diff mbox series

[v3,04/13] aarch64: configure test for BTI support

Message ID c904e0926acc59bb73e1c46b5d3c799a5a330d72.1589552054.git.szabolcs.nagy@arm.com
State Superseded
Headers show
Series aarch64: branch protection support | expand

Commit Message

Szabolcs Nagy May 15, 2020, 2:40 p.m. UTC
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.
---
 config.h.in                  |  3 +++
 sysdeps/aarch64/configure    | 42 ++++++++++++++++++++++++++++++++++++
 sysdeps/aarch64/configure.ac | 19 ++++++++++++++++
 3 files changed, 64 insertions(+)

Comments

Adhemerval Zanella May 25, 2020, 6:41 p.m. UTC | #1
On 15/05/2020 11:40, Szabolcs Nagy wrote:
> 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.

From the configure check below I understand that it still possible to
build a glibc with BTI support if the required flags are add on 
CC or CFLAGS.  Maybe make it explicit in the commit message?

LGTM, thanks.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
>  config.h.in                  |  3 +++
>  sysdeps/aarch64/configure    | 42 ++++++++++++++++++++++++++++++++++++
>  sysdeps/aarch64/configure.ac | 19 ++++++++++++++++
>  3 files changed, 64 insertions(+)
> 
> diff --git a/config.h.in b/config.h.in
> index dea43df438..506b0c416c 100644
> --- a/config.h.in
> +++ b/config.h.in
> @@ -109,6 +109,9 @@
>  /* AArch64 big endian ABI */
>  #undef HAVE_AARCH64_BE
>  
> +/* AArch64 BTI support enabled.  */
> +#undef HAVE_AARCH64_BTI
> +
>  /* C-SKY ABI version.  */
>  #undef CSKYABI
>  

Ok.

> diff --git a/sysdeps/aarch64/configure b/sysdeps/aarch64/configure
> index 5bd355a691..70477a7fa5 100644
> --- a/sysdeps/aarch64/configure
> +++ b/sysdeps/aarch64/configure
> @@ -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
> diff --git a/sysdeps/aarch64/configure.ac b/sysdeps/aarch64/configure.ac
> index 7851dd4dac..798f494740 100644
> --- a/sysdeps/aarch64/configure.ac
> +++ b/sysdeps/aarch64/configure.ac
> @@ -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.

Maybe add that user might still set it on CC or CFLAGS?

> +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
> 

Ok.
Adhemerval Zanella May 25, 2020, 6:48 p.m. UTC | #2
On 25/05/2020 15:41, Adhemerval Zanella wrote:
> 
> 
> On 15/05/2020 11:40, Szabolcs Nagy wrote:
>> 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.
> 
> From the configure check below I understand that it still possible to
> build a glibc with BTI support if the required flags are add on 
> CC or CFLAGS.  Maybe make it explicit in the commit message?
> 
> LGTM, thanks.
> 
> Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
> 
>> ---
>>  config.h.in                  |  3 +++
>>  sysdeps/aarch64/configure    | 42 ++++++++++++++++++++++++++++++++++++
>>  sysdeps/aarch64/configure.ac | 19 ++++++++++++++++
>>  3 files changed, 64 insertions(+)
>>
>> diff --git a/config.h.in b/config.h.in
>> index dea43df438..506b0c416c 100644
>> --- a/config.h.in
>> +++ b/config.h.in
>> @@ -109,6 +109,9 @@
>>  /* AArch64 big endian ABI */
>>  #undef HAVE_AARCH64_BE
>>  
>> +/* AArch64 BTI support enabled.  */
>> +#undef HAVE_AARCH64_BTI
>> +
>>  /* C-SKY ABI version.  */
>>  #undef CSKYABI
>>  
> 
> Ok.

In fact I think you can define as:

  #define HAVE_AARCH64_BTI  0

That AC_DEFINE will correctly set to 1.  It allows to check for the
macro value instead of existence.
diff mbox series

Patch

diff --git a/config.h.in b/config.h.in
index dea43df438..506b0c416c 100644
--- a/config.h.in
+++ b/config.h.in
@@ -109,6 +109,9 @@ 
 /* AArch64 big endian ABI */
 #undef HAVE_AARCH64_BE
 
+/* AArch64 BTI support enabled.  */
+#undef HAVE_AARCH64_BTI
+
 /* C-SKY ABI version.  */
 #undef CSKYABI
 
diff --git a/sysdeps/aarch64/configure b/sysdeps/aarch64/configure
index 5bd355a691..70477a7fa5 100644
--- a/sysdeps/aarch64/configure
+++ b/sysdeps/aarch64/configure
@@ -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
diff --git a/sysdeps/aarch64/configure.ac b/sysdeps/aarch64/configure.ac
index 7851dd4dac..798f494740 100644
--- a/sysdeps/aarch64/configure.ac
+++ b/sysdeps/aarch64/configure.ac
@@ -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