[gcc(refs/vendors/ARM/heads/gcs-13)] aarch64: Add -mbranch-protection=gcs option

[gcc(refs/vendors/ARM/heads/gcs-13)] aarch64: Add -mbranch-protection=gcs option

[Szabolcs Nagy]

https://gcc.gnu.org/g:218fc0f90a84a06998fa770983b75e4c1dfa8ed3

commit 218fc0f90a84a06998fa770983b75e4c1dfa8ed3
Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date:   Mon Jun 19 12:57:56 2023 +0100

    aarch64: Add -mbranch-protection=gcs option
    
    This enables Guarded Control Stack (GCS) compatible code generation.
    
    The "standard" branch-protection type enables it, and the default
    depends on the compiler default.
    
    TODO: gcs compatibility marking is missing.
    
    gcc/ChangeLog:
    
            * config/aarch64/aarch64-protos.h (aarch_gcs_enabled): Declare.
            * config/aarch64/aarch64.cc (aarch_gcs_enabled): Define.
            (aarch_handle_no_branch_protection): Handle gcs.
            (aarch_handle_standard_branch_protection): Handle gcs.
            (aarch_handle_gcs_protection): New.
            * config/aarch64/aarch64.opt: Add aarch_enable_gcs.
            * configure: Regenerate.
            * configure.ac: Handle gcs in --enable-standard-branch-protection.
            * doc/invoke.texi: Document -mbranch-protection=gcs.

Diff:
---
 gcc/config/aarch64/aarch64-protos.h |  2 ++
 gcc/config/aarch64/aarch64.cc       | 24 ++++++++++++++++++++++++
 gcc/config/aarch64/aarch64.opt      |  3 +++
 gcc/configure                       |  2 +-
 gcc/configure.ac                    |  2 +-
 gcc/doc/invoke.texi                 |  5 +++--
 6 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/gcc/config/aarch64/aarch64-protos.h b/gcc/config/aarch64/aarch64-protos.h
index 7be51ea6f56c..f893b86ab05b 100644
--- a/gcc/config/aarch64/aarch64-protos.h
+++ b/gcc/config/aarch64/aarch64-protos.h
@@ -1066,4 +1066,6 @@ extern bool aarch64_harden_sls_blr_p (void);
 
 extern void aarch64_output_patchable_area (unsigned int, bool);
 
+extern bool aarch64_gcs_enabled ();
+
 #endif /* GCC_AARCH64_PROTOS_H */
diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index 6f02fed539c9..ffc3b4d00b34 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -9042,6 +9042,13 @@ aarch_bti_j_insn_p (rtx_insn *insn)
   return GET_CODE (pat) == UNSPEC_VOLATILE && XINT (pat, 1) == UNSPECV_BTI_J;
 }
 
+/* Return TRUE if Guarded Control Stack is enabled.  */
+bool
+aarch64_gcs_enabled (void)
+{
+  return (aarch64_enable_gcs == 1);
+}
+
 /* Check if X (or any sub-rtx of X) is a PACIASP/PACIBSP instruction.  */
 bool
 aarch_pac_insn_p (rtx x)
@@ -18344,6 +18351,7 @@ aarch64_handle_no_branch_protection (void)
 {
   aarch_ra_sign_scope = AARCH_FUNCTION_NONE;
   aarch_enable_bti = 0;
+  aarch64_enable_gcs = 0;
 }
 
 static void
@@ -18352,6 +18360,7 @@ aarch64_handle_standard_branch_protection (void)
   aarch_ra_sign_scope = AARCH_FUNCTION_NON_LEAF;
   aarch64_ra_sign_key = AARCH64_KEY_A;
   aarch_enable_bti = 1;
+  aarch64_enable_gcs = 1;
 }
 
 static void
@@ -18378,6 +18387,11 @@ aarch64_handle_bti_protection (void)
 {
   aarch_enable_bti = 1;
 }
+static void
+aarch64_handle_gcs_protection (void)
+{
+  aarch64_enable_gcs = 1;
+}
 
 static const struct aarch_branch_protect_type aarch64_pac_ret_subtypes[] = {
   { "leaf", false, aarch64_handle_pac_ret_leaf, NULL, 0 },
@@ -18392,6 +18406,7 @@ static const struct aarch_branch_protect_type aarch64_branch_protect_types[] =
   { "pac-ret", false, aarch64_handle_pac_ret_protection,
     aarch64_pac_ret_subtypes, ARRAY_SIZE (aarch64_pac_ret_subtypes) },
   { "bti", false, aarch64_handle_bti_protection, NULL, 0 },
+  { "gcs", false, aarch64_handle_gcs_protection, NULL, 0 },
   { NULL, false, NULL, NULL, 0 }
 };
 
