1 //===- OutputSections.cpp -------------------------------------------------===//
2 //
3 // The LLVM Linker
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9
10 #include "OutputSections.h"
11 #include "InputChunks.h"
12 #include "InputFiles.h"
13 #include "OutputSegment.h"
14 #include "WriterUtils.h"
15 #include "lld/Common/ErrorHandler.h"
16 #include "lld/Common/Threads.h"
17 #include "llvm/ADT/Twine.h"
18 #include "llvm/Support/LEB128.h"
19
20 #define DEBUG_TYPE "lld"
21
22 using namespace llvm;
23 using namespace llvm::wasm;
24 using namespace lld;
25 using namespace lld::wasm;
26
sectionTypeToString(uint32_t SectionType)27 static StringRef sectionTypeToString(uint32_t SectionType) {
28 switch (SectionType) {
29 case WASM_SEC_CUSTOM:
30 return "CUSTOM";
31 case WASM_SEC_TYPE:
32 return "TYPE";
33 case WASM_SEC_IMPORT:
34 return "IMPORT";
35 case WASM_SEC_FUNCTION:
36 return "FUNCTION";
37 case WASM_SEC_TABLE:
38 return "TABLE";
39 case WASM_SEC_MEMORY:
40 return "MEMORY";
41 case WASM_SEC_GLOBAL:
42 return "GLOBAL";
43 case WASM_SEC_EXPORT:
44 return "EXPORT";
45 case WASM_SEC_START:
46 return "START";
47 case WASM_SEC_ELEM:
48 return "ELEM";
49 case WASM_SEC_CODE:
50 return "CODE";
51 case WASM_SEC_DATA:
52 return "DATA";
53 default:
54 fatal("invalid section type");
55 }
56 }
57
58 // Returns a string, e.g. "FUNCTION(.text)".
toString(const OutputSection & Sec)59 std::string lld::toString(const OutputSection &Sec) {
60 if (!Sec.Name.empty())
61 return (Sec.getSectionName() + "(" + Sec.Name + ")").str();
62 return Sec.getSectionName();
63 }
64
getSectionName() const65 StringRef OutputSection::getSectionName() const {
66 return sectionTypeToString(Type);
67 }
68
createHeader(size_t BodySize)69 void OutputSection::createHeader(size_t BodySize) {
70 raw_string_ostream OS(Header);
71 debugWrite(OS.tell(), "section type [" + getSectionName() + "]");
72 encodeULEB128(Type, OS);
73 writeUleb128(OS, BodySize, "section size");
74 OS.flush();
75 log("createHeader: " + toString(*this) + " body=" + Twine(BodySize) +
76 " total=" + Twine(getSize()));
77 }
78
CodeSection(ArrayRef<InputFunction * > Functions)79 CodeSection::CodeSection(ArrayRef<InputFunction *> Functions)
80 : OutputSection(WASM_SEC_CODE), Functions(Functions) {
81 assert(Functions.size() > 0);
82
83 raw_string_ostream OS(CodeSectionHeader);
84 writeUleb128(OS, Functions.size(), "function count");
85 OS.flush();
86 BodySize = CodeSectionHeader.size();
87
88 for (InputFunction *Func : Functions) {
89 Func->OutputOffset = BodySize;
90 Func->calculateSize();
91 BodySize += Func->getSize();
92 }
93
94 createHeader(BodySize);
95 }
96
writeTo(uint8_t * Buf)97 void CodeSection::writeTo(uint8_t *Buf) {
98 log("writing " + toString(*this));
99 log(" size=" + Twine(getSize()));
100 log(" headersize=" + Twine(Header.size()));
101 log(" codeheadersize=" + Twine(CodeSectionHeader.size()));
102 Buf += Offset;
103
104 // Write section header
105 memcpy(Buf, Header.data(), Header.size());
106 Buf += Header.size();
107
108 // Write code section headers
109 memcpy(Buf, CodeSectionHeader.data(), CodeSectionHeader.size());
110
111 // Write code section bodies
112 parallelForEach(Functions,
113 [&](const InputChunk *Chunk) { Chunk->writeTo(Buf); });
114 }
115
numRelocations() const116 uint32_t CodeSection::numRelocations() const {
117 uint32_t Count = 0;
118 for (const InputChunk *Func : Functions)
119 Count += Func->NumRelocations();
120 return Count;
121 }
122
writeRelocations(raw_ostream & OS) const123 void CodeSection::writeRelocations(raw_ostream &OS) const {
124 for (const InputChunk *C : Functions)
125 C->writeRelocations(OS);
126 }
127
DataSection(ArrayRef<OutputSegment * > Segments)128 DataSection::DataSection(ArrayRef<OutputSegment *> Segments)
