lib/Target/BPF/BTFDebug.cpp

   1 //===- BTFDebug.cpp - BTF Generator ---------------------------------------===//
   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 support for writing BTF debug info.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "BTFDebug.h"
  14 #include "BPF.h"
  15 #include "BPFCORE.h"
  16 #include "MCTargetDesc/BPFMCTargetDesc.h"
  17 #include "llvm/BinaryFormat/ELF.h"
  18 #include "llvm/CodeGen/AsmPrinter.h"
  19 #include "llvm/CodeGen/MachineModuleInfo.h"
  20 #include "llvm/MC/MCContext.h"
  21 #include "llvm/MC/MCObjectFileInfo.h"
  22 #include "llvm/MC/MCSectionELF.h"
  23 #include "llvm/MC/MCStreamer.h"
  24 #include "llvm/Support/LineIterator.h"
  25
  26 using namespace llvm;
  27
  28 static const char *BTFKindStr[] = {
  29 #define HANDLE_BTF_KIND(ID, NAME) "BTF_KIND_" #NAME,
  30 #include "BTF.def"
  31 };
  32
  33 /// Emit a BTF common type.
  34 void BTFTypeBase::emitType(MCStreamer &OS) {
  35   OS.AddComment(std::string(BTFKindStr[Kind]) + "(id = " + std::to_string(Id) +
  36                 ")");
  37   OS.EmitIntValue(BTFType.NameOff, 4);
  38   OS.AddComment("0x" + Twine::utohexstr(BTFType.Info));
  39   OS.EmitIntValue(BTFType.Info, 4);
  40   OS.EmitIntValue(BTFType.Size, 4);
  41 }
  42
  43 BTFTypeDerived::BTFTypeDerived(const DIDerivedType *DTy, unsigned Tag,
  44                                bool NeedsFixup)
  45     : DTy(DTy), NeedsFixup(NeedsFixup) {
  46   switch (Tag) {
  47   case dwarf::DW_TAG_pointer_type:
  48     Kind = BTF::BTF_KIND_PTR;
  49     break;
  50   case dwarf::DW_TAG_const_type:
  51     Kind = BTF::BTF_KIND_CONST;
  52     break;
  53   case dwarf::DW_TAG_volatile_type:
  54     Kind = BTF::BTF_KIND_VOLATILE;
  55     break;
  56   case dwarf::DW_TAG_typedef:
  57     Kind = BTF::BTF_KIND_TYPEDEF;
  58     break;
  59   case dwarf::DW_TAG_restrict_type:
  60     Kind = BTF::BTF_KIND_RESTRICT;
  61     break;
  62   default:
  63     llvm_unreachable("Unknown DIDerivedType Tag");
  64   }
  65   BTFType.Info = Kind << 24;
  66 }
  67
  68 void BTFTypeDerived::completeType(BTFDebug &BDebug) {
  69   if (IsCompleted)
  70     return;
  71   IsCompleted = true;
  72
  73   BTFType.NameOff = BDebug.addString(DTy->getName());
  74
  75   if (NeedsFixup)
  76     return;
  77
  78   // The base type for PTR/CONST/VOLATILE could be void.
  79   const DIType *ResolvedType = DTy->getBaseType();
  80   if (!ResolvedType) {
  81     assert((Kind == BTF::BTF_KIND_PTR || Kind == BTF::BTF_KIND_CONST ||
  82             Kind == BTF::BTF_KIND_VOLATILE) &&
  83            "Invalid null basetype");
  84     BTFType.Type = 0;
  85   } else {
  86     BTFType.Type = BDebug.getTypeId(ResolvedType);
  87   }
  88 }
  89
  90 void BTFTypeDerived::emitType(MCStreamer &OS) { BTFTypeBase::emitType(OS); }
  91
  92 void BTFTypeDerived::setPointeeType(uint32_t PointeeType) {
  93   BTFType.Type = PointeeType;
  94 }
  95
  96 /// Represent a struct/union forward declaration.
  97 BTFTypeFwd::BTFTypeFwd(StringRef Name, bool IsUnion) : Name(Name) {
  98   Kind = BTF::BTF_KIND_FWD;
  99   BTFType.Info = IsUnion << 31 | Kind << 24;
 100   BTFType.Type = 0;
 101 }
 102
 103 void BTFTypeFwd::completeType(BTFDebug &BDebug) {
 104   if (IsCompleted)
 105     return;
 106   IsCompleted = true;
 107
 108   BTFType.NameOff = BDebug.addString(Name);
 109 }
 110
 111 void BTFTypeFwd::emitType(MCStreamer &OS) { BTFTypeBase::emitType(OS); }
 112
 113 BTFTypeInt::BTFTypeInt(uint32_t Encoding, uint32_t SizeInBits,
 114                        uint32_t OffsetInBits, StringRef TypeName)
 115     : Name(TypeName) {
 116   // Translate IR int encoding to BTF int encoding.
 117   uint8_t BTFEncoding;
 118   switch (Encoding) {
 119   case dwarf::DW_ATE_boolean:
 120     BTFEncoding = BTF::INT_BOOL;
 121     break;
 122   case dwarf::DW_ATE_signed:
 123   case dwarf::DW_ATE_signed_char:
 124     BTFEncoding = BTF::INT_SIGNED;
 125     break;
 126   case dwarf::DW_ATE_unsigned:
 127   case dwarf::DW_ATE_unsigned_char:
 128     BTFEncoding = 0;
 129     break;
 130   default:
 131     llvm_unreachable("Unknown BTFTypeInt Encoding");
 132   }
 133
 134   Kind = BTF::BTF_KIND_INT;
 135   BTFType.Info = Kind << 24;
 136   BTFType.Size = roundupToBytes(SizeInBits);
 137   IntVal = (BTFEncoding << 24) | OffsetInBits << 16 | SizeInBits;
 138 }
 139
 140 void BTFTypeInt::completeType(BTFDebug &BDebug) {
 141   if (IsCompleted)
 142     return;
 143   IsCompleted = true;
 144
 145   BTFType.NameOff = BDebug.addString(Name);
 146 }
 147
 148 void BTFTypeInt::emitType(MCStreamer &OS) {
 149   BTFTypeBase::emitType(OS);
 150   OS.AddComment("0x" + Twine::utohexstr(IntVal));
 151   OS.EmitIntValue(IntVal, 4);
 152 }
 153
 154 BTFTypeEnum::BTFTypeEnum(const DICompositeType *ETy, uint32_t VLen) : ETy(ETy) {
 155   Kind = BTF::BTF_KIND_ENUM;
 156   BTFType.Info = Kind << 24 | VLen;
 157   BTFType.Size = roundupToBytes(ETy->getSizeInBits());
 158 }
 159
 160 void BTFTypeEnum::completeType(BTFDebug &BDebug) {
 161   if (IsCompleted)
 162     return;
 163   IsCompleted = true;
 164
 165   BTFType.NameOff = BDebug.addString(ETy->getName());
 166
 167   DINodeArray Elements = ETy->getElements();
 168   for (const auto Element : Elements) {
 169     const auto *Enum = cast<DIEnumerator>(Element);
 170
 171     struct BTF::BTFEnum BTFEnum;
 172     BTFEnum.NameOff = BDebug.addString(Enum->getName());
 173     // BTF enum value is 32bit, enforce it.
