1 //===- MSFCommon.h - Common types and functions for MSF files ---*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 10 #ifndef LLVM_DEBUGINFO_MSF_MSFCOMMON_H 11 #define LLVM_DEBUGINFO_MSF_MSFCOMMON_H 12 13 #include "llvm/ADT/ArrayRef.h" 14 #include "llvm/ADT/BitVector.h" 15 #include "llvm/Support/Endian.h" 16 #include "llvm/Support/Error.h" 17 #include "llvm/Support/MathExtras.h" 18 #include <cstdint> 19 #include <vector> 20 21 namespace llvm { 22 namespace msf { 23 24 static const char Magic[] = {'M', 'i', 'c', 'r', 'o', 's', 'o', 'f', 25 't', ' ', 'C', '/', 'C', '+', '+', ' ', 26 'M', 'S', 'F', ' ', '7', '.', '0', '0', 27 '\r', '\n', '\x1a', 'D', 'S', '\0', '\0', '\0'}; 28 29 // The superblock is overlaid at the beginning of the file (offset 0). 30 // It starts with a magic header and is followed by information which 31 // describes the layout of the file system. 32 struct SuperBlock { 33 char MagicBytes[sizeof(Magic)]; 34 // The file system is split into a variable number of fixed size elements. 35 // These elements are referred to as blocks. The size of a block may vary 36 // from system to system. 37 support::ulittle32_t BlockSize; 38 // The index of the free block map. 39 support::ulittle32_t FreeBlockMapBlock; 40 // This contains the number of blocks resident in the file system. In 41 // practice, NumBlocks * BlockSize is equivalent to the size of the MSF 42 // file. 43 support::ulittle32_t NumBlocks; 44 // This contains the number of bytes which make up the directory. 45 support::ulittle32_t NumDirectoryBytes; 46 // This field's purpose is not yet known. 47 support::ulittle32_t Unknown1; 48 // This contains the block # of the block map. 49 support::ulittle32_t BlockMapAddr; 50 }; 51 52 struct MSFLayout { 53 MSFLayout() = default; 54 55 uint32_t mainFpmBlock() const { 56 assert(SB->FreeBlockMapBlock == 1 || SB->FreeBlockMapBlock == 2); 57 return SB->FreeBlockMapBlock; 58 } 59 60 uint32_t alternateFpmBlock() const { 61 // If mainFpmBlock is 1, this is 2. If mainFpmBlock is 2, this is 1. 62 return 3U - mainFpmBlock(); 63 } 64 65 const SuperBlock *SB = nullptr; 66 BitVector FreePageMap; 67 ArrayRef<support::ulittle32_t> DirectoryBlocks; 68 ArrayRef<support::ulittle32_t> StreamSizes; 69 std::vector<ArrayRef<support::ulittle32_t>> StreamMap; 70 }; 71 72 /// Describes the layout of a stream in an MSF layout. A "stream" here 73 /// is defined as any logical unit of data which may be arranged inside the MSF 74 /// file as a sequence of (possibly discontiguous) blocks. When we want to read 75 /// from a particular MSF Stream, we fill out a stream layout structure and the 76 /// reader uses it to determine which blocks in the underlying MSF file contain 77 /// the data, so that it can be pieced together in the right order. 78 class MSFStreamLayout { 79 public: 80 uint32_t Length; 81 std::vector<support::ulittle32_t> Blocks; 82 }; 83 84 /// Determine the layout of the FPM stream, given the MSF layout. An FPM 85 /// stream spans 1 or more blocks, each at equally spaced intervals throughout 86 /// the file. 87 MSFStreamLayout getFpmStreamLayout(const MSFLayout &Msf, 88 bool IncludeUnusedFpmData = false, 89 bool AltFpm = false); 90 91 inline bool isValidBlockSize(uint32_t Size) { 92 switch (Size) { 93 case 512: 94 case 1024: 95 case 2048: 96 case 4096: 97 return true; 98 } 99 return false; 100 } 101 102 // Super Block, Fpm0, Fpm1, and Block Map 103 inline uint32_t getMinimumBlockCount() { return 4; } 104 105 // Super Block, Fpm0, and Fpm1 are reserved. The Block Map, although required 106 // need not be at block 3. 107 inline uint32_t getFirstUnreservedBlock() { return 3; } 108 109 inline uint64_t bytesToBlocks(uint64_t NumBytes, uint64_t BlockSize) { 110 return divideCeil(NumBytes, BlockSize); 111 } 112 113 inline uint64_t blockToOffset(uint64_t BlockNumber, uint64_t BlockSize) { 114 return BlockNumber * BlockSize; 115 } 116 117 inline uint32_t getFpmIntervalLength(const MSFLayout &L) { 118 return L.SB->BlockSize; 119 } 120 121 /// Given an MSF with the specified block size and number of blocks, determine 122 /// how many pieces the specified Fpm is split into. 123 /// \p BlockSize - the block size of the MSF 124 /// \p NumBlocks - the total number of blocks in the MSF 125 /// \p IncludeUnusedFpmData - When true, this will count every block that is 126 /// both in the file and matches the form of an FPM block, even if some of 127 /// those FPM blocks are unused (a single FPM block can describe the 128 /// allocation status of up to 32,767 blocks, although one appears only 129 /// every 4,096 blocks). So there are 8x as many blocks that match the 130 /// form as there are blocks that are necessary to describe the allocation 131 /// status of the file. When this parameter is false, these extraneous 132 /// trailing blocks are not counted. 133 inline uint32_t getNumFpmIntervals(uint32_t BlockSize, uint32_t NumBlocks, 134 bool IncludeUnusedFpmData, int FpmNumber) { 135 assert(FpmNumber == 1 || FpmNumber == 2); 136 if (IncludeUnusedFpmData) { 137 // This calculation determines how many times a number of the form 138 // BlockSize * k + N appears in the range [0, NumBlocks). We only need to 139 // do this when unused data is included, since the number of blocks dwarfs 140 // the number of fpm blocks. 141 return divideCeil(NumBlocks - FpmNumber, BlockSize); 142 } 143 144 // We want the minimum number of intervals required, where each interval can 145 // represent BlockSize * 8 blocks. 146 return divideCeil(NumBlocks, 8 * BlockSize); 147 } 148 149 inline uint32_t getNumFpmIntervals(const MSFLayout &L, 150 bool IncludeUnusedFpmData = false, 151 bool AltFpm = false) { 152 return getNumFpmIntervals(L.SB->BlockSize, L.SB->NumBlocks, 153 IncludeUnusedFpmData, 154 AltFpm ? L.alternateFpmBlock() : L.mainFpmBlock()); 155 } 156 157 Error validateSuperBlock(const SuperBlock &SB); 158 159 } // end namespace msf 160 } // end namespace llvm 161 162 #endif // LLVM_DEBUGINFO_MSF_MSFCOMMON_H 163