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 
21 using namespace llvm;
22 
23 namespace {
24   struct RelEntry {
RelEntry__anonf2e8309f0111::RelEntry25     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 
MipsELFObjectWriter(bool _is64Bit,uint8_t OSABI,bool _isN64,bool IsLittleEndian)55 MipsELFObjectWriter::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 
~MipsELFObjectWriter()61 MipsELFObjectWriter::~MipsELFObjectWriter() {}
62 
ExplicitRelSym(const MCAssembler & Asm,const MCValue & Target,const MCFragment & F,const MCFixup & Fixup,bool IsPCRel) const63 const 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 
GetRelocType(const MCValue & Target,const MCFixup & Fixup,bool IsPCRel,bool IsRelocWithSymbol,int64_t Addend) const78 unsigned 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.
NeedsMatchingLo(const MCAssembler & Asm,const RelEntry & R)230 static 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 
HasMatchingLo(const MCAssembler & Asm,RelLsIter I,RelLsIter Last)240 static 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 
HasSameSymbol(const RelEntry & R0,const RelEntry & R1)250 static bool HasSameSymbol(const RelEntry &R0, const RelEntry &R1) {
251   return R0.Sym == R1.Sym;
252 }
253 
CompareOffset(const RelEntry & R0,const RelEntry & R1)254 static int CompareOffset(const RelEntry &R0, const RelEntry &R1) {
255   return (R0.Offset > R1.Offset) ? 1 : ((R0.Offset == R1.Offset) ? 0 : -1);
256 }
257 
sortRelocs(const MCAssembler & Asm,std::vector<ELFRelocationEntry> & Relocs)258 void 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 
createMipsELFObjectWriter(raw_ostream & OS,uint8_t OSABI,bool IsLittleEndian,bool Is64Bit)316 MCObjectWriter *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