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llvm-mirror/lib/Target/BPF/BTFDebug.cpp
Yonghong Song 51c6311d11 BPF: generate .rodata BTF datasec for certain initialized local var's 
Currently, BTF datasec type for .rodata is generated only if there are
user-defined readonly global variables which have debuginfo generated.

Certain readonly global variables may be generated from initialized
local variables. For example,
  void foo(const void *);
  int test() {
    const struct {
      unsigned a[4];
      char b;
    } val = { .a = {2, 3, 4, 5}, .b = 6 };
    foo(&val);
    return 0;
  }

The clang will create a private linkage const global to store
the initialized value:
  @__const.test.val = private unnamed_addr constant %struct.anon
      { [4 x i32] [i32 2, i32 3, i32 4, i32 5], i8 6 }, align 4

This global variable eventually is put in .rodata ELF section.

If there is .rodata ELF section, libbpf expects a BTF .rodata
datasec as well even though it may be empty meaning there are no
global readonly variables with proper debuginfo. Martin reported
a bug where without this empty BTF .rodata datasec, the bpftool
gen will exit with an error.

This patch fixed the issue by generating .rodata BTF datasec
if there exists local var intial data which will result in
.rodata ELF section.

Differential Revision: https://reviews.llvm.org/D84002
2020-07-17 09:45:57 -07:00

1316 lines
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//===- BTFDebug.cpp - BTF Generator ---------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains support for writing BTF debug info.
//
//===----------------------------------------------------------------------===//
#include "BTFDebug.h"
#include "BPF.h"
#include "BPFCORE.h"
#include "MCTargetDesc/BPFMCTargetDesc.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCObjectFileInfo.h"
#include "llvm/MC/MCSectionELF.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/Support/LineIterator.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
using namespace llvm;
static const char *BTFKindStr[] = {
#define HANDLE_BTF_KIND(ID, NAME) "BTF_KIND_" #NAME,
#include "BTF.def"
};
/// Emit a BTF common type.
void BTFTypeBase::emitType(MCStreamer &OS) {
OS.AddComment(std::string(BTFKindStr[Kind]) + "(id = " + std::to_string(Id) +
")");
OS.emitInt32(BTFType.NameOff);
OS.AddComment("0x" + Twine::utohexstr(BTFType.Info));
OS.emitInt32(BTFType.Info);
OS.emitInt32(BTFType.Size);
}
BTFTypeDerived::BTFTypeDerived(const DIDerivedType *DTy, unsigned Tag,
bool NeedsFixup)
: DTy(DTy), NeedsFixup(NeedsFixup) {
switch (Tag) {
case dwarf::DW_TAG_pointer_type:
Kind = BTF::BTF_KIND_PTR;
break;
case dwarf::DW_TAG_const_type:
Kind = BTF::BTF_KIND_CONST;
break;
case dwarf::DW_TAG_volatile_type:
Kind = BTF::BTF_KIND_VOLATILE;
break;
case dwarf::DW_TAG_typedef:
Kind = BTF::BTF_KIND_TYPEDEF;
break;
case dwarf::DW_TAG_restrict_type:
Kind = BTF::BTF_KIND_RESTRICT;
break;
default:
llvm_unreachable("Unknown DIDerivedType Tag");
}
BTFType.Info = Kind << 24;
}
void BTFTypeDerived::completeType(BTFDebug &BDebug) {
if (IsCompleted)
return;
IsCompleted = true;
BTFType.NameOff = BDebug.addString(DTy->getName());
if (NeedsFixup)
return;
// The base type for PTR/CONST/VOLATILE could be void.
const DIType *ResolvedType = DTy->getBaseType();
if (!ResolvedType) {
assert((Kind == BTF::BTF_KIND_PTR || Kind == BTF::BTF_KIND_CONST ||
Kind == BTF::BTF_KIND_VOLATILE) &&
"Invalid null basetype");
BTFType.Type = 0;
} else {
BTFType.Type = BDebug.getTypeId(ResolvedType);
}
}
void BTFTypeDerived::emitType(MCStreamer &OS) { BTFTypeBase::emitType(OS); }
void BTFTypeDerived::setPointeeType(uint32_t PointeeType) {
BTFType.Type = PointeeType;
}
/// Represent a struct/union forward declaration.
BTFTypeFwd::BTFTypeFwd(StringRef Name, bool IsUnion) : Name(Name) {
Kind = BTF::BTF_KIND_FWD;
BTFType.Info = IsUnion << 31 | Kind << 24;
BTFType.Type = 0;
}
void BTFTypeFwd::completeType(BTFDebug &BDebug) {
if (IsCompleted)
return;
IsCompleted = true;
BTFType.NameOff = BDebug.addString(Name);
}
void BTFTypeFwd::emitType(MCStreamer &OS) { BTFTypeBase::emitType(OS); }
BTFTypeInt::BTFTypeInt(uint32_t Encoding, uint32_t SizeInBits,
uint32_t OffsetInBits, StringRef TypeName)
: Name(TypeName) {
// Translate IR int encoding to BTF int encoding.
uint8_t BTFEncoding;
switch (Encoding) {
case dwarf::DW_ATE_boolean:
BTFEncoding = BTF::INT_BOOL;
break;
case dwarf::DW_ATE_signed:
case dwarf::DW_ATE_signed_char:
BTFEncoding = BTF::INT_SIGNED;
break;
case dwarf::DW_ATE_unsigned:
case dwarf::DW_ATE_unsigned_char:
BTFEncoding = 0;
break;
default:
llvm_unreachable("Unknown BTFTypeInt Encoding");
}
Kind = BTF::BTF_KIND_INT;
BTFType.Info = Kind << 24;
BTFType.Size = roundupToBytes(SizeInBits);
IntVal = (BTFEncoding << 24) | OffsetInBits << 16 | SizeInBits;
}
void BTFTypeInt::completeType(BTFDebug &BDebug) {
if (IsCompleted)
return;
IsCompleted = true;
BTFType.NameOff = BDebug.addString(Name);
}
void BTFTypeInt::emitType(MCStreamer &OS) {
BTFTypeBase::emitType(OS);
OS.AddComment("0x" + Twine::utohexstr(IntVal));
OS.emitInt32(IntVal);
}
BTFTypeEnum::BTFTypeEnum(const DICompositeType *ETy, uint32_t VLen) : ETy(ETy) {
Kind = BTF::BTF_KIND_ENUM;
BTFType.Info = Kind << 24 | VLen;
BTFType.Size = roundupToBytes(ETy->getSizeInBits());
}
void BTFTypeEnum::completeType(BTFDebug &BDebug) {
if (IsCompleted)
return;
IsCompleted = true;
BTFType.NameOff = BDebug.addString(ETy->getName());
DINodeArray Elements = ETy->getElements();
for (const auto Element : Elements) {
const auto *Enum = cast<DIEnumerator>(Element);
struct BTF::BTFEnum BTFEnum;
BTFEnum.NameOff = BDebug.addString(Enum->getName());
// BTF enum value is 32bit, enforce it.
