From 6d1f97bb0667e35cbb4e656516b0b5f48afcabde Mon Sep 17 00:00:00 2001
From: Yury Khrustalev <yury.khrustalev@arm.com>
Date: Tue, 28 Jan 2025 16:13:51 +0000
Subject: [PATCH] aarch64: Add configure checks for GCS support

 - Add check that linker supports -z gcs=...
 - Add checks that main and test compiler support
   -mbranch-protection=gcs

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
---
 configure    | 99 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 configure.ac | 17 +++++++++
 2 files changed, 116 insertions(+)

diff --git a/configure b/configure
index eb8abd0054..8fd09c6d88 100755
--- a/configure
+++ b/configure
@@ -8908,6 +8908,105 @@ printf "%s\n" "$libc_linker_feature" >&6; }
 config_vars="$config_vars
 load-address-ldflag = $libc_cv_load_address_ldflag"
 
+# Check if compilers support GCS in branch protection:
+
+
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking if compiler supports -mbranch-protection=gcs" >&5
+printf %s "checking if compiler supports -mbranch-protection=gcs... " >&6; }
+if test ${libc_cv_cc_gcs+y}
+then :
+  printf %s "(cached) " >&6
+else case e in #(
+  e) if { ac_try='${CC-cc} -Werror -mbranch-protection=gcs -xc /dev/null -S -o /dev/null'
+  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; }
+then :
+  libc_cv_cc_gcs=yes
+else case e in #(
+  e) libc_cv_cc_gcs=no ;;
+esac
+fi ;;
+esac
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $libc_cv_cc_gcs" >&5
+printf "%s\n" "$libc_cv_cc_gcs" >&6; }
+if test "$TEST_CC" = "$CC"; then
+  libc_cv_test_cc_gcs=$libc_cv_cc_gcs
+else
+
+saved_CC="$CC"
+CC="$TEST_CC"
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking if compiler supports -mbranch-protection=gcs in testing" >&5
+printf %s "checking if compiler supports -mbranch-protection=gcs in testing... " >&6; }
+if test ${libc_cv_test_cc_gcs+y}
+then :
+  printf %s "(cached) " >&6
+else case e in #(
+  e) if { ac_try='${CC-cc} -Werror -mbranch-protection=gcs -xc /dev/null -S -o /dev/null'
+  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; }
+then :
+  libc_cv_test_cc_gcs=yes
+else case e in #(
+  e) libc_cv_test_cc_gcs=no ;;
+esac
+fi ;;
+esac
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $libc_cv_test_cc_gcs" >&5
+printf "%s\n" "$libc_cv_test_cc_gcs" >&6; }
+
+CC="$saved_CC"
+
+fi
+
+config_vars="$config_vars
+have-cc-gcs = $libc_cv_cc_gcs"
+config_vars="$config_vars
+have-test-cc-gcs = $libc_cv_test_cc_gcs"
+
+# Check if linker supports GCS marking
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for linker that supports -z gcs=always" >&5
+printf %s "checking for linker that supports -z gcs=always... " >&6; }
+libc_linker_feature=no
+cat > conftest.c <<EOF
+int _start (void) { return 42; }
+EOF
+if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp
+		  -Wl,-z,gcs=always -nostdlib -nostartfiles
+		  -fPIC -shared -o conftest.so conftest.c
+		  1>&5'
+  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; }
+then
+  if ${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp -Wl,-z,gcs=always -nostdlib \
+      -nostartfiles -fPIC -shared -o conftest.so conftest.c 2>&1 \
+      | grep "warning: -z gcs=always ignored" > /dev/null 2>&1; then
+    true
+  else
+    libc_linker_feature=yes
+  fi
+fi
+rm -f conftest*
+if test $libc_linker_feature = yes; then
+  libc_cv_ld_gcs=yes
+else
+  libc_cv_ld_gcs=no
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $libc_linker_feature" >&5
+printf "%s\n" "$libc_linker_feature" >&6; }
+config_vars="$config_vars
+have-ld-gcs = $libc_cv_ld_gcs"
+
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking if we can build programs as PIE" >&5
 printf %s "checking if we can build programs as PIE... " >&6; }
 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
diff --git a/configure.ac b/configure.ac
index 050bfa65e3..d4ef0c4243 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1992,6 +1992,23 @@ LIBC_LINKER_FEATURE([-Ttext-segment=$libc_cv_pde_load_address],
 		    [libc_cv_load_address_ldflag=])
 LIBC_CONFIG_VAR([load-address-ldflag], [$libc_cv_load_address_ldflag])
 
+# Check if compilers support GCS in branch protection:
+LIBC_TRY_CC_AND_TEST_CC_OPTION([if compiler supports -mbranch-protection=gcs],
+  [-Werror -mbranch-protection=gcs],
+  libc_cv_cc_gcs,
+  [libc_cv_cc_gcs=yes],
+  [libc_cv_cc_gcs=no],
+  libc_cv_test_cc_gcs,
+  [libc_cv_test_cc_gcs=yes],
+  [libc_cv_test_cc_gcs=no])
+LIBC_CONFIG_VAR([have-cc-gcs], [$libc_cv_cc_gcs])
+LIBC_CONFIG_VAR([have-test-cc-gcs], [$libc_cv_test_cc_gcs])
+
+# Check if linker supports GCS marking
+LIBC_LINKER_FEATURE([-z gcs=always], [-Wl,-z,gcs=always],
+		    [libc_cv_ld_gcs=yes], [libc_cv_ld_gcs=no])
+LIBC_CONFIG_VAR([have-ld-gcs], [$libc_cv_ld_gcs])
+
 AC_MSG_CHECKING(if we can build programs as PIE)
 AC_COMPILE_IFELSE([AC_LANG_SOURCE([[#ifdef PIE_UNSUPPORTED
 # error PIE is not supported