1 //===- lib/MC/MCDwarf.cpp - MCDwarf implementation ------------------------===//
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 "llvm/MC/MCDwarf.h"
10 #include "llvm/ADT/ArrayRef.h"
11 #include "llvm/ADT/DenseMap.h"
12 #include "llvm/ADT/Hashing.h"
13 #include "llvm/ADT/STLExtras.h"
14 #include "llvm/ADT/SmallString.h"
15 #include "llvm/ADT/SmallVector.h"
16 #include "llvm/ADT/StringRef.h"
17 #include "llvm/ADT/Twine.h"
18 #include "llvm/BinaryFormat/Dwarf.h"
19 #include "llvm/Config/config.h"
20 #include "llvm/MC/MCAsmInfo.h"
21 #include "llvm/MC/MCContext.h"
22 #include "llvm/MC/MCExpr.h"
23 #include "llvm/MC/MCObjectFileInfo.h"
24 #include "llvm/MC/MCObjectStreamer.h"
25 #include "llvm/MC/MCRegisterInfo.h"
26 #include "llvm/MC/MCSection.h"
27 #include "llvm/MC/MCStreamer.h"
28 #include "llvm/MC/MCSymbol.h"
29 #include "llvm/Support/Casting.h"
30 #include "llvm/Support/Endian.h"
31 #include "llvm/Support/EndianStream.h"
32 #include "llvm/Support/ErrorHandling.h"
33 #include "llvm/Support/LEB128.h"
34 #include "llvm/Support/MathExtras.h"
35 #include "llvm/Support/Path.h"
36 #include "llvm/Support/SourceMgr.h"
37 #include "llvm/Support/raw_ostream.h"
38 #include <cassert>
39 #include <cstdint>
40 #include <optional>
41 #include <string>
42 #include <utility>
43 #include <vector>
44
45 using namespace llvm;
46
emitListsTableHeaderStart(MCStreamer & S)47 MCSymbol *mcdwarf::emitListsTableHeaderStart(MCStreamer &S) {
48 MCSymbol *Start = S.getContext().createTempSymbol("debug_list_header_start");
49 MCSymbol *End = S.getContext().createTempSymbol("debug_list_header_end");
50 auto DwarfFormat = S.getContext().getDwarfFormat();
51 if (DwarfFormat == dwarf::DWARF64) {
52 S.AddComment("DWARF64 mark");
53 S.emitInt32(dwarf::DW_LENGTH_DWARF64);
54 }
55 S.AddComment("Length");
56 S.emitAbsoluteSymbolDiff(End, Start,
57 dwarf::getDwarfOffsetByteSize(DwarfFormat));
58 S.emitLabel(Start);
59 S.AddComment("Version");
60 S.emitInt16(S.getContext().getDwarfVersion());
61 S.AddComment("Address size");
62 S.emitInt8(S.getContext().getAsmInfo()->getCodePointerSize());
63 S.AddComment("Segment selector size");
64 S.emitInt8(0);
65 return End;
66 }
67
ScaleAddrDelta(MCContext & Context,uint64_t AddrDelta)68 static inline uint64_t ScaleAddrDelta(MCContext &Context, uint64_t AddrDelta) {
69 unsigned MinInsnLength = Context.getAsmInfo()->getMinInstAlignment();
70 if (MinInsnLength == 1)
71 return AddrDelta;
72 if (AddrDelta % MinInsnLength != 0) {
73 // TODO: report this error, but really only once.
74 ;
75 }
76 return AddrDelta / MinInsnLength;
77 }
78
MCDwarfLineStr(MCContext & Ctx)79 MCDwarfLineStr::MCDwarfLineStr(MCContext &Ctx) {
80 UseRelocs = Ctx.getAsmInfo()->doesDwarfUseRelocationsAcrossSections();
81 if (UseRelocs) {
82 MCSection *DwarfLineStrSection =
83 Ctx.getObjectFileInfo()->getDwarfLineStrSection();
84 assert(DwarfLineStrSection && "DwarfLineStrSection must not be NULL");
85 LineStrLabel = DwarfLineStrSection->getBeginSymbol();
86 }
87 }
88
89 //
90 // This is called when an instruction is assembled into the specified section
91 // and if there is information from the last .loc directive that has yet to have
92 // a line entry made for it is made.
93 //
make(MCStreamer * MCOS,MCSection * Section)94 void MCDwarfLineEntry::make(MCStreamer *MCOS, MCSection *Section) {
95 if (!MCOS->getContext().getDwarfLocSeen())
96 return;
97
98 // Create a symbol at in the current section for use in the line entry.
99 MCSymbol *LineSym = MCOS->getContext().createTempSymbol();
100 // Set the value of the symbol to use for the MCDwarfLineEntry.
101 MCOS->emitLabel(LineSym);
102
103 // Get the current .loc info saved in the context.
104 const MCDwarfLoc &DwarfLoc = MCOS->getContext().getCurrentDwarfLoc();
105
106 // Create a (local) line entry with the symbol and the current .loc info.
107 MCDwarfLineEntry LineEntry(LineSym, DwarfLoc);
108
109 // clear DwarfLocSeen saying the current .loc info is now used.
110 MCOS->getContext().clearDwarfLocSeen();
111
112 // Add the line entry to this section's entries.
113 MCOS->getContext()
114 .getMCDwarfLineTable(MCOS->getContext().getDwarfCompileUnitID())
115 .getMCLineSections()
116 .addLineEntry(LineEntry, Section);
117 }
118
119 //
120 // This helper routine returns an expression of End - Start - IntVal .
121 //
makeEndMinusStartExpr(MCContext & Ctx,const MCSymbol & Start,const MCSymbol & End,int IntVal)122 static inline const MCExpr *makeEndMinusStartExpr(MCContext &Ctx,
123 const MCSymbol &Start,
124 const MCSymbol &End,
125 int IntVal) {
126 MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
127 const MCExpr *Res = MCSymbolRefExpr::create(&End, Variant, Ctx);
128 const MCExpr *RHS = MCSymbolRefExpr::create(&Start, Variant, Ctx);
129 const MCExpr *Res1 = MCBinaryExpr::create(MCBinaryExpr::Sub, Res, RHS, Ctx);
130 const MCExpr *Res2 = MCConstantExpr::create(IntVal, Ctx);
131 const MCExpr *Res3 = MCBinaryExpr::create(MCBinaryExpr::Sub, Res1, Res2, Ctx);
132 return Res3;
133 }
134
135 //
136 // This helper routine returns an expression of Start + IntVal .
137 //
138 static inline const MCExpr *
makeStartPlusIntExpr(MCContext & Ctx,const MCSymbol & Start,int IntVal)139 makeStartPlusIntExpr(MCContext &Ctx, const MCSymbol &Start, int IntVal) {
140 MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
141 const MCExpr *LHS = MCSymbolRefExpr::create(&Start, Variant, Ctx);
142 const MCExpr *RHS = MCConstantExpr::create(IntVal, Ctx);
143 const MCExpr *Res = MCBinaryExpr::create(MCBinaryExpr::Add, LHS, RHS, Ctx);
144 return Res;
145 }
146
addEndEntry(MCSymbol * EndLabel)147 void MCLineSection::addEndEntry(MCSymbol *EndLabel) {
148 auto *Sec = &EndLabel->getSection();
149 // The line table may be empty, which we should skip adding an end entry.
150 // There are two cases:
151 // (1) MCAsmStreamer - emitDwarfLocDirective emits a location directive in
152 // place instead of adding a line entry if the target has
153 // usesDwarfFileAndLocDirectives.
154 // (2) MCObjectStreamer - if a function has incomplete debug info where
155 // instructions don't have DILocations, the line entries are missing.
156 auto I = MCLineDivisions.find(Sec);
157 if (I != MCLineDivisions.end()) {
158 auto &Entries = I->second;
159 auto EndEntry = Entries.back();
160 EndEntry.setEndLabel(EndLabel);
161 Entries.push_back(EndEntry);
162 }
163 }
164
165 //
166 // This emits the Dwarf line table for the specified section from the entries
167 // in the LineSection.
168 //
emitOne(MCStreamer * MCOS,MCSection * Section,const MCLineSection::MCDwarfLineEntryCollection & LineEntries)169 void MCDwarfLineTable::emitOne(
170 MCStreamer *MCOS, MCSection *Section,
171 const MCLineSection::MCDwarfLineEntryCollection &LineEntries) {
172
173 unsigned FileNum, LastLine, Column, Flags, Isa, Discriminator;
174 MCSymbol *LastLabel;
175 auto init = [&]() {
176 FileNum = 1;
177 LastLine = 1;
178 Column = 0;
179 Flags = DWARF2_LINE_DEFAULT_IS_STMT ? DWARF2_FLAG_IS_STMT : 0;
180 Isa = 0;
181 Discriminator = 0;
182 LastLabel = nullptr;
183 };
184 init();
185
186 // Loop through each MCDwarfLineEntry and encode the dwarf line number table.
187 bool EndEntryEmitted = false;
188 for (const MCDwarfLineEntry &LineEntry : LineEntries) {
189 MCSymbol *Label = LineEntry.getLabel();
190 const MCAsmInfo *asmInfo = MCOS->getContext().getAsmInfo();
191 if (LineEntry.IsEndEntry) {
192 MCOS->emitDwarfAdvanceLineAddr(INT64_MAX, LastLabel, Label,
193 asmInfo->getCodePointerSize());
194 init();
195 EndEntryEmitted = true;
196 continue;
197 }
198
199 int64_t LineDelta = static_cast<int64_t>(LineEntry.getLine()) - LastLine;
200
201 if (FileNum != LineEntry.getFileNum()) {
202 FileNum = LineEntry.getFileNum();
203 MCOS->emitInt8(dwarf::DW_LNS_set_file);
204 MCOS->emitULEB128IntValue(FileNum);
205 }
206 if (Column != LineEntry.getColumn()) {
207 Column = LineEntry.getColumn();
208 MCOS->emitInt8(dwarf::DW_LNS_set_column);
209 MCOS->emitULEB128IntValue(Column);
210 }
211 if (Discriminator != LineEntry.getDiscriminator() &&
212 MCOS->getContext().getDwarfVersion() >= 4) {
213 Discriminator = LineEntry.getDiscriminator();
214 unsigned Size = getULEB128Size(Discriminator);
215 MCOS->emitInt8(dwarf::DW_LNS_extended_op);
216 MCOS->emitULEB128IntValue(Size + 1);
217 MCOS->emitInt8(dwarf::DW_LNE_set_discriminator);
218 MCOS->emitULEB128IntValue(Discriminator);
219 }
220 if (Isa != LineEntry.getIsa()) {
221 Isa = LineEntry.getIsa();
222 MCOS->emitInt8(dwarf::DW_LNS_set_isa);
223 MCOS->emitULEB128IntValue(Isa);
224 }
225 if ((LineEntry.getFlags() ^ Flags) & DWARF2_FLAG_IS_STMT) {
226 Flags = LineEntry.getFlags();
227 MCOS->emitInt8(dwarf::DW_LNS_negate_stmt);
228 }
229 if (LineEntry.getFlags() & DWARF2_FLAG_BASIC_BLOCK)
230 MCOS->emitInt8(dwarf::DW_LNS_set_basic_block);
231 if (LineEntry.getFlags() & DWARF2_FLAG_PROLOGUE_END)
232 MCOS->emitInt8(dwarf::DW_LNS_set_prologue_end);
233 if (LineEntry.getFlags() & DWARF2_FLAG_EPILOGUE_BEGIN)
234 MCOS->emitInt8(dwarf::DW_LNS_set_epilogue_begin);
235
236 // At this point we want to emit/create the sequence to encode the delta in
237 // line numbers and the increment of the address from the previous Label
238 // and the current Label.
239 MCOS->emitDwarfAdvanceLineAddr(LineDelta, LastLabel, Label,
240 asmInfo->getCodePointerSize());
241
242 Discriminator = 0;
243 LastLine = LineEntry.getLine();
244 LastLabel = Label;
245 }
246
247 // Generate DWARF line end entry.
248 // We do not need this for DwarfDebug that explicitly terminates the line
249 // table using ranges whenever CU or section changes. However, the MC path
250 // does not track ranges nor terminate the line table. In that case,
251 // conservatively use the section end symbol to end the line table.
