ELFObjectReader.cpp revision 87f34658dec9097d987d254a990ea7f311bfc95f 
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 <mcld/IRBuilder.h>
12#include <mcld/MC/Input.h>
13#include <mcld/LD/ELFReader.h>
14#include <mcld/LD/EhFrameReader.h>
15#include <mcld/LD/EhFrame.h>
16#include <mcld/Target/GNULDBackend.h>
17#include <mcld/Support/MsgHandling.h>
18#include <mcld/Support/MemoryArea.h>
19#include <mcld/Object/ObjectBuilder.h>
20
21#include <llvm/Support/ELF.h>
22#include <llvm/ADT/Twine.h>
23#include <llvm/ADT/StringRef.h>
24
25#include <string>
26#include <cassert>
27
28using namespace mcld;
29
30//===----------------------------------------------------------------------===//
31// ELFObjectReader
32//===----------------------------------------------------------------------===//
33/// constructor
34ELFObjectReader::ELFObjectReader(GNULDBackend& pBackend,
35                                 IRBuilder& pBuilder,
36                                 const LinkerConfig& pConfig)
37  : ObjectReader(),
38    m_pELFReader(NULL),
39    m_pEhFrameReader(NULL),
40    m_Builder(pBuilder),
41    m_ReadFlag(ParseEhFrame),
42    m_Backend(pBackend),
43    m_Config(pConfig) {
44  if (pConfig.targets().is32Bits() && pConfig.targets().isLittleEndian()) {
45    m_pELFReader = new ELFReader<32, true>(pBackend);
46  }
47  else if (pConfig.targets().is64Bits() && pConfig.targets().isLittleEndian()) {
48    m_pELFReader = new ELFReader<64, true>(pBackend);
49  }
50
51  m_pEhFrameReader = new EhFrameReader();
52}
53
54/// destructor
55ELFObjectReader::~ELFObjectReader()
56{
57  delete m_pELFReader;
58  delete m_pEhFrameReader;
59}
60
61/// isMyFormat
62bool ELFObjectReader::isMyFormat(Input &pInput, bool &pContinue) const
63{
64  assert(pInput.hasMemArea());
65
66  // Don't warning about the frequently requests.
67  // MemoryArea has a list of cache to handle this.
68  size_t hdr_size = m_pELFReader->getELFHeaderSize();
69  if (pInput.memArea()->size() < hdr_size)
70    return false;
71
72  llvm::StringRef region = pInput.memArea()->request(pInput.fileOffset(),
73                                                     hdr_size);
74
75  const char* ELF_hdr = region.begin();
76  bool result = true;
77  if (!m_pELFReader->isELF(ELF_hdr)) {
78    pContinue = true;
79    result = false;
80  } else if (Input::Object != m_pELFReader->fileType(ELF_hdr)) {
81    pContinue = true;
82    result = false;
83  } else if (!m_pELFReader->isMyEndian(ELF_hdr)) {
84    pContinue = false;
85    result = false;
86  } else if (!m_pELFReader->isMyMachine(ELF_hdr)) {
87    pContinue = false;
88    result = false;
89  }
90  return result;
91}
92
93/// readHeader - read section header and create LDSections.
94bool ELFObjectReader::readHeader(Input& pInput)
95{
96  assert(pInput.hasMemArea());
97
98  size_t hdr_size = m_pELFReader->getELFHeaderSize();
99  if (pInput.memArea()->size() < hdr_size)
100    return false;
101
102  llvm::StringRef region = pInput.memArea()->request(pInput.fileOffset(),
103                                                     hdr_size);
104  const char* ELF_hdr = region.begin();
105  bool result = m_pELFReader->readSectionHeaders(pInput, ELF_hdr);
106  return result;
107}
108
109/// readSections - read all regular sections.
110bool ELFObjectReader::readSections(Input& pInput)
111{
112  // handle sections
113  LDContext::sect_iterator section, sectEnd = pInput.context()->sectEnd();
114  for (section = pInput.context()->sectBegin(); section != sectEnd; ++section) {
115    // ignore the section if the LDSection* in input context is NULL
116    if (NULL == *section)
117        continue;
118
119    switch((*section)->kind()) {
120      /** group sections **/
121      case LDFileFormat::Group: {
122        assert(NULL != (*section)->getLink());
123        ResolveInfo* signature =
124            m_pELFReader->readSignature(pInput,
125                                        *(*section)->getLink(),
126                                        (*section)->getInfo());
127
128        bool exist = false;
129        if (0 == signature->nameSize() &&
130            ResolveInfo::Section == signature->type()) {
131          // if the signature is a section symbol in input object, we use the
132          // section name as group signature.