 174     BTFEnum.Val = static_cast<uint32_t>(Enum->getValue());
 175     EnumValues.push_back(BTFEnum);
 176   }
 177 }
 178
 179 void BTFTypeEnum::emitType(MCStreamer &OS) {
 180   BTFTypeBase::emitType(OS);
 181   for (const auto &Enum : EnumValues) {
 182     OS.EmitIntValue(Enum.NameOff, 4);
 183     OS.EmitIntValue(Enum.Val, 4);
 184   }
 185 }
 186
 187 BTFTypeArray::BTFTypeArray(uint32_t ElemTypeId, uint32_t NumElems) {
 188   Kind = BTF::BTF_KIND_ARRAY;
 189   BTFType.NameOff = 0;
 190   BTFType.Info = Kind << 24;
 191   BTFType.Size = 0;
 192
 193   ArrayInfo.ElemType = ElemTypeId;
 194   ArrayInfo.Nelems = NumElems;
 195 }
 196
 197 /// Represent a BTF array.
 198 void BTFTypeArray::completeType(BTFDebug &BDebug) {
 199   if (IsCompleted)
 200     return;
 201   IsCompleted = true;
 202
 203   // The IR does not really have a type for the index.
 204   // A special type for array index should have been
 205   // created during initial type traversal. Just
 206   // retrieve that type id.
 207   ArrayInfo.IndexType = BDebug.getArrayIndexTypeId();
 208 }
 209
 210 void BTFTypeArray::emitType(MCStreamer &OS) {
 211   BTFTypeBase::emitType(OS);
 212   OS.EmitIntValue(ArrayInfo.ElemType, 4);
 213   OS.EmitIntValue(ArrayInfo.IndexType, 4);
 214   OS.EmitIntValue(ArrayInfo.Nelems, 4);
 215 }
 216
 217 /// Represent either a struct or a union.
 218 BTFTypeStruct::BTFTypeStruct(const DICompositeType *STy, bool IsStruct,
 219                              bool HasBitField, uint32_t Vlen)
 220     : STy(STy), HasBitField(HasBitField) {
 221   Kind = IsStruct ? BTF::BTF_KIND_STRUCT : BTF::BTF_KIND_UNION;
 222   BTFType.Size = roundupToBytes(STy->getSizeInBits());
 223   BTFType.Info = (HasBitField << 31) | (Kind << 24) | Vlen;
 224 }
 225
 226 void BTFTypeStruct::completeType(BTFDebug &BDebug) {
 227   if (IsCompleted)
 228     return;
 229   IsCompleted = true;
 230
 231   BTFType.NameOff = BDebug.addString(STy->getName());
 232
 233   // Add struct/union members.
 234   const DINodeArray Elements = STy->getElements();
 235   for (const auto *Element : Elements) {
 236     struct BTF::BTFMember BTFMember;
 237     const auto *DDTy = cast<DIDerivedType>(Element);
 238
 239     BTFMember.NameOff = BDebug.addString(DDTy->getName());
 240     if (HasBitField) {
 241       uint8_t BitFieldSize = DDTy->isBitField() ? DDTy->getSizeInBits() : 0;
 242       BTFMember.Offset = BitFieldSize << 24 | DDTy->getOffsetInBits();
 243     } else {
 244       BTFMember.Offset = DDTy->getOffsetInBits();
 245     }
 246     const auto *BaseTy = DDTy->getBaseType();
 247     BTFMember.Type = BDebug.getTypeId(BaseTy);
 248     Members.push_back(BTFMember);
 249   }
 250 }
 251
 252 void BTFTypeStruct::emitType(MCStreamer &OS) {
 253   BTFTypeBase::emitType(OS);
 254   for (const auto &Member : Members) {
 255     OS.EmitIntValue(Member.NameOff, 4);
 256     OS.EmitIntValue(Member.Type, 4);
 257     OS.AddComment("0x" + Twine::utohexstr(Member.Offset));
 258     OS.EmitIntValue(Member.Offset, 4);
 259   }
 260 }
 261
 262 std::string BTFTypeStruct::getName() { return STy->getName(); }
 263
 264 /// The Func kind represents both subprogram and pointee of function
 265 /// pointers. If the FuncName is empty, it represents a pointee of function
 266 /// pointer. Otherwise, it represents a subprogram. The func arg names
 267 /// are empty for pointee of function pointer case, and are valid names
 268 /// for subprogram.
 269 BTFTypeFuncProto::BTFTypeFuncProto(
 270     const DISubroutineType *STy, uint32_t VLen,
 271     const std::unordered_map<uint32_t, StringRef> &FuncArgNames)
 272     : STy(STy), FuncArgNames(FuncArgNames) {
 273   Kind = BTF::BTF_KIND_FUNC_PROTO;
 274   BTFType.Info = (Kind << 24) | VLen;
 275 }
 276
 277 void BTFTypeFuncProto::completeType(BTFDebug &BDebug) {
 278   if (IsCompleted)
 279     return;
 280   IsCompleted = true;
 281
 282   DITypeRefArray Elements = STy->getTypeArray();
 283   auto RetType = Elements[0];
 284   BTFType.Type = RetType ? BDebug.getTypeId(RetType) : 0;
 285   BTFType.NameOff = 0;
 286
 287   // For null parameter which is typically the last one
 288   // to represent the vararg, encode the NameOff/Type to be 0.
