[Bug ld/27282] New: ld: Should SHF_GNU_RETAIN/STT_GNU_IFUNC/STB_GNU_UNIQUE work for ELFOSABI_NONE object files?

[i at maskray dot me]

https://sourceware.org/bugzilla/show_bug.cgi?id=27282

            Bug ID: 27282
           Summary: ld: Should SHF_GNU_RETAIN/STT_GNU_IFUNC/STB_GNU_UNIQUE
                    work for ELFOSABI_NONE object files?
           Product: binutils
           Version: unspecified
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: ld
          Assignee: unassigned at sourceware dot org
          Reporter: i at maskray dot me
  Target Milestone: ---

ld -m elf_x86_64  recognizes semantics of OS-specific
STT_GNU_IFUNC/STB_GNU_UNIQUE in ELFOSABI_NONE object files.

  LLVM integrated assembler as of 12.0.0 does not set ELFOSABI_GNU if you use
@gnu_indirect_function/@gnu_unique_object.

  Question: how do GNU as set OSABI for STT_GNU_IFUNC/STB_GNU_UNIQUE on
FreeBSD? Is the behavior host platform dependent? 

However, ld -m elf_x86_64  does not recognize SHF_GNU_RETAIN in ELFOSABI_NONE
object files.

So these section/symbol properties have some inconsistency.
I can see two choices.


1. (Current behavior)
Ignore semantics of SHF_GNU_RETAIN in ELFOSABI_NONE object files.
If we want to make rules consistent, we should do this for
STT_GNU_IFUNC/STB_GNU_UNIQUE,
but it would break all the object files produced by LLVM integrated assembler.

2.
Recognize the semantics of SHF_GNU_RETAIN if the ld configuration & options
indicate Linux target (e.g. ld -m elf_x86_64 on Linux),
regardless of EI_OSABI in object files.
This choice gives discretion to the linker.

I think the only downside is that readelf -S does not display 'R' for
SHF_GNU_RETAIN,
like readelf -s doesn't show IFUNC for LLVM integrated assembler assembled
object files today.

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