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.

17 files changed, 290 insertions, 4 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 \
diff --git a/ld/ChangeLog b/ld/ChangeLog
index 178ca68..fbc4d59 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,5 +1,19 @@
 2018-05-14  H.J. Lu  <hongjiu.lu@intel.com>
 
+	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.
+
+2018-05-14  H.J. Lu  <hongjiu.lu@intel.com>
+
 	PR ld/23162
 	* testsuite/ld-elf/pr23162.map: New file.
 	* testsuite/ld-elf/pr23162.rd: Likewise.
diff --git a/ld/testsuite/ld-ifunc/ifunc-9-i386.d b/ld/testsuite/ld-ifunc/ifunc-9-i386.d
new file mode 100644
index 0000000..754ee2d
--- /dev/null
+++ b/ld/testsuite/ld-ifunc/ifunc-9-i386.d
@@ -0,0 +1,9 @@
+#source: ifunc-9-x86.s
+#as: --32
+#ld: -m elf_i386 --export-dynamic
+#readelf: -r --wide
+#target: x86_64-*-* i?86-*-*
+
+Relocation section '.rel.plt' at .*
+[ ]+Offset[ ]+Info[ ]+Type[ ]+.*
+[0-9a-f]+[ ]+[0-9a-f]+[ ]+R_386_IRELATIVE[ ]*
diff --git a/ld/testsuite/ld-ifunc/ifunc-9-x86-64.d b/ld/testsuite/ld-ifunc/ifunc-9-x86-64.d
new file mode 100644
index 0000000..85c3a69
--- /dev/null
+++ b/ld/testsuite/ld-ifunc/ifunc-9-x86-64.d
@@ -0,0 +1,9 @@
+#source: ifunc-9-x86.s
+#as: --64
+#ld: -melf_x86_64 --export-dynamic
+#readelf: -r --wide
+#target: x86_64-*-*
+
+Relocation section '.rela.plt' at .*
+[ ]+Offset[ ]+Info[ ]+Type[ ]+.*
+[0-9a-f]+[ ]+[0-9a-f]+[ ]+R_X86_64_IRELATIVE[ ]+[0-9a-f]*
diff --git a/ld/testsuite/ld-ifunc/ifunc-9-x86.d b/ld/testsuite/ld-ifunc/ifunc-9-x86.d
deleted file mode 100644
index 7390dd1..0000000
--- a/ld/testsuite/ld-ifunc/ifunc-9-x86.d
+++ /dev/null
@@ -1,3 +0,0 @@
-#ld: --export-dynamic
-#error: .*dynamic STT_GNU_IFUNC symbol `foo' with pointer equality in `.*.o' can not be used when making an executable; recompile with -fPIE and relink with -pie
-#target: x86_64-*-* i?86-*-*
diff --git a/ld/testsuite/ld-ifunc/ifunc.exp b/ld/testsuite/ld-ifunc/ifunc.exp
index d9cc381..9f4aa73 100644
--- a/ld/testsuite/ld-ifunc/ifunc.exp
+++ b/ld/testsuite/ld-ifunc/ifunc.exp
@@ -581,6 +581,76 @@ run_cc_link_tests [list \
 	{} \
 	"libpr18841cn.so" \
     ] \
+    [list \
+	"Build libpr23169a.so" \
+	"-shared" \
+	"-fPIC -O2 -g" \
+	{ pr23169a.c } \
+	{} \
+	"libpr23169a.so" \
+    ] \
+    [list \
+	"Build libpr23169b.so" \
+	"-shared -Wl,-z,now" \
+	"-fPIC -O2 -g" \
+	{ pr23169a.c } \
+	{} \
+	"libpr23169b.so" \
+    ] \
+    [list \
+	"Build pr23169a" \
+	"$NOPIE_LDFLAGS -Wl,--no-as-needed tmpdir/libpr23169a.so" \