 289   for (unsigned I = 1, N = Elements.size(); I < N; ++I) {
 290     struct BTF::BTFParam Param;
 291     auto Element = Elements[I];
 292     if (Element) {
 293       Param.NameOff = BDebug.addString(FuncArgNames[I]);
 294       Param.Type = BDebug.getTypeId(Element);
 295     } else {
 296       Param.NameOff = 0;
 297       Param.Type = 0;
 298     }
 299     Parameters.push_back(Param);
 300   }
 301 }
 302
 303 void BTFTypeFuncProto::emitType(MCStreamer &OS) {
 304   BTFTypeBase::emitType(OS);
 305   for (const auto &Param : Parameters) {
 306     OS.EmitIntValue(Param.NameOff, 4);
 307     OS.EmitIntValue(Param.Type, 4);
 308   }
 309 }
 310
 311 BTFTypeFunc::BTFTypeFunc(StringRef FuncName, uint32_t ProtoTypeId)
 312     : Name(FuncName) {
 313   Kind = BTF::BTF_KIND_FUNC;
 314   BTFType.Info = Kind << 24;
 315   BTFType.Type = ProtoTypeId;
 316 }
 317
 318 void BTFTypeFunc::completeType(BTFDebug &BDebug) {
 319   if (IsCompleted)
 320     return;
 321   IsCompleted = true;
 322
 323   BTFType.NameOff = BDebug.addString(Name);
 324 }
 325
 326 void BTFTypeFunc::emitType(MCStreamer &OS) { BTFTypeBase::emitType(OS); }
 327
 328 BTFKindVar::BTFKindVar(StringRef VarName, uint32_t TypeId, uint32_t VarInfo)
 329     : Name(VarName) {
 330   Kind = BTF::BTF_KIND_VAR;
 331   BTFType.Info = Kind << 24;
 332   BTFType.Type = TypeId;
 333   Info = VarInfo;
 334 }
 335
 336 void BTFKindVar::completeType(BTFDebug &BDebug) {
 337   BTFType.NameOff = BDebug.addString(Name);
 338 }
 339
 340 void BTFKindVar::emitType(MCStreamer &OS) {
 341   BTFTypeBase::emitType(OS);
 342   OS.EmitIntValue(Info, 4);
 343 }
 344
 345 BTFKindDataSec::BTFKindDataSec(AsmPrinter *AsmPrt, std::string SecName)
 346     : Asm(AsmPrt), Name(SecName) {
 347   Kind = BTF::BTF_KIND_DATASEC;
 348   BTFType.Info = Kind << 24;
 349   BTFType.Size = 0;
 350 }
 351
 352 void BTFKindDataSec::completeType(BTFDebug &BDebug) {
 353   BTFType.NameOff = BDebug.addString(Name);
 354   BTFType.Info |= Vars.size();
 355 }
 356
 357 void BTFKindDataSec::emitType(MCStreamer &OS) {
 358   BTFTypeBase::emitType(OS);
 359
 360   for (const auto &V : Vars) {
 361     OS.EmitIntValue(std::get<0>(V), 4);
 362     Asm->EmitLabelReference(std::get<1>(V), 4);
 363     OS.EmitIntValue(std::get<2>(V), 4);
 364   }
 365 }
 366
 367 uint32_t BTFStringTable::addString(StringRef S) {
 368   // Check whether the string already exists.
 369   for (auto &OffsetM : OffsetToIdMap) {
 370     if (Table[OffsetM.second] == S)
 371       return OffsetM.first;
 372   }
 373   // Not find, add to the string table.
 374   uint32_t Offset = Size;
 375   OffsetToIdMap[Offset] = Table.size();
 376   Table.push_back(S);
 377   Size += S.size() + 1;
 378   return Offset;
 379 }
 380
 381 BTFDebug::BTFDebug(AsmPrinter *AP)
 382     : DebugHandlerBase(AP), OS(*Asm->OutStreamer), SkipInstruction(false),
 383       LineInfoGenerated(false), SecNameOff(0), ArrayIndexTypeId(0),
 384       MapDefNotCollected(true) {
 385   addString("\0");
 386 }
 387
 388 uint32_t BTFDebug::addType(std::unique_ptr<BTFTypeBase> TypeEntry,
 389                            const DIType *Ty) {
 390   TypeEntry->setId(TypeEntries.size() + 1);
 391   uint32_t Id = TypeEntry->getId();
 392   DIToIdMap[Ty] = Id;
 393   TypeEntries.push_back(std::move(TypeEntry));
 394   return Id;
 395 }
 396
 397 uint32_t BTFDebug::addType(std::unique_ptr<BTFTypeBase> TypeEntry) {
 398   TypeEntry->setId(TypeEntries.size() + 1);
 399   uint32_t Id = TypeEntry->getId();
 400   TypeEntries.push_back(std::move(TypeEntry));
 401   return Id;
 402 }
 403
 404 void BTFDebug::visitBasicType(const DIBasicType *BTy, uint32_t &TypeId) {
 405   // Only int types are supported in BTF.
 406   uint32_t Encoding = BTy->getEncoding();
 407   if (Encoding != dwarf::DW_ATE_boolean && Encoding != dwarf::DW_ATE_signed &&
 408       Encoding != dwarf::DW_ATE_signed_char &&
 409       Encoding != dwarf::DW_ATE_unsigned &&
 410       Encoding != dwarf::DW_ATE_unsigned_char)
 411     return;
 412
 413   // Create a BTF type instance for this DIBasicType and put it into
 414   // DIToIdMap for cross-type reference check.
 415   auto TypeEntry = std::make_unique<BTFTypeInt>(
 416       Encoding, BTy->getSizeInBits(), BTy->getOffsetInBits(), BTy->getName());
 417   TypeId = addType(std::move(TypeEntry), BTy);
 418 }
 419
 420 /// Handle subprogram or subroutine types.
 421 void BTFDebug::visitSubroutineType(
 422     const DISubroutineType *STy, bool ForSubprog,
 423     const std::unordered_map<uint32_t, StringRef> &FuncArgNames,
 424     uint32_t &TypeId) {
 425   DITypeRefArray Elements = STy->getTypeArray();
 426   uint32_t VLen = Elements.size() - 1;
 427   if (VLen > BTF::MAX_VLEN)
 428     return;
 429
 430   // Subprogram has a valid non-zero-length name, and the pointee of
 431   // a function pointer has an empty name. The subprogram type will
 432   // not be added to DIToIdMap as it should not be referenced by
 433   // any other types.
 434   auto TypeEntry = std::make_unique<BTFTypeFuncProto>(STy, VLen, FuncArgNames);
 435   if (ForSubprog)
 436     TypeId = addType(std::move(TypeEntry)); // For subprogram
 437   else
 438     TypeId = addType(std::move(TypeEntry), STy); // For func ptr
 439
 440   // Visit return type and func arg types.
 441   for (const auto Element : Elements) {
 442     visitTypeEntry(Element);
 443   }
 444 }
 445
 446 /// Handle structure/union types.
 447 void BTFDebug::visitStructType(const DICompositeType *CTy, bool IsStruct,
 448                                uint32_t &TypeId) {
 449   const DINodeArray Elements = CTy->getElements();
 450   uint32_t VLen = Elements.size();
 451   if (VLen > BTF::MAX_VLEN)
 452     return;
 453
 454   // Check whether we have any bitfield members or not
 455   bool HasBitField = false;
 456   for (const auto *Element : Elements) {
 457     auto E = cast<DIDerivedType>(Element);
 458     if (E->isBitField()) {
 459       HasBitField = true;
 460       break;
 461     }
 462   }
 463
 464   auto TypeEntry =
 465       std::make_unique<BTFTypeStruct>(CTy, IsStruct, HasBitField, VLen);
 466   StructTypes.push_back(TypeEntry.get());
 467   TypeId = addType(std::move(TypeEntry), CTy);
 468
 469   // Visit all struct members.
 470   for (const auto *Element : Elements)
 471     visitTypeEntry(cast<DIDerivedType>(Element));
 472 }
 473
 474 void BTFDebug::visitArrayType(const DICompositeType *CTy, uint32_t &TypeId) {
 475   // Visit array element type.
 476   uint32_t ElemTypeId;
 477   const DIType *ElemType = CTy->getBaseType();
 478   visitTypeEntry(ElemType, ElemTypeId, false, false);
 479
 480   // Visit array dimensions.