129 : OutputSection(WASM_SEC_DATA), Segments(Segments) {
130 raw_string_ostream OS(DataSectionHeader);
131
132 writeUleb128(OS, Segments.size(), "data segment count");
133 OS.flush();
134 BodySize = DataSectionHeader.size();
135
136 for (OutputSegment *Segment : Segments) {
137 raw_string_ostream OS(Segment->Header);
138 writeUleb128(OS, 0, "memory index");
139 writeUleb128(OS, WASM_OPCODE_I32_CONST, "opcode:i32const");
140 writeSleb128(OS, Segment->StartVA, "memory offset");
141 writeUleb128(OS, WASM_OPCODE_END, "opcode:end");
142 writeUleb128(OS, Segment->Size, "segment size");
143 OS.flush();
144
145 Segment->SectionOffset = BodySize;
146 BodySize += Segment->Header.size() + Segment->Size;
147 log("Data segment: size=" + Twine(Segment->Size));
148
149 for (InputSegment *InputSeg : Segment->InputSegments)
150 InputSeg->OutputOffset = Segment->SectionOffset + Segment->Header.size() +
151 InputSeg->OutputSegmentOffset;
152 }
153
154 createHeader(BodySize);
155 }
156
writeTo(uint8_t * Buf)157 void DataSection::writeTo(uint8_t *Buf) {
158 log("writing " + toString(*this) + " size=" + Twine(getSize()) +
159 " body=" + Twine(BodySize));
160 Buf += Offset;
161
162 // Write section header
163 memcpy(Buf, Header.data(), Header.size());
164 Buf += Header.size();
165
166 // Write data section headers
167 memcpy(Buf, DataSectionHeader.data(), DataSectionHeader.size());
168
169 parallelForEach(Segments, [&](const OutputSegment *Segment) {
170 // Write data segment header
171 uint8_t *SegStart = Buf + Segment->SectionOffset;
172 memcpy(SegStart, Segment->Header.data(), Segment->Header.size());
173
174 // Write segment data payload
175 for (const InputChunk *Chunk : Segment->InputSegments)
176 Chunk->writeTo(Buf);
177 });
178 }
179
numRelocations() const180 uint32_t DataSection::numRelocations() const {
181 uint32_t Count = 0;
182 for (const OutputSegment *Seg : Segments)
183 for (const InputChunk *InputSeg : Seg->InputSegments)
184 Count += InputSeg->NumRelocations();
185 return Count;
186 }
187
writeRelocations(raw_ostream & OS) const188 void DataSection::writeRelocations(raw_ostream &OS) const {
189 for (const OutputSegment *Seg : Segments)
190 for (const InputChunk *C : Seg->InputSegments)
191 C->writeRelocations(OS);
192 }
193
CustomSection(std::string Name,ArrayRef<InputSection * > InputSections)194 CustomSection::CustomSection(std::string Name,
195 ArrayRef<InputSection *> InputSections)
196 : OutputSection(WASM_SEC_CUSTOM, Name), PayloadSize(0),
197 InputSections(InputSections) {
198 raw_string_ostream OS(NameData);
199 encodeULEB128(Name.size(), OS);
200 OS << Name;
201 OS.flush();
202
203 for (InputSection *Section : InputSections) {
204 Section->OutputOffset = PayloadSize;
205 PayloadSize += Section->getSize();
206 }
207
208 createHeader(PayloadSize + NameData.size());
209 }
210
writeTo(uint8_t * Buf)211 void CustomSection::writeTo(uint8_t *Buf) {
212 log("writing " + toString(*this) + " size=" + Twine(getSize()) +
213 " chunks=" + Twine(InputSections.size()));
214
215 assert(Offset);
216 Buf += Offset;
217
218 // Write section header
219 memcpy(Buf, Header.data(), Header.size());
220 Buf += Header.size();
221 memcpy(Buf, NameData.data(), NameData.size());
222 Buf += NameData.size();
223
224 // Write custom sections payload
225 parallelForEach(InputSections,
226 [&](const InputSection *Section) { Section->writeTo(Buf); });
227 }
228
numRelocations() const229 uint32_t CustomSection::numRelocations() const {
230 uint32_t Count = 0;
231 for (const InputSection *InputSect : InputSections)
232 Count += InputSect->NumRelocations();
233 return Count;
234 }
235
writeRelocations(raw_ostream & OS) const236 void CustomSection::writeRelocations(raw_ostream &OS) const {
237 for (const InputSection *S : InputSections)
238 S->writeRelocations(OS);
239 }
240