+	"$NOPIE_CFLAGS -O2 -g" \
+	{ pr23169b.c pr23169c.c } \
+	{{readelf {--dyn-syms} pr23169a.rd} \
+	 {readelf {-r -W} pr23169b.rd}} \
+	"pr23169a" \
+    ] \
+    [list \
+	"Build pr23169b" \
+	"-pie -Wl,--no-as-needed tmpdir/libpr23169a.so" \
+	"-fPIE -O2 -g" \
+	{ pr23169b.c pr23169c.c } \
+	{{readelf {--dyn-syms} pr23169c.rd} \
+	 {readelf {-r -W} pr23169b.rd}} \
+	"pr23169b" \
+    ] \
+    [list \
+	"Build pr23169c" \
+	"$NOPIE_LDFLAGS -Wl,--no-as-needed tmpdir/libpr23169a.so" \
+	"-fPIE -O2 -g" \
+	{ pr23169b.c pr23169c.c } \
+	{{readelf {--dyn-syms} pr23169c.rd} \
+	 {readelf {-r -W} pr23169b.rd}} \
+	"pr23169c" \
+    ] \
+    [list \
+	"Build pr23169d" \
+	"$NOPIE_LDFLAGS -Wl,--no-as-needed,-z,now tmpdir/libpr23169b.so" \
+	"$NOPIE_CFLAGS -O2 -g" \
+	{ pr23169b.c pr23169c.c } \
+	{{readelf {--dyn-syms} pr23169a.rd} \
+	 {readelf {-r -W} pr23169b.rd}} \
+	"pr23169d" \
+    ] \
+    [list \
+	"Build pr23169e" \
+	"-pie -Wl,--no-as-needed,-z,now tmpdir/libpr23169b.so" \
+	"-fPIE -O2 -g" \
+	{ pr23169b.c pr23169c.c } \
+	{{readelf {--dyn-syms} pr23169c.rd} \
+	 {readelf {-r -W} pr23169b.rd}} \
+	"pr23169e" \
+    ] \
+    [list \
+	"Build pr23169f" \
+	"$NOPIE_LDFLAGS -Wl,--no-as-needed,-z,now tmpdir/libpr23169b.so" \
+	"-fPIE -O2 -g" \
+	{ pr23169b.c pr23169c.c } \
+	{{readelf {--dyn-syms} pr23169c.rd} \
+	 {readelf {-r -W} pr23169b.rd}} \
+	"pr23169f" \
+    ] \
 ]
 
 run_ld_link_exec_tests [list \
@@ -632,4 +702,58 @@ run_ld_link_exec_tests [list \
 	"pr18841cn" \
 	"pr18841.out" \
     ] \
+    [list \
+	"Run pr23169a" \
+	"$NOPIE_LDFLAGS -Wl,--no-as-needed tmpdir/libpr23169a.so" \
+	"" \
+	{ pr23169b.c pr23169c.c } \
+	"pr23169a" \
+	"pass.out" \
+	"$NOPIE_CFLAGS -O2 -g" \
+    ] \
+    [list \
+	"Run pr23169b" \
+	"-pie -Wl,--no-as-needed tmpdir/libpr23169a.so" \
+	"" \
+	{ pr23169b.c pr23169c.c } \
+	"pr23169b" \
+	"pass.out" \
+	"-fPIE -O2 -g" \
+    ] \
+    [list \
+	"Run pr23169c" \
+	"$NOPIE_LDFLAGS -Wl,--no-as-needed tmpdir/libpr23169a.so" \
+	"" \
+	{ pr23169b.c pr23169c.c } \
+	"pr23169c" \
+	"pass.out" \
+	"-fPIE -O2 -g" \
+    ] \
+    [list \
+	"Run pr23169d" \
+	"$NOPIE_LDFLAGS -Wl,--no-as-needed,-z,now tmpdir/libpr23169b.so" \
+	"" \
+	{ pr23169b.c pr23169c.c } \
+	"pr23169d" \
+	"pass.out" \
+	"$NOPIE_CFLAGS -O2 -g" \
+    ] \
+    [list \
+	"Run pr23169e" \
+	"-pie -Wl,--no-as-needed,-z,now tmpdir/libpr23169b.so" \
+	"" \
+	{ pr23169b.c pr23169c.c } \
+	"pr23169e" \