 481   DINodeArray Elements = CTy->getElements();
 482   for (int I = Elements.size() - 1; I >= 0; --I) {
 483     if (auto *Element = dyn_cast_or_null<DINode>(Elements[I]))
 484       if (Element->getTag() == dwarf::DW_TAG_subrange_type) {
 485         const DISubrange *SR = cast<DISubrange>(Element);
 486         auto *CI = SR->getCount().dyn_cast<ConstantInt *>();
 487         int64_t Count = CI->getSExtValue();
 488
 489         // For struct s { int b; char c[]; }, the c[] will be represented
 490         // as an array with Count = -1.
 491         auto TypeEntry =
 492             std::make_unique<BTFTypeArray>(ElemTypeId,
 493                 Count >= 0 ? Count : 0);
 494         if (I == 0)
 495           ElemTypeId = addType(std::move(TypeEntry), CTy);
 496         else
 497           ElemTypeId = addType(std::move(TypeEntry));
 498       }
 499   }
 500
 501   // The array TypeId is the type id of the outermost dimension.
 502   TypeId = ElemTypeId;
 503
 504   // The IR does not have a type for array index while BTF wants one.
 505   // So create an array index type if there is none.
 506   if (!ArrayIndexTypeId) {
 507     auto TypeEntry = std::make_unique<BTFTypeInt>(dwarf::DW_ATE_unsigned, 32,
 508                                                    0, "__ARRAY_SIZE_TYPE__");
 509     ArrayIndexTypeId = addType(std::move(TypeEntry));
 510   }
 511 }
 512
 513 void BTFDebug::visitEnumType(const DICompositeType *CTy, uint32_t &TypeId) {
 514   DINodeArray Elements = CTy->getElements();
 515   uint32_t VLen = Elements.size();
 516   if (VLen > BTF::MAX_VLEN)
 517     return;
 518
 519   auto TypeEntry = std::make_unique<BTFTypeEnum>(CTy, VLen);
 520   TypeId = addType(std::move(TypeEntry), CTy);
 521   // No need to visit base type as BTF does not encode it.
 522 }
 523
 524 /// Handle structure/union forward declarations.
 525 void BTFDebug::visitFwdDeclType(const DICompositeType *CTy, bool IsUnion,
 526                                 uint32_t &TypeId) {
 527   auto TypeEntry = std::make_unique<BTFTypeFwd>(CTy->getName(), IsUnion);
 528   TypeId = addType(std::move(TypeEntry), CTy);
 529 }
 530
 531 /// Handle structure, union, array and enumeration types.
 532 void BTFDebug::visitCompositeType(const DICompositeType *CTy,
 533                                   uint32_t &TypeId) {
 534   auto Tag = CTy->getTag();
 535   if (Tag == dwarf::DW_TAG_structure_type || Tag == dwarf::DW_TAG_union_type) {
 536     // Handle forward declaration differently as it does not have members.
 537     if (CTy->isForwardDecl())
 538       visitFwdDeclType(CTy, Tag == dwarf::DW_TAG_union_type, TypeId);
 539     else
 540       visitStructType(CTy, Tag == dwarf::DW_TAG_structure_type, TypeId);
 541   } else if (Tag == dwarf::DW_TAG_array_type)
 542     visitArrayType(CTy, TypeId);
 543   else if (Tag == dwarf::DW_TAG_enumeration_type)
 544     visitEnumType(CTy, TypeId);
 545 }
 546
 547 /// Handle pointer, typedef, const, volatile, restrict and member types.
 548 void BTFDebug::visitDerivedType(const DIDerivedType *DTy, uint32_t &TypeId,
 549                                 bool CheckPointer, bool SeenPointer) {
 550   unsigned Tag = DTy->getTag();
 551
 552   /// Try to avoid chasing pointees, esp. structure pointees which may
 553   /// unnecessary bring in a lot of types.
 554   if (CheckPointer && !SeenPointer) {
 555     SeenPointer = Tag == dwarf::DW_TAG_pointer_type;
 556   }
 557
 558   if (CheckPointer && SeenPointer) {
 559     const DIType *Base = DTy->getBaseType();
 560     if (Base) {
 561       if (const auto *CTy = dyn_cast<DICompositeType>(Base)) {
 562         auto CTag = CTy->getTag();
 563         if ((CTag == dwarf::DW_TAG_structure_type ||
 564              CTag == dwarf::DW_TAG_union_type) &&
 565             !CTy->isForwardDecl()) {
 566           /// Find a candidate, generate a fixup. Later on the struct/union
 567           /// pointee type will be replaced with either a real type or
 568           /// a forward declaration.
 569           auto TypeEntry = std::make_unique<BTFTypeDerived>(DTy, Tag, true);
 570           auto &Fixup = FixupDerivedTypes[CTy->getName()];
 571           Fixup.first = CTag == dwarf::DW_TAG_union_type;
 572           Fixup.second.push_back(TypeEntry.get());
 573           TypeId = addType(std::move(TypeEntry), DTy);
 574           return;
 575         }
 576       }
 577     }
 578   }
 579
 580   if (Tag == dwarf::DW_TAG_pointer_type || Tag == dwarf::DW_TAG_typedef ||
 581       Tag == dwarf::DW_TAG_const_type || Tag == dwarf::DW_TAG_volatile_type ||
 582       Tag == dwarf::DW_TAG_restrict_type) {
 583     auto TypeEntry = std::make_unique<BTFTypeDerived>(DTy, Tag, false);
 584     TypeId = addType(std::move(TypeEntry), DTy);
 585   } else if (Tag != dwarf::DW_TAG_member) {
 586     return;
 587   }
 588
 589   // Visit base type of pointer, typedef, const, volatile, restrict or
 590   // struct/union member.
