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Andreas Haas 7b53a0e010 [wasm] Avoid executing infinite loops in the wasm fuzzers 
The wasm-async fuzzer uses the bytes provided by the fuzzer engine
directly as wasm module bytes, compiles them with async compilation, and
then tries to execute the "main" function of the module. This "main"
can have an infinite loop which causes a timeout in the fuzzer. With
this CL the "main" function is first executed with the interpreter. If
the execution in the interpreter finishes within 16k steps, which means
that there is no infinite loop, also the compiled code is executed.

I added the raw fuzzer input as a test case because in this case I
really want to test the fuzzer and not V8.

R=clemensh@chromium.org

Bug: chromium:761784
Change-Id: Id1fe5da0da8670ec821ab9979fdb9454dbde1162
Reviewed-on: https://chromium-review.googlesource.com/651046
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47874}
2017-09-07 12:35:45 +00:00
..
json Add json fuzzer 2016-02-02 11:29:01 +00:00
parser
regexp [regexp] add fuzzer support for regexp parser and compiler. 2016-02-01 14:00:38 +00:00
wasm [wasm] Cleanup the wasm fuzzer corpus files. 2017-05-19 09:21:16 +00:00
wasm_async [wasm] Avoid executing infinite loops in the wasm fuzzers 2017-09-07 12:35:45 +00:00
wasm_call [wasm] Add a new fuzzer which can also test wasm function calls. 2016-10-24 11:15:00 +00:00
wasm_code [wasm] Create a new fuzzer for wasm code. 2016-08-29 13:56:00 +00:00
wasm_compile [wasm] Syntax- and Type-aware Fuzzer 2017-02-17 17:06:29 +00:00
wasm_data_section [wasm] Write fuzzers for single wasm sections. 2016-09-14 11:17:53 +00:00
wasm_function_sigs_section [wasm] Write fuzzers for single wasm sections. 2016-09-14 11:17:53 +00:00
wasm_globals_section [wasm] Write fuzzers for single wasm sections. 2016-09-14 11:17:53 +00:00
wasm_imports_section [wasm] Write fuzzers for single wasm sections. 2016-09-14 11:17:53 +00:00
wasm_memory_section [wasm] Write fuzzers for single wasm sections. 2016-09-14 11:17:53 +00:00
wasm_names_section [wasm] Write fuzzers for single wasm sections. 2016-09-14 11:17:53 +00:00
wasm_types_section [wasm] Write fuzzers for single wasm sections. 2016-09-14 11:17:53 +00:00
DEPS
fuzzer-support.cc [test/fuzzer] Fix cpplint complaints 2017-09-04 10:45:21 +00:00
fuzzer-support.h [test/fuzzer] Fix cpplint complaints 2017-09-04 10:45:21 +00:00
fuzzer.cc [test/fuzzer] Fix cpplint complaints 2017-09-04 10:45:21 +00:00
fuzzer.gyp [wasm] Avoid executing infinite loops in the wasm fuzzers 2017-09-07 12:35:45 +00:00
fuzzer.isolate [wasm] Remove the wasm-asmjs fuzzer 2017-06-21 10:59:35 +00:00
fuzzer.status
json.cc Add GC request to libFuzzers in attempt to avoid parasitic coverage. 2016-04-28 13:32:28 +00:00
parser.cc [test/fuzzer] Fix cpplint complaints 2017-09-04 10:45:21 +00:00
README.md [fuzzer] Format README.md 2017-02-13 08:42:26 +00:00
regexp.cc [regexp] Additional checks to flush out fuzzer crash 2017-08-29 15:10:30 +00:00
testcfg.py [wasm] Remove the wasm-asmjs fuzzer 2017-06-21 10:59:35 +00:00
wasm_corpus.tar.gz.sha1 [wasm] Move the wasm fuzzer corpus to a different directory 2017-04-28 23:29:41 +00:00
wasm-async.cc [wasm] Avoid executing infinite loops in the wasm fuzzers 2017-09-07 12:35:45 +00:00
wasm-call.cc [test/fuzzer] Fix cpplint complaints 2017-09-04 10:45:21 +00:00
wasm-code.cc [test/fuzzer] Fix cpplint complaints 2017-09-04 10:45:21 +00:00
wasm-compile.cc [test/fuzzer] Fix cpplint complaints 2017-09-04 10:45:21 +00:00
wasm-data-section.cc add gn jumbo build support 2017-08-09 09:05:29 +00:00
wasm-function-sigs-section.cc add gn jumbo build support 2017-08-09 09:05:29 +00:00
wasm-fuzzer-common.cc [wasm] Avoid executing infinite loops in the wasm fuzzers 2017-09-07 12:35:45 +00:00
wasm-fuzzer-common.h [wasm] Avoid executing infinite loops in the wasm fuzzers 2017-09-07 12:35:45 +00:00
wasm-globals-section.cc add gn jumbo build support 2017-08-09 09:05:29 +00:00
wasm-imports-section.cc add gn jumbo build support 2017-08-09 09:05:29 +00:00
wasm-memory-section.cc add gn jumbo build support 2017-08-09 09:05:29 +00:00
wasm-names-section.cc add gn jumbo build support 2017-08-09 09:05:29 +00:00
wasm-types-section.cc add gn jumbo build support 2017-08-09 09:05:29 +00:00
wasm.cc [wasm] Avoid executing infinite loops in the wasm fuzzers 2017-09-07 12:35:45 +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 build rules of an existing fuzzer in test/fuzzer/fuzzer.gyp, e.g. the build rules for the wasm.cc fuzzer are v8_simple_wasm_fuzzer and wasm_fuzzer_lib

    • This build rule is needed to compile with gyp

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

  7. 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

  8. 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/reproducing.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