uint32_t Value;
if (Enum->isUnsigned())
Value = static_cast<uint32_t>(Enum->getValue().getZExtValue());
else
Value = static_cast<uint32_t>(Enum->getValue().getSExtValue());
BTFEnum.Val = Value;
EnumValues.push_back(BTFEnum);
}
}
void BTFTypeEnum::emitType(MCStreamer &OS) {
BTFTypeBase::emitType(OS);
for (const auto &Enum : EnumValues) {
OS.emitInt32(Enum.NameOff);
OS.emitInt32(Enum.Val);
}
}
BTFTypeArray::BTFTypeArray(uint32_t ElemTypeId, uint32_t NumElems) {
Kind = BTF::BTF_KIND_ARRAY;
BTFType.NameOff = 0;
BTFType.Info = Kind << 24;
BTFType.Size = 0;
ArrayInfo.ElemType = ElemTypeId;
ArrayInfo.Nelems = NumElems;
}
/// Represent a BTF array.
void BTFTypeArray::completeType(BTFDebug &BDebug) {
if (IsCompleted)
return;
IsCompleted = true;
// The IR does not really have a type for the index.
// A special type for array index should have been
// created during initial type traversal. Just
// retrieve that type id.
ArrayInfo.IndexType = BDebug.getArrayIndexTypeId();
}
void BTFTypeArray::emitType(MCStreamer &OS) {
BTFTypeBase::emitType(OS);
OS.emitInt32(ArrayInfo.ElemType);
OS.emitInt32(ArrayInfo.IndexType);
OS.emitInt32(ArrayInfo.Nelems);
}
/// Represent either a struct or a union.
BTFTypeStruct::BTFTypeStruct(const DICompositeType *STy, bool IsStruct,
bool HasBitField, uint32_t Vlen)
: STy(STy), HasBitField(HasBitField) {
Kind = IsStruct ? BTF::BTF_KIND_STRUCT : BTF::BTF_KIND_UNION;
BTFType.Size = roundupToBytes(STy->getSizeInBits());
BTFType.Info = (HasBitField << 31) | (Kind << 24) | Vlen;
}
void BTFTypeStruct::completeType(BTFDebug &BDebug) {
if (IsCompleted)
return;
IsCompleted = true;
BTFType.NameOff = BDebug.addString(STy->getName());
// Add struct/union members.
const DINodeArray Elements = STy->getElements();
for (const auto *Element : Elements) {
struct BTF::BTFMember BTFMember;
const auto *DDTy = cast<DIDerivedType>(Element);
BTFMember.NameOff = BDebug.addString(DDTy->getName());
if (HasBitField) {
uint8_t BitFieldSize = DDTy->isBitField() ? DDTy->getSizeInBits() : 0;
BTFMember.Offset = BitFieldSize << 24 | DDTy->getOffsetInBits();
} else {
BTFMember.Offset = DDTy->getOffsetInBits();
}
const auto *BaseTy = DDTy->getBaseType();
BTFMember.Type = BDebug.getTypeId(BaseTy);
Members.push_back(BTFMember);
}
}
void BTFTypeStruct::emitType(MCStreamer &OS) {
BTFTypeBase::emitType(OS);
for (const auto &Member : Members) {
OS.emitInt32(Member.NameOff);
OS.emitInt32(Member.Type);
OS.AddComment("0x" + Twine::utohexstr(Member.Offset));
OS.emitInt32(Member.Offset);
}
}
std::string BTFTypeStruct::getName() { return std::string(STy->getName()); }
/// The Func kind represents both subprogram and pointee of function
/// pointers. If the FuncName is empty, it represents a pointee of function
/// pointer. Otherwise, it represents a subprogram. The func arg names
/// are empty for pointee of function pointer case, and are valid names
/// for subprogram.
BTFTypeFuncProto::BTFTypeFuncProto(
const DISubroutineType *STy, uint32_t VLen,
const std::unordered_map<uint32_t, StringRef> &FuncArgNames)
: STy(STy), FuncArgNames(FuncArgNames) {
Kind = BTF::BTF_KIND_FUNC_PROTO;
BTFType.Info = (Kind << 24) | VLen;
}
void BTFTypeFuncProto::completeType(BTFDebug &BDebug) {
if (IsCompleted)
return;
IsCompleted = true;
DITypeRefArray Elements = STy->getTypeArray();
auto RetType = Elements[0];
BTFType.Type = RetType ? BDebug.getTypeId(RetType) : 0;
BTFType.NameOff = 0;
// For null parameter which is typically the last one
// to represent the vararg, encode the NameOff/Type to be 0.
