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 //===- BTFParser.h ----------------------------------------------*- C++ -*-===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 //
 // BTFParser reads .BTF and .BTF.ext ELF sections generated by LLVM
 // BPF backend and provides introspection for the stored information.
 // Currently the following information is accessible:
 // - string table;
 // - instruction offset to line information mapping;
 // - types table;
 // - CO-RE relocations table.
 //
 // See llvm/DebugInfo/BTF/BTF.h for some details about binary format
 // and links to Linux Kernel documentation.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_DEBUGINFO_BTF_BTFPARSER_H
 #define LLVM_DEBUGINFO_BTF_BTFPARSER_H
 
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/DebugInfo/BTF/BTF.h"
 #include "llvm/Object/ObjectFile.h"
 #include "llvm/Support/DataExtractor.h"
 
 namespace llvm {
 using object::ObjectFile;
 using object::SectionedAddress;
 using object::SectionRef;
 
 class BTFParser {
   using BTFLinesVector = SmallVector<BTF::BPFLineInfo, 0>;
   using BTFRelocVector = SmallVector<BTF::BPFFieldReloc, 0>;
 
   // In BTF strings are stored as a continuous memory region with
   // individual strings separated by 0 bytes. Strings are identified
   // by an offset in such region.
   // The `StringsTable` points to this region in the parsed ObjectFile.
   StringRef StringsTable;
 
   // A copy of types table from the object file but using native byte
   // order. Should not be too big in practice, e.g. for ~250MiB vmlinux
   // image it is ~4MiB.
   OwningArrayRef<uint8_t> TypesBuffer;
 
   // Maps ELF section number to instruction line number information.
   // Each BTFLinesVector is sorted by `InsnOffset` to allow fast lookups.
   DenseMap<uint64_t, BTFLinesVector> SectionLines;
 
   // Maps ELF section number to CO-RE relocation information.
   // Each BTFRelocVector is sorted by `InsnOffset` to allow fast lookups.
   DenseMap<uint64_t, BTFRelocVector> SectionRelocs;
 
   // Vector of pointers to all known types, index in this vector
   // equals to logical type BTF id.
   // Pointers point to memory owned by `TypesBuffer`
   // (except pointer at index 0, which is statically allocated).
   std::vector<const BTF::CommonType *> Types;
 
   struct ParseContext;
   Error parseBTF(ParseContext &Ctx, SectionRef BTF);
   Error parseBTFExt(ParseContext &Ctx, SectionRef BTFExt);
   Error parseLineInfo(ParseContext &Ctx, DataExtractor &Extractor,
                       uint64_t LineInfoStart, uint64_t LineInfoEnd);
   Error parseRelocInfo(ParseContext &Ctx, DataExtractor &Extractor,
                        uint64_t RelocInfoStart, uint64_t RelocInfoEnd);
   Error parseTypesInfo(ParseContext &Ctx, uint64_t TypesInfoStart,
                        StringRef RawData);
 
 public:
   // Looks-up a string in the .BTF section's string table.
   // Offset is relative to string table start.
   StringRef findString(uint32_t Offset) const;
 
   // Search for line information for a specific address,
   // address match is exact (contrary to DWARFContext).
   // Return nullptr if no information found.
   // If information is present, return a pointer to object
   // owned by this class.
   const BTF::BPFLineInfo *findLineInfo(SectionedAddress Address) const;
 
   // Search for CO-RE relocation information for a specific address.
   // Return nullptr if no information found.
   // If information is present, return a pointer to object
   // owned by this class.
   const BTF::BPFFieldReloc *findFieldReloc(SectionedAddress Address) const;
 
   // Return a human readable representation of the CO-RE relocation
   // record, this is for display purpose only.
   // See implementation for details.
   void symbolize(const BTF::BPFFieldReloc *Reloc,
                  SmallVectorImpl<char> &Result) const;
 
   // Lookup BTF type definition with a specific index.
   // Return nullptr if no information found.
   // If information is present, return a pointer to object
   // owned by this class.
   const BTF::CommonType *findType(uint32_t Id) const;
 
   // Return total number of known BTF types.
   size_t typesCount() const { return Types.size(); }
 
   // Allow to selectively load BTF information.
   struct ParseOptions {
     bool LoadLines = false;
     bool LoadTypes = false;
     bool LoadRelocs = false;
   };
 
   // Fills instance of BTFParser with information stored in .BTF and
   // .BTF.ext sections of the `Obj`. If this instance was already
   // filled, old data is discarded.
   //
   // If information cannot be parsed:
   // - return an error describing the failure;
   // - state of the BTFParser might be incomplete but is not invalid,
   //   queries might be run against it, but some (or all) information
   //   might be unavailable;
   Error parse(const ObjectFile &Obj, const ParseOptions &Opts);
   Error parse(const ObjectFile &Obj) { return parse(Obj, {true, true, true}); }
 
   // Return true if `Obj` has .BTF and .BTF.ext sections.
   static bool hasBTFSections(const ObjectFile &Obj);
 };
 
 } // namespace llvm
 
 #endif // LLVM_DEBUGINFO_BTF_BTFPARSER_H

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