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