xref: /freebsd/contrib/llvm-project/llvm/lib/MC/MCWinCOFFStreamer.cpp (revision c66ec88fed842fbaad62c30d510644ceb7bd2d71) 
1 //===- llvm/MC/MCWinCOFFStreamer.cpp --------------------------------------===//
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 // This file contains an implementation of a Windows COFF object file streamer.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "llvm/ADT/SmallString.h"
14 #include "llvm/ADT/SmallVector.h"
15 #include "llvm/ADT/Triple.h"
16 #include "llvm/ADT/Twine.h"
17 #include "llvm/BinaryFormat/COFF.h"
18 #include "llvm/MC/MCAsmBackend.h"
19 #include "llvm/MC/MCAssembler.h"
20 #include "llvm/MC/MCCodeEmitter.h"
21 #include "llvm/MC/MCContext.h"
22 #include "llvm/MC/MCExpr.h"
23 #include "llvm/MC/MCFixup.h"
24 #include "llvm/MC/MCFragment.h"
25 #include "llvm/MC/MCObjectFileInfo.h"
26 #include "llvm/MC/MCObjectStreamer.h"
27 #include "llvm/MC/MCObjectWriter.h"
28 #include "llvm/MC/MCSection.h"
29 #include "llvm/MC/MCSymbolCOFF.h"
30 #include "llvm/MC/MCWinCOFFStreamer.h"
31 #include "llvm/Support/Casting.h"
32 #include "llvm/Support/ErrorHandling.h"
33 #include "llvm/Support/MathExtras.h"
34 #include "llvm/Support/SMLoc.h"
35 #include "llvm/Support/raw_ostream.h"
36 #include <algorithm>
37 #include <cassert>
38 #include <cstdint>
39 
40 using namespace llvm;
41 
42 #define DEBUG_TYPE "WinCOFFStreamer"
43 
44 MCWinCOFFStreamer::MCWinCOFFStreamer(MCContext &Context,
45                                      std::unique_ptr<MCAsmBackend> MAB,
46                                      std::unique_ptr<MCCodeEmitter> CE,
47                                      std::unique_ptr<MCObjectWriter> OW)
48     : MCObjectStreamer(Context, std::move(MAB), std::move(OW), std::move(CE)),
49       CurSymbol(nullptr) {}
50 
51 void MCWinCOFFStreamer::emitInstToData(const MCInst &Inst,
52                                        const MCSubtargetInfo &STI) {
53   MCDataFragment *DF = getOrCreateDataFragment();
54 
55   SmallVector<MCFixup, 4> Fixups;
56   SmallString<256> Code;
57   raw_svector_ostream VecOS(Code);
58   getAssembler().getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
59 
60   // Add the fixups and data.
61   for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
62     Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
63     DF->getFixups().push_back(Fixups[i]);
64   }
65   DF->setHasInstructions(STI);
66   DF->getContents().append(Code.begin(), Code.end());
67 }
68 
69 void MCWinCOFFStreamer::InitSections(bool NoExecStack) {
70   // FIXME: this is identical to the ELF one.
71   // This emulates the same behavior of GNU as. This makes it easier
72   // to compare the output as the major sections are in the same order.
73   SwitchSection(getContext().getObjectFileInfo()->getTextSection());
74   emitCodeAlignment(4);
75 
76   SwitchSection(getContext().getObjectFileInfo()->getDataSection());
77   emitCodeAlignment(4);
78 
79   SwitchSection(getContext().getObjectFileInfo()->getBSSSection());
80   emitCodeAlignment(4);
81 
82   SwitchSection(getContext().getObjectFileInfo()->getTextSection());
83 }
84 
85 void MCWinCOFFStreamer::emitLabel(MCSymbol *S, SMLoc Loc) {
86   auto *Symbol = cast<MCSymbolCOFF>(S);
87   MCObjectStreamer::emitLabel(Symbol, Loc);
88 }
89 
90 void MCWinCOFFStreamer::emitAssemblerFlag(MCAssemblerFlag Flag) {
91   // Let the target do whatever target specific stuff it needs to do.
