xref: /freebsd/contrib/llvm-project/llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp (revision 6966ac055c3b7a39266fb982493330df7a097997)
1 //===-- X86ELFObjectWriter.cpp - X86 ELF Writer ---------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "MCTargetDesc/X86FixupKinds.h"
10 #include "MCTargetDesc/X86MCTargetDesc.h"
11 #include "llvm/BinaryFormat/ELF.h"
12 #include "llvm/MC/MCAsmInfo.h"
13 #include "llvm/MC/MCContext.h"
14 #include "llvm/MC/MCELFObjectWriter.h"
15 #include "llvm/MC/MCExpr.h"
16 #include "llvm/MC/MCFixup.h"
17 #include "llvm/MC/MCObjectWriter.h"
18 #include "llvm/MC/MCValue.h"
19 #include "llvm/Support/ErrorHandling.h"
20 #include <cassert>
21 #include <cstdint>
22 
23 using namespace llvm;
24 
25 namespace {
26 
27 class X86ELFObjectWriter : public MCELFObjectTargetWriter {
28 public:
29   X86ELFObjectWriter(bool IsELF64, uint8_t OSABI, uint16_t EMachine);
30   ~X86ELFObjectWriter() override = default;
31 
32 protected:
33   unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
34                         const MCFixup &Fixup, bool IsPCRel) const override;
35 };
36 
37 } // end anonymous namespace
38 
39 X86ELFObjectWriter::X86ELFObjectWriter(bool IsELF64, uint8_t OSABI,
40                                        uint16_t EMachine)
41     : MCELFObjectTargetWriter(IsELF64, OSABI, EMachine,
42                               // Only i386 and IAMCU use Rel instead of RelA.
43                               /*HasRelocationAddend*/
44                               (EMachine != ELF::EM_386) &&
45                                   (EMachine != ELF::EM_IAMCU)) {}
46 
47 enum X86_64RelType { RT64_NONE, RT64_64, RT64_32, RT64_32S, RT64_16, RT64_8 };
48 
49 static X86_64RelType getType64(unsigned Kind,
50                                MCSymbolRefExpr::VariantKind &Modifier,
51                                bool &IsPCRel) {
52   switch (Kind) {
53   default:
54     llvm_unreachable("Unimplemented");
55   case FK_NONE:
56     return RT64_NONE;
57   case X86::reloc_global_offset_table8:
58     Modifier = MCSymbolRefExpr::VK_GOT;
59     IsPCRel = true;
60     return RT64_64;
61   case FK_Data_8:
62     return RT64_64;
63   case X86::reloc_signed_4byte:
64   case X86::reloc_signed_4byte_relax:
65     if (Modifier == MCSymbolRefExpr::VK_None && !IsPCRel)
66       return RT64_32S;
67     return RT64_32;
68   case X86::reloc_global_offset_table:
69     Modifier = MCSymbolRefExpr::VK_GOT;
70     IsPCRel = true;
71     return RT64_32;
72   case FK_Data_4:
73   case FK_PCRel_4:
74   case X86::reloc_riprel_4byte:
75   case X86::reloc_riprel_4byte_relax:
76   case X86::reloc_riprel_4byte_relax_rex:
77   case X86::reloc_riprel_4byte_movq_load:
78     return RT64_32;
79   case X86::reloc_branch_4byte_pcrel:
80     Modifier = MCSymbolRefExpr::VK_PLT;
81     return RT64_32;
82   case FK_PCRel_2:
83   case FK_Data_2:
84     return RT64_16;
85   case FK_PCRel_1:
86   case FK_Data_1:
87     return RT64_8;
88   }
89 }
90 
91 static void checkIs32(MCContext &Ctx, SMLoc Loc, X86_64RelType Type) {
92   if (Type != RT64_32)
93     Ctx.reportError(Loc,
94                     "32 bit reloc applied to a field with a different size");
95 }
96 
97 static unsigned getRelocType64(MCContext &Ctx, SMLoc Loc,
98                                MCSymbolRefExpr::VariantKind Modifier,
99                                X86_64RelType Type, bool IsPCRel,
100                                unsigned Kind) {
101   switch (Modifier) {