252 if (!EndEntryEmitted)
253 MCOS->emitDwarfLineEndEntry(Section, LastLabel);
254 }
255
256 //
257 // This emits the Dwarf file and the line tables.
258 //
emit(MCStreamer * MCOS,MCDwarfLineTableParams Params)259 void MCDwarfLineTable::emit(MCStreamer *MCOS, MCDwarfLineTableParams Params) {
260 MCContext &context = MCOS->getContext();
261
262 auto &LineTables = context.getMCDwarfLineTables();
263
264 // Bail out early so we don't switch to the debug_line section needlessly and
265 // in doing so create an unnecessary (if empty) section.
266 if (LineTables.empty())
267 return;
268
269 // In a v5 non-split line table, put the strings in a separate section.
270 std::optional<MCDwarfLineStr> LineStr;
271 if (context.getDwarfVersion() >= 5)
272 LineStr.emplace(context);
273
274 // Switch to the section where the table will be emitted into.
275 MCOS->switchSection(context.getObjectFileInfo()->getDwarfLineSection());
276
277 // Handle the rest of the Compile Units.
278 for (const auto &CUIDTablePair : LineTables) {
279 CUIDTablePair.second.emitCU(MCOS, Params, LineStr);
280 }
281
282 if (LineStr)
283 LineStr->emitSection(MCOS);
284 }
285
Emit(MCStreamer & MCOS,MCDwarfLineTableParams Params,MCSection * Section) const286 void MCDwarfDwoLineTable::Emit(MCStreamer &MCOS, MCDwarfLineTableParams Params,
287 MCSection *Section) const {
288 if (!HasSplitLineTable)
289 return;
290 std::optional<MCDwarfLineStr> NoLineStr(std::nullopt);
291 MCOS.switchSection(Section);
292 MCOS.emitLabel(Header.Emit(&MCOS, Params, std::nullopt, NoLineStr).second);
293 }
294
295 std::pair<MCSymbol *, MCSymbol *>
Emit(MCStreamer * MCOS,MCDwarfLineTableParams Params,std::optional<MCDwarfLineStr> & LineStr) const296 MCDwarfLineTableHeader::Emit(MCStreamer *MCOS, MCDwarfLineTableParams Params,
297 std::optional<MCDwarfLineStr> &LineStr) const {
298 static const char StandardOpcodeLengths[] = {
299 0, // length of DW_LNS_copy
300 1, // length of DW_LNS_advance_pc
301 1, // length of DW_LNS_advance_line
302 1, // length of DW_LNS_set_file
303 1, // length of DW_LNS_set_column
304 0, // length of DW_LNS_negate_stmt
305 0, // length of DW_LNS_set_basic_block
306 0, // length of DW_LNS_const_add_pc
307 1, // length of DW_LNS_fixed_advance_pc
308 0, // length of DW_LNS_set_prologue_end
309 0, // length of DW_LNS_set_epilogue_begin
310 1 // DW_LNS_set_isa
311 };
312 assert(std::size(StandardOpcodeLengths) >=
313 (Params.DWARF2LineOpcodeBase - 1U));
314 return Emit(MCOS, Params,
315 ArrayRef(StandardOpcodeLengths, Params.DWARF2LineOpcodeBase - 1),
316 LineStr);
317 }
318
forceExpAbs(MCStreamer & OS,const MCExpr * Expr)319 static const MCExpr *forceExpAbs(MCStreamer &OS, const MCExpr* Expr) {
320 MCContext &Context = OS.getContext();
321 assert(!isa<MCSymbolRefExpr>(Expr));
322 if (Context.getAsmInfo()->hasAggressiveSymbolFolding())
323 return Expr;
324
325 MCSymbol *ABS = Context.createTempSymbol();
326 OS.emitAssignment(ABS, Expr);
327 return MCSymbolRefExpr::create(ABS, Context);
328 }
329
emitAbsValue(MCStreamer & OS,const MCExpr * Value,unsigned Size)330 static void emitAbsValue(MCStreamer &OS, const MCExpr *Value, unsigned Size) {
331 const MCExpr *ABS = forceExpAbs(OS, Value);
332 OS.emitValue(ABS, Size);
333 }
334
emitSection(MCStreamer * MCOS)335 void MCDwarfLineStr::emitSection(MCStreamer *MCOS) {
336 // Switch to the .debug_line_str section.
337 MCOS->switchSection(
338 MCOS->getContext().getObjectFileInfo()->getDwarfLineStrSection());
339 SmallString<0> Data = getFinalizedData();
340 MCOS->emitBinaryData(Data.str());
341 }
342
getFinalizedData()343 SmallString<0> MCDwarfLineStr::getFinalizedData() {
344 // Emit the strings without perturbing the offsets we used.
345 if (!LineStrings.isFinalized())
346 LineStrings.finalizeInOrder();
347 SmallString<0> Data;
348 Data.resize(LineStrings.getSize());
349 LineStrings.write((uint8_t *)Data.data());
350 return Data;
351 }
352
addString(StringRef Path)353 size_t MCDwarfLineStr::addString(StringRef Path) {
354 return LineStrings.add(Path);
355 }
356
emitRef(MCStreamer * MCOS,StringRef Path)357 void MCDwarfLineStr::emitRef(MCStreamer *MCOS, StringRef Path) {
358 int RefSize =
359 dwarf::getDwarfOffsetByteSize(MCOS->getContext().getDwarfFormat());
360 size_t Offset = addString(Path);
361 if (UseRelocs) {
362 MCContext &Ctx = MCOS->getContext();
363 MCOS->emitValue(makeStartPlusIntExpr(Ctx, *LineStrLabel, Offset), RefSize);
364 } else
365 MCOS->emitIntValue(Offset, RefSize);
366 }
367
emitV2FileDirTables(MCStreamer * MCOS) const368 void MCDwarfLineTableHeader::emitV2FileDirTables(MCStreamer *MCOS) const {
369 // First the directory table.
370 for (auto &Dir : MCDwarfDirs) {
371 MCOS->emitBytes(Dir); // The DirectoryName, and...
372 MCOS->emitBytes(StringRef("\0", 1)); // its null terminator.
373 }
374 MCOS->emitInt8(0); // Terminate the directory list.
375
376 // Second the file table.
377 for (unsigned i = 1; i < MCDwarfFiles.size(); i++) {
378 assert(!MCDwarfFiles[i].Name.empty());
379 MCOS->emitBytes(MCDwarfFiles[i].Name); // FileName and...
380 MCOS->emitBytes(StringRef("\0", 1)); // its null terminator.
381 MCOS->emitULEB128IntValue(MCDwarfFiles[i].DirIndex); // Directory number.
382 MCOS->emitInt8(0); // Last modification timestamp (always 0).
383 MCOS->emitInt8(0); // File size (always 0).
384 }
385 MCOS->emitInt8(0); // Terminate the file list.
386 }
387
emitOneV5FileEntry(MCStreamer * MCOS,const MCDwarfFile & DwarfFile,bool EmitMD5,bool HasAnySource,std::optional<MCDwarfLineStr> & LineStr)388 static void emitOneV5FileEntry(MCStreamer *MCOS, const MCDwarfFile &DwarfFile,
389 bool EmitMD5, bool HasAnySource,
390 std::optional<MCDwarfLineStr> &LineStr) {
391 assert(!DwarfFile.Name.empty());
392 if (LineStr)
393 LineStr->emitRef(MCOS, DwarfFile.Name);
394 else {
395 MCOS->emitBytes(DwarfFile.Name); // FileName and...
396 MCOS->emitBytes(StringRef("\0", 1)); // its null terminator.
397 }
398 MCOS->emitULEB128IntValue(DwarfFile.DirIndex); // Directory number.
399 if (EmitMD5) {
400 const MD5::MD5Result &Cksum = *DwarfFile.Checksum;
401 MCOS->emitBinaryData(
402 StringRef(reinterpret_cast<const char *>(Cksum.data()), Cksum.size()));
403 }
404 if (HasAnySource) {
405 if (LineStr)
406 LineStr->emitRef(MCOS, DwarfFile.Source.value_or(StringRef()));
407 else {
408 MCOS->emitBytes(DwarfFile.Source.value_or(StringRef())); // Source and...
409 MCOS->emitBytes(StringRef("\0", 1)); // its null terminator.
410 }
411 }
412 }
413
emitV5FileDirTables(MCStreamer * MCOS,std::optional<MCDwarfLineStr> & LineStr) const414 void MCDwarfLineTableHeader::emitV5FileDirTables(
415 MCStreamer *MCOS, std::optional<MCDwarfLineStr> &LineStr) const {
416 // The directory format, which is just a list of the directory paths. In a
417 // non-split object, these are references to .debug_line_str; in a split
418 // object, they are inline strings.
419 MCOS->emitInt8(1);
420 MCOS->emitULEB128IntValue(dwarf::DW_LNCT_path);
421 MCOS->emitULEB128IntValue(LineStr ? dwarf::DW_FORM_line_strp
422 : dwarf::DW_FORM_string);
423 MCOS->emitULEB128IntValue(MCDwarfDirs.size() + 1);
424 // Try not to emit an empty compilation directory.
425 SmallString<256> Dir;
426 StringRef CompDir = MCOS->getContext().getCompilationDir();
427 if (!CompilationDir.empty()) {
428 Dir = CompilationDir;
429 MCOS->getContext().remapDebugPath(Dir);
430 CompDir = Dir.str();
431 if (LineStr)
432 CompDir = LineStr->getSaver().save(CompDir);
433 }
434 if (LineStr) {
435 // Record path strings, emit references here.
436 LineStr->emitRef(MCOS, CompDir);
437 for (const auto &Dir : MCDwarfDirs)
438 LineStr->emitRef(MCOS, Dir);
439 } else {
440 // The list of directory paths. Compilation directory comes first.
441 MCOS->emitBytes(CompDir);
442 MCOS->emitBytes(StringRef("\0", 1));
443 for (const auto &Dir : MCDwarfDirs) {
444 MCOS->emitBytes(Dir); // The DirectoryName, and...
445 MCOS->emitBytes(StringRef("\0", 1)); // its null terminator.
446 }
447 }
448
449 // The file format, which is the inline null-terminated filename and a
450 // directory index. We don't track file size/timestamp so don't emit them
451 // in the v5 table. Emit MD5 checksums and source if we have them.
452 uint64_t Entries = 2;
453 if (HasAllMD5)
454 Entries += 1;
455 if (HasAnySource)
456 Entries += 1;
457 MCOS->emitInt8(Entries);
458 MCOS->emitULEB128IntValue(dwarf::DW_LNCT_path);
459 MCOS->emitULEB128IntValue(LineStr ? dwarf::DW_FORM_line_strp
460 : dwarf::DW_FORM_string);
461 MCOS->emitULEB128IntValue(dwarf::DW_LNCT_directory_index);
462 MCOS->emitULEB128IntValue(dwarf::DW_FORM_udata);
463 if (HasAllMD5) {
464 MCOS->emitULEB128IntValue(dwarf::DW_LNCT_MD5);
465 MCOS->emitULEB128IntValue(dwarf::DW_FORM_data16);
466 }
467 if (HasAnySource) {
468 MCOS->emitULEB128IntValue(dwarf::DW_LNCT_LLVM_source);
469 MCOS->emitULEB128IntValue(LineStr ? dwarf::DW_FORM_line_strp
470 : dwarf::DW_FORM_string);
471 }
472 // Then the counted list of files. The root file is file #0, then emit the
473 // files as provide by .file directives.
474 // MCDwarfFiles has an unused element [0] so use size() not size()+1.
475 // But sometimes MCDwarfFiles is empty, in which case we still emit one file.
476 MCOS->emitULEB128IntValue(MCDwarfFiles.empty() ? 1 : MCDwarfFiles.size());
477 // To accommodate assembler source written for DWARF v4 but trying to emit
478 // v5: If we didn't see a root file explicitly, replicate file #1.
