PR ld/21334: Always call `_bfd_elf_link_renumber_dynsyms' if required

Complement commit e17b0c351f0b ("MIPS/BFD: Respect the ELF gABI dynamic
symbol table sort requirement") and correct an inconsistency in dynamic
symbol accounting data causing an assertion failure in the MIPS backend:

ld: BFD (GNU Binutils) 2.28.51.20170330 assertion fail
../../binutils-gdb/bfd/elfxx-mips.c:3860

in the course of making a GOT entry in a static binary to satisfy a GOT
relocation present in input, due to the local dynamic symbol count not
having been established.

To do so let backends request `_bfd_elf_link_renumber_dynsyms' to be
always called, rather than where a dynamic binary is linked only, and
then make this request in the MIPS backend.

	bfd/
	PR ld/21334
	* elf-bfd.h (elf_backend_data): Add `always_renumber_dynsyms'
	member.
	* elfxx-target.h [!elf_backend_always_renumber_dynsyms]
	(elf_backend_always_renumber_dynsyms): Define.
	(elfNN_bed): Initialize `always_renumber_dynsyms' member.
	* elfxx-mips.h (elf_backend_always_renumber_dynsyms): Define.
	* elflink.c (bfd_elf_size_dynamic_sections): Also call
	`_bfd_elf_link_renumber_dynsyms' if the backend has requested
	it.
	(bfd_elf_size_dynsym_hash_dynstr): Likewise.

	ld/
	PR ld/21334
	* testsuite/ld-mips-elf/pr21334.dd: New test.
	* testsuite/ld-mips-elf/pr21334.gd: New test.
	* testsuite/ld-mips-elf/pr21334.ld: New test linker script.
	* testsuite/ld-mips-elf/pr21334.s: New test source.
	* testsuite/ld-mips-elf/mips-elf.exp: Run the new tests.

1 files changed, 23 insertions, 11 deletions

diff --git a/bfd/elflink.c b/bfd/elflink.c
index 05b1211..73af763 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -6460,7 +6460,11 @@ bfd_elf_size_dynamic_sections (bfd *output_bfd,
       elf_link_hash_traverse (elf_hash_table (info), elf_gc_sweep_symbol,
 			      &sweep_info);
 
-      if (elf_hash_table (info)->dynamic_sections_created)
+      /* We need to reassign dynsym indices now that symbols may have
+	 been removed.  See the call in `bfd_elf_size_dynsym_hash_dynstr'
+	 for the details of the conditions used here.  */
+      if (elf_hash_table (info)->dynamic_sections_created
+	  || bed->always_renumber_dynsyms)
 	_bfd_elf_link_renumber_dynsyms (output_bfd, info, &section_sym_count);
     }
 
@@ -6828,6 +6832,8 @@ bfd_boolean
 bfd_elf_size_dynsym_hash_dynstr (bfd *output_bfd, struct bfd_link_info *info)
 {
   const struct elf_backend_data *bed;
+  unsigned long section_sym_count;
+  bfd_size_type dynsymcount;
 
   if (!is_elf_hash_table (info->hash))
     return TRUE;
@@ -6835,24 +6841,30 @@ bfd_elf_size_dynsym_hash_dynstr (bfd *output_bfd, struct bfd_link_info *info)
   bed = get_elf_backend_data (output_bfd);
   (*bed->elf_backend_init_index_section) (output_bfd, info);
 
+  /* Assign dynsym indices.  In a shared library we generate a section
+     symbol for each output section, which come first.  Next come all
+     of the back-end allocated local dynamic syms, followed by the rest
+     of the global symbols.
+
+     This is usually not needed for static binaries, however backends
+     can request to always do it, e.g. the MIPS backend uses dynamic
+     symbol counts to lay out GOT, which will be produced in the
+     presence of GOT relocations even in static binaries (holding fixed
+     data in that case, to satisfy those relocations).  */
+
+  if (elf_hash_table (info)->dynamic_sections_created
+      || bed->always_renumber_dynsyms)
+    dynsymcount = _bfd_elf_link_renumber_dynsyms (output_bfd, info,
+						  &section_sym_count);
+
   if (elf_hash_table (info)->dynamic_sections_created)
     {
       bfd *dynobj;
       asection *s;
-      bfd_size_type dynsymcount;
-      unsigned long section_sym_count;
       unsigned int dtagcount;
 
       dynobj = elf_hash_table (info)->dynobj;
 
-      /* Assign dynsym indicies.  In a shared library we generate a
-	 section symbol for each output section, which come first.
-	 Next come all of the back-end allocated local dynamic syms,
-	 followed by the rest of the global symbols.  */
-
-      dynsymcount = _bfd_elf_link_renumber_dynsyms (output_bfd, info,
-						    &section_sym_count);
-
       /* Work out the size of the symbol version section.  */
       s = bfd_get_linker_section (dynobj, ".gnu.version");
       BFD_ASSERT (s != NULL);