MipsELFObjectWriter.cpp revision 263508 
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 const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
46                                           const MCValue &Target,
47                                           const MCFragment &F,
48                                           const MCFixup &Fixup,
49                                           bool IsPCRel) const;
50    virtual void sortRelocs(const MCAssembler &Asm,
51                            std::vector<ELFRelocationEntry> &Relocs);
52  };
53}
54
55MipsELFObjectWriter::MipsELFObjectWriter(bool _is64Bit, uint8_t OSABI,
56                                         bool _isN64, bool IsLittleEndian)
57  : MCELFObjectTargetWriter(_is64Bit, OSABI, ELF::EM_MIPS,
58                            /*HasRelocationAddend*/ (_isN64) ? true : false,
59                            /*IsN64*/ _isN64) {}
60
61MipsELFObjectWriter::~MipsELFObjectWriter() {}
62
63const MCSymbol *MipsELFObjectWriter::ExplicitRelSym(const MCAssembler &Asm,
64                                                    const MCValue &Target,
65                                                    const MCFragment &F,
66                                                    const MCFixup &Fixup,
67                                                    bool IsPCRel) const {
68  assert(Target.getSymA() && "SymA cannot be 0.");
69  const MCSymbol &Sym = Target.getSymA()->getSymbol().AliasedSymbol();
70
71  if (Sym.getSection().getKind().isMergeableCString() ||
72      Sym.getSection().getKind().isMergeableConst())
73    return &Sym;
74
75  return NULL;
76}
77
78unsigned MipsELFObjectWriter::GetRelocType(const MCValue &Target,
79                                           const MCFixup &Fixup,
80                                           bool IsPCRel,
81                                           bool IsRelocWithSymbol,
82                                           int64_t Addend) const {
83  // determine the type of the relocation
84  unsigned Type = (unsigned)ELF::R_MIPS_NONE;
85  unsigned Kind = (unsigned)Fixup.getKind();
86
87  switch (Kind) {
88  default:
89    llvm_unreachable("invalid fixup kind!");
90  case FK_Data_4:
91    Type = ELF::R_MIPS_32;
92    break;
93  case FK_Data_8:
94    Type = ELF::R_MIPS_64;
95    break;
96  case FK_GPRel_4:
97    if (isN64()) {
98      Type = setRType((unsigned)ELF::R_MIPS_GPREL32, Type);
99      Type = setRType2((unsigned)ELF::R_MIPS_64, Type);
100      Type = setRType3((unsigned)ELF::R_MIPS_NONE, Type);
101    }
102    else
103      Type = ELF::R_MIPS_GPREL32;
104    break;
105  case Mips::fixup_Mips_GPREL16:
106    Type = ELF::R_MIPS_GPREL16;
107    break;
108  case Mips::fixup_Mips_26:
109    Type = ELF::R_MIPS_26;
110    break;
111  case Mips::fixup_Mips_CALL16:
112    Type = ELF::R_MIPS_CALL16;
113    break;
114  case Mips::fixup_Mips_GOT_Global:
115  case Mips::fixup_Mips_GOT_Local:
116    Type = ELF::R_MIPS_GOT16;
117    break;
118  case Mips::fixup_Mips_HI16:
119    Type = ELF::R_MIPS_HI16;
120    break;
121  case Mips::fixup_Mips_LO16:
122    Type = ELF::R_MIPS_LO16;
123    break;
124  case Mips::fixup_Mips_TLSGD:
125    Type = ELF::R_MIPS_TLS_GD;
126    break;
127  case Mips::fixup_Mips_GOTTPREL:
