Initial import of v8-native WASM.

src/wasm/module-decoder.cc

+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "src/macro-assembler.h"
+#include "src/objects.h"
+#include "src/v8.h"
+
+#include "src/wasm/decoder.h"
+#include "src/wasm/module-decoder.h"
+
+namespace v8 {
+namespace internal {
+namespace wasm {
+
+#if DEBUG
+#define TRACE(...)                                    \
+  do {                                                \
+    if (FLAG_trace_wasm_decoder) PrintF(__VA_ARGS__); \
+  } while (false)
+#else
+#define TRACE(...)
+#endif
+
+
+// The main logic for decoding the bytes of a module.
+class ModuleDecoder : public Decoder {
+ public:
+  ModuleDecoder(Zone* zone, const byte* module_start, const byte* module_end,
+                bool asm_js)
+      : Decoder(module_start, module_end), module_zone(zone), asm_js_(asm_js) {
+    result_.start = start_;
+    if (limit_ < start_) {
+      error(start_, "end is less than start");
+      limit_ = start_;
+    }
+  }
+
+  virtual void onFirstError() {
+    pc_ = limit_;  // On error, terminate section decoding loop.
+  }
+
+  // Decodes an entire module.
+  ModuleResult DecodeModule(WasmModule* module, bool verify_functions = true) {
+    pc_ = start_;
+    module->module_start = start_;
+    module->module_end = limit_;
+    module->min_mem_size_log2 = 0;
+    module->max_mem_size_log2 = 0;
+    module->mem_export = false;
+    module->mem_external = false;
+    module->globals = new std::vector<WasmGlobal>();
+    module->signatures = new std::vector<FunctionSig*>();
+    module->functions = new std::vector<WasmFunction>();
+    module->data_segments = new std::vector<WasmDataSegment>();
+    module->function_table = new std::vector<uint16_t>();
+
+    bool sections[kMaxModuleSectionCode];
+    memset(sections, 0, sizeof(sections));
+
+    // Decode the module sections.
+    while (pc_ < limit_) {
+      TRACE("DecodeSection\n");
+      WasmSectionDeclCode section =
+          static_cast<WasmSectionDeclCode>(u8("section"));
+      // Each section should appear at most once.
+      if (section < kMaxModuleSectionCode) {
+        CheckForPreviousSection(sections, section, false);
+        sections[section] = true;
+      }
+
+      switch (section) {
+        case kDeclEnd:
+          // Terminate section decoding.
+          limit_ = pc_;
+          break;
+        case kDeclMemory:
+          module->min_mem_size_log2 = u8("min memory");
+          module->max_mem_size_log2 = u8("max memory");
+          module->mem_export = u8("export memory") != 0;
+          break;
+        case kDeclSignatures: {
+          int length;
+          uint32_t signatures_count = u32v(&length, "signatures count");
+          module->signatures->reserve(SafeReserve(signatures_count));
+          // Decode signatures.
+          for (uint32_t i = 0; i < signatures_count; i++) {
+            if (failed()) break;
+            TRACE("DecodeSignature[%d] module+%d\n", i,
+                  static_cast<int>(pc_ - start_));
+            FunctionSig* s = sig();  // read function sig.
+            module->signatures->push_back(s);
+          }
+          break;
+        }
+        case kDeclFunctions: {
+          // Functions require a signature table first.
+          CheckForPreviousSection(sections, kDeclSignatures, true);
+          int length;
+          uint32_t functions_count = u32v(&length, "functions count");
+          module->functions->reserve(SafeReserve(functions_count));
+          // Set up module environment for verification.
+          ModuleEnv menv;
+          menv.module = module;
+          menv.globals_area = 0;
+          menv.mem_start = 0;
+          menv.mem_end = 0;
+          menv.function_code = nullptr;
+          menv.asm_js = asm_js_;
+          // Decode functions.
+          for (uint32_t i = 0; i < functions_count; i++) {
+            if (failed()) break;
+            TRACE("DecodeFunction[%d] module+%d\n", i,
+                  static_cast<int>(pc_ - start_));
+
+            module->functions->push_back(
+                {nullptr, 0, 0, 0, 0, 0, 0, false, false});
+            WasmFunction* function = &module->functions->back();
+            DecodeFunctionInModule(module, function, false);
+          }
+          if (ok() && verify_functions) {
+            for (uint32_t i = 0; i < functions_count; i++) {
+              if (failed()) break;
+              WasmFunction* function = &module->functions->at(i);
+              if (!function->external) {
+                VerifyFunctionBody(i, &menv, function);
+                if (result_.failed())
+                  error(result_.error_pc, result_.error_msg.get());
+              }
+            }
+          }
+          break;
+        }
+        case kDeclGlobals: {
+          int length;
+          uint32_t globals_count = u32v(&length, "globals count");
+          module->globals->reserve(SafeReserve(globals_count));
+          // Decode globals.
