This patch adds support for aarch64 gcs build attributes. This support
includes generating two new assembler directives .aeabi_subsection and
.aeabi_attribute. These directives are generated as per the syntax
mentioned in spec "Build Attributes for the Arm® 64-bit
Architecture (AArch64)" available at [1].
To check whether the assembler being used to build the toolchain
supports these directives, a new gcc configure check is added in
gcc/configure.ac.
If the assembler support these directives, .aeabi_subsection and
.aeabi_attribute directives are emitted in the generated assembly,
when -mbranch-protection=gcs is passed.
If the assembler does not support these directives,
.note.gnu.property section will emit the relevant gcs information
in the generated assembly, when -mbranch-protection=gcs is passed.
This patch needs to be applied on top of GCC gcs patch series [2].
Bootstrapped on aarch64-none-linux-gnu and regression tested on
aarch64-none-elf, no issues.
Ok for master?
Regards,
Srinath.
[1]: https://github.com/ARM-software/abi-aa/pull/230
[2]: https://gcc.gnu.org/git/?p=gcc.git;a=shortlog;h=refs/vendors/ARM/heads/gcs
gcc/ChangeLog:
2024-09-11 Srinath Parvathaneni <srinath.parvathan...@arm.com>
* config.in: Regenerated
* config/aarch64/aarch64.cc (aarch64_emit_aeabi_attribute): New
function declaration.
(aarch64_emit_aeabi_subsection): Likewise.
(aarch64_start_file): Emit gcs build attributes.
(aarch64_file_end_indicate_exec_stack): Update gcs bit in
note.gnu.property section.
* configure: Regenerated.
* configure.ac: Add gcc configure check.
gcc/testsuite/ChangeLog:
2024-09-11 Srinath Parvathaneni <srinath.parvathan...@arm.com>
* gcc.target/aarch64/build-attribute-gcs.c: New test.
---
gcc/config.in | 6 +++
gcc/config/aarch64/a.out | Bin 0 -> 656 bytes
gcc/config/aarch64/aarch64.cc | 43 ++++++++++++++++++
gcc/configure | 35 ++++++++++++++
gcc/configure.ac | 7 +++
.../gcc.target/aarch64/build-attribute-gcs.c | 24 ++++++++++
6 files changed, 115 insertions(+)
create mode 100644 gcc/config/aarch64/a.out
create mode 100644 gcc/testsuite/gcc.target/aarch64/build-attribute-gcs.c
diff --git a/gcc/config.in b/gcc/config.in
index 7fcabbe5061..eb6024dfc90 100644
--- a/gcc/config.in
+++ b/gcc/config.in
@@ -379,6 +379,12 @@
#endif
+/* Define if your assembler supports gcs build attributes. */
+#ifndef USED_FOR_TARGET
+#undef HAVE_AS_BUILD_ATTRIBUTES_GCS
+#endif
+
+
/* Define to the level of your assembler's compressed debug section support.
*/
#ifndef USED_FOR_TARGET
diff --git a/gcc/config/aarch64/a.out b/gcc/config/aarch64/a.out
new file mode 100644
index 0000000000000000000000000000000000000000..dd7982f2db625be166d33548dc5d00c7e7601629
GIT binary patch
literal 656
zcmb<-^>JfjWMqH=MuzPS2p&w7f#Cvz$>0EHJ20>_upx<JGMTZO#K6GJz=Ww7D8dYc
zm_V<%GPfi#i9xTpqzFQ1z*r@z6(tOMDTyVC40=h$#h7|Y7m)^P0r?-@XAU@wLJuoN
zsD5;x5UXDusGkFf$<+^X54O;S*`ENE2LV<fW&vW5T_7L<p%^%UG`ig&sRbYc2+;kD
W&KCr#!KQy9ST_TM4wQyb==uS05EWhk
literal 0
HcmV?d00001
diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index 8709f2b0cfb..2cff5317fc1 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -24679,6 +24679,33 @@ aarch64_post_cfi_startproc (FILE *f, tree ignored ATTRIBUTE_UNUSED)
asm_fprintf (f, "\t.cfi_b_key_frame\n");
}
+/* This function is used to emit an AEABI attribute with tag and its associated
+ value. We emit the numerical value of the tag and the textual tags as
+ comment so that anyone reading the assembler output will know which tag is
+ being set.
+ example: .aeabi_attribute 3, 1 // Tag_Feature_GCS */
+
+void
+aarch64_emit_aeabi_attribute (const char *name, uint8_t num, uint8_t val)
+{
+ asm_fprintf (asm_out_file, "\t.aeabi_attribute %u, %u", num, val);
+ if (flag_debug_asm)
+ asm_fprintf (asm_out_file, "\t%s %s", ASM_COMMENT_START, name);
+ asm_fprintf (asm_out_file, "\n");
+}
+
+/* This function is used to emit an AEABI subsection with vendor name,
+ optional status and value type.
