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Manos Koukoutos 797e4afefe [wasm] Support reftypes tables in WasmModuleBuilder 
WasmModuleBuilder is a class that is used to build Wasm modules in the
asm.js parser, in the fuzzer, as well as some tests. When it comes to
Wasm tables, WasmModuleBuilder currently supports only basic tables
(before the reftypes proposal) using an ad-hoc indirect-function index
vector.
This CL adds proper support for element sections and tables that use
them in the full potential of the reftypes extension. The new
functionality will only be used in the fuzzer and potentially some tests
in the future. Along this, we drop some functionality from
WasmModuleBuilder that was only used in tests and is redundant with the
new architecture.
Additionally, we remove tables other than externref and funcref from the
fuzzer (which were not supported properly or used anyway). We will
reintroduce them at a later time.

Bug: v8:11954
Change-Id: I0a4f6e7b63b6e3d9f7da03b5202fbf14d8678332
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3122162
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76597}
2021-08-31 10:02:19 +00:00
..
inspector [inspector] Handle isolate termination gracefully 2021-01-19 14:22:41 +00:00
json
multi_return
parser
regexp
regexp_builtins
wasm [wasm] Install the exception constructor in InstallConditionalFeatures 2021-03-25 16:28:53 +00:00
wasm_async [wasm][fuzzer] Fix return value of interpreter 2020-08-13 10:08:53 +00:00
wasm_code
wasm_compile
BUILD.gn [no-wasm] Exclude more targets from build 2021-03-09 11:25:54 +00:00
DEPS
fuzzer-support.cc [sandbox] Disallow ArrayBuffers outside the VM Cage 2021-08-25 09:52:38 +00:00
fuzzer-support.h Reland "[include] Split out v8.h" 2021-08-24 13:08:55 +00:00
fuzzer.cc
fuzzer.status [test] Filter tests for third party heap 2021-04-27 10:17:33 +00:00
inspector-fuzzer.cc Fix name collision of v8::internal::IsolateData 2021-08-25 08:45:53 +00:00
json.cc Reland "[include] Split out v8.h" 2021-08-24 13:08:55 +00:00
multi-return.cc [isolate][cleanup] Remove pointer to WasmEngine 2021-06-21 09:09:25 +00:00
parser.cc Reland "[include] Split out v8.h" 2021-08-24 13:08:55 +00:00
README.md
regexp-builtins.cc Reland "[include] Split out v8.h" 2021-08-24 13:08:55 +00:00
regexp.cc Reland "[include] Split out v8.h" 2021-08-24 13:08:55 +00:00
testcfg.py [inspector][fuzzer] Add inspector fuzzer 2020-11-02 14:29:08 +00:00
wasm_corpus.tar.gz.sha1 [wasm] Update and run script to generate fuzzer corpus 2020-12-01 16:21:51 +00:00
wasm-async.cc Reland "[include] Split out v8.h" 2021-08-24 13:08:55 +00:00
wasm-code.cc [fuzzer] Add struct type and array type to fuzzed module 2021-07-19 10:59:15 +00:00
wasm-compile.cc [wasm] Support reftypes tables in WasmModuleBuilder 2021-08-31 10:02:19 +00:00
wasm-fuzzer-common.cc [test] Improve some error messages and comments 2021-08-27 13:51:21 +00:00
wasm-fuzzer-common.h [fuzzer] Add struct type and array type to fuzzed module 2021-07-19 10:59:15 +00:00
wasm.cc Reland "[include] Split out v8.h" 2021-08-24 13:08:55 +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