Subject: Re: [PATCHv2] selftests: kselftest.h: mark functions with 'noreturn'
To:     Anders Roxell <anders.roxell@linaro.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Shuah Khan <shuah@kernel.org>
Cc:     fenghua.yu@intel.com, reinette.chatre@intel.com,
        john.stultz@linaro.org, tglx@linutronix.de,
        akpm@linux-foundation.org, nathan@kernel.org,
        linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
        linux-mm@kvack.org, llvm@lists.linux.dev,
        Shuah Khan <skhan@linuxfoundation.org>
References: <20211103094752.1263442-1-anders.roxell@linaro.org>
 <CAKwvOdkq9k7ceyvnDWNN6m-vYOx41a6BBZwHy_0eDRfx5B4KnQ@mail.gmail.com>
 <CADYN=9+_UU9qZX56uahGXxz00iayqJLRAaQrRXh1CMXTvwSbAg@mail.gmail.com>
From:   Shuah Khan <skhan@linuxfoundation.org>
Message-ID: <e00fb2ce-b931-c725-7506-027bab0a6c47@linuxfoundation.org>
Date:   Wed, 17 Nov 2021 06:40:50 -0700
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On 11/17/21 4:01 AM, Anders Roxell wrote:
> On Wed, 3 Nov 2021 at 19:38, Nick Desaulniers <ndesaulniers@google.com> wrote:
>>
>> On Wed, Nov 3, 2021 at 2:47 AM Anders Roxell <anders.roxell@linaro.org> wrote:
>>>
>>> When building kselftests/capabilities the following warning shows up:
>>>
>>> clang -O2 -g -std=gnu99 -Wall    test_execve.c -lcap-ng -lrt -ldl -o test_execve
>>> test_execve.c:121:13: warning: variable 'have_outer_privilege' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
>>>          } else if (unshare(CLONE_NEWUSER | CLONE_NEWNS) == 0) {
>>>                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>> test_execve.c:136:9: note: uninitialized use occurs here
>>>          return have_outer_privilege;
>>>                 ^~~~~~~~~~~~~~~~~~~~
>>> test_execve.c:121:9: note: remove the 'if' if its condition is always true
>>>          } else if (unshare(CLONE_NEWUSER | CLONE_NEWNS) == 0) {
>>>                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>> test_execve.c:94:27: note: initialize the variable 'have_outer_privilege' to silence this warning
>>>          bool have_outer_privilege;
>>>                                   ^
>>>                                    = false
>>>
>>> Rework so all the ksft_exit_*() functions have attribue
>>> '__attribute__((noreturn))' so the compiler knows that there wont be
>>> any return from the function. That said, without
>>> '__attribute__((noreturn))' the compiler warns about the above issue
>>> since it thinks that it will get back from the ksft_exit_skip()
>>> function, which it wont.
>>> Cleaning up the callers that rely on ksft_exit_*() return code, since
>>> the functions ksft_exit_*() have never returned anything.
>>>
>>> Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
>>> ---
>>>   tools/testing/selftests/clone3/clone3.c              |  4 +++-
>>>   .../testing/selftests/clone3/clone3_clear_sighand.c  |  2 +-
>>>   tools/testing/selftests/clone3/clone3_set_tid.c      |  4 +++-
>>>   tools/testing/selftests/ipc/msgque.c                 | 10 +++++-----
>>>   tools/testing/selftests/kcmp/kcmp_test.c             |  2 +-
>>>   tools/testing/selftests/kselftest.h                  | 12 ++++++------
>>>   .../membarrier/membarrier_test_multi_thread.c        |  2 +-
>>>   .../membarrier/membarrier_test_single_thread.c       |  2 +-
>>>   tools/testing/selftests/pidfd/pidfd_fdinfo_test.c    |  2 +-
>>>   tools/testing/selftests/pidfd/pidfd_open_test.c      |  4 +++-
>>>   tools/testing/selftests/pidfd/pidfd_poll_test.c      |  2 +-
>>>   tools/testing/selftests/pidfd/pidfd_test.c           |  2 +-
>>>   tools/testing/selftests/resctrl/resctrl_tests.c      |  6 +++---
