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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 
mainFpmBlockMSFLayout55   uint32_t mainFpmBlock() const {
56     assert(SB->FreeBlockMapBlock == 1 || SB->FreeBlockMapBlock == 2);
57     return SB->FreeBlockMapBlock;
58   }
59 
alternateFpmBlockMSFLayout60   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 
isValidBlockSize(uint32_t Size)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
getMinimumBlockCount()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.
getFirstUnreservedBlock()107 inline uint32_t getFirstUnreservedBlock() { return 3; }
108 
bytesToBlocks(uint64_t NumBytes,uint64_t BlockSize)109 inline uint64_t bytesToBlocks(uint64_t NumBytes, uint64_t BlockSize) {
110   return divideCeil(NumBytes, BlockSize);
111 }
112 
blockToOffset(uint64_t BlockNumber,uint64_t BlockSize)113 inline uint64_t blockToOffset(uint64_t BlockNumber, uint64_t BlockSize) {
114   return BlockNumber * BlockSize;
115 }
116 
getFpmIntervalLength(const MSFLayout & L)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.
getNumFpmIntervals(uint32_t BlockSize,uint32_t NumBlocks,bool IncludeUnusedFpmData,int FpmNumber)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