llvm/lib/ObjCopy/MachO/MachOLayoutBuilder.h

   1 //===- MachOLayoutBuilder.h -------------------------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef LLVM_LIB_OBJCOPY_MACHO_MACHOLAYOUTBUILDER_H
  10 #define LLVM_LIB_OBJCOPY_MACHO_MACHOLAYOUTBUILDER_H
  11
  12 #include "MachOObject.h"
  13 #include "llvm/ObjCopy/MachO/MachOObjcopy.h"
  14
  15 namespace llvm {
  16 namespace objcopy {
  17 namespace macho {
  18
  19 /// When MachO binaries include a LC_CODE_SIGNATURE load command,
  20 /// the __LINKEDIT data segment will include a section corresponding
  21 /// to the LC_CODE_SIGNATURE load command. This section serves as a signature
  22 /// for the binary. Included in the CodeSignature section is a header followed
  23 /// by a hash of the binary. If present, the CodeSignature section is the
  24 /// last component of the binary.
  25 struct CodeSignatureInfo {
  26   // NOTE: These values are to be kept in sync with those in
  27   // LLD's CodeSignatureSection class.
  28
  29   static constexpr uint32_t Align = 16;
  30   static constexpr uint8_t BlockSizeShift = 12;
  31   // The binary is read in blocks of the following size.
  32   static constexpr size_t BlockSize = (1 << BlockSizeShift); // 4 KiB
  33   // For each block, a SHA256 hash (256 bits, 32 bytes) is written to
  34   // the CodeSignature section.
  35   static constexpr size_t HashSize = 256 / 8;
  36   static constexpr size_t BlobHeadersSize = llvm::alignTo<8>(
  37       sizeof(llvm::MachO::CS_SuperBlob) + sizeof(llvm::MachO::CS_BlobIndex));
  38   // The size of the entire header depends upon the filename the binary is being
  39   // written to, but the rest of the header is fixed in size.
  40   static constexpr uint32_t FixedHeadersSize =
  41       BlobHeadersSize + sizeof(llvm::MachO::CS_CodeDirectory);
  42
  43   // The offset relative to the start of the binary where
  44   // the CodeSignature section should begin.
  45   uint32_t StartOffset;
  46   // The size of the entire header, output file name size included.
  47   uint32_t AllHeadersSize;
  48   // The number of blocks required to hash the binary.
  49   uint32_t BlockCount;
  50   StringRef OutputFileName;
  51   // The size of the entire CodeSignature section, including both the header and
  52   // hashes.
  53   uint32_t Size;
  54 };
  55
  56 class MachOLayoutBuilder {
  57   Object &O;
  58   bool Is64Bit;
  59   StringRef OutputFileName;
  60   uint64_t PageSize;
  61   CodeSignatureInfo CodeSignature;
  62
  63   // Points to the __LINKEDIT segment if it exists.
  64   MachO::macho_load_command *LinkEditLoadCommand = nullptr;
  65   StringTableBuilder StrTableBuilder;
  66
  67   uint32_t computeSizeOfCmds() const;
  68   void constructStringTable();
  69   void updateSymbolIndexes();
  70   void updateDySymTab(MachO::macho_load_command &MLC);
  71   uint64_t layoutSegments();
  72   uint64_t layoutRelocations(uint64_t Offset);
  73   Error layoutTail(uint64_t Offset);
  74
  75   static StringTableBuilder::Kind getStringTableBuilderKind(const Object &O,
  76                                                             bool Is64Bit);
  77
  78 public:
  79   MachOLayoutBuilder(Object &O, bool Is64Bit, StringRef OutputFileName,
  80                      uint64_t PageSize)
  81       : O(O), Is64Bit(Is64Bit), OutputFileName(OutputFileName),
  82         PageSize(PageSize),
  83         StrTableBuilder(getStringTableBuilderKind(O, Is64Bit)) {}
  84
  85   // Recomputes and updates fields in the given object such as file offsets.
  86   Error layout();
  87
  88   StringTableBuilder &getStringTableBuilder() { return StrTableBuilder; }
  89
  90   const CodeSignatureInfo &getCodeSignature() const { return CodeSignature; }
  91 };
  92
  93 } // end namespace macho
  94 } // end namespace objcopy
  95 } // end namespace llvm
  96
  97 #endif // LLVM_LIB_OBJCOPY_MACHO_MACHOLAYOUTBUILDER_H