 591   uint32_t TempTypeId = 0;
 592   if (Tag == dwarf::DW_TAG_member)
 593     visitTypeEntry(DTy->getBaseType(), TempTypeId, true, false);
 594   else
 595     visitTypeEntry(DTy->getBaseType(), TempTypeId, CheckPointer, SeenPointer);
 596 }
 597
 598 void BTFDebug::visitTypeEntry(const DIType *Ty, uint32_t &TypeId,
 599                               bool CheckPointer, bool SeenPointer) {
 600   if (!Ty || DIToIdMap.find(Ty) != DIToIdMap.end()) {
 601     TypeId = DIToIdMap[Ty];
 602     return;
 603   }
 604
 605   if (const auto *BTy = dyn_cast<DIBasicType>(Ty))
 606     visitBasicType(BTy, TypeId);
 607   else if (const auto *STy = dyn_cast<DISubroutineType>(Ty))
 608     visitSubroutineType(STy, false, std::unordered_map<uint32_t, StringRef>(),
 609                         TypeId);
 610   else if (const auto *CTy = dyn_cast<DICompositeType>(Ty))
 611     visitCompositeType(CTy, TypeId);
 612   else if (const auto *DTy = dyn_cast<DIDerivedType>(Ty))
 613     visitDerivedType(DTy, TypeId, CheckPointer, SeenPointer);
 614   else
 615     llvm_unreachable("Unknown DIType");
 616 }
 617
 618 void BTFDebug::visitTypeEntry(const DIType *Ty) {
 619   uint32_t TypeId;
 620   visitTypeEntry(Ty, TypeId, false, false);
 621 }
 622
 623 void BTFDebug::visitMapDefType(const DIType *Ty, uint32_t &TypeId) {
 624   if (!Ty || DIToIdMap.find(Ty) != DIToIdMap.end()) {
 625     TypeId = DIToIdMap[Ty];
 626     return;
 627   }
 628
 629   // MapDef type is a struct type
 630   const auto *CTy = dyn_cast<DICompositeType>(Ty);
 631   if (!CTy)
 632     return;
 633
 634   auto Tag = CTy->getTag();
 635   if (Tag != dwarf::DW_TAG_structure_type || CTy->isForwardDecl())
 636     return;
 637
 638   // Record this type
 639   const DINodeArray Elements = CTy->getElements();
 640   bool HasBitField = false;
 641   for (const auto *Element : Elements) {
 642     auto E = cast<DIDerivedType>(Element);
 643     if (E->isBitField()) {
 644       HasBitField = true;
 645       break;
 646     }
 647   }
 648
 649   auto TypeEntry =
 650       std::make_unique<BTFTypeStruct>(CTy, true, HasBitField, Elements.size());
 651   StructTypes.push_back(TypeEntry.get());
 652   TypeId = addType(std::move(TypeEntry), CTy);
 653
 654   // Visit all struct members
 655   for (const auto *Element : Elements) {
 656     const auto *MemberType = cast<DIDerivedType>(Element);
 657     visitTypeEntry(MemberType->getBaseType());
 658   }
 659 }
 660
 661 /// Read file contents from the actual file or from the source
 662 std::string BTFDebug::populateFileContent(const DISubprogram *SP) {
 663   auto File = SP->getFile();
 664   std::string FileName;
 665
 666   if (!File->getFilename().startswith("/") && File->getDirectory().size())
 667     FileName = File->getDirectory().str() + "/" + File->getFilename().str();
 668   else
 669     FileName = File->getFilename();
 670
 671   // No need to populate the contends if it has been populated!
 672   if (FileContent.find(FileName) != FileContent.end())
 673     return FileName;
 674
 675   std::vector<std::string> Content;
 676   std::string Line;
 677   Content.push_back(Line); // Line 0 for empty string
 678
 679   std::unique_ptr<MemoryBuffer> Buf;
 680   auto Source = File->getSource();
 681   if (Source)
 682     Buf = MemoryBuffer::getMemBufferCopy(*Source);
 683   else if (ErrorOr<std::unique_ptr<MemoryBuffer>> BufOrErr =
 684                MemoryBuffer::getFile(FileName))
 685     Buf = std::move(*BufOrErr);
 686   if (Buf)
 687     for (line_iterator I(*Buf, false), E; I != E; ++I)
 688       Content.push_back(*I);
 689
 690   FileContent[FileName] = Content;
 691   return FileName;
 692 }
 693
 694 void BTFDebug::constructLineInfo(const DISubprogram *SP, MCSymbol *Label,
 695                                  uint32_t Line, uint32_t Column) {
 696   std::string FileName = populateFileContent(SP);
 697   BTFLineInfo LineInfo;
 698
 699   LineInfo.Label = Label;
 700   LineInfo.FileNameOff = addString(FileName);
 701   // If file content is not available, let LineOff = 0.
 702   if (Line < FileContent[FileName].size())
 703     LineInfo.LineOff = addString(FileContent[FileName][Line]);
 704   else
 705     LineInfo.LineOff = 0;
 706   LineInfo.LineNum = Line;
 707   LineInfo.ColumnNum = Column;
 708   LineInfoTable[SecNameOff].push_back(LineInfo);
 709 }
 710
 711 void BTFDebug::emitCommonHeader() {
 712   OS.AddComment("0x" + Twine::utohexstr(BTF::MAGIC));
 713   OS.EmitIntValue(BTF::MAGIC, 2);
 714   OS.EmitIntValue(BTF::VERSION, 1);
 715   OS.EmitIntValue(0, 1);
 716 }
 717
 718 void BTFDebug::emitBTFSection() {
 719   // Do not emit section if no types and only "" string.
 720   if (!TypeEntries.size() && StringTable.getSize() == 1)
 721     return;
 722
 723   MCContext &Ctx = OS.getContext();
 724   OS.SwitchSection(Ctx.getELFSection(".BTF", ELF::SHT_PROGBITS, 0));
 725
 726   // Emit header.
 727   emitCommonHeader();
 728   OS.EmitIntValue(BTF::HeaderSize, 4);
 729
 730   uint32_t TypeLen = 0, StrLen;
 731   for (const auto &TypeEntry : TypeEntries)
 732     TypeLen += TypeEntry->getSize();
 733   StrLen = StringTable.getSize();
 734
 735   OS.EmitIntValue(0, 4);
 736   OS.EmitIntValue(TypeLen, 4);
 737   OS.EmitIntValue(TypeLen, 4);
 738   OS.EmitIntValue(StrLen, 4);
 739
 740   // Emit type table.
 741   for (const auto &TypeEntry : TypeEntries)
 742     TypeEntry->emitType(OS);
 743
 744   // Emit string table.
 745   uint32_t StringOffset = 0;
 746   for (const auto &S : StringTable.getTable()) {
 747     OS.AddComment("string offset=" + std::to_string(StringOffset));
 748     OS.EmitBytes(S);
 749     OS.EmitBytes(StringRef("\0", 1));
 750     StringOffset += S.size() + 1;
 751   }
 752 }
 753
 754 void BTFDebug::emitBTFExtSection() {
 755   // Do not emit section if empty FuncInfoTable and LineInfoTable.
 756   if (!FuncInfoTable.size() && !LineInfoTable.size() &&
 757       !FieldRelocTable.size() && !ExternRelocTable.size())
 758     return;
 759
 760   MCContext &Ctx = OS.getContext();
 761   OS.SwitchSection(Ctx.getELFSection(".BTF.ext", ELF::SHT_PROGBITS, 0));
 762
 763   // Emit header.
 764   emitCommonHeader();
 765   OS.EmitIntValue(BTF::ExtHeaderSize, 4);
 766
 767   // Account for FuncInfo/LineInfo record size as well.
 768   uint32_t FuncLen = 4, LineLen = 4;
 769   // Do not account for optional FieldReloc/ExternReloc.
