These are useless because they can't match any address. In fact,
worse than useless because the .eh_frame_hdr lookup table matching
addresses to FDEs does not contain information about the FDE range.
The table is sorted by address; Range is inferred by the address
delta from one entry to the next. So if a zero address range FDE is
followed by a normal non-zero range FDE for the same address,
everything is good. However, the qsort could just as easily sort the
FDEs in the other order, in which case the normal FDE would
effectively be seen to have a zero range.
bfd/
PR 17447
* elf-bfd.h (struct eh_cie_fde): Comment re NULL u.fde.cie_inf.
* elf-eh-frame.c (_bfd_elf_parse_eh_frame): Mark zero address
range FDEs for discarding.
(vma_compare): Sort on range after address.
(_bfd_elf_gc_mark_fdes): Test for NULL u.fde.cie_inf.
(_bfd_elf_discard_section_eh_frame): Likewise. Write "FDE" in
error message rather than "fde".
(_bfd_elf_write_section_eh_frame_hdr): Write "PC" and "FDE" in
error message.
ld/testsuite/
* ld-elf/eh1.s: Don't create FDEs with zero address ranges.
* ld-elf/eh3.s: Likewise.
* ld-elf/eh1.d, * ld-elf/eh2.d, * ld-elf/eh3.d: Adjust.
* ld-mips-elf/eh-frame1-n32.d: Warning match update.
* ld-mips-elf/eh-frame1-n64.d: Likewise.
* ld-mips-elf/eh-frame2-n32.d: Likewise.
* ld-mips-elf/eh-frame2-n64.d: Likewise.
* elf-eh-frame.c (make_pc_relative): New function.
(_bfd_elf_write_section_eh_frame): Use it.
ld/testsuite/
* ld-mips-elf/eh-frame1-n32.d: Expect PC-relative encodings
to include DW_EH_PE_sdata4.
* ld-mips-elf/eh-frame2-n32.d: Likewise.
* ld-mips-elf/eh-frame1-n64.d: Expect PC-relative encodings
to include DW_EH_PE_sdata8.
* ld-mips-elf/eh-frame2-n64.d: Likewise.
* ld-mips-elf/eh-frame1-n32.d: Expect a warning about .eh_frame_hdr.
Remove duplicate CIEs. Adjust relocation addresses and .eh_frame
offsets accordingly. Do not allow there to be any trailing
R_MIPS_NONE relocations.
* ld-mips-elf/eh-frame1-n64.d: Likewise.
* ld-mips-elf/eh-frame2-n32.d: Likewise.
* ld-mips-elf/eh-frame2-n64.d: Likewise.
add_fde_encoding. Remove need_relative.
* elf-eh-frame.c (extra_augmentation_string_bytes)
(extra_augmentation_data_bytes, size_of_output_cie_fde): New functions.
(_bfd_elf_discard_section_eh_frame): Consider changing the FDE encoding
in cases where the CIE has no existing 'R' augmentation. Use
size_of_output_cie_fde when assigning offsets. Use the final offset
as the new section size.
(_bfd_elf_eh_frame_section_offset): Remove need_relative handling.
Account for any extra augmentation bytes in the returned offset.
(_bfd_elf_write_section_eh_frame): Rework so that the entries are
moved before being modified. Pad growing entries with DW_CFA_nops.
Add 'z' and 'R' augmentations as directed by add_augmentation_size
and add_fde_encoding.
Alan Modra
Maciej W. Rozycki
Richard Sandiford
Nick Clifton