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 162