[binutils-gdb] PR29355, ld segfaults with -r/-q and custom-named section .rela*

[binutils-gdb] PR29355, ld segfaults with -r/-q and custom-named section .rela*

[Alan Modra]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=35c5dcc666082f0edf6dd559e46b98d0e7986a2e

commit 35c5dcc666082f0edf6dd559e46b98d0e7986a2e
Author: Alan Modra <amodra@gmail.com>
Date:   Tue Jul 12 10:51:52 2022 +0930

    PR29355, ld segfaults with -r/-q and custom-named section .rela*
    
    The bug testcase uses an output section named .rel or .rela which has
    input .data sections mapped to it.  The input .data section has
    relocations.  When counting output relocations SHT_REL and SHT_RELA
    section reloc_count is ignored, with the justification that reloc
    sections themselves can't have relocations and some backends use
    reloc_count in reloc sections.  However, the test wrongly used the
    output section type (which normally would match input section type).
    Fix that.  Note that it is arguably wrong for ld to leave the output
    .rel/.rela section type as SHT_REL/SHT_RELA when non-empty non-reloc
    sections are written to it, but I'm not going to change that since it
    might be useful to hand-craft relocs in a data section that is then
    written to a SHT_REL/SHT_RELA output section.
    
            PR 29355
            * elflink.c (bfd_elf_final_link): Use input section type rather
            than output section type to determine whether to exclude using
            reloc_count from that section.

Diff:
---
 bfd/elflink.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/bfd/elflink.c b/bfd/elflink.c
index dcafac32800..2b1450fa4e1 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -12413,8 +12413,10 @@ bfd_elf_final_link (bfd *abfd, struct bfd_link_info *info)
 		      && elf_symtab_shndx_list (sec->owner) != NULL)
 		    max_sym_shndx_count = sym_count;
 
-		  if (esdo->this_hdr.sh_type == SHT_REL
-		      || esdo->this_hdr.sh_type == SHT_RELA)
+		  esdi = elf_section_data (sec);
+
+		  if (esdi->this_hdr.sh_type == SHT_REL
+		      || esdi->this_hdr.sh_type == SHT_RELA)
 		    /* Some backends use reloc_count in relocation sections
 		       to count particular types of relocs.  Of course,
 		       reloc sections themselves can't have relocations.  */
@@ -12432,8 +12434,6 @@ bfd_elf_final_link (bfd *abfd, struct bfd_link_info *info)
 		  else if (bed->elf_backend_count_relocs)
 		    reloc_count = (*bed->elf_backend_count_relocs) (info, sec);
 
-		  esdi = elf_section_data (sec);
-
 		  if ((sec->flags & SEC_RELOC) != 0)
 		    {
 		      size_t ext_size = 0;