linux-kernel - Re: [PATCH v4 2/2] selftests: Add a test mangling with uc

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Message-ID: <abd97c85-c9d9-43c9-b0c2-36f6f0e442e0@linuxfoundation.org>
Date: Mon, 22 Jul 2024 08:58:51 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: Dev Jain <dev.jain@....com>, Oleg Nesterov <oleg@...hat.com>
Cc: shuah@...nel.org, mingo@...nel.org, tglx@...utronix.de,
 mark.rutland@....com, ryan.roberts@....com, broonie@...nel.org,
 suzuki.poulose@....com, Anshuman.Khandual@....com,
 DeepakKumar.Mishra@....com, aneesh.kumar@...nel.org,
 linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
 Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v4 2/2] selftests: Add a test mangling with uc_sigmask

On 7/15/24 05:49, Dev Jain wrote:
> 
> On 6/30/24 20:48, Oleg Nesterov wrote:
>> I see nothing wrong, but perhaps this test can be simplified?
>> Feel free to ignore.
>>
>> Say,
>>
>> On 06/27, Dev Jain wrote:
>>> +void handler_usr(int signo, siginfo_t *info, void *uc)
>>> +{
>>> +    int ret;
>>> +
>>> +    /*
>>> +     * Break out of infinite recursion caused by raise(SIGUSR1) invoked
>>> +     * from inside the handler
>>> +     */
>>> +    ++cnt;
>>> +    if (cnt > 1)
>>> +        return;
>>> +
>>> +    ksft_print_msg("In handler_usr\n");

This message isn't very useful. Why do you need this message?

>>> +
>>> +    /* SEGV blocked during handler execution, delivered on return */
>>> +    if (raise(SIGSEGV))
>>> +        ksft_exit_fail_perror("raise");>>> +
>>> +    ksft_print_msg("SEGV bypassed successfully\n");
>> You could simply do sigprocmask(SIG_SETMASK, NULL, &oldset) and check if
>> SIGSEGV is blocked in oldset. SIG_SETMASK has no effect if newset == NULL.
>>
> 
> IMHO, isn't raising the signal, and the process not terminating, a stricter test? I have already included your described approach in
> the last testcase; so, the test includes both ways: raising the
> signal -> process not terminating, and checking blockage with sigprocmask().

thanks,
-- Shuah