wasm: use strings for section names

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"
@@ skipping 33 matching lines @@
   ModuleResult DecodeModule(WasmModule* module, bool verify_functions = true) {
     pc_ = start_;
     module->module_start = start_;
     module->module_end = limit_;
     module->min_mem_pages = 0;
     module->max_mem_pages = 0;
     module->mem_export = false;
     module->mem_external = false;
     module->origin = origin_;
 
-    bool sections[kMaxModuleSectionCode] = {false};
+    bool sections[(size_t)WasmSection::Code::Max] = {false};
 
     const byte* pos = pc_;
     uint32_t magic_word = consume_u32("wasm magic");
 #define BYTES(x) (x & 0xff), (x >> 8) & 0xff, (x >> 16) & 0xff, (x >> 24) & 0xff
     if (magic_word != kWasmMagic) {
       error(pos, pos,
             "expected magic word %02x %02x %02x %02x, "
             "found %02x %02x %02x %02x",
             BYTES(kWasmMagic), BYTES(magic_word));
       return toResult(module);
     }
 
     pos = pc_;
     uint32_t magic_version = consume_u32("wasm version");
     if (magic_version != kWasmVersion) {
       error(pos, pos,
             "expected version %02x %02x %02x %02x, "
             "found %02x %02x %02x %02x",
             BYTES(kWasmVersion), BYTES(magic_version));
       return toResult(module);
     }
 
     // Decode the module sections.
     while (pc_ < limit_) {
       TRACE("DecodeSection\n");
-      uint8_t section_u8 = consume_u8("section");
+      pos = pc_;
 
-      if (section_u8 >= kMaxModuleSectionCode) {
+      int length;
+      uint32_t section_length = consume_u32v(&length, "section size");
+
+      int section_string_leb_length = 0;
+      uint32_t section_string_length = 0;
+      WasmSection::Code section = consume_section_name(
+          &section_string_leb_length, &section_string_length);
+      uint32_t string_and_leb_length =
+          section_string_leb_length + section_string_length;
+      if (string_and_leb_length > section_length) {
+        error(pos, pos,
+              "section string of size %u longer than total section bytes %u",
+              string_and_leb_length, section_length);
+        break;
+      }
+
+      if (section == WasmSection::Code::Max) {
         // Skip unknown section.
-        int length;
-        uint32_t section_bytes = consume_u32v(&length, "section size");
-        consume_bytes(section_bytes);
+        uint32_t skip = section_length - string_and_leb_length;
+        TRACE("skipping %u bytes from unknown section\n", skip);
+        consume_bytes(skip);
         continue;
       }
 
       // Each section should appear at most once.
-      auto section = static_cast<WasmSectionDeclCode>(section_u8);
       CheckForPreviousSection(sections, section, false);
-      sections[section] = true;
+      sections[(size_t)section] = true;
 
       switch (section) {
-        case kDeclEnd:
+        case WasmSection::Code::End:
           // Terminate section decoding.
           limit_ = pc_;
           break;
-        case kDeclMemory:
+        case WasmSection::Code::Memory:
           int length;
           module->min_mem_pages = consume_u32v(&length, "min memory");
           module->max_mem_pages = consume_u32v(&length, "max memory");
           module->mem_export = consume_u8("export memory") != 0;
           break;
-        case kDeclSignatures: {
+        case WasmSection::Code::Signatures: {
           int length;
           uint32_t signatures_count = consume_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 = consume_sig();  // read function sig.
             module->signatures.push_back(s);
           }
           break;
         }
-        case kDeclFunctionSignatures: {
+        case WasmSection::Code::FunctionSignatures: {
           // Functions require a signature table first.
-          CheckForPreviousSection(sections, kDeclSignatures, true);
+          CheckForPreviousSection(sections, WasmSection::Code::Signatures,
+                                  true);
           int length;
           uint32_t functions_count = consume_u32v(&length, "functions count");
           module->functions.reserve(SafeReserve(functions_count));
           for (uint32_t i = 0; i < functions_count; i++) {
             module->functions.push_back(
                 {nullptr, i, 0, 0, 0, 0, 0, 0, false, false});
             WasmFunction* function = &module->functions.back();
             function->sig_index = consume_sig_index(module, &function->sig);
           }
           break;
         }
-        case kDeclFunctionBodies: {
+        case WasmSection::Code::FunctionBodies: {
           // Function bodies should follow signatures.
-          CheckForPreviousSection(sections, kDeclFunctionSignatures, true);
+          CheckForPreviousSection(sections,
+                                  WasmSection::Code::FunctionSignatures, true);
           int length;
           const byte* pos = pc_;
           uint32_t functions_count = consume_u32v(&length, "functions count");
           if (functions_count != module->functions.size()) {
             error(pos, pos, "function body count %u mismatch (%u expected)",
                   functions_count,
                   static_cast<uint32_t>(module->functions.size()));
             break;
           }
           for (uint32_t i = 0; i < functions_count; i++) {
             WasmFunction* function = &module->functions[i];
             int length;
             uint32_t size = consume_u32v(&length, "body size");
             function->code_start_offset = pc_offset();
             function->code_end_offset = pc_offset() + size;
 