92   getAssembler().getBackend().handleAssemblerFlag(Flag);
93 
94   switch (Flag) {
95   // None of these require COFF specific handling.
96   case MCAF_SyntaxUnified:
97   case MCAF_Code16:
98   case MCAF_Code32:
99   case MCAF_Code64:
100     break;
101   case MCAF_SubsectionsViaSymbols:
102     llvm_unreachable("COFF doesn't support .subsections_via_symbols");
103   }
104 }
105 
106 void MCWinCOFFStreamer::emitThumbFunc(MCSymbol *Func) {
107   llvm_unreachable("not implemented");
108 }
109 
110 bool MCWinCOFFStreamer::emitSymbolAttribute(MCSymbol *S,
111                                             MCSymbolAttr Attribute) {
112   auto *Symbol = cast<MCSymbolCOFF>(S);
113   getAssembler().registerSymbol(*Symbol);
114 
115   switch (Attribute) {
116   default: return false;
117   case MCSA_WeakReference:
118   case MCSA_Weak:
119     Symbol->setIsWeakExternal();
120     Symbol->setExternal(true);
121     break;
122   case MCSA_Global:
123     Symbol->setExternal(true);
124     break;
125   case MCSA_AltEntry:
126     llvm_unreachable("COFF doesn't support the .alt_entry attribute");
127   }
128 
129   return true;
130 }
131 
132 void MCWinCOFFStreamer::emitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
133   llvm_unreachable("not implemented");
134 }
135 
136 void MCWinCOFFStreamer::BeginCOFFSymbolDef(MCSymbol const *S) {
137   auto *Symbol = cast<MCSymbolCOFF>(S);
138   if (CurSymbol)
139     Error("starting a new symbol definition without completing the "
140           "previous one");
141   CurSymbol = Symbol;
142 }
143 
144 void MCWinCOFFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
145   if (!CurSymbol) {
146     Error("storage class specified outside of symbol definition");
147     return;
148   }
149 
150   if (StorageClass & ~COFF::SSC_Invalid) {
151     Error("storage class value '" + Twine(StorageClass) +
152                "' out of range");
153     return;
154   }
155 
156   getAssembler().registerSymbol(*CurSymbol);
157   cast<MCSymbolCOFF>(CurSymbol)->setClass((uint16_t)StorageClass);
158 }
159 
160 void MCWinCOFFStreamer::EmitCOFFSymbolType(int Type) {
161   if (!CurSymbol) {
162     Error("symbol type specified outside of a symbol definition");
163     return;
164   }
165 
166   if (Type & ~0xffff) {
167     Error("type value '" + Twine(Type) + "' out of range");
168     return;
169   }
170 
171   getAssembler().registerSymbol(*CurSymbol);
172   cast<MCSymbolCOFF>(CurSymbol)->setType((uint16_t)Type);
173 }
174 
175 void MCWinCOFFStreamer::EndCOFFSymbolDef() {
176   if (!CurSymbol)
177     Error("ending symbol definition without starting one");
178   CurSymbol = nullptr;
179 }
180 
181 void MCWinCOFFStreamer::EmitCOFFSafeSEH(MCSymbol const *Symbol) {
182   // SafeSEH is a feature specific to 32-bit x86.  It does not exist (and is
183   // unnecessary) on all platforms which use table-based exception dispatch.
184   if (getContext().getObjectFileInfo()->getTargetTriple().getArch() !=
185       Triple::x86)
186     return;
187 
188   const MCSymbolCOFF *CSymbol = cast<MCSymbolCOFF>(Symbol);
189   if (CSymbol->isSafeSEH())
190     return;
191 
192   MCSection *SXData = getContext().getObjectFileInfo()->getSXDataSection();
193   getAssembler().registerSection(*SXData);
194   if (SXData->getAlignment() < 4)
195     SXData->setAlignment(Align(4));
196 
197   new MCSymbolIdFragment(Symbol, SXData);
198 
199   getAssembler().registerSymbol(*Symbol);
200   CSymbol->setIsSafeSEH();
201 
202   // The Microsoft linker requires that the symbol type of a handler be
203   // function. Go ahead and oblige it here.
