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Clemens Hammacher 4531c865a9 [wasm] Reuse LEB encoding logic in module builder 
Instead of using the WASM_I32V_* macros (and other) from
wasm-macro-gen.h, use the appropriate methods to encode LEB integers.
This also saves some spaces for the wasm bytecode generated from asm.js.

Specifically, this CL
1) renames EmitVarInt to EmitI32V and EmitVarUint to EmitU32V (on
   WasmFunctionBuilder).
2) introduces more methods on the WasmFunctionBuilder to emit i64v,
   u64v, f32, and f64 values.
3) uses the ZoneBuffer instead of a plain ZoneVector<char> in the
   WasmFunctionBuilder to build the body of the function.
4) introduces more helper functions on the ZoneBuffer to encode i64v,
   u64v, f32 and f64 values.

R=ahaas@chromium.org

Change-Id: Ifa59a6a67380ecf9a3823c382daf00855f5bc61e
Reviewed-on: https://chromium-review.googlesource.com/486803
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44842}
2017-04-25 11:32:21 +00:00
..
json Add json fuzzer 2016-02-02 11:29:01 +00:00
parser Add a library suitable for libfuzzer with a small unit test runner shell 2016-01-26 10:39:03 +00:00
regexp [regexp] add fuzzer support for regexp parser and compiler. 2016-02-01 14:00:38 +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 Add a library suitable for libfuzzer with a small unit test runner shell 2016-01-26 10:39:03 +00:00
fuzzer-support.cc [cleanup] Make ArrayList functions const. 2017-04-04 12:06:56 +00:00
fuzzer-support.h [cleanup] Make ArrayList functions const. 2017-04-04 12:06:56 +00:00
fuzzer.cc [wasm] Fix -Wsign-compare warnings. 2016-11-10 12:51:05 +00:00
fuzzer.gyp [wasm] Syntax- and Type-aware Fuzzer 2017-02-17 17:06:29 +00:00
fuzzer.isolate [wasm] Syntax- and Type-aware Fuzzer 2017-02-17 17:06:29 +00:00
fuzzer.status Add a library suitable for libfuzzer with a small unit test runner shell 2016-01-26 10:39:03 +00:00
json.cc Add GC request to libFuzzers in attempt to avoid parasitic coverage. 2016-04-28 13:32:28 +00:00
parser.cc Make isolate explicit param of parsing:: functions 2017-03-28 08:20:56 +00:00
README.md [fuzzer] Format README.md 2017-02-13 08:42:26 +00:00
regexp.cc [regexp fuzzer] Let the fuzzer input select the regexp flag. 2016-11-22 12:59:38 +00:00
testcfg.py [wasm] Syntax- and Type-aware Fuzzer 2017-02-17 17:06:29 +00:00
wasm_asmjs.tar.gz.sha1 [wasm] Update wasm fuzzer corpus 2017-04-25 08:24:41 +00:00
wasm-asmjs.cc [wasm] Change the constant kV8MaxWasmTableSize to a command line flag. 2017-01-24 10:12:22 +00:00
wasm-call.cc [wasm][fuzzer] Small fixes in the correctness fuzzer result comparison. 2017-02-16 11:23:29 +00:00
wasm-code.cc [wasm][fuzzer] Small fixes in the correctness fuzzer result comparison. 2017-02-16 11:23:29 +00:00
wasm-compile.cc [wasm] Reuse LEB encoding logic in module builder 2017-04-25 11:32:21 +00:00
wasm-data-section.cc [iwyu, wasm] Remove unallowed includes to objects-inl.h from wasm. 2017-02-13 15:05:37 +00:00
wasm-function-sigs-section.cc [iwyu, wasm] Remove unallowed includes to objects-inl.h from wasm. 2017-02-13 15:05:37 +00:00
wasm-globals-section.cc [iwyu, wasm] Remove unallowed includes to objects-inl.h from wasm. 2017-02-13 15:05:37 +00:00
wasm-imports-section.cc [iwyu, wasm] Remove unallowed includes to objects-inl.h from wasm. 2017-02-13 15:05:37 +00:00
wasm-memory-section.cc [iwyu, wasm] Remove unallowed includes to objects-inl.h from wasm. 2017-02-13 15:05:37 +00:00
wasm-names-section.cc [iwyu, wasm] Remove unallowed includes to objects-inl.h from wasm. 2017-02-13 15:05:37 +00:00
wasm-section-fuzzers.cc [wasm] Implement extensible name section 2017-04-07 16:31:47 +00:00
wasm-section-fuzzers.h [wasm] Implement extensible name section 2017-04-07 16:31:47 +00:00
wasm-types-section.cc [iwyu, wasm] Remove unallowed includes to objects-inl.h from wasm. 2017-02-13 15:05:37 +00:00
wasm.cc [wasm] Change the constant kV8MaxWasmTableSize to a command line flag. 2017-01-24 10:12:22 +00:00
wasm.tar.gz.sha1 [wasm] Update wasm fuzzer corpus 2017-04-25 08:24:41 +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