MipsELFObjectWriter.cpp revision 101771ba4d9c2421f836069fcedf9ddc8a0c9dc7 
1//===-- MipsELFObjectWriter.cpp - Mips ELF Writer -------------------------===//
2//
3//                     The LLVM Compiler Infrastructure
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 "MCTargetDesc/MipsBaseInfo.h"
11#include "MCTargetDesc/MipsFixupKinds.h"
12#include "MCTargetDesc/MipsMCTargetDesc.h"
13#include "llvm/MC/MCAssembler.h"
14#include "llvm/MC/MCELFObjectWriter.h"
15#include "llvm/MC/MCExpr.h"
16#include "llvm/MC/MCSection.h"
17#include "llvm/MC/MCValue.h"
18#include "llvm/Support/ErrorHandling.h"
19#include <list>
20
21using namespace llvm;
22
23namespace {
24  struct RelEntry {
25    RelEntry(const ELFRelocationEntry &R, const MCSymbol *S, int64_t O) :
26      Reloc(R), Sym(S), Offset(O) {}
27    ELFRelocationEntry Reloc;
28    const MCSymbol *Sym;
29    int64_t Offset;
30  };
31
32  typedef std::list<RelEntry> RelLs;
33  typedef RelLs::iterator RelLsIter;
34
35  class MipsELFObjectWriter : public MCELFObjectTargetWriter {
36  public:
37    MipsELFObjectWriter(bool _is64Bit, uint8_t OSABI,
38                        bool _isN64, bool IsLittleEndian);
39
40    virtual ~MipsELFObjectWriter();
41
42    virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
43                                  bool IsPCRel, bool IsRelocWithSymbol,
44                                  int64_t Addend) const;
45    virtual unsigned getEFlags() const;
46    virtual const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
47                                           const MCValue &Target,
48                                           const MCFragment &F,
49                                           const MCFixup &Fixup,
50                                           bool IsPCRel) const;
51    virtual void sortRelocs(const MCAssembler &Asm,
52                            std::vector<ELFRelocationEntry> &Relocs);
53  };
54}
55
56MipsELFObjectWriter::MipsELFObjectWriter(bool _is64Bit, uint8_t OSABI,
57                                         bool _isN64, bool IsLittleEndian)
58  : MCELFObjectTargetWriter(_is64Bit, OSABI, ELF::EM_MIPS,
59                            /*HasRelocationAddend*/ (_isN64) ? true : false,
60                            /*IsN64*/ _isN64) {}
61
62MipsELFObjectWriter::~MipsELFObjectWriter() {}
63
64// FIXME: get the real EABI Version from the Subtarget class.
65unsigned MipsELFObjectWriter::getEFlags() const {
66
67  // FIXME: We can't tell if we are PIC (dynamic) or CPIC (static)
68  unsigned Flag = ELF::EF_MIPS_NOREORDER;
69
70  if (is64Bit())
71    Flag |= ELF::EF_MIPS_ARCH_64R2;
72  else
73    Flag |= ELF::EF_MIPS_ARCH_32R2;
74  return Flag;
75}
76
77const MCSymbol *MipsELFObjectWriter::ExplicitRelSym(const MCAssembler &Asm,
78                                                    const MCValue &Target,
79                                                    const MCFragment &F,
80                                                    const MCFixup &Fixup,
81                                                    bool IsPCRel) const {
82  assert(Target.getSymA() && "SymA cannot be 0.");
83  const MCSymbol &Sym = Target.getSymA()->getSymbol().AliasedSymbol();
