New fuzzer (#1126)

This adds a new method of fuzzing, "translate to fuzz" which means we consider the input to be a stream of data that we translate into a valid wasm module. It's sort of like a random seed for a process that creates a random wasm module. By using the input that way, we can explore the space of valid wasm modules quickly, and it makes afl-fuzz integration easy.

Also adds a "fuzz binary" option which is similar to "fuzz execution". It makes wasm-opt not only execute the code before and after opts, but also write to binary and read from it, helping to fuzz the binary format.

1 files changed, 47 insertions, 0 deletions

diff --git a/src/tools/spec-wrapper.h b/src/tools/spec-wrapper.h
new file mode 100644
index 000000000..4da746a5d
--- /dev/null
+++ b/src/tools/spec-wrapper.h
@@ -0,0 +1,47 @@
+/*
+ * Copyright 2017 WebAssembly Community Group participants
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//
+// Emit a wasm spec interpreter wrapper to run a wasm module with some test
+// values, useful for fuzzing.
+//
+
+namespace wasm {
+
+static std::string generateSpecWrapper(Module& wasm) {
+  std::string ret;
+  for (auto& exp : wasm.exports) {
+    auto* func = wasm.getFunctionOrNull(exp->value);
+    if (!func) continue; // something exported other than a function
+    ret += std::string("(invoke \"hangLimitInitializer\") (invoke \"") + exp->name.str + "\" ";
+    for (WasmType param : func->params) {
+      // zeros in arguments TODO more?
+      switch (param) {
+        case i32: ret += "(i32.const 0)"; break;
+        case i64: ret += "(i64.const 0)"; break;
+        case f32: ret += "(f32.const 0)"; break;
+        case f64: ret += "(f64.const 0)"; break;
+        default: WASM_UNREACHABLE();
+      }
+      ret += " ";
+    }
+    ret += ") ";
+  }
+  return ret;
+}
+
+} // namespace wasm
+