x86; Allow IFUNC pointer defined in PDE

If IFUNC symbol is defined in position-dependent executable, we should
change it to the normal function and set its address to its PLT entry
which should be resolved by R_*_IRELATIVE at run-time.  All external
references should be resolved to its PLT in executable.

bfd/

	PR ld/23169
	* elf-ifunc.c (_bfd_elf_allocate_ifunc_dyn_relocs): Don't issue
	an error on IFUNC pointer defined in PDE.
	* elf32-i386.c (elf_i386_finish_dynamic_symbol): Call
	_bfd_x86_elf_link_fixup_ifunc_symbol.
	* elf64-x86-64.c (elf_x86_64_finish_dynamic_symbol): Likewise.
	* elfxx-x86.c (_bfd_x86_elf_link_fixup_ifunc_symbol): New
	function.
	* elfxx-x86.h (_bfd_x86_elf_link_fixup_ifunc_symbol): New.

ld/

	PR ld/23169
	* testsuite/ld-ifunc/ifunc-9-i386.d: New file.
	* testsuite/ld-ifunc/ifunc-9-x86-64.d: Likewise.
	* testsuite/ld-ifunc/pr23169a.c: Likewise.
	* testsuite/ld-ifunc/pr23169a.rd: Likewise.
	* testsuite/ld-ifunc/pr23169b.c: Likewise.
	* testsuite/ld-ifunc/pr23169b.c: Likewise.
	* testsuite/ld-ifunc/pr23169c.rd: Likewise.
	* testsuite/ld-ifunc/pr23169c.rd: Likewise.
	* testsuite/ld-ifunc/ifunc-9-x86.d: Removed.
	* testsuite/ld-ifunc/ifunc.exp: Run PR ld/23169 tests.

6 files changed, 74 insertions, 1 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 10b9679..f8138a1 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,5 +1,17 @@
 2018-05-14  H.J. Lu  <hongjiu.lu@intel.com>
 
+	PR ld/23169
+	* elf-ifunc.c (_bfd_elf_allocate_ifunc_dyn_relocs): Don't issue
+	an error on IFUNC pointer defined in PDE.
+	* elf32-i386.c (elf_i386_finish_dynamic_symbol): Call
+	_bfd_x86_elf_link_fixup_ifunc_symbol.
+	* elf64-x86-64.c (elf_x86_64_finish_dynamic_symbol): Likewise.
+	* elfxx-x86.c (_bfd_x86_elf_link_fixup_ifunc_symbol): New
+	function.
+	* elfxx-x86.h (_bfd_x86_elf_link_fixup_ifunc_symbol): New.
+
+2018-05-14  H.J. Lu  <hongjiu.lu@intel.com>
+
 	PR ld/23162
 	* elfxx-x86.c (elf_x86_linker_defined): New function.
 	(_bfd_x86_elf_link_check_relocs): Use it to mark __bss_start,
diff --git a/bfd/elf-ifunc.c b/bfd/elf-ifunc.c
index 5716ab3..b8a3632 100644
--- a/bfd/elf-ifunc.c
+++ b/bfd/elf-ifunc.c
@@ -131,8 +131,15 @@ _bfd_elf_allocate_ifunc_dyn_relocs (struct bfd_link_info *info,
      the resolved function may be used.  But in non-PIC executable,
      the address of its .plt slot may be used.  Pointer equality may
      not work correctly.  PIE or non-PLT reference should be used if
-     pointer equality is required here.  */
+     pointer equality is required here.
+
+     If STT_GNU_IFUNC symbol is defined in position-dependent executable,
+     backend should change it to the normal function and set its address
+     to its PLT entry which should be resolved by R_*_IRELATIVE at
+     run-time.  All external references should be resolved to its PLT in
+     executable.  */
   if (!need_dynreloc
+      && !(bfd_link_pde (info) && h->def_regular)
       && (h->dynindx != -1
 	  || info->export_dynamic)
       && h->pointer_equality_needed)
diff --git a/bfd/elf32-i386.c b/bfd/elf32-i386.c
index c1c4ed0..580a591 100644
--- a/bfd/elf32-i386.c
+++ b/bfd/elf32-i386.c
@@ -3805,6 +3805,8 @@ elf_i386_finish_dynamic_symbol (bfd *output_bfd,
 	sym->st_value = 0;
     }
 