             TRACE("  +%d  %-20s: (%d bytes)\n", pc_offset(), "function body",
                   size);
             pc_ += size;
             if (pc_ > limit_) {
               error(pc_, "function body extends beyond end of file");
             }
           }
           break;
         }
-        case kDeclFunctions: {
+        case WasmSection::Code::Functions: {
           // Functions require a signature table first.
-          CheckForPreviousSection(sections, kDeclSignatures, true);
+          CheckForPreviousSection(sections, WasmSection::Code::Signatures,
+                                  true);
           int length;
           uint32_t functions_count = consume_u32v(&length, "functions count");
           module->functions.reserve(SafeReserve(functions_count));
           // Set up module environment for verification.
           ModuleEnv menv;
           menv.module = module;
           menv.instance = nullptr;
           menv.origin = origin_;
           // Decode functions.
           for (uint32_t i = 0; i < functions_count; i++) {
@@ skipping 12 matching lines @@
               WasmFunction* function = &module->functions[i];
               if (!function->external) {
                 VerifyFunctionBody(i, &menv, function);
                 if (result_.failed())
                   error(result_.error_pc, result_.error_msg.get());
               }
             }
           }
           break;
         }
-        case kDeclNames: {
+        case WasmSection::Code::Names: {
           // Names correspond to functions.
-          CheckForPreviousSection(sections, kDeclFunctionSignatures, true);
+          CheckForPreviousSection(sections,
+                                  WasmSection::Code::FunctionSignatures, true);
           int length;
           const byte* pos = pc_;
           uint32_t functions_count = consume_u32v(&length, "functions count");
           if (functions_count != module->functions.size()) {
             error(pos, pos, "function name count %u mismatch (%u expected)",
                   functions_count,
                   static_cast<uint32_t>(module->functions.size()));
             break;
           }
 
           for (uint32_t i = 0; i < functions_count; i++) {
             WasmFunction* function = &module->functions[i];
             function->name_offset =
                 consume_string(&function->name_length, "function name");
 
             uint32_t local_names_count =
                 consume_u32v(&length, "local names count");
             for (uint32_t j = 0; j < local_names_count; j++) {
               uint32_t unused = 0;
               uint32_t offset = consume_string(&unused, "local name");
               USE(unused);
               USE(offset);
             }
           }
           break;
         }
-        case kDeclGlobals: {
+        case WasmSection::Code::Globals: {
           int length;
           uint32_t globals_count = consume_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, 0, MachineType::Int32(), 0, false});
             WasmGlobal* global = &module->globals.back();
             DecodeGlobalInModule(global);
           }
           break;
         }
-        case kDeclDataSegments: {
+        case WasmSection::Code::DataSegments: {
           int length;
           uint32_t data_segments_count =
               consume_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(module, segment);
           }
           break;
         }
-        case kDeclFunctionTable: {
+        case WasmSection::Code::FunctionTable: {
           // An indirect function table requires functions first.
           CheckForFunctions(module, section);
           int length;
           uint32_t function_table_count =
               consume_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 = consume_u32v(&length);
             if (index >= module->functions.size()) {
               error(pc_ - 2, "invalid function index");
               break;
             }
             module->function_table.push_back(index);
           }
           break;
         }
-        case kDeclStartFunction: {
+        case WasmSection::Code::StartFunction: {
           // Declares a start function for a module.
           CheckForFunctions(module, section);
           if (module->start_function_index >= 0) {
             error("start function already declared");
             break;
           }
           WasmFunction* func;
           const byte* pos = pc_;
           module->start_function_index = consume_func_index(module, &func);
           if (func && func->sig->parameter_count() > 0) {
             error(pos, "invalid start function: non-zero parameter count");
             break;
           }
           break;
         }
-        case kDeclImportTable: {
+        case WasmSection::Code::ImportTable: {
           // Declares an import table.
-          CheckForPreviousSection(sections, kDeclSignatures, true);
+          CheckForPreviousSection(sections, WasmSection::Code::Signatures,
+                                  true);
           int length;
           uint32_t import_table_count =
               consume_u32v(&length, "import table count");
           module->import_table.reserve(SafeReserve(import_table_count));
           // Decode import table.
           for (uint32_t i = 0; i < import_table_count; i++) {
             if (failed()) break;
             TRACE("DecodeImportTable[%d] module+%d\n", i,
                   static_cast<int>(pc_ - start_));
 
             module->import_table.push_back({nullptr, 0, 0});
             WasmImport* import = &module->import_table.back();
 