 770   uint32_t FieldRelocLen = 0, ExternRelocLen = 0;
 771   for (const auto &FuncSec : FuncInfoTable) {
 772     FuncLen += BTF::SecFuncInfoSize;
 773     FuncLen += FuncSec.second.size() * BTF::BPFFuncInfoSize;
 774   }
 775   for (const auto &LineSec : LineInfoTable) {
 776     LineLen += BTF::SecLineInfoSize;
 777     LineLen += LineSec.second.size() * BTF::BPFLineInfoSize;
 778   }
 779   for (const auto &FieldRelocSec : FieldRelocTable) {
 780     FieldRelocLen += BTF::SecFieldRelocSize;
 781     FieldRelocLen += FieldRelocSec.second.size() * BTF::BPFFieldRelocSize;
 782   }
 783   for (const auto &ExternRelocSec : ExternRelocTable) {
 784     ExternRelocLen += BTF::SecExternRelocSize;
 785     ExternRelocLen += ExternRelocSec.second.size() * BTF::BPFExternRelocSize;
 786   }
 787
 788   if (FieldRelocLen)
 789     FieldRelocLen += 4;
 790   if (ExternRelocLen)
 791     ExternRelocLen += 4;
 792
 793   OS.EmitIntValue(0, 4);
 794   OS.EmitIntValue(FuncLen, 4);
 795   OS.EmitIntValue(FuncLen, 4);
 796   OS.EmitIntValue(LineLen, 4);
 797   OS.EmitIntValue(FuncLen + LineLen, 4);
 798   OS.EmitIntValue(FieldRelocLen, 4);
 799   OS.EmitIntValue(FuncLen + LineLen + FieldRelocLen, 4);
 800   OS.EmitIntValue(ExternRelocLen, 4);
 801
 802   // Emit func_info table.
 803   OS.AddComment("FuncInfo");
 804   OS.EmitIntValue(BTF::BPFFuncInfoSize, 4);
 805   for (const auto &FuncSec : FuncInfoTable) {
 806     OS.AddComment("FuncInfo section string offset=" +
 807                   std::to_string(FuncSec.first));
 808     OS.EmitIntValue(FuncSec.first, 4);
 809     OS.EmitIntValue(FuncSec.second.size(), 4);
 810     for (const auto &FuncInfo : FuncSec.second) {
 811       Asm->EmitLabelReference(FuncInfo.Label, 4);
 812       OS.EmitIntValue(FuncInfo.TypeId, 4);
 813     }
 814   }
 815
 816   // Emit line_info table.
 817   OS.AddComment("LineInfo");
 818   OS.EmitIntValue(BTF::BPFLineInfoSize, 4);
 819   for (const auto &LineSec : LineInfoTable) {
 820     OS.AddComment("LineInfo section string offset=" +
 821                   std::to_string(LineSec.first));
 822     OS.EmitIntValue(LineSec.first, 4);
 823     OS.EmitIntValue(LineSec.second.size(), 4);
 824     for (const auto &LineInfo : LineSec.second) {
 825       Asm->EmitLabelReference(LineInfo.Label, 4);
 826       OS.EmitIntValue(LineInfo.FileNameOff, 4);
 827       OS.EmitIntValue(LineInfo.LineOff, 4);
 828       OS.AddComment("Line " + std::to_string(LineInfo.LineNum) + " Col " +
 829                     std::to_string(LineInfo.ColumnNum));
 830       OS.EmitIntValue(LineInfo.LineNum << 10 | LineInfo.ColumnNum, 4);
 831     }
 832   }
 833
 834   // Emit field reloc table.
 835   if (FieldRelocLen) {
 836     OS.AddComment("FieldReloc");
 837     OS.EmitIntValue(BTF::BPFFieldRelocSize, 4);
 838     for (const auto &FieldRelocSec : FieldRelocTable) {
 839       OS.AddComment("Field reloc section string offset=" +
 840                     std::to_string(FieldRelocSec.first));
 841       OS.EmitIntValue(FieldRelocSec.first, 4);
 842       OS.EmitIntValue(FieldRelocSec.second.size(), 4);
 843       for (const auto &FieldRelocInfo : FieldRelocSec.second) {
 844         Asm->EmitLabelReference(FieldRelocInfo.Label, 4);
 845         OS.EmitIntValue(FieldRelocInfo.TypeID, 4);
 846         OS.EmitIntValue(FieldRelocInfo.OffsetNameOff, 4);
 847         OS.EmitIntValue(FieldRelocInfo.RelocKind, 4);
 848       }
 849     }
 850   }
 851
 852   // Emit extern reloc table.
 853   if (ExternRelocLen) {
 854     OS.AddComment("ExternReloc");
 855     OS.EmitIntValue(BTF::BPFExternRelocSize, 4);
 856     for (const auto &ExternRelocSec : ExternRelocTable) {
 857       OS.AddComment("Extern reloc section string offset=" +
 858                     std::to_string(ExternRelocSec.first));
 859       OS.EmitIntValue(ExternRelocSec.first, 4);
 860       OS.EmitIntValue(ExternRelocSec.second.size(), 4);
 861       for (const auto &ExternRelocInfo : ExternRelocSec.second) {
 862         Asm->EmitLabelReference(ExternRelocInfo.Label, 4);
 863         OS.EmitIntValue(ExternRelocInfo.ExternNameOff, 4);
 864       }
 865     }
 866   }
 867 }
 868
 869 void BTFDebug::beginFunctionImpl(const MachineFunction *MF) {
 870   auto *SP = MF->getFunction().getSubprogram();
 871   auto *Unit = SP->getUnit();
 872
 873   if (Unit->getEmissionKind() == DICompileUnit::NoDebug) {
 874     SkipInstruction = true;
 875     return;
 876   }
 877   SkipInstruction = false;
 878
 879   // Collect MapDef types. Map definition needs to collect
 880   // pointee types. Do it first. Otherwise, for the following
 881   // case:
 882   //    struct m { ...};
 883   //    struct t {
 884   //      struct m *key;
 885   //    };
 886   //    foo(struct t *arg);
 887   //
 888   //    struct mapdef {
 889   //      ...
 890   //      struct m *key;
 891   //      ...
 892   //    } __attribute__((section(".maps"))) hash_map;
 893   //
 894   // If subroutine foo is traversed first, a type chain
 895   // "ptr->struct m(fwd)" will be created and later on
 896   // when traversing mapdef, since "ptr->struct m" exists,
 897   // the traversal of "struct m" will be omitted.
 898   if (MapDefNotCollected) {
 899     processGlobals(true);
 900     MapDefNotCollected = false;
 901   }
 902
 903   // Collect all types locally referenced in this function.
 904   // Use RetainedNodes so we can collect all argument names
 905   // even if the argument is not used.
 906   std::unordered_map<uint32_t, StringRef> FuncArgNames;
 907   for (const DINode *DN : SP->getRetainedNodes()) {
 908     if (const auto *DV = dyn_cast<DILocalVariable>(DN)) {
 909       // Collect function arguments for subprogram func type.
 910       uint32_t Arg = DV->getArg();
 911       if (Arg) {
 912         visitTypeEntry(DV->getType());
 913         FuncArgNames[Arg] = DV->getName();
 914       }
 915     }
 916   }
 917
 918   // Construct subprogram func proto type.
