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
20namespace llvm {
21namespace msf {
22
23static 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.
31struct 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
51struct 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.
77class MSFStreamLayout {
78public:
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.
86MSFStreamLayout getFpmStreamLayout(const MSFLayout &Msf,
87 bool IncludeUnusedFpmData = false,
88 bool AltFpm = false);
89
90inline bool isValidBlockSize(uint32_t Size) {
91 switch (Size) {
92 case 512:
93 case 1024:
94 case 2048:
95 case 4096:
96 case 8192:
97 case 16384:
98 case 32768:
99 return true;
100 }
101 return false;
102}
103
104/// Given the specified block size, returns the maximum possible file size.
105/// Block Size | Max File Size
106/// <= 4096 | 4GB
107/// 8192 | 8GB
108/// 16384 | 16GB
109/// 32768 | 32GB
110/// \p Size - the block size of the MSF
111inline uint64_t getMaxFileSizeFromBlockSize(uint32_t Size) {
112 switch (Size) {
113 case 8192:
114 return (uint64_t)UINT32_MAX * 2ULL;
115 case 16384:
116 return (uint64_t)UINT32_MAX * 3ULL;
117 case 32768:
118 return (uint64_t)UINT32_MAX * 4ULL;
119 default:
120 return (uint64_t)UINT32_MAX;
121 }
122}
123
124// Super Block, Fpm0, Fpm1, and Block Map
125inline uint32_t getMinimumBlockCount() { return 4; }
126
127// Super Block, Fpm0, and Fpm1 are reserved. The Block Map, although required
128// need not be at block 3.
129inline uint32_t getFirstUnreservedBlock() { return 3; }
130
131inline uint64_t bytesToBlocks(uint64_t NumBytes, uint64_t BlockSize) {
132 return divideCeil(Numerator: NumBytes, Denominator: BlockSize);
133}
134
135inline uint64_t blockToOffset(uint64_t BlockNumber, uint64_t BlockSize) {
136 return BlockNumber * BlockSize;
137}
138
139inline uint32_t getFpmIntervalLength(const MSFLayout &L) {
140 return L.SB->BlockSize;
141}
142
143/// Given an MSF with the specified block size and number of blocks, determine
144/// how many pieces the specified Fpm is split into.
145/// \p BlockSize - the block size of the MSF
146/// \p NumBlocks - the total number of blocks in the MSF
147/// \p IncludeUnusedFpmData - When true, this will count every block that is
148/// both in the file and matches the form of an FPM block, even if some of
149/// those FPM blocks are unused (a single FPM block can describe the
150/// allocation status of up to 32,767 blocks, although one appears only
151/// every 4,096 blocks). So there are 8x as many blocks that match the
152/// form as there are blocks that are necessary to describe the allocation
153/// status of the file. When this parameter is false, these extraneous
154/// trailing blocks are not counted.
155inline uint32_t getNumFpmIntervals(uint32_t BlockSize, uint32_t NumBlocks,
156 bool IncludeUnusedFpmData, int FpmNumber) {
157 assert(FpmNumber == 1 || FpmNumber == 2);
158 if (IncludeUnusedFpmData) {
159 // This calculation determines how many times a number of the form
160 // BlockSize * k + N appears in the range [0, NumBlocks). We only need to
161 // do this when unused data is included, since the number of blocks dwarfs
162 // the number of fpm blocks.
163 return divideCeil(Numerator: NumBlocks - FpmNumber, Denominator: BlockSize);
164 }
165
166 // We want the minimum number of intervals required, where each interval can
167 // represent BlockSize * 8 blocks.
168 return divideCeil(Numerator: NumBlocks, Denominator: 8 * BlockSize);
169}
170
171inline uint32_t getNumFpmIntervals(const MSFLayout &L,
172 bool IncludeUnusedFpmData = false,
173 bool AltFpm = false) {
174 return getNumFpmIntervals(BlockSize: L.SB->BlockSize, NumBlocks: L.SB->NumBlocks,
175 IncludeUnusedFpmData,
176 FpmNumber: AltFpm ? L.alternateFpmBlock() : L.mainFpmBlock());
177}
178
179Error validateSuperBlock(const SuperBlock &SB);
180
181} // end namespace msf
182} // end namespace llvm
183
184#endif // LLVM_DEBUGINFO_MSF_MSFCOMMON_H
185