479 assert((!RootFile.Name.empty() || MCDwarfFiles.size() >= 1) &&
480 "No root file and no .file directives");
481 emitOneV5FileEntry(MCOS, RootFile.Name.empty() ? MCDwarfFiles[1] : RootFile,
482 HasAllMD5, HasAnySource, LineStr);
483 for (unsigned i = 1; i < MCDwarfFiles.size(); ++i)
484 emitOneV5FileEntry(MCOS, MCDwarfFiles[i], HasAllMD5, HasAnySource, LineStr);
485 }
486
487 std::pair<MCSymbol *, MCSymbol *>
Emit(MCStreamer * MCOS,MCDwarfLineTableParams Params,ArrayRef<char> StandardOpcodeLengths,std::optional<MCDwarfLineStr> & LineStr) const488 MCDwarfLineTableHeader::Emit(MCStreamer *MCOS, MCDwarfLineTableParams Params,
489 ArrayRef<char> StandardOpcodeLengths,
490 std::optional<MCDwarfLineStr> &LineStr) const {
491 MCContext &context = MCOS->getContext();
492
493 // Create a symbol at the beginning of the line table.
494 MCSymbol *LineStartSym = Label;
495 if (!LineStartSym)
496 LineStartSym = context.createTempSymbol();
497
498 // Set the value of the symbol, as we are at the start of the line table.
499 MCOS->emitDwarfLineStartLabel(LineStartSym);
500
501 unsigned OffsetSize = dwarf::getDwarfOffsetByteSize(context.getDwarfFormat());
502
503 MCSymbol *LineEndSym = MCOS->emitDwarfUnitLength("debug_line", "unit length");
504
505 // Next 2 bytes is the Version.
506 unsigned LineTableVersion = context.getDwarfVersion();
507 MCOS->emitInt16(LineTableVersion);
508
509 // In v5, we get address info next.
510 if (LineTableVersion >= 5) {
511 MCOS->emitInt8(context.getAsmInfo()->getCodePointerSize());
512 MCOS->emitInt8(0); // Segment selector; same as EmitGenDwarfAranges.
513 }
514
515 // Create symbols for the start/end of the prologue.
516 MCSymbol *ProStartSym = context.createTempSymbol("prologue_start");
517 MCSymbol *ProEndSym = context.createTempSymbol("prologue_end");
518
519 // Length of the prologue, is the next 4 bytes (8 bytes for DWARF64). This is
520 // actually the length from after the length word, to the end of the prologue.
521 MCOS->emitAbsoluteSymbolDiff(ProEndSym, ProStartSym, OffsetSize);
522
523 MCOS->emitLabel(ProStartSym);
524
525 // Parameters of the state machine, are next.
526 MCOS->emitInt8(context.getAsmInfo()->getMinInstAlignment());
527 // maximum_operations_per_instruction
528 // For non-VLIW architectures this field is always 1.
529 // FIXME: VLIW architectures need to update this field accordingly.
530 if (LineTableVersion >= 4)
531 MCOS->emitInt8(1);
532 MCOS->emitInt8(DWARF2_LINE_DEFAULT_IS_STMT);
533 MCOS->emitInt8(Params.DWARF2LineBase);
534 MCOS->emitInt8(Params.DWARF2LineRange);
535 MCOS->emitInt8(StandardOpcodeLengths.size() + 1);
536
537 // Standard opcode lengths
538 for (char Length : StandardOpcodeLengths)
539 MCOS->emitInt8(Length);
540
541 // Put out the directory and file tables. The formats vary depending on
542 // the version.
543 if (LineTableVersion >= 5)
544 emitV5FileDirTables(MCOS, LineStr);
545 else
546 emitV2FileDirTables(MCOS);
547
548 // This is the end of the prologue, so set the value of the symbol at the
549 // end of the prologue (that was used in a previous expression).
550 MCOS->emitLabel(ProEndSym);
551
552 return std::make_pair(LineStartSym, LineEndSym);
553 }
554
emitCU(MCStreamer * MCOS,MCDwarfLineTableParams Params,std::optional<MCDwarfLineStr> & LineStr) const555 void MCDwarfLineTable::emitCU(MCStreamer *MCOS, MCDwarfLineTableParams Params,
556 std::optional<MCDwarfLineStr> &LineStr) const {
557 MCSymbol *LineEndSym = Header.Emit(MCOS, Params, LineStr).second;
558
559 // Put out the line tables.
560 for (const auto &LineSec : MCLineSections.getMCLineEntries())
561 emitOne(MCOS, LineSec.first, LineSec.second);
562
563 // This is the end of the section, so set the value of the symbol at the end
564 // of this section (that was used in a previous expression).
565 MCOS->emitLabel(LineEndSym);
566 }
567
568 Expected<unsigned>
tryGetFile(StringRef & Directory,StringRef & FileName,std::optional<MD5::MD5Result> Checksum,std::optional<StringRef> Source,uint16_t DwarfVersion,unsigned FileNumber)569 MCDwarfLineTable::tryGetFile(StringRef &Directory, StringRef &FileName,
570 std::optional<MD5::MD5Result> Checksum,
571 std::optional<StringRef> Source,
572 uint16_t DwarfVersion, unsigned FileNumber) {
573 return Header.tryGetFile(Directory, FileName, Checksum, Source, DwarfVersion,
574 FileNumber);
575 }
576
isRootFile(const MCDwarfFile & RootFile,StringRef & Directory,StringRef & FileName,std::optional<MD5::MD5Result> Checksum)577 static bool isRootFile(const MCDwarfFile &RootFile, StringRef &Directory,
578 StringRef &FileName,
579 std::optional<MD5::MD5Result> Checksum) {
580 if (RootFile.Name.empty() || StringRef(RootFile.Name) != FileName)
581 return false;
582 return RootFile.Checksum == Checksum;
583 }
584
585 Expected<unsigned>
tryGetFile(StringRef & Directory,StringRef & FileName,std::optional<MD5::MD5Result> Checksum,std::optional<StringRef> Source,uint16_t DwarfVersion,unsigned FileNumber)586 MCDwarfLineTableHeader::tryGetFile(StringRef &Directory, StringRef &FileName,
587 std::optional<MD5::MD5Result> Checksum,
588 std::optional<StringRef> Source,
589 uint16_t DwarfVersion, unsigned FileNumber) {
590 if (Directory == CompilationDir)
591 Directory = "";
592 if (FileName.empty()) {
593 FileName = "<stdin>";
594 Directory = "";
595 }
596 assert(!FileName.empty());
597 // Keep track of whether any or all files have an MD5 checksum.
598 // If any files have embedded source, they all must.
599 if (MCDwarfFiles.empty()) {
600 trackMD5Usage(Checksum.has_value());
601 HasAnySource |= Source.has_value();
602 }
603 if (DwarfVersion >= 5 && isRootFile(RootFile, Directory, FileName, Checksum))
604 return 0;
605 if (FileNumber == 0) {
606 // File numbers start with 1 and/or after any file numbers
607 // allocated by inline-assembler .file directives.
608 FileNumber = MCDwarfFiles.empty() ? 1 : MCDwarfFiles.size();
609 SmallString<256> Buffer;
610 auto IterBool = SourceIdMap.insert(
611 std::make_pair((Directory + Twine('\0') + FileName).toStringRef(Buffer),
612 FileNumber));
613 if (!IterBool.second)
614 return IterBool.first->second;
615 }
616 // Make space for this FileNumber in the MCDwarfFiles vector if needed.
617 if (FileNumber >= MCDwarfFiles.size())
618 MCDwarfFiles.resize(FileNumber + 1);
619
620 // Get the new MCDwarfFile slot for this FileNumber.
621 MCDwarfFile &File = MCDwarfFiles[FileNumber];
622
623 // It is an error to see the same number more than once.
624 if (!File.Name.empty())
625 return make_error<StringError>("file number already allocated",
626 inconvertibleErrorCode());
627
628 if (Directory.empty()) {
629 // Separate the directory part from the basename of the FileName.
630 StringRef tFileName = sys::path::filename(FileName);
631 if (!tFileName.empty()) {
632 Directory = sys::path::parent_path(FileName);
633 if (!Directory.empty())
634 FileName = tFileName;
635 }
636 }
637
638 // Find or make an entry in the MCDwarfDirs vector for this Directory.
639 // Capture directory name.
640 unsigned DirIndex;
641 if (Directory.empty()) {
642 // For FileNames with no directories a DirIndex of 0 is used.
643 DirIndex = 0;
644 } else {
645 DirIndex = llvm::find(MCDwarfDirs, Directory) - MCDwarfDirs.begin();
646 if (DirIndex >= MCDwarfDirs.size())
647 MCDwarfDirs.push_back(std::string(Directory));
648 // The DirIndex is one based, as DirIndex of 0 is used for FileNames with
649 // no directories. MCDwarfDirs[] is unlike MCDwarfFiles[] in that the
650 // directory names are stored at MCDwarfDirs[DirIndex-1] where FileNames
651 // are stored at MCDwarfFiles[FileNumber].Name .
652 DirIndex++;
653 }
654
655 File.Name = std::string(FileName);
656 File.DirIndex = DirIndex;
657 File.Checksum = Checksum;
658 trackMD5Usage(Checksum.has_value());
659 File.Source = Source;
660 if (Source.has_value())
661 HasAnySource = true;
662
663 // return the allocated FileNumber.
664 return FileNumber;
665 }
666
667 /// Utility function to emit the encoding to a streamer.
Emit(MCStreamer * MCOS,MCDwarfLineTableParams Params,int64_t LineDelta,uint64_t AddrDelta)668 void MCDwarfLineAddr::Emit(MCStreamer *MCOS, MCDwarfLineTableParams Params,
669 int64_t LineDelta, uint64_t AddrDelta) {
670 MCContext &Context = MCOS->getContext();
671 SmallString<256> Tmp;
672 MCDwarfLineAddr::encode(Context, Params, LineDelta, AddrDelta, Tmp);
673 MCOS->emitBytes(Tmp);
674 }
675
676 /// Given a special op, return the address skip amount (in units of
677 /// DWARF2_LINE_MIN_INSN_LENGTH).
SpecialAddr(MCDwarfLineTableParams Params,uint64_t op)678 static uint64_t SpecialAddr(MCDwarfLineTableParams Params, uint64_t op) {
679 return (op - Params.DWARF2LineOpcodeBase) / Params.DWARF2LineRange;
680 }
681
682 /// Utility function to encode a Dwarf pair of LineDelta and AddrDeltas.
encode(MCContext & Context,MCDwarfLineTableParams Params,int64_t LineDelta,uint64_t AddrDelta,SmallVectorImpl<char> & Out)683 void MCDwarfLineAddr::encode(MCContext &Context, MCDwarfLineTableParams Params,
684 int64_t LineDelta, uint64_t AddrDelta,
685 SmallVectorImpl<char> &Out) {
686 uint8_t Buf[16];
687 uint64_t Temp, Opcode;
688 bool NeedCopy = false;
689
690 // The maximum address skip amount that can be encoded with a special op.
691 uint64_t MaxSpecialAddrDelta = SpecialAddr(Params, 255);
692
693 // Scale the address delta by the minimum instruction length.
694 AddrDelta = ScaleAddrDelta(Context, AddrDelta);
695
696 // A LineDelta of INT64_MAX is a signal that this is actually a
697 // DW_LNE_end_sequence. We cannot use special opcodes here, since we want the
698 // end_sequence to emit the matrix entry.
699 if (LineDelta == INT64_MAX) {
700 if (AddrDelta == MaxSpecialAddrDelta)
701 Out.push_back(dwarf::DW_LNS_const_add_pc);
702 else if (AddrDelta) {
703 Out.push_back(dwarf::DW_LNS_advance_pc);
704 Out.append(Buf, Buf + encodeULEB128(AddrDelta, Buf));
705 }
706 Out.push_back(dwarf::DW_LNS_extended_op);
707 Out.push_back(1);
708 Out.push_back(dwarf::DW_LNE_end_sequence);
709 return;
710 }
711
712 // Bias the line delta by the base.
713 Temp = LineDelta - Params.DWARF2LineBase;
714
715 // If the line increment is out of range of a special opcode, we must encode
716 // it with DW_LNS_advance_line.
717 if (Temp >= Params.DWARF2LineRange ||
718 Temp + Params.DWARF2LineOpcodeBase > 255) {
719 Out.push_back(dwarf::DW_LNS_advance_line);
720 Out.append(Buf, Buf + encodeSLEB128(LineDelta, Buf));
721
722 LineDelta = 0;
723 Temp = 0 - Params.DWARF2LineBase;
724 NeedCopy = true;
725 }
726
727 // Use DW_LNS_copy instead of a "line +0, addr +0" special opcode.
