b = *b + 100;
}

void gen_gotoff(void)
{
int b = 10;
funcb (&b);
}

gcc -c sample.c -fPIC -fsanitize=kernel-address --param asan-stack=1

The above example (built with -fPIC) was linked to one of the
built-in.a (built with -fno-PIE) and checked for correctness with kaslr
enabled. Both the relocs turns out relative and can be skipped.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202402221404.T2TGs8El-lkp@intel.com/
Fixes: 55dc65b46023 ("s390: add relocs tool")
Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

s390: add relocs tool

This 'relocs' tool is copied from the x86 version, ported for s390, and
greatly simplified to remove unnecessary features.

It reads vmlinux and outputs assembly to create a .vmlinux.relocs_64
section which contains the offsets of all R_390_64 relocations which
apply to allocatable sections.

Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Link: https://lore.kernel.org/r/20240219132734.22881-3-sumanthk@linux.ibm.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>