for (unsigned I = 1, N = Elements.size(); I < N; ++I) {
struct BTF::BTFParam Param;
auto Element = Elements[I];
if (Element) {
Param.NameOff = BDebug.addString(FuncArgNames[I]);
Param.Type = BDebug.getTypeId(Element);
} else {
Param.NameOff = 0;
Param.Type = 0;
}
Parameters.push_back(Param);
}
}
void BTFTypeFuncProto::emitType(MCStreamer &OS) {
BTFTypeBase::emitType(OS);
for (const auto &Param : Parameters) {
OS.emitInt32(Param.NameOff);
OS.emitInt32(Param.Type);
}
}
BTFTypeFunc::BTFTypeFunc(StringRef FuncName, uint32_t ProtoTypeId,
uint32_t Scope)
: Name(FuncName) {
Kind = BTF::BTF_KIND_FUNC;
BTFType.Info = (Kind << 24) | Scope;
BTFType.Type = ProtoTypeId;
}
void BTFTypeFunc::completeType(BTFDebug &BDebug) {
if (IsCompleted)
return;
IsCompleted = true;
BTFType.NameOff = BDebug.addString(Name);
}
void BTFTypeFunc::emitType(MCStreamer &OS) { BTFTypeBase::emitType(OS); }
BTFKindVar::BTFKindVar(StringRef VarName, uint32_t TypeId, uint32_t VarInfo)
: Name(VarName) {
Kind = BTF::BTF_KIND_VAR;
BTFType.Info = Kind << 24;
BTFType.Type = TypeId;
Info = VarInfo;
}
void BTFKindVar::completeType(BTFDebug &BDebug) {
BTFType.NameOff = BDebug.addString(Name);
}
void BTFKindVar::emitType(MCStreamer &OS) {
BTFTypeBase::emitType(OS);
OS.emitInt32(Info);
}
BTFKindDataSec::BTFKindDataSec(AsmPrinter *AsmPrt, std::string SecName)
: Asm(AsmPrt), Name(SecName) {
Kind = BTF::BTF_KIND_DATASEC;
BTFType.Info = Kind << 24;
BTFType.Size = 0;
}
void BTFKindDataSec::completeType(BTFDebug &BDebug) {
BTFType.NameOff = BDebug.addString(Name);
BTFType.Info |= Vars.size();
}
void BTFKindDataSec::emitType(MCStreamer &OS) {
BTFTypeBase::emitType(OS);
for (const auto &V : Vars) {
OS.emitInt32(std::get<0>(V));
Asm->emitLabelReference(std::get<1>(V), 4);
OS.emitInt32(std::get<2>(V));
}
}
uint32_t BTFStringTable::addString(StringRef S) {
// Check whether the string already exists.
for (auto &OffsetM : OffsetToIdMap) {
if (Table[OffsetM.second] == S)
return OffsetM.first;
}
// Not find, add to the string table.
uint32_t Offset = Size;
OffsetToIdMap[Offset] = Table.size();
Table.push_back(std::string(S));
Size += S.size() + 1;
return Offset;
}
BTFDebug::BTFDebug(AsmPrinter *AP)
: DebugHandlerBase(AP), OS(*Asm->OutStreamer), SkipInstruction(false),
LineInfoGenerated(false), SecNameOff(0), ArrayIndexTypeId(0),
MapDefNotCollected(true) {
addString("\0");
}
uint32_t BTFDebug::addType(std::unique_ptr<BTFTypeBase> TypeEntry,
const DIType *Ty) {
TypeEntry->setId(TypeEntries.size() + 1);
uint32_t Id = TypeEntry->getId();
DIToIdMap[Ty] = Id;
TypeEntries.push_back(std::move(TypeEntry));
return Id;
}
uint32_t BTFDebug::addType(std::unique_ptr<BTFTypeBase> TypeEntry) {
TypeEntry->setId(TypeEntries.size() + 1);
uint32_t Id = TypeEntry->getId();
TypeEntries.push_back(std::move(TypeEntry));
return Id;
}
void BTFDebug::visitBasicType(const DIBasicType *BTy, uint32_t &TypeId) {
// Only int types are supported in BTF.
uint32_t Encoding = BTy->getEncoding();
if (Encoding != dwarf::DW_ATE_boolean && Encoding != dwarf::DW_ATE_signed &&
Encoding != dwarf::DW_ATE_signed_char &&
Encoding != dwarf::DW_ATE_unsigned &&
Encoding != dwarf::DW_ATE_unsigned_char)
return;
// Create a BTF type instance for this DIBasicType and put it into
// DIToIdMap for cross-type reference check.
auto TypeEntry = std::make_unique<BTFTypeInt>(
Encoding, BTy->getSizeInBits(), BTy->getOffsetInBits(), BTy->getName());
TypeId = addType(std::move(TypeEntry), BTy);
}
/// Handle subprogram or subroutine types.
void BTFDebug::visitSubroutineType(
const DISubroutineType *STy, bool ForSubprog,
const std::unordered_map<uint32_t, StringRef> &FuncArgNames,
uint32_t &TypeId) {
DITypeRefArray Elements = STy->getTypeArray();
uint32_t VLen = Elements.size() - 1;
if (VLen > BTF::MAX_VLEN)
return;
// Subprogram has a valid non-zero-length name, and the pointee of
// a function pointer has an empty name. The subprogram type will
// not be added to DIToIdMap as it should not be referenced by
// any other types.
auto TypeEntry = std::make_unique<BTFTypeFuncProto>(STy, VLen, FuncArgNames);
if (ForSubprog)
TypeId = addType(std::move(TypeEntry)); // For subprogram
else
TypeId = addType(std::move(TypeEntry), STy); // For func ptr
// Visit return type and func arg types.
for (const auto Element : Elements) {
visitTypeEntry(Element);
}
}
/// Handle structure/union types.
void BTFDebug::visitStructType(const DICompositeType *CTy, bool IsStruct,
uint32_t &TypeId) {
const DINodeArray Elements = CTy->getElements();
uint32_t VLen = Elements.size();
if (VLen > BTF::MAX_VLEN)
return;
// Check whether we have any bitfield members or not
bool HasBitField = false;
for (const auto *Element : Elements) {
auto E = cast<DIDerivedType>(Element);
if (E->isBitField()) {
HasBitField = true;
break;
}
}
auto TypeEntry =
std::make_unique<BTFTypeStruct>(CTy, IsStruct, HasBitField, VLen);
StructTypes.push_back(TypeEntry.get());
TypeId = addType(std::move(TypeEntry), CTy);
// Visit all struct members.
for (const auto *Element : Elements)
visitTypeEntry(cast<DIDerivedType>(Element));
}
void BTFDebug::visitArrayType(const DICompositeType *CTy, uint32_t &TypeId) {
// Visit array element type.
uint32_t ElemTypeId;
const DIType *ElemType = CTy->getBaseType();
visitTypeEntry(ElemType, ElemTypeId, false, false);
// Visit array dimensions.
