1 //===- ELFObjectReader.cpp ------------------------------------------------===//
2 //
3 // The MCLinker Project
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 #include <mcld/LD/ELFObjectReader.h>
10
11 #include <string>
12 #include <cassert>
13
14 #include <llvm/Support/ELF.h>
15 #include <llvm/ADT/Twine.h>
16
17 #include <mcld/IRBuilder.h>
18 #include <mcld/MC/MCLDInput.h>
19 #include <mcld/LD/ELFReader.h>
20 #include <mcld/LD/EhFrameReader.h>
21 #include <mcld/LD/EhFrame.h>
22 #include <mcld/Target/GNULDBackend.h>
23 #include <mcld/Support/MsgHandling.h>
24 #include <mcld/Object/ObjectBuilder.h>
25
26 using namespace mcld;
27
28 //===----------------------------------------------------------------------===//
29 // ELFObjectReader
30 //===----------------------------------------------------------------------===//
31 /// constructor
ELFObjectReader(GNULDBackend & pBackend,IRBuilder & pBuilder,const LinkerConfig & pConfig)32 ELFObjectReader::ELFObjectReader(GNULDBackend& pBackend,
33 IRBuilder& pBuilder,
34 const LinkerConfig& pConfig)
35 : ObjectReader(),
36 m_pELFReader(NULL),
37 m_pEhFrameReader(NULL),
38 m_Builder(pBuilder),
39 m_ReadFlag(ParseEhFrame),
40 m_Backend(pBackend),
41 m_Config(pConfig) {
42 if (pConfig.targets().is32Bits() && pConfig.targets().isLittleEndian()) {
43 m_pELFReader = new ELFReader<32, true>(pBackend);
44 }
45 else if (pConfig.targets().is64Bits() && pConfig.targets().isLittleEndian()) {
46 m_pELFReader = new ELFReader<64, true>(pBackend);
47 }
48
49 m_pEhFrameReader = new EhFrameReader();
50 }
51
52 /// destructor
~ELFObjectReader()53 ELFObjectReader::~ELFObjectReader()
54 {
55 delete m_pELFReader;
56 delete m_pEhFrameReader;
57 }
58
59 /// isMyFormat
isMyFormat(Input & pInput) const60 bool ELFObjectReader::isMyFormat(Input &pInput) const
61 {
62 assert(pInput.hasMemArea());
63
64 // Don't warning about the frequently requests.
65 // MemoryArea has a list of cache to handle this.
66 size_t hdr_size = m_pELFReader->getELFHeaderSize();
67 MemoryRegion* region = pInput.memArea()->request(pInput.fileOffset(),
68 hdr_size);
69
70 uint8_t* ELF_hdr = region->start();
71 bool result = true;
72 if (!m_pELFReader->isELF(ELF_hdr))
73 result = false;
74 else if (!m_pELFReader->isMyEndian(ELF_hdr))
75 result = false;
76 else if (!m_pELFReader->isMyMachine(ELF_hdr))
77 result = false;
78 else if (Input::Object != m_pELFReader->fileType(ELF_hdr))
79 result = false;
80 pInput.memArea()->release(region);
81 return result;
82 }
83
84 /// readHeader - read section header and create LDSections.
readHeader(Input & pInput)85 bool ELFObjectReader::readHeader(Input& pInput)
86 {
87 assert(pInput.hasMemArea());
88
89 size_t hdr_size = m_pELFReader->getELFHeaderSize();
90 MemoryRegion* region = pInput.memArea()->request(pInput.fileOffset(),
91 hdr_size);
92 uint8_t* ELF_hdr = region->start();
93 bool result = m_pELFReader->readSectionHeaders(pInput, ELF_hdr);
94 pInput.memArea()->release(region);
95 return result;
96 }
97
98 /// readSections - read all regular sections.