+          for (uint32_t i = 0; i < globals_count; i++) {
+            if (failed()) break;
+            TRACE("DecodeGlobal[%d] module+%d\n", i,
+                  static_cast<int>(pc_ - start_));
+            module->globals->push_back({0, MachineType::Int32(), 0, false});
+            WasmGlobal* global = &module->globals->back();
+            DecodeGlobalInModule(global);
+          }
+          break;
+        }
+        case kDeclDataSegments: {
+          int length;
+          uint32_t data_segments_count = u32v(&length, "data segments count");
+          module->data_segments->reserve(SafeReserve(data_segments_count));
+          // Decode data segments.
+          for (uint32_t i = 0; i < data_segments_count; i++) {
+            if (failed()) break;
+            TRACE("DecodeDataSegment[%d] module+%d\n", i,
+                  static_cast<int>(pc_ - start_));
+            module->data_segments->push_back({0, 0, 0});
+            WasmDataSegment* segment = &module->data_segments->back();
+            DecodeDataSegmentInModule(segment);
+          }
+          break;
+        }
+        case kDeclFunctionTable: {
+          // An indirect function table requires functions first.
+          CheckForPreviousSection(sections, kDeclFunctions, true);
+          int length;
+          uint32_t function_table_count = u32v(&length, "function table count");
+          module->function_table->reserve(SafeReserve(function_table_count));
+          // Decode function table.
+          for (uint32_t i = 0; i < function_table_count; i++) {
+            if (failed()) break;
+            TRACE("DecodeFunctionTable[%d] module+%d\n", i,
+                  static_cast<int>(pc_ - start_));
+            uint16_t index = u16();
+            if (index >= module->functions->size()) {
+              error(pc_ - 2, "invalid function index");
+              break;
+            }
+            module->function_table->push_back(index);
+          }
+          break;
+        }
+        default:
+          error(pc_ - 1, nullptr, "unrecognized section 0x%02x", section);
+          break;
+      }
+    }
+
+    return toResult(module);
+  }
+
+  uint32_t SafeReserve(uint32_t count) {
+    // Avoid OOM by only reserving up to a certain size.
+    const uint32_t kMaxReserve = 20000;
+    return count < kMaxReserve ? count : kMaxReserve;
+  }
+
+  void CheckForPreviousSection(bool* sections, WasmSectionDeclCode section,
+                               bool present) {
+    if (section >= kMaxModuleSectionCode) return;
+    if (sections[section] == present) return;
+    const char* name = "";
+    switch (section) {
+      case kDeclMemory:
+        name = "memory";
+        break;
+      case kDeclSignatures:
+        name = "signatures";
+        break;
+      case kDeclFunctions:
+        name = "function declaration";
+        break;
+      case kDeclGlobals:
+        name = "global variable";
+        break;
+      case kDeclDataSegments:
+        name = "data segment";
+        break;
+      case kDeclFunctionTable:
+        name = "function table";
+        break;
+      default:
+        name = "";
+        break;
+    }
+    if (present) {
+      error(pc_ - 1, nullptr, "required %s section missing", name);
+    } else {
+      error(pc_ - 1, nullptr, "%s section already present", name);
+    }
+  }
+
+  // Decodes a single anonymous function starting at {start_}.
+  FunctionResult DecodeSingleFunction(ModuleEnv* module_env,
+                                      WasmFunction* function) {
+    pc_ = start_;
+    function->sig = sig();                       // read signature
+    function->name_offset = 0;                   // ---- name
+    function->code_start_offset = off(pc_ + 8);  // ---- code start
+    function->code_end_offset = off(limit_);     // ---- code end
+    function->local_int32_count = u16();         // read u16
+    function->local_int64_count = u16();         // read u16
+    function->local_float32_count = u16();       // read u16
+    function->local_float64_count = u16();       // read u16
+    function->exported = false;                  // ---- exported
+    function->external = false;                  // ---- external
+
+    if (ok()) VerifyFunctionBody(0, module_env, function);
+
+    FunctionResult result;
+    result.CopyFrom(result_);  // Copy error code and location.
+    result.val = function;
+    return result;
+  }
+
+  // Decodes a single function signature at {start}.
+  FunctionSig* DecodeFunctionSignature(const byte* start) {
+    pc_ = start;
+    FunctionSig* result = sig();
+    return ok() ? result : nullptr;
+  }
+
+ private:
+  Zone* module_zone;
+  ModuleResult result_;
+  bool asm_js_;
+
+  uint32_t off(const byte* ptr) { return static_cast<uint32_t>(ptr - start_); }
+
+  // Decodes a single global entry inside a module starting at {pc_}.
