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aarch64: configure test for BTI support

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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.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
This commit is contained in:
Szabolcs Nagy 2020-05-06 20:22:16 +01:00
parent dbfefbdc3a
commit 1b0a4f58f5
3 changed files with 64 additions and 0 deletions
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3
config.h.in
View File

@ -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

42
sysdeps/aarch64/configure vendored
View File

@ -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

19
sysdeps/aarch64/configure.ac
View File

@ -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