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    SubjectRe: [PATCH 6/6] psi: introduce psi monitor
    On Mon, Dec 17, 2018 at 05:21:05PM -0800, Suren Baghdasaryan wrote:
    > On Mon, Dec 17, 2018 at 8:22 AM Peter Zijlstra <peterz@infradead.org> wrote:

    > > 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.

    The grammar seems fairly simple, something like:

    some-full = "some" | "full" ;
    threshold-abs = integer ;
    threshold-pct = integer, { "%" } ;
    threshold = threshold-abs | threshold-pct ;
    window = integer ;
    trigger = some-full, space, threshold, space, window ;

    And that could even be expressed as two scanf formats:

    "%4s %u%% %u" , "%4s %u %u"

    which then gets your something like:

    char type[5];

    if (sscanf(input, "%4s %u%% %u", &type, &pct, &window) == 3) {
    // do pct thing
    } else if (sscanf(intput, "%4s %u %u", &type, &thres, &window) == 3) {
    // do abs thing
    } else return -EFAIL;

    if (!strcmp(type, "some")) {
    // some
    } else if (!strcmp(type, "full")) {
    // full
    } else return -EFAIL;

    // do more

    which seems like a lot less error prone. Alternatively you can use 4
    formats:

    "some %u%% %u" "some %u %u"
    "full %u%% %u" "full %u %u"

    and avoid the whole 'type' thing.


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