[PATCH v2] selftests/ftrace: adjust offset for kprobe syntax error test

[PATCH v2] selftests/ftrace: adjust offset for kprobe syntax error test

[Hari Bathini]

In 'NOFENTRY_ARGS' test case for syntax check, any offset X of
`vfs_read+X` except function entry offset (0) fits the criterion,
even if that offset is not at instruction boundary, as the parser
comes before probing. But with "ENDBR64" instruction on x86, offset
4 is treated as function entry. So, X can't be 4 as well. Thus, 8
was used as offset for the test case. On 64-bit powerpc though, any
offset <= 16 can be considered function entry depending on build
configuration (see arch_kprobe_on_func_entry() for implementation
details). So, use `vfs_read+20` to accommodate that scenario too.

Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
---

Changes in v2:
* Use 20 as offset for all arches.


 .../selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc      | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc
index a16c6a6f6055..8f1c58f0c239 100644
--- a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc
+++ b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc
@@ -111,7 +111,7 @@ check_error 'p vfs_read $arg* ^$arg*'		# DOUBLE_ARGS
 if !grep -q 'kernel return probes support:' README; then
 check_error 'r vfs_read ^$arg*'			# NOFENTRY_ARGS
 fi
-check_error 'p vfs_read+8 ^$arg*'		# NOFENTRY_ARGS
+check_error 'p vfs_read+20 ^$arg*'		# NOFENTRY_ARGS
 check_error 'p vfs_read ^hoge'			# NO_BTFARG
 check_error 'p kfree ^$arg10'			# NO_BTFARG (exceed the number of parameters)
 check_error 'r kfree ^$retval'			# NO_RETVAL
-- 
2.47.0

Re: [PATCH v2] selftests/ftrace: adjust offset for kprobe syntax error test

[Steven Rostedt]

On Sat, 30 Nov 2024 01:56:21 +0530
Hari Bathini <hbathini@linux.ibm.com> wrote:

> In 'NOFENTRY_ARGS' test case for syntax check, any offset X of
> `vfs_read+X` except function entry offset (0) fits the criterion,
> even if that offset is not at instruction boundary, as the parser
> comes before probing. But with "ENDBR64" instruction on x86, offset
> 4 is treated as function entry. So, X can't be 4 as well. Thus, 8
> was used as offset for the test case. On 64-bit powerpc though, any
> offset <= 16 can be considered function entry depending on build
> configuration (see arch_kprobe_on_func_entry() for implementation
> details). So, use `vfs_read+20` to accommodate that scenario too.
> 
> Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
> Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>

Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Shuah,

Can you take this through your tree?

Thanks,

-- Steve

> ---
> 
> Changes in v2:
> * Use 20 as offset for all arches.
> 
> 
>  .../selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc      | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc
> index a16c6a6f6055..8f1c58f0c239 100644
> --- a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc
> +++ b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc
> @@ -111,7 +111,7 @@ check_error 'p vfs_read $arg* ^$arg*'		# DOUBLE_ARGS
>  if !grep -q 'kernel return probes support:' README; then
>  check_error 'r vfs_read ^$arg*'			# NOFENTRY_ARGS
>  fi
> -check_error 'p vfs_read+8 ^$arg*'		# NOFENTRY_ARGS
> +check_error 'p vfs_read+20 ^$arg*'		# NOFENTRY_ARGS
>  check_error 'p vfs_read ^hoge'			# NO_BTFARG
>  check_error 'p kfree ^$arg10'			# NO_BTFARG (exceed the number of parameters)
>  check_error 'r kfree ^$retval'			# NO_RETVAL

Re: [PATCH v2] selftests/ftrace: adjust offset for kprobe syntax error test

[Shuah Khan]

On 12/2/24 12:41, Steven Rostedt wrote:
> On Sat, 30 Nov 2024 01:56:21 +0530
> Hari Bathini <hbathini@linux.ibm.com> wrote:
> 
>> In 'NOFENTRY_ARGS' test case for syntax check, any offset X of
>> `vfs_read+X` except function entry offset (0) fits the criterion,
>> even if that offset is not at instruction boundary, as the parser
>> comes before probing. But with "ENDBR64" instruction on x86, offset
>> 4 is treated as function entry. So, X can't be 4 as well. Thus, 8
>> was used as offset for the test case. On 64-bit powerpc though, any
>> offset <= 16 can be considered function entry depending on build
>> configuration (see arch_kprobe_on_func_entry() for implementation
>> details). So, use `vfs_read+20` to accommodate that scenario too.
>>
>> Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
>> Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
> 
> Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> 
> Shuah,
> 
> Can you take this through your tree?