readSections(Input & pInput)99 bool ELFObjectReader::readSections(Input& pInput)
100 {
101 // handle sections
102 LDContext::sect_iterator section, sectEnd = pInput.context()->sectEnd();
103 for (section = pInput.context()->sectBegin(); section != sectEnd; ++section) {
104 // ignore the section if the LDSection* in input context is NULL
105 if (NULL == *section)
106 continue;
107
108 switch((*section)->kind()) {
109 /** group sections **/
110 case LDFileFormat::Group: {
111 assert(NULL != (*section)->getLink());
112 ResolveInfo* signature =
113 m_pELFReader->readSignature(pInput,
114 *(*section)->getLink(),
115 (*section)->getInfo());
116
117 bool exist = false;
118 if (0 == signature->nameSize() &&
119 ResolveInfo::Section == signature->type()) {
120 // if the signature is a section symbol in input object, we use the
121 // section name as group signature.
122 signatures().insert((*section)->name(), exist);
123 } else {
124 signatures().insert(signature->name(), exist);
125 }
126
127 if (exist) {
128 // if this is not the first time we see this group signature, then
129 // ignore all the members in this group (set Ignore)
130 MemoryRegion* region = pInput.memArea()->request(
131 pInput.fileOffset() + (*section)->offset(), (*section)->size());
132 llvm::ELF::Elf32_Word* value =
133 reinterpret_cast<llvm::ELF::Elf32_Word*>(region->start());
134
135 size_t size = region->size() / sizeof(llvm::ELF::Elf32_Word);
136 if (llvm::ELF::GRP_COMDAT == *value) {
137 for (size_t index = 1; index < size; ++index) {
138 pInput.context()->getSection(value[index])->setKind(LDFileFormat::Ignore);
139 }
140 }
141 pInput.memArea()->release(region);
142 }
143 ResolveInfo::Destroy(signature);
144 break;
145 }
146 /** relocation sections **/
147 case LDFileFormat::Relocation: {
148 assert(NULL != (*section)->getLink());
149 size_t link_index = (*section)->getLink()->index();
150 LDSection* link_sect = pInput.context()->getSection(link_index);
151 if (NULL == link_sect || LDFileFormat::Ignore == link_sect->kind()) {
152 // Relocation sections of group members should also be part of the
153 // group. Thus, if the associated member sections are ignored, the
154 // related relocations should be also ignored.
155 (*section)->setKind(LDFileFormat::Ignore);
156 }
157 break;
158 }
159 /** normal sections **/
160 // FIXME: support Version Kind
161 case LDFileFormat::Version:
162 // FIXME: support GCCExceptTable Kind
163 case LDFileFormat::GCCExceptTable:
164 /** Fall through **/
165 case LDFileFormat::Regular:
166 case LDFileFormat::Note:
167 case LDFileFormat::MetaData: {
168 SectionData* sd = IRBuilder::CreateSectionData(**section);
169 if (!m_pELFReader->readRegularSection(pInput, *sd))
170 fatal(diag::err_cannot_read_section) << (*section)->name();
171 break;
172 }
173 case LDFileFormat::Debug: {
174 if (m_Config.options().stripDebug()) {
175 (*section)->setKind(LDFileFormat::Ignore);
176 }
177 else {
178 SectionData* sd = IRBuilder::CreateSectionData(**section);
179 if (!m_pELFReader->readRegularSection(pInput, *sd)) {
180 fatal(diag::err_cannot_read_section) << (*section)->name();
181 }
182 }
183 break;
184 }
185 case LDFileFormat::EhFrame: {
186 EhFrame* eh_frame = IRBuilder::CreateEhFrame(**section);
187
188 if (m_Config.options().hasEhFrameHdr() &&
189 (m_ReadFlag & ParseEhFrame)) {
190
191 // if --eh-frame-hdr option is given, parse .eh_frame.
192 if (!m_pEhFrameReader->read<32, true>(pInput, *eh_frame)) {
193 // if we failed to parse a .eh_frame, we should not parse the rest
194 // .eh_frame.