@@ -18481,6 +18496,15 @@ aarch64_override_options (void)
 #endif
     }
 
+  if (aarch64_enable_gcs == 2)
+    {
+#ifdef TARGET_ENABLE_GCS
+      aarch64_enable_gcs = 1;
+#else
+      aarch64_enable_gcs = 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.  */
diff --git a/gcc/config/aarch64/aarch64.opt b/gcc/config/aarch64/aarch64.opt
index 137e506fe198..1ec7017b4326 100644
--- a/gcc/config/aarch64/aarch64.opt
+++ b/gcc/config/aarch64/aarch64.opt
@@ -39,6 +39,9 @@ aarch64_feature_flags aarch64_isa_flags = 0
 TargetVariable
 unsigned aarch_enable_bti = 2
 
+TargetVariable
+unsigned aarch64_enable_gcs = 2
+
 TargetVariable
 enum aarch64_key_type aarch64_ra_sign_key = AARCH64_KEY_A
 
diff --git a/gcc/configure b/gcc/configure
index dec2eca1a453..661c17c5adfa 100755
--- a/gcc/configure
+++ b/gcc/configure
@@ -26344,7 +26344,7 @@ 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"
+            tm_defines="${tm_defines} TARGET_ENABLE_BTI=1 TARGET_ENABLE_PAC_RET=1 TARGET_ENABLE_GCS=1"
             ;;
           no)
             ;;
diff --git a/gcc/configure.ac b/gcc/configure.ac
index c0d067ec2716..c4be3713e930 100644
--- a/gcc/configure.ac
+++ b/gcc/configure.ac
@@ -4379,7 +4379,7 @@ AS_HELP_STRING([--disable-standard-branch-protection],
       [
         case $enableval in
           yes)
-            tm_defines="${tm_defines} TARGET_ENABLE_BTI=1 TARGET_ENABLE_PAC_RET=1"
+            tm_defines="${tm_defines} TARGET_ENABLE_BTI=1 TARGET_ENABLE_PAC_RET=1 TARGET_ENABLE_GCS=1"
             ;;
           no)
             ;;
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index b777fc927551..e77338e4bd13 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -774,7 +774,7 @@ Objective-C and Objective-C++ Dialects}.
 -mpc-relative-literal-loads
 -msign-return-address=@var{scope}
 -mbranch-protection=@var{none}|@var{standard}|@var{pac-ret}[+@var{leaf}
-+@var{b-key}]|@var{bti}
++@var{b-key}]|@var{bti}|@var{gcs}
 -mharden-sls=@var{opts}
 -march=@var{name}  -mcpu=@var{name}  -mtune=@var{name}
 -moverride=@var{string}  -mverbose-cost-dump
@@ -20418,7 +20418,7 @@ default value is @samp{none}. This option has been deprecated by
 -mbranch-protection.
 
 @opindex mbranch-protection
-@item -mbranch-protection=@var{none}|@var{standard}|@var{pac-ret}[+@var{leaf}+@var{b-key}]|@var{bti}
+@item -mbranch-protection=@var{none}|@var{standard}|@var{pac-ret}[+@var{leaf}+@var{b-key}]|@var{bti}|@var{gcs}
 Select the branch protection features to use.
 @samp{none} is the default and turns off all types of branch protection.
 @samp{standard} turns on all types of branch protection features.  If a feature
@@ -20431,6 +20431,7 @@ argument @samp{leaf} can be used to extend the signing to include leaf
 functions.  The optional argument @samp{b-key} can be used to sign the functions
 with the B-key instead of the A-key.
 @samp{bti} turns on branch target identification mechanism.
+@samp{gcs} turns on guarded control stack compatible code generation.
 
 @opindex mharden-sls
 @item -mharden-sls=@var{opts}