[v5,02/14] aarch64: configure test for BTI support
Commit Message
Check BTI support in the compiler and linker. The check also
requires READELF that understands the BTI GNU property note.
It is expected to succeed with gcc >=gcc-9 configured with
--enable-standard-branch-protection and binutils >=binutils-2.33.
Note: passing -mbranch-protection=bti in CFLAGS when building glibc
may not be enough to get a glibc that supports BTI because crtbegin*
and crtend* provided by the compiler needs to be BTI compatible too.
---
config.h.in | 3 +++
sysdeps/aarch64/configure | 42 ++++++++++++++++++++++++++++++++++++
sysdeps/aarch64/configure.ac | 19 ++++++++++++++++
3 files changed, 64 insertions(+)
@@ -109,6 +109,9 @@
/* AArch64 big endian ABI */
#undef HAVE_AARCH64_BE
+/* AArch64 BTI support enabled. */
+#define HAVE_AARCH64_BTI 0
+
/* C-SKY ABI version. */
#undef CSKYABI
@@ -172,3 +172,45 @@ else
config_vars="$config_vars
default-abi = lp64"
fi
+
+# Only consider BTI supported if -mbranch-protection=bti is
+# on by default in the compiler and the linker produces
+# binaries with GNU property notes in PT_GNU_PROPERTY segment.
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for BTI support" >&5
+$as_echo_n "checking for BTI support... " >&6; }
+if ${libc_cv_aarch64_bti+:} false; then :
+ $as_echo_n "(cached) " >&6
+else
+ cat > conftest.c <<EOF
+void foo (void) { }
+EOF
+ libc_cv_aarch64_bti=no
+ if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS -nostdlib -nostartfiles $no_ssp -shared -fPIC -o conftest.so conftest.c'
+ { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+ (eval $ac_try) 2>&5
+ ac_status=$?
+ $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+ test $ac_status = 0; }; } \
+ && { ac_try='$READELF -lW conftest.so | grep -q GNU_PROPERTY'
+ { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+ (eval $ac_try) 2>&5
+ ac_status=$?
+ $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+ test $ac_status = 0; }; } \
+ && { ac_try='$READELF -nW conftest.so | grep -q "NT_GNU_PROPERTY_TYPE_0.*AArch64 feature:.* BTI"'
+ { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+ (eval $ac_try) 2>&5
+ ac_status=$?
+ $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+ test $ac_status = 0; }; }
+ then
+ libc_cv_aarch64_bti=yes
+ fi
+ rm -rf conftest.*
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_aarch64_bti" >&5
+$as_echo "$libc_cv_aarch64_bti" >&6; }
+if test $libc_cv_aarch64_bti = yes; then
+ $as_echo "#define HAVE_AARCH64_BTI 1" >>confdefs.h
+
+fi
@@ -20,3 +20,22 @@ if test $libc_cv_aarch64_be = yes; then
else
LIBC_CONFIG_VAR([default-abi], [lp64])
fi
+
+# Only consider BTI supported if -mbranch-protection=bti is
+# on by default in the compiler and the linker produces
+# binaries with GNU property notes in PT_GNU_PROPERTY segment.
+AC_CACHE_CHECK([for BTI support], [libc_cv_aarch64_bti], [dnl
+ cat > conftest.c <<EOF
+void foo (void) { }
+EOF
+ libc_cv_aarch64_bti=no
+ if AC_TRY_COMMAND([${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS -nostdlib -nostartfiles $no_ssp -shared -fPIC -o conftest.so conftest.c]) \
+ && AC_TRY_COMMAND([$READELF -lW conftest.so | grep -q GNU_PROPERTY]) \
+ && AC_TRY_COMMAND([$READELF -nW conftest.so | grep -q "NT_GNU_PROPERTY_TYPE_0.*AArch64 feature:.* BTI"])
+ then
+ libc_cv_aarch64_bti=yes
+ fi
+ rm -rf conftest.*])
+if test $libc_cv_aarch64_bti = yes; then
+ AC_DEFINE(HAVE_AARCH64_BTI)
+fi