Add extern_protected_data and set it for x86

Re-apply: commit ca3fe95e469b9daec153caa2c90665f5daaec2b5

With copy relocation, address of protected data defined in the shared
library may be external.  This patch adds extern_protected_data and
changes _bfd_elf_symbol_refs_local_p to return false for protected data
if extern_protected_data is true.

This patch will break building shared libraries with protected data
symbols using GCCs older than GCC 5 without the bug fix for

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65248

GCC backport request should be made in the GCC bug report above.

To get correct run-time behavior on Linux, glibc 2.22 or above are
required, which have the bug fix for

https://sourceware.org/bugzilla/show_bug.cgi?id=17711

Backports for glibc 2.21, 2.20, 2.19 and 2.18 are on hjl/pr17711/2.21,
hjl/pr17711/2.20, hjl/pr17711/2.19 and hjl/pr17711/2.18 branches,
respectively, at

https://sourceware.org/git/?p=glibc.git;a=summary

bfd/

	PR ld/pr15228
	PR ld/pr17709
	* elf-bfd.h (elf_backend_data): Add extern_protected_data.
	* elf32-i386.c (elf_backend_extern_protected_data): New.
	Defined to 1.
	* elf64-x86-64.c (elf_backend_extern_protected_data): Likewise.
	* elflink.c (_bfd_elf_adjust_dynamic_copy): Don't error on
	copy relocs against protected symbols if extern_protected_data
	is true.
	(_bfd_elf_symbol_refs_local_p): Don't return true on protected
	non-function symbols if extern_protected_data is true.
	* elfxx-target.h (elf_backend_extern_protected_data): New.
	Default to 0.
	(elfNN_bed): Initialize extern_protected_data with
	elf_backend_extern_protected_data.

ld/testsuite/

	PR ld/pr15228
	PR ld/pr17709
	* ld-i386/i386.exp (i386tests): Add a test for PR ld/17709.
	* ld-i386/pr17709-nacl.rd: New file.
	* ld-i386/pr17709.rd: Likewise.
	* ld-i386/pr17709a.s: Likewise.
	* ld-i386/pr17709b.s: Likewise.
	* ld-i386/protected3.d: Updated.
	* ld-i386/protected3.s: Likewise.
	* ld-x86-64/pr17709-nacl.rd: New file.
	* ld-x86-64/pr17709.rd: Likewise.
	* ld-x86-64/pr17709a.s: Likewise.
	* ld-x86-64/pr17709b.s: Likewise.
	* ld-x86-64/protected3.d: Updated.
	* ld-x86-64/protected3.s: Likewise.
	* ld-x86-64/x86-64.exp (x86_64tests): Add a test for PR ld/17709.

6 files changed, 35 insertions, 4 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 10a3ae2..dd30698 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,5 +1,23 @@
 2015-04-10  H.J. Lu  <hongjiu.lu@intel.com>
 
+	PR ld/pr15228
+	PR ld/pr17709
+	* elf-bfd.h (elf_backend_data): Add extern_protected_data.
+	* elf32-i386.c (elf_backend_extern_protected_data): New.
+	Defined to 1.
+	* elf64-x86-64.c (elf_backend_extern_protected_data): Likewise.
+	* elflink.c (_bfd_elf_adjust_dynamic_copy): Don't error on
+	copy relocs against protected symbols if extern_protected_data
+	is true.
+	(_bfd_elf_symbol_refs_local_p): Don't return true on protected
+	non-function symbols if extern_protected_data is true.
+	* elfxx-target.h (elf_backend_extern_protected_data): New.
+	Default to 0.
+	(elfNN_bed): Initialize extern_protected_data with
+	elf_backend_extern_protected_data.
+
+2015-04-10  H.J. Lu  <hongjiu.lu@intel.com>
+
 	* compress.c (bfd_compress_section_contents): Replace bfd_malloc
 	and free with bfd_alloc and bfd_release on compressed buffer.
 	Release buffer if compressed section isn't smaller.
diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h
index 8def41b..e435e52 100644
--- a/bfd/elf-bfd.h
+++ b/bfd/elf-bfd.h
@@ -1363,6 +1363,10 @@ struct elf_backend_data
      in length rather than sec->size in length, if sec->rawsize is
      non-zero and smaller than sec->size.  */
   unsigned caches_rawsize : 1;
+
+  /* Address of protected data defined in the shared library may be
+     external, i.e., due to copy relocation.   */
+  unsigned extern_protected_data : 1;
 };
 
