1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
|
//===- MachOObject.cpp - Mach-O object file model ---------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "MachOObject.h"
#include "llvm/ADT/SmallPtrSet.h"
#include <unordered_set>
using namespace llvm;
using namespace llvm::objcopy::macho;
Section::Section(StringRef SegName, StringRef SectName)
: Segname(SegName), Sectname(SectName),
CanonicalName((Twine(SegName) + Twine(',') + SectName).str()) {}
Section::Section(StringRef SegName, StringRef SectName, StringRef Content)
: Segname(SegName), Sectname(SectName),
CanonicalName((Twine(SegName) + Twine(',') + SectName).str()),
Content(Content) {}
const SymbolEntry *SymbolTable::getSymbolByIndex(uint32_t Index) const {
assert(Index < Symbols.size() && "invalid symbol index");
return Symbols[Index].get();
}
SymbolEntry *SymbolTable::getSymbolByIndex(uint32_t Index) {
return const_cast<SymbolEntry *>(
static_cast<const SymbolTable *>(this)->getSymbolByIndex(Index));
}
void SymbolTable::removeSymbols(
function_ref<bool(const std::unique_ptr<SymbolEntry> &)> ToRemove) {
llvm::erase_if(Symbols, ToRemove);
}
void Object::updateLoadCommandIndexes() {
static constexpr char TextSegmentName[] = "__TEXT";
// Update indices of special load commands
for (size_t Index = 0, Size = LoadCommands.size(); Index < Size; ++Index) {
LoadCommand &LC = LoadCommands[Index];
switch (LC.MachOLoadCommand.load_command_data.cmd) {
case MachO::LC_CODE_SIGNATURE:
CodeSignatureCommandIndex = Index;
break;
case MachO::LC_SEGMENT:
if (StringRef(LC.MachOLoadCommand.segment_command_data.segname) ==
TextSegmentName)
TextSegmentCommandIndex = Index;
break;
case MachO::LC_SEGMENT_64:
if (StringRef(LC.MachOLoadCommand.segment_command_64_data.segname) ==
TextSegmentName)
TextSegmentCommandIndex = Index;
break;
case MachO::LC_SYMTAB:
SymTabCommandIndex = Index;
break;
case MachO::LC_DYSYMTAB:
DySymTabCommandIndex = Index;
break;
case MachO::LC_DYLD_INFO:
case MachO::LC_DYLD_INFO_ONLY:
DyLdInfoCommandIndex = Index;
break;
case MachO::LC_DATA_IN_CODE:
DataInCodeCommandIndex = Index;
break;
case MachO::LC_LINKER_OPTIMIZATION_HINT:
LinkerOptimizationHintCommandIndex = Index;
break;
case MachO::LC_FUNCTION_STARTS:
FunctionStartsCommandIndex = Index;
break;
case MachO::LC_DYLIB_CODE_SIGN_DRS:
DylibCodeSignDRsIndex = Index;
break;
case MachO::LC_DYLD_CHAINED_FIXUPS:
ChainedFixupsCommandIndex = Index;
break;
case MachO::LC_DYLD_EXPORTS_TRIE:
ExportsTrieCommandIndex = Index;
break;
}
}
}
Error Object::removeLoadCommands(
function_ref<bool(const LoadCommand &)> ToRemove) {
auto It = std::stable_partition(
LoadCommands.begin(), LoadCommands.end(),
[&](const LoadCommand &LC) { return !ToRemove(LC); });
LoadCommands.erase(It, LoadCommands.end());
updateLoadCommandIndexes();
return Error::success();
}
Error Object::removeSections(
function_ref<bool(const std::unique_ptr<Section> &)> ToRemove) {
DenseMap<uint32_t, const Section *> OldIndexToSection;
uint32_t NextSectionIndex = 1;
for (LoadCommand &LC : LoadCommands) {
auto It = std::stable_partition(
std::begin(LC.Sections), std::end(LC.Sections),
[&](const std::unique_ptr<Section> &Sec) { return !ToRemove(Sec); });
for (auto I = LC.Sections.begin(), End = It; I != End; ++I) {
OldIndexToSection[(*I)->Index] = I->get();
(*I)->Index = NextSectionIndex++;
}
LC.Sections.erase(It, LC.Sections.end());
}
auto IsDead = [&](const std::unique_ptr<SymbolEntry> &S) -> bool {
std::optional<uint32_t> Section = S->section();
