linux-kernel - Re: [PATCH v2] selftests: prctl: Add new prctl test for PR_SET

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Message-ID: <CAK6rUAMODPLQeUawXMW_RNiJFdukOqdhS5GA5XRAq4U9bnQdNg@mail.gmail.com>
Date:   Sat, 10 Jun 2023 18:01:51 +0500
From:   Osama Muhammad <osmtendev@...il.com>
To:     Shuah Khan <skhan@...uxfoundation.org>
Cc:     shuah@...nel.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v2] selftests: prctl: Add new prctl test for PR_SET_NAME

Hi all,

I looked into it and tried to use TASK_COMM_LEN in the test. Even
though I included "linux/sched.h '', I was not able to compile the
test because it couldn't find it in the header file.
I dived deep into the issue and turns out header file mapped in
/usr/include/linux/sched.h is actually mapped to
/include/uapi/linux/sched.h[1] in linux source,
where TASK_COMM_LEN is not even defined. Instead TASK_COMM_LEN is
defined in /include/linux/sched.h which is not mapped to any header
files in
userspace(/(/usr/include/linux).
I also tried to find the TASK_COM_LEN in /usr/include/linux/ but I
couldn't find it. Following are the search results.
grep -rnw '/usr/include/linux/' -e 'TASK_COMM_LEN"
RESULTS OF COMMAND :- /usr/include/linux/taskstats.h:38:#define
TS_COMM_LEN 32 /* should be >= TASK_COMM_LEN
Based on this information, I have two questions:
1. Would this require a fix to move 'TASK_COMM_LEN' macro from
/include/linux/sched.h to UAPI headers /include/uapi/linux/sched.h.
2. Is there any other way to access TASK_COMM_LEN in the selftest that
I'm not aware of?

[1]:-https://elixir.bootlin.com/linux/v5.15.116/source/include/uapi/linux/sched.h

Thanks,
Osama

On Sat, 10 Jun 2023 at 02:43, Shuah Khan <skhan@...uxfoundation.org> wrote:
>
> On 6/7/23 09:36, Osama Muhammad wrote:
> > This patch will add the new test, which covers the prctl call
> > PR_SET_NAME command. The test tries to give a name using the PR_SET_NAME
> > call and then confirm it that it changed correctly by using  PR_GET_NAME.
> > It also tries to rename it with empty name.In the test PR_GET_NAME is
> > tested by passing null pointer to it and check its behaviour.
> >
> > Signed-off-by: Osama Muhammad <osmtendev@...il.com>
> >
> > ---
> > changes since v1:
> >       -Used TASK_COMM_LEN instead of using numerical value 16.
>
> Please add linux/sched.h here as an include to pull this.
> It is good to add an explicit include as opposed taking
> a chance on it being included from another include.
>
> thanks,
> -- Shuah