Re: [PATCH v3 0/2] Fix several mix up between octets and bytes in ELF program headers

[Christian Eggers <ceggers@gmx.de>]

> > and st_value?
>
> debugging through gas showed that struct elf_internal_sym::st_value is set
> from struct bfd_symbol::value [2] which in turn is set from struct
> expressionS::X_add_number [3].
>
> For sections like .text, all these values are in *bytes*. For sections which
> have SEC_ELF_OCTETS set (like .debug_info), there exists only the section
> symbols which have a value of 0. In absence of of "real" symbols inside
> these
> sections, I cannot say whether st_value can also be in octets.
> ...
> [2] bfd/elf.c:8139/8192
> [3] gas/write.c:2311/2410

elf_internal_sym::st_value has the following users:
- _bfd_elf_rel_local_sym():
  + Parameter "added" is sometimes octets, sometimes bytes.
    * Only used for architectures where this doesn't matter
  + _bfd_merged_section_offset() deals with octets, not bytes
  + result should be kept in bytes
- _bfd_elf_rela_local_sym(): Needs one conversion
- adjust_eh_frame_local_symbols():
  + delta = offset_adjust (sym->st_value, sec)
    * offset_adjust() uses octets/bytes inconsistently, needs fixes
      - eh_cie_fde::offset should be kept in octets
    * offset_adjust() should better return bytes
- asymbol_from_plugin_symbol(): No change?
- bfd_elf_final_link(): Needs 4 conversions.
- bfd_elf_print_symbol(): Only printf, may be kept as it is
- elf_slurp_symbol_table(): Copies to bfd_symbol::value, needs conversion
- elf_swap_symbol_in/out(): No change
- elf_common_parse():
  ...
  align = parse_align (is_local);
  ...
  S_SET_ALIGN (symbolP, align);
  +-- st_value = align ???   <--- why? But needs conversion
- elf_link_add_object_symbols(): More complicated!
  + bfd_vma value = isym->st_value  <-- octets
    ...
    value = isym->st_size;          <-- octets
    ...
    value -= sec->vma;              <-- bytes, needs conversion to octets
    ...
    (*bed->elf_add_symbol_hook) (..., &value))  <-- ???
    ...
    _bfd_elf_merge_symbol (..., &value, ...)    <-- octets
    ...
    _bfd_generic_link_add_one_symbol(..., value, ...)  <-- mixed ???
    ...
    _bfd_elf_add_default_symbol (..., value, ...): _bfd_elf_merge_symbol() <-- octets

  + align = bfd_log2 (isym->st_value);          <-- needs conversion to bytes
  + common_align = bfd_log2 (isym->st_value);   <-- needs conversion to bytes
- elf_link_input_bfd(): Needs 7 conversions
- elf_link_output_extsym(): Needs 4 conversions
- elf_output_implib(): Needs 1 conversion
- elf_s_get_align(): S_GET_ALIGN() <-- ???
- elf_s_set_align(): S_SET_ALIGN() <-- ???
- ldelf_ctf_symbols_iter_cb(): Copies to ctf_link_sym_t::st_value <-- no change
- s_mri_common():
  + align = get_absolute_expression ();
    ...
    S_SET_ALIGN (sym, align);   <-- conversion from bytes to octets

- set_symbol_value(): Needs one conversion
- swap_out_syms(): Needs two conversion


Conclusion: Conversion of elf_internal_sym::st_value from bytes to octets looks
possible, but may discover some currently undefined behavior. Simply converting
everything from bytes to octets in elf_swap_symbol_in/out() could be a shortcut
as currently all non-zero symbol values are in bytes. But doing so would be
inconsistent to my proposed change for r_offset and r_addend, so I would try
the "hard" way.

At next I will have a look at DWARF2 debug information.

Regards
Christian