DINodeArray Elements = CTy->getElements();
for (int I = Elements.size() - 1; I >= 0; --I) {
if (auto *Element = dyn_cast_or_null<DINode>(Elements[I]))
if (Element->getTag() == dwarf::DW_TAG_subrange_type) {
const DISubrange *SR = cast<DISubrange>(Element);
auto *CI = SR->getCount().dyn_cast<ConstantInt *>();
int64_t Count = CI->getSExtValue();
// For struct s { int b; char c[]; }, the c[] will be represented
// as an array with Count = -1.
auto TypeEntry =
std::make_unique<BTFTypeArray>(ElemTypeId,
Count >= 0 ? Count : 0);
if (I == 0)
ElemTypeId = addType(std::move(TypeEntry), CTy);
else
ElemTypeId = addType(std::move(TypeEntry));
}
}
// The array TypeId is the type id of the outermost dimension.
TypeId = ElemTypeId;
// The IR does not have a type for array index while BTF wants one.
// So create an array index type if there is none.
if (!ArrayIndexTypeId) {
auto TypeEntry = std::make_unique<BTFTypeInt>(dwarf::DW_ATE_unsigned, 32,
0, "__ARRAY_SIZE_TYPE__");
ArrayIndexTypeId = addType(std::move(TypeEntry));
}
}
void BTFDebug::visitEnumType(const DICompositeType *CTy, uint32_t &TypeId) {
DINodeArray Elements = CTy->getElements();
uint32_t VLen = Elements.size();
if (VLen > BTF::MAX_VLEN)
return;
auto TypeEntry = std::make_unique<BTFTypeEnum>(CTy, VLen);
TypeId = addType(std::move(TypeEntry), CTy);
// No need to visit base type as BTF does not encode it.
}
/// Handle structure/union forward declarations.
void BTFDebug::visitFwdDeclType(const DICompositeType *CTy, bool IsUnion,
uint32_t &TypeId) {
auto TypeEntry = std::make_unique<BTFTypeFwd>(CTy->getName(), IsUnion);
TypeId = addType(std::move(TypeEntry), CTy);
}
/// Handle structure, union, array and enumeration types.
void BTFDebug::visitCompositeType(const DICompositeType *CTy,
uint32_t &TypeId) {
auto Tag = CTy->getTag();
if (Tag == dwarf::DW_TAG_structure_type || Tag == dwarf::DW_TAG_union_type) {
// Handle forward declaration differently as it does not have members.
if (CTy->isForwardDecl())
visitFwdDeclType(CTy, Tag == dwarf::DW_TAG_union_type, TypeId);
else
visitStructType(CTy, Tag == dwarf::DW_TAG_structure_type, TypeId);
} else if (Tag == dwarf::DW_TAG_array_type)
visitArrayType(CTy, TypeId);
else if (Tag == dwarf::DW_TAG_enumeration_type)
visitEnumType(CTy, TypeId);
}
/// Handle pointer, typedef, const, volatile, restrict and member types.
void BTFDebug::visitDerivedType(const DIDerivedType *DTy, uint32_t &TypeId,
bool CheckPointer, bool SeenPointer) {
unsigned Tag = DTy->getTag();
/// Try to avoid chasing pointees, esp. structure pointees which may
/// unnecessary bring in a lot of types.
if (CheckPointer && !SeenPointer) {
SeenPointer = Tag == dwarf::DW_TAG_pointer_type;
}
if (CheckPointer && SeenPointer) {
const DIType *Base = DTy->getBaseType();
if (Base) {
if (const auto *CTy = dyn_cast<DICompositeType>(Base)) {
auto CTag = CTy->getTag();
if ((CTag == dwarf::DW_TAG_structure_type ||
CTag == dwarf::DW_TAG_union_type) &&
!CTy->getName().empty() && !CTy->isForwardDecl()) {
/// Find a candidate, generate a fixup. Later on the struct/union
/// pointee type will be replaced with either a real type or
/// a forward declaration.
auto TypeEntry = std::make_unique<BTFTypeDerived>(DTy, Tag, true);
auto &Fixup = FixupDerivedTypes[CTy->getName()];
Fixup.first = CTag == dwarf::DW_TAG_union_type;
Fixup.second.push_back(TypeEntry.get());
TypeId = addType(std::move(TypeEntry), DTy);
return;
}
}
}
}
if (Tag == dwarf::DW_TAG_pointer_type || Tag == dwarf::DW_TAG_typedef ||
Tag == dwarf::DW_TAG_const_type || Tag == dwarf::DW_TAG_volatile_type ||
Tag == dwarf::DW_TAG_restrict_type) {
auto TypeEntry = std::make_unique<BTFTypeDerived>(DTy, Tag, false);
TypeId = addType(std::move(TypeEntry), DTy);
} else if (Tag != dwarf::DW_TAG_member) {
return;
}
// Visit base type of pointer, typedef, const, volatile, restrict or
// struct/union member.
uint32_t TempTypeId = 0;
if (Tag == dwarf::DW_TAG_member)
visitTypeEntry(DTy->getBaseType(), TempTypeId, true, false);
else
visitTypeEntry(DTy->getBaseType(), TempTypeId, CheckPointer, SeenPointer);
}
void BTFDebug::visitTypeEntry(const DIType *Ty, uint32_t &TypeId,
bool CheckPointer, bool SeenPointer) {
if (!Ty || DIToIdMap.find(Ty) != DIToIdMap.end()) {
TypeId = DIToIdMap[Ty];
// To handle the case like the following:
// struct t;
// typedef struct t _t;
// struct s1 { _t *c; };
// int test1(struct s1 *arg) { ... }
//
// struct t { int a; int b; };
// struct s2 { _t c; }
// int test2(struct s2 *arg) { ... }
//
// During traversing test1() argument, "_t" is recorded
// in DIToIdMap and a forward declaration fixup is created
// for "struct t" to avoid pointee type traversal.