+  void DecodeGlobalInModule(WasmGlobal* global) {
+    global->name_offset = string("global name");
+    global->type = mem_type();
+    global->offset = 0;
+    global->exported = u8("exported") != 0;
+  }
+
+  // Decodes a single function entry inside a module starting at {pc_}.
+  void DecodeFunctionInModule(WasmModule* module, WasmFunction* function,
+                              bool verify_body = true) {
+    byte decl_bits = u8("function decl");
+
+    const byte* sigpos = pc_;
+    function->sig_index = u16("signature index");
+
+    if (function->sig_index >= module->signatures->size()) {
+      return error(sigpos, "invalid signature index");
+    } else {
+      function->sig = module->signatures->at(function->sig_index);
+    }
+
+    TRACE("  +%d  <function attributes:%s%s%s%s%s>\n",
+          static_cast<int>(pc_ - start_),
+          decl_bits & kDeclFunctionName ? " name" : "",
+          decl_bits & kDeclFunctionImport ? " imported" : "",
+          decl_bits & kDeclFunctionLocals ? " locals" : "",
+          decl_bits & kDeclFunctionExport ? " exported" : "",
+          (decl_bits & kDeclFunctionImport) == 0 ? " body" : "");
+
+    if (decl_bits & kDeclFunctionName) {
+      function->name_offset = string("function name");
+    }
+
+    function->exported = decl_bits & kDeclFunctionExport;
+
+    // Imported functions have no locals or body.
+    if (decl_bits & kDeclFunctionImport) {
+      function->external = true;
+      return;
+    }
+
+    if (decl_bits & kDeclFunctionLocals) {
+      function->local_int32_count = u16("int32 count");
+      function->local_int64_count = u16("int64 count");
+      function->local_float32_count = u16("float32 count");
+      function->local_float64_count = u16("float64 count");
+    }
+
+    uint16_t size = u16("body size");
+    if (ok()) {
+      if ((pc_ + size) > limit_) {
+        return error(pc_, limit_,
+                     "expected %d bytes for function body, fell off end", size);
+      }
+      function->code_start_offset = static_cast<uint32_t>(pc_ - start_);
+      function->code_end_offset = function->code_start_offset + size;
+      TRACE("  +%d  %-20s: (%d bytes)\n", static_cast<int>(pc_ - start_),
+            "function body", size);
+      pc_ += size;
+    }
+  }
+
+  // Decodes a single data segment entry inside a module starting at {pc_}.
+  void DecodeDataSegmentInModule(WasmDataSegment* segment) {
+    segment->dest_addr =
+        u32("destination");  // TODO(titzer): check it's within the memory size.
+    segment->source_offset = offset("source offset");
+    segment->source_size =
+        u32("source size");  // TODO(titzer): check the size is reasonable.
+    segment->init = u8("init");
+  }
+
+  // Verifies the body (code) of a given function.
+  void VerifyFunctionBody(uint32_t func_num, ModuleEnv* menv,
+                          WasmFunction* function) {
+    if (FLAG_trace_wasm_decode_time) {
+      // TODO(titzer): clean me up a bit.
+      OFStream os(stdout);
+      os << "Verifying WASM function:";
+      if (function->name_offset > 0) {
+        os << menv->module->GetName(function->name_offset);
+      }
+      os << std::endl;
+    }
+    FunctionEnv fenv;
+    fenv.module = menv;
+    fenv.sig = function->sig;
+    fenv.local_int32_count = function->local_int32_count;
+    fenv.local_int64_count = function->local_int64_count;
+    fenv.local_float32_count = function->local_float32_count;
+    fenv.local_float64_count = function->local_float64_count;
+    fenv.SumLocals();
+
+    TreeResult result =
+        VerifyWasmCode(&fenv, start_, start_ + function->code_start_offset,
+                       start_ + function->code_end_offset);
+    if (result.failed()) {
+      // Wrap the error message from the function decoder.
+      std::ostringstream str;
+      str << "in function #" << func_num << ": ";
+      // TODO(titzer): add function name for the user?
+      str << result;
+      const char* raw = str.str().c_str();
+      size_t len = strlen(raw);
+      char* buffer = new char[len];
+      strncpy(buffer, raw, len);
+      buffer[len - 1] = 0;
+
+      // Copy error code and location.
+      result_.CopyFrom(result);
+      result_.error_msg.Reset(buffer);
+    }
+  }
+
+  // Reads a single 32-bit unsigned integer interpreted as an offset, checking
+  // the offset is within bounds and advances.