133          signatures().insert((*section)->name(), exist);
134        } else {
135          signatures().insert(signature->name(), exist);
136        }
137
138        if (exist) {
139          // if this is not the first time we see this group signature, then
140          // ignore all the members in this group (set Ignore)
141          llvm::StringRef region = pInput.memArea()->request(
142               pInput.fileOffset() + (*section)->offset(), (*section)->size());
143          const llvm::ELF::Elf32_Word* value =
144              reinterpret_cast<const llvm::ELF::Elf32_Word*>(region.begin());
145
146          size_t size = region.size() / sizeof(llvm::ELF::Elf32_Word);
147          if (llvm::ELF::GRP_COMDAT == *value) {
148            for (size_t index = 1; index < size; ++index) {
149              pInput.context()->getSection(value[index])->setKind(LDFileFormat::Ignore);
150            }
151          }
152        }
153        ResolveInfo::Destroy(signature);
154        break;
155      }
156      /** linkonce sections **/
157      case LDFileFormat::LinkOnce: {
158        bool exist = false;
159        // .gnu.linkonce + "." + type + "." + name
160        llvm::StringRef name(llvm::StringRef((*section)->name()).drop_front(14));
161        signatures().insert(name.split(".").second, exist);
162        if (!exist) {
163          if (name.startswith("wi")) {
164            (*section)->setKind(LDFileFormat::Debug);
165            if (m_Config.options().stripDebug())
166              (*section)->setKind(LDFileFormat::Ignore);
167            else {
168              SectionData* sd = IRBuilder::CreateSectionData(**section);
169              if (!m_pELFReader->readRegularSection(pInput, *sd))
170                fatal(diag::err_cannot_read_section) << (*section)->name();
171            }
172          } else {
173            (*section)->setKind(LDFileFormat::Regular);
174            SectionData* sd = IRBuilder::CreateSectionData(**section);
175            if (!m_pELFReader->readRegularSection(pInput, *sd))
176              fatal(diag::err_cannot_read_section) << (*section)->name();
177          }
178        } else {
179          (*section)->setKind(LDFileFormat::Ignore);
180        }
181        break;
182      }
183      /** relocation sections **/
184      case LDFileFormat::Relocation: {
185        assert(NULL != (*section)->getLink());
186        size_t link_index = (*section)->getLink()->index();
187        LDSection* link_sect = pInput.context()->getSection(link_index);
188        if (NULL == link_sect || LDFileFormat::Ignore == link_sect->kind()) {
189          // Relocation sections of group members should also be part of the
190          // group. Thus, if the associated member sections are ignored, the
191          // related relocations should be also ignored.
192          (*section)->setKind(LDFileFormat::Ignore);
193        }
194        break;
195      }
196      /** normal sections **/
197      // FIXME: support Version Kind
198      case LDFileFormat::Version:
199      // FIXME: support GCCExceptTable Kind
200      case LDFileFormat::GCCExceptTable:
201      /** Fall through **/
202      case LDFileFormat::Regular:
203      case LDFileFormat::Note:
204      case LDFileFormat::MetaData: {
205        SectionData* sd = IRBuilder::CreateSectionData(**section);
206        if (!m_pELFReader->readRegularSection(pInput, *sd))
207          fatal(diag::err_cannot_read_section) << (*section)->name();
208        break;
209      }
210      case LDFileFormat::Debug: {
211        if (m_Config.options().stripDebug()) {
212          (*section)->setKind(LDFileFormat::Ignore);
213        }
214        else {
215          SectionData* sd = IRBuilder::CreateSectionData(**section);
216          if (!m_pELFReader->readRegularSection(pInput, *sd)) {
217            fatal(diag::err_cannot_read_section) << (*section)->name();
218          }
219        }
220        break;
221      }
222      case LDFileFormat::EhFrame: {
223        EhFrame* eh_frame = IRBuilder::CreateEhFrame(**section);
224
225        // We don't really parse EhFrame if this is a partial linking
226        if ((m_Config.codeGenType() != LinkerConfig::Object) &&
227            (m_ReadFlag & ParseEhFrame)) {
228          if (!m_pEhFrameReader->read<32, true>(pInput, *eh_frame)) {
229            // if we failed to parse a .eh_frame, we should not parse the rest
230            // .eh_frame.
