linux-kernel - Re: [PATCH 6/6] psi: introduce psi monitor

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Date:   Mon, 17 Dec 2018 17:22:23 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     gregkh@...uxfoundation.org, tj@...nel.org, lizefan@...wei.com,
        hannes@...xchg.org, axboe@...nel.dk, dennis@...nel.org,
        dennisszhou@...il.com, mingo@...hat.com, akpm@...ux-foundation.org,
        corbet@....net, cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com
Subject: Re: [PATCH 6/6] psi: introduce psi monitor

On Fri, Dec 14, 2018 at 09:15:08AM -0800, Suren Baghdasaryan wrote:
> +ssize_t psi_trigger_parse(char *buf, size_t nbytes, enum psi_res res,
> +	enum psi_states *state, u32 *threshold_us, u32 *win_sz_us)
> +{
> +	bool some;
> +	bool threshold_pct;
> +	u32 threshold;
> +	u32 win_sz;
> +	char *p;
> +
> +	p = strsep(&buf, " ");
> +	if (p == NULL)
> +		return -EINVAL;
> +
> +	/* parse type */
> +	if (!strcmp(p, "some"))
> +		some = true;
> +	else if (!strcmp(p, "full"))
> +		some = false;
> +	else
> +		return -EINVAL;
> +
> +	switch (res) {
> +	case (PSI_IO):
> +		*state = some ? PSI_IO_SOME : PSI_IO_FULL;
> +		break;
> +	case (PSI_MEM):
> +		*state = some ? PSI_MEM_SOME : PSI_MEM_FULL;
> +		break;
> +	case (PSI_CPU):
> +		if (!some)
> +			return -EINVAL;
> +		*state = PSI_CPU_SOME;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	while (isspace(*buf))
> +		buf++;
> +
> +	p = strsep(&buf, "%");
> +	if (p == NULL)
> +		return -EINVAL;
> +
> +	if (buf == NULL) {
> +		/* % sign was not found, threshold is specified in us */
> +		buf = p;
> +		p = strsep(&buf, " ");
> +		if (p == NULL)
> +			return -EINVAL;
> +
> +		threshold_pct = false;
> +	} else
> +		threshold_pct = true;
> +
> +	/* parse threshold */
> +	if (kstrtouint(p, 0, &threshold))
> +		return -EINVAL;
> +
> +	while (isspace(*buf))
> +		buf++;
> +
> +	p = strsep(&buf, " ");
> +	if (p == NULL)
> +		return -EINVAL;
> +
> +	/* Parse window size */
> +	if (kstrtouint(p, 0, &win_sz))
> +		return -EINVAL;
> +
> +	/* Check window size */
> +	if (win_sz < PSI_TRIG_MIN_WIN_US || win_sz > PSI_TRIG_MAX_WIN_US)
> +		return -EINVAL;
> +
> +	if (threshold_pct)
> +		threshold = (threshold * win_sz) / 100;
> +
> +	/* Check threshold */
> +	if (threshold == 0 || threshold > win_sz)
> +		return -EINVAL;
> +
> +	*threshold_us = threshold;
> +	*win_sz_us = win_sz;
> +
> +	return 0;
> +}

How well has this thing been fuzzed? Custom string parser, yay!