+ example: .aeabi_subsection .aeabi-feature-and-bits, 1, 0 */
+
+void
+aarch64_emit_aeabi_subsection (const char *name, uint8_t num, uint8_t val)
+{
+ asm_fprintf (asm_out_file, "\t.aeabi_subsection %s, %u, %u\n",
+ name, num, val);
+}
+
+
/* Implements TARGET_ASM_FILE_START. Output the assembly header. */
static void
@@ -24699,6 +24726,20 @@ aarch64_start_file (void)
asm_fprintf (asm_out_file, "\t.arch %s\n",
aarch64_last_printed_arch_string.c_str ());
+/* Emit gcs build attributes only when building a native AArch64-hosted
+ compiler. */
+#if defined(__aarch64__)
+ /* Check the current assembly supports gcs build attributes, if not
+ fallback to .note.gnu.property section. */
+ #ifdef HAVE_AS_BUILD_ATTRIBUTES_GCS
+ if (aarch64_gcs_enabled ())
+ {
+ aarch64_emit_aeabi_subsection (".aeabi-feature-and-bits", 1, 0);
+ aarch64_emit_aeabi_attribute ("Tag_Feature_GCS", 3, 1);
+ }
+ #endif
+#endif
+
default_file_start ();
}
@@ -29105,8 +29146,10 @@ aarch64_file_end_indicate_exec_stack ()
if (aarch_ra_sign_scope != AARCH_FUNCTION_NONE)
feature_1_and |= GNU_PROPERTY_AARCH64_FEATURE_1_PAC;
+#ifndef HAVE_AS_BUILD_ATTRIBUTES_GCS
if (aarch64_gcs_enabled ())
feature_1_and |= GNU_PROPERTY_AARCH64_FEATURE_1_GCS;
+#endif
if (feature_1_and)
{
diff --git a/gcc/configure b/gcc/configure
index ec6124cb361..bec606f61b3 100755
--- a/gcc/configure
+++ b/gcc/configure
@@ -28036,6 +28036,41 @@ if test $gcc_cv_as_aarch64_picreloc = yes; then
$as_echo "#define HAVE_AS_SMALL_PIC_RELOCS 1" >>confdefs.h
+fi
+
+ # Check if we have binutils support for gcs build attributes.
+ { $as_echo "$as_me:${as_lineno-$LINENO}: checking assembler for gcs build attributes support" >&5
+$as_echo_n "checking assembler for gcs build attributes support... " >&6; }
+if ${gcc_cv_as_aarch64_gcs_build_attributes+:} false; then :
+ $as_echo_n "(cached) " >&6
+else
+ gcc_cv_as_aarch64_gcs_build_attributes=no
+ if test x$gcc_cv_as != x; then
+ $as_echo '
+ .aeabi_subsection .aeabi-feature-and-bits, 1, 0
+ .aeabi_attribute 3, 1
+ ' > conftest.s
+ if { ac_try='$gcc_cv_as $gcc_cv_as_flags -o conftest.o conftest.s >&5'
+ { { eval echo "\"\$as_me\":${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
+ gcc_cv_as_aarch64_gcs_build_attributes=yes
+ else
+ echo "configure: failed program was" >&5
+ cat conftest.s >&5
+ fi
+ rm -f conftest.o conftest.s
+ fi
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $gcc_cv_as_aarch64_gcs_build_attributes" >&5
+$as_echo "$gcc_cv_as_aarch64_gcs_build_attributes" >&6; }
+if test $gcc_cv_as_aarch64_gcs_build_attributes = yes; then
+
+$as_echo "#define HAVE_AS_BUILD_ATTRIBUTES_GCS 1" >>confdefs.h
+
fi
# Enable Branch Target Identification Mechanism and Return Address
diff --git a/gcc/configure.ac b/gcc/configure.ac
index d0b9865fc91..51b07417153 100644
--- a/gcc/configure.ac
+++ b/gcc/configure.ac
@@ -4388,6 +4388,13 @@ case "$target" in
ldr x0, [[x2, #:gotpage_lo15:globalsym]]
],,[AC_DEFINE(HAVE_AS_SMALL_PIC_RELOCS, 1,
[Define if your assembler supports relocs needed by -fpic.])])
+ # Check if we have binutils support for gcs build attributes.
+ gcc_GAS_CHECK_FEATURE([gcs build attributes support], gcc_cv_as_aarch64_gcs_build_attributes,,
+ [
+ .aeabi_subsection .aeabi-feature-and-bits, 1, 0
+ .aeabi_attribute 3, 1
+ ],,[AC_DEFINE(HAVE_AS_BUILD_ATTRIBUTES_GCS, 1,
+ [Define if your assembler supports gcs build attributes.])])
# Enable Branch Target Identification Mechanism and Return Address
# Signing by default.
AC_ARG_ENABLE(standard-branch-protection,
diff --git a/gcc/testsuite/gcc.target/aarch64/build-attribute-gcs.c b/gcc/testsuite/gcc.target/aarch64/build-attribute-gcs.c
new file mode 100644
index 00000000000..eb15772757e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/build-attribute-gcs.c
@@ -0,0 +1,24 @@
+/* { dg-do compile { target aarch64*-*-linux* } } */
+
+int main()
+{
+ return 0;
+}
+
+/* { dg-options "-mbranch-protection=gcs" } */
+/* { dg-final { scan-assembler-not "\.aeabi_subsection \.aeabi-feature-and-bits, 1, 0" } } */
+/* { dg-final { scan-assembler-not "\.aeabi_attribute 3, 1\t\/\/ Tag_Feature_GCS" } } */
+/* { dg-final { scan-assembler ".note.gnu.property" } } */
+
+/* { dg-options "-mbranch-protection=bti" } */
+/* { dg-final { scan-assembler ".note.gnu.property" } } */
+
+
+/* { dg-options "-mbranch-protection=pac-ret" } */
+/* { dg-final { scan-assembler ".note.gnu.property" } } */
+
+
+/* { dg-options "-mbranch-protection=standard" } */
+/* { dg-final { scan-assembler-not "\.aeabi_subsection \.aeabi-feature-and-bits, 1, 0" } } */
+/* { dg-final { scan-assembler-not "\.aeabi_attribute 3, 1\t\/\/ Tag_Feature_GCS" } } */
+/* { dg-final { scan-assembler ".note.gnu.property" } } */