+  uint32_t offset(const char* name = nullptr) {
+    uint32_t offset = u32(name ? name : "offset");
+    if (offset > (limit_ - start_)) {
+      error(pc_ - sizeof(uint32_t), "offset out of bounds of module");
+    }
+    return offset;
+  }
+
+  // Reads a single 32-bit unsigned integer interpreted as an offset into the
+  // data and validating the string there and advances.
+  uint32_t string(const char* name = nullptr) {
+    return offset(name ? name : "string");  // TODO(titzer): validate string
+  }
+
+  // Reads a single 8-bit integer, interpreting it as a local type.
+  LocalType local_type() {
+    byte val = u8("local type");
+    LocalTypeCode t = static_cast<LocalTypeCode>(val);
+    switch (t) {
+      case kLocalVoid:
+        return kAstStmt;
+      case kLocalI32:
+        return kAstI32;
+      case kLocalI64:
+        return kAstI64;
+      case kLocalF32:
+        return kAstF32;
+      case kLocalF64:
+        return kAstF64;
+      default:
+        error(pc_ - 1, "invalid local type");
+        return kAstStmt;
+    }
+  }
+
+  // Reads a single 8-bit integer, interpreting it as a memory type.
+  MachineType mem_type() {
+    byte val = u8("memory type");
+    MemTypeCode t = static_cast<MemTypeCode>(val);
+    switch (t) {
+      case kMemI8:
+        return MachineType::Int8();
+      case kMemU8:
+        return MachineType::Uint8();
+      case kMemI16:
+        return MachineType::Int16();
+      case kMemU16:
+        return MachineType::Uint16();
+      case kMemI32:
+        return MachineType::Int32();
+      case kMemU32:
+        return MachineType::Uint32();
+      case kMemI64:
+        return MachineType::Int64();
+      case kMemU64:
+        return MachineType::Uint64();
+      case kMemF32:
+        return MachineType::Float32();
+      case kMemF64:
+        return MachineType::Float64();
+      default:
+        error(pc_ - 1, "invalid memory type");
+        return MachineType::None();
+    }
+  }
+
+  // Parses an inline function signature.
+  FunctionSig* sig() {
+    byte count = u8("param count");
+    LocalType ret = local_type();
+    FunctionSig::Builder builder(module_zone, ret == kAstStmt ? 0 : 1, count);
+    if (ret != kAstStmt) builder.AddReturn(ret);
+
+    for (int i = 0; i < count; i++) {
+      LocalType param = local_type();
+      if (param == kAstStmt) error(pc_ - 1, "invalid void parameter type");
+      builder.AddParam(param);
+    }
+    return builder.Build();
+  }
+};
+
+
+// Helpers for nice error messages.
+class ModuleError : public ModuleResult {
+ public:
+  explicit ModuleError(const char* msg) {
+    error_code = kError;
+    size_t len = strlen(msg) + 1;
+    char* result = new char[len];
+    strncpy(result, msg, len);
+    result[len - 1] = 0;
+    error_msg.Reset(result);
+  }
+};
+
+
+// Helpers for nice error messages.
+class FunctionError : public FunctionResult {
+ public:
+  explicit FunctionError(const char* msg) {
+    error_code = kError;
+    size_t len = strlen(msg) + 1;
+    char* result = new char[len];
+    strncpy(result, msg, len);
+    result[len - 1] = 0;
+    error_msg.Reset(result);
+  }
+};
+
+
+ModuleResult DecodeWasmModule(Isolate* isolate, Zone* zone,
+                              const byte* module_start, const byte* module_end,
+                              bool verify_functions, bool asm_js) {
+  size_t size = module_end - module_start;
+  if (module_start > module_end) return ModuleError("start > end");
+  if (size >= kMaxModuleSize) return ModuleError("size > maximum module size");
+  WasmModule* module = new WasmModule();
+  ModuleDecoder decoder(zone, module_start, module_end, asm_js);
+  return decoder.DecodeModule(module, verify_functions);
+}
+
+
+FunctionSig* DecodeWasmSignatureForTesting(Zone* zone, const byte* start,
+                                           const byte* end) {
+  ModuleDecoder decoder(zone, start, end, false);
+  return decoder.DecodeFunctionSignature(start);
+}
+
+
+FunctionResult DecodeWasmFunction(Isolate* isolate, Zone* zone,
+                                  ModuleEnv* module_env,
+                                  const byte* function_start,
+                                  const byte* function_end) {
+  size_t size = function_end - function_start;
+  if (function_start > function_end) return FunctionError("start > end");
+  if (size > kMaxFunctionSize)
+    return FunctionError("size > maximum function size");
+  WasmFunction* function = new WasmFunction();
+  ModuleDecoder decoder(zone, function_start, function_end, false);
+  return decoder.DecodeSingleFunction(module_env, function);
+}
+}  // namespace wasm
+}  // namespace internal
+}  // namespace v8