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PR20989, sparc GOT sequence optimization

This patch stops sparc ld doing the wrong thing when optimizing loads
from the GOT to a GOT pointer relative sequence.  Tested by code
inspection and cross-build of binutils+testsuite as I don't have a
sparc system handy to do native regression testing.  OK?

It would be easy to edit these code sequences to avoid the GOT load
for undefined weak hidden visibility syms by loading a zero inline,
but I'll leave that to the maintainers.  Also, you might like to check
why the testcase in the PR didn't signal a relocation overflow..

Oh, and I strongly suspect the same bug exists in gold.

	PR ld/20989
	* elfxx-sparc.c (gdop_relative_offset_ok): New function.
	(_bfd_sparc_elf_relocate_section): Use it to validate GOT
	indirect to GOT pointer relative code edit.

diff --git a/bfd/elfxx-sparc.c b/bfd/elfxx-sparc.c
index d7b2688..ca43c41 100644
--- a/bfd/elfxx-sparc.c
+++ b/bfd/elfxx-sparc.c
@@ -2927,6 +2927,33 @@ gdopoff (struct bfd_link_info *info, bfd_vma address)
   return address - got_base;
+/* Return whether H is local and its ADDRESS is within 4G of
+   _GLOBAL_OFFSET_TABLE_ and thus the offset may be calculated by a
+   sethi, xor sequence.  */
+static bfd_boolean
+gdop_relative_offset_ok (struct bfd_link_info *info,
+			 struct elf_link_hash_entry *h,
+			 bfd_vma address ATTRIBUTE_UNUSED)
+  if (!SYMBOL_REFERENCES_LOCAL (info, h))
+    return FALSE;
+  /* If H is undefined, ADDRESS will be zero.  We can't allow a
+     relative offset to "zero" when producing PIEs or shared libs.
+     Note that to get here with an undefined symbol it must also be
+     hidden or internal visibility.  */
+  if (bfd_link_pic (info)
+      && h != NULL
+      && (h->root.type == bfd_link_hash_undefweak
+	  || h->root.type == bfd_link_hash_undefined))
+    return FALSE;
+#ifdef BFD64
+  return gdopoff (info, address) + ((bfd_vma) 1 << 32) < (bfd_vma) 2 << 32;
+  return TRUE;
 /* Relocate a SPARC ELF section.  */
@@ -3168,7 +3195,7 @@ _bfd_sparc_elf_relocate_section (bfd *output_bfd,
-	  if (SYMBOL_REFERENCES_LOCAL (info, h))
+	  if (gdop_relative_offset_ok (info, h, relocation))
 	      r_type = (r_type == R_SPARC_GOTDATA_OP_HIX22
@@ -3178,7 +3205,7 @@ _bfd_sparc_elf_relocate_section (bfd *output_bfd,
-	  if (SYMBOL_REFERENCES_LOCAL (info, h))
+	  if (gdop_relative_offset_ok (info, h, relocation))
 	      bfd_vma insn = bfd_get_32 (input_bfd, contents + rel->r_offset);

Alan Modra
Australia Development Lab, IBM

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