728 if (LineDelta == 0 && AddrDelta == 0) {
729 Out.push_back(dwarf::DW_LNS_copy);
730 return;
731 }
732
733 // Bias the opcode by the special opcode base.
734 Temp += Params.DWARF2LineOpcodeBase;
735
736 // Avoid overflow when addr_delta is large.
737 if (AddrDelta < 256 + MaxSpecialAddrDelta) {
738 // Try using a special opcode.
739 Opcode = Temp + AddrDelta * Params.DWARF2LineRange;
740 if (Opcode <= 255) {
741 Out.push_back(Opcode);
742 return;
743 }
744
745 // Try using DW_LNS_const_add_pc followed by special op.
746 Opcode = Temp + (AddrDelta - MaxSpecialAddrDelta) * Params.DWARF2LineRange;
747 if (Opcode <= 255) {
748 Out.push_back(dwarf::DW_LNS_const_add_pc);
749 Out.push_back(Opcode);
750 return;
751 }
752 }
753
754 // Otherwise use DW_LNS_advance_pc.
755 Out.push_back(dwarf::DW_LNS_advance_pc);
756 Out.append(Buf, Buf + encodeULEB128(AddrDelta, Buf));
757
758 if (NeedCopy)
759 Out.push_back(dwarf::DW_LNS_copy);
760 else {
761 assert(Temp <= 255 && "Buggy special opcode encoding.");
762 Out.push_back(Temp);
763 }
764 }
765
766 // Utility function to write a tuple for .debug_abbrev.
EmitAbbrev(MCStreamer * MCOS,uint64_t Name,uint64_t Form)767 static void EmitAbbrev(MCStreamer *MCOS, uint64_t Name, uint64_t Form) {
768 MCOS->emitULEB128IntValue(Name);
769 MCOS->emitULEB128IntValue(Form);
770 }
771
772 // When generating dwarf for assembly source files this emits
773 // the data for .debug_abbrev section which contains three DIEs.
EmitGenDwarfAbbrev(MCStreamer * MCOS)774 static void EmitGenDwarfAbbrev(MCStreamer *MCOS) {
775 MCContext &context = MCOS->getContext();
776 MCOS->switchSection(context.getObjectFileInfo()->getDwarfAbbrevSection());
777
778 // DW_TAG_compile_unit DIE abbrev (1).
779 MCOS->emitULEB128IntValue(1);
780 MCOS->emitULEB128IntValue(dwarf::DW_TAG_compile_unit);
781 MCOS->emitInt8(dwarf::DW_CHILDREN_yes);
782 dwarf::Form SecOffsetForm =
783 context.getDwarfVersion() >= 4
784 ? dwarf::DW_FORM_sec_offset
785 : (context.getDwarfFormat() == dwarf::DWARF64 ? dwarf::DW_FORM_data8
786 : dwarf::DW_FORM_data4);
787 EmitAbbrev(MCOS, dwarf::DW_AT_stmt_list, SecOffsetForm);
788 if (context.getGenDwarfSectionSyms().size() > 1 &&
789 context.getDwarfVersion() >= 3) {
790 EmitAbbrev(MCOS, dwarf::DW_AT_ranges, SecOffsetForm);
791 } else {
792 EmitAbbrev(MCOS, dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr);
793 EmitAbbrev(MCOS, dwarf::DW_AT_high_pc, dwarf::DW_FORM_addr);
794 }
795 EmitAbbrev(MCOS, dwarf::DW_AT_name, dwarf::DW_FORM_string);
796 if (!context.getCompilationDir().empty())
797 EmitAbbrev(MCOS, dwarf::DW_AT_comp_dir, dwarf::DW_FORM_string);
798 StringRef DwarfDebugFlags = context.getDwarfDebugFlags();
799 if (!DwarfDebugFlags.empty())
800 EmitAbbrev(MCOS, dwarf::DW_AT_APPLE_flags, dwarf::DW_FORM_string);
801 EmitAbbrev(MCOS, dwarf::DW_AT_producer, dwarf::DW_FORM_string);
802 EmitAbbrev(MCOS, dwarf::DW_AT_language, dwarf::DW_FORM_data2);
803 EmitAbbrev(MCOS, 0, 0);
804
805 // DW_TAG_label DIE abbrev (2).
806 MCOS->emitULEB128IntValue(2);
807 MCOS->emitULEB128IntValue(dwarf::DW_TAG_label);
808 MCOS->emitInt8(dwarf::DW_CHILDREN_no);
809 EmitAbbrev(MCOS, dwarf::DW_AT_name, dwarf::DW_FORM_string);
810 EmitAbbrev(MCOS, dwarf::DW_AT_decl_file, dwarf::DW_FORM_data4);
811 EmitAbbrev(MCOS, dwarf::DW_AT_decl_line, dwarf::DW_FORM_data4);
812 EmitAbbrev(MCOS, dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr);
813 EmitAbbrev(MCOS, 0, 0);
814
815 // Terminate the abbreviations for this compilation unit.
816 MCOS->emitInt8(0);
817 }
818
819 // When generating dwarf for assembly source files this emits the data for
820 // .debug_aranges section. This section contains a header and a table of pairs
821 // of PointerSize'ed values for the address and size of section(s) with line
822 // table entries.
EmitGenDwarfAranges(MCStreamer * MCOS,const MCSymbol * InfoSectionSymbol)823 static void EmitGenDwarfAranges(MCStreamer *MCOS,
824 const MCSymbol *InfoSectionSymbol) {
825 MCContext &context = MCOS->getContext();
826
827 auto &Sections = context.getGenDwarfSectionSyms();
828
829 MCOS->switchSection(context.getObjectFileInfo()->getDwarfARangesSection());
830
831 unsigned UnitLengthBytes =
832 dwarf::getUnitLengthFieldByteSize(context.getDwarfFormat());
833 unsigned OffsetSize = dwarf::getDwarfOffsetByteSize(context.getDwarfFormat());
834
835 // This will be the length of the .debug_aranges section, first account for
836 // the size of each item in the header (see below where we emit these items).
837 int Length = UnitLengthBytes + 2 + OffsetSize + 1 + 1;
838
839 // Figure the padding after the header before the table of address and size
840 // pairs who's values are PointerSize'ed.
841 const MCAsmInfo *asmInfo = context.getAsmInfo();
842 int AddrSize = asmInfo->getCodePointerSize();
843 int Pad = 2 * AddrSize - (Length & (2 * AddrSize - 1));
844 if (Pad == 2 * AddrSize)
845 Pad = 0;
846 Length += Pad;
847
848 // Add the size of the pair of PointerSize'ed values for the address and size
849 // of each section we have in the table.
850 Length += 2 * AddrSize * Sections.size();
851 // And the pair of terminating zeros.
852 Length += 2 * AddrSize;
853
854 // Emit the header for this section.
855 if (context.getDwarfFormat() == dwarf::DWARF64)
856 // The DWARF64 mark.
857 MCOS->emitInt32(dwarf::DW_LENGTH_DWARF64);
858 // The 4 (8 for DWARF64) byte length not including the length of the unit
859 // length field itself.
860 MCOS->emitIntValue(Length - UnitLengthBytes, OffsetSize);
861 // The 2 byte version, which is 2.
862 MCOS->emitInt16(2);
863 // The 4 (8 for DWARF64) byte offset to the compile unit in the .debug_info
864 // from the start of the .debug_info.
865 if (InfoSectionSymbol)
866 MCOS->emitSymbolValue(InfoSectionSymbol, OffsetSize,
867 asmInfo->needsDwarfSectionOffsetDirective());
868 else
869 MCOS->emitIntValue(0, OffsetSize);
870 // The 1 byte size of an address.
871 MCOS->emitInt8(AddrSize);
872 // The 1 byte size of a segment descriptor, we use a value of zero.
873 MCOS->emitInt8(0);
874 // Align the header with the padding if needed, before we put out the table.
875 for(int i = 0; i < Pad; i++)
876 MCOS->emitInt8(0);
877
878 // Now emit the table of pairs of PointerSize'ed values for the section
879 // addresses and sizes.
880 for (MCSection *Sec : Sections) {
881 const MCSymbol *StartSymbol = Sec->getBeginSymbol();
882 MCSymbol *EndSymbol = Sec->getEndSymbol(context);
883 assert(StartSymbol && "StartSymbol must not be NULL");
884 assert(EndSymbol && "EndSymbol must not be NULL");
885
886 const MCExpr *Addr = MCSymbolRefExpr::create(
887 StartSymbol, MCSymbolRefExpr::VK_None, context);
888 const MCExpr *Size =
889 makeEndMinusStartExpr(context, *StartSymbol, *EndSymbol, 0);
890 MCOS->emitValue(Addr, AddrSize);
891 emitAbsValue(*MCOS, Size, AddrSize);
892 }
893
894 // And finally the pair of terminating zeros.
895 MCOS->emitIntValue(0, AddrSize);
896 MCOS->emitIntValue(0, AddrSize);
897 }
898
899 // When generating dwarf for assembly source files this emits the data for
900 // .debug_info section which contains three parts. The header, the compile_unit
901 // DIE and a list of label DIEs.
EmitGenDwarfInfo(MCStreamer * MCOS,const MCSymbol * AbbrevSectionSymbol,const MCSymbol * LineSectionSymbol,const MCSymbol * RangesSymbol)902 static void EmitGenDwarfInfo(MCStreamer *MCOS,
903 const MCSymbol *AbbrevSectionSymbol,
904 const MCSymbol *LineSectionSymbol,
905 const MCSymbol *RangesSymbol) {
906 MCContext &context = MCOS->getContext();
907
908 MCOS->switchSection(context.getObjectFileInfo()->getDwarfInfoSection());
909
910 // Create a symbol at the start and end of this section used in here for the
911 // expression to calculate the length in the header.
912 MCSymbol *InfoStart = context.createTempSymbol();
913 MCOS->emitLabel(InfoStart);
914 MCSymbol *InfoEnd = context.createTempSymbol();
915
916 // First part: the header.
917
918 unsigned UnitLengthBytes =
919 dwarf::getUnitLengthFieldByteSize(context.getDwarfFormat());
920 unsigned OffsetSize = dwarf::getDwarfOffsetByteSize(context.getDwarfFormat());
921
922 if (context.getDwarfFormat() == dwarf::DWARF64)
923 // Emit DWARF64 mark.
924 MCOS->emitInt32(dwarf::DW_LENGTH_DWARF64);
925
926 // The 4 (8 for DWARF64) byte total length of the information for this
927 // compilation unit, not including the unit length field itself.
928 const MCExpr *Length =
929 makeEndMinusStartExpr(context, *InfoStart, *InfoEnd, UnitLengthBytes);
930 emitAbsValue(*MCOS, Length, OffsetSize);
931
932 // The 2 byte DWARF version.
933 MCOS->emitInt16(context.getDwarfVersion());
934
935 // The DWARF v5 header has unit type, address size, abbrev offset.
936 // Earlier versions have abbrev offset, address size.
937 const MCAsmInfo &AsmInfo = *context.getAsmInfo();
938 int AddrSize = AsmInfo.getCodePointerSize();
939 if (context.getDwarfVersion() >= 5) {
940 MCOS->emitInt8(dwarf::DW_UT_compile);
941 MCOS->emitInt8(AddrSize);
942 }
943 // The 4 (8 for DWARF64) byte offset to the debug abbrevs from the start of
944 // the .debug_abbrev.
945 if (AbbrevSectionSymbol)
946 MCOS->emitSymbolValue(AbbrevSectionSymbol, OffsetSize,
947 AsmInfo.needsDwarfSectionOffsetDirective());
948 else
949 // Since the abbrevs are at the start of the section, the offset is zero.
950 MCOS->emitIntValue(0, OffsetSize);
951 if (context.getDwarfVersion() <= 4)
952 MCOS->emitInt8(AddrSize);
953
954 // Second part: the compile_unit DIE.
955
956 // The DW_TAG_compile_unit DIE abbrev (1).