204   CSymbol->setType(COFF::IMAGE_SYM_DTYPE_FUNCTION
205                    << COFF::SCT_COMPLEX_TYPE_SHIFT);
206 }
207 
208 void MCWinCOFFStreamer::EmitCOFFSymbolIndex(MCSymbol const *Symbol) {
209   MCSection *Sec = getCurrentSectionOnly();
210   getAssembler().registerSection(*Sec);
211   if (Sec->getAlignment() < 4)
212     Sec->setAlignment(Align(4));
213 
214   new MCSymbolIdFragment(Symbol, getCurrentSectionOnly());
215 
216   getAssembler().registerSymbol(*Symbol);
217 }
218 
219 void MCWinCOFFStreamer::EmitCOFFSectionIndex(const MCSymbol *Symbol) {
220   visitUsedSymbol(*Symbol);
221   MCDataFragment *DF = getOrCreateDataFragment();
222   const MCSymbolRefExpr *SRE = MCSymbolRefExpr::create(Symbol, getContext());
223   MCFixup Fixup = MCFixup::create(DF->getContents().size(), SRE, FK_SecRel_2);
224   DF->getFixups().push_back(Fixup);
225   DF->getContents().resize(DF->getContents().size() + 2, 0);
226 }
227 
228 void MCWinCOFFStreamer::EmitCOFFSecRel32(const MCSymbol *Symbol,
229                                          uint64_t Offset) {
230   visitUsedSymbol(*Symbol);
231   MCDataFragment *DF = getOrCreateDataFragment();
232   // Create Symbol A for the relocation relative reference.
233   const MCExpr *MCE = MCSymbolRefExpr::create(Symbol, getContext());
234   // Add the constant offset, if given.
235   if (Offset)
236     MCE = MCBinaryExpr::createAdd(
237         MCE, MCConstantExpr::create(Offset, getContext()), getContext());
238   // Build the secrel32 relocation.
239   MCFixup Fixup = MCFixup::create(DF->getContents().size(), MCE, FK_SecRel_4);
240   // Record the relocation.
241   DF->getFixups().push_back(Fixup);
242   // Emit 4 bytes (zeros) to the object file.
243   DF->getContents().resize(DF->getContents().size() + 4, 0);
244 }
245 
246 void MCWinCOFFStreamer::EmitCOFFImgRel32(const MCSymbol *Symbol,
247                                          int64_t Offset) {
248   visitUsedSymbol(*Symbol);
249   MCDataFragment *DF = getOrCreateDataFragment();
250   // Create Symbol A for the relocation relative reference.
251   const MCExpr *MCE = MCSymbolRefExpr::create(
252       Symbol, MCSymbolRefExpr::VK_COFF_IMGREL32, getContext());
253   // Add the constant offset, if given.
254   if (Offset)
255     MCE = MCBinaryExpr::createAdd(
256         MCE, MCConstantExpr::create(Offset, getContext()), getContext());
257   // Build the imgrel relocation.
258   MCFixup Fixup = MCFixup::create(DF->getContents().size(), MCE, FK_Data_4);
259   // Record the relocation.
260   DF->getFixups().push_back(Fixup);
261   // Emit 4 bytes (zeros) to the object file.
262   DF->getContents().resize(DF->getContents().size() + 4, 0);
263 }
264 
265 void MCWinCOFFStreamer::emitCommonSymbol(MCSymbol *S, uint64_t Size,
266                                          unsigned ByteAlignment) {
267   auto *Symbol = cast<MCSymbolCOFF>(S);
268 
269   const Triple &T = getContext().getObjectFileInfo()->getTargetTriple();
270   if (T.isWindowsMSVCEnvironment()) {
271     if (ByteAlignment > 32)
272       report_fatal_error("alignment is limited to 32-bytes");
273 
274     // Round size up to alignment so that we will honor the alignment request.