 919   uint32_t ProtoTypeId;
 920   visitSubroutineType(SP->getType(), true, FuncArgNames, ProtoTypeId);
 921
 922   // Construct subprogram func type
 923   auto FuncTypeEntry =
 924       std::make_unique<BTFTypeFunc>(SP->getName(), ProtoTypeId);
 925   uint32_t FuncTypeId = addType(std::move(FuncTypeEntry));
 926
 927   for (const auto &TypeEntry : TypeEntries)
 928     TypeEntry->completeType(*this);
 929
 930   // Construct funcinfo and the first lineinfo for the function.
 931   MCSymbol *FuncLabel = Asm->getFunctionBegin();
 932   BTFFuncInfo FuncInfo;
 933   FuncInfo.Label = FuncLabel;
 934   FuncInfo.TypeId = FuncTypeId;
 935   if (FuncLabel->isInSection()) {
 936     MCSection &Section = FuncLabel->getSection();
 937     const MCSectionELF *SectionELF = dyn_cast<MCSectionELF>(&Section);
 938     assert(SectionELF && "Null section for Function Label");
 939     SecNameOff = addString(SectionELF->getSectionName());
 940   } else {
 941     SecNameOff = addString(".text");
 942   }
 943   FuncInfoTable[SecNameOff].push_back(FuncInfo);
 944 }
 945
 946 void BTFDebug::endFunctionImpl(const MachineFunction *MF) {
 947   SkipInstruction = false;
 948   LineInfoGenerated = false;
 949   SecNameOff = 0;
 950 }
 951
 952 /// On-demand populate struct types as requested from abstract member
 953 /// accessing.
 954 unsigned BTFDebug::populateStructType(const DIType *Ty) {
 955   unsigned Id;
 956   visitTypeEntry(Ty, Id, false, false);
 957   for (const auto &TypeEntry : TypeEntries)
 958     TypeEntry->completeType(*this);
 959   return Id;
 960 }
 961
 962 /// Generate a struct member field relocation.
 963 void BTFDebug::generateFieldReloc(const MachineInstr *MI,
 964                                    const MCSymbol *ORSym, DIType *RootTy,
 965                                    StringRef AccessPattern) {
 966   unsigned RootId = populateStructType(RootTy);
 967   size_t FirstDollar = AccessPattern.find_first_of('$');
 968   size_t FirstColon = AccessPattern.find_first_of(':');
 969   size_t SecondColon = AccessPattern.find_first_of(':', FirstColon + 1);
 970   StringRef IndexPattern = AccessPattern.substr(FirstDollar + 1);
 971   StringRef RelocKindStr = AccessPattern.substr(FirstColon + 1,
 972       SecondColon - FirstColon);
 973   StringRef PatchImmStr = AccessPattern.substr(SecondColon + 1,
 974       FirstDollar - SecondColon);
 975
 976   BTFFieldReloc FieldReloc;
 977   FieldReloc.Label = ORSym;
 978   FieldReloc.OffsetNameOff = addString(IndexPattern);
 979   FieldReloc.TypeID = RootId;
 980   FieldReloc.RelocKind = std::stoull(RelocKindStr);
 981   PatchImms[AccessPattern.str()] = std::stoul(PatchImmStr);
 982   FieldRelocTable[SecNameOff].push_back(FieldReloc);
 983 }
 984
 985 void BTFDebug::processLDimm64(const MachineInstr *MI) {
 986   // If the insn is an LD_imm64, the following two cases
 987   // will generate an .BTF.ext record.
 988   //
 989   // If the insn is "r2 = LD_imm64 @__BTF_...",
 990   // add this insn into the .BTF.ext FieldReloc subsection.
 991   // Relocation looks like:
 992   //  . SecName:
 993   //    . InstOffset
 994   //    . TypeID
 995   //    . OffSetNameOff
 996   // Later, the insn is replaced with "r2 = <offset>"
 997   // where "<offset>" equals to the offset based on current
 998   // type definitions.
 999   //
1000   // If the insn is "r2 = LD_imm64 @VAR" and VAR is
1001   // a patchable external global, add this insn into the .BTF.ext
1002   // ExternReloc subsection.
1003   // Relocation looks like:
1004   //  . SecName:
1005   //    . InstOffset
1006   //    . ExternNameOff
1007   // Later, the insn is replaced with "r2 = <value>" or
1008   // "LD_imm64 r2, <value>" where "<value>" = 0.
1009
1010   // check whether this is a candidate or not
1011   const MachineOperand &MO = MI->getOperand(1);
1012   if (MO.isGlobal()) {
1013     const GlobalValue *GVal = MO.getGlobal();
1014     auto *GVar = dyn_cast<GlobalVariable>(GVal);
1015     if (GVar && GVar->hasAttribute(BPFCoreSharedInfo::AmaAttr)) {
1016       MCSymbol *ORSym = OS.getContext().createTempSymbol();
1017       OS.EmitLabel(ORSym);
1018
1019       MDNode *MDN = GVar->getMetadata(LLVMContext::MD_preserve_access_index);
1020       DIType *Ty = dyn_cast<DIType>(MDN);
1021       generateFieldReloc(MI, ORSym, Ty, GVar->getName());
1022     } else if (GVar && !GVar->hasInitializer() && GVar->hasExternalLinkage() &&
1023                GVar->getSection() == BPFCoreSharedInfo::PatchableExtSecName) {
1024       MCSymbol *ORSym = OS.getContext().createTempSymbol();
1025       OS.EmitLabel(ORSym);
1026
1027       BTFExternReloc ExternReloc;
1028       ExternReloc.Label = ORSym;
1029       ExternReloc.ExternNameOff = addString(GVar->getName());
1030       ExternRelocTable[SecNameOff].push_back(ExternReloc);
1031     }
1032   }
1033 }
1034
1035 void BTFDebug::beginInstruction(const MachineInstr *MI) {
1036   DebugHandlerBase::beginInstruction(MI);
1037
1038   if (SkipInstruction || MI->isMetaInstruction() ||
1039       MI->getFlag(MachineInstr::FrameSetup))
1040     return;
1041
1042   if (MI->isInlineAsm()) {
1043     // Count the number of register definitions to find the asm string.
1044     unsigned NumDefs = 0;
1045     for (; MI->getOperand(NumDefs).isReg() && MI->getOperand(NumDefs).isDef();
1046          ++NumDefs)
1047       ;
1048
1049     // Skip this inline asm instruction if the asmstr is empty.
1050     const char *AsmStr = MI->getOperand(NumDefs).getSymbolName();
1051     if (AsmStr[0] == 0)
1052       return;
1053   }
1054
1055   if (MI->getOpcode() == BPF::LD_imm64)
1056     processLDimm64(MI);
1057
1058   // Skip this instruction if no DebugLoc or the DebugLoc
1059   // is the same as the previous instruction.
1060   const DebugLoc &DL = MI->getDebugLoc();
1061   if (!DL || PrevInstLoc == DL) {
1062     // This instruction will be skipped, no LineInfo has
1063     // been generated, construct one based on function signature.
1064     if (LineInfoGenerated == false) {
1065       auto *S = MI->getMF()->getFunction().getSubprogram();
1066       MCSymbol *FuncLabel = Asm->getFunctionBegin();
1067       constructLineInfo(S, FuncLabel, S->getLine(), 0);
1068       LineInfoGenerated = true;
1069     }
1070
1071     return;
1072   }
1073
1074   // Create a temporary label to remember the insn for lineinfo.
