Re: [PATCH 4/12] arm: Add testsuite library support for PACBTI target

[Richard Earnshaw via Gcc-patches]

On 04/07/2022 15:47, Andrea Corallo wrote:

Richard Earnshaw  writes:


On 01/07/2022 14:03, Richard Earnshaw via Gcc-patches wrote:

On 28/04/2022 10:40, Andrea Corallo via Gcc-patches wrote:

Add targeting-checking entities for PACBTI in testsuite
framework.

Pre-approved with the requested changes here
>.


gcc/testsuite/ChangeLog:

* testsuite/lib/target-supports.exp:
(check_effective_target_arm_pacbti_hw): New.
* doc/sourcebuild.texi: Document arm_pacbti_hw.

Co-Authored-By: Tejas Belagod  


+proc check_effective_target_arm_pacbti_hw {} {
+    return [check_runtime arm_pacbti_hw_available {
+    __attribute__ ((naked)) int
+    main (void)
+    {
+  asm ("pac r12, lr, sp");
So the armv8-m Arm ARM says that this instruction is in the NOP
space and that it is undefined if we aren't armv8-m.main or higher.
+  asm ("mov r0, #0");
+  asm ("autg r12, lr, sp");
This isn't in the nop space, but the Arm ARM says it is
unpredictable if the extension isn't present.  Unfortunately, that
means this isn't a particularly reliable way of detecting that the
PACBTI feature is present.
However, I can't think off hand of more reliable way of testing this
since reading the feature register ID_ISAR5 is not possible when in
unprivileged mode.
So I think we'll have to live with this.
+  asm ("bx lr");
+    }
+    } ""]
OK.



Or perhaps not. The test does not try to add the right options to
enable PAC/BTI if those aren't in the default selection for the
current testsuite run.

Perhaps we also need some additional tests to work out what
architecture options to add (if any) to ensure the test will at least
assemble.


Hi Richard,
thanks for reviewing.

Wouldn't be sufficient for that to have this test compiled with
-march=armv8-m.main?


Take a look at how, for example, check_effective_target_arm_mve_hw (and 
add_options_for_v8_1_m_mve_fp) is implemented.


R.



BR

   Andrea

Re: [PATCH 4/12] arm: Add testsuite library support for PACBTI target

[Andrea Corallo via Gcc-patches]

Richard Earnshaw  writes:

> On 01/07/2022 14:03, Richard Earnshaw via Gcc-patches wrote:
>> On 28/04/2022 10:40, Andrea Corallo via Gcc-patches wrote:
>>> Add targeting-checking entities for PACBTI in testsuite
>>> framework.
>>>
>>> Pre-approved with the requested changes here
>>> .
>>>
>>> gcc/testsuite/ChangeLog:
>>>
>>> * testsuite/lib/target-supports.exp:
>>> (check_effective_target_arm_pacbti_hw): New.
>>> * doc/sourcebuild.texi: Document arm_pacbti_hw.
>>>
>>> Co-Authored-By: Tejas Belagod  
>>>
>> +proc check_effective_target_arm_pacbti_hw {} {
>> +    return [check_runtime arm_pacbti_hw_available {
>> +    __attribute__ ((naked)) int
>> +    main (void)
>> +    {
>> +  asm ("pac r12, lr, sp");
>> So the armv8-m Arm ARM says that this instruction is in the NOP
>> space and that it is undefined if we aren't armv8-m.main or higher.
>> +  asm ("mov r0, #0");
>> +  asm ("autg r12, lr, sp");
>> This isn't in the nop space, but the Arm ARM says it is
>> unpredictable if the extension isn't present.  Unfortunately, that
>> means this isn't a particularly reliable way of detecting that the
>> PACBTI feature is present.
>> However, I can't think off hand of more reliable way of testing this
>> since reading the feature register ID_ISAR5 is not possible when in
>> unprivileged mode.
>> So I think we'll have to live with this.
>> +  asm ("bx lr");
>> +    }
>> +    } ""]
>> OK.
>> 
>
> Or perhaps not. The test does not try to add the right options to
> enable PAC/BTI if those aren't in the default selection for the
> current testsuite run.
>
> Perhaps we also need some additional tests to work out what
> architecture options to add (if any) to ensure the test will at least
> assemble.

Hi Richard,
thanks for reviewing.

Wouldn't be sufficient for that to have this test compiled with
-march=armv8-m.main?

BR

  Andrea

Re: [PATCH 4/12] arm: Add testsuite library support for PACBTI target

[Richard Earnshaw via Gcc-patches]

On 01/07/2022 14:03, Richard Earnshaw via Gcc-patches wrote:



On 28/04/2022 10:40, Andrea Corallo via Gcc-patches wrote:

Add targeting-checking entities for PACBTI in testsuite
framework.

Pre-approved with the requested changes here
.

gcc/testsuite/ChangeLog:

* testsuite/lib/target-supports.exp:
(check_effective_target_arm_pacbti_hw): New.
* doc/sourcebuild.texi: Document arm_pacbti_hw.