return (Section && !OldIndexToSection.count(*Section));
};
SmallPtrSet<const SymbolEntry *, 2> DeadSymbols;
for (const std::unique_ptr<SymbolEntry> &Sym : SymTable.Symbols)
if (IsDead(Sym))
DeadSymbols.insert(Sym.get());
for (const LoadCommand &LC : LoadCommands)
for (const std::unique_ptr<Section> &Sec : LC.Sections)
for (const RelocationInfo &R : Sec->Relocations)
if (R.Symbol && *R.Symbol && DeadSymbols.count(*R.Symbol))
return createStringError(std::errc::invalid_argument,
"symbol '%s' defined in section with index "
"'%u' cannot be removed because it is "
"referenced by a relocation in section '%s'",
(*R.Symbol)->Name.c_str(),
*((*R.Symbol)->section()),
Sec->CanonicalName.c_str());
SymTable.removeSymbols(IsDead);
for (std::unique_ptr<SymbolEntry> &S : SymTable.Symbols)
if (S->section())
S->n_sect = OldIndexToSection[S->n_sect]->Index;
return Error::success();
}
uint64_t Object::nextAvailableSegmentAddress() const {
uint64_t HeaderSize =
is64Bit() ? sizeof(MachO::mach_header_64) : sizeof(MachO::mach_header);
uint64_t Addr = HeaderSize + Header.SizeOfCmds;
for (const LoadCommand &LC : LoadCommands) {
const MachO::macho_load_command &MLC = LC.MachOLoadCommand;
switch (MLC.load_command_data.cmd) {
case MachO::LC_SEGMENT:
Addr = std::max(Addr,
static_cast<uint64_t>(MLC.segment_command_data.vmaddr) +
MLC.segment_command_data.vmsize);
break;
case MachO::LC_SEGMENT_64:
Addr = std::max(Addr, MLC.segment_command_64_data.vmaddr +
MLC.segment_command_64_data.vmsize);
break;
default:
continue;
}
}
return Addr;
}
template <typename SegmentType>
static void
constructSegment(SegmentType &Seg, llvm::MachO::LoadCommandType CmdType,
StringRef SegName, uint64_t SegVMAddr, uint64_t SegVMSize) {
assert(SegName.size() <= sizeof(Seg.segname) && "too long segment name");
memset(&Seg, 0, sizeof(SegmentType));
Seg.cmd = CmdType;
strncpy(Seg.segname, SegName.data(), SegName.size());
Seg.maxprot |=
(MachO::VM_PROT_READ | MachO::VM_PROT_WRITE | MachO::VM_PROT_EXECUTE);
Seg.initprot |=
(MachO::VM_PROT_READ | MachO::VM_PROT_WRITE | MachO::VM_PROT_EXECUTE);
Seg.vmaddr = SegVMAddr;
Seg.vmsize = SegVMSize;
}
LoadCommand &Object::addSegment(StringRef SegName, uint64_t SegVMSize) {
LoadCommand LC;
const uint64_t SegVMAddr = nextAvailableSegmentAddress();
if (is64Bit())
constructSegment(LC.MachOLoadCommand.segment_command_64_data,
MachO::LC_SEGMENT_64, SegName, SegVMAddr, SegVMSize);
else
constructSegment(LC.MachOLoadCommand.segment_command_data,
MachO::LC_SEGMENT, SegName, SegVMAddr, SegVMSize);
LoadCommands.push_back(std::move(LC));
return LoadCommands.back();
}
/// Extracts a segment name from a string which is possibly non-null-terminated.
static StringRef extractSegmentName(const char *SegName) {
return StringRef(SegName,
strnlen(SegName, sizeof(MachO::segment_command::segname)));
}
std::optional<StringRef> LoadCommand::getSegmentName() const {
const MachO::macho_load_command &MLC = MachOLoadCommand;
switch (MLC.load_command_data.cmd) {
case MachO::LC_SEGMENT:
return extractSegmentName(MLC.segment_command_data.segname);
case MachO::LC_SEGMENT_64:
return extractSegmentName(MLC.segment_command_64_data.segname);
default:
return std::nullopt;
}
}
std::optional<uint64_t> LoadCommand::getSegmentVMAddr() const {
const MachO::macho_load_command &MLC = MachOLoadCommand;
switch (MLC.load_command_data.cmd) {
case MachO::LC_SEGMENT:
return MLC.segment_command_data.vmaddr;
case MachO::LC_SEGMENT_64:
return MLC.segment_command_64_data.vmaddr;
default:
return std::nullopt;
}
}
|
