Extract common code from runtime implementations.

include/proxy-wasm/null_vm.h

@@ -44,7 +44,6 @@ struct NullVm : public WasmVm {
   bool setWord(uint64_t pointer, Word data) override;
   bool getWord(uint64_t pointer, Word *data) override;
   size_t getWordSize() override;
-  std::string_view getCustomSection(std::string_view name) override;
   std::string_view getPrecompiledSectionName() override;
 
 #define _FORWARD_GET_FUNCTION(_T)                                                                  \

include/proxy-wasm/wasm_vm.h

@@ -248,14 +248,6 @@ class WasmVm {
    */
   virtual size_t getWordSize() = 0;
 
-  /**
-   * Get the contents of the custom section with the given name or "" if it does not exist.
-   * @param name the name of the custom section to get.
-   * @return the contents of the custom section (if any). The result will be empty if there
-   * is no such section.
-   */
-  virtual std::string_view getCustomSection(std::string_view name) = 0;
-
   /**
    * Get the name of the custom section that contains precompiled module.
    * @return the name of the custom section that contains precompiled module.

src/common/wasm_util.cc

@@ -0,0 +1,159 @@
+// Copyright 2021 Google LLC
+//
+// 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.
+
+#include "src/common/wasm_util.h"
+#include <cstdio>
+#include <string.h>
+
+namespace proxy_wasm {
+namespace common {
+
+bool WasmUtil::getCustomSection(const char *begin, const char *end, std::string_view name,
+                                std::string_view &ret) {
+  // Skip the Wasm header.
+  const char *pos = begin + 8;
+  while (pos < end) {
+    if (pos + 1 > end) {
+      return false;
+    }
+    const auto section_type = *pos++;
+    uint32_t section_len = 0;
+    if (!parseVarint(pos, end, section_len) || pos + section_len > end) {
+      return false;
+    }
+    if (section_type == 0) {
+      // Custom section.
+      const auto section_data_start = pos;
+      uint32_t section_name_len = 0;
+      if (!WasmUtil::parseVarint(pos, end, section_name_len) || pos + section_name_len > end) {
+        return false;
+      }
+      if (section_name_len == name.size() && ::memcmp(pos, name.data(), section_name_len) == 0) {
+        pos += section_name_len;
+        ret = {pos, static_cast<size_t>(section_data_start + section_len - pos)};
+        return true;
+      }
+      pos = section_data_start + section_len;
+    } else {
+      // Skip other sections.
+      pos += section_len;
+    }
+  }
+  return true;
+};
+
+bool WasmUtil::getFunctionNameIndex(const char *begin, const char *end,
+                                    std::unordered_map<uint32_t, std::string> &ret) {
+  std::string_view name_section = {};
+  if (!WasmUtil::getCustomSection(begin, end, "name", name_section)) {
+    return false;
+  };
+  if (!name_section.empty()) {
+    const char *pos = name_section.data();
+    const char *end = name_section.data() + name_section.size();
+    while (pos < end) {
+      const auto subsection_id = *pos++;
+      uint32_t subsection_size = 0;
+      if (!parseVarint(pos, end, subsection_size) || pos + subsection_size > end) {
+        return false;
+      }
+
+      if (subsection_id != 1) {
+        // Skip other subsctions.
+        pos += subsection_size;
+      } else {
+        // Enters function name subsection.
+        const auto start = pos;
+        uint32_t namemap_vector_size = 0;
+        if (!parseVarint(pos, end, namemap_vector_size) || pos + namemap_vector_size > end) {
+          return false;
+        }
+        for (uint32_t i = 0; i < namemap_vector_size; i++) {
+          uint32_t func_index = 0;
+          if (!parseVarint(pos, end, func_index)) {
+            return false;
+          }
+
+          uint32_t func_name_size = 0;
+          if (!parseVarint(pos, end, func_name_size) || pos + func_name_size > end) {
+            return false;
+          }
+          ret.insert({func_index, std::string(pos, func_name_size)});
+          pos += func_name_size;
+        }
+        if (start + subsection_size != pos) {
+          return false;
+        }
+      }
+    }
+  }
+  return true;
+}
+
+bool WasmUtil::getStrippedSource(const char *begin, const char *end, std::vector<char> &ret) {
+  // Skip the Wasm header.
+  const char *pos = begin + 8;
+  while (pos < end) {
+    const auto section_start = pos;
+    if (pos + 1 > end) {
+      return false;
+    }
+    const auto section_type = *pos++;
+    uint32_t section_len = 0;
+    if (!parseVarint(pos, end, section_len) || pos + section_len > end) {
+      return false;
+    }
+    if (section_type == 0 /* custom section */) {
+      const auto section_data_start = pos;
+      uint32_t section_name_len = 0;
+      if (!parseVarint(pos, end, section_name_len) || pos + section_name_len > end) {
+        return false;
+      }
+      auto section_name = std::string_view(pos, section_name_len);
+      if (section_name.find("precompiled_") != std::string::npos) {
+        // If this is the first "precompiled_" section, then save everything
+        // before it, otherwise skip it.
+        if (ret.empty()) {
+          const char *start = begin;
+          ret.insert(ret.end(), start, section_start);
+        }
+      }
+      pos = section_data_start + section_len;
+    } else {
+      pos += section_len;
+      // Save this section if we already saw a custom "precompiled_" section.
+      if (!ret.empty()) {
+        ret.insert(ret.end(), section_start, pos /* section end */);
+      }
+    }
+  }
+  return true;
+}
+
+bool WasmUtil::parseVarint(const char *&pos, const char *end, uint32_t &ret) {
+  uint32_t shift = 0;
+  char b;
+  do {
+    if (pos + 1 > end) {
+      return false;
+    }
+    b = *pos++;
+    ret += (b & 0x7f) << shift;
+    shift += 7;
+  } while ((b & 0x80) != 0);
+  return ret != static_cast<uint32_t>(-1);
+}
+
+} // namespace common
+} // namespace proxy_wasm