Co-Authored-By: Tejas Belagod  


+proc check_effective_target_arm_pacbti_hw {} {
+    return [check_runtime arm_pacbti_hw_available {
+    __attribute__ ((naked)) int
+    main (void)
+    {
+  asm ("pac r12, lr, sp");

So the armv8-m Arm ARM says that this instruction is in the NOP space 
and that it is undefined if we aren't armv8-m.main or higher.


+  asm ("mov r0, #0");
+  asm ("autg r12, lr, sp");

This isn't in the nop space, but the Arm ARM says it is unpredictable if 
the extension isn't present.  Unfortunately, that means this isn't a 
particularly reliable way of detecting that the PACBTI feature is present.


However, I can't think off hand of more reliable way of testing this 
since reading the feature register ID_ISAR5 is not possible when in 
unprivileged mode.


So I think we'll have to live with this.

+  asm ("bx lr");
+    }
+    } ""]

OK.



Or perhaps not. The test does not try to add the right options to enable 
PAC/BTI if those aren't in the default selection for the current 
testsuite run.


Perhaps we also need some additional tests to work out what architecture 
options to add (if any) to ensure the test will at least assemble.



R.

R.

Re: [PATCH 4/12] arm: Add testsuite library support for PACBTI target

[Richard Earnshaw via Gcc-patches]

On 28/04/2022 10:40, Andrea Corallo via Gcc-patches wrote:

Add targeting-checking entities for PACBTI in testsuite
framework.

Pre-approved with the requested changes here
.

gcc/testsuite/ChangeLog:

* testsuite/lib/target-supports.exp:
(check_effective_target_arm_pacbti_hw): New.
* doc/sourcebuild.texi: Document arm_pacbti_hw.

Co-Authored-By: Tejas Belagod  


+proc check_effective_target_arm_pacbti_hw {} {
+return [check_runtime arm_pacbti_hw_available {
+   __attribute__ ((naked)) int
+   main (void)
+   {
+ asm ("pac r12, lr, sp");

So the armv8-m Arm ARM says that this instruction is in the NOP space 
and that it is undefined if we aren't armv8-m.main or higher.


+ asm ("mov r0, #0");
+ asm ("autg r12, lr, sp");

This isn't in the nop space, but the Arm ARM says it is unpredictable if 
the extension isn't present.  Unfortunately, that means this isn't a 
particularly reliable way of detecting that the PACBTI feature is present.


However, I can't think off hand of more reliable way of testing this 
since reading the feature register ID_ISAR5 is not possible when in 
unprivileged mode.


So I think we'll have to live with this.

+ asm ("bx lr");
+   }
+} ""]

OK.

R.

[PATCH 4/12] arm: Add testsuite library support for PACBTI target

[Andrea Corallo via Gcc-patches]

Add targeting-checking entities for PACBTI in testsuite
framework.

Pre-approved with the requested changes here
.

gcc/testsuite/ChangeLog:

* testsuite/lib/target-supports.exp:
(check_effective_target_arm_pacbti_hw): New.
* doc/sourcebuild.texi: Document arm_pacbti_hw.

Co-Authored-By: Tejas Belagod  

diff --git a/gcc/doc/sourcebuild.texi b/gcc/doc/sourcebuild.texi
index 613ac29967b..e8cbd8e4aef 100644
--- a/gcc/doc/sourcebuild.texi
+++ b/gcc/doc/sourcebuild.texi
@@ -2167,6 +2167,10 @@ ARM target supports options to generate instructions 
from ARMv8.1-M with
 the Custom Datapath Extension (CDE) and M-Profile Vector Extension (MVE).
 Some multilibs may be incompatible with these options.
 
+@item arm_pacbti_hw
+Test system supports executing Pointer Authentication and Branch Target
+Identification instructions.
+
 @item arm_prefer_ldrd_strd
 ARM target prefers @code{LDRD} and @code{STRD} instructions over
 @code{LDM} and @code{STM} instructions.
diff --git a/gcc/testsuite/lib/target-supports.exp 
b/gcc/testsuite/lib/target-supports.exp
index ff8edbd3e17..df8ab037fb3 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -5090,6 +5090,22 @@ proc check_effective_target_arm_cmse_clear_ok {} {
 } "-mcmse"];
 }
 
+# Return 1 if the target supports executing PACBTI instructions, 0
+# otherwise.
+
+proc check_effective_target_arm_pacbti_hw {} {
+return [check_runtime arm_pacbti_hw_available {
+   __attribute__ ((naked)) int
+   main (void)
+   {
+ asm ("pac r12, lr, sp");
+ asm ("mov r0, #0");
+ asm ("autg r12, lr, sp");
+ asm ("bx lr");
+   }
+} ""]
+}
+
 # Return 1 if this compilation turns on string_ops_prefer_neon on.
 
 proc check_effective_target_arm_tune_string_ops_prefer_neon { } {