 /* Information about reloc sections associated with a bfd_elf_section_data
diff --git a/bfd/elf32-i386.c b/bfd/elf32-i386.c
index 3f16fc1..52f4d33 100644
--- a/bfd/elf32-i386.c
+++ b/bfd/elf32-i386.c
@@ -5292,6 +5292,7 @@ elf_i386_add_symbol_hook (bfd * abfd,
 #define elf_backend_want_plt_sym	0
 #define elf_backend_got_header_size	12
 #define elf_backend_plt_alignment	4
+#define elf_backend_extern_protected_data 1
 
 /* Support RELA for objdump of prelink objects.  */
 #define elf_info_to_howto		      elf_i386_info_to_howto_rel
diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c
index 6eb8471..ab72306 100644
--- a/bfd/elf64-x86-64.c
+++ b/bfd/elf64-x86-64.c
@@ -5868,6 +5868,7 @@ static const struct bfd_elf_special_section
 #define elf_backend_got_header_size	    (GOT_ENTRY_SIZE*3)
 #define elf_backend_rela_normal		    1
 #define elf_backend_plt_alignment           4
+#define elf_backend_extern_protected_data   1
 
 #define elf_info_to_howto		    elf_x86_64_info_to_howto
 
diff --git a/bfd/elflink.c b/bfd/elflink.c
index 5bc9e9b..98d3108 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -2673,7 +2673,9 @@ _bfd_elf_adjust_dynamic_copy (struct bfd_link_info *info,
   /* Increment the size of DYNBSS to make room for the symbol.  */
   dynbss->size += h->size;
 
-  if (h->protected_def)
+  /* No error if extern_protected_data is true.  */
+  if (h->protected_def
+      && !get_elf_backend_data (dynbss->owner)->extern_protected_data)
     info->callbacks->einfo
       (_("%P: copy reloc against protected `%T' is dangerous\n"),
        h->root.root.string);
@@ -2833,8 +2835,9 @@ _bfd_elf_symbol_refs_local_p (struct elf_link_hash_entry *h,
 
   bed = get_elf_backend_data (hash_table->dynobj);
 
-  /* STV_PROTECTED non-function symbols are local.  */
-  if (!bed->is_function_type (h->type))
+  /* If extern_protected_data is false, STV_PROTECTED non-function
+     symbols are local.  */
+  if (!bed->extern_protected_data && !bed->is_function_type (h->type))
     return TRUE;
 
   /* Function pointer equality tests may require that STV_PROTECTED
diff --git a/bfd/elfxx-target.h b/bfd/elfxx-target.h
index 9bfb6c8..0085d6c 100644
--- a/bfd/elfxx-target.h
+++ b/bfd/elfxx-target.h
@@ -117,6 +117,9 @@
 #ifndef elf_backend_caches_rawsize
 #define elf_backend_caches_rawsize 0
 #endif
+#ifndef elf_backend_extern_protected_data
+#define elf_backend_extern_protected_data 0
+#endif
 #ifndef elf_backend_stack_align
 #define elf_backend_stack_align 16
 #endif
@@ -806,7 +809,8 @@ static struct elf_backend_data elfNN_bed =
   elf_backend_want_dynbss,
   elf_backend_want_p_paddr_set_to_zero,
   elf_backend_default_execstack,
-  elf_backend_caches_rawsize
+  elf_backend_caches_rawsize,
+  elf_backend_extern_protected_data
 };
 
 /* Forward declaration for use when initialising alternative_target field.  */