957 MCOS->emitULEB128IntValue(1);
958
959 // DW_AT_stmt_list, a 4 (8 for DWARF64) byte offset from the start of the
960 // .debug_line section.
961 if (LineSectionSymbol)
962 MCOS->emitSymbolValue(LineSectionSymbol, OffsetSize,
963 AsmInfo.needsDwarfSectionOffsetDirective());
964 else
965 // The line table is at the start of the section, so the offset is zero.
966 MCOS->emitIntValue(0, OffsetSize);
967
968 if (RangesSymbol) {
969 // There are multiple sections containing code, so we must use
970 // .debug_ranges/.debug_rnglists. AT_ranges, the 4/8 byte offset from the
971 // start of the .debug_ranges/.debug_rnglists.
972 MCOS->emitSymbolValue(RangesSymbol, OffsetSize);
973 } else {
974 // If we only have one non-empty code section, we can use the simpler
975 // AT_low_pc and AT_high_pc attributes.
976
977 // Find the first (and only) non-empty text section
978 auto &Sections = context.getGenDwarfSectionSyms();
979 const auto TextSection = Sections.begin();
980 assert(TextSection != Sections.end() && "No text section found");
981
982 MCSymbol *StartSymbol = (*TextSection)->getBeginSymbol();
983 MCSymbol *EndSymbol = (*TextSection)->getEndSymbol(context);
984 assert(StartSymbol && "StartSymbol must not be NULL");
985 assert(EndSymbol && "EndSymbol must not be NULL");
986
987 // AT_low_pc, the first address of the default .text section.
988 const MCExpr *Start = MCSymbolRefExpr::create(
989 StartSymbol, MCSymbolRefExpr::VK_None, context);
990 MCOS->emitValue(Start, AddrSize);
991
992 // AT_high_pc, the last address of the default .text section.
993 const MCExpr *End = MCSymbolRefExpr::create(
994 EndSymbol, MCSymbolRefExpr::VK_None, context);
995 MCOS->emitValue(End, AddrSize);
996 }
997
998 // AT_name, the name of the source file. Reconstruct from the first directory
999 // and file table entries.
1000 const SmallVectorImpl<std::string> &MCDwarfDirs = context.getMCDwarfDirs();
1001 if (MCDwarfDirs.size() > 0) {
1002 MCOS->emitBytes(MCDwarfDirs[0]);
1003 MCOS->emitBytes(sys::path::get_separator());
1004 }
1005 const SmallVectorImpl<MCDwarfFile> &MCDwarfFiles = context.getMCDwarfFiles();
1006 // MCDwarfFiles might be empty if we have an empty source file.
1007 // If it's not empty, [0] is unused and [1] is the first actual file.
1008 assert(MCDwarfFiles.empty() || MCDwarfFiles.size() >= 2);
1009 const MCDwarfFile &RootFile =
1010 MCDwarfFiles.empty()
1011 ? context.getMCDwarfLineTable(/*CUID=*/0).getRootFile()
1012 : MCDwarfFiles[1];
1013 MCOS->emitBytes(RootFile.Name);
1014 MCOS->emitInt8(0); // NULL byte to terminate the string.
1015
1016 // AT_comp_dir, the working directory the assembly was done in.
1017 if (!context.getCompilationDir().empty()) {
1018 MCOS->emitBytes(context.getCompilationDir());
1019 MCOS->emitInt8(0); // NULL byte to terminate the string.
1020 }
1021
1022 // AT_APPLE_flags, the command line arguments of the assembler tool.
1023 StringRef DwarfDebugFlags = context.getDwarfDebugFlags();
1024 if (!DwarfDebugFlags.empty()){
1025 MCOS->emitBytes(DwarfDebugFlags);
1026 MCOS->emitInt8(0); // NULL byte to terminate the string.
1027 }
1028
1029 // AT_producer, the version of the assembler tool.
1030 StringRef DwarfDebugProducer = context.getDwarfDebugProducer();
1031 if (!DwarfDebugProducer.empty())
1032 MCOS->emitBytes(DwarfDebugProducer);
1033 else
1034 MCOS->emitBytes(StringRef("llvm-mc (based on LLVM " PACKAGE_VERSION ")"));
1035 MCOS->emitInt8(0); // NULL byte to terminate the string.
1036
1037 // AT_language, a 4 byte value. We use DW_LANG_Mips_Assembler as the dwarf2
1038 // draft has no standard code for assembler.
1039 MCOS->emitInt16(dwarf::DW_LANG_Mips_Assembler);
1040
1041 // Third part: the list of label DIEs.
1042
1043 // Loop on saved info for dwarf labels and create the DIEs for them.
1044 const std::vector<MCGenDwarfLabelEntry> &Entries =
1045 MCOS->getContext().getMCGenDwarfLabelEntries();
1046 for (const auto &Entry : Entries) {
1047 // The DW_TAG_label DIE abbrev (2).
1048 MCOS->emitULEB128IntValue(2);
1049
1050 // AT_name, of the label without any leading underbar.
1051 MCOS->emitBytes(Entry.getName());
1052 MCOS->emitInt8(0); // NULL byte to terminate the string.
1053
1054 // AT_decl_file, index into the file table.
1055 MCOS->emitInt32(Entry.getFileNumber());
1056
1057 // AT_decl_line, source line number.
1058 MCOS->emitInt32(Entry.getLineNumber());
1059
1060 // AT_low_pc, start address of the label.
1061 const MCExpr *AT_low_pc = MCSymbolRefExpr::create(Entry.getLabel(),
1062 MCSymbolRefExpr::VK_None, context);
1063 MCOS->emitValue(AT_low_pc, AddrSize);
1064 }
1065
1066 // Add the NULL DIE terminating the Compile Unit DIE's.
1067 MCOS->emitInt8(0);
1068
1069 // Now set the value of the symbol at the end of the info section.
1070 MCOS->emitLabel(InfoEnd);
1071 }
1072
1073 // When generating dwarf for assembly source files this emits the data for
1074 // .debug_ranges section. We only emit one range list, which spans all of the
1075 // executable sections of this file.
emitGenDwarfRanges(MCStreamer * MCOS)1076 static MCSymbol *emitGenDwarfRanges(MCStreamer *MCOS) {
1077 MCContext &context = MCOS->getContext();
1078 auto &Sections = context.getGenDwarfSectionSyms();
1079
1080 const MCAsmInfo *AsmInfo = context.getAsmInfo();
1081 int AddrSize = AsmInfo->getCodePointerSize();
1082 MCSymbol *RangesSymbol;
1083
1084 if (MCOS->getContext().getDwarfVersion() >= 5) {
1085 MCOS->switchSection(context.getObjectFileInfo()->getDwarfRnglistsSection());
1086 MCSymbol *EndSymbol = mcdwarf::emitListsTableHeaderStart(*MCOS);
1087 MCOS->AddComment("Offset entry count");
1088 MCOS->emitInt32(0);
1089 RangesSymbol = context.createTempSymbol("debug_rnglist0_start");
1090 MCOS->emitLabel(RangesSymbol);
1091 for (MCSection *Sec : Sections) {
1092 const MCSymbol *StartSymbol = Sec->getBeginSymbol();
1093 const MCSymbol *EndSymbol = Sec->getEndSymbol(context);
1094 const MCExpr *SectionStartAddr = MCSymbolRefExpr::create(
1095 StartSymbol, MCSymbolRefExpr::VK_None, context);
1096 const MCExpr *SectionSize =
1097 makeEndMinusStartExpr(context, *StartSymbol, *EndSymbol, 0);
1098 MCOS->emitInt8(dwarf::DW_RLE_start_length);
1099 MCOS->emitValue(SectionStartAddr, AddrSize);
1100 MCOS->emitULEB128Value(SectionSize);
1101 }
1102 MCOS->emitInt8(dwarf::DW_RLE_end_of_list);
1103 MCOS->emitLabel(EndSymbol);
1104 } else {
1105 MCOS->switchSection(context.getObjectFileInfo()->getDwarfRangesSection());
1106 RangesSymbol = context.createTempSymbol("debug_ranges_start");
1107 MCOS->emitLabel(RangesSymbol);
1108 for (MCSection *Sec : Sections) {
1109 const MCSymbol *StartSymbol = Sec->getBeginSymbol();
1110 const MCSymbol *EndSymbol = Sec->getEndSymbol(context);
1111
1112 // Emit a base address selection entry for the section start.
1113 const MCExpr *SectionStartAddr = MCSymbolRefExpr::create(
1114 StartSymbol, MCSymbolRefExpr::VK_None, context);
1115 MCOS->emitFill(AddrSize, 0xFF);
1116 MCOS->emitValue(SectionStartAddr, AddrSize);
1117
1118 // Emit a range list entry spanning this section.
1119 const MCExpr *SectionSize =
1120 makeEndMinusStartExpr(context, *StartSymbol, *EndSymbol, 0);
1121 MCOS->emitIntValue(0, AddrSize);
1122 emitAbsValue(*MCOS, SectionSize, AddrSize);
1123 }
1124
1125 // Emit end of list entry
1126 MCOS->emitIntValue(0, AddrSize);
1127 MCOS->emitIntValue(0, AddrSize);
1128 }
1129
1130 return RangesSymbol;
1131 }
1132
1133 //
1134 // When generating dwarf for assembly source files this emits the Dwarf
1135 // sections.
1136 //
Emit(MCStreamer * MCOS)1137 void MCGenDwarfInfo::Emit(MCStreamer *MCOS) {
1138 MCContext &context = MCOS->getContext();
1139
1140 // Create the dwarf sections in this order (.debug_line already created).
1141 const MCAsmInfo *AsmInfo = context.getAsmInfo();
1142 bool CreateDwarfSectionSymbols =
1143 AsmInfo->doesDwarfUseRelocationsAcrossSections();
1144 MCSymbol *LineSectionSymbol = nullptr;
1145 if (CreateDwarfSectionSymbols)
1146 LineSectionSymbol = MCOS->getDwarfLineTableSymbol(0);
1147 MCSymbol *AbbrevSectionSymbol = nullptr;
1148 MCSymbol *InfoSectionSymbol = nullptr;
1149 MCSymbol *RangesSymbol = nullptr;
1150
1151 // Create end symbols for each section, and remove empty sections
1152 MCOS->getContext().finalizeDwarfSections(*MCOS);
1153
1154 // If there are no sections to generate debug info for, we don't need
1155 // to do anything
1156 if (MCOS->getContext().getGenDwarfSectionSyms().empty())
1157 return;
1158
1159 // We only use the .debug_ranges section if we have multiple code sections,
1160 // and we are emitting a DWARF version which supports it.
1161 const bool UseRangesSection =
1162 MCOS->getContext().getGenDwarfSectionSyms().size() > 1 &&
1163 MCOS->getContext().getDwarfVersion() >= 3;
1164 CreateDwarfSectionSymbols |= UseRangesSection;
1165
1166 MCOS->switchSection(context.getObjectFileInfo()->getDwarfInfoSection());
1167 if (CreateDwarfSectionSymbols) {
1168 InfoSectionSymbol = context.createTempSymbol();
1169 MCOS->emitLabel(InfoSectionSymbol);
1170 }
1171 MCOS->switchSection(context.getObjectFileInfo()->getDwarfAbbrevSection());
1172 if (CreateDwarfSectionSymbols) {
1173 AbbrevSectionSymbol = context.createTempSymbol();
1174 MCOS->emitLabel(AbbrevSectionSymbol);
1175 }
1176
1177 MCOS->switchSection(context.getObjectFileInfo()->getDwarfARangesSection());
1178
1179 // Output the data for .debug_aranges section.
1180 EmitGenDwarfAranges(MCOS, InfoSectionSymbol);
1181
1182 if (UseRangesSection) {
1183 RangesSymbol = emitGenDwarfRanges(MCOS);
1184 assert(RangesSymbol);
1185 }
1186
1187 // Output the data for .debug_abbrev section.
1188 EmitGenDwarfAbbrev(MCOS);
1189
1190 // Output the data for .debug_info section.
1191 EmitGenDwarfInfo(MCOS, AbbrevSectionSymbol, LineSectionSymbol, RangesSymbol);
1192 }
1193
1194 //
1195 // When generating dwarf for assembly source files this is called when symbol
1196 // for a label is created. If this symbol is not a temporary and is in the
1197 // section that dwarf is being generated for, save the needed info to create
1198 // a dwarf label.
