diff mbox series

[v1] aarch64: Add GCS build attributes support.

Message ID 20240911155009.1343113-1-srinath.parvathaneni@arm.com
State New
Headers show
Series [v1] aarch64: Add GCS build attributes support. | expand

Commit Message

Srinath Parvathaneni Sept. 11, 2024, 3:50 p.m. UTC 
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.parvathaneni@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.parvathaneni@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

Comments

Kyrylo Tkachov Sept. 12, 2024, 7:59 a.m. UTC | #1 
Hi Srinath,
Not a full review, just some things that popped out to me.

> On 11 Sep 2024, at 17:50, Srinath Parvathaneni <srinath.parvathaneni@arm.com> wrote:
> 
> External email: Use caution opening links or attachments
> 
> 
> 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.parvathaneni@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.parvathaneni@arm.com>
> 
>        * gcc.target/aarch64/build-attribute-gcs.c: New test.
> ---
> gcc/config.in                                 |   6 +++
> gcc/config/aarch64/a.out                      | Bin 0 -> 656 bytes

This binary artifact shouldn’t be in the patch.



> 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/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" } } */


These scans should be in different tests compiled with different options.
You can’t have multiple dg-options directives in a single test and scanning for “.note.gnu.property” multiple times in a single test is redundant too.

Thanks,
Kyrill
Eric Gallager Sept. 12, 2024, 2:43 p.m. UTC | #2 
On Wed, Sep 11, 2024 at 11:51 AM Srinath Parvathaneni
<srinath.parvathaneni@arm.com> wrote:
>
> This patch adds support for aarch64 gcs build attributes.

Hi, just wondering if you could clarify what "GCS" stands for in this
context? When I see it, my first thought is "GNU Coding Standards",
but I don't think that's right...

> 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.parvathaneni@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.parvathaneni@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
>
Kyrylo Tkachov Oct. 1, 2024, 7:41 a.m. UTC | #3 
> On 12 Sep 2024, at 16:43, Eric Gallager <egall@gwmail.gwu.edu> wrote:
> 
> 
> 
> On Wed, Sep 11, 2024 at 11:51 AM Srinath Parvathaneni
> <srinath.parvathaneni@arm.com> wrote:
>> 
>> This patch adds support for aarch64 gcs build attributes.
> 
> Hi, just wondering if you could clarify what "GCS" stands for in this
> context? When I see it, my first thought is "GNU Coding Standards",
> but I don't think that's right...

It’s the Guarded Control Stack feature of the Arm architecture:
https://community.arm.com/arm-community-blogs/b/architectures-and-processors-blog/posts/arm-a-profile-architecture-2022
Thanks,
Kyrill


> 
>> 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.parvathaneni@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.parvathaneni@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 mbox series

Patch

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" } } */