1//===-- X86ELFObjectWriter.cpp - X86 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/X86FixupKinds.h"
11#include "MCTargetDesc/X86MCTargetDesc.h"
12#include "llvm/MC/MCELFObjectWriter.h"
13#include "llvm/MC/MCExpr.h"
14#include "llvm/MC/MCValue.h"
15#include "llvm/Support/ELF.h"
16#include "llvm/Support/ErrorHandling.h"
17
18using namespace llvm;
19
20namespace {
21  class X86ELFObjectWriter : public MCELFObjectTargetWriter {
22  public:
23    X86ELFObjectWriter(bool IsELF64, uint8_t OSABI, uint16_t EMachine);
24
25    ~X86ELFObjectWriter() override;
26
27  protected:
28    unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
29                          bool IsPCRel) const override;
30  };
31}
32
33X86ELFObjectWriter::X86ELFObjectWriter(bool IsELF64, uint8_t OSABI,
34                                       uint16_t EMachine)
35  : MCELFObjectTargetWriter(IsELF64, OSABI, EMachine,
36                            // Only i386 uses Rel instead of RelA.
37                            /*HasRelocationAddend*/ EMachine != ELF::EM_386) {}
38
39X86ELFObjectWriter::~X86ELFObjectWriter()
40{}
41
42enum X86_64RelType { RT64_64, RT64_32, RT64_32S, RT64_16, RT64_8 };
43
44static X86_64RelType getType64(unsigned Kind,
45                               MCSymbolRefExpr::VariantKind &Modifier,
46                               bool &IsPCRel) {
47  switch (Kind) {
48  default:
49    llvm_unreachable("Unimplemented");
50  case X86::reloc_global_offset_table8:
51    Modifier = MCSymbolRefExpr::VK_GOT;
52    IsPCRel = true;
53    return RT64_64;
54  case FK_Data_8:
55    return RT64_64;
56  case X86::reloc_signed_4byte:
57    if (Modifier == MCSymbolRefExpr::VK_None && !IsPCRel)
58      return RT64_32S;
59    return RT64_32;
60  case X86::reloc_global_offset_table:
61    Modifier = MCSymbolRefExpr::VK_GOT;
62    IsPCRel = true;
63    return RT64_32;
64  case FK_Data_4:
65  case FK_PCRel_4:
66  case X86::reloc_riprel_4byte:
67  case X86::reloc_riprel_4byte_movq_load:
68    return RT64_32;
69  case FK_Data_2:
70    return RT64_16;
71  case FK_PCRel_1:
72  case FK_Data_1:
73    return RT64_8;
74  }
75}
76
77static unsigned getRelocType64(MCSymbolRefExpr::VariantKind Modifier,
78                               X86_64RelType Type, bool IsPCRel) {
79  switch (Modifier) {
80  default:
81    llvm_unreachable("Unimplemented");
82  case MCSymbolRefExpr::VK_None:
83    switch (Type) {
84    case RT64_64:
85      return IsPCRel ? ELF::R_X86_64_PC64 : ELF::R_X86_64_64;
86    case RT64_32:
87      return IsPCRel ? ELF::R_X86_64_PC32 : ELF::R_X86_64_32;
88    case RT64_32S:
89      return ELF::R_X86_64_32S;
90    case RT64_16:
91      return IsPCRel ? ELF::R_X86_64_PC16 : ELF::R_X86_64_16;
92    case RT64_8:
93      return IsPCRel ? ELF::R_X86_64_PC8 : ELF::R_X86_64_8;
94    }
95  case MCSymbolRefExpr::VK_GOT:
96    switch (Type) {
97    case RT64_64:
98      return IsPCRel ? ELF::R_X86_64_GOTPC64 : ELF::R_X86_64_GOT64;
99    case RT64_32:
100      return IsPCRel ? ELF::R_X86_64_GOTPC32 : ELF::R_X86_64_GOT32;
101    case RT64_32S:
102    case RT64_16:
103    case RT64_8:
104      llvm_unreachable("Unimplemented");
105    }
106  case MCSymbolRefExpr::VK_GOTOFF:
107    assert(Type == RT64_64);
108    assert(!IsPCRel);
109    return ELF::R_X86_64_GOTOFF64;
110  case MCSymbolRefExpr::VK_TPOFF:
111    assert(!IsPCRel);
112    switch (Type) {
113    case RT64_64:
114      return ELF::R_X86_64_TPOFF64;
115    case RT64_32:
116      return ELF::R_X86_64_TPOFF32;
117    case RT64_32S:
118    case RT64_16:
119    case RT64_8:
120      llvm_unreachable("Unimplemented");
121    }
122  case MCSymbolRefExpr::VK_DTPOFF:
123    assert(!IsPCRel);
124    switch (Type) {
125    case RT64_64:
126      return ELF::R_X86_64_DTPOFF64;
127    case RT64_32:
128      return ELF::R_X86_64_DTPOFF32;
129    case RT64_32S:
130    case RT64_16:
131    case RT64_8:
132      llvm_unreachable("Unimplemented");
133    }
134  case MCSymbolRefExpr::VK_SIZE:
135    assert(!IsPCRel);
136    switch (Type) {
137    case RT64_64:
138      return ELF::R_X86_64_SIZE64;
