embedded-file-writer.h

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// Copyright 2018 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.
 
#ifndef V8_SNAPSHOT_EMBEDDED_EMBEDDED_FILE_WRITER_H_
#define V8_SNAPSHOT_EMBEDDED_EMBEDDED_FILE_WRITER_H_
 
#include <cinttypes>
#include <cstdio>
#include <cstring>
#include <memory>
 
#include "src/base/platform/wrappers.h"
#include "src/base/strings.h"
#include "src/common/globals.h"
#include "src/snapshot/embedded/embedded-data.h"
#include "src/snapshot/embedded/embedded-file-writer-interface.h"
#include "src/snapshot/embedded/platform-embedded-file-writer-base.h"
 
#if defined(V8_OS_WIN64)
#include "src/diagnostics/unwinding-info-win64.h"
#endif  // V8_OS_WIN64
 
namespace v8 {
namespace internal {
// Generates the embedded.S file which is later compiled into the final v8
// binary. Its contents are exported through two symbols:
//
// v8_<variant>_embedded_blob_ (intptr_t):
//     a pointer to the start of the embedded blob.
// v8_<variant>_embedded_blob_size_ (uint32_t):
//     size of the embedded blob in bytes.
//
// The variant is usually "Default" but can be modified in multisnapshot builds.
class EmbeddedFileWriter : public EmbeddedFileWriterInterface {
 public:
  int LookupOrAddExternallyCompiledFilename(const char* filename) override;
  const char* GetExternallyCompiledFilename(int fileid) const override;
  int GetExternallyCompiledFilenameCount() const override;
 
  void PrepareBuiltinSourcePositionMap(Builtins* builtins) override;
 
#if defined(V8_OS_WIN64)
  void SetBuiltinUnwindData(
      Builtin builtin,
      const win64_unwindinfo::BuiltinUnwindInfo& unwinding_info) override {
    DCHECK_LT(static_cast<int>(builtin), Builtins::kBuiltinCount);
    unwind_infos_[static_cast<int>(builtin)] = unwinding_info;
  }
#endif  // V8_OS_WIN64
 
  void SetEmbeddedFile(const char* embedded_src_path) {
    embedded_src_path_ = embedded_src_path;
  }
 
  void SetEmbeddedVariant(const char* embedded_variant) {
    if (embedded_variant == nullptr) return;
    embedded_variant_ = embedded_variant;
  }
 
  void SetTargetArch(const char* target_arch) { target_arch_ = target_arch; }
 
  void SetTargetOs(const char* target_os) { target_os_ = target_os; }
 
  void WriteEmbedded(const i::EmbeddedData* blob) const {
    MaybeWriteEmbeddedFile(blob);
  }
 
 private:
  void MaybeWriteEmbeddedFile(const i::EmbeddedData* blob) const {
    if (embedded_src_path_ == nullptr) return;
 
    FILE* fp = GetFileDescriptorOrDie(embedded_src_path_);
 
    std::unique_ptr<PlatformEmbeddedFileWriterBase> writer =
        NewPlatformEmbeddedFileWriter(target_arch_, target_os_);
    writer->SetFile(fp);
 
    WriteFilePrologue(writer.get());
    WriteExternalFilenames(writer.get());
    WriteDataSection(writer.get(), blob);
    WriteCodeSection(writer.get(), blob);
    WriteFileEpilogue(writer.get(), blob);
 
    base::Fclose(fp);
  }
 
  static FILE* GetFileDescriptorOrDie(const char* filename) {
    FILE* fp = v8::base::OS::FOpen(filename, "w");
 
    if (fp == nullptr) {
      i::PrintF("Unable to open file \"%s\" for writing.\n", filename);
      exit(1);
    }
    return fp;
  }
 
  void WriteFilePrologue(PlatformEmbeddedFileWriterBase* w) const {
    w->Comment("Autogenerated file. Do not edit.");
    w->Newline();
    w->FilePrologue();
  }
 
  void WriteExternalFilenames(PlatformEmbeddedFileWriterBase* w) const {
#ifndef DEBUG
    // Release builds must not contain debug infos.
    CHECK_EQ(external_filenames_by_index_.size(), 0);
#endif
 
    w->Comment(
        "Source positions in the embedded blob refer to filenames by id.");
    w->Comment("Assembly directives here map the id to a filename.");
    w->Newline();
 