275     Size = std::max(Size, static_cast<uint64_t>(ByteAlignment));
276   }
277 
278   getAssembler().registerSymbol(*Symbol);
279   Symbol->setExternal(true);
280   Symbol->setCommon(Size, ByteAlignment);
281 
282   if (!T.isWindowsMSVCEnvironment() && ByteAlignment > 1) {
283     SmallString<128> Directive;
284     raw_svector_ostream OS(Directive);
285     const MCObjectFileInfo *MFI = getContext().getObjectFileInfo();
286 
287     OS << " -aligncomm:\"" << Symbol->getName() << "\","
288        << Log2_32_Ceil(ByteAlignment);
289 
290     PushSection();
291     SwitchSection(MFI->getDrectveSection());
292     emitBytes(Directive);
293     PopSection();
294   }
295 }
296 
297 void MCWinCOFFStreamer::emitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
298                                               unsigned ByteAlignment) {
299   auto *Symbol = cast<MCSymbolCOFF>(S);
300 
301   MCSection *Section = getContext().getObjectFileInfo()->getBSSSection();
302   PushSection();
303   SwitchSection(Section);
304   emitValueToAlignment(ByteAlignment, 0, 1, 0);
305   emitLabel(Symbol);
306   Symbol->setExternal(false);
307   emitZeros(Size);
308   PopSection();
309 }
310 
311 void MCWinCOFFStreamer::emitZerofill(MCSection *Section, MCSymbol *Symbol,
312                                      uint64_t Size, unsigned ByteAlignment,
313                                      SMLoc Loc) {
314   llvm_unreachable("not implemented");
315 }
316 
317 void MCWinCOFFStreamer::emitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
318                                        uint64_t Size, unsigned ByteAlignment) {
319   llvm_unreachable("not implemented");
320 }
321 
322 // TODO: Implement this if you want to emit .comment section in COFF obj files.
323 void MCWinCOFFStreamer::emitIdent(StringRef IdentString) {
324   llvm_unreachable("not implemented");
325 }
326 
327 void MCWinCOFFStreamer::EmitWinEHHandlerData(SMLoc Loc) {
328   llvm_unreachable("not implemented");
329 }
330 
331 void MCWinCOFFStreamer::emitCGProfileEntry(const MCSymbolRefExpr *From,
332                                            const MCSymbolRefExpr *To,
333                                            uint64_t Count) {
334   // Ignore temporary symbols for now.
335   if (!From->getSymbol().isTemporary() && !To->getSymbol().isTemporary())
336     getAssembler().CGProfile.push_back({From, To, Count});
337 }
338 
339 void MCWinCOFFStreamer::finalizeCGProfileEntry(const MCSymbolRefExpr *&SRE) {
340   const MCSymbol *S = &SRE->getSymbol();
341   bool Created;
342   getAssembler().registerSymbol(*S, &Created);
343   if (Created) {
344     cast<MCSymbolCOFF>(S)->setIsWeakExternal();
345     cast<MCSymbolCOFF>(S)->setExternal(true);
346   }
347 }
348 
349 void MCWinCOFFStreamer::finalizeCGProfile() {
350   for (MCAssembler::CGProfileEntry &E : getAssembler().CGProfile) {
351     finalizeCGProfileEntry(E.From);
352     finalizeCGProfileEntry(E.To);
353   }
354 }
355 
356 void MCWinCOFFStreamer::finishImpl() {
357   finalizeCGProfile();
358 
359   MCObjectStreamer::finishImpl();
360 }
361 
362 void MCWinCOFFStreamer::Error(const Twine &Msg) const {
363   getContext().reportError(SMLoc(), Msg);
364 }
365