Re: [PATCH 6/6] psi: introduce psi monitor

Suren Baghdasaryan
2018-12-18T01:21:21Z

On Mon, Dec 17, 2018 at 8:22 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> 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!

Honestly, not much. Normal cases and some obvious corner cases. Will
check if I can use some fuzzer to get more coverage or will write a
script.
I'm not thrilled about writing a custom parser, so if there is a
better way to handle this please advise.

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