    // Write external filenames.
    int size = static_cast<int>(external_filenames_by_index_.size());
    for (int i = 0; i < size; i++) {
      w->DeclareExternalFilename(ExternalFilenameIndexToId(i),
                                 external_filenames_by_index_[i]);
    }
  }
 
  // Fairly arbitrary but should fit all symbol names.
  static constexpr int kTemporaryStringLength = 256;
 
  std::string EmbeddedBlobCodeSymbol() const {
    base::EmbeddedVector<char, kTemporaryStringLength>
        embedded_blob_code_symbol;
    base::SNPrintF(embedded_blob_code_symbol, "v8_%s_embedded_blob_code_",
                   embedded_variant_);
    return std::string{embedded_blob_code_symbol.begin()};
  }
 
  std::string EmbeddedBlobDataSymbol() const {
    base::EmbeddedVector<char, kTemporaryStringLength>
        embedded_blob_data_symbol;
    base::SNPrintF(embedded_blob_data_symbol, "v8_%s_embedded_blob_data_",
                   embedded_variant_);
    return std::string{embedded_blob_data_symbol.begin()};
  }
 
  void WriteDataSection(PlatformEmbeddedFileWriterBase* w,
                        const i::EmbeddedData* blob) const {
    w->Comment("The embedded blob data section starts here.");
    w->SectionRoData();
    w->AlignToDataAlignment();
    w->DeclareSymbolGlobal(EmbeddedBlobDataSymbol().c_str());
    w->DeclareLabelProlog(EmbeddedBlobDataSymbol().c_str());
    w->DeclareLabel(EmbeddedBlobDataSymbol().c_str());
 
    WriteBinaryContentsAsInlineAssembly(w, blob->data(), blob->data_size());
    w->DeclareLabelEpilogue();
    w->Newline();
  }
 
  void WriteBuiltin(PlatformEmbeddedFileWriterBase* w,
                    const i::EmbeddedData* blob, const Builtin builtin) const;
 
  void WriteBuiltinLabels(PlatformEmbeddedFileWriterBase* w,
                          std::string name) const;
 
  void WriteCodeSection(PlatformEmbeddedFileWriterBase* w,
                        const i::EmbeddedData* blob) const;
 
  void WriteFileEpilogue(PlatformEmbeddedFileWriterBase* w,
                         const i::EmbeddedData* blob) const;
 
#if defined(V8_OS_WIN_X64)
  void WriteUnwindInfoEntry(PlatformEmbeddedFileWriterBase* w,
                            uint64_t rva_start, uint64_t rva_end) const;
#endif
 
  static void WriteBinaryContentsAsInlineAssembly(
      PlatformEmbeddedFileWriterBase* w, const uint8_t* data, uint32_t size);
 
  // In assembly directives, filename ids need to begin with 1.
  static constexpr int kFirstExternalFilenameId = 1;
  static int ExternalFilenameIndexToId(int index) {
    return kFirstExternalFilenameId + index;
  }
  static int ExternalFilenameIdToIndex(int id) {
    return id - kFirstExternalFilenameId;
  }
 
 private:
  std::vector<uint8_t> source_positions_[Builtins::kBuiltinCount];
  std::vector<LabelInfo> label_info_[Builtins::kBuiltinCount];
 
#if defined(V8_OS_WIN64)
  win64_unwindinfo::BuiltinUnwindInfo unwind_infos_[Builtins::kBuiltinCount];
#endif  // V8_OS_WIN64
 
  std::map<const char*, int> external_filenames_;
  std::vector<const char*> external_filenames_by_index_;
 
  // The file to generate or nullptr.
  const char* embedded_src_path_ = nullptr;
 
  // The variant is only used in multi-snapshot builds and otherwise set to
  // "Default".
  const char* embedded_variant_ = kDefaultEmbeddedVariant;
 
  // {target_arch} and {target_os} control the generated assembly format. Note
  // these may differ from both host- and target-platforms specified through
  // e.g. V8_OS_* and V8_TARGET_ARCH_* defines.
  const char* target_arch_ = nullptr;
  const char* target_os_ = nullptr;
};
 
}  // namespace internal
}  // namespace v8
 
#endif  // V8_SNAPSHOT_EMBEDDED_EMBEDDED_FILE_WRITER_H_