[PATCH v3 1/4] aarch64: add configure checks for BTI support

[Yury Khrustalev]

---
 sysdeps/aarch64/configure    | 144 +++++++++++++++++++++++++++++++++++
 sysdeps/aarch64/configure.ac |  36 +++++++++
 2 files changed, 180 insertions(+)

diff --git a/sysdeps/aarch64/configure b/sysdeps/aarch64/configure
index eecdd324b2..44b833ea1d 100755
--- a/sysdeps/aarch64/configure
+++ b/sysdeps/aarch64/configure
@@ -196,6 +196,150 @@ fi
 
 libc_cv_support_sframe=yes
 
+# Check if compilers support BTI in branch protection:
+
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking if compiler supports -mbranch-protection=bti" >&5
+printf %s "checking if compiler supports -mbranch-protection=bti... " >&6; }
+if test ${libc_cv_cc_bti+y}
+then :
+  printf %s "(cached) " >&6
+else case e in #(
+  e) if { ac_try='${CC-cc} -Werror -mbranch-protection=bti -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 $ac_status = 0; }; }
+then :
+  libc_cv_cc_bti=yes
+else case e in #(
+  e) libc_cv_cc_bti=no ;;
+esac
+fi ;;
+esac
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $libc_cv_cc_bti" >&5
+printf "%s\n" "$libc_cv_cc_bti" >&6; }
+if test "$TEST_CC" = "$CC"; then
+  libc_cv_test_cc_bti=$libc_cv_cc_bti
+else
+
+saved_CC="$CC"
+CC="$TEST_CC"
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking if compiler supports -mbranch-protection=bti in testing" >&5
+printf %s "checking if compiler supports -mbranch-protection=bti in testing... " >&6; }
+if test ${libc_cv_test_cc_bti+y}
+then :
+  printf %s "(cached) " >&6
+else case e in #(
+  e) if { ac_try='${CC-cc} -Werror -mbranch-protection=bti -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 $ac_status = 0; }; }
+then :
+  libc_cv_test_cc_bti=yes
+else case e in #(
+  e) libc_cv_test_cc_bti=no
+ ;;
+esac
+fi ;;
+esac
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $libc_cv_test_cc_bti" >&5
+printf "%s\n" "$libc_cv_test_cc_bti" >&6; }
+
+CC="$saved_CC"
+
+fi
+
+
+# Check if linker supports BTI marking
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for linker that supports -z force-bti" >&5
+printf %s "checking for linker that supports -z force-bti... " >&6; }
+libc_linker_feature=no
+cat > conftest.c <<EOF
+int _start (void) { return 42; }
+EOF
+if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp
+		  -Wl,-z,force-bti -nostdlib -nostartfiles
+		  -fPIC -shared -o conftest.so conftest.c
+		  1>&5'
+  { { eval echo "\"\$as_me\":${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,force-bti -nostdlib \
+      -nostartfiles -fPIC -shared -o conftest.so conftest.c 2>&1 \
+      | grep "warning: -z force-bti ignored" > /dev/null 2>&1; then
+    true
+  else
+    libc_linker_feature=yes
+  fi
+fi
+rm -f conftest*
+if test $libc_linker_feature = yes; then
+  libc_cv_ld_bti=yes
+else
+  libc_cv_ld_bti=no
+
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $libc_linker_feature" >&5
+printf "%s\n" "$libc_linker_feature" >&6; }
+
+# Check if toolchain is enabled to support BTI
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking if toolchain is enabled to support BTI" >&5
+printf %s "checking if toolchain is enabled to support BTI... " >&6; }
+libc_elf_property=no
+cat > conftest.c <<EOF
+int foo (void) { return 42; }
+EOF
+if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS
+		  -fPIC -shared -o conftest.so conftest.c
+		  1>&5'
+  { { eval echo "\"\$as_me\":${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 { ac_try='LC_ALL=C $READELF -n --wide conftest.so | grep "AArch64 feature: .*BTI" 1>&5'
+  { { eval echo "\"\$as_me\":${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
+    libc_elf_property=yes
+  else
+    libc_elf_property=no
+  fi
+fi
+rm -f conftest*
+if test $libc_elf_property = yes; then
+  libc_cv_bti_supported=yes
+else
+  libc_cv_bti_supported=no
+
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $libc_elf_property" >&5
+printf "%s\n" "$libc_elf_property" >&6; }
+
+if test $libc_cv_cc_bti = yes && \
+  test $libc_cv_test_cc_bti = yes && \
+  test $libc_cv_ld_bti = yes && \
+  test $libc_cv_bti_supported = yes
+then
+  config_vars="$config_vars
+have-test-bti = yes"
+else
+  config_vars="$config_vars
+have-test-bti = no"
+fi
+
 # Check if compilers support GCS in branch protection:
 
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking if compiler supports -mbranch-protection=gcs" >&5
diff --git a/sysdeps/aarch64/configure.ac b/sysdeps/aarch64/configure.ac
index 8b01aa843d..b9981861f6 100644
--- a/sysdeps/aarch64/configure.ac
+++ b/sysdeps/aarch64/configure.ac
@@ -34,6 +34,42 @@ fi
 
 libc_cv_support_sframe=yes
 
+# Check if compilers support BTI in branch protection:
+LIBC_TRY_CC_AND_TEST_CC_OPTION(
+  [if compiler supports -mbranch-protection=bti],
+  [-Werror -mbranch-protection=bti],
+  libc_cv_cc_bti,
+  [libc_cv_cc_bti=yes],
+  [libc_cv_cc_bti=no],
+  libc_cv_test_cc_bti,
+  [libc_cv_test_cc_bti=yes],
+  [libc_cv_test_cc_bti=no]
+)
+
+# Check if linker supports BTI marking
+LIBC_LINKER_FEATURE(
+  [-z force-bti], [-Wl,-z,force-bti],
+  [libc_cv_ld_bti=yes], [libc_cv_ld_bti=no]
+)
+
+# Check if toolchain is enabled to support BTI
+LIBC_CHECK_ELF_PROPERTY(
+  [if toolchain is enabled to support BTI],
+  [AArch64 feature: .*BTI],
+  [libc_cv_bti_supported=yes],
+  [libc_cv_bti_supported=no]
+)
+
+if test $libc_cv_cc_bti = yes && \
+  test $libc_cv_test_cc_bti = yes && \
+  test $libc_cv_ld_bti = yes && \
+  test $libc_cv_bti_supported = yes
+then
+  LIBC_CONFIG_VAR([have-test-bti], [yes])
+else
+  LIBC_CONFIG_VAR([have-test-bti], [no])
+fi
+
 # Check if compilers support GCS in branch protection:
 LIBC_TRY_CC_AND_TEST_CC_OPTION(
   [if compiler supports -mbranch-protection=gcs],
-- 
2.47.3