195 m_ReadFlag ^= ParseEhFrame;
196 }
197 }
198 else {
199 if (!m_pELFReader->readRegularSection(pInput,
200 eh_frame->getSectionData())) {
201 fatal(diag::err_cannot_read_section) << (*section)->name();
202 }
203 }
204 break;
205 }
206 /** target dependent sections **/
207 case LDFileFormat::Target: {
208 SectionData* sd = IRBuilder::CreateSectionData(**section);
209 if (!m_Backend.readSection(pInput, *sd)) {
210 fatal(diag::err_cannot_read_target_section) << (*section)->name();
211 }
212 break;
213 }
214 /** BSS sections **/
215 case LDFileFormat::BSS: {
216 IRBuilder::CreateBSS(**section);
217 break;
218 }
219 // ignore
220 case LDFileFormat::Null:
221 case LDFileFormat::NamePool:
222 case LDFileFormat::Ignore:
223 case LDFileFormat::StackNote:
224 continue;
225 // warning
226 case LDFileFormat::EhFrameHdr:
227 default: {
228 warning(diag::warn_illegal_input_section) << (*section)->name()
229 << pInput.name()
230 << pInput.path();
231 break;
232 }
233 }
234 } // end of for all sections
235
236 return true;
237 }
238
239 /// readSymbols - read symbols from the input relocatable object.
readSymbols(Input & pInput)240 bool ELFObjectReader::readSymbols(Input& pInput)
241 {
242 assert(pInput.hasMemArea());
243
244 LDSection* symtab_shdr = pInput.context()->getSection(".symtab");
245 if (NULL == symtab_shdr) {
246 note(diag::note_has_no_symtab) << pInput.name()
247 << pInput.path()
248 << ".symtab";
249 return true;
250 }
251
252 LDSection* strtab_shdr = symtab_shdr->getLink();
253 if (NULL == strtab_shdr) {
254 fatal(diag::fatal_cannot_read_strtab) << pInput.name()
255 << pInput.path()
256 << ".symtab";
257 return false;
258 }
259
260 MemoryRegion* symtab_region = pInput.memArea()->request(
261 pInput.fileOffset() + symtab_shdr->offset(), symtab_shdr->size());
262 MemoryRegion* strtab_region = pInput.memArea()->request(
263 pInput.fileOffset() + strtab_shdr->offset(), strtab_shdr->size());
264 char* strtab = reinterpret_cast<char*>(strtab_region->start());
265 bool result = m_pELFReader->readSymbols(pInput,
266 m_Builder,
267 *symtab_region,
268 strtab);
269 pInput.memArea()->release(symtab_region);
270 pInput.memArea()->release(strtab_region);
271 return result;
272 }
273
readRelocations(Input & pInput)274 bool ELFObjectReader::readRelocations(Input& pInput)
275 {
276 assert(pInput.hasMemArea());
277
278 MemoryArea* mem = pInput.memArea();
279 LDContext::sect_iterator rs, rsEnd = pInput.context()->relocSectEnd();
280 for (rs = pInput.context()->relocSectBegin(); rs != rsEnd; ++rs) {
281 if (LDFileFormat::Ignore == (*rs)->kind())
282 continue;
283
284 uint32_t offset = pInput.fileOffset() + (*rs)->offset();
285 uint32_t size = (*rs)->size();
286 MemoryRegion* region = mem->request(offset, size);
287 IRBuilder::CreateRelocData(**rs); ///< create relocation data for the header
288 switch ((*rs)->type()) {
289 case llvm::ELF::SHT_RELA: {
290 if (!m_pELFReader->readRela(pInput, **rs, *region)) {
291 mem->release(region);
292 return false;
293 }
294 break;
295 }
296 case llvm::ELF::SHT_REL: {
297 if (!m_pELFReader->readRel(pInput, **rs, *region)) {
298 mem->release(region);
299 return false;
300 }
301 break;
302 }
303 default: { ///< should not enter
304 mem->release(region);
305 return false;
306 }
307 } // end of switch
308
309 mem->release(region);
310 } // end of for all relocation data
311
312 return true;
313 }
314
315