ARMELFObjectWriter.cpp revision 36b56886974eae4f9c5ebc96befd3e7bfe5de338 
1//===-- ARMELFObjectWriter.cpp - ARM 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/ARMMCTargetDesc.h"
11#include "MCTargetDesc/ARMFixupKinds.h"
12#include "llvm/ADT/Statistic.h"
13#include "llvm/ADT/StringSwitch.h"
14#include "llvm/MC/MCELFObjectWriter.h"
15#include "llvm/MC/MCExpr.h"
16#include "llvm/MC/MCSectionELF.h"
17#include "llvm/MC/MCValue.h"
18#include "llvm/Support/Debug.h"
19#include "llvm/Support/ErrorHandling.h"
20#include "llvm/Support/raw_ostream.h"
21
22using namespace llvm;
23
24namespace {
25  class ARMELFObjectWriter : public MCELFObjectTargetWriter {
26    enum { DefaultEABIVersion = 0x05000000U };
27    unsigned GetRelocTypeInner(const MCValue &Target,
28                               const MCFixup &Fixup,
29                               bool IsPCRel) const;
30
31
32  public:
33    ARMELFObjectWriter(uint8_t OSABI);
34
35    virtual ~ARMELFObjectWriter();
36
37    unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
38                          bool IsPCRel) const override;
39
40    bool needsRelocateWithSymbol(unsigned Type) const override;
41  };
42}
43
44ARMELFObjectWriter::ARMELFObjectWriter(uint8_t OSABI)
45  : MCELFObjectTargetWriter(/*Is64Bit*/ false, OSABI,
46                            ELF::EM_ARM,
47                            /*HasRelocationAddend*/ false) {}
48
49ARMELFObjectWriter::~ARMELFObjectWriter() {}
50
51bool ARMELFObjectWriter::needsRelocateWithSymbol(unsigned Type) const {
52  // FIXME: This is extremelly conservative. This really needs to use a
53  // whitelist with a clear explanation for why each realocation needs to
54  // point to the symbol, not to the section.
55  switch (Type) {
56  default:
57    return true;
58
59  case ELF::R_ARM_PREL31:
60  case ELF::R_ARM_ABS32:
61    return false;
62  }
63}
64
65// Need to examine the Fixup when determining whether to
66// emit the relocation as an explicit symbol or as a section relative
67// offset
68unsigned ARMELFObjectWriter::GetRelocType(const MCValue &Target,
69                                          const MCFixup &Fixup,
70                                          bool IsPCRel) const {
71  return GetRelocTypeInner(Target, Fixup, IsPCRel);
72}
73
74unsigned ARMELFObjectWriter::GetRelocTypeInner(const MCValue &Target,
75                                               const MCFixup &Fixup,
76                                               bool IsPCRel) const  {
77  MCSymbolRefExpr::VariantKind Modifier = Fixup.getAccessVariant();
78
79  unsigned Type = 0;
80  if (IsPCRel) {
81    switch ((unsigned)Fixup.getKind()) {
82    default: llvm_unreachable("Unimplemented");
83    case FK_Data_4:
84      switch (Modifier) {
85      default: llvm_unreachable("Unsupported Modifier");
86      case MCSymbolRefExpr::VK_None:
87        Type = ELF::R_ARM_REL32;
88        break;
89      case MCSymbolRefExpr::VK_TLSGD:
90        llvm_unreachable("unimplemented");
91      case MCSymbolRefExpr::VK_GOTTPOFF:
92        Type = ELF::R_ARM_TLS_IE32;
93        break;
94      }
95      break;
96    case ARM::fixup_arm_blx:
97    case ARM::fixup_arm_uncondbl:
98      switch (Modifier) {
99      case MCSymbolRefExpr::VK_PLT:
100        Type = ELF::R_ARM_PLT32;
101        break;
102      case MCSymbolRefExpr::VK_ARM_TLSCALL:
103        Type = ELF::R_ARM_TLS_CALL;
104        break;
105      default:
106        Type = ELF::R_ARM_CALL;
107        break;
108      }
109      break;
110    case ARM::fixup_arm_condbl:
111    case ARM::fixup_arm_condbranch:
112    case ARM::fixup_arm_uncondbranch:
113      Type = ELF::R_ARM_JUMP24;
114      break;
115    case ARM::fixup_t2_condbranch:
