If there exist multiple sections with the same name (which can happen when
using the --unique option with ld, which will be used to keep multiple
(per-object) .parainstructions and .altinstructions sections separate),
find_section_by_name() will only return the first section name match, which
leads to incorrect base section assignments for rela sections. Fix this by
using the sh_info field of the rela section to find its base section
instead, which contains the index of the section to which the relocation
applies.
Make sure sym->sec is not NULL before checking for its rela section
(sym->sec->rela). This fixes a case where an object may have STT_FUNC
symbols whose the sections (sym->sec) were not selected for inclusion (or
are located in another object) and hence these symbols do not have sym->sec
set. This corner case only recently popped up after reusing kpatch_elf_open()
on objects that have been outputted by create-diff-object (and these
objects only contain the necessary sections needed for the patch module).
This will also automatically exclude livepatch symbols from the check,
because they do not have sections associated with them (i.e., sym->sec is
NULL). We do not have to check for fentry calls for klp (SHN_LIVEPATCH)
symbols, because [1] they do not have sections associated with them, [2]
they are not the target functions to be patched, and [3] they are
technically just placeholder symbols for symbol resolution in livepatch.
Move functions kpatch_reindex_elements() and kpatch_rebuild_rela_section_data()
from create-diff-object.c to kpatch-elf.c. These functions will be used
to rebuild kpatch elf data in create-klp-module and create-kpatch-module,
i.e. during the second "phase" of kpatch-build.
Since is_bundleable() is only called once by kpatch_create_symbol_list(),
and no other kpatch-build tool will need to call this function, we can
simply make it static and local to kpatch-elf.c
Introduce a common kpatch elf api by moving all functions and struct
declarations related to manipulating kpatch_elf objects from
create-diff-object to kpatch-elf.{h,c}. Move logging macros to a separate
file log.h, and have kpatch-elf.h include it. These changes will generalize
the kpatch-elf and logging api and make it available to other kpatch-build
tools.
