[DTrace-devel] [PATCH] test: Clean up fbtprovider/tst.return0.d

[Eugene Loh]

On 4/22/22 2:53 AM, Kris Van Hees wrote:

> On Thu, Apr 21, 2022 at 09:23:56PM -0400, eugene.loh--- via DTrace-devel wrote:
>> From: Eugene Loh <eugene.loh at oracle.com>
>>
>> Remove the vestigial -Z since the remaining probe is actually needed
>> for the test not to time out.  Change references to "arg0" (which is
>> not defined for fbt:::return probes) to "arg1".
> Removing -Z is correct.
Okay.
> CHanging from arg0 to arg1 is not correct.  The test verifies that the return
> value (in arg1) is 0 by means of the predicate.  But it prints out arg0 (and
> also refers to that in the test assertion.
>
> Now, the arg0 value is actually wrong but that is a different issue.
I do not understand why we would examine arg0 or how we could know arg0 
is wrong:  it seems to me that arg0 is undefined.

I also do not see why the test doesn't just time out.  Or if we're 
checking arg1, whether we should only be examining the lower 32 bits.

Importantly, it seems to me that arg1 (the fbt:::return value) is 
wrong.  The FBT trampoline seems to get probe args from the registers in 
a way that makes sense for fbt:::entry but not for fbt:::return.  
Specifically, we need to get arg1 from a particular register and the 
other args don't need to be retrieved at all (or set to 0?).

Our tests for fbt:::return values seem to be
                 test/stress/misc/tst.roch.d
                 test/unittest/fbtprovider/tst.functionreturnvalue.d
                 test/unittest/fbtprovider/tst.ioctlargs.d
                 test/unittest/fbtprovider/tst.offset.d
                 test/unittest/fbtprovider/tst.offsetzero.d
None actually checks the fbt return value.

I'll try to clean this stuff up.

>
>> Signed-off-by: Eugene Loh <eugene.loh at oracle.com>
>> ---
>>   test/unittest/fbtprovider/tst.return0.d | 8 +++-----
>>   1 file changed, 3 insertions(+), 5 deletions(-)
>>
>> diff --git a/test/unittest/fbtprovider/tst.return0.d b/test/unittest/fbtprovider/tst.return0.d
>> index 3d58e84f..e37a1632 100644
>> --- a/test/unittest/fbtprovider/tst.return0.d
>> +++ b/test/unittest/fbtprovider/tst.return0.d
>> @@ -1,24 +1,22 @@
>>   /*
>>    * Oracle Linux DTrace.
>> - * Copyright (c) 2006, 2021, Oracle and/or its affiliates. All rights reserved.
>> + * Copyright (c) 2006, 2022, Oracle and/or its affiliates. All rights reserved.
>>    * Licensed under the Universal Permissive License v 1.0 as shown at
>>    * http://oss.oracle.com/licenses/upl.
>>    */
>>   
>>   /*
>> - * ASSERTION: simple fbt provider arg0 and probfunc print test.
>> + * ASSERTION: simple fbt provider arg1 and probfunc print test.
>>    *
>>    * SECTION: FBT Provider/Probe arguments
>>    */
>>   
>> -/* @@runtest-opts: -Z */
>> -
>>   #pragma D option quiet
>>   #pragma D option statusrate=10ms
>>   
>>   fbt::do_sys_poll:return
>>   /arg1 == 0/
>>   {
>> -	printf("%s %x returned 0", probefunc, arg0);
>> +	printf("%s %x returned 0", probefunc, arg1);
>>   	exit(0);
>>   }
>> -- 
>> 2.18.4
>>
>>
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