//
// During traversing test2() argument, even if we see "_t" is
// already defined, we should keep moving to eventually
// bring in types for "struct t". Otherwise, the "struct s2"
// definition won't be correct.
if (Ty && (!CheckPointer || !SeenPointer)) {
if (const auto *DTy = dyn_cast<DIDerivedType>(Ty)) {
unsigned Tag = DTy->getTag();
if (Tag == dwarf::DW_TAG_typedef || Tag == dwarf::DW_TAG_const_type ||
Tag == dwarf::DW_TAG_volatile_type ||
Tag == dwarf::DW_TAG_restrict_type) {
uint32_t TmpTypeId;
visitTypeEntry(DTy->getBaseType(), TmpTypeId, CheckPointer,
SeenPointer);
}
}
}
return;
}
if (const auto *BTy = dyn_cast<DIBasicType>(Ty))
visitBasicType(BTy, TypeId);
else if (const auto *STy = dyn_cast<DISubroutineType>(Ty))
visitSubroutineType(STy, false, std::unordered_map<uint32_t, StringRef>(),
TypeId);
else if (const auto *CTy = dyn_cast<DICompositeType>(Ty))
visitCompositeType(CTy, TypeId);
else if (const auto *DTy = dyn_cast<DIDerivedType>(Ty))
visitDerivedType(DTy, TypeId, CheckPointer, SeenPointer);
else
llvm_unreachable("Unknown DIType");
}
void BTFDebug::visitTypeEntry(const DIType *Ty) {
uint32_t TypeId;
visitTypeEntry(Ty, TypeId, false, false);
}
void BTFDebug::visitMapDefType(const DIType *Ty, uint32_t &TypeId) {
if (!Ty || DIToIdMap.find(Ty) != DIToIdMap.end()) {
TypeId = DIToIdMap[Ty];
return;
}
// MapDef type may be a struct type or a non-pointer derived type
const DIType *OrigTy = Ty;
while (auto *DTy = dyn_cast<DIDerivedType>(Ty)) {
auto Tag = DTy->getTag();
if (Tag != dwarf::DW_TAG_typedef && Tag != dwarf::DW_TAG_const_type &&
Tag != dwarf::DW_TAG_volatile_type &&
Tag != dwarf::DW_TAG_restrict_type)
break;
Ty = DTy->getBaseType();
}
const auto *CTy = dyn_cast<DICompositeType>(Ty);
if (!CTy)
return;
auto Tag = CTy->getTag();
if (Tag != dwarf::DW_TAG_structure_type || CTy->isForwardDecl())
return;
// Visit all struct members to ensure pointee type is visited
const DINodeArray Elements = CTy->getElements();
for (const auto *Element : Elements) {
const auto *MemberType = cast<DIDerivedType>(Element);
visitTypeEntry(MemberType->getBaseType());
}
// Visit this type, struct or a const/typedef/volatile/restrict type
visitTypeEntry(OrigTy, TypeId, false, false);
}
/// Read file contents from the actual file or from the source
std::string BTFDebug::populateFileContent(const DISubprogram *SP) {
auto File = SP->getFile();
std::string FileName;
if (!File->getFilename().startswith("/") && File->getDirectory().size())
FileName = File->getDirectory().str() + "/" + File->getFilename().str();
else
FileName = std::string(File->getFilename());
// No need to populate the contends if it has been populated!
if (FileContent.find(FileName) != FileContent.end())
return FileName;
std::vector<std::string> Content;
std::string Line;
Content.push_back(Line); // Line 0 for empty string
std::unique_ptr<MemoryBuffer> Buf;
auto Source = File->getSource();
if (Source)
Buf = MemoryBuffer::getMemBufferCopy(*Source);
else if (ErrorOr<std::unique_ptr<MemoryBuffer>> BufOrErr =
MemoryBuffer::getFile(FileName))
Buf = std::move(*BufOrErr);
if (Buf)
for (line_iterator I(*Buf, false), E; I != E; ++I)
Content.push_back(std::string(*I));
FileContent[FileName] = Content;
return FileName;
}
void BTFDebug::constructLineInfo(const DISubprogram *SP, MCSymbol *Label,
uint32_t Line, uint32_t Column) {
std::string FileName = populateFileContent(SP);
BTFLineInfo LineInfo;
LineInfo.Label = Label;
LineInfo.FileNameOff = addString(FileName);
// If file content is not available, let LineOff = 0.
if (Line < FileContent[FileName].size())
LineInfo.LineOff = addString(FileContent[FileName][Line]);
else
LineInfo.LineOff = 0;
LineInfo.LineNum = Line;
LineInfo.ColumnNum = Column;
LineInfoTable[SecNameOff].push_back(LineInfo);
}
void BTFDebug::emitCommonHeader() {
OS.AddComment("0x" + Twine::utohexstr(BTF::MAGIC));
OS.emitIntValue(BTF::MAGIC, 2);
OS.emitInt8(BTF::VERSION);
OS.emitInt8(0);
}
void BTFDebug::emitBTFSection() {
// Do not emit section if no types and only "" string.
if (!TypeEntries.size() && StringTable.getSize() == 1)
return;
MCContext &Ctx = OS.getContext();
OS.SwitchSection(Ctx.getELFSection(".BTF", ELF::SHT_PROGBITS, 0));
// Emit header.
emitCommonHeader();
OS.emitInt32(BTF::HeaderSize);
uint32_t TypeLen = 0, StrLen;
for (const auto &TypeEntry : TypeEntries)
TypeLen += TypeEntry->getSize();
StrLen = StringTable.getSize();
OS.emitInt32(0);
OS.emitInt32(TypeLen);
OS.emitInt32(TypeLen);
OS.emitInt32(StrLen);
// Emit type table.
for (const auto &TypeEntry : TypeEntries)
TypeEntry->emitType(OS);
// Emit string table.
uint32_t StringOffset = 0;
for (const auto &S : StringTable.getTable()) {
OS.AddComment("string offset=" + std::to_string(StringOffset));
OS.emitBytes(S);
OS.emitBytes(StringRef("\0", 1));
StringOffset += S.size() + 1;
}
}
void BTFDebug::emitBTFExtSection() {
// Do not emit section if empty FuncInfoTable and LineInfoTable
// and FieldRelocTable.
if (!FuncInfoTable.size() && !LineInfoTable.size() &&
!FieldRelocTable.size())
return;
MCContext &Ctx = OS.getContext();
OS.SwitchSection(Ctx.getELFSection(".BTF.ext", ELF::SHT_PROGBITS, 0));
// Emit header.
emitCommonHeader();
OS.emitInt32(BTF::ExtHeaderSize);
// Account for FuncInfo/LineInfo record size as well.
uint32_t FuncLen = 4, LineLen = 4;
// Do not account for optional FieldReloc.
uint32_t FieldRelocLen = 0;
for (const auto &FuncSec : FuncInfoTable) {
FuncLen += BTF::SecFuncInfoSize;
FuncLen += FuncSec.second.size() * BTF::BPFFuncInfoSize;
}
for (const auto &LineSec : LineInfoTable) {
LineLen += BTF::SecLineInfoSize;
LineLen += LineSec.second.size() * BTF::BPFLineInfoSize;
}
for (const auto &FieldRelocSec : FieldRelocTable) {
FieldRelocLen += BTF::SecFieldRelocSize;
FieldRelocLen += FieldRelocSec.second.size() * BTF::BPFFieldRelocSize;
}
if (FieldRelocLen)
FieldRelocLen += 4;
OS.emitInt32(0);
OS.emitInt32(FuncLen);
OS.emitInt32(FuncLen);
OS.emitInt32(LineLen);
OS.emitInt32(FuncLen + LineLen);
OS.emitInt32(FieldRelocLen);
// Emit func_info table.
