Hi Tong,
On Thu, 25 Sep 2014 22:53:22 -0700, Tong Shen wrote:
>>>>>> +/**
>>>>>> + * is_non_relocatable_dyn - check if ELF file is ET_DYN, but not
>>>>>> relocatable
>>>>>> + * @ehdr: ELF header of the ELF file
>>>>>> + * @shdr: a section header in the ELF file
>>>>>> + *
>>>>>> + * For ELF files with type ET_EXEC and ET_REL, we adjust symbol
>>>>>> addresses in
>>>>>> + * symbol table in dso__load_sym() so that later we can always locate
>>>>>> symbols
>>>>>> + * by sym.st_value + map_address_of_ELF_file.
>>>>>> + *
>>>>>> + * But ELF files with type ET_DYN may need adjusting as well, if they
>>>>>> are
>>>>>> + * not relocatable. There's no standard way to tell if an ELF file with
>>>>>> type
>>>>>> + * ET_DYN is relocatable. One possible way to do that is checking if
>>>>>> + * sh_addr == sh_offset for .text section.
>>>>>> + */
>>>>>> +static bool is_non_relocatable_dyn(GElf_Ehdr *ehdr, GElf_Shdr *shdr,
>>>>>> + Elf_Data *secstrs) {
>>>>>> + return ehdr->e_type == ET_DYN &&
>>>>>> + elf_sec__is_text(shdr, secstrs) &&
>>>>>> + shdr->sh_offset != shdr->sh_addr;
>>>>>> +}
>>>>>> +
>>>>>> int dso__load_sym(struct dso *dso, struct map *map,
>>>>>> struct symsrc *syms_ss, struct symsrc *runtime_ss,
>>>>>> symbol_filter_t filter, int kmodule)
>>>>>> @@ -914,8 +935,9 @@ int dso__load_sym(struct dso *dso, struct map *map,
>>>>>> goto new_symbol;
>>>>>> }
>>>>>>
>>>>>> - if ((used_opd && runtime_ss->adjust_symbols)
>>>>>> - || (!used_opd && syms_ss->adjust_symbols))
>>>>>> {
>>>>>> + if ((used_opd && runtime_ss->adjust_symbols) ||
>>>>>> + (!used_opd && syms_ss->adjust_symbols) ||
>>>>>> + is_non_relocatable_dyn(&ehdr, &shdr, secstrs)) {
>>>>>> pr_debug4("%s: adjusting symbol: st_value: %#"
>>>>>> PRIx64 " "
>>>>>> "sh_addr: %#" PRIx64 " sh_offset: %#"
>>>>>> PRIx64 "\n", __func__,
>>>>>> (u64)sym.st_value, (u64)shdr.sh_addr,
Hmm.. IIUC for normal dso (ET_DYN), shdr->offset == shdr->sh_addr for
text section right? And we always adjust ET_EXEC and ET_REL.. What
about always trying to adjust symbol address then? We may precalculate
adjust offset and subtracting it from symbol values. And the offset of
0 effectively means no adjust. This way we can simplify the logic IMHO.
Thanks,
Namhyung
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