84
85  if (Sym.getSection().getKind().isMergeableCString() ||
86      Sym.getSection().getKind().isMergeableConst())
87    return &Sym;
88
89  return NULL;
90}
91
92unsigned MipsELFObjectWriter::GetRelocType(const MCValue &Target,
93                                           const MCFixup &Fixup,
94                                           bool IsPCRel,
95                                           bool IsRelocWithSymbol,
96                                           int64_t Addend) const {
97  // determine the type of the relocation
98  unsigned Type = (unsigned)ELF::R_MIPS_NONE;
99  unsigned Kind = (unsigned)Fixup.getKind();
100
101  switch (Kind) {
102  default:
103    llvm_unreachable("invalid fixup kind!");
104  case FK_Data_4:
105    Type = ELF::R_MIPS_32;
106    break;
107  case FK_Data_8:
108    Type = ELF::R_MIPS_64;
109    break;
110  case FK_GPRel_4:
111    Type = ELF::R_MIPS_GPREL32;
112    break;
113  case Mips::fixup_Mips_GPREL16:
114    Type = ELF::R_MIPS_GPREL16;
115    break;
116  case Mips::fixup_Mips_26:
117    Type = ELF::R_MIPS_26;
118    break;
119  case Mips::fixup_Mips_CALL16:
120    Type = ELF::R_MIPS_CALL16;
121    break;
122  case Mips::fixup_Mips_GOT_Global:
123  case Mips::fixup_Mips_GOT_Local:
124    Type = ELF::R_MIPS_GOT16;
125    break;
126  case Mips::fixup_Mips_HI16:
127    Type = ELF::R_MIPS_HI16;
128    break;
129  case Mips::fixup_Mips_LO16:
130    Type = ELF::R_MIPS_LO16;
131    break;
132  case Mips::fixup_Mips_TLSGD:
133    Type = ELF::R_MIPS_TLS_GD;
134    break;
135  case Mips::fixup_Mips_GOTTPREL:
136    Type = ELF::R_MIPS_TLS_GOTTPREL;
137    break;
138  case Mips::fixup_Mips_TPREL_HI:
139    Type = ELF::R_MIPS_TLS_TPREL_HI16;
140    break;
141  case Mips::fixup_Mips_TPREL_LO:
142    Type = ELF::R_MIPS_TLS_TPREL_LO16;
143    break;
144  case Mips::fixup_Mips_TLSLDM:
145    Type = ELF::R_MIPS_TLS_LDM;
146    break;
147  case Mips::fixup_Mips_DTPREL_HI:
148    Type = ELF::R_MIPS_TLS_DTPREL_HI16;
149    break;
150  case Mips::fixup_Mips_DTPREL_LO:
151    Type = ELF::R_MIPS_TLS_DTPREL_LO16;
152    break;
153  case Mips::fixup_Mips_Branch_PCRel:
154  case Mips::fixup_Mips_PC16:
155    Type = ELF::R_MIPS_PC16;
156    break;
157  case Mips::fixup_Mips_GOT_PAGE:
158    Type = ELF::R_MIPS_GOT_PAGE;
159    break;
160  case Mips::fixup_Mips_GOT_OFST:
161    Type = ELF::R_MIPS_GOT_OFST;
162    break;
163  case Mips::fixup_Mips_GOT_DISP:
164    Type = ELF::R_MIPS_GOT_DISP;
165    break;
166  case Mips::fixup_Mips_GPOFF_HI:
167    Type = setRType((unsigned)ELF::R_MIPS_GPREL16, Type);
168    Type = setRType2((unsigned)ELF::R_MIPS_SUB, Type);
169    Type = setRType3((unsigned)ELF::R_MIPS_HI16, Type);
170    break;
171  case Mips::fixup_Mips_GPOFF_LO:
172    Type = setRType((unsigned)ELF::R_MIPS_GPREL16, Type);
173    Type = setRType2((unsigned)ELF::R_MIPS_SUB, Type);
174    Type = setRType3((unsigned)ELF::R_MIPS_LO16, Type);
175    break;
176  case Mips::fixup_Mips_HIGHER:
177    Type = ELF::R_MIPS_HIGHER;
178    break;
179  case Mips::fixup_Mips_HIGHEST:
180    Type = ELF::R_MIPS_HIGHEST;
181    break;
182  }
183  return Type;
184}
185
186// Return true if R is either a GOT16 against a local symbol or HI16.
