[AArch64, 6/6] Enable BTI: Add configure option.

This patch is part of a series that enables ARMv8.5-A in GCC and
adds Branch Target Identification Mechanism.

This patch is adding a new configure option for enabling BTI and
Return Address Signing by default.

*** gcc/ChangeLog ***

2018-01-09  Sudakshina Das  <sudi.das@arm.com>

	* config/aarch64/aarch64.c (aarch64_override_options): Add case to
	check configure option to set BTI and Return Address Signing.
	* configure.ac: Add --enable-standard-branch-protection and
	--disable-standard-branch-protection.
	* configure: Regenerated.
	* doc/install.texi: Document the same.

*** gcc/testsuite/ChangeLog ***

2018-01-09  Sudakshina Das  <sudi.das@arm.com>

	* gcc.target/aarch64/bti-1.c: Update test to not add command line
	option when configure with bti.
	* gcc.target/aarch64/bti-2.c: Likewise.
	* lib/target-supports.exp
	(check_effective_target_default_branch_protection):
	Add configure check for --enable-standard-branch-protection.

From-SVN: r267770

gcc/ChangeLog

@@ -1,3 +1,12 @@
+2018-01-09  Sudakshina Das  <sudi.das@arm.com>
+
+	* config/aarch64/aarch64.c (aarch64_override_options): Add case to
+	check configure option to set BTI and Return Address Signing.
+	* configure.ac: Add --enable-standard-branch-protection and
+	--disable-standard-branch-protection.
+	* configure: Regenerated.
+	* doc/install.texi: Document the same.
+
 2018-01-09  Sudakshina Das  <sudi.das@arm.com>
 	    Ramana Radhakrishnan  <ramana.radhakrishnan@arm.com>
 

gcc/config/aarch64/aarch64.c

@@ -11825,6 +11825,28 @@ aarch64_override_options (void)
   if (!selected_tune)
     selected_tune = selected_cpu;
 
+  if (aarch64_enable_bti == 2)
+    {
+#ifdef TARGET_ENABLE_BTI
+      aarch64_enable_bti = 1;
+#else
+      aarch64_enable_bti = 0;
+#endif
+    }
+
+  /* Return address signing is currently not supported for ILP32 targets.  For
+     LP64 targets use the configured option in the absence of a command-line
+     option for -mbranch-protection.  */
+  if (!TARGET_ILP32 && accepted_branch_protection_string == NULL)
+    {
+#ifdef TARGET_ENABLE_PAC_RET
+      aarch64_ra_sign_scope = AARCH64_FUNCTION_NON_LEAF;
+      aarch64_ra_sign_key = AARCH64_KEY_A;
+#else
+      aarch64_ra_sign_scope = AARCH64_FUNCTION_NONE;
+#endif
+    }
+
 #ifndef HAVE_AS_MABI_OPTION
   /* The compiler may have been configured with 2.23.* binutils, which does
      not have support for ILP32.  */

gcc/configure

@@ -979,6 +979,7 @@ with_plugin_ld
 enable_gnu_indirect_function
 enable_initfini_array
 enable_comdat
+enable_standard_branch_protection
 enable_fix_cortex_a53_835769
 enable_fix_cortex_a53_843419
 with_glibc_version
@@ -1708,6 +1709,14 @@ Optional Features:
   --enable-initfini-array	use .init_array/.fini_array sections
   --enable-comdat         enable COMDAT group support
 
+  --enable-standard-branch-protection
+                          enable Branch Target Identification Mechanism and
+                          Return Address Signing by default for AArch64
+  --disable-standard-branch-protection
+                          disable Branch Target Identification Mechanism and
+                          Return Address Signing by default for AArch64
+
+
   --enable-fix-cortex-a53-835769
                           enable workaround for AArch64 Cortex-A53 erratum
                           835769 by default
@@ -25054,6 +25063,25 @@ if test $gcc_cv_as_aarch64_picreloc = yes; then
 
 $as_echo "#define HAVE_AS_SMALL_PIC_RELOCS 1" >>confdefs.h
 
+fi
+
+    # Enable Branch Target Identification Mechanism and Return Address
+    # Signing by default.
+    # Check whether --enable-standard-branch-protection was given.
+if test "${enable_standard_branch_protection+set}" = set; then :
+  enableval=$enable_standard_branch_protection;
+        case $enableval in
+          yes)
+            tm_defines="${tm_defines} TARGET_ENABLE_BTI=1 TARGET_ENABLE_PAC_RET=1"
+            ;;
+          no)
+            ;;
+          *)
+            as_fn_error "'$enableval' is an invalid value for --enable-standard-branch-protection.\
+  Valid choices are 'yes' and 'no'." "$LINENO" 5
+            ;;
+        esac
+
 fi
 
     # Enable default workaround for AArch64 Cortex-A53 erratum 835769.

gcc/configure.ac

@@ -3962,6 +3962,29 @@ case "$target" in
 	ldr     x0, [[x2, #:gotpage_lo15:globalsym]]
     ],,[AC_DEFINE(HAVE_AS_SMALL_PIC_RELOCS, 1,
 	[Define if your assembler supports relocs needed by -fpic.])])
+    # Enable Branch Target Identification Mechanism and Return Address
+    # Signing by default.
+    AC_ARG_ENABLE(standard-branch-protection,
+    [
+AS_HELP_STRING([--enable-standard-branch-protection],
+        [enable Branch Target Identification Mechanism and Return Address Signing by default for AArch64])
+AS_HELP_STRING([--disable-standard-branch-protection],
+        [disable Branch Target Identification Mechanism and Return Address Signing by default for AArch64])
+    ],
+      [
+        case $enableval in
+          yes)
+            tm_defines="${tm_defines} TARGET_ENABLE_BTI=1 TARGET_ENABLE_PAC_RET=1"
+            ;;
+          no)
+            ;;
+          *)
+            AC_MSG_ERROR(['$enableval' is an invalid value for --enable-standard-branch-protection.\
+  Valid choices are 'yes' and 'no'.])
+            ;;
+        esac
+      ],
+    [])
     # Enable default workaround for AArch64 Cortex-A53 erratum 835769.
     AC_ARG_ENABLE(fix-cortex-a53-835769,
     [

gcc/doc/install.texi

@@ -3413,6 +3413,16 @@ The workaround is disabled by default if neither of
 @option{--enable-fix-cortex-a53-843419} or
 @option{--disable-fix-cortex-a53-843419} is given at configure time.
 
+To enable Branch Target Identification Mechanism and Return Address Signing by
+default at configure time use the @option{--enable-standard-branch-protection}
+option.  This is equivalent to having @option{-mbranch-protection=standard}
+during compilation.  This can be explicitly disabled during compilation by
+passing the @option{-mbranch-protection=none} option which turns off all
+types of branch protections.  Conversely,
+@option{--disable-standard-branch-protection} will disable both the
+protections by default.  This mechanism is turned off by default if neither
+of the options are given at configure time.
+
 @html
 <hr />
 @end html

gcc/testsuite/ChangeLog

@@ -1,3 +1,12 @@
+2018-01-09  Sudakshina Das  <sudi.das@arm.com>
+
+	* gcc.target/aarch64/bti-1.c: Update test to not add command line
+	option when configure with bti.
+	* gcc.target/aarch64/bti-2.c: Likewise.
+	* lib/target-supports.exp
+	(check_effective_target_default_branch_protection):
+	Add configure check for --enable-standard-branch-protection.
+
 2018-01-09  Sudakshina Das  <sudi.das@arm.com>
 
 	* gcc.target/aarch64/bti-1.c: New test.

gcc/testsuite/gcc.target/aarch64/bti-1.c

@@ -1,6 +1,9 @@
 /* { dg-do compile } */
 /* -Os to create jump table.  */
-/* { dg-options "-Os -mbranch-protection=standard" } */
+/* { dg-options "-Os" } */
+/* If configured with --enable-standard-branch-protection, don't use
+   command line option.  */
+/* { dg-additional-options "-mbranch-protection=standard" { target { ! default_branch_protection } } } */
 
 extern int f1 (void);
 extern int f2 (void);

gcc/testsuite/gcc.target/aarch64/bti-2.c

@@ -1,6 +1,8 @@
 /* { dg-do run } */
 /* { dg-require-effective-target aarch64_bti_hw } */
-/* { dg-options "-mbranch-protection=standard" } */
+/* If configured with --enable-standard-branch-protection, don't use
+   command line option.  */
+/* { dg-additional-options "-mbranch-protection=standard" { target { ! default_branch_protection } } } */
 
 #include<stdio.h>
 

gcc/testsuite/lib/target-supports.exp

@@ -4329,6 +4329,11 @@ proc check_effective_target_aarch64_bti_hw { } {
     } "-O2" ]
 }
 
+# Return 1 if GCC was configured with --enable-standard-branch-protection
+proc check_effective_target_default_branch_protection { } {
+    return [check_configured_with "enable-standard-branch-protection"]
+}
+
 # Return 1 if the target supports the ARMv8.1 Adv.SIMD extension, 0
 # otherwise.  The test is valid for AArch64 and ARM.  Record the command
 # line options needed.