On Mon, Dec 17, 2018 at 8:22 AM Peter Zijlstra [off-list ref] wrote:

On Fri, Dec 14, 2018 at 09:15:08AM -0800, Suren Baghdasaryan wrote:

quoted

+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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