1 //===- llvm/MC/MCWinCOFFStreamer.cpp --------------------------------------===//
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 // This file contains an implementation of a Windows COFF object file streamer.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "llvm/ADT/SmallString.h"
15 #include "llvm/ADT/SmallVector.h"
16 #include "llvm/ADT/Triple.h"
17 #include "llvm/ADT/Twine.h"
18 #include "llvm/BinaryFormat/COFF.h"
19 #include "llvm/MC/MCAsmBackend.h"
20 #include "llvm/MC/MCAssembler.h"
21 #include "llvm/MC/MCCodeEmitter.h"
22 #include "llvm/MC/MCContext.h"
23 #include "llvm/MC/MCExpr.h"
24 #include "llvm/MC/MCFixup.h"
25 #include "llvm/MC/MCFragment.h"
26 #include "llvm/MC/MCObjectFileInfo.h"
27 #include "llvm/MC/MCObjectStreamer.h"
28 #include "llvm/MC/MCObjectWriter.h"
29 #include "llvm/MC/MCSection.h"
30 #include "llvm/MC/MCSymbolCOFF.h"
31 #include "llvm/MC/MCWinCOFFStreamer.h"
32 #include "llvm/Support/Casting.h"
33 #include "llvm/Support/ErrorHandling.h"
34 #include "llvm/Support/MathExtras.h"
35 #include "llvm/Support/SMLoc.h"
36 #include "llvm/Support/raw_ostream.h"
37 #include <algorithm>
38 #include <cassert>
39 #include <cstdint>
40
41 using namespace llvm;
42
43 #define DEBUG_TYPE "WinCOFFStreamer"
44
MCWinCOFFStreamer(MCContext & Context,std::unique_ptr<MCAsmBackend> MAB,std::unique_ptr<MCCodeEmitter> CE,std::unique_ptr<MCObjectWriter> OW)45 MCWinCOFFStreamer::MCWinCOFFStreamer(MCContext &Context,
46 std::unique_ptr<MCAsmBackend> MAB,
47 std::unique_ptr<MCCodeEmitter> CE,
48 std::unique_ptr<MCObjectWriter> OW)
49 : MCObjectStreamer(Context, std::move(MAB), std::move(OW), std::move(CE)),
50 CurSymbol(nullptr) {}
51
EmitInstToData(const MCInst & Inst,const MCSubtargetInfo & STI)52 void MCWinCOFFStreamer::EmitInstToData(const MCInst &Inst,
53 const MCSubtargetInfo &STI) {
54 MCDataFragment *DF = getOrCreateDataFragment();
55
56 SmallVector<MCFixup, 4> Fixups;
57 SmallString<256> Code;
58 raw_svector_ostream VecOS(Code);
59 getAssembler().getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
60
61 // Add the fixups and data.
62 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
63 Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
64 DF->getFixups().push_back(Fixups[i]);
65 }
66 DF->setHasInstructions(STI);
67 DF->getContents().append(Code.begin(), Code.end());
68 }
69
InitSections(bool NoExecStack)70 void MCWinCOFFStreamer::InitSections(bool NoExecStack) {
71 // FIXME: this is identical to the ELF one.
72 // This emulates the same behavior of GNU as. This makes it easier
73 // to compare the output as the major sections are in the same order.
74 SwitchSection(getContext().getObjectFileInfo()->getTextSection());
75 EmitCodeAlignment(4);
76
77 SwitchSection(getContext().getObjectFileInfo()->getDataSection());
78 EmitCodeAlignment(4);
79
80 SwitchSection(getContext().getObjectFileInfo()->getBSSSection());
81 EmitCodeAlignment(4);
82
83 SwitchSection(getContext().getObjectFileInfo()->getTextSection());
84 }
85
EmitLabel(MCSymbol * S,SMLoc Loc)86 void MCWinCOFFStreamer::EmitLabel(MCSymbol *S, SMLoc Loc) {
87 auto *Symbol = cast<MCSymbolCOFF>(S);
88 MCObjectStreamer::EmitLabel(Symbol, Loc);
89 }
90
EmitAssemblerFlag(MCAssemblerFlag Flag)91 void MCWinCOFFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
92 llvm_unreachable("not implemented");
93 }
94
EmitThumbFunc(MCSymbol * Func)95 void MCWinCOFFStreamer::EmitThumbFunc(MCSymbol *Func) {
96 llvm_unreachable("not implemented");
97 }
98
EmitSymbolAttribute(MCSymbol * S,MCSymbolAttr Attribute)99 bool MCWinCOFFStreamer::EmitSymbolAttribute(MCSymbol *S,
100 MCSymbolAttr Attribute) {
101 auto *Symbol = cast<MCSymbolCOFF>(S);
102 getAssembler().registerSymbol(*Symbol);
103
104 switch (Attribute) {
105 default: return false;
106 case MCSA_WeakReference:
107 case MCSA_Weak:
108 Symbol->setIsWeakExternal();
109 Symbol->setExternal(true);
110 break;
111 case MCSA_Global:
112 Symbol->setExternal(true);
113 break;
114 case MCSA_AltEntry:
115 llvm_unreachable("COFF doesn't support the .alt_entry attribute");
116 }
117
118 return true;
119 }
120
EmitSymbolDesc(MCSymbol * Symbol,unsigned DescValue)121 void MCWinCOFFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
122 llvm_unreachable("not implemented");
123 }
124
BeginCOFFSymbolDef(MCSymbol const * S)125 void MCWinCOFFStreamer::BeginCOFFSymbolDef(MCSymbol const *S) {
126 auto *Symbol = cast<MCSymbolCOFF>(S);
127 if (CurSymbol)
128 Error("starting a new symbol definition without completing the "
129 "previous one");
130 CurSymbol = Symbol;
131 }
132
EmitCOFFSymbolStorageClass(int StorageClass)133 void MCWinCOFFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
134 if (!CurSymbol) {
135 Error("storage class specified outside of symbol definition");
136 return;
137 }
138
139 if (StorageClass & ~COFF::SSC_Invalid) {
140 Error("storage class value '" + Twine(StorageClass) +
141 "' out of range");
142 return;
143 }
144
145 getAssembler().registerSymbol(*CurSymbol);
146 cast<MCSymbolCOFF>(CurSymbol)->setClass((uint16_t)StorageClass);
147 }
148
EmitCOFFSymbolType(int Type)149 void MCWinCOFFStreamer::EmitCOFFSymbolType(int Type) {
150 if (!CurSymbol) {
151 Error("symbol type specified outside of a symbol definition");
152 return;
153 }
154
155 if (Type & ~0xffff) {
156 Error("type value '" + Twine(Type) + "' out of range");
157 return;
158 }
159
160 getAssembler().registerSymbol(*CurSymbol);
161 cast<MCSymbolCOFF>(CurSymbol)->setType((uint16_t)Type);
162 }
163
EndCOFFSymbolDef()164 void MCWinCOFFStreamer::EndCOFFSymbolDef() {
165 if (!CurSymbol)
166 Error("ending symbol definition without starting one");
167 CurSymbol = nullptr;
168 }
169
EmitCOFFSafeSEH(MCSymbol const * Symbol)170 void MCWinCOFFStreamer::EmitCOFFSafeSEH(MCSymbol const *Symbol) {
171 // SafeSEH is a feature specific to 32-bit x86. It does not exist (and is
172 // unnecessary) on all platforms which use table-based exception dispatch.
173 if (getContext().getObjectFileInfo()->getTargetTriple().getArch() !=
174 Triple::x86)
175 return;
176
177 const MCSymbolCOFF *CSymbol = cast<MCSymbolCOFF>(Symbol);
178 if (CSymbol->isSafeSEH())
179 return;
180
181 MCSection *SXData = getContext().getObjectFileInfo()->getSXDataSection();
182 getAssembler().registerSection(*SXData);
183 if (SXData->getAlignment() < 4)
184 SXData->setAlignment(4);
185
186 new MCSymbolIdFragment(Symbol, SXData);
187
188 getAssembler().registerSymbol(*Symbol);
189 CSymbol->setIsSafeSEH();
190
191 // The Microsoft linker requires that the symbol type of a handler be
192 // function. Go ahead and oblige it here.
193 CSymbol->setType(COFF::IMAGE_SYM_DTYPE_FUNCTION
194 << COFF::SCT_COMPLEX_TYPE_SHIFT);
195 }
196
EmitCOFFSymbolIndex(MCSymbol const * Symbol)197 void MCWinCOFFStreamer::EmitCOFFSymbolIndex(MCSymbol const *Symbol) {
198 MCSection *Sec = getCurrentSectionOnly();
199 getAssembler().registerSection(*Sec);
200 if (Sec->getAlignment() < 4)
201 Sec->setAlignment(4);
202
203 new MCSymbolIdFragment(Symbol, getCurrentSectionOnly());
204
205 getAssembler().registerSymbol(*Symbol);
206 }
207
EmitCOFFSectionIndex(const MCSymbol * Symbol)208 void MCWinCOFFStreamer::EmitCOFFSectionIndex(const MCSymbol *Symbol) {
209 visitUsedSymbol(*Symbol);
210 MCDataFragment *DF = getOrCreateDataFragment();
211 const MCSymbolRefExpr *SRE = MCSymbolRefExpr::create(Symbol, getContext());
212 MCFixup Fixup = MCFixup::create(DF->getContents().size(), SRE, FK_SecRel_2);
213 DF->getFixups().push_back(Fixup);
214 DF->getContents().resize(DF->getContents().size() + 2, 0);
215 }
216
EmitCOFFSecRel32(const MCSymbol * Symbol,uint64_t Offset)217 void MCWinCOFFStreamer::EmitCOFFSecRel32(const MCSymbol *Symbol,
218 uint64_t Offset) {
219 visitUsedSymbol(*Symbol);
220 MCDataFragment *DF = getOrCreateDataFragment();
221 // Create Symbol A for the relocation relative reference.
222 const MCExpr *MCE = MCSymbolRefExpr::create(Symbol, getContext());
223 // Add the constant offset, if given.