1199 //
Make(MCSymbol * Symbol,MCStreamer * MCOS,SourceMgr & SrcMgr,SMLoc & Loc)1200 void MCGenDwarfLabelEntry::Make(MCSymbol *Symbol, MCStreamer *MCOS,
1201 SourceMgr &SrcMgr, SMLoc &Loc) {
1202 // We won't create dwarf labels for temporary symbols.
1203 if (Symbol->isTemporary())
1204 return;
1205 MCContext &context = MCOS->getContext();
1206 // We won't create dwarf labels for symbols in sections that we are not
1207 // generating debug info for.
1208 if (!context.getGenDwarfSectionSyms().count(MCOS->getCurrentSectionOnly()))
1209 return;
1210
1211 // The dwarf label's name does not have the symbol name's leading
1212 // underbar if any.
1213 StringRef Name = Symbol->getName();
1214 if (Name.starts_with("_"))
1215 Name = Name.substr(1, Name.size()-1);
1216
1217 // Get the dwarf file number to be used for the dwarf label.
1218 unsigned FileNumber = context.getGenDwarfFileNumber();
1219
1220 // Finding the line number is the expensive part which is why we just don't
1221 // pass it in as for some symbols we won't create a dwarf label.
1222 unsigned CurBuffer = SrcMgr.FindBufferContainingLoc(Loc);
1223 unsigned LineNumber = SrcMgr.FindLineNumber(Loc, CurBuffer);
1224
1225 // We create a temporary symbol for use for the AT_high_pc and AT_low_pc
1226 // values so that they don't have things like an ARM thumb bit from the
1227 // original symbol. So when used they won't get a low bit set after
1228 // relocation.
1229 MCSymbol *Label = context.createTempSymbol();
1230 MCOS->emitLabel(Label);
1231
1232 // Create and entry for the info and add it to the other entries.
1233 MCOS->getContext().addMCGenDwarfLabelEntry(
1234 MCGenDwarfLabelEntry(Name, FileNumber, LineNumber, Label));
1235 }
1236
getDataAlignmentFactor(MCStreamer & streamer)1237 static int getDataAlignmentFactor(MCStreamer &streamer) {
1238 MCContext &context = streamer.getContext();
1239 const MCAsmInfo *asmInfo = context.getAsmInfo();
1240 int size = asmInfo->getCalleeSaveStackSlotSize();
1241 if (asmInfo->isStackGrowthDirectionUp())
1242 return size;
1243 else
1244 return -size;
1245 }
1246
getSizeForEncoding(MCStreamer & streamer,unsigned symbolEncoding)1247 static unsigned getSizeForEncoding(MCStreamer &streamer,
1248 unsigned symbolEncoding) {
1249 MCContext &context = streamer.getContext();
1250 unsigned format = symbolEncoding & 0x0f;
1251 switch (format) {
1252 default: llvm_unreachable("Unknown Encoding");
1253 case dwarf::DW_EH_PE_absptr:
1254 case dwarf::DW_EH_PE_signed:
1255 return context.getAsmInfo()->getCodePointerSize();
1256 case dwarf::DW_EH_PE_udata2:
1257 case dwarf::DW_EH_PE_sdata2:
1258 return 2;
1259 case dwarf::DW_EH_PE_udata4:
1260 case dwarf::DW_EH_PE_sdata4:
1261 return 4;
1262 case dwarf::DW_EH_PE_udata8:
1263 case dwarf::DW_EH_PE_sdata8:
1264 return 8;
1265 }
1266 }
1267
emitFDESymbol(MCObjectStreamer & streamer,const MCSymbol & symbol,unsigned symbolEncoding,bool isEH)1268 static void emitFDESymbol(MCObjectStreamer &streamer, const MCSymbol &symbol,
1269 unsigned symbolEncoding, bool isEH) {
1270 MCContext &context = streamer.getContext();
1271 const MCAsmInfo *asmInfo = context.getAsmInfo();
1272 const MCExpr *v = asmInfo->getExprForFDESymbol(&symbol,
1273 symbolEncoding,
1274 streamer);
1275 unsigned size = getSizeForEncoding(streamer, symbolEncoding);
1276 if (asmInfo->doDwarfFDESymbolsUseAbsDiff() && isEH)
1277 emitAbsValue(streamer, v, size);
1278 else
1279 streamer.emitValue(v, size);
1280 }
1281
EmitPersonality(MCStreamer & streamer,const MCSymbol & symbol,unsigned symbolEncoding)1282 static void EmitPersonality(MCStreamer &streamer, const MCSymbol &symbol,
1283 unsigned symbolEncoding) {
1284 MCContext &context = streamer.getContext();
1285 const MCAsmInfo *asmInfo = context.getAsmInfo();
1286 const MCExpr *v = asmInfo->getExprForPersonalitySymbol(&symbol,
1287 symbolEncoding,
1288 streamer);
1289 unsigned size = getSizeForEncoding(streamer, symbolEncoding);
1290 streamer.emitValue(v, size);
1291 }
1292
1293 namespace {
1294
1295 class FrameEmitterImpl {
1296 int CFAOffset = 0;
1297 int InitialCFAOffset = 0;
1298 bool IsEH;
1299 MCObjectStreamer &Streamer;
1300
1301 public:
FrameEmitterImpl(bool IsEH,MCObjectStreamer & Streamer)1302 FrameEmitterImpl(bool IsEH, MCObjectStreamer &Streamer)
1303 : IsEH(IsEH), Streamer(Streamer) {}
1304
1305 /// Emit the unwind information in a compact way.
1306 void EmitCompactUnwind(const MCDwarfFrameInfo &frame);
1307
1308 const MCSymbol &EmitCIE(const MCDwarfFrameInfo &F);
1309 void EmitFDE(const MCSymbol &cieStart, const MCDwarfFrameInfo &frame,
1310 bool LastInSection, const MCSymbol &SectionStart);
1311 void emitCFIInstructions(ArrayRef<MCCFIInstruction> Instrs,
1312 MCSymbol *BaseLabel);
1313 void emitCFIInstruction(const MCCFIInstruction &Instr);
1314 };
1315
1316 } // end anonymous namespace
1317
emitEncodingByte(MCObjectStreamer & Streamer,unsigned Encoding)1318 static void emitEncodingByte(MCObjectStreamer &Streamer, unsigned Encoding) {
1319 Streamer.emitInt8(Encoding);
1320 }
1321
emitCFIInstruction(const MCCFIInstruction & Instr)1322 void FrameEmitterImpl::emitCFIInstruction(const MCCFIInstruction &Instr) {
1323 int dataAlignmentFactor = getDataAlignmentFactor(Streamer);
1324 auto *MRI = Streamer.getContext().getRegisterInfo();
1325
1326 switch (Instr.getOperation()) {
1327 case MCCFIInstruction::OpRegister: {
1328 unsigned Reg1 = Instr.getRegister();
1329 unsigned Reg2 = Instr.getRegister2();
1330 if (!IsEH) {
1331 Reg1 = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg1);
1332 Reg2 = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg2);
1333 }
1334 Streamer.emitInt8(dwarf::DW_CFA_register);
1335 Streamer.emitULEB128IntValue(Reg1);
1336 Streamer.emitULEB128IntValue(Reg2);
1337 return;
1338 }
1339 case MCCFIInstruction::OpWindowSave:
1340 Streamer.emitInt8(dwarf::DW_CFA_GNU_window_save);
1341 return;
1342
1343 case MCCFIInstruction::OpNegateRAState:
1344 Streamer.emitInt8(dwarf::DW_CFA_AARCH64_negate_ra_state);
1345 return;
1346
1347 case MCCFIInstruction::OpUndefined: {
1348 unsigned Reg = Instr.getRegister();
1349 Streamer.emitInt8(dwarf::DW_CFA_undefined);
1350 Streamer.emitULEB128IntValue(Reg);
1351 return;
1352 }
1353 case MCCFIInstruction::OpAdjustCfaOffset:
1354 case MCCFIInstruction::OpDefCfaOffset: {
1355 const bool IsRelative =
1356 Instr.getOperation() == MCCFIInstruction::OpAdjustCfaOffset;
1357
1358 Streamer.emitInt8(dwarf::DW_CFA_def_cfa_offset);
1359
1360 if (IsRelative)
1361 CFAOffset += Instr.getOffset();
1362 else
1363 CFAOffset = Instr.getOffset();
1364
1365 Streamer.emitULEB128IntValue(CFAOffset);
1366
1367 return;
1368 }
1369 case MCCFIInstruction::OpDefCfa: {
1370 unsigned Reg = Instr.getRegister();
1371 if (!IsEH)
1372 Reg = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg);
1373 Streamer.emitInt8(dwarf::DW_CFA_def_cfa);
1374 Streamer.emitULEB128IntValue(Reg);
1375 CFAOffset = Instr.getOffset();
1376 Streamer.emitULEB128IntValue(CFAOffset);
1377
1378 return;
1379 }
1380 case MCCFIInstruction::OpDefCfaRegister: {
1381 unsigned Reg = Instr.getRegister();
1382 if (!IsEH)
1383 Reg = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg);
1384 Streamer.emitInt8(dwarf::DW_CFA_def_cfa_register);
1385 Streamer.emitULEB128IntValue(Reg);
1386
1387 return;
1388 }
1389 // TODO: Implement `_sf` variants if/when they need to be emitted.
1390 case MCCFIInstruction::OpLLVMDefAspaceCfa: {
1391 unsigned Reg = Instr.getRegister();
1392 if (!IsEH)
1393 Reg = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg);
1394 Streamer.emitIntValue(dwarf::DW_CFA_LLVM_def_aspace_cfa, 1);
1395 Streamer.emitULEB128IntValue(Reg);
1396 CFAOffset = Instr.getOffset();
1397 Streamer.emitULEB128IntValue(CFAOffset);
1398 Streamer.emitULEB128IntValue(Instr.getAddressSpace());
1399
1400 return;
1401 }
1402 case MCCFIInstruction::OpOffset:
1403 case MCCFIInstruction::OpRelOffset: {
1404 const bool IsRelative =
1405 Instr.getOperation() == MCCFIInstruction::OpRelOffset;
1406
1407 unsigned Reg = Instr.getRegister();
1408 if (!IsEH)
1409 Reg = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg);
1410
1411 int Offset = Instr.getOffset();
1412 if (IsRelative)
1413 Offset -= CFAOffset;
1414 Offset = Offset / dataAlignmentFactor;
1415
1416 if (Offset < 0) {
1417 Streamer.emitInt8(dwarf::DW_CFA_offset_extended_sf);
1418 Streamer.emitULEB128IntValue(Reg);
1419 Streamer.emitSLEB128IntValue(Offset);
1420 } else if (Reg < 64) {
1421 Streamer.emitInt8(dwarf::DW_CFA_offset + Reg);
1422 Streamer.emitULEB128IntValue(Offset);
1423 } else {
1424 Streamer.emitInt8(dwarf::DW_CFA_offset_extended);
1425 Streamer.emitULEB128IntValue(Reg);
1426 Streamer.emitULEB128IntValue(Offset);
1427 }
1428 return;
1429 }
1430 case MCCFIInstruction::OpRememberState:
1431 Streamer.emitInt8(dwarf::DW_CFA_remember_state);
1432 return;
1433 case MCCFIInstruction::OpRestoreState:
1434 Streamer.emitInt8(dwarf::DW_CFA_restore_state);
1435 return;
1436 case MCCFIInstruction::OpSameValue: {
1437 unsigned Reg = Instr.getRegister();
1438 Streamer.emitInt8(dwarf::DW_CFA_same_value);
1439 Streamer.emitULEB128IntValue(Reg);
1440 return;
1441 }
1442 case MCCFIInstruction::OpRestore: {
1443 unsigned Reg = Instr.getRegister();
1444 if (!IsEH)
1445 Reg = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg);
1446 if (Reg < 64) {
1447 Streamer.emitInt8(dwarf::DW_CFA_restore | Reg);
1448 } else {
1449 Streamer.emitInt8(dwarf::DW_CFA_restore_extended);
1450 Streamer.emitULEB128IntValue(Reg);
1451 }
1452 return;
1453 }
1454 case MCCFIInstruction::OpGnuArgsSize:
1455 Streamer.emitInt8(dwarf::DW_CFA_GNU_args_size);
1456 Streamer.emitULEB128IntValue(Instr.getOffset());
1457 return;
1458
1459 case MCCFIInstruction::OpEscape:
1460 Streamer.emitBytes(Instr.getValues());
1461 return;
1462 }
1463 llvm_unreachable("Unhandled case in switch");
1464 }
1465
1466 /// Emit frame instructions to describe the layout of the frame.
emitCFIInstructions(ArrayRef<MCCFIInstruction> Instrs,MCSymbol * BaseLabel)1467 void FrameEmitterImpl::emitCFIInstructions(ArrayRef<MCCFIInstruction> Instrs,
1468 MCSymbol *BaseLabel) {
1469 for (const MCCFIInstruction &Instr : Instrs) {
1470 MCSymbol *Label = Instr.getLabel();
1471 // Throw out move if the label is invalid.