231            m_ReadFlag ^= ParseEhFrame;
232          }
233        }
234        else {
235          if (!m_pELFReader->readRegularSection(pInput,
236                                                *eh_frame->getSectionData())) {
237            fatal(diag::err_cannot_read_section) << (*section)->name();
238          }
239        }
240        break;
241      }
242      /** target dependent sections **/
243      case LDFileFormat::Target: {
244        SectionData* sd = IRBuilder::CreateSectionData(**section);
245        if (!m_Backend.readSection(pInput, *sd)) {
246          fatal(diag::err_cannot_read_target_section) << (*section)->name();
247        }
248        break;
249      }
250      /** BSS sections **/
251      case LDFileFormat::BSS: {
252        IRBuilder::CreateBSS(**section);
253        break;
254      }
255      // ignore
256      case LDFileFormat::Null:
257      case LDFileFormat::NamePool:
258      case LDFileFormat::Ignore:
259      case LDFileFormat::StackNote:
260        continue;
261      // warning
262      case LDFileFormat::EhFrameHdr:
263      default: {
264        warning(diag::warn_illegal_input_section) << (*section)->name()
265                                                  << pInput.name()
266                                                  << pInput.path();
267        break;
268      }
269    }
270  } // end of for all sections
271
272  return true;
273}
274
275/// readSymbols - read symbols from the input relocatable object.
276bool ELFObjectReader::readSymbols(Input& pInput)
277{
278  assert(pInput.hasMemArea());
279
280  LDSection* symtab_shdr = pInput.context()->getSection(".symtab");
281  if (NULL == symtab_shdr) {
282    note(diag::note_has_no_symtab) << pInput.name()
283                                   << pInput.path()
284                                   << ".symtab";
285    return true;
286  }
287
288  LDSection* strtab_shdr = symtab_shdr->getLink();
289  if (NULL == strtab_shdr) {
290    fatal(diag::fatal_cannot_read_strtab) << pInput.name()
291                                          << pInput.path()
292                                          << ".symtab";
293    return false;
294  }
295
296  llvm::StringRef symtab_region = pInput.memArea()->request(
297      pInput.fileOffset() + symtab_shdr->offset(), symtab_shdr->size());
298  llvm::StringRef strtab_region = pInput.memArea()->request(
299      pInput.fileOffset() + strtab_shdr->offset(), strtab_shdr->size());
300  const char* strtab = strtab_region.begin();
301  bool result = m_pELFReader->readSymbols(pInput,
302                                          m_Builder,
303                                          symtab_region,
304                                          strtab);
305  return result;
306}
307
308bool ELFObjectReader::readRelocations(Input& pInput)
309{
310  assert(pInput.hasMemArea());
311
312  MemoryArea* mem = pInput.memArea();
313  LDContext::sect_iterator rs, rsEnd = pInput.context()->relocSectEnd();
314  for (rs = pInput.context()->relocSectBegin(); rs != rsEnd; ++rs) {
315    if (LDFileFormat::Ignore == (*rs)->kind())
316      continue;
317
318    uint32_t offset = pInput.fileOffset() + (*rs)->offset();
319    uint32_t size = (*rs)->size();
320    llvm::StringRef region = mem->request(offset, size);
321    IRBuilder::CreateRelocData(**rs); ///< create relocation data for the header
322    switch ((*rs)->type()) {
323      case llvm::ELF::SHT_RELA: {
324        if (!m_pELFReader->readRela(pInput, **rs, region)) {
325          return false;
326        }
327        break;
328      }
329      case llvm::ELF::SHT_REL: {
330        if (!m_pELFReader->readRel(pInput, **rs, region)) {
331          return false;
332        }
333        break;
334      }
335      default: { ///< should not enter
336        return false;
337      }
338    } // end of switch
339
340  } // end of for all relocation data
341
342  return true;
343}
344
345