128    Type = ELF::R_MIPS_TLS_GOTTPREL;
129    break;
130  case Mips::fixup_Mips_TPREL_HI:
131    Type = ELF::R_MIPS_TLS_TPREL_HI16;
132    break;
133  case Mips::fixup_Mips_TPREL_LO:
134    Type = ELF::R_MIPS_TLS_TPREL_LO16;
135    break;
136  case Mips::fixup_Mips_TLSLDM:
137    Type = ELF::R_MIPS_TLS_LDM;
138    break;
139  case Mips::fixup_Mips_DTPREL_HI:
140    Type = ELF::R_MIPS_TLS_DTPREL_HI16;
141    break;
142  case Mips::fixup_Mips_DTPREL_LO:
143    Type = ELF::R_MIPS_TLS_DTPREL_LO16;
144    break;
145  case Mips::fixup_Mips_Branch_PCRel:
146  case Mips::fixup_Mips_PC16:
147    Type = ELF::R_MIPS_PC16;
148    break;
149  case Mips::fixup_Mips_GOT_PAGE:
150    Type = ELF::R_MIPS_GOT_PAGE;
151    break;
152  case Mips::fixup_Mips_GOT_OFST:
153    Type = ELF::R_MIPS_GOT_OFST;
154    break;
155  case Mips::fixup_Mips_GOT_DISP:
156    Type = ELF::R_MIPS_GOT_DISP;
157    break;
158  case Mips::fixup_Mips_GPOFF_HI:
159    Type = setRType((unsigned)ELF::R_MIPS_GPREL16, Type);
160    Type = setRType2((unsigned)ELF::R_MIPS_SUB, Type);
161    Type = setRType3((unsigned)ELF::R_MIPS_HI16, Type);
162    break;
163  case Mips::fixup_Mips_GPOFF_LO:
164    Type = setRType((unsigned)ELF::R_MIPS_GPREL16, Type);
165    Type = setRType2((unsigned)ELF::R_MIPS_SUB, Type);
166    Type = setRType3((unsigned)ELF::R_MIPS_LO16, Type);
167    break;
168  case Mips::fixup_Mips_HIGHER:
169    Type = ELF::R_MIPS_HIGHER;
170    break;
171  case Mips::fixup_Mips_HIGHEST:
172    Type = ELF::R_MIPS_HIGHEST;
173    break;
174  case Mips::fixup_Mips_GOT_HI16:
175    Type = ELF::R_MIPS_GOT_HI16;
176    break;
177  case Mips::fixup_Mips_GOT_LO16:
178    Type = ELF::R_MIPS_GOT_LO16;
179    break;
180  case Mips::fixup_Mips_CALL_HI16:
181    Type = ELF::R_MIPS_CALL_HI16;
182    break;
183  case Mips::fixup_Mips_CALL_LO16:
184    Type = ELF::R_MIPS_CALL_LO16;
185    break;
186  case Mips::fixup_MICROMIPS_26_S1:
187    Type = ELF::R_MICROMIPS_26_S1;
188    break;
189  case Mips::fixup_MICROMIPS_HI16:
190    Type = ELF::R_MICROMIPS_HI16;
191    break;
192  case Mips::fixup_MICROMIPS_LO16:
193    Type = ELF::R_MICROMIPS_LO16;
194    break;
195  case Mips::fixup_MICROMIPS_GOT16:
196    Type = ELF::R_MICROMIPS_GOT16;
197    break;
198  case Mips::fixup_MICROMIPS_PC16_S1:
199    Type = ELF::R_MICROMIPS_PC16_S1;
200    break;
201  case Mips::fixup_MICROMIPS_CALL16:
202    Type = ELF::R_MICROMIPS_CALL16;
203    break;
204  case Mips::fixup_MICROMIPS_GOT_DISP:
205    Type = ELF::R_MICROMIPS_GOT_DISP;
206    break;
207  case Mips::fixup_MICROMIPS_GOT_PAGE:
208    Type = ELF::R_MICROMIPS_GOT_PAGE;
209    break;
210  case Mips::fixup_MICROMIPS_GOT_OFST:
211    Type = ELF::R_MICROMIPS_GOT_OFST;
212    break;
213  case Mips::fixup_MICROMIPS_TLS_DTPREL_HI16:
214    Type = ELF::R_MICROMIPS_TLS_DTPREL_HI16;
215    break;
216  case Mips::fixup_MICROMIPS_TLS_DTPREL_LO16:
217    Type = ELF::R_MICROMIPS_TLS_DTPREL_LO16;
218    break;
219  case Mips::fixup_MICROMIPS_TLS_TPREL_HI16:
220    Type = ELF::R_MICROMIPS_TLS_TPREL_HI16;
221    break;
222  case Mips::fixup_MICROMIPS_TLS_TPREL_LO16:
223    Type = ELF::R_MICROMIPS_TLS_TPREL_LO16;
224    break;
225  }
226  return Type;
227}
228
229// Return true if R is either a GOT16 against a local symbol or HI16.