1472 if (Label && !Label->isDefined()) continue; // Not emitted, in dead code.
1473
1474 // Advance row if new location.
1475 if (BaseLabel && Label) {
1476 MCSymbol *ThisSym = Label;
1477 if (ThisSym != BaseLabel) {
1478 Streamer.emitDwarfAdvanceFrameAddr(BaseLabel, ThisSym, Instr.getLoc());
1479 BaseLabel = ThisSym;
1480 }
1481 }
1482
1483 emitCFIInstruction(Instr);
1484 }
1485 }
1486
1487 /// Emit the unwind information in a compact way.
EmitCompactUnwind(const MCDwarfFrameInfo & Frame)1488 void FrameEmitterImpl::EmitCompactUnwind(const MCDwarfFrameInfo &Frame) {
1489 MCContext &Context = Streamer.getContext();
1490 const MCObjectFileInfo *MOFI = Context.getObjectFileInfo();
1491
1492 // range-start range-length compact-unwind-enc personality-func lsda
1493 // _foo LfooEnd-_foo 0x00000023 0 0
1494 // _bar LbarEnd-_bar 0x00000025 __gxx_personality except_tab1
1495 //
1496 // .section __LD,__compact_unwind,regular,debug
1497 //
1498 // # compact unwind for _foo
1499 // .quad _foo
1500 // .set L1,LfooEnd-_foo
1501 // .long L1
1502 // .long 0x01010001
1503 // .quad 0
1504 // .quad 0
1505 //
1506 // # compact unwind for _bar
1507 // .quad _bar
1508 // .set L2,LbarEnd-_bar
1509 // .long L2
1510 // .long 0x01020011
1511 // .quad __gxx_personality
1512 // .quad except_tab1
1513
1514 uint32_t Encoding = Frame.CompactUnwindEncoding;
1515 if (!Encoding) return;
1516 bool DwarfEHFrameOnly = (Encoding == MOFI->getCompactUnwindDwarfEHFrameOnly());
1517
1518 // The encoding needs to know we have an LSDA.
1519 if (!DwarfEHFrameOnly && Frame.Lsda)
1520 Encoding |= 0x40000000;
1521
1522 // Range Start
1523 unsigned FDEEncoding = MOFI->getFDEEncoding();
1524 unsigned Size = getSizeForEncoding(Streamer, FDEEncoding);
1525 Streamer.emitSymbolValue(Frame.Begin, Size);
1526
1527 // Range Length
1528 const MCExpr *Range =
1529 makeEndMinusStartExpr(Context, *Frame.Begin, *Frame.End, 0);
1530 emitAbsValue(Streamer, Range, 4);
1531
1532 // Compact Encoding
1533 Size = getSizeForEncoding(Streamer, dwarf::DW_EH_PE_udata4);
1534 Streamer.emitIntValue(Encoding, Size);
1535
1536 // Personality Function
1537 Size = getSizeForEncoding(Streamer, dwarf::DW_EH_PE_absptr);
1538 if (!DwarfEHFrameOnly && Frame.Personality)
1539 Streamer.emitSymbolValue(Frame.Personality, Size);
1540 else
1541 Streamer.emitIntValue(0, Size); // No personality fn
1542
1543 // LSDA
1544 Size = getSizeForEncoding(Streamer, Frame.LsdaEncoding);
1545 if (!DwarfEHFrameOnly && Frame.Lsda)
1546 Streamer.emitSymbolValue(Frame.Lsda, Size);
1547 else
1548 Streamer.emitIntValue(0, Size); // No LSDA
1549 }
1550
getCIEVersion(bool IsEH,unsigned DwarfVersion)1551 static unsigned getCIEVersion(bool IsEH, unsigned DwarfVersion) {
1552 if (IsEH)
1553 return 1;
1554 switch (DwarfVersion) {
1555 case 2:
1556 return 1;
1557 case 3:
1558 return 3;
1559 case 4:
1560 case 5:
1561 return 4;
1562 }
1563 llvm_unreachable("Unknown version");
1564 }
1565
EmitCIE(const MCDwarfFrameInfo & Frame)1566 const MCSymbol &FrameEmitterImpl::EmitCIE(const MCDwarfFrameInfo &Frame) {
1567 MCContext &context = Streamer.getContext();
1568 const MCRegisterInfo *MRI = context.getRegisterInfo();
1569 const MCObjectFileInfo *MOFI = context.getObjectFileInfo();
1570
1571 MCSymbol *sectionStart = context.createTempSymbol();
1572 Streamer.emitLabel(sectionStart);
1573
1574 MCSymbol *sectionEnd = context.createTempSymbol();
1575
1576 dwarf::DwarfFormat Format = IsEH ? dwarf::DWARF32 : context.getDwarfFormat();
1577 unsigned UnitLengthBytes = dwarf::getUnitLengthFieldByteSize(Format);
1578 unsigned OffsetSize = dwarf::getDwarfOffsetByteSize(Format);
1579 bool IsDwarf64 = Format == dwarf::DWARF64;
1580
1581 if (IsDwarf64)
1582 // DWARF64 mark
1583 Streamer.emitInt32(dwarf::DW_LENGTH_DWARF64);
1584
1585 // Length
1586 const MCExpr *Length = makeEndMinusStartExpr(context, *sectionStart,
1587 *sectionEnd, UnitLengthBytes);
1588 emitAbsValue(Streamer, Length, OffsetSize);
1589
1590 // CIE ID
1591 uint64_t CIE_ID =
1592 IsEH ? 0 : (IsDwarf64 ? dwarf::DW64_CIE_ID : dwarf::DW_CIE_ID);
1593 Streamer.emitIntValue(CIE_ID, OffsetSize);
1594
1595 // Version
1596 uint8_t CIEVersion = getCIEVersion(IsEH, context.getDwarfVersion());
1597 Streamer.emitInt8(CIEVersion);
1598
1599 if (IsEH) {
1600 SmallString<8> Augmentation;
1601 Augmentation += "z";
1602 if (Frame.Personality)
1603 Augmentation += "P";
1604 if (Frame.Lsda)
1605 Augmentation += "L";
1606 Augmentation += "R";
1607 if (Frame.IsSignalFrame)
1608 Augmentation += "S";
1609 if (Frame.IsBKeyFrame)
1610 Augmentation += "B";
1611 if (Frame.IsMTETaggedFrame)
1612 Augmentation += "G";
1613 Streamer.emitBytes(Augmentation);
1614 }
1615 Streamer.emitInt8(0);
1616
1617 if (CIEVersion >= 4) {
1618 // Address Size
1619 Streamer.emitInt8(context.getAsmInfo()->getCodePointerSize());
1620
1621 // Segment Descriptor Size
1622 Streamer.emitInt8(0);
1623 }
1624
1625 // Code Alignment Factor
1626 Streamer.emitULEB128IntValue(context.getAsmInfo()->getMinInstAlignment());
1627
1628 // Data Alignment Factor
1629 Streamer.emitSLEB128IntValue(getDataAlignmentFactor(Streamer));
1630
1631 // Return Address Register
1632 unsigned RAReg = Frame.RAReg;
1633 if (RAReg == static_cast<unsigned>(INT_MAX))
1634 RAReg = MRI->getDwarfRegNum(MRI->getRARegister(), IsEH);
1635
1636 if (CIEVersion == 1) {
1637 assert(RAReg <= 255 &&
1638 "DWARF 2 encodes return_address_register in one byte");
1639 Streamer.emitInt8(RAReg);
1640 } else {
1641 Streamer.emitULEB128IntValue(RAReg);
1642 }
1643
1644 // Augmentation Data Length (optional)
1645 unsigned augmentationLength = 0;
1646 if (IsEH) {
1647 if (Frame.Personality) {
1648 // Personality Encoding
1649 augmentationLength += 1;
1650 // Personality
1651 augmentationLength +=
1652 getSizeForEncoding(Streamer, Frame.PersonalityEncoding);
1653 }
1654 if (Frame.Lsda)
1655 augmentationLength += 1;
1656 // Encoding of the FDE pointers
1657 augmentationLength += 1;
1658
1659 Streamer.emitULEB128IntValue(augmentationLength);
1660
1661 // Augmentation Data (optional)
1662 if (Frame.Personality) {
1663 // Personality Encoding
1664 emitEncodingByte(Streamer, Frame.PersonalityEncoding);
1665 // Personality
1666 EmitPersonality(Streamer, *Frame.Personality, Frame.PersonalityEncoding);
1667 }
1668
1669 if (Frame.Lsda)
1670 emitEncodingByte(Streamer, Frame.LsdaEncoding);
1671
1672 // Encoding of the FDE pointers
1673 emitEncodingByte(Streamer, MOFI->getFDEEncoding());
1674 }
1675
1676 // Initial Instructions
1677
1678 const MCAsmInfo *MAI = context.getAsmInfo();
1679 if (!Frame.IsSimple) {
1680 const std::vector<MCCFIInstruction> &Instructions =
1681 MAI->getInitialFrameState();
1682 emitCFIInstructions(Instructions, nullptr);
1683 }
1684
1685 InitialCFAOffset = CFAOffset;
1686
1687 // Padding
1688 Streamer.emitValueToAlignment(Align(IsEH ? 4 : MAI->getCodePointerSize()));
1689
1690 Streamer.emitLabel(sectionEnd);
1691 return *sectionStart;
1692 }
1693
EmitFDE(const MCSymbol & cieStart,const MCDwarfFrameInfo & frame,bool LastInSection,const MCSymbol & SectionStart)1694 void FrameEmitterImpl::EmitFDE(const MCSymbol &cieStart,
1695 const MCDwarfFrameInfo &frame,
1696 bool LastInSection,
1697 const MCSymbol &SectionStart) {
1698 MCContext &context = Streamer.getContext();
1699 MCSymbol *fdeStart = context.createTempSymbol();
1700 MCSymbol *fdeEnd = context.createTempSymbol();
1701 const MCObjectFileInfo *MOFI = context.getObjectFileInfo();
1702
1703 CFAOffset = InitialCFAOffset;
1704
1705 dwarf::DwarfFormat Format = IsEH ? dwarf::DWARF32 : context.getDwarfFormat();
1706 unsigned OffsetSize = dwarf::getDwarfOffsetByteSize(Format);
1707
1708 if (Format == dwarf::DWARF64)
1709 // DWARF64 mark
1710 Streamer.emitInt32(dwarf::DW_LENGTH_DWARF64);
1711
1712 // Length
1713 const MCExpr *Length = makeEndMinusStartExpr(context, *fdeStart, *fdeEnd, 0);
1714 emitAbsValue(Streamer, Length, OffsetSize);
1715
1716 Streamer.emitLabel(fdeStart);
1717
1718 // CIE Pointer
1719 const MCAsmInfo *asmInfo = context.getAsmInfo();
1720 if (IsEH) {
1721 const MCExpr *offset =
1722 makeEndMinusStartExpr(context, cieStart, *fdeStart, 0);
1723 emitAbsValue(Streamer, offset, OffsetSize);
1724 } else if (!asmInfo->doesDwarfUseRelocationsAcrossSections()) {
1725 const MCExpr *offset =
1726 makeEndMinusStartExpr(context, SectionStart, cieStart, 0);
1727 emitAbsValue(Streamer, offset, OffsetSize);
1728 } else {
1729 Streamer.emitSymbolValue(&cieStart, OffsetSize,
1730 asmInfo->needsDwarfSectionOffsetDirective());
1731 }
1732
1733 // PC Begin
1734 unsigned PCEncoding =
1735 IsEH ? MOFI->getFDEEncoding() : (unsigned)dwarf::DW_EH_PE_absptr;
1736 unsigned PCSize = getSizeForEncoding(Streamer, PCEncoding);
1737 emitFDESymbol(Streamer, *frame.Begin, PCEncoding, IsEH);
1738
1739 // PC Range
1740 const MCExpr *Range =
1741 makeEndMinusStartExpr(context, *frame.Begin, *frame.End, 0);
1742 emitAbsValue(Streamer, Range, PCSize);
1743
1744 if (IsEH) {
1745 // Augmentation Data Length
1746 unsigned augmentationLength = 0;
1747
1748 if (frame.Lsda)
1749 augmentationLength += getSizeForEncoding(Streamer, frame.LsdaEncoding);
1750
1751 Streamer.emitULEB128IntValue(augmentationLength);
1752
1753 // Augmentation Data
1754 if (frame.Lsda)
1755 emitFDESymbol(Streamer, *frame.Lsda, frame.LsdaEncoding, true);
1756 }
1757
1758 // Call Frame Instructions
1759 emitCFIInstructions(frame.Instructions, frame.Begin);
1760
1761 // Padding
1762 // The size of a .eh_frame section has to be a multiple of the alignment
1763 // since a null CIE is interpreted as the end. Old systems overaligned
1764 // .eh_frame, so we do too and account for it in the last FDE.