Yes I can take it. I do have question about whether this is
a fix - sounds like it is from the change log.

Clearly stating that it is a fix will help so it can be picked
up for stables.

thanks,
-- Shuah

Re: [PATCH v2] selftests/ftrace: adjust offset for kprobe syntax error test

[Steven Rostedt]

On Tue, 3 Dec 2024 18:01:06 -0700
Shuah Khan <skhan@linuxfoundation.org> wrote:

> On 12/2/24 12:41, Steven Rostedt wrote:
> > On Sat, 30 Nov 2024 01:56:21 +0530
> > Hari Bathini <hbathini@linux.ibm.com> wrote:
> >   
> >> In 'NOFENTRY_ARGS' test case for syntax check, any offset X of
> >> `vfs_read+X` except function entry offset (0) fits the criterion,
> >> even if that offset is not at instruction boundary, as the parser
> >> comes before probing. But with "ENDBR64" instruction on x86, offset
> >> 4 is treated as function entry. So, X can't be 4 as well. Thus, 8
> >> was used as offset for the test case. On 64-bit powerpc though, any
> >> offset <= 16 can be considered function entry depending on build
> >> configuration (see arch_kprobe_on_func_entry() for implementation
> >> details). So, use `vfs_read+20` to accommodate that scenario too.
> >>
> >> Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
> >> Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>  
> > 
> > Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> > 
> > Shuah,
> > 
> > Can you take this through your tree?  
> 
> Yes I can take it. I do have question about whether this is
> a fix - sounds like it is from the change log.
> 
> Clearly stating that it is a fix will help so it can be picked
> up for stables.

I would say it's a fix, as the test currently fails in certain scenarios
for powerpc.

You can add:

Fixes: 4231f30fcc34a ("selftests/ftrace: Add BTF arguments test cases")

-- Steve

Re: [PATCH v2] selftests/ftrace: adjust offset for kprobe syntax error test

[Shuah Khan]

On 12/3/24 18:20, Steven Rostedt wrote:
> On Tue, 3 Dec 2024 18:01:06 -0700
> Shuah Khan <skhan@linuxfoundation.org> wrote:
> 
>> On 12/2/24 12:41, Steven Rostedt wrote:
>>> On Sat, 30 Nov 2024 01:56:21 +0530
>>> Hari Bathini <hbathini@linux.ibm.com> wrote:
>>>    
>>>> In 'NOFENTRY_ARGS' test case for syntax check, any offset X of
>>>> `vfs_read+X` except function entry offset (0) fits the criterion,
>>>> even if that offset is not at instruction boundary, as the parser
>>>> comes before probing. But with "ENDBR64" instruction on x86, offset
>>>> 4 is treated as function entry. So, X can't be 4 as well. Thus, 8
>>>> was used as offset for the test case. On 64-bit powerpc though, any
>>>> offset <= 16 can be considered function entry depending on build
>>>> configuration (see arch_kprobe_on_func_entry() for implementation
>>>> details). So, use `vfs_read+20` to accommodate that scenario too.
>>>>
>>>> Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
>>>> Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
>>>
>>> Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
>>>
>>> Shuah,
>>>
>>> Can you take this through your tree?
>>
>> Yes I can take it. I do have question about whether this is
>> a fix - sounds like it is from the change log.
>>
>> Clearly stating that it is a fix will help so it can be picked
>> up for stables.
> 
> I would say it's a fix, as the test currently fails in certain scenarios
> for powerpc.
> 
> You can add:
> 
> Fixes: 4231f30fcc34a ("selftests/ftrace: Add BTF arguments test cases")
> 

I applied this to linux-kselftest fixes - will send it up for rc2 or rc3

thanks,
-- Shuah

Re: [PATCH v2] selftests/ftrace: adjust offset for kprobe syntax error test

[Steven Rostedt]

On Thu, 5 Dec 2024 09:06:43 -0700
Shuah Khan <skhan@linuxfoundation.org> wrote:

> I applied this to linux-kselftest fixes - will send it up for rc2 or rc3

Thanks Shuah,

-- Steve