1 //===-- llvm/MC/WinCOFFStreamer.cpp -----------------------------*- C++ -*-===//
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/StringExtras.h"
15 #include "llvm/MC/MCAsmBackend.h"
16 #include "llvm/MC/MCAsmLayout.h"
17 #include "llvm/MC/MCAssembler.h"
18 #include "llvm/MC/MCCodeEmitter.h"
19 #include "llvm/MC/MCContext.h"
20 #include "llvm/MC/MCExpr.h"
21 #include "llvm/MC/MCObjectFileInfo.h"
22 #include "llvm/MC/MCObjectStreamer.h"
23 #include "llvm/MC/MCSection.h"
24 #include "llvm/MC/MCSectionCOFF.h"
25 #include "llvm/MC/MCStreamer.h"
26 #include "llvm/MC/MCSymbol.h"
27 #include "llvm/MC/MCValue.h"
28 #include "llvm/MC/MCWinCOFFStreamer.h"
29 #include "llvm/Support/COFF.h"
30 #include "llvm/Support/Debug.h"
31 #include "llvm/Support/ErrorHandling.h"
32 #include "llvm/Support/MathExtras.h"
33 #include "llvm/Support/TargetRegistry.h"
34 #include "llvm/Support/raw_ostream.h"
35 
36 using namespace llvm;
37 
38 #define DEBUG_TYPE "WinCOFFStreamer"
39 
40 namespace llvm {
MCWinCOFFStreamer(MCContext & Context,MCAsmBackend & MAB,MCCodeEmitter & CE,raw_pwrite_stream & OS)41 MCWinCOFFStreamer::MCWinCOFFStreamer(MCContext &Context, MCAsmBackend &MAB,
42                                      MCCodeEmitter &CE, raw_pwrite_stream &OS)
43     : MCObjectStreamer(Context, MAB, OS, &CE), CurSymbol(nullptr) {}
44 
EmitInstToData(const MCInst & Inst,const MCSubtargetInfo & STI)45 void MCWinCOFFStreamer::EmitInstToData(const MCInst &Inst,
46                                        const MCSubtargetInfo &STI) {
47   MCDataFragment *DF = getOrCreateDataFragment();
48 
49   SmallVector<MCFixup, 4> Fixups;
50   SmallString<256> Code;
51   raw_svector_ostream VecOS(Code);
52   getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups, STI);
53   VecOS.flush();
54 
55   // Add the fixups and data.
56   for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
57     Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
58     DF->getFixups().push_back(Fixups[i]);
59   }
60 
61   DF->getContents().append(Code.begin(), Code.end());
62 }
63 
InitSections(bool NoExecStack)64 void MCWinCOFFStreamer::InitSections(bool NoExecStack) {
65   // FIXME: this is identical to the ELF one.
66   // This emulates the same behavior of GNU as. This makes it easier
67   // to compare the output as the major sections are in the same order.
68   SwitchSection(getContext().getObjectFileInfo()->getTextSection());
69   EmitCodeAlignment(4);
70 
71   SwitchSection(getContext().getObjectFileInfo()->getDataSection());
72   EmitCodeAlignment(4);
73 
74   SwitchSection(getContext().getObjectFileInfo()->getBSSSection());
75   EmitCodeAlignment(4);
76 
77   SwitchSection(getContext().getObjectFileInfo()->getTextSection());
78 }
79 
EmitLabel(MCSymbol * Symbol)80 void MCWinCOFFStreamer::EmitLabel(MCSymbol *Symbol) {
81   assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
82   MCObjectStreamer::EmitLabel(Symbol);
83 }
84 
EmitAssemblerFlag(MCAssemblerFlag Flag)85 void MCWinCOFFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
86   llvm_unreachable("not implemented");
87 }
88 
EmitThumbFunc(MCSymbol * Func)89 void MCWinCOFFStreamer::EmitThumbFunc(MCSymbol *Func) {
90   llvm_unreachable("not implemented");
91 }
92 
EmitSymbolAttribute(MCSymbol * Symbol,MCSymbolAttr Attribute)93 bool MCWinCOFFStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
94                                             MCSymbolAttr Attribute) {
95   assert(Symbol && "Symbol must be non-null!");
96   assert((!Symbol->isInSection() ||
97           Symbol->getSection().getVariant() == MCSection::SV_COFF) &&
98          "Got non-COFF section in the COFF backend!");
99 
100   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
101 
102   switch (Attribute) {
103   default: return false;
104   case MCSA_WeakReference:
105   case MCSA_Weak:
106     SD.modifyFlags(COFF::SF_WeakExternal, COFF::SF_WeakExternal);
107     SD.setExternal(true);
108     break;
109   case MCSA_Global:
110     SD.setExternal(true);
111     break;
112   }
113 
114   return true;
115 }
116 
EmitSymbolDesc(MCSymbol * Symbol,unsigned DescValue)117 void MCWinCOFFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
118   llvm_unreachable("not implemented");
119 }
120 
BeginCOFFSymbolDef(MCSymbol const * Symbol)121 void MCWinCOFFStreamer::BeginCOFFSymbolDef(MCSymbol const *Symbol) {
122   assert((!Symbol->isInSection() ||
123           Symbol->getSection().getVariant() == MCSection::SV_COFF) &&
124          "Got non-COFF section in the COFF backend!");
125 
126   if (CurSymbol)
127     FatalError("starting a new symbol definition without completing the "
128                "previous one");
129   CurSymbol = Symbol;
130 }
131 
EmitCOFFSymbolStorageClass(int StorageClass)132 void MCWinCOFFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
133   if (!CurSymbol)
134     FatalError("storage class specified outside of symbol definition");
135 
136   if (StorageClass & ~COFF::SSC_Invalid)
137     FatalError(Twine("storage class value '") + itostr(StorageClass) +
138                "' out of range");
139 
140   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*CurSymbol);
141   SD.modifyFlags(StorageClass << COFF::SF_ClassShift, COFF::SF_ClassMask);
142 }
143 
EmitCOFFSymbolType(int Type)144 void MCWinCOFFStreamer::EmitCOFFSymbolType(int Type) {
145   if (!CurSymbol)
146     FatalError("symbol type specified outside of a symbol definition");
147 
148   if (Type & ~0xffff)
149     FatalError(Twine("type value '") + itostr(Type) + "' out of range");
150 
151   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*CurSymbol);
152   SD.modifyFlags(Type << COFF::SF_TypeShift, COFF::SF_TypeMask);
153 }
154 
EndCOFFSymbolDef()155 void MCWinCOFFStreamer::EndCOFFSymbolDef() {
156   if (!CurSymbol)
157     FatalError("ending symbol definition without starting one");
158   CurSymbol = nullptr;
159 }
160 
EmitCOFFSectionIndex(MCSymbol const * Symbol)161 void MCWinCOFFStreamer::EmitCOFFSectionIndex(MCSymbol const *Symbol) {
162   MCDataFragment *DF = getOrCreateDataFragment();
163   const MCSymbolRefExpr *SRE = MCSymbolRefExpr::Create(Symbol, getContext());
164   MCFixup Fixup = MCFixup::Create(DF->getContents().size(), SRE, FK_SecRel_2);
165   DF->getFixups().push_back(Fixup);
166   DF->getContents().resize(DF->getContents().size() + 2, 0);
167 }
168 
EmitCOFFSecRel32(MCSymbol const * Symbol)169 void MCWinCOFFStreamer::EmitCOFFSecRel32(MCSymbol const *Symbol) {
170   MCDataFragment *DF = getOrCreateDataFragment();
171   const MCSymbolRefExpr *SRE = MCSymbolRefExpr::Create(Symbol, getContext());
172   MCFixup Fixup = MCFixup::Create(DF->getContents().size(), SRE, FK_SecRel_4);
173   DF->getFixups().push_back(Fixup);
174   DF->getContents().resize(DF->getContents().size() + 4, 0);
175 }
176 
EmitELFSize(MCSymbol * Symbol,const MCExpr * Value)177 void MCWinCOFFStreamer::EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
178   llvm_unreachable("not supported");
179 }
180 
EmitCommonSymbol(MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment)181 void MCWinCOFFStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
182                                          unsigned ByteAlignment) {
183   assert((!Symbol->isInSection() ||
184           Symbol->getSection().getVariant() == MCSection::SV_COFF) &&
185          "Got non-COFF section in the COFF backend!");
186 
187   const Triple &T = getContext().getObjectFileInfo()->getTargetTriple();
188   if (T.isKnownWindowsMSVCEnvironment()) {
189     if (ByteAlignment > 32)
190       report_fatal_error("alignment is limited to 32-bytes");
191 
192     // Round size up to alignment so that we will honor the alignment request.