OS.AddComment("FuncInfo");
OS.emitInt32(BTF::BPFFuncInfoSize);
for (const auto &FuncSec : FuncInfoTable) {
OS.AddComment("FuncInfo section string offset=" +
std::to_string(FuncSec.first));
OS.emitInt32(FuncSec.first);
OS.emitInt32(FuncSec.second.size());
for (const auto &FuncInfo : FuncSec.second) {
Asm->emitLabelReference(FuncInfo.Label, 4);
OS.emitInt32(FuncInfo.TypeId);
}
}
// Emit line_info table.
OS.AddComment("LineInfo");
OS.emitInt32(BTF::BPFLineInfoSize);
for (const auto &LineSec : LineInfoTable) {
OS.AddComment("LineInfo section string offset=" +
std::to_string(LineSec.first));
OS.emitInt32(LineSec.first);
OS.emitInt32(LineSec.second.size());
for (const auto &LineInfo : LineSec.second) {
Asm->emitLabelReference(LineInfo.Label, 4);
OS.emitInt32(LineInfo.FileNameOff);
OS.emitInt32(LineInfo.LineOff);
OS.AddComment("Line " + std::to_string(LineInfo.LineNum) + " Col " +
std::to_string(LineInfo.ColumnNum));
OS.emitInt32(LineInfo.LineNum << 10 | LineInfo.ColumnNum);
}
}
// Emit field reloc table.
if (FieldRelocLen) {
OS.AddComment("FieldReloc");
OS.emitInt32(BTF::BPFFieldRelocSize);
for (const auto &FieldRelocSec : FieldRelocTable) {
OS.AddComment("Field reloc section string offset=" +
std::to_string(FieldRelocSec.first));
OS.emitInt32(FieldRelocSec.first);
OS.emitInt32(FieldRelocSec.second.size());
for (const auto &FieldRelocInfo : FieldRelocSec.second) {
Asm->emitLabelReference(FieldRelocInfo.Label, 4);
OS.emitInt32(FieldRelocInfo.TypeID);
OS.emitInt32(FieldRelocInfo.OffsetNameOff);
OS.emitInt32(FieldRelocInfo.RelocKind);
}
}
}
}
void BTFDebug::beginFunctionImpl(const MachineFunction *MF) {
auto *SP = MF->getFunction().getSubprogram();
auto *Unit = SP->getUnit();
if (Unit->getEmissionKind() == DICompileUnit::NoDebug) {
SkipInstruction = true;
return;
}
SkipInstruction = false;
// Collect MapDef types. Map definition needs to collect
// pointee types. Do it first. Otherwise, for the following
// case:
// struct m { ...};
// struct t {
// struct m *key;
// };
// foo(struct t *arg);
//
// struct mapdef {
// ...
// struct m *key;
// ...
// } __attribute__((section(".maps"))) hash_map;
//
// If subroutine foo is traversed first, a type chain
// "ptr->struct m(fwd)" will be created and later on
// when traversing mapdef, since "ptr->struct m" exists,
// the traversal of "struct m" will be omitted.
if (MapDefNotCollected) {
processGlobals(true);
MapDefNotCollected = false;
}
// Collect all types locally referenced in this function.
// Use RetainedNodes so we can collect all argument names
// even if the argument is not used.
std::unordered_map<uint32_t, StringRef> FuncArgNames;
for (const DINode *DN : SP->getRetainedNodes()) {
if (const auto *DV = dyn_cast<DILocalVariable>(DN)) {
// Collect function arguments for subprogram func type.
uint32_t Arg = DV->getArg();
if (Arg) {
visitTypeEntry(DV->getType());
FuncArgNames[Arg] = DV->getName();
}
}
}
// Construct subprogram func proto type.
uint32_t ProtoTypeId;
visitSubroutineType(SP->getType(), true, FuncArgNames, ProtoTypeId);
// Construct subprogram func type
uint8_t Scope = SP->isLocalToUnit() ? BTF::FUNC_STATIC : BTF::FUNC_GLOBAL;
auto FuncTypeEntry =
std::make_unique<BTFTypeFunc>(SP->getName(), ProtoTypeId, Scope);
uint32_t FuncTypeId = addType(std::move(FuncTypeEntry));
for (const auto &TypeEntry : TypeEntries)
TypeEntry->completeType(*this);
// Construct funcinfo and the first lineinfo for the function.
MCSymbol *FuncLabel = Asm->getFunctionBegin();
BTFFuncInfo FuncInfo;
FuncInfo.Label = FuncLabel;
FuncInfo.TypeId = FuncTypeId;
if (FuncLabel->isInSection()) {
MCSection &Section = FuncLabel->getSection();
const MCSectionELF *SectionELF = dyn_cast<MCSectionELF>(&Section);
assert(SectionELF && "Null section for Function Label");
SecNameOff = addString(SectionELF->getName());
} else {
SecNameOff = addString(".text");
}
FuncInfoTable[SecNameOff].push_back(FuncInfo);
}
void BTFDebug::endFunctionImpl(const MachineFunction *MF) {
SkipInstruction = false;
LineInfoGenerated = false;
SecNameOff = 0;
}
/// On-demand populate types as requested from abstract member
/// accessing or preserve debuginfo type.
unsigned BTFDebug::populateType(const DIType *Ty) {
unsigned Id;
visitTypeEntry(Ty, Id, false, false);
for (const auto &TypeEntry : TypeEntries)
TypeEntry->completeType(*this);
return Id;
}
/// Generate a struct member field relocation.