102   default:
103     llvm_unreachable("Unimplemented");
104   case MCSymbolRefExpr::VK_None:
105   case MCSymbolRefExpr::VK_X86_ABS8:
106     switch (Type) {
107     case RT64_NONE:
108       if (Modifier == MCSymbolRefExpr::VK_None)
109         return ELF::R_X86_64_NONE;
110       llvm_unreachable("Unimplemented");
111     case RT64_64:
112       return IsPCRel ? ELF::R_X86_64_PC64 : ELF::R_X86_64_64;
113     case RT64_32:
114       return IsPCRel ? ELF::R_X86_64_PC32 : ELF::R_X86_64_32;
115     case RT64_32S:
116       return ELF::R_X86_64_32S;
117     case RT64_16:
118       return IsPCRel ? ELF::R_X86_64_PC16 : ELF::R_X86_64_16;
119     case RT64_8:
120       return IsPCRel ? ELF::R_X86_64_PC8 : ELF::R_X86_64_8;
121     }
122     llvm_unreachable("unexpected relocation type!");
123   case MCSymbolRefExpr::VK_GOT:
124     switch (Type) {
125     case RT64_64:
126       return IsPCRel ? ELF::R_X86_64_GOTPC64 : ELF::R_X86_64_GOT64;
127     case RT64_32:
128       return IsPCRel ? ELF::R_X86_64_GOTPC32 : ELF::R_X86_64_GOT32;
129     case RT64_32S:
130     case RT64_16:
131     case RT64_8:
132     case RT64_NONE:
133       llvm_unreachable("Unimplemented");
134     }
135     llvm_unreachable("unexpected relocation type!");
136   case MCSymbolRefExpr::VK_GOTOFF:
137     assert(Type == RT64_64);
138     assert(!IsPCRel);
139     return ELF::R_X86_64_GOTOFF64;
140   case MCSymbolRefExpr::VK_TPOFF:
141     assert(!IsPCRel);
142     switch (Type) {
143     case RT64_64:
144       return ELF::R_X86_64_TPOFF64;
145     case RT64_32:
146       return ELF::R_X86_64_TPOFF32;
147     case RT64_32S:
148     case RT64_16:
149     case RT64_8:
150     case RT64_NONE:
151       llvm_unreachable("Unimplemented");
152     }
153     llvm_unreachable("unexpected relocation type!");
154   case MCSymbolRefExpr::VK_DTPOFF:
155     assert(!IsPCRel);
156     switch (Type) {
157     case RT64_64:
158       return ELF::R_X86_64_DTPOFF64;
159     case RT64_32:
160       return ELF::R_X86_64_DTPOFF32;
161     case RT64_32S:
162     case RT64_16:
163     case RT64_8:
164     case RT64_NONE:
165       llvm_unreachable("Unimplemented");
166     }
167     llvm_unreachable("unexpected relocation type!");
168   case MCSymbolRefExpr::VK_SIZE:
169     assert(!IsPCRel);
170     switch (Type) {
171     case RT64_64:
172       return ELF::R_X86_64_SIZE64;
173     case RT64_32:
174       return ELF::R_X86_64_SIZE32;
175     case RT64_32S:
176     case RT64_16:
177     case RT64_8:
178     case RT64_NONE:
179       llvm_unreachable("Unimplemented");
180     }
181     llvm_unreachable("unexpected relocation type!");
182   case MCSymbolRefExpr::VK_TLSCALL:
183     return ELF::R_X86_64_TLSDESC_CALL;
184   case MCSymbolRefExpr::VK_TLSDESC:
185     return ELF::R_X86_64_GOTPC32_TLSDESC;
186   case MCSymbolRefExpr::VK_TLSGD:
187     checkIs32(Ctx, Loc, Type);
188     return ELF::R_X86_64_TLSGD;
189   case MCSymbolRefExpr::VK_GOTTPOFF:
190     checkIs32(Ctx, Loc, Type);
191     return ELF::R_X86_64_GOTTPOFF;
192   case MCSymbolRefExpr::VK_TLSLD:
193     checkIs32(Ctx, Loc, Type);
194     return ELF::R_X86_64_TLSLD;
195   case MCSymbolRefExpr::VK_PLT:
196     checkIs32(Ctx, Loc, Type);
197     return ELF::R_X86_64_PLT32;
198   case MCSymbolRefExpr::VK_GOTPCREL:
199     checkIs32(Ctx, Loc, Type);
200     // Older versions of ld.bfd/ld.gold/lld
201     // do not support GOTPCRELX/REX_GOTPCRELX,
202     // and we want to keep back-compatibility.
