linux-kernel - Re: [PATCH v5 06/17] sched/debug: Output SD flag names rather than their values

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Message-ID: <jhjpn7v66lf.mognet@arm.com>
Date:   Wed, 12 Aug 2020 19:51:08 +0100
From:   Valentin Schneider <valentin.schneider@....com>
To:     kernel test robot <lkp@...el.com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kbuild-all@...ts.01.org, mingo@...nel.org, peterz@...radead.org,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        morten.rasmussen@....com, Quentin Perret <qperret@...gle.com>
Subject: Re: [PATCH v5 06/17] sched/debug: Output SD flag names rather than their values


On 12/08/20 17:35, kernel test robot wrote:
> Hi Valentin,
>
> Thank you for the patch! Perhaps something to improve:
>

[...]


> url:    https://github.com/0day-ci/linux/commits/Valentin-Schneider/sched-Instrument-sched-domain-flags/20200812-205638
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git 949bcb8135a96a6923e676646bd29cbe69e8350f
> config: i386-randconfig-s001-20200811 (attached as .config)
> compiler: gcc-9 (Debian 9.3.0-15) 9.3.0
> reproduce:
>         # apt-get install sparse
>         # sparse version: v0.6.2-168-g9554805c-dirty
>         # save the attached .config to linux build tree
>         make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=i386
>

>>> kernel/sched/debug.c:279:17: sparse: sparse: non size-preserving pointer to integer cast
>>> kernel/sched/debug.c:279:17: sparse: sparse: non size-preserving integer to pointer cast
>
>    271
>    272		tmp = kcalloc(data_size + 1, sizeof(tmp), GFP_KERNEL);
>    273		for_each_set_bit(idx, &flags, __SD_FLAG_CNT) {
>    274			char *name = sd_flag_debug[idx].name;
>    275
>    276			len += snprintf(tmp + len, strlen(name) + 2, "%s ", name);
>    277		}
>    278
>  > 279		tmp += *ppos;

I pretty much copied kernel/sysctl.c::_proc_do_string() and I think that's
exactly the same types here: char* buffer incremented by loff_t offset. It
does look fine to me, but I can't really parse that warning.

>    280		len -= *ppos;
>    281
>    282		if (len > *lenp)
>    283			len = *lenp;
>    284		if (len)
>    285			memcpy(buffer, tmp, len);
>    286		if (len < *lenp) {
>    287			((char *)buffer)[len] = '\n';
>    288			len++;
>    289		}
>    290
>    291		*lenp = len;
>    292		*ppos += len;
>    293
>    294		kfree(tmp);
>    295
>    296		return 0;
>    297	}
>    298
>
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org