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Clemens Hammacher 2270c0eaaa [wasm][fuzzer] Run micro tasks after each fuzzer execution 
This asserts that we run e.g. GC finalization tasks. Without that, we
might run ouf of memory.

R=ahaas@chromium.org

Bug: chromium:938739
Change-Id: Ic80074f877183bcabb3353fbeff94842a534efab
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1526007
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60266}
2019-03-15 14:23:45 +00:00
..
json
multi_return [turbofan] Add fuzzer to test different signatures for multi-returns 2018-01-12 12:20:27 +00:00
parser
regexp
regexp_builtins [regexp] Initial go at a builtins fuzzer 2018-01-18 11:02:57 +00:00
wasm
wasm_async
wasm_code
wasm_compile
BUILD.gn [fuzzer] Remove the wasm section fuzzers 2019-01-11 15:18:47 +00:00
DEPS
fuzzer-support.cc [cleanup] Deprecate EnsureEventLoopInitialized 2018-02-28 15:32:28 +00:00
fuzzer-support.h [fuzzer] Use std::unique_ptr for the FuzzerSupport 2017-11-29 16:36:23 +00:00
fuzzer.cc
fuzzer.status [test] Don't test jitless without embedded-builtins 2019-02-26 14:33:01 +00:00
json.cc [fuzzer] Fix OOM in v8_json_parser_fuzzer due to unnecessary long input. 2018-07-17 14:25:27 +00:00
multi-return.cc [wasm] Keep NativeModule alive in BackgroundCompileScope 2019-03-13 08:04:04 +00:00
parser.cc Reduce input size limit of parser fuzzer to 2kB 2018-12-17 13:39:05 +00:00
README.md [gyp] move build targets for tests to gypfiles. 2018-01-30 06:31:00 +00:00
regexp-builtins.cc [regexp-builtins-fuzzer] Print generated source in verbose mode 2019-03-08 11:40:41 +00:00
regexp.cc [explicit isolates] Remove GetIsolate from objects.cc 2018-07-13 12:42:14 +00:00
testcfg.py Reland "Reland "[test] refactor testsuite configuration"" 2019-02-06 09:02:09 +00:00
wasm_corpus.tar.gz.sha1
wasm-async.cc Reland "[wasm] Implement the new API for WebAssembly.instantiateStreaming" 2018-08-14 08:20:19 +00:00
wasm-code.cc [wasm][fuzzer] Remove unused return value 2018-11-20 17:15:35 +00:00
wasm-compile.cc [wasm][fuzzer] Remove unused return value 2018-11-20 17:15:35 +00:00
wasm-fuzzer-common.cc [wasm] merge js constants file in module-builder 2019-01-30 22:10:34 +00:00
wasm-fuzzer-common.h [fuzzer] Remove the wasm section fuzzers 2019-01-11 15:18:47 +00:00
wasm.cc [wasm][fuzzer] Run micro tasks after each fuzzer execution 2019-03-15 14:23:45 +00:00

README.md

How to make a libFuzzer fuzzer in V8

This document describes how to make a new libFuzzer fuzzer for V8. A general introduction to libFuzzer can be found here. In short, libFuzzer is an in-process coverage-driven evolutionary fuzzer. libFuzzer serves you with a sequence of byte arrays that you can use to test your code. libFuzzer tries to generate this sequence of byte arrays in a way that maximizes test coverage.

Warning: By itself libFuzzer typically does not generate valid JavaScript code.

Changes to V8

tldr: Do the same as https://codereview.chromium.org/2280623002 to introduce a new fuzzer to V8.

This is a step by step guide on how to make a new fuzzer in V8. In the example the fuzzer is called foo.

  1. Copy one of the existing fuzzer implementations in test/fuzzer/, e.g. cp wasm.cc foo.cc

    • Copying an existing fuzzer is a good idea to get all the required setup, e.g. setting up the isolate

  2. Create a directory called foo in test/fuzzer/ which contains at least one file

    • The file is used by the trybots to check whether the fuzzer actually compiles and runs

  3. Copy the build rules of an existing fuzzer in BUILD.gn, e.g. the build rules for the wasm.cc fuzzer are v8_source_set("wasm_fuzzer") and v8_fuzzer("wasm_fuzzer"). Note that the name has to be the name of the directory created in Step 2 + _fuzzer so that the scripts on the trybots work

  4. Now you can already compile the fuzzer, e.g. with ninja -j 1000 -C out/x64.debug/v8_simple_foo_fuzzer

    • Use this binary to reproduce issues found by cluster fuzz, e.g. out/x64.debug/v8_simple_foo_fuzzer testcase.foo

  5. Copy the binary name and the test directory name in test/fuzzer/fuzzer.isolate

  6. Add the fuzzer to the FuzzerTestSuite in test/fuzzer/testcfg.py

    • This step is needed to run the fuzzer with the files created in Step 2 on the trybots

  7. Commit the changes described above to the V8 repository

Changes to Chromium

tldr: Do the same as https://codereview.chromium.org/2344823002 to add the new fuzzer to cluster fuzz.

  1. Copy the build rules of an existing fuzzer in testing/libfuzzer/fuzzers/BUILD.gn, e.g. the build rule for the wasm.cc fuzzer is v8_wasm_fuzzer. There is no need to set a dictionary , or a seed_corpus. See chromium-fuzzing-getting-started for more information.

  2. Compile the fuzzer in chromium (for different configurations see: https://chromium.googlesource.com/chromium/src/+/master/testing/libfuzzer/reference.md):

    • gn gen out/libfuzzer '--args=use_libfuzzer=true is_asan=true is_debug=false enable_nacl=false'

    • ninja -j 1000 -C out/libfuzzer/ v8_foo_fuzzer

  3. Run the fuzzer locally

    • mkdir /tmp/empty_corpus && out/libfuzzer/v8_foo_fuzzer /tmp/empty_corpus