x86: Support Intel Shadow Stack with SHSTK property

To support Intel Shadow Stack (SHSTK) in Intel Control-flow Enforcement
Technology (CET) instructions:

https://software.intel.com/sites/default/files/managed/4d/2a/control-flow-enforcement-technology-preview.pdf

 #define GNU_PROPERTY_X86_FEATURE_1_SHSTK (1U << 1)

is added to GNU program properties to indicate that all executable sections
are compatible with SHSTK where return address popped from shadow stack
always matches return address popped from normal stack.

GNU_PROPERTY_X86_FEATURE_1_SHSTK is set on output only if it is set on all
relocatable inputs.

bfd/

	* elf32-i386.c (elf_i386_merge_gnu_properties): If info->shstk
	is set, turn on GNU_PROPERTY_X86_FEATURE_1_SHSTK.
	(elf_i386_link_setup_gnu_properties): If info->shstk is set,
	turn on GNU_PROPERTY_X86_FEATURE_1_IBT.
	* elf64-x86-64.c (elf_x86_64_merge_gnu_properties): If
	info->shstk is set, turn on GNU_PROPERTY_X86_FEATURE_1_SHSTK.
	(elf_x86_64_link_setup_gnu_properties): If info->shstk is set,
	turn on GNU_PROPERTY_X86_FEATURE_1_IBT.

binutils/

	* readelf.c (decode_x86_feature): Decode
	GNU_PROPERTY_X86_FEATURE_1_SHSTK.
	* testsuite/binutils-all/i386/shstk.d: New file.
	* testsuite/binutils-all/i386/shstk.s: Likewise.
	* testsuite/binutils-all/x86-64/shstk-x32.d: Likewise.
	* testsuite/binutils-all/x86-64/shstk.d: Likewise.
	* testsuite/binutils-all/x86-64/shstk.s: Likewise.

include/

	* bfdlink.h (bfd_link_info): Add shstk.
	* elf/common.h (GNU_PROPERTY_X86_FEATURE_1_SHSTK): New.

ld/

	* NEWS: Mention -z shstk and GNU_PROPERTY_X86_FEATURE_1_SHSTK.
	* emulparams/cet.sh (PARSE_AND_LIST_OPTIONS_CET): Add "-z shstk".
	(PARSE_AND_LIST_ARGS_CASE_Z_CET): Support "-z shstk".
	* ld.texinfo: Document -z shstk.
	* testsuite/ld-i386/i386.exp: Run SHSTK tests.
	* testsuite/ld-x86-64/x86-64.exp: Likewise.
	* testsuite/ld-i386/property-x86-shstk.s: New file.
	* testsuite/ld-i386/property-x86-shstk1a.d: Likewise.
	* testsuite/ld-i386/property-x86-shstk1b.d: Likewise.
	* testsuite/ld-i386/property-x86-shstk2.d: Likewise.
	* testsuite/ld-i386/property-x86-shstk3a.d: Likewise.
	* testsuite/ld-i386/property-x86-shstk3b.d: Likewise.
	* testsuite/ld-i386/property-x86-shstk4.d: Likewise.
	* testsuite/ld-i386/property-x86-shstk5.d: Likewise.
	* testsuite/ld-x86-64/property-x86-shstk.s: Likewise.
	* testsuite/ld-x86-64/property-x86-shstk1a-x32.d: Likewise.
	* testsuite/ld-x86-64/property-x86-shstk1a.d: Likewise.
	* testsuite/ld-x86-64/property-x86-shstk1b-x32.d: Likewise.
	* testsuite/ld-x86-64/property-x86-shstk1b.d: Likewise.
	* testsuite/ld-x86-64/property-x86-shstk2-x32.d: Likewise.
	* testsuite/ld-x86-64/property-x86-shstk2.d: Likewise.
	* testsuite/ld-x86-64/property-x86-shstk3a-x32.d: Likewise.
	* testsuite/ld-x86-64/property-x86-shstk3a.d: Likewise.
	* testsuite/ld-x86-64/property-x86-shstk3b-x32.d: Likewise.
	* testsuite/ld-x86-64/property-x86-shstk3b.d: Likewise.
	* testsuite/ld-x86-64/property-x86-shstk4-x32.d: Likewise.
	* testsuite/ld-x86-64/property-x86-shstk4.d: Likewise.
	* testsuite/ld-x86-64/property-x86-shstk5-x32.d: Likewise.
	* testsuite/ld-x86-64/property-x86-shstk5.d: Likewise.

1 files changed, 14 insertions, 4 deletions

diff --git a/bfd/elf32-i386.c b/bfd/elf32-i386.c
index d662816..ee8219c 100644
--- a/bfd/elf32-i386.c
+++ b/bfd/elf32-i386.c
@@ -6751,8 +6751,11 @@ elf_i386_merge_gnu_properties (struct bfd_link_info *info,
 	  features = 0;
 	  if (info->ibt)
 	    features = GNU_PROPERTY_X86_FEATURE_1_IBT;
+	  if (info->shstk)
+	    features |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
 	  number = aprop->u.number;
-	  /* Add GNU_PROPERTY_X86_FEATURE_1_IBT.  */
+	  /* Add GNU_PROPERTY_X86_FEATURE_1_IBT and
+	     GNU_PROPERTY_X86_FEATURE_1_SHSTK.  */
 	  aprop->u.number = (number & bprop->u.number) | features;
 	  updated = number != (unsigned int) aprop->u.number;
 	  /* Remove the property if all feature bits are cleared.  */
@@ -6764,9 +6767,12 @@ elf_i386_merge_gnu_properties (struct bfd_link_info *info,
 	  features = 0;
 	  if (info->ibt)
 	    features = GNU_PROPERTY_X86_FEATURE_1_IBT;
+	  if (info->shstk)
+	    features |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
 	  if (features)
 	    {
-	      /* Add GNU_PROPERTY_X86_FEATURE_1_IBT.  */
+	      /* Add GNU_PROPERTY_X86_FEATURE_1_IBT and
+		 GNU_PROPERTY_X86_FEATURE_1_SHSTK.  */
 	      if (aprop != NULL)
 		{
 		  number = aprop->u.number;
@@ -6813,9 +6819,12 @@ elf_i386_link_setup_gnu_properties (struct bfd_link_info *info)
   features = 0;
   if (info->ibt)
     features = GNU_PROPERTY_X86_FEATURE_1_IBT;
+  if (info->shstk)
+    features |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
   if (features)
     {
-      /* Turn on GNU_PROPERTY_X86_FEATURE_1_IBT.  */
+      /* Turn on GNU_PROPERTY_X86_FEATURE_1_IBT and
+	 GNU_PROPERTY_X86_FEATURE_1_SHSTK.  */
       bfd *ebfd = NULL;
       elf_property *prop;
 
@@ -6833,7 +6842,8 @@ elf_i386_link_setup_gnu_properties (struct bfd_link_info *info)
 		prop = _bfd_elf_get_property (pbfd,
 					      GNU_PROPERTY_X86_FEATURE_1_AND,
 					      4);
-		/* Add GNU_PROPERTY_X86_FEATURE_1_IBT.  */
+		/* Add GNU_PROPERTY_X86_FEATURE_1_IBT and
+		   GNU_PROPERTY_X86_FEATURE_1_SHSTK.  */
 		prop->u.number |= features;
 		prop->pr_kind = property_number;
 		break;