             import->sig_index = consume_sig_index(module, &import->sig);
             const byte* pos = pc_;
             import->module_name_offset = consume_string(
                 &import->module_name_length, "import module name");
             if (import->module_name_length == 0) {
               error(pos, "import module name cannot be NULL");
             }
             import->function_name_offset = consume_string(
                 &import->function_name_length, "import function name");
           }
           break;
         }
-        case kDeclExportTable: {
+        case WasmSection::Code::ExportTable: {
           // Declares an export table.
           CheckForFunctions(module, section);
           int length;
           uint32_t export_table_count =
               consume_u32v(&length, "export table count");
           module->export_table.reserve(SafeReserve(export_table_count));
           // Decode export table.
           for (uint32_t i = 0; i < export_table_count; i++) {
             if (failed()) break;
             TRACE("DecodeExportTable[%d] module+%d\n", i,
                   static_cast<int>(pc_ - start_));
 
             module->export_table.push_back({0, 0});
             WasmExport* exp = &module->export_table.back();
 
             WasmFunction* func;
             exp->func_index = consume_func_index(module, &func);
             exp->name_offset = consume_string(&exp->name_length, "export name");
           }
           break;
         }
-        case kMaxModuleSectionCode:
+        case WasmSection::Code::Max:
           UNREACHABLE();  // Already skipped unknown sections.
       }
     }
 
     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;
   }
 
-  const char* SectionName(WasmSectionDeclCode section) {
-    switch (section) {
-      case kDeclMemory:
-        return "memory";
-      case kDeclSignatures:
-        return "signatures";
-      case kDeclFunctions:
-        return "function declaration";
-      case kDeclGlobals:
-        return "global variable";
-      case kDeclDataSegments:
-        return "data segment";
-      case kDeclFunctionTable:
-        return "function table";
-      default:
-        return "";
+  void CheckForFunctions(WasmModule* module, WasmSection::Code section) {
+    if (module->functions.size() == 0) {
+      error(pc_ - 1, nullptr, "functions must appear before section %s",
+            WasmSection::getName(section));
     }
   }
 
-  void CheckForFunctions(WasmModule* module, WasmSectionDeclCode section) {
-    if (module->functions.size() == 0) {
-      error(pc_ - 1, nullptr, "functions must appear before section %s",
-            SectionName(section));
+  void CheckForPreviousSection(bool* sections, WasmSection::Code section,
+                               bool present) {
+    if (section >= WasmSection::Code::Max) return;
+    if (sections[(size_t)section] == present) return;
+    if (present) {
+      error(pc_ - 1, nullptr, "required %s section missing",
+            WasmSection::getName(section));
+    } else {
+      error(pc_ - 1, nullptr, "%s section already present",
+            WasmSection::getName(section));
     }
   }
 
-  void CheckForPreviousSection(bool* sections, WasmSectionDeclCode section,
-                               bool present) {
-    if (section >= kMaxModuleSectionCode) return;
-    if (sections[section] == present) return;
-    const char* name = SectionName(section);
-    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 = consume_sig();               // read signature
     function->name_offset = 0;                   // ---- name
     function->name_length = 0;                   // ---- name length
     function->code_start_offset = off(pc_);      // ---- code start
     function->code_end_offset = off(limit_);     // ---- code end
     function->exported = false;                  // ---- exported
@@ skipping 193 matching lines @@
     if (func_index >= module->functions.size()) {
       error(pos, pos, "function index %u out of bounds (%d functions)",
             func_index, static_cast<int>(module->functions.size()));
       *func = nullptr;
       return 0;
     }
     *func = &module->functions[func_index];
     return func_index;
   }
 
+  // Reads a section name.
+  WasmSection::Code consume_section_name(int* string_leb_length,
+                                         uint32_t* string_length) {
+    *string_length = consume_u32v(string_leb_length, "name length");
+    const byte* start = pc_;
+    consume_bytes(*string_length);
+    if (failed()) {
+      TRACE("Section name of length %u couldn't be read\n", *string_length);
+      return WasmSection::Code::Max;
+    }
+    // TODO(jfb) Linear search, it may be better to do a common-prefix search.
+    for (WasmSection::Code i = WasmSection::begin(); i != WasmSection::end();
+         i = WasmSection::next(i)) {
+      if (WasmSection::getNameLength(i) == *string_length &&
+          0 == memcmp(WasmSection::getName(i), start, *string_length)) {
+        return i;
+      }
+    }
+    TRACE("Unknown section: '");
+    for (uint32_t i = 0; i != *string_length; ++i) TRACE("%c", *(start + i));
+    TRACE("'\n");
+    return WasmSection::Code::Max;
+  }
+
   // Reads a single 8-bit integer, interpreting it as a local type.
   LocalType consume_local_type() {
     byte val = consume_u8("local type");
     LocalTypeCode t = static_cast<LocalTypeCode>(val);
     switch (t) {
       case kLocalVoid:
         return kAstStmt;
       case kLocalI32:
         return kAstI32;
       case kLocalI64:
@@ skipping 111 matching lines @@
   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, kWasmOrigin);
   return decoder.DecodeSingleFunction(module_env, function);
 }
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8