+	"pass.out" \
+	"-fPIE -O2 -g" \
+    ] \
+    [list \
+	"Run pr23169f" \
+	"$NOPIE_LDFLAGS -Wl,--no-as-needed,-z,now tmpdir/libpr23169b.so" \
+	"" \
+	{ pr23169b.c pr23169c.c } \
+	"pr23169f" \
+	"pass.out" \
+	"-fPIE -O2 -g" \
+    ] \
 ]
diff --git a/ld/testsuite/ld-ifunc/pr23169a.c b/ld/testsuite/ld-ifunc/pr23169a.c
new file mode 100644
index 0000000..02bf220
--- /dev/null
+++ b/ld/testsuite/ld-ifunc/pr23169a.c
@@ -0,0 +1,9 @@
+int (*func_p) (void);
+extern int func (void);
+
+void
+foo (void)
+{
+  if (func_p != &func || func_p () != 0xbadbeef)
+    __builtin_abort ();
+}
diff --git a/ld/testsuite/ld-ifunc/pr23169a.rd b/ld/testsuite/ld-ifunc/pr23169a.rd
new file mode 100644
index 0000000..ca04d8f
--- /dev/null
+++ b/ld/testsuite/ld-ifunc/pr23169a.rd
@@ -0,0 +1,6 @@
+
+Symbol table '\.dynsym' contains [0-9]+ entries:
+ +Num: +Value +Size Type +Bind +Vis +Ndx Name
+#...
+ +[0-9]+: +[a-f0-9]+ +0 +FUNC +GLOBAL +DEFAULT +[0-9]+ +func
+#...
diff --git a/ld/testsuite/ld-ifunc/pr23169b.c b/ld/testsuite/ld-ifunc/pr23169b.c
new file mode 100644
index 0000000..99790d4
--- /dev/null
+++ b/ld/testsuite/ld-ifunc/pr23169b.c
@@ -0,0 +1,23 @@
+#include <stdio.h>
+
+extern int (*func_p) (void);
+extern int func (void);
+extern void foo (void);
+
+
+void
+bar (void)
+{
+  if (func_p != &func || func_p () != 0xbadbeef)
+    __builtin_abort ();
+}
+
+int
+main ()
+{
+  func_p = &func;
+  foo ();
+  bar ();
+  printf ("PASS\n");
+  return 0;
+}
diff --git a/ld/testsuite/ld-ifunc/pr23169b.rd b/ld/testsuite/ld-ifunc/pr23169b.rd
new file mode 100644
index 0000000..d57a793
--- /dev/null
+++ b/ld/testsuite/ld-ifunc/pr23169b.rd
@@ -0,0 +1,3 @@
+#failif
+[a-f0-9]+ +[0-9a-f]+ +R_.*_* +[a-f0-9]+ +func(| \+ 0)
+...
diff --git a/ld/testsuite/ld-ifunc/pr23169c.c b/ld/testsuite/ld-ifunc/pr23169c.c
new file mode 100644
index 0000000..b530108
--- /dev/null
+++ b/ld/testsuite/ld-ifunc/pr23169c.c
@@ -0,0 +1,13 @@
+static int
+ifunc (void)
+{
+  return 0xbadbeef;
+}
+
+void func(void) __attribute__((ifunc("resolve_func")));
+
+static void *
+resolve_func (void)
+{
+  return ifunc;
+}
diff --git a/ld/testsuite/ld-ifunc/pr23169c.rd b/ld/testsuite/ld-ifunc/pr23169c.rd
new file mode 100644
index 0000000..1c4ba8a
--- /dev/null
+++ b/ld/testsuite/ld-ifunc/pr23169c.rd
@@ -0,0 +1,6 @@
+
+Symbol table '\.dynsym' contains [0-9]+ entries:
+ +Num: +Value +Size Type +Bind +Vis +Ndx Name
+#...
+ +[0-9]+: +[a-f0-9]+ +[0-9]+ +IFUNC +GLOBAL +DEFAULT +[0-9]+ +func
+#...