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To:     Andrey Konovalov <andreyknvl@gmail.com>
Cc:     Dmitry Vyukov <dvyukov@google.com>,
        Andrey Konovalov <andreyknvl@google.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Randy Dunlap <rdunlap@infradead.org>,
        Andrew Klychkov <andrew.a.klychkov@gmail.com>,
        Miguel Ojeda <ojeda@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Jakub Kicinski <kuba@kernel.org>,
        Aleksandr Nogikh <nogikh@google.com>,
        Wei Yongjun <weiyongjun1@huawei.com>,
        Maciej Grochowski <maciej.grochowski@pm.me>,
        kasan-dev@googlegroups.com, linux-doc@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>
References: <20210326205135.6098-1-info@alexander-lochmann.de>
 <CA+fCnZcTi=QLGC_LCdhs+fMrxkqX66kXEuM5ewOmjVjifKzUrw@mail.gmail.com>
From:   Alexander Lochmann <info@alexander-lochmann.de>
Subject: Re: [PATCHv3] Introduced new tracing mode KCOV_MODE_UNIQUE.
Message-ID: <aaee2292-022b-d99e-9fa9-b48ad5c2fe92@alexander-lochmann.de>
Date:   Sat, 18 Sep 2021 22:22:17 +0200
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From: Alexander Lochmann <info@alexander-lochmann.de>
To: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>,
 Andrey Konovalov <andreyknvl@google.com>, Jonathan Corbet <corbet@lwn.net>,
 Randy Dunlap <rdunlap@infradead.org>,
 Andrew Klychkov <andrew.a.klychkov@gmail.com>,
 Miguel Ojeda <ojeda@kernel.org>,
 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
 Andrew Morton <akpm@linux-foundation.org>, Jakub Kicinski <kuba@kernel.org>,
 Aleksandr Nogikh <nogikh@google.com>, Wei Yongjun <weiyongjun1@huawei.com>,
 Maciej Grochowski <maciej.grochowski@pm.me>, kasan-dev@googlegroups.com,
 linux-doc@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>
Message-ID: <aaee2292-022b-d99e-9fa9-b48ad5c2fe92@alexander-lochmann.de>
Subject: Re: [PATCHv3] Introduced new tracing mode KCOV_MODE_UNIQUE.
References: <20210326205135.6098-1-info@alexander-lochmann.de>
 <CA+fCnZcTi=QLGC_LCdhs+fMrxkqX66kXEuM5ewOmjVjifKzUrw@mail.gmail.com>
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On 27.03.21 15:56, Andrey Konovalov wrote:
>=20
>> @@ -213,9 +223,10 @@ static void notrace write_comp_data(u64 type, u64=
 arg1, u64 arg2, u64 ip)
>>          struct task_struct *t;
>>          u64 *area;
>>          u64 count, start_index, end_pos, max_pos;
>> +       unsigned int mode;
>>
>>          t =3D current;
>> -       if (!check_kcov_mode(KCOV_MODE_TRACE_CMP, t))
>> +       if (!check_kcov_mode(KCOV_MODE_TRACE_CMP, t, &mode))
>>                  return;
>=20
> mode isn't used here, right? No need for it then.
>=20
No, it's not. However, check_kcov_mode() needs it. Dmitry suggested=20
passing a pointer to check_kcov_mode(), and let the optimizer do the rest=
=2E
>> @@ -562,12 +576,14 @@ static int kcov_ioctl_locked(struct kcov *kcov, =
unsigned int cmd,
>>   {
>>          struct task_struct *t;
>>          unsigned long size, unused;
>> -       int mode, i;
>> +       int mode, i, text_size, ret =3D 0;
>>          struct kcov_remote_arg *remote_arg;
>>          struct kcov_remote *remote;
>>          unsigned long flags;
>>
>>          switch (cmd) {
>> +       case KCOV_INIT_UNIQUE:
>> +               fallthrough;
>>          case KCOV_INIT_TRACE:
>>                  /*
>>                   * Enable kcov in trace mode and setup buffer size.
>> @@ -581,11 +597,42 @@ static int kcov_ioctl_locked(struct kcov *kcov, =
unsigned int cmd,
>>                   * that must not overflow.
>>                   */
>>                  size =3D arg;
>> -               if (size < 2 || size > INT_MAX / sizeof(unsigned long)=
)
>> -                       return -EINVAL;
>> -               kcov->size =3D size;
>> -               kcov->mode =3D KCOV_MODE_INIT;
>> -               return 0;
>> +               if (cmd =3D=3D KCOV_INIT_UNIQUE) {
>=20
> Let's put this code under KCOV_INIT_UNIQUE in the switch. This
> internal if only saves duplicating two lines of code, which isn't
> worth it.
So. Shall I skip the fallthrough and move 'my' code upwards?

--=20
Alexander Lochmann                PGP key: 0xBC3EF6FD
Heiliger Weg 72                   phone:  +49.231.28053964
D-44141 Dortmund                  mobile: +49.151.15738323


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