187static bool NeedsMatchingLo(const MCAssembler &Asm, const RelEntry &R) {
188  if (!R.Sym)
189    return false;
190
191  MCSymbolData &SD = Asm.getSymbolData(R.Sym->AliasedSymbol());
192
193  return ((R.Reloc.Type == ELF::R_MIPS_GOT16) && !SD.isExternal()) ||
194    (R.Reloc.Type == ELF::R_MIPS_HI16);
195}
196
197static bool HasMatchingLo(const MCAssembler &Asm, RelLsIter I, RelLsIter Last) {
198  if (I == Last)
199    return false;
200
201  RelLsIter Hi = I++;
202
203  return (I->Reloc.Type == ELF::R_MIPS_LO16) && (Hi->Sym == I->Sym) &&
204    (Hi->Offset == I->Offset);
205}
206
207static bool HasSameSymbol(const RelEntry &R0, const RelEntry &R1) {
208  return R0.Sym == R1.Sym;
209}
210
211static int CompareOffset(const RelEntry &R0, const RelEntry &R1) {
212  return (R0.Offset > R1.Offset) ? 1 : ((R0.Offset == R1.Offset) ? 0 : -1);
213}
214
215void MipsELFObjectWriter::sortRelocs(const MCAssembler &Asm,
216                                     std::vector<ELFRelocationEntry> &Relocs) {
217  // Call the default function first. Relocations are sorted in descending
218  // order of r_offset.
219  MCELFObjectTargetWriter::sortRelocs(Asm, Relocs);
220
221  RelLs RelocLs;
222  std::vector<RelLsIter> Unmatched;
223
224  // Fill RelocLs. Traverse Relocs backwards so that relocations in RelocLs
225  // are in ascending order of r_offset.
226  for (std::vector<ELFRelocationEntry>::reverse_iterator R = Relocs.rbegin();
227       R != Relocs.rend(); ++R) {
228     std::pair<const MCSymbolRefExpr*, int64_t> P =
229       MipsGetSymAndOffset(*R->Fixup);
230     RelocLs.push_back(RelEntry(*R, P.first ? &P.first->getSymbol() : 0,
231                                P.second));
232  }
233
234  // Get list of unmatched HI16 and GOT16.
235  for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R)
236    if (NeedsMatchingLo(Asm, *R) && !HasMatchingLo(Asm, R, --RelocLs.end()))
237      Unmatched.push_back(R);
238
239  // Insert unmatched HI16 and GOT16 immediately before their matching LO16.
240  for (std::vector<RelLsIter>::iterator U = Unmatched.begin();
241       U != Unmatched.end(); ++U) {
242    RelLsIter LoPos = RelocLs.end(), HiPos = *U;
243    bool MatchedLo = false;
244
245    for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R) {
246      if ((R->Reloc.Type == ELF::R_MIPS_LO16) && HasSameSymbol(*HiPos, *R) &&
247          (CompareOffset(*R, *HiPos) >= 0) &&
248          ((LoPos == RelocLs.end()) || ((CompareOffset(*R, *LoPos) < 0)) ||
249           (!MatchedLo && !CompareOffset(*R, *LoPos))))
250        LoPos = R;
251
252      MatchedLo = NeedsMatchingLo(Asm, *R) &&
253        HasMatchingLo(Asm, R, --RelocLs.end());
254    }
255
256    // If a matching LoPos was found, move HiPos and insert it before LoPos.
257    // Make the offsets of HiPos and LoPos match.
258    if (LoPos != RelocLs.end()) {
259      HiPos->Offset = LoPos->Offset;
260      RelocLs.insert(LoPos, *HiPos);
261      RelocLs.erase(HiPos);
262    }
263  }
264
265  // Put the sorted list back in reverse order.
266  assert(Relocs.size() == RelocLs.size());
267  unsigned I = RelocLs.size();
268
269  for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R)
270    Relocs[--I] = R->Reloc;
271}
272
273MCObjectWriter *llvm::createMipsELFObjectWriter(raw_ostream &OS,
274                                                uint8_t OSABI,
275                                                bool IsLittleEndian,
276                                                bool Is64Bit) {
277  MCELFObjectTargetWriter *MOTW = new MipsELFObjectWriter(Is64Bit, OSABI,
278                                                (Is64Bit) ? true : false,
279                                                IsLittleEndian);
280  return createELFObjectWriter(MOTW, OS, IsLittleEndian);
281}
282