>>>   tools/testing/selftests/sync/sync_test.c             |  2 +-
>>>   tools/testing/selftests/timers/adjtick.c             |  4 ++--
>>>   tools/testing/selftests/timers/alarmtimer-suspend.c  |  4 ++--
>>>   tools/testing/selftests/timers/change_skew.c         |  4 ++--
>>>   tools/testing/selftests/timers/clocksource-switch.c  |  4 ++--
>>>   tools/testing/selftests/timers/freq-step.c           |  4 ++--
>>>   tools/testing/selftests/timers/inconsistency-check.c |  4 ++--
>>>   tools/testing/selftests/timers/leap-a-day.c          | 10 +++++-----
>>>   tools/testing/selftests/timers/leapcrash.c           |  4 ++--
>>>   tools/testing/selftests/timers/mqueue-lat.c          |  4 ++--
>>>   tools/testing/selftests/timers/nanosleep.c           |  4 ++--
>>>   tools/testing/selftests/timers/nsleep-lat.c          |  4 ++--
>>>   tools/testing/selftests/timers/posix_timers.c        | 12 ++++++------
>>>   tools/testing/selftests/timers/raw_skew.c            |  6 +++---
>>>   tools/testing/selftests/timers/set-2038.c            |  4 ++--
>>>   tools/testing/selftests/timers/set-tai.c             |  4 ++--
>>>   tools/testing/selftests/timers/set-timer-lat.c       |  4 ++--
>>>   tools/testing/selftests/timers/set-tz.c              |  4 ++--
>>>   tools/testing/selftests/timers/skew_consistency.c    |  4 ++--
>>>   tools/testing/selftests/timers/threadtest.c          |  2 +-
>>>   tools/testing/selftests/timers/valid-adjtimex.c      |  6 +++---
>>>   tools/testing/selftests/vm/madv_populate.c           |  2 +-
>>>   35 files changed, 80 insertions(+), 74 deletions(-)
>>>
>>> diff --git a/tools/testing/selftests/clone3/clone3.c b/tools/testing/selftests/clone3/clone3.c
>>> index 42be3b925830..ede5da0c67b4 100644
>>> --- a/tools/testing/selftests/clone3/clone3.c
>>> +++ b/tools/testing/selftests/clone3/clone3.c
>>> @@ -191,5 +191,7 @@ int main(int argc, char *argv[])
>>>          test_clone3(CLONE_NEWPID, getpagesize() + 8, -E2BIG,
>>>                          CLONE3_ARGS_NO_TEST);
>>>
>>> -       return !ksft_get_fail_cnt() ? ksft_exit_pass() : ksft_exit_fail();
>>> +       if (ksft_get_fail_cnt())
>>> +               ksft_exit_fail();
>>> +       ksft_exit_pass();
>>>   }
>>> diff --git a/tools/testing/selftests/clone3/clone3_clear_sighand.c b/tools/testing/selftests/clone3/clone3_clear_sighand.c
>>> index 47a8c0fc3676..dcd9448eaeec 100644
>>> --- a/tools/testing/selftests/clone3/clone3_clear_sighand.c
>>> +++ b/tools/testing/selftests/clone3/clone3_clear_sighand.c
>>> @@ -124,5 +124,5 @@ int main(int argc, char **argv)
>>>
>>>          test_clone3_clear_sighand();
>>>
>>> -       return ksft_exit_pass();
>>> +       ksft_exit_pass();
>>>   }
>>> diff --git a/tools/testing/selftests/clone3/clone3_set_tid.c b/tools/testing/selftests/clone3/clone3_set_tid.c
>>> index 0229e9ebb995..a755fcd3af89 100644
>>> --- a/tools/testing/selftests/clone3/clone3_set_tid.c
>>> +++ b/tools/testing/selftests/clone3/clone3_set_tid.c
>>> @@ -393,5 +393,7 @@ int main(int argc, char *argv[])
>>>   out:
>>>          ret = 0;
>>>
>>> -       return !ret ? ksft_exit_pass() : ksft_exit_fail();
>>> +       if (ret)
>>> +               ksft_exit_fail();
>>> +       ksft_exit_pass();
>>
>> This case is weird (pre-existing-ly) and looks broken.  The assignment
>> to ret should probably occur _before_ the out: label.  Honestly, I'd
>> remove the use of goto from this function and just call either
>> ksft_exit_pass() or ksft_exit_fail().
> 
> I can do that in a followup patch.
> 

Let's fold this change in. Please send me v3 with.

thanks,
-- Shuah