+  _bfd_x86_elf_link_fixup_ifunc_symbol (info, htab, h, sym);
+
   /* Don't generate dynamic GOT relocation against undefined weak
      symbol in executable.  */
   if (h->got.offset != (bfd_vma) -1
diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c
index a0ebd2c..e5a4dbc 100644
--- a/bfd/elf64-x86-64.c
+++ b/bfd/elf64-x86-64.c
@@ -4147,6 +4147,8 @@ elf_x86_64_finish_dynamic_symbol (bfd *output_bfd,
 	sym->st_value = 0;
     }
 
+  _bfd_x86_elf_link_fixup_ifunc_symbol (info, htab, h, sym);
+
   /* Don't generate dynamic GOT relocation against undefined weak
      symbol in executable.  */
   if (h->got.offset != (bfd_vma) -1
diff --git a/bfd/elfxx-x86.c b/bfd/elfxx-x86.c
index 6c1f4c3..936b4c6 100644
--- a/bfd/elfxx-x86.c
+++ b/bfd/elfxx-x86.c
@@ -1730,6 +1730,52 @@ _bfd_x86_elf_fixup_symbol (struct bfd_link_info *info,
   return TRUE;
 }
 
+/* Change the STT_GNU_IFUNC symbol defined in position-dependent
+   executable into the normal function symbol and set its address
+   to its PLT entry, which should be resolved by R_*_IRELATIVE at
+   run-time.  */
+
+void
+_bfd_x86_elf_link_fixup_ifunc_symbol (struct bfd_link_info *info,
+				      struct elf_x86_link_hash_table *htab,
+				      struct elf_link_hash_entry *h,
+				      Elf_Internal_Sym *sym)
+{
+  if (bfd_link_pde (info)
+      && h->def_regular
+      && h->dynindx != -1
+      && h->plt.offset != (bfd_vma) -1
+      && h->type == STT_GNU_IFUNC
+      && h->pointer_equality_needed)
+    {
+      asection *plt_s;
+      bfd_vma plt_offset;
+      bfd *output_bfd = info->output_bfd;
+
+      if (htab->plt_second)
+	{
+	  struct elf_x86_link_hash_entry *eh
+	    = (struct elf_x86_link_hash_entry *) h;
+
+	  plt_s = htab->plt_second;
+	  plt_offset = eh->plt_second.offset;
+	}
+      else
+	{
+	  plt_s = htab->elf.splt;
+	  plt_offset = h->plt.offset;
+	}
+
+      sym->st_size = 0;
+      sym->st_info = ELF_ST_INFO (ELF_ST_BIND (sym->st_info), STT_FUNC);
+      sym->st_shndx
+	= _bfd_elf_section_from_bfd_section (output_bfd,
+					     plt_s->output_section);
+      sym->st_value = (plt_s->output_section->vma
+		       + plt_s->output_offset + plt_offset);
+    }
+}
+
 /* Return TRUE if symbol should be hashed in the `.gnu.hash' section.  */
 
 bfd_boolean
diff --git a/bfd/elfxx-x86.h b/bfd/elfxx-x86.h
index efa835e..8f67c23 100644
--- a/bfd/elfxx-x86.h
+++ b/bfd/elfxx-x86.h
@@ -674,6 +674,10 @@ extern bfd_boolean _bfd_x86_elf_merge_gnu_properties
 extern bfd * _bfd_x86_elf_link_setup_gnu_properties
   (struct bfd_link_info *, struct elf_x86_init_table *);
 
+extern void _bfd_x86_elf_link_fixup_ifunc_symbol
+  (struct bfd_link_info *, struct elf_x86_link_hash_table *,
+   struct elf_link_hash_entry *, Elf_Internal_Sym *sym);
+
 #define bfd_elf64_mkobject \
   _bfd_x86_elf_mkobject
 #define bfd_elf32_mkobject \