224 if (Offset)
225 MCE = MCBinaryExpr::createAdd(
226 MCE, MCConstantExpr::create(Offset, getContext()), getContext());
227 // Build the secrel32 relocation.
228 MCFixup Fixup = MCFixup::create(DF->getContents().size(), MCE, FK_SecRel_4);
229 // Record the relocation.
230 DF->getFixups().push_back(Fixup);
231 // Emit 4 bytes (zeros) to the object file.
232 DF->getContents().resize(DF->getContents().size() + 4, 0);
233 }
234
EmitCOFFImgRel32(const MCSymbol * Symbol,int64_t Offset)235 void MCWinCOFFStreamer::EmitCOFFImgRel32(const MCSymbol *Symbol,
236 int64_t Offset) {
237 visitUsedSymbol(*Symbol);
238 MCDataFragment *DF = getOrCreateDataFragment();
239 // Create Symbol A for the relocation relative reference.
240 const MCExpr *MCE = MCSymbolRefExpr::create(
241 Symbol, MCSymbolRefExpr::VK_COFF_IMGREL32, getContext());
242 // Add the constant offset, if given.
243 if (Offset)
244 MCE = MCBinaryExpr::createAdd(
245 MCE, MCConstantExpr::create(Offset, getContext()), getContext());
246 // Build the imgrel relocation.
247 MCFixup Fixup = MCFixup::create(DF->getContents().size(), MCE, FK_Data_4);
248 // Record the relocation.
249 DF->getFixups().push_back(Fixup);
250 // Emit 4 bytes (zeros) to the object file.
251 DF->getContents().resize(DF->getContents().size() + 4, 0);
252 }
253
EmitCommonSymbol(MCSymbol * S,uint64_t Size,unsigned ByteAlignment)254 void MCWinCOFFStreamer::EmitCommonSymbol(MCSymbol *S, uint64_t Size,
255 unsigned ByteAlignment) {
256 auto *Symbol = cast<MCSymbolCOFF>(S);
257
258 const Triple &T = getContext().getObjectFileInfo()->getTargetTriple();
259 if (T.isKnownWindowsMSVCEnvironment()) {
260 if (ByteAlignment > 32)
261 report_fatal_error("alignment is limited to 32-bytes");
262
263 // Round size up to alignment so that we will honor the alignment request.
264 Size = std::max(Size, static_cast<uint64_t>(ByteAlignment));
265 }
266
267 getAssembler().registerSymbol(*Symbol);
268 Symbol->setExternal(true);
269 Symbol->setCommon(Size, ByteAlignment);
270
271 if (!T.isKnownWindowsMSVCEnvironment() && ByteAlignment > 1) {
272 SmallString<128> Directive;
273 raw_svector_ostream OS(Directive);
274 const MCObjectFileInfo *MFI = getContext().getObjectFileInfo();
275
276 OS << " -aligncomm:\"" << Symbol->getName() << "\","
277 << Log2_32_Ceil(ByteAlignment);
278
279 PushSection();
280 SwitchSection(MFI->getDrectveSection());
281 EmitBytes(Directive);
282 PopSection();
283 }
284 }
285
EmitLocalCommonSymbol(MCSymbol * S,uint64_t Size,unsigned ByteAlignment)286 void MCWinCOFFStreamer::EmitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
287 unsigned ByteAlignment) {
288 auto *Symbol = cast<MCSymbolCOFF>(S);
289
290 MCSection *Section = getContext().getObjectFileInfo()->getBSSSection();
291 PushSection();
292 SwitchSection(Section);
293 EmitValueToAlignment(ByteAlignment, 0, 1, 0);
294 EmitLabel(Symbol);
295 Symbol->setExternal(false);
296 EmitZeros(Size);
297 PopSection();
298 }
299
EmitZerofill(MCSection * Section,MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment,SMLoc Loc)300 void MCWinCOFFStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
301 uint64_t Size, unsigned ByteAlignment,
302 SMLoc Loc) {
303 llvm_unreachable("not implemented");
304 }
305
EmitTBSSSymbol(MCSection * Section,MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment)306 void MCWinCOFFStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
307 uint64_t Size, unsigned ByteAlignment) {
308 llvm_unreachable("not implemented");
309 }
310
311 // TODO: Implement this if you want to emit .comment section in COFF obj files.
EmitIdent(StringRef IdentString)312 void MCWinCOFFStreamer::EmitIdent(StringRef IdentString) {
313 llvm_unreachable("not implemented");
314 }
315
EmitWinEHHandlerData(SMLoc Loc)316 void MCWinCOFFStreamer::EmitWinEHHandlerData(SMLoc Loc) {
317 llvm_unreachable("not implemented");
318 }
319
FinishImpl()320 void MCWinCOFFStreamer::FinishImpl() {
321 MCObjectStreamer::FinishImpl();
322 }
323
Error(const Twine & Msg) const324 void MCWinCOFFStreamer::Error(const Twine &Msg) const {
325 getContext().reportError(SMLoc(), Msg);
326 }
327