230static bool NeedsMatchingLo(const MCAssembler &Asm, const RelEntry &R) {
231  if (!R.Sym)
232    return false;
233
234  MCSymbolData &SD = Asm.getSymbolData(R.Sym->AliasedSymbol());
235
236  return ((R.Reloc.Type == ELF::R_MIPS_GOT16) && !SD.isExternal()) ||
237    (R.Reloc.Type == ELF::R_MIPS_HI16);
238}
239
240static bool HasMatchingLo(const MCAssembler &Asm, RelLsIter I, RelLsIter Last) {
241  if (I == Last)
242    return false;
243
244  RelLsIter Hi = I++;
245
246  return (I->Reloc.Type == ELF::R_MIPS_LO16) && (Hi->Sym == I->Sym) &&
247    (Hi->Offset == I->Offset);
248}
249
250static bool HasSameSymbol(const RelEntry &R0, const RelEntry &R1) {
251  return R0.Sym == R1.Sym;
252}
253
254static int CompareOffset(const RelEntry &R0, const RelEntry &R1) {
255  return (R0.Offset > R1.Offset) ? 1 : ((R0.Offset == R1.Offset) ? 0 : -1);
256}
257
258void MipsELFObjectWriter::sortRelocs(const MCAssembler &Asm,
259                                     std::vector<ELFRelocationEntry> &Relocs) {
260  // Call the default function first. Relocations are sorted in descending
261  // order of r_offset.
262  MCELFObjectTargetWriter::sortRelocs(Asm, Relocs);
263
264  RelLs RelocLs;
265  std::vector<RelLsIter> Unmatched;
266
267  // Fill RelocLs. Traverse Relocs backwards so that relocations in RelocLs
268  // are in ascending order of r_offset.
269  for (std::vector<ELFRelocationEntry>::reverse_iterator R = Relocs.rbegin();
270       R != Relocs.rend(); ++R) {
271     std::pair<const MCSymbolRefExpr*, int64_t> P =
272       MipsGetSymAndOffset(*R->Fixup);
273     RelocLs.push_back(RelEntry(*R, P.first ? &P.first->getSymbol() : 0,
274                                P.second));
275  }
276
277  // Get list of unmatched HI16 and GOT16.
278  for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R)
279    if (NeedsMatchingLo(Asm, *R) && !HasMatchingLo(Asm, R, --RelocLs.end()))
280      Unmatched.push_back(R);
281
282  // Insert unmatched HI16 and GOT16 immediately before their matching LO16.
283  for (std::vector<RelLsIter>::iterator U = Unmatched.begin();
284       U != Unmatched.end(); ++U) {
285    RelLsIter LoPos = RelocLs.end(), HiPos = *U;
286    bool MatchedLo = false;
287
288    for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R) {
289      if ((R->Reloc.Type == ELF::R_MIPS_LO16) && HasSameSymbol(*HiPos, *R) &&
290          (CompareOffset(*R, *HiPos) >= 0) &&
291          ((LoPos == RelocLs.end()) || ((CompareOffset(*R, *LoPos) < 0)) ||
292           (!MatchedLo && !CompareOffset(*R, *LoPos))))
293        LoPos = R;
294
295      MatchedLo = NeedsMatchingLo(Asm, *R) &&
296        HasMatchingLo(Asm, R, --RelocLs.end());
297    }
298
299    // If a matching LoPos was found, move HiPos and insert it before LoPos.
300    // Make the offsets of HiPos and LoPos match.
301    if (LoPos != RelocLs.end()) {
302      HiPos->Offset = LoPos->Offset;
303      RelocLs.insert(LoPos, *HiPos);
304      RelocLs.erase(HiPos);
305    }
306  }
307
308  // Put the sorted list back in reverse order.
309  assert(Relocs.size() == RelocLs.size());
310  unsigned I = RelocLs.size();
311
312  for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R)
313    Relocs[--I] = R->Reloc;
314}
315
316MCObjectWriter *llvm::createMipsELFObjectWriter(raw_ostream &OS,
317                                                uint8_t OSABI,
318                                                bool IsLittleEndian,
319                                                bool Is64Bit) {
320  MCELFObjectTargetWriter *MOTW = new MipsELFObjectWriter(Is64Bit, OSABI,
321                                                (Is64Bit) ? true : false,
322                                                IsLittleEndian);
323  return createELFObjectWriter(MOTW, OS, IsLittleEndian);
324}
325