116    case ARM::fixup_t2_uncondbranch:
117      Type = ELF::R_ARM_THM_JUMP24;
118      break;
119    case ARM::fixup_arm_movt_hi16:
120      Type = ELF::R_ARM_MOVT_PREL;
121      break;
122    case ARM::fixup_arm_movw_lo16:
123      Type = ELF::R_ARM_MOVW_PREL_NC;
124      break;
125    case ARM::fixup_t2_movt_hi16:
126      Type = ELF::R_ARM_THM_MOVT_PREL;
127      break;
128    case ARM::fixup_t2_movw_lo16:
129      Type = ELF::R_ARM_THM_MOVW_PREL_NC;
130      break;
131    case ARM::fixup_arm_thumb_bl:
132    case ARM::fixup_arm_thumb_blx:
133      switch (Modifier) {
134      case MCSymbolRefExpr::VK_ARM_TLSCALL:
135        Type = ELF::R_ARM_THM_TLS_CALL;
136        break;
137      default:
138        Type = ELF::R_ARM_THM_CALL;
139        break;
140      }
141      break;
142    }
143  } else {
144    switch ((unsigned)Fixup.getKind()) {
145    default: llvm_unreachable("invalid fixup kind!");
146    case FK_Data_4:
147      switch (Modifier) {
148      default: llvm_unreachable("Unsupported Modifier");
149      case MCSymbolRefExpr::VK_ARM_NONE:
150        Type = ELF::R_ARM_NONE;
151        break;
152      case MCSymbolRefExpr::VK_GOT:
153        Type = ELF::R_ARM_GOT_BREL;
154        break;
155      case MCSymbolRefExpr::VK_TLSGD:
156        Type = ELF::R_ARM_TLS_GD32;
157        break;
158      case MCSymbolRefExpr::VK_TPOFF:
159        Type = ELF::R_ARM_TLS_LE32;
160        break;
161      case MCSymbolRefExpr::VK_GOTTPOFF:
162        Type = ELF::R_ARM_TLS_IE32;
163        break;
164      case MCSymbolRefExpr::VK_None:
165        Type = ELF::R_ARM_ABS32;
166        break;
167      case MCSymbolRefExpr::VK_GOTOFF:
168        Type = ELF::R_ARM_GOTOFF32;
169        break;
170      case MCSymbolRefExpr::VK_ARM_TARGET1:
171        Type = ELF::R_ARM_TARGET1;
172        break;
173      case MCSymbolRefExpr::VK_ARM_TARGET2:
174        Type = ELF::R_ARM_TARGET2;
175        break;
176      case MCSymbolRefExpr::VK_ARM_PREL31:
177        Type = ELF::R_ARM_PREL31;
178        break;
179      case MCSymbolRefExpr::VK_ARM_TLSLDO:
180        Type = ELF::R_ARM_TLS_LDO32;
181        break;
182      case MCSymbolRefExpr::VK_ARM_TLSCALL:
183        Type = ELF::R_ARM_TLS_CALL;
184        break;
185      case MCSymbolRefExpr::VK_ARM_TLSDESC:
186        Type = ELF::R_ARM_TLS_GOTDESC;
187        break;
188      case MCSymbolRefExpr::VK_ARM_TLSDESCSEQ:
189        Type = ELF::R_ARM_TLS_DESCSEQ;
190        break;
191      }
192      break;
193    case ARM::fixup_arm_ldst_pcrel_12:
194    case ARM::fixup_arm_pcrel_10:
195    case ARM::fixup_arm_adr_pcrel_12:
196    case ARM::fixup_arm_thumb_bl:
197    case ARM::fixup_arm_thumb_cb:
198    case ARM::fixup_arm_thumb_cp:
199    case ARM::fixup_arm_thumb_br:
200      llvm_unreachable("Unimplemented");
201    case ARM::fixup_arm_condbranch:
202    case ARM::fixup_arm_uncondbranch:
203      Type = ELF::R_ARM_JUMP24;
204      break;
205    case ARM::fixup_arm_movt_hi16:
206      Type = ELF::R_ARM_MOVT_ABS;
207      break;
208    case ARM::fixup_arm_movw_lo16:
209      Type = ELF::R_ARM_MOVW_ABS_NC;
210      break;
211    case ARM::fixup_t2_movt_hi16:
212      Type = ELF::R_ARM_THM_MOVT_ABS;
213      break;
214    case ARM::fixup_t2_movw_lo16:
215      Type = ELF::R_ARM_THM_MOVW_ABS_NC;
216      break;
217    }
218  }
219
220  return Type;
221}
222
223MCObjectWriter *llvm::createARMELFObjectWriter(raw_ostream &OS,
224                                               uint8_t OSABI,
225                                               bool IsLittleEndian) {
226  MCELFObjectTargetWriter *MOTW = new ARMELFObjectWriter(OSABI);
227  return createELFObjectWriter(MOTW, OS, IsLittleEndian);
228}
229