src/common/wasm_util.h

@@ -0,0 +1,69 @@
+// Copyright 2021 Google LLC
+//
+// 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.
+#pragma once
+
+#include <string_view>
+#include <vector>
+#include <unordered_map>
+
+namespace proxy_wasm {
+namespace common {
+
+// Utilitiy functions which directly operate on Wasm bytecodes.
+class WasmUtil {
+public:
+  /**
+   * getCustomSection extract the view of the custom section for a given name.
+   * @param begin is the beggining of bytecode.
+   * @param end is the end of bytecode.
+   * @param name is the name of the custom section.
+   * @param ret is the reference to store the resulting view to the custom section.
+   * @return indicates whether parsing succeeded or not.
+   */
+  static bool getCustomSection(const char *begin, const char *end, std::string_view name,
+                               std::string_view &ret);
+
+  /**
+   * getFunctionNameIndex constructs the map from function indexes to function names stored in
+   * the function name subsection in "name" custom section.
+   * See https://webassembly.github.io/spec/core/appendix/custom.html#binary-funcnamesec for detail.
+   * @param begin is the beggining of bytecode.
+   * @param end is the end of bytecode.
+   * @param ret the reference to store map from function indexes to function names.
+   * @return indicates whether parsing succeeded or not.
+   */
+  static bool getFunctionNameIndex(const char *begin, const char *end,
+                                   std::unordered_map<uint32_t, std::string> &ret);
+
+  /**
+   * getStrippedSource gets Wasm module without Custom Sections to save some memory in workers.
+   * @param begin is the beggining of original bytecode.
+   * @param end is the end of original bytecode.
+   * @param ret the reference to the stripped bytecode.
+   * @return indicates whether parsing succeeded or not.
+   */
+  static bool getStrippedSource(const char *begin, const char *end, std::vector<char> &ret);
+
+  /**
+   * parseVarint parses the bytecode following LEB128.
+   * @param begin is the postion where parsing starts.
+   * @param end is the end of bytecode.
+   * @param ret is the reference to store the resulting value.
+   * @return indicates whether parsing succeeded or not.
+   */
+  static bool parseVarint(const char *&begin, const char *end, uint32_t &ret);
+};
+
+} // namespace common
+} // namespace proxy_wasm

src/null/null_vm.cc

@@ -104,11 +104,6 @@ bool NullVm::getWord(uint64_t pointer, Word *data) {
 
 size_t NullVm::getWordSize() { return sizeof(uint64_t); }
 
-std::string_view NullVm::getCustomSection(std::string_view /* name */) {
-  // Return nothing: there is no WASM file.
-  return {};
-}
-
 std::string_view NullVm::getPrecompiledSectionName() {
   // Return nothing: there is no WASM file.
   return {};