include/llvm/DebugInfo/MSF/MSFCommon.h

   1 //===- MSFCommon.h - Common types and functions for MSF files ---*- 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_DEBUGINFO_MSF_MSFCOMMON_H
  10 #define LLVM_DEBUGINFO_MSF_MSFCOMMON_H
  11
  12 #include "llvm/ADT/ArrayRef.h"
  13 #include "llvm/ADT/BitVector.h"
  14 #include "llvm/Support/Endian.h"
  15 #include "llvm/Support/Error.h"
  16 #include "llvm/Support/MathExtras.h"
  17 #include <cstdint>
  18 #include <vector>
  19
  20 namespace llvm {
  21 namespace msf {
  22
  23 static const char Magic[] = {'M',  'i',  'c',    'r', 'o', 's',  'o',  'f',
  24                              't',  ' ',  'C',    '/', 'C', '+',  '+',  ' ',
  25                              'M',  'S',  'F',    ' ', '7', '.',  '0',  '0',
  26                              '\r', '\n', '\x1a', 'D', 'S', '\0', '\0', '\0'};
  27
  28 // The superblock is overlaid at the beginning of the file (offset 0).
  29 // It starts with a magic header and is followed by information which
  30 // describes the layout of the file system.
  31 struct SuperBlock {
  32   char MagicBytes[sizeof(Magic)];
  33   // The file system is split into a variable number of fixed size elements.
  34   // These elements are referred to as blocks.  The size of a block may vary
  35   // from system to system.
  36   support::ulittle32_t BlockSize;
  37   // The index of the free block map.
  38   support::ulittle32_t FreeBlockMapBlock;
  39   // This contains the number of blocks resident in the file system.  In
  40   // practice, NumBlocks * BlockSize is equivalent to the size of the MSF
  41   // file.
  42   support::ulittle32_t NumBlocks;
  43   // This contains the number of bytes which make up the directory.
  44   support::ulittle32_t NumDirectoryBytes;
  45   // This field's purpose is not yet known.
  46   support::ulittle32_t Unknown1;
  47   // This contains the block # of the block map.
  48   support::ulittle32_t BlockMapAddr;
  49 };
  50
  51 struct MSFLayout {
  52   MSFLayout() = default;
  53
  54   uint32_t mainFpmBlock() const {
  55     assert(SB->FreeBlockMapBlock == 1 || SB->FreeBlockMapBlock == 2);
  56     return SB->FreeBlockMapBlock;
  57   }
  58
  59   uint32_t alternateFpmBlock() const {
  60     // If mainFpmBlock is 1, this is 2.  If mainFpmBlock is 2, this is 1.
  61     return 3U - mainFpmBlock();
  62   }
  63
  64   const SuperBlock *SB = nullptr;
  65   BitVector FreePageMap;
  66   ArrayRef<support::ulittle32_t> DirectoryBlocks;
  67   ArrayRef<support::ulittle32_t> StreamSizes;
  68   std::vector<ArrayRef<support::ulittle32_t>> StreamMap;
  69 };
  70
  71 /// Describes the layout of a stream in an MSF layout.  A "stream" here
  72 /// is defined as any logical unit of data which may be arranged inside the MSF
  73 /// file as a sequence of (possibly discontiguous) blocks.  When we want to read
  74 /// from a particular MSF Stream, we fill out a stream layout structure and the
  75 /// reader uses it to determine which blocks in the underlying MSF file contain
  76 /// the data, so that it can be pieced together in the right order.
  77 class MSFStreamLayout {
  78 public:
  79   uint32_t Length;
  80   std::vector<support::ulittle32_t> Blocks;
  81 };
  82
  83 /// Determine the layout of the FPM stream, given the MSF layout.  An FPM
  84 /// stream spans 1 or more blocks, each at equally spaced intervals throughout
  85 /// the file.
  86 MSFStreamLayout getFpmStreamLayout(const MSFLayout &Msf,
  87                                    bool IncludeUnusedFpmData = false,
  88                                    bool AltFpm = false);
  89
  90 inline bool isValidBlockSize(uint32_t Size) {
  91   switch (Size) {
  92   case 512:
  93   case 1024:
  94   case 2048:
  95   case 4096:
  96     return true;
  97   }
  98   return false;
  99 }
 100
 101 // Super Block, Fpm0, Fpm1, and Block Map
 102 inline uint32_t getMinimumBlockCount() { return 4; }
 103
 104 // Super Block, Fpm0, and Fpm1 are reserved.  The Block Map, although required
 105 // need not be at block 3.
 106 inline uint32_t getFirstUnreservedBlock() { return 3; }
 107
 108 inline uint64_t bytesToBlocks(uint64_t NumBytes, uint64_t BlockSize) {
 109   return divideCeil(NumBytes, BlockSize);
 110 }
 111
 112 inline uint64_t blockToOffset(uint64_t BlockNumber, uint64_t BlockSize) {
 113   return BlockNumber * BlockSize;
 114 }
 115
 116 inline uint32_t getFpmIntervalLength(const MSFLayout &L) {
 117   return L.SB->BlockSize;
 118 }
 119
 120 /// Given an MSF with the specified block size and number of blocks, determine
 121 /// how many pieces the specified Fpm is split into.
 122 /// \p BlockSize - the block size of the MSF
 123 /// \p NumBlocks - the total number of blocks in the MSF
 124 /// \p IncludeUnusedFpmData - When true, this will count every block that is
 125 ///    both in the file and matches the form of an FPM block, even if some of
 126 ///    those FPM blocks are unused (a single FPM block can describe the
 127 ///    allocation status of up to 32,767 blocks, although one appears only
 128 ///    every 4,096 blocks).  So there are 8x as many blocks that match the
 129 ///    form as there are blocks that are necessary to describe the allocation
 130 ///    status of the file.  When this parameter is false, these extraneous
 131 ///    trailing blocks are not counted.
 132 inline uint32_t getNumFpmIntervals(uint32_t BlockSize, uint32_t NumBlocks,
 133                                    bool IncludeUnusedFpmData, int FpmNumber) {
 134   assert(FpmNumber == 1 || FpmNumber == 2);
 135   if (IncludeUnusedFpmData) {
 136     // This calculation determines how many times a number of the form
 137     // BlockSize * k + N appears in the range [0, NumBlocks).  We only need to
 138     // do this when unused data is included, since the number of blocks dwarfs
 139     // the number of fpm blocks.
 140     return divideCeil(NumBlocks - FpmNumber, BlockSize);
 141   }
 142
 143   // We want the minimum number of intervals required, where each interval can
 144   // represent BlockSize * 8 blocks.
 145   return divideCeil(NumBlocks, 8 * BlockSize);
 146 }
 147
 148 inline uint32_t getNumFpmIntervals(const MSFLayout &L,
 149                                    bool IncludeUnusedFpmData = false,
 150                                    bool AltFpm = false) {
 151   return getNumFpmIntervals(L.SB->BlockSize, L.SB->NumBlocks,
 152                             IncludeUnusedFpmData,
 153                             AltFpm ? L.alternateFpmBlock() : L.mainFpmBlock());
 154 }
 155
 156 Error validateSuperBlock(const SuperBlock &SB);
 157
 158 } // end namespace msf
 159 } // end namespace llvm
 160
 161 #endif // LLVM_DEBUGINFO_MSF_MSFCOMMON_H