[Webkit-unassigned] [Bug 203898] Add FuzzerAgent that reads predictions from a file
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bugzilla-daemon at webkit.org
Fri Nov 8 06:00:30 PST 2019
https://bugs.webkit.org/show_bug.cgi?id=203898
--- Comment #5 from Tuomas Karkkainen <tuomas.webkit at apple.com> ---
(In reply to Saam Barati from comment #3)
> Comment on attachment 382922 [details]
> proposed patch
>
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=382922&action=review
>
> > Source/JavaScriptCore/ChangeLog:7
> > +
>
> you should describe the details of what this patch is doing here.
I'll add a description for this.
> > Source/JavaScriptCore/runtime/FuzzerPredictions.cpp:50
> > + while ((line = fgets(buffer, sizeof(buffer), f))) {
> > + SpeculatedType prediction;
> > + char lookupKey[BUFSIZ];
> > + int numberOfItemsFound = sscanf(line, "%[^:]:%llx\n", lookupKey, &prediction);
> > + RELEASE_ASSERT(numberOfItemsFound == 2);
> > + const String& functionNameString = String(lookupKey, strlen(lookupKey));
> > + m_predictions.set(functionNameString, prediction);
> > + }
>
> can you comment on the format of this file?
>
> Also, how do you produce this file?
I'll add a comment describing the format.
The file is produced by the fuzzer, which is not part of the WebKit repo.
> > Source/JavaScriptCore/runtime/FileBasedFuzzerAgent.cpp:167
> > +String FileBasedFuzzerAgent::createLookupKey(const String& sourceFilename, OpcodeID opcodeId, int startLocation, int endLocation)
> > +{
> > + StringBuilder lookupKey;
> > + lookupKey.append(sourceFilename);
> > + lookupKey.append("|");
> > + lookupKey.append(toString(opcodeAliasForLookupKey(opcodeId)));
> > + lookupKey.append("|");
> > + lookupKey.append(startLocation);
> > + lookupKey.append("|");
> > + lookupKey.append(endLocation);
> > + return lookupKey.toString();
> > +}
>
> nit: This is slightly hokey. We tend to define a struct for hash map keys,
> and use a custom hash and equality function. Turning it into a String is
> convenient, but slightly weird. I guess since we don't care about perf,
> maybe this is ok.
I figured since this is only for fuzzing I wouldn't spend too much effort on parsing the config file. The string here matches the format of the file containing the predictions, which I will document.
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