203     if (!Ctx.getAsmInfo()->canRelaxRelocations())
204       return ELF::R_X86_64_GOTPCREL;
205     switch (Kind) {
206     default:
207       return ELF::R_X86_64_GOTPCREL;
208     case X86::reloc_riprel_4byte_relax:
209       return ELF::R_X86_64_GOTPCRELX;
210     case X86::reloc_riprel_4byte_relax_rex:
211     case X86::reloc_riprel_4byte_movq_load:
212       return ELF::R_X86_64_REX_GOTPCRELX;
213     }
214     llvm_unreachable("unexpected relocation type!");
215   }
216 }
217 
218 enum X86_32RelType { RT32_NONE, RT32_32, RT32_16, RT32_8 };
219 
220 static X86_32RelType getType32(X86_64RelType T) {
221   switch (T) {
222   case RT64_NONE:
223     return RT32_NONE;
224   case RT64_64:
225     llvm_unreachable("Unimplemented");
226   case RT64_32:
227   case RT64_32S:
228     return RT32_32;
229   case RT64_16:
230     return RT32_16;
231   case RT64_8:
232     return RT32_8;
233   }
234   llvm_unreachable("unexpected relocation type!");
235 }
236 
237 static unsigned getRelocType32(MCContext &Ctx,
238                                MCSymbolRefExpr::VariantKind Modifier,
239                                X86_32RelType Type, bool IsPCRel,
240                                unsigned Kind) {
241   switch (Modifier) {
242   default:
243     llvm_unreachable("Unimplemented");
244   case MCSymbolRefExpr::VK_None:
245   case MCSymbolRefExpr::VK_X86_ABS8:
246     switch (Type) {
247     case RT32_NONE:
248       if (Modifier == MCSymbolRefExpr::VK_None)
249         return ELF::R_386_NONE;
250       llvm_unreachable("Unimplemented");
251     case RT32_32:
252       return IsPCRel ? ELF::R_386_PC32 : ELF::R_386_32;
253     case RT32_16:
254       return IsPCRel ? ELF::R_386_PC16 : ELF::R_386_16;
255     case RT32_8:
256       return IsPCRel ? ELF::R_386_PC8 : ELF::R_386_8;
257     }
258     llvm_unreachable("unexpected relocation type!");
259   case MCSymbolRefExpr::VK_GOT:
260     assert(Type == RT32_32);
261     if (IsPCRel)
262       return ELF::R_386_GOTPC;
263     // Older versions of ld.bfd/ld.gold/lld do not support R_386_GOT32X and we
264     // want to maintain compatibility.
265     if (!Ctx.getAsmInfo()->canRelaxRelocations())
266       return ELF::R_386_GOT32;
267 
268     return Kind == X86::reloc_signed_4byte_relax ? ELF::R_386_GOT32X
269                                                  : ELF::R_386_GOT32;
270   case MCSymbolRefExpr::VK_GOTOFF:
271     assert(Type == RT32_32);
272     assert(!IsPCRel);
273     return ELF::R_386_GOTOFF;
274   case MCSymbolRefExpr::VK_TLSCALL:
275     return ELF::R_386_TLS_DESC_CALL;
276   case MCSymbolRefExpr::VK_TLSDESC:
277     return ELF::R_386_TLS_GOTDESC;
278   case MCSymbolRefExpr::VK_TPOFF:
279     assert(Type == RT32_32);
280     assert(!IsPCRel);
281     return ELF::R_386_TLS_LE_32;
282   case MCSymbolRefExpr::VK_DTPOFF:
283     assert(Type == RT32_32);
284     assert(!IsPCRel);
285     return ELF::R_386_TLS_LDO_32;
286   case MCSymbolRefExpr::VK_TLSGD:
287     assert(Type == RT32_32);
288     assert(!IsPCRel);
289     return ELF::R_386_TLS_GD;
290   case MCSymbolRefExpr::VK_GOTTPOFF:
291     assert(Type == RT32_32);
292     assert(!IsPCRel);
293     return ELF::R_386_TLS_IE_32;
294   case MCSymbolRefExpr::VK_PLT:
295     assert(Type == RT32_32);
296     return ELF::R_386_PLT32;
297   case MCSymbolRefExpr::VK_INDNTPOFF:
298     assert(Type == RT32_32);
299     assert(!IsPCRel);
300     return ELF::R_386_TLS_IE;
301   case MCSymbolRefExpr::VK_NTPOFF:
302     assert(Type == RT32_32);
303     assert(!IsPCRel);
304     return ELF::R_386_TLS_LE;
305   case MCSymbolRefExpr::VK_GOTNTPOFF:
306     assert(Type == RT32_32);
307     assert(!IsPCRel);
308     return ELF::R_386_TLS_GOTIE;
309   case MCSymbolRefExpr::VK_TLSLDM:
310     assert(Type == RT32_32);
311     assert(!IsPCRel);
312     return ELF::R_386_TLS_LDM;
313   }
314 }
315 
316 unsigned X86ELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target,
317                                           const MCFixup &Fixup,
318                                           bool IsPCRel) const {
319   MCSymbolRefExpr::VariantKind Modifier = Target.getAccessVariant();
320   unsigned Kind = Fixup.getKind();
321   X86_64RelType Type = getType64(Kind, Modifier, IsPCRel);
322   if (getEMachine() == ELF::EM_X86_64)
323     return getRelocType64(Ctx, Fixup.getLoc(), Modifier, Type, IsPCRel, Kind);
324 
325   assert((getEMachine() == ELF::EM_386 || getEMachine() == ELF::EM_IAMCU) &&
326          "Unsupported ELF machine type.");
327   return getRelocType32(Ctx, Modifier, getType32(Type), IsPCRel, Kind);
328 }
329 
330 std::unique_ptr<MCObjectTargetWriter>
331 llvm::createX86ELFObjectWriter(bool IsELF64, uint8_t OSABI, uint16_t EMachine) {
332   return llvm::make_unique<X86ELFObjectWriter>(IsELF64, OSABI, EMachine);
333 }
334