aarch64: handle STO_AARCH64_VARIANT_PCS in bfd

Propagate STO_AARCH64_VARIANT_PCS st_other attribute to the output and
add DT_AARCH64_VARIANT_PCS dynamic tag if necessary.

Mismatching attributes are not diagnosed.

bfd/ChangeLog:

	* elfnn-aarch64.c (elfNN_aarch64_merge_symbol_attribute): New function.
	(struct elf_aarch64_link_hash_table): Add variant_pcs member.
	(elfNN_aarch64_allocate_dynrelocs): Update variant_pcs.
	(elfNN_aarch64_size_dynamic_sections): Add DT_AARCH64_VARIANT_PCS.
	(elf_backend_merge_symbol_attribute): Define.

ld/ChangeLog:

	* testsuite/ld-aarch64/aarch64-elf.exp: Add new tests.
	* testsuite/ld-aarch64/variant_pcs-1.s: New asm for tests.
	* testsuite/ld-aarch64/variant_pcs-2.s: New asm for tests.
	* testsuite/ld-aarch64/variant_pcs-now.d: New test.
	* testsuite/ld-aarch64/variant_pcs-r.d: New test.
	* testsuite/ld-aarch64/variant_pcs-shared.d: New test.
	* testsuite/ld-aarch64/variant_pcs.ld: New linker script for tests.

2 files changed, 49 insertions, 0 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index fe2f5b1..a7603da 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,11 @@
+2019-05-24  Szabolcs Nagy  <szabolcs.nagy@arm.com>
+
+	* elfnn-aarch64.c (elfNN_aarch64_merge_symbol_attribute): New function.
+	(struct elf_aarch64_link_hash_table): Add variant_pcs member.
+	(elfNN_aarch64_allocate_dynrelocs): Update variant_pcs.
+	(elfNN_aarch64_size_dynamic_sections): Add DT_AARCH64_VARIANT_PCS.
+	(elf_backend_merge_symbol_attribute): Define.
+
 2019-05-24  Alan Modra  <amodra@gmail.com>
 
 	* po/SRC-POTFILES.in: Regenerate.
diff --git a/bfd/elfnn-aarch64.c b/bfd/elfnn-aarch64.c
index 9e28544..761e6b9 100644
--- a/bfd/elfnn-aarch64.c
+++ b/bfd/elfnn-aarch64.c
@@ -2681,6 +2681,9 @@ struct elf_aarch64_link_hash_table
   unsigned int top_index;
   asection **input_list;
 
+  /* JUMP_SLOT relocs for variant PCS symbols may be present.  */
+  int variant_pcs;
+
   /* The offset into splt of the PLT entry for the TLS descriptor
      resolver.  Special values are 0, if not necessary (or not found
      to be necessary yet), and -1 if needed but not determined
@@ -2895,6 +2898,31 @@ elfNN_aarch64_copy_indirect_symbol (struct bfd_link_info *info,
   _bfd_elf_link_hash_copy_indirect (info, dir, ind);
 }
 
+/* Merge non-visibility st_other attributes.  */
+
+static void
+elfNN_aarch64_merge_symbol_attribute (struct elf_link_hash_entry *h,
+				      const Elf_Internal_Sym *isym,
+				      bfd_boolean definition ATTRIBUTE_UNUSED,
+				      bfd_boolean dynamic ATTRIBUTE_UNUSED)
+{
+  unsigned int isym_sto = isym->st_other & ~ELF_ST_VISIBILITY (-1);
+  unsigned int h_sto = h->other & ~ELF_ST_VISIBILITY (-1);
+
+  if (isym_sto == h_sto)
+    return;
+
+  if (isym_sto & ~STO_AARCH64_VARIANT_PCS)
+    /* Not fatal, this callback cannot fail.  */
+    _bfd_error_handler (_("unknown attribute for symbol `%s': 0x%02x"),
+			h->root.root.string, isym_sto);
+
+  /* Note: Ideally we would warn about any attribute mismatch, but
+     this api does not allow that without substantial changes.  */
+  if (isym_sto & STO_AARCH64_VARIANT_PCS)
+    h->other |= STO_AARCH64_VARIANT_PCS;
+}
+
 /* Destroy an AArch64 elf linker hash table.  */
 
 static void
@@ -8571,6 +8599,12 @@ elfNN_aarch64_allocate_dynrelocs (struct elf_link_hash_entry *h, void *inf)
 	     updated.  */
 
 	  htab->root.srelplt->reloc_count++;
+
+	  /* Mark the DSO in case R_<CLS>_JUMP_SLOT relocs against
+	     variant PCS symbols are present.  */
+	  if (h->other & STO_AARCH64_VARIANT_PCS)
+	    htab->variant_pcs = 1;
+
 	}
       else
 	{
@@ -9159,6 +9193,10 @@ elfNN_aarch64_size_dynamic_sections (bfd *output_bfd ATTRIBUTE_UNUSED,
 	      || !add_dynamic_entry (DT_JMPREL, 0))
 	    return FALSE;
 
+	  if (htab->variant_pcs
+	      && !add_dynamic_entry (DT_AARCH64_VARIANT_PCS, 0))
+	    return FALSE;
+
 	  if (htab->tlsdesc_plt
 	      && !(info->flags & DF_BIND_NOW)
 	      && (!add_dynamic_entry (DT_TLSDESC_PLT, 0)
@@ -10083,6 +10121,9 @@ const struct elf_size_info elfNN_aarch64_size_info =
 #define elf_backend_copy_indirect_symbol	\
   elfNN_aarch64_copy_indirect_symbol
 
+#define elf_backend_merge_symbol_attribute	\
+  elfNN_aarch64_merge_symbol_attribute
+
 /* Create .dynbss, and .rela.bss sections in DYNOBJ, and set up shortcuts
    to them in our hash.  */
 #define elf_backend_create_dynamic_sections	\