193     Size = std::max(Size, static_cast<uint64_t>(ByteAlignment));
194   }
195 
196   AssignSection(Symbol, nullptr);
197 
198   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
199   SD.setExternal(true);
200   SD.setCommon(Size, ByteAlignment);
201 
202   if (!T.isKnownWindowsMSVCEnvironment() && ByteAlignment > 1) {
203     SmallString<128> Directive;
204     raw_svector_ostream OS(Directive);
205     const MCObjectFileInfo *MFI = getContext().getObjectFileInfo();
206 
207     OS << " -aligncomm:\"" << Symbol->getName() << "\","
208        << Log2_32_Ceil(ByteAlignment);
209     OS.flush();
210 
211     PushSection();
212     SwitchSection(MFI->getDrectveSection());
213     EmitBytes(Directive);
214     PopSection();
215   }
216 }
217 
EmitLocalCommonSymbol(MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment)218 void MCWinCOFFStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
219                                               unsigned ByteAlignment) {
220   assert(!Symbol->isInSection() && "Symbol must not already have a section!");
221 
222   const MCSection *Section = getContext().getObjectFileInfo()->getBSSSection();
223   MCSectionData &SectionData = getAssembler().getOrCreateSectionData(*Section);
224   if (SectionData.getAlignment() < ByteAlignment)
225     SectionData.setAlignment(ByteAlignment);
226 
227   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
228   SD.setExternal(false);
229 
230   AssignSection(Symbol, Section);
231 
232   if (ByteAlignment != 1)
233     new MCAlignFragment(ByteAlignment, /*Value=*/0, /*ValueSize=*/0,
234                         ByteAlignment, &SectionData);
235 
236   MCFillFragment *Fragment =
237       new MCFillFragment(/*Value=*/0, /*ValueSize=*/0, Size, &SectionData);
238   SD.setFragment(Fragment);
239 }
240 
EmitZerofill(const MCSection * Section,MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment)241 void MCWinCOFFStreamer::EmitZerofill(const MCSection *Section,
242                                      MCSymbol *Symbol, uint64_t Size,
243                                      unsigned ByteAlignment) {
244   llvm_unreachable("not implemented");
245 }
246 
EmitTBSSSymbol(const MCSection * Section,MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment)247 void MCWinCOFFStreamer::EmitTBSSSymbol(const MCSection *Section,
248                                        MCSymbol *Symbol, uint64_t Size,
249                                        unsigned ByteAlignment) {
250   llvm_unreachable("not implemented");
251 }
252 
EmitFileDirective(StringRef Filename)253 void MCWinCOFFStreamer::EmitFileDirective(StringRef Filename) {
254   getAssembler().addFileName(Filename);
255 }
256 
257 // TODO: Implement this if you want to emit .comment section in COFF obj files.
EmitIdent(StringRef IdentString)258 void MCWinCOFFStreamer::EmitIdent(StringRef IdentString) {
259   llvm_unreachable("not implemented");
260 }
261 
EmitWinEHHandlerData()262 void MCWinCOFFStreamer::EmitWinEHHandlerData() {
263   llvm_unreachable("not implemented");
264 }
265 
FinishImpl()266 void MCWinCOFFStreamer::FinishImpl() {
267   MCObjectStreamer::FinishImpl();
268 }
269 
270 LLVM_ATTRIBUTE_NORETURN
FatalError(const Twine & Msg) const271 void MCWinCOFFStreamer::FatalError(const Twine &Msg) const {
272   getContext().FatalError(SMLoc(), Msg);
273 }
274 }
275 
276