1765 unsigned Alignment = LastInSection ? asmInfo->getCodePointerSize() : PCSize;
1766 Streamer.emitValueToAlignment(Align(Alignment));
1767
1768 Streamer.emitLabel(fdeEnd);
1769 }
1770
1771 namespace {
1772
1773 struct CIEKey {
getEmptyKey__anon862085bb0311::CIEKey1774 static const CIEKey getEmptyKey() {
1775 return CIEKey(nullptr, 0, -1, false, false, static_cast<unsigned>(INT_MAX),
1776 false, false);
1777 }
1778
getTombstoneKey__anon862085bb0311::CIEKey1779 static const CIEKey getTombstoneKey() {
1780 return CIEKey(nullptr, -1, 0, false, false, static_cast<unsigned>(INT_MAX),
1781 false, false);
1782 }
1783
CIEKey__anon862085bb0311::CIEKey1784 CIEKey(const MCSymbol *Personality, unsigned PersonalityEncoding,
1785 unsigned LSDAEncoding, bool IsSignalFrame, bool IsSimple,
1786 unsigned RAReg, bool IsBKeyFrame, bool IsMTETaggedFrame)
1787 : Personality(Personality), PersonalityEncoding(PersonalityEncoding),
1788 LsdaEncoding(LSDAEncoding), IsSignalFrame(IsSignalFrame),
1789 IsSimple(IsSimple), RAReg(RAReg), IsBKeyFrame(IsBKeyFrame),
1790 IsMTETaggedFrame(IsMTETaggedFrame) {}
1791
CIEKey__anon862085bb0311::CIEKey1792 explicit CIEKey(const MCDwarfFrameInfo &Frame)
1793 : Personality(Frame.Personality),
1794 PersonalityEncoding(Frame.PersonalityEncoding),
1795 LsdaEncoding(Frame.LsdaEncoding), IsSignalFrame(Frame.IsSignalFrame),
1796 IsSimple(Frame.IsSimple), RAReg(Frame.RAReg),
1797 IsBKeyFrame(Frame.IsBKeyFrame),
1798 IsMTETaggedFrame(Frame.IsMTETaggedFrame) {}
1799
PersonalityName__anon862085bb0311::CIEKey1800 StringRef PersonalityName() const {
1801 if (!Personality)
1802 return StringRef();
1803 return Personality->getName();
1804 }
1805
operator <__anon862085bb0311::CIEKey1806 bool operator<(const CIEKey &Other) const {
1807 return std::make_tuple(PersonalityName(), PersonalityEncoding, LsdaEncoding,
1808 IsSignalFrame, IsSimple, RAReg, IsBKeyFrame,
1809 IsMTETaggedFrame) <
1810 std::make_tuple(Other.PersonalityName(), Other.PersonalityEncoding,
1811 Other.LsdaEncoding, Other.IsSignalFrame,
1812 Other.IsSimple, Other.RAReg, Other.IsBKeyFrame,
1813 Other.IsMTETaggedFrame);
1814 }
1815
1816 const MCSymbol *Personality;
1817 unsigned PersonalityEncoding;
1818 unsigned LsdaEncoding;
1819 bool IsSignalFrame;
1820 bool IsSimple;
1821 unsigned RAReg;
1822 bool IsBKeyFrame;
1823 bool IsMTETaggedFrame;
1824 };
1825
1826 } // end anonymous namespace
1827
1828 namespace llvm {
1829
1830 template <> struct DenseMapInfo<CIEKey> {
getEmptyKeyllvm::DenseMapInfo1831 static CIEKey getEmptyKey() { return CIEKey::getEmptyKey(); }
getTombstoneKeyllvm::DenseMapInfo1832 static CIEKey getTombstoneKey() { return CIEKey::getTombstoneKey(); }
1833
getHashValuellvm::DenseMapInfo1834 static unsigned getHashValue(const CIEKey &Key) {
1835 return static_cast<unsigned>(
1836 hash_combine(Key.Personality, Key.PersonalityEncoding, Key.LsdaEncoding,
1837 Key.IsSignalFrame, Key.IsSimple, Key.RAReg,
1838 Key.IsBKeyFrame, Key.IsMTETaggedFrame));
1839 }
1840
isEqualllvm::DenseMapInfo1841 static bool isEqual(const CIEKey &LHS, const CIEKey &RHS) {
1842 return LHS.Personality == RHS.Personality &&
1843 LHS.PersonalityEncoding == RHS.PersonalityEncoding &&
1844 LHS.LsdaEncoding == RHS.LsdaEncoding &&
1845 LHS.IsSignalFrame == RHS.IsSignalFrame &&
1846 LHS.IsSimple == RHS.IsSimple && LHS.RAReg == RHS.RAReg &&
1847 LHS.IsBKeyFrame == RHS.IsBKeyFrame &&
1848 LHS.IsMTETaggedFrame == RHS.IsMTETaggedFrame;
1849 }
1850 };
1851
1852 } // end namespace llvm
1853
Emit(MCObjectStreamer & Streamer,MCAsmBackend * MAB,bool IsEH)1854 void MCDwarfFrameEmitter::Emit(MCObjectStreamer &Streamer, MCAsmBackend *MAB,
1855 bool IsEH) {
1856 MCContext &Context = Streamer.getContext();
1857 const MCObjectFileInfo *MOFI = Context.getObjectFileInfo();
1858 const MCAsmInfo *AsmInfo = Context.getAsmInfo();
1859 FrameEmitterImpl Emitter(IsEH, Streamer);
1860 ArrayRef<MCDwarfFrameInfo> FrameArray = Streamer.getDwarfFrameInfos();
1861
1862 // Emit the compact unwind info if available.
1863 bool NeedsEHFrameSection = !MOFI->getSupportsCompactUnwindWithoutEHFrame();
1864 if (IsEH && MOFI->getCompactUnwindSection()) {
1865 Streamer.generateCompactUnwindEncodings(MAB);
1866 bool SectionEmitted = false;
1867 for (const MCDwarfFrameInfo &Frame : FrameArray) {
1868 if (Frame.CompactUnwindEncoding == 0) continue;
1869 if (!SectionEmitted) {
1870 Streamer.switchSection(MOFI->getCompactUnwindSection());
1871 Streamer.emitValueToAlignment(Align(AsmInfo->getCodePointerSize()));
1872 SectionEmitted = true;
1873 }
1874 NeedsEHFrameSection |=
1875 Frame.CompactUnwindEncoding ==
1876 MOFI->getCompactUnwindDwarfEHFrameOnly();
1877 Emitter.EmitCompactUnwind(Frame);
1878 }
1879 }
1880
1881 // Compact unwind information can be emitted in the eh_frame section or the
1882 // debug_frame section. Skip emitting FDEs and CIEs when the compact unwind
1883 // doesn't need an eh_frame section and the emission location is the eh_frame
1884 // section.
1885 if (!NeedsEHFrameSection && IsEH) return;
1886
1887 MCSection &Section =
1888 IsEH ? *const_cast<MCObjectFileInfo *>(MOFI)->getEHFrameSection()
1889 : *MOFI->getDwarfFrameSection();
1890
1891 Streamer.switchSection(&Section);
1892 MCSymbol *SectionStart = Context.createTempSymbol();
1893 Streamer.emitLabel(SectionStart);
1894
1895 DenseMap<CIEKey, const MCSymbol *> CIEStarts;
1896
1897 const MCSymbol *DummyDebugKey = nullptr;
1898 bool CanOmitDwarf = MOFI->getOmitDwarfIfHaveCompactUnwind();
1899 // Sort the FDEs by their corresponding CIE before we emit them.
1900 // This isn't technically necessary according to the DWARF standard,
1901 // but the Android libunwindstack rejects eh_frame sections where
1902 // an FDE refers to a CIE other than the closest previous CIE.
1903 std::vector<MCDwarfFrameInfo> FrameArrayX(FrameArray.begin(), FrameArray.end());
1904 llvm::stable_sort(FrameArrayX,
1905 [](const MCDwarfFrameInfo &X, const MCDwarfFrameInfo &Y) {
1906 return CIEKey(X) < CIEKey(Y);
1907 });
1908 for (auto I = FrameArrayX.begin(), E = FrameArrayX.end(); I != E;) {
1909 const MCDwarfFrameInfo &Frame = *I;
1910 ++I;
1911 if (CanOmitDwarf && Frame.CompactUnwindEncoding !=
1912 MOFI->getCompactUnwindDwarfEHFrameOnly() && IsEH)
1913 // CIEs and FDEs can be emitted in either the eh_frame section or the
1914 // debug_frame section, on some platforms (e.g. AArch64) the target object
1915 // file supports emitting a compact_unwind section without an associated
1916 // eh_frame section. If the eh_frame section is not needed, and the
1917 // location where the CIEs and FDEs are to be emitted is the eh_frame
1918 // section, do not emit anything.
1919 continue;
1920
1921 CIEKey Key(Frame);
1922 const MCSymbol *&CIEStart = IsEH ? CIEStarts[Key] : DummyDebugKey;
1923 if (!CIEStart)
1924 CIEStart = &Emitter.EmitCIE(Frame);
1925
1926 Emitter.EmitFDE(*CIEStart, Frame, I == E, *SectionStart);
1927 }
1928 }
1929
encodeAdvanceLoc(MCContext & Context,uint64_t AddrDelta,SmallVectorImpl<char> & Out)1930 void MCDwarfFrameEmitter::encodeAdvanceLoc(MCContext &Context,
1931 uint64_t AddrDelta,
1932 SmallVectorImpl<char> &Out) {
1933 // Scale the address delta by the minimum instruction length.
1934 AddrDelta = ScaleAddrDelta(Context, AddrDelta);
1935 if (AddrDelta == 0)
1936 return;
1937
1938 llvm::endianness E = Context.getAsmInfo()->isLittleEndian()
1939 ? llvm::endianness::little
1940 : llvm::endianness::big;
1941
1942 if (isUIntN(6, AddrDelta)) {
1943 uint8_t Opcode = dwarf::DW_CFA_advance_loc | AddrDelta;
1944 Out.push_back(Opcode);
1945 } else if (isUInt<8>(AddrDelta)) {
1946 Out.push_back(dwarf::DW_CFA_advance_loc1);
1947 Out.push_back(AddrDelta);
1948 } else if (isUInt<16>(AddrDelta)) {
1949 Out.push_back(dwarf::DW_CFA_advance_loc2);
1950 support::endian::write<uint16_t>(Out, AddrDelta, E);
1951 } else {
1952 assert(isUInt<32>(AddrDelta));
1953 Out.push_back(dwarf::DW_CFA_advance_loc4);
1954 support::endian::write<uint32_t>(Out, AddrDelta, E);
1955 }
1956 }
1957