void BTFDebug::generatePatchImmReloc(const MCSymbol *ORSym, uint32_t RootId,
const GlobalVariable *GVar, bool IsAma) {
BTFFieldReloc FieldReloc;
FieldReloc.Label = ORSym;
FieldReloc.TypeID = RootId;
StringRef AccessPattern = GVar->getName();
size_t FirstDollar = AccessPattern.find_first_of('$');
if (IsAma) {
size_t FirstColon = AccessPattern.find_first_of(':');
size_t SecondColon = AccessPattern.find_first_of(':', FirstColon + 1);
StringRef IndexPattern = AccessPattern.substr(FirstDollar + 1);
StringRef RelocKindStr = AccessPattern.substr(FirstColon + 1,
SecondColon - FirstColon);
StringRef PatchImmStr = AccessPattern.substr(SecondColon + 1,
FirstDollar - SecondColon);
FieldReloc.OffsetNameOff = addString(IndexPattern);
FieldReloc.RelocKind = std::stoull(std::string(RelocKindStr));
PatchImms[GVar] = std::stoul(std::string(PatchImmStr));
} else {
StringRef RelocStr = AccessPattern.substr(FirstDollar + 1);
FieldReloc.OffsetNameOff = addString("0");
FieldReloc.RelocKind = std::stoull(std::string(RelocStr));
PatchImms[GVar] = RootId;
}
FieldRelocTable[SecNameOff].push_back(FieldReloc);
}
void BTFDebug::processReloc(const MachineOperand &MO) {
// check whether this is a candidate or not
if (MO.isGlobal()) {
const GlobalValue *GVal = MO.getGlobal();
auto *GVar = dyn_cast<GlobalVariable>(GVal);
if (!GVar)
return;
if (!GVar->hasAttribute(BPFCoreSharedInfo::AmaAttr) &&
!GVar->hasAttribute(BPFCoreSharedInfo::TypeIdAttr))
return;
MCSymbol *ORSym = OS.getContext().createTempSymbol();
OS.emitLabel(ORSym);
MDNode *MDN = GVar->getMetadata(LLVMContext::MD_preserve_access_index);
uint32_t RootId = populateType(dyn_cast<DIType>(MDN));
generatePatchImmReloc(ORSym, RootId, GVar,
GVar->hasAttribute(BPFCoreSharedInfo::AmaAttr));
}
}
void BTFDebug::beginInstruction(const MachineInstr *MI) {
DebugHandlerBase::beginInstruction(MI);
if (SkipInstruction || MI->isMetaInstruction() ||
MI->getFlag(MachineInstr::FrameSetup))
return;
if (MI->isInlineAsm()) {
// Count the number of register definitions to find the asm string.
unsigned NumDefs = 0;
for (; MI->getOperand(NumDefs).isReg() && MI->getOperand(NumDefs).isDef();
++NumDefs)
;
// Skip this inline asm instruction if the asmstr is empty.
const char *AsmStr = MI->getOperand(NumDefs).getSymbolName();
if (AsmStr[0] == 0)
return;
}
if (MI->getOpcode() == BPF::LD_imm64) {
// If the insn is "r2 = LD_imm64 @<an AmaAttr global>",
// add this insn into the .BTF.ext FieldReloc subsection.
// Relocation looks like:
// . SecName:
// . InstOffset
// . TypeID
// . OffSetNameOff
// . RelocType
// Later, the insn is replaced with "r2 = <offset>"
// where "<offset>" equals to the offset based on current
// type definitions.
//
// If the insn is "r2 = LD_imm64 @<an TypeIdAttr global>",
// The LD_imm64 result will be replaced with a btf type id.
processReloc(MI->getOperand(1));
} else if (MI->getOpcode() == BPF::CORE_MEM ||
MI->getOpcode() == BPF::CORE_ALU32_MEM ||
MI->getOpcode() == BPF::CORE_SHIFT) {
// relocation insn is a load, store or shift insn.
processReloc(MI->getOperand(3));
} else if (MI->getOpcode() == BPF::JAL) {
// check extern function references
const MachineOperand &MO = MI->getOperand(0);
if (MO.isGlobal()) {
processFuncPrototypes(dyn_cast<Function>(MO.getGlobal()));
}
}
// Skip this instruction if no DebugLoc or the DebugLoc
// is the same as the previous instruction.
const DebugLoc &DL = MI->getDebugLoc();
if (!DL || PrevInstLoc == DL) {
// This instruction will be skipped, no LineInfo has
// been generated, construct one based on function signature.
if (LineInfoGenerated == false) {
auto *S = MI->getMF()->getFunction().getSubprogram();
MCSymbol *FuncLabel = Asm->getFunctionBegin();
constructLineInfo(S, FuncLabel, S->getLine(), 0);
LineInfoGenerated = true;
}
return;
}
// Create a temporary label to remember the insn for lineinfo.
MCSymbol *LineSym = OS.getContext().createTempSymbol();
OS.emitLabel(LineSym);
// Construct the lineinfo.
auto SP = DL.get()->getScope()->getSubprogram();
constructLineInfo(SP, LineSym, DL.getLine(), DL.getCol());
LineInfoGenerated = true;
PrevInstLoc = DL;
}
void BTFDebug::processGlobals(bool ProcessingMapDef) {
// Collect all types referenced by globals.
const Module *M = MMI->getModule();
for (const GlobalVariable &Global : M->globals()) {
// Decide the section name.
StringRef SecName;
if (Global.hasSection()) {
SecName = Global.getSection();
} else if (Global.hasInitializer()) {
// data, bss, or readonly sections
if (Global.isConstant())
SecName = ".rodata";
else
SecName = Global.getInitializer()->isZeroValue() ? ".bss" : ".data";
} else {
// extern variables without explicit section,
// put them into ".extern" section.
SecName = ".extern";
}
if (ProcessingMapDef != SecName.startswith(".maps"))
continue;
// Create a .rodata datasec if the global variable is an initialized
// constant with private linkage and if it won't be in .rodata.str<#>
// and .rodata.cst<#> sections.
if (SecName == ".rodata" && Global.hasPrivateLinkage() &&
DataSecEntries.find(std::string(SecName)) == DataSecEntries.end()) {
SectionKind GVKind =
TargetLoweringObjectFile::getKindForGlobal(&Global, Asm->TM);
// skip .rodata.str<#> and .rodata.cst<#> sections
if (!GVKind.isMergeableCString() && !GVKind.isMergeableConst()) {
DataSecEntries[std::string(SecName)] =
std::make_unique<BTFKindDataSec>(Asm, std::string(SecName));
}
}
SmallVector<DIGlobalVariableExpression *, 1> GVs;
Global.getDebugInfo(GVs);
// No type information, mostly internal, skip it.
if (GVs.size() == 0)
continue;
uint32_t GVTypeId = 0;
for (auto *GVE : GVs) {
if (SecName.startswith(".maps"))
visitMapDefType(GVE->getVariable()->getType(), GVTypeId);
else
visitTypeEntry(GVE->getVariable()->getType(), GVTypeId, false, false);
break;
}
// Only support the following globals:
// . static variables
// . non-static weak or non-weak global variables
// . weak or non-weak extern global variables
// Whether DataSec is readonly or not can be found from corresponding ELF
// section flags. Whether a BTF_KIND_VAR is a weak symbol or not
// can be found from the corresponding ELF symbol table.
auto Linkage = Global.getLinkage();
if (Linkage != GlobalValue::InternalLinkage &&
Linkage != GlobalValue::ExternalLinkage &&
Linkage != GlobalValue::WeakAnyLinkage &&
Linkage != GlobalValue::ExternalWeakLinkage)
continue;
uint32_t GVarInfo;
if (Linkage == GlobalValue::InternalLinkage) {
GVarInfo = BTF::VAR_STATIC;
} else if (Global.hasInitializer()) {
GVarInfo = BTF::VAR_GLOBAL_ALLOCATED;
} else {
GVarInfo = BTF::VAR_GLOBAL_EXTERNAL;
}
auto VarEntry =
std::make_unique<BTFKindVar>(Global.getName(), GVTypeId, GVarInfo);
uint32_t VarId = addType(std::move(VarEntry));
assert(!SecName.empty());
// Find or create a DataSec
if (DataSecEntries.find(std::string(SecName)) == DataSecEntries.end()) {
DataSecEntries[std::string(SecName)] =
std::make_unique<BTFKindDataSec>(Asm, std::string(SecName));
}
// Calculate symbol size
const DataLayout &DL = Global.getParent()->getDataLayout();
uint32_t Size = DL.getTypeAllocSize(Global.getType()->getElementType());
DataSecEntries[std::string(SecName)]->addVar(VarId, Asm->getSymbol(&Global),
Size);
}
}
/// Emit proper patchable instructions.
bool BTFDebug::InstLower(const MachineInstr *MI, MCInst &OutMI) {
if (MI->getOpcode() == BPF::LD_imm64) {
const MachineOperand &MO = MI->getOperand(1);
if (MO.isGlobal()) {
const GlobalValue *GVal = MO.getGlobal();
auto *GVar = dyn_cast<GlobalVariable>(GVal);
if (GVar) {
// Emit "mov ri, <imm>"
uint32_t Imm;
if (GVar->hasAttribute(BPFCoreSharedInfo::AmaAttr) ||
GVar->hasAttribute(BPFCoreSharedInfo::TypeIdAttr))
Imm = PatchImms[GVar];
else
return false;
OutMI.setOpcode(BPF::MOV_ri);
OutMI.addOperand(MCOperand::createReg(MI->getOperand(0).getReg()));
OutMI.addOperand(MCOperand::createImm(Imm));
return true;
}
}
} else if (MI->getOpcode() == BPF::CORE_MEM ||
MI->getOpcode() == BPF::CORE_ALU32_MEM ||
MI->getOpcode() == BPF::CORE_SHIFT) {
const MachineOperand &MO = MI->getOperand(3);
if (MO.isGlobal()) {
const GlobalValue *GVal = MO.getGlobal();
auto *GVar = dyn_cast<GlobalVariable>(GVal);
if (GVar && GVar->hasAttribute(BPFCoreSharedInfo::AmaAttr)) {
uint32_t Imm = PatchImms[GVar];
OutMI.setOpcode(MI->getOperand(1).getImm());
if (MI->getOperand(0).isImm())
OutMI.addOperand(MCOperand::createImm(MI->getOperand(0).getImm()));
else
OutMI.addOperand(MCOperand::createReg(MI->getOperand(0).getReg()));
OutMI.addOperand(MCOperand::createReg(MI->getOperand(2).getReg()));
OutMI.addOperand(MCOperand::createImm(Imm));
return true;
}
}
}
return false;
}
void BTFDebug::processFuncPrototypes(const Function *F) {
if (!F)
return;
const DISubprogram *SP = F->getSubprogram();
if (!SP || SP->isDefinition())
return;
// Do not emit again if already emitted.
if (ProtoFunctions.find(F) != ProtoFunctions.end())
return;
ProtoFunctions.insert(F);
uint32_t ProtoTypeId;
const std::unordered_map<uint32_t, StringRef> FuncArgNames;
visitSubroutineType(SP->getType(), false, FuncArgNames, ProtoTypeId);
uint8_t Scope = BTF::FUNC_EXTERN;
auto FuncTypeEntry =
std::make_unique<BTFTypeFunc>(SP->getName(), ProtoTypeId, Scope);
addType(std::move(FuncTypeEntry));
}
void BTFDebug::endModule() {
// Collect MapDef globals if not collected yet.
if (MapDefNotCollected) {
processGlobals(true);
MapDefNotCollected = false;
}
// Collect global types/variables except MapDef globals.
processGlobals(false);
for (auto &DataSec : DataSecEntries)
addType(std::move(DataSec.second));
// Fixups
for (auto &Fixup : FixupDerivedTypes) {
StringRef TypeName = Fixup.first;
bool IsUnion = Fixup.second.first;
// Search through struct types
uint32_t StructTypeId = 0;
for (const auto &StructType : StructTypes) {
if (StructType->getName() == TypeName) {
StructTypeId = StructType->getId();
break;
}
}
if (StructTypeId == 0) {
auto FwdTypeEntry = std::make_unique<BTFTypeFwd>(TypeName, IsUnion);
StructTypeId = addType(std::move(FwdTypeEntry));
}
for (auto &DType : Fixup.second.second) {
DType->setPointeeType(StructTypeId);
}
}
// Complete BTF type cross refereences.
for (const auto &TypeEntry : TypeEntries)
TypeEntry->completeType(*this);
// Emit BTF sections.
emitBTFSection();
emitBTFExtSection();
}
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