139    case RT64_32:
140      return ELF::R_X86_64_SIZE32;
141    case RT64_32S:
142    case RT64_16:
143    case RT64_8:
144      llvm_unreachable("Unimplemented");
145    }
146  case MCSymbolRefExpr::VK_TLSGD:
147    assert(Type == RT64_32);
148    return ELF::R_X86_64_TLSGD;
149  case MCSymbolRefExpr::VK_GOTTPOFF:
150    assert(Type == RT64_32);
151    return ELF::R_X86_64_GOTTPOFF;
152  case MCSymbolRefExpr::VK_TLSLD:
153    assert(Type == RT64_32);
154    return ELF::R_X86_64_TLSLD;
155  case MCSymbolRefExpr::VK_PLT:
156    assert(Type == RT64_32);
157    return ELF::R_X86_64_PLT32;
158  case MCSymbolRefExpr::VK_GOTPCREL:
159    assert(Type == RT64_32);
160    return ELF::R_X86_64_GOTPCREL;
161  }
162}
163
164enum X86_32RelType { RT32_32, RT32_16, RT32_8 };
165
166static X86_32RelType getType32(X86_64RelType T) {
167  switch (T) {
168  case RT64_64:
169    llvm_unreachable("Unimplemented");
170  case RT64_32:
171  case RT64_32S:
172    return RT32_32;
173  case RT64_16:
174    return RT32_16;
175  case RT64_8:
176    return RT32_8;
177  }
178  llvm_unreachable("unexpected relocation type!");
179}
180
181static unsigned getRelocType32(MCSymbolRefExpr::VariantKind Modifier,
182                               X86_32RelType Type, bool IsPCRel) {
183  switch (Modifier) {
184  default:
185    llvm_unreachable("Unimplemented");
186  case MCSymbolRefExpr::VK_None:
187    switch (Type) {
188    case RT32_32:
189      return IsPCRel ? ELF::R_386_PC32 : ELF::R_386_32;
190    case RT32_16:
191      return IsPCRel ? ELF::R_386_PC16 : ELF::R_386_16;
192    case RT32_8:
193      return IsPCRel ? ELF::R_386_PC8 : ELF::R_386_8;
194    }
195  case MCSymbolRefExpr::VK_GOT:
196    assert(Type == RT32_32);
197    return IsPCRel ? ELF::R_386_GOTPC : ELF::R_386_GOT32;
198  case MCSymbolRefExpr::VK_GOTOFF:
199    assert(Type == RT32_32);
200    assert(!IsPCRel);
201    return ELF::R_386_GOTOFF;
202  case MCSymbolRefExpr::VK_TPOFF:
203    assert(Type == RT32_32);
204    assert(!IsPCRel);
205    return ELF::R_386_TLS_LE_32;
206  case MCSymbolRefExpr::VK_DTPOFF:
207    assert(Type == RT32_32);
208    assert(!IsPCRel);
209    return ELF::R_386_TLS_LDO_32;
210  case MCSymbolRefExpr::VK_TLSGD:
211    assert(Type == RT32_32);
212    assert(!IsPCRel);
213    return ELF::R_386_TLS_GD;
214  case MCSymbolRefExpr::VK_GOTTPOFF:
215    assert(Type == RT32_32);
216    assert(!IsPCRel);
217    return ELF::R_386_TLS_IE_32;
218  case MCSymbolRefExpr::VK_PLT:
219    assert(Type == RT32_32);
220    return ELF::R_386_PLT32;
221  case MCSymbolRefExpr::VK_INDNTPOFF:
222    assert(Type == RT32_32);
223    assert(!IsPCRel);
224    return ELF::R_386_TLS_IE;
225  case MCSymbolRefExpr::VK_NTPOFF:
226    assert(Type == RT32_32);
227    assert(!IsPCRel);
228    return ELF::R_386_TLS_LE;
229  case MCSymbolRefExpr::VK_GOTNTPOFF:
230    assert(Type == RT32_32);
231    assert(!IsPCRel);
232    return ELF::R_386_TLS_GOTIE;
233  case MCSymbolRefExpr::VK_TLSLDM:
234    assert(Type == RT32_32);
235    assert(!IsPCRel);
236    return ELF::R_386_TLS_LDM;
237  }
238}
239
240unsigned X86ELFObjectWriter::GetRelocType(const MCValue &Target,
241                                          const MCFixup &Fixup,
242                                          bool IsPCRel) const {
243  MCSymbolRefExpr::VariantKind Modifier = Target.getAccessVariant();
244  X86_64RelType Type = getType64(Fixup.getKind(), Modifier, IsPCRel);
245  if (getEMachine() == ELF::EM_X86_64)
246    return getRelocType64(Modifier, Type, IsPCRel);
247
248  assert(getEMachine() == ELF::EM_386 && "Unsupported ELF machine type.");
249  return getRelocType32(Modifier, getType32(Type), IsPCRel);
250}
251
252MCObjectWriter *llvm::createX86ELFObjectWriter(raw_pwrite_stream &OS,
253                                               bool IsELF64, uint8_t OSABI,
254                                               uint16_t EMachine) {
255  MCELFObjectTargetWriter *MOTW =
256    new X86ELFObjectWriter(IsELF64, OSABI, EMachine);
257  return createELFObjectWriter(MOTW, OS,  /*IsLittleEndian=*/true);
258}
259