1//===- MachOLayoutBuilder.h -------------------------------------*- 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_LIB_OBJCOPY_MACHO_MACHOLAYOUTBUILDER_H
10#define LLVM_LIB_OBJCOPY_MACHO_MACHOLAYOUTBUILDER_H
11
12#include "MachOObject.h"
13#include "llvm/ObjCopy/MachO/MachOObjcopy.h"
14
15namespace llvm {
16namespace objcopy {
17namespace macho {
18
19/// When MachO binaries include a LC_CODE_SIGNATURE load command,
20/// the __LINKEDIT data segment will include a section corresponding
21/// to the LC_CODE_SIGNATURE load command. This section serves as a signature
22/// for the binary. Included in the CodeSignature section is a header followed
23/// by a hash of the binary. If present, the CodeSignature section is the
24/// last component of the binary.
25struct CodeSignatureInfo {
26 // NOTE: These values are to be kept in sync with those in
27 // LLD's CodeSignatureSection class.
28
29 static constexpr uint32_t Align = 16;
30 static constexpr uint8_t BlockSizeShift = 12;
31 // The binary is read in blocks of the following size.
32 static constexpr size_t BlockSize = (1 << BlockSizeShift); // 4 KiB
33 // For each block, a SHA256 hash (256 bits, 32 bytes) is written to
34 // the CodeSignature section.
35 static constexpr size_t HashSize = 256 / 8;
36 static constexpr size_t BlobHeadersSize = llvm::alignTo<8>(
37 Value: sizeof(llvm::MachO::CS_SuperBlob) + sizeof(llvm::MachO::CS_BlobIndex));
38 // The size of the entire header depends upon the filename the binary is being
39 // written to, but the rest of the header is fixed in size.
40 static constexpr uint32_t FixedHeadersSize =
41 BlobHeadersSize + sizeof(llvm::MachO::CS_CodeDirectory);
42
43 // The offset relative to the start of the binary where
44 // the CodeSignature section should begin.
45 uint32_t StartOffset;
46 // The size of the entire header, output file name size included.
47 uint32_t AllHeadersSize;
48 // The number of blocks required to hash the binary.
49 uint32_t BlockCount;
50 StringRef OutputFileName;
51 // The size of the entire CodeSignature section, including both the header and
52 // hashes.
53 uint32_t Size;
54};
55
56class MachOLayoutBuilder {
57 Object &O;
58 bool Is64Bit;
59 StringRef OutputFileName;
60 uint64_t PageSize;
61 CodeSignatureInfo CodeSignature;
62
63 // Points to the __LINKEDIT segment if it exists.
64 MachO::macho_load_command *LinkEditLoadCommand = nullptr;
65 StringTableBuilder StrTableBuilder;
66
67 uint32_t computeSizeOfCmds() const;
68 void constructStringTable();
69 void updateSymbolIndexes();
70 void updateDySymTab(MachO::macho_load_command &MLC);
71 uint64_t layoutSegments();
72 uint64_t layoutRelocations(uint64_t Offset);
73 Error layoutTail(uint64_t Offset);
74
75 static StringTableBuilder::Kind getStringTableBuilderKind(const Object &O,
76 bool Is64Bit);
77
78public:
79 MachOLayoutBuilder(Object &O, bool Is64Bit, StringRef OutputFileName,
80 uint64_t PageSize)
81 : O(O), Is64Bit(Is64Bit), OutputFileName(OutputFileName),
82 PageSize(PageSize),
83 StrTableBuilder(getStringTableBuilderKind(O, Is64Bit)) {}
84
85 // Recomputes and updates fields in the given object such as file offsets.
86 Error layout();
87
88 StringTableBuilder &getStringTableBuilder() { return StrTableBuilder; }
89
90 const CodeSignatureInfo &getCodeSignature() const { return CodeSignature; }
91};
92
93} // end namespace macho
94} // end namespace objcopy
95} // end namespace llvm
96
97#endif // LLVM_LIB_OBJCOPY_MACHO_MACHOLAYOUTBUILDER_H
98