1075   MCSymbol *LineSym = OS.getContext().createTempSymbol();
1076   OS.EmitLabel(LineSym);
1077
1078   // Construct the lineinfo.
1079   auto SP = DL.get()->getScope()->getSubprogram();
1080   constructLineInfo(SP, LineSym, DL.getLine(), DL.getCol());
1081
1082   LineInfoGenerated = true;
1083   PrevInstLoc = DL;
1084 }
1085
1086 void BTFDebug::processGlobals(bool ProcessingMapDef) {
1087   // Collect all types referenced by globals.
1088   const Module *M = MMI->getModule();
1089   for (const GlobalVariable &Global : M->globals()) {
1090     // Ignore external globals for now.
1091     if (!Global.hasInitializer() && Global.hasExternalLinkage())
1092       continue;
1093
1094     // Decide the section name.
1095     StringRef SecName;
1096     if (Global.hasSection()) {
1097       SecName = Global.getSection();
1098     } else {
1099       // data, bss, or readonly sections
1100       if (Global.isConstant())
1101         SecName = ".rodata";
1102       else
1103         SecName = Global.getInitializer()->isZeroValue() ? ".bss" : ".data";
1104     }
1105
1106     if (ProcessingMapDef != SecName.startswith(".maps"))
1107       continue;
1108
1109     SmallVector<DIGlobalVariableExpression *, 1> GVs;
1110     Global.getDebugInfo(GVs);
1111     uint32_t GVTypeId = 0;
1112     for (auto *GVE : GVs) {
1113       if (SecName.startswith(".maps"))
1114         visitMapDefType(GVE->getVariable()->getType(), GVTypeId);
1115       else
1116         visitTypeEntry(GVE->getVariable()->getType(), GVTypeId, false, false);
1117       break;
1118     }
1119
1120     // Only support the following globals:
1121     //  . static variables
1122     //  . non-static global variables with section attributes
1123     // Essentially means:
1124     //  . .bcc/.data/.rodata DataSec entities only contain static data
1125     //  . Other DataSec entities contain static or initialized global data.
1126     //    Initialized global data are mostly used for finding map key/value type
1127     //    id's. Whether DataSec is readonly or not can be found from
1128     //    corresponding ELF section flags.
1129     auto Linkage = Global.getLinkage();
1130     if (Linkage != GlobalValue::InternalLinkage &&
1131         (Linkage != GlobalValue::ExternalLinkage || !Global.hasSection()))
1132       continue;
1133
1134     uint32_t GVarInfo = Linkage == GlobalValue::ExternalLinkage
1135                             ? BTF::VAR_GLOBAL_ALLOCATED
1136                             : BTF::VAR_STATIC;
1137     auto VarEntry =
1138         std::make_unique<BTFKindVar>(Global.getName(), GVTypeId, GVarInfo);
1139     uint32_t VarId = addType(std::move(VarEntry));
1140
1141     // Find or create a DataSec
1142     if (DataSecEntries.find(SecName) == DataSecEntries.end()) {
1143       DataSecEntries[SecName] = std::make_unique<BTFKindDataSec>(Asm, SecName);
1144     }
1145
1146     // Calculate symbol size
1147     const DataLayout &DL = Global.getParent()->getDataLayout();
1148     uint32_t Size = DL.getTypeAllocSize(Global.getType()->getElementType());
1149
1150     DataSecEntries[SecName]->addVar(VarId, Asm->getSymbol(&Global), Size);
1151   }
1152 }
1153
1154 /// Emit proper patchable instructions.
1155 bool BTFDebug::InstLower(const MachineInstr *MI, MCInst &OutMI) {
1156   if (MI->getOpcode() == BPF::LD_imm64) {
1157     const MachineOperand &MO = MI->getOperand(1);
1158     if (MO.isGlobal()) {
1159       const GlobalValue *GVal = MO.getGlobal();
1160       auto *GVar = dyn_cast<GlobalVariable>(GVal);
1161       if (GVar && GVar->hasAttribute(BPFCoreSharedInfo::AmaAttr)) {
1162         // Emit "mov ri, <imm>" for patched immediate.
1163         uint32_t Imm = PatchImms[GVar->getName().str()];
1164         OutMI.setOpcode(BPF::MOV_ri);
1165         OutMI.addOperand(MCOperand::createReg(MI->getOperand(0).getReg()));
1166         OutMI.addOperand(MCOperand::createImm(Imm));
1167         return true;
1168       } else if (GVar && !GVar->hasInitializer() &&
1169                  GVar->hasExternalLinkage() &&
1170                  GVar->getSection() == BPFCoreSharedInfo::PatchableExtSecName) {
1171         const IntegerType *IntTy = dyn_cast<IntegerType>(GVar->getValueType());
1172         assert(IntTy);
1173         // For patchable externals, emit "LD_imm64, ri, 0" if the external
1174         // variable is 64bit width, emit "mov ri, 0" otherwise.
1175         if (IntTy->getBitWidth() == 64)
1176           OutMI.setOpcode(BPF::LD_imm64);
1177         else
1178           OutMI.setOpcode(BPF::MOV_ri);
1179         OutMI.addOperand(MCOperand::createReg(MI->getOperand(0).getReg()));
1180         OutMI.addOperand(MCOperand::createImm(0));
1181         return true;
1182       }
1183     }
1184   }
1185   return false;
1186 }
1187
1188 void BTFDebug::endModule() {
1189   // Collect MapDef globals if not collected yet.
1190   if (MapDefNotCollected) {
1191     processGlobals(true);
1192     MapDefNotCollected = false;
1193   }
1194
1195   // Collect global types/variables except MapDef globals.
1196   processGlobals(false);
1197   for (auto &DataSec : DataSecEntries)
1198     addType(std::move(DataSec.second));
1199
1200   // Fixups
1201   for (auto &Fixup : FixupDerivedTypes) {
1202     StringRef TypeName = Fixup.first;
1203     bool IsUnion = Fixup.second.first;
1204
1205     // Search through struct types
1206     uint32_t StructTypeId = 0;
1207     for (const auto &StructType : StructTypes) {
1208       if (StructType->getName() == TypeName) {
1209         StructTypeId = StructType->getId();
1210         break;
1211       }
1212     }
1213
1214     if (StructTypeId == 0) {
1215       auto FwdTypeEntry = std::make_unique<BTFTypeFwd>(TypeName, IsUnion);
1216       StructTypeId = addType(std::move(FwdTypeEntry));
1217     }
1218
1219     for (auto &DType : Fixup.second.second) {
1220       DType->setPointeeType(StructTypeId);
1221     }
1222   }
1223
1224   // Complete BTF type cross refereences.
1225   for (const auto &TypeEntry : TypeEntries)
1226     TypeEntry->completeType(*this);
1227
1228   // Emit BTF sections.
